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Functional materials


Chromogenic materials and devices

Chromogenic materials and devices exhibit tunable optical properties because of influence of external means such as illumination, temperature, pressure, electric or magnetic fields, x-rays, ion-beam radiation, gases or potential. They have strong potential in many technologically important applications: in building and automobile industry by controlling the light and heat transfer through windows, in optoelectronic and medical industry as well as environmental technology as emitting and sensing devices, in stealth program, designed to produce vehicle that are immune to infrared detection and to make them nearly invisible to enemy (the ability to decouple temperature and thermal emission opens a gateway for controlling the visibility of objects to infrared cameras), in aerospace engineering by changeable emissivity of surfaces upon heating, as the spacecraft thermal control, as visors and windows that can control glare for pilots and passengers, etc. Current theoretical and experimental studies aim to further increase the impact that the chromogenic materials and devices can play in technological advances. The Symposium is to bring academic scientists, engineers, and industry to exchange their results about latest developments on the topic.


In recent years, new materials, devices, and new applications came out in the field of chromogenic materials and devices. Some of them are the new x-chromatic devices based on the emerging class of mixed anion materials, polymer-based multicolor x-chromatic devices, new designs of electrochromic devices with enhanced dielectric tunability and self-healing properties, new applications of inorganic photochromic coatings in contact lenses and car industry, photochromic polymers in textile industry, multifunctional photothermochromic materials,  latest achievements on materials engineering for reducing the temperature for tuning reflectivity of thermochromic coatings, innovative smart selective coatings to avoid overheating in highly efficient thermal solar collectors, etc. Furthermore, the recent years have seen the development and improvement in synthesis and characterization techniques such as printing and roll-to-roll deposition of x-chromatic device. Current theoretical and experimental studies aim to further increase the impact that chromogenic materials and systems can play in technological advances. This Symposium will provide an overview of the state of the art and most recent scientific and technical progress as well as the market situation, identification of key areas, challenges, approaches, and technologies in this field along with the life cycle assessment, eco-toxicological assessment and risk assessment. It is multidisciplinary and international. Target groups are young scientists, early stage and experienced researchers from academic Institutions, SME’s and industries. To motivate participation of young researchers and beginners into the Symposium, graduate student awards (GSA) will be arranged. One day tutorial entitled “mixed anion materials, applications in x-chromism, and methods of study” will be arranged. The lectures of the tutorial will be delivered by experienced researchers working in this field. Upon approval, the Symposium organizers will search for sponsors that would cover some of the extra expenses that will be spent to offer partial financial support to contributors from emerging countries. About 40% of the invited speakers are from SME’s and companies that have activity related to chromogenics. So, the Symposium will be excellent platform that reflects the latest news about market needs that can be solved by chromogenics.

Hot topics to be covered by the symposium:

  • Chromogenic (electrochromic, thermochromic, photochromic, gasochromic, magnetochromic, piezochromic) devices;
  • Building-integrated chromogenic devices;
  • Degradation of chromogenic materials and devices;
  • Window-integrated solar powered chromogenic devices;
  • Organic, inorganic and hybrid chromogenic materials;
  • Chromogenic nanomaterial-organic/inorganic composites;
  • Mixed anion materials for chromogenic device applications;
  • Defects and impurities;
  • Theoretical and experimental methods of research;
  • Applications in buildings, ophthalmology;
  • Life-cycle assessment;
  • Thermal regulation;
  • Infrared stealth.



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08:45 Welcome and Introduction to the Symposium - B. Dam, F. Capon, S. Karazhanov, A. Rougier    
Session I : Fabien Capon – Albert Schenning
Authors : Albert Schenning
Affiliations : Eindhoven University of Technology

Resume : Cholesteric liquid crystal polymers display selective reflection properties arising from their helical ordering. The temperature response of these polymers, comprising dynamic reflection color changes upon variation of temperature, can be exploited in energy-saving smart windows. In my lecture, the design, fabrication, and application of temperature responsive infrared reflective polymer coatings will be discussed.

Authors : Acher, L. (1), Ji, H*(1)., Garino, N. (1), Massuyeau, F.(2), Jobic, S.(2), Pontille, L. (1), Cauwet, F. (1), Ferro, G. (1), & Carole, D. (1).
Affiliations : (1) Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France (2) Institut des Matériaux Jean Rouxel, IMN, Université de Nantes, CNRS, F-44000 Nantes, France * lead presenter

Resume : Thermochromic materials are used in a wide range of applications such as temperature memory sensors (cold chain break sensor, threshold temperature sensor for aeronautic application?), temperature sensors for safety (kitchen tools?), smart materials for specified application (smart windows or concrete for building energy efficiency?) or in day-to-day life as smart pigment (textile, ink, packaging?). NiTiO3 is a yellow pigment which adopts a crystalline structure (ilmenite) very close to corundum and thus to hematite. Ilmenite structure is based on a hexagonal close-packed anion lattice with cations occupying two-thirds of the available octahedral interstices (space group R ). Nickel titanate is actively studied for its photocatalytic and magnetic applications but not for thermochromic ones. As chromium-doped corundum and hematite present thermochromic behaviour, the compound was studied to detect any potential ability. The powders were synthesized via a modified Pechini method followed by calcination step (700 °C). For the first time, thermochromic properties have been evidenced on this compound in the temperature range (Room Temperature (RT) ? 400 °C), passing from dark yellow colour at RT to darker brown at 400 °C. The optical properties of the powders have been evaluated using visible spectrometry vs temperature and ?E colour difference measurements. L* and b* parameters both decrease whereas a* increases with temperature. The colour change, i.e. the thermochromism, is continuous and totally reversible as L*a*b* parameters come back to their original values after returning to RT. The cycling has been also checked. Since metal doping of this compound is known to change its colour, we also investigate the effect of doping on the final colour and thermochromism. In order to better explain the thermochromism mechanisms, a deep study of the material was made using High-Temperature X-Ray Diffraction combined with Rietveld refinements, Raman spectroscopy.

Authors : Hupperetz, J.F.B.(1)(2), Yeung, C.P.K.(1)(2), Habets, R.(1)(2), Leufkens, L.(1)(2), van Zandvoort, R.(1)(2), Wolters, D.(1)(2), Meulendijks, N.(1)(2), Mann, D.(1)(2), Buskens, P(1)(2)(3).
Affiliations : (1) The Netherlands Organisation for Applied Scientific Research (TNO), High Tech Campus 25, 5656AE Eindhoven, The Netherlands. (2) Brightlands Materials Center, Urmonderbaan 22, 6167RD Geleen, The Netherlands. (3) Hasselt University (UHasselt), Institute for Materials Research (IMO), DESINe group, Martelarenlaan 42, 3500 Hasselt, Belgium.

Resume : The building sector consumes approximately one third of the total energy worldwide. A large part of this energy is used for heating and cooling of buildings, which can be drastically reduced through application of energy-efficient windows. Novel smart window technologies can provide optimal use of solar heat in regions with changing requirements from summer to winter. Here, we studied vanadium dioxide (VO2), which is a promising optical material for this purpose because of its thermochromic property. Based on its structural phase transition from the semiconductive monoclinic to the conductive rutile structure at a defined switching temperature of 68°C, it switches from a solar infrared transmissive to blocking state. This switch is reversible, the switching temperature can be lowered via doping, and VO2 comprising materials are transparent in the visible, which makes them interesting for application in thermochromic windows that regulate solar heat gain. Very recently, we have reported the preparation and characterization of thermochromic coatings consisting of VO2 and SiO2, the switching kinetics of thermochromic powders, and the impact of thermochromic windows on energy savings in intermediate climates. Here, we report the development of thermochromic coatings and laminates comprising W-doped VO2 nanoparticles as functional pigments. We obtained these pigments via wet bead milling of a W-doped VO2 powder obtained by high-temperature conversion of organometallic precursors in a tube furnace. By DSC and XRD analyses, we demonstrated that high purity W-doped VO2 powders were formed, which were successfully milled to functional thermochromic nanopigments with a switching temperature of 22°C. We applied the nanopigments in both polyvinyl butyral (PVB) polymer films and in silica sol-gel coatings with tunable optical properties for smart window applications. For laminated glass using VO2-pigmented PVB films, a visible transmission of more than 60% with a solar modulation of 8% was reached. Similar optical properties were reached for VO2-pigmented silica coatings with a layer thickness of 300 nm.

Authors : A.C. García-Wong, D. Pilloud, S. Bruyère, F. Capon, J.F. Pierson
Affiliations : Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, Campus Artem, 2 allée André Guinier, 54011 Nancy, France.

Resume : VO2 is a broadly studied thermochromic material, which undergoes a metal-insulator transition approx. at 68°C, accompanied by a crystallographic transition from a low-temperature monoclinic phase to a high-temperature tetragonal rutile structure. Optical and electrical properties change drastically with the phase transition and offer a path to various applications, such as thermal solar collectors, ultrafast electronic devices, smart windows... Nevertheless, the elaboration of pure VO2 films on large surfaces remains a challenge due to the difficult task of avoiding other phases belonging to the vanadium-oxygen binary system [1]. In previous studies, we have demonstrated that the oxidation of VN thin films is a new method to form high-quality thermochromic VO2 [2,3]. The present work aims to achieve thermochromic VO2 from the controlled oxidation of another new precursor: sputter-deposited V2N films. Thermochromic VO2 films have been obtained by air oxidation of V2N samples performed at two temperatures (450 and 550°C). X-ray diffraction and Raman spectrometry of the V2N oxidized films evidence that VO2 and V2O5 are the only phases obtained throughout the oxidation process. VO2 is the first oxide formed coexisting with V2N for a long time at 450°C or swiftly vanishing at 550°C. EELS results show that the oxidation of V2N to VO2 occurs in two stages. First, the V2N turns into VN before the oxidation to VO2. Further oxidation leads to the formation of V2O5, diminishing the thermochromic performance of the films. As the thickness of the initial V2N layer increases from about 100 nm to 445 nm, the optical modulation properties of the obtained VO2 films change from a negative value of the emissivity switch to a positive value. These results may pave the way for future research on the oxidation of V2N as a new precursor to form high-quality thermochromic VO2. [1] Yang et al., Annu. Rev. Mater. Res. 41 (2011) 337?367. [2] García-Wong et al., Sol. Energy Mater. Sol. Cells. 210 (2020) 110474. [3] García-Wong et al., J. Materiomics. 7 (2021) 657?664.

Authors : A. Jolivet a, J. Cardin a, C. Frilay a, O. Debieu b, P. Marie a, S. Duprey a, F. Lemarié a, X. Portier a, B. Horcholles a, P. Bazin c, J. More-Chevalier d, P. Fitl d, S. Cicho? d. J. Lan?ok d, Wojciech Jadwisienczak e, David Ingram f, C. Labbé a
Affiliations : a: CIMAP Normandie Université, ENSICAEN, UNICAEN, CEA, CNRS, 6 Bd Maréchal Juin, 14050 Caen Cedex 4, France; b: CIRIMAT, 4 allée Emile Monso, BP-44362, 31030 Toulouse Cedex 4, France; c: LCS Normandie Université, ENSICAEN, 6 Bd Maréchal Juin, 14050 Caen, France; d: Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 18221 Praha 8, Czech Republic; e: School of Electrical Engineering and Computer Science, Ohio University, Athens, Ohio 45701, USA; f: Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA

Resume : VO2 is a well-known reversible material for its Insulator-to-Metal Transition (IMT) that takes place around 70°C. The closeness between the room temperature and the IMT temperature makes VO2 a suitable candidate for resistive switching systems and thermochromic materials1. The growth by Atomic Layer Deposition (ALD) allows running deposition at temperatures lower than 250°C, enabling deposition on all kinds of substrates, with a low thermal budget. Vanadium oxide films were deposited at 240°C on silicon (100) and glass substrates from water as an oxidizing agent and vanadium tri-isopropoxide (VTIP) as vanadium precursor. Annealing was held at a temperature ranging from 400°C to 550°C by 50°C steps, under forming gas (95% Ar, 5% H2) for 60 minutes. A structural analysis was performed by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM), showing that as-deposited films are amorphous, whereas crystallization in VO2 and V2O5 phase happens around 500°C. Crystallized films are polycrystalline with crystallites reaching 0.3 µm. For a better understanding, XPS and RBS studies will also be presented. Optical and electrical analyzes were also conducted by Raman spectroscopy, Fourier Transformed IR Spectroscopy (FTIR), ellipsometric spectroscopy, and electrical resistivity measurements. According to these spectroscopic techniques, films annealed at 500°C present a repeatable IMT around 70°C. For films on silicon substrate, FTIR spectra show a specially interesting result with the increase of the optical absorbance from 0.1 OD at room temperature up to 0.9 OD above IMT temperature on a wavenumber range extending from 4000 to 1000 cm-1, alongside the disappearance of the low-temperature VO2 peaks in FTIR and Raman spectroscopy. The IMT effect is also observable in the UV-visible range on the glass substrate. For electrical measurements by 4-probe resistivity, the resistivity was found to decrease down to 10-1 ?.cm upon IMT temperature. On the whole, vanadium oxide films were characterized between RT and 100°C and present encouraging properties adjustable with temperature, especially in the IR range, and paves the way for future applications in thermochromic materials. 1. Prasadam, V. P. et al. Atomic layer deposition of vanadium oxides: process and application review. Mater. Today Chem. 12, 396?423 (2019).

10:30 Discussion    
Session II : Aline Rougier - Anthony Maho
Authors : Zhigang Zhao
Affiliations : Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China

Resume : Tungsten oxide (WO3) is the earliest discovered, and most widely used inorganic electrochromic material, which can change its optical properties (transmittance, reflectance, or absorption) when induced by an electrical current or voltage, resulting in variable colors. Owing to its high stability, strong weatherability, good adhesion to glass substrates and ease for large-scale production, the WO3 material has a high commercial prospect. However, in its pristine form, WO3 only displays a one-fold color modulation from transparent to blue, making it very difficult to achieve the utmost goal of full-color tunability for future electrochromic technology. Here, we introduced a Fabry-Perot cavity structure, tuning the thickness, refractive index, repetition period of the dielectric material in the cavities and photonic bandgap, realizing muti-color inorganic electrochromic devices. Such a simply structured device can significantly change to other more brilliant colours by changing the optical indices (n, k) of the tungsten oxide layer through ion insertion under applied potentials. Meanwhile, we emphasized the integration of multicolor electrochromic devices with other advanced energy, environment and electronic technologies to obtain new concept and multi-functional devices of new intelligent energy storage systems, high color purity devices and ?Janus? devices.

Authors : Gwendoline Petroffe,(a) Vincent Roumegoux,(a) Jean-Paul Dudon,(b) Sophie Cantin,(a) Frédéric Vidal,(a) Pierre-Henri Aubert,(a)
Affiliations : (a) LPPI, CY Université, 5 mail Gay-Lussac, 95031 Cergy-Pontoise Cedex, France. (b) Thales Alenia Space (TAS), 100 Boulevard du Midi, 06150 Cannes, France

Resume : In space, the thermal equilibrium of a satellite versus its environment is governed by radiative exchanges. In order to save on-board weight and electrical power, it is strongly interesting to develop new IR-switchable coatings that are able to operate variable infrared emissivity. Indeed such technology can hence offer a high infrared emissivity in ?hot cases? when it is needed to reject heat, and a low emissivity during ?cold cases? when it is suitable to keep the heat within the satellite orbiting around the Earth. Indeed the installed heating power sized on the coldest thermal case can be drastically reduced.[1] In this context and to mimic the satellite temperature conditions, a small radiator has been built: it consists of an assembly of a matrix made of 4x4 electroemissive tiles on an aluminum plate preliminarily equipped with thermistors[2]. A frame cover ensures electrical contact with the 16 tiles; the latter consists in a PEO/NBR semi-interpenetrating polymer network with two PEDOT layers on each side.[3] Hence, adding an electrolyte, the tiles can be operated as a two-electrodes system in which one PEDOT layer exhibits IR-optical switches. The radiator total active surface is 82cm². Once embedded with Kapton®, the radiator is placed in a vacuum chamber and tested under thermal conditions close to the space environment (-25°C up to 80°C) . A thermal sequence has been setup to follow the behavior of the radiator in both ?hot? and ?cold? cases (without taking into account the solar flux) and, at the same time, compared to optical solar reflectors (OSR) taken as a reference. When switched between high and low emissivities according to the thermal load, the radiator was quite more effective than the OSR in preserving the heat inside the satellite during cold environments while in a "hot" environment, the thermal rejection was close to that of the OSR proving the interest of this technology in the thermal regulation of satellites. To this efficiency in the thermal regulation is associated a significant saving in on-board installed electric power dedicated to the heating in cold phases of the mission and thus a reduced mass of the satellite (smaller solar panels and/or batteries). Moreover this energy saving allows a more efficient use of electrical propulsion during Electrical Orbit Raising (EOR) phase and should allow then to reduce drastically the duration of this non-operational phase. In a second part, we will discuss some important aspects especially the reduction of solar absorption and the possibility to prepare flexible tiles to reduce again the on-board weight of the radiator. References [1] F. Vidal, G. Petroffe, L. Beouch, S. Cantin, C. Chevrot, P.-H. Aubert, J.-P. Dudon, Active Thermal Control of Satellites with Electroactive Materials. In: Rasmussen L. (Eds) Smart Materials. Springer, Cham., 2022, pp. 221?254. [2] G. Petroffe, L. Beouch, S. Cantin, C. Chevrot, P.-H. Aubert, J.-P. Dudon, F. Vidal, Sol. Energy Mater. Sol. Cells 2019, 200, 110035. [3] L.J. Goujon, P.-H. Aubert, L. Sauques, F. Vidal, D. Teyssié, C. Chevrot, Sol. Energy Mater. Sol. Cells 2014, 127, 33?42.

Authors : Wei Church Poh, Xuefei Gong, Alice Lee-Sie Eh, Pooi See Lee
Affiliations : School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798

Resume : Electrolytes play an indispensable role in electrochromic devices as it facilitates redox switching process by providing essential ions and balancing residual charges. However, many insurmountable problems exist with typical electrolytes which generally made up of salts in aqueous or organic medium. Aqueous electrolytes, though having good ionic conductivities and relatively safe, are widely limited by their narrow operating temperature and potential. While organic electrolytes can offer better thermal and electrochemical stabilities, their flammability nature is a serious drawback that could restrict widespread applications. Ionic liquids (ILs), which are basically room-temperature liquid salts, are promising and safer alternatives to conventional electrolytes, owing to their outstanding stability and safety features. Nevertheless, high-fluidity nature of ILs could induce a serious risk of leakage and complicates device fabrication, eventually leading to device failure. In this regard, a rationally designed vinyl-functionalized IL monomer has been prepared with the aim of realizing free-standing poly(ionic liquids) (PILs) film for electrochromic applications. The electrolyte ink formulation exhibited a fast-curing process ( < 30 s) under ambient condition, rendering a film with high transparency (> 90 %), excellent ionic conductivity (ca. 4 mS/cm), and good thermal characteristics (>300 ?C). Taking the advantage of in-situ curing process, printing of the ink has also been realized, providing a new strategy for high throughput coating of solid electrolyte. For the electrode materials, a coordination polymer (CP) has been prepared via a highly reproducible electropolymerization process. The growth of this CP on the electrode can be facilely manipulated by electrochemical parameters, resulting in different surface morphology and controllable thickness. Detailed analysis is also established, showing that the CP film growth has taken place in an anisotropic one-dimensional modality. By integrating this CP-modified electrode with the PIL, electrochromic devices have been demonstrated with high optical contrast, fast response time, and good cyclic endurance

Authors : Raquel Utrera-Melero, Florian Massuyeau, Jean-Yves Mevellec, Camille Latouche, and S. Perruchas
Affiliations : Université de Nantes, CNRS, Institut des Matériaux de Nantes Jean Rouxel, IMN, F-44000 Nantes, France.

Resume : Luminescent mechanochromic materials displaying switchable luminescence properties in response to external mechanical stimuli[1] are attracting wide interest for potential applications in strain detection, optical recording and storage, and anti-counterfeiting.[2,3] Regarding security issues, mechanically induced damages need to be detected at the early stage of stress formation[4] and luminescent mechanochromic materials enable the straightforward visible detection of strain with emission changes easily detectable by naked eyes or by simple non-invasive spectroscopic means.[5] Efficient mechanochromic luminescent materials should exhibit high-contrast luminescent change in emission color or intensity for an easy detection and this effect should be preferentially reversible. For practical applications of mechanical sensing, the design of thin films is suitable compared with powdered luminescent mechanochromic compound with no mechanical strength. In parallel, the in-depth understanding of the underlying mechanochromism mechanism is naturally of utmost importance for guiding the development of such stimuli-responsive devices. In this context, we report our investigations regarding the study of luminescent mechanochromic copper iodide complexes and their development as active component for the synthesis of mechanically responsive materials.[6] The luminescent mechanochromic properties of these compounds formulated [Cu4I4L4] (L = organic ligand) are characterized by a contrasted emission change upon mechanical solicitations. Moreover, these compounds exhibit luminescence thermochromism with temperature-dependent luminescence properties.[7] Structural characterizations and spectroscopic analyses supported by DFT (Density Functional Theory) calculations permit to get insights into the mechanochromism mechanism. The synthesis of mechanically-responsive films is also presented. [1] Z. Chi, X. Zhang, B. Xu, X. Zhou, C. Ma, Y. Zhang, S. Liu and J. Xu, Chem. Soc. Rev., 2012, 41, 3878?3896. [2] H. Yu, X. Song, N. Xie, J. Wang, C. Li and Y. Wang, Adv. Funct. Mater., 2021, 31, 2007511. [3] C. Wang, D. Wang, V. Kozhevnikov, X. Dai, G. Turnbull, X. Chen, J. Kong, B. Z. Tang, Y. Li and B. B. Xu, Nat. Commun., 2020, 11, 1448. [4] M. E. McFadden and M. J. Robb, J. Am. Chem. Soc., 2019, 141, 11388?11392. [5] S. Kato, S. Furukawa, D. Aoki, R. Goseki, K. Oikawa, K. Tsuchiya, N. Shimada, A. Maruyama, K. Numata and H. Otsuka, Nat. Commun., 2021, 12, 126. [6] R. Utrera-Melero, B. Huitorel, M. Cordier, F. Massuyeau, J.-Y. Mevellec, N. Stephant, P. Deniard, C. Latouche, C. Martineau-Corcos and S. Perruchas, J. Mater. Chem. C, 2021, 9, 7991?8001. [7] S. Perruchas, Dalton Transactions, 2021, 50, 12031?12044.

Authors : Jiseon Kim*(1), Dongwon Shin(1), Sungjun Choi(1) and Caroline Sunyong Lee(1)
Affiliations : (1) Department of materials science and chemical engineering, Hanyang University, South Korea

Resume : In this research, an inorganic electrochromic device was fabricated to achieve quadruple modes using unique electrolyte chemistry inducing localized surface plasmon resonance(LSPR): 1) transparent, 2) visible light block, 3) near-infrared block and 4) Vis-NIR block. This ECD can control selectively visible light and near-infrared lights to reduce the consumption of heating and cooling energy as well as protect the privacy of the building. Tungsten oxide(WO3) thin films, which are conventionally used as inorganic electrochromic materials, and antimony Tin-doped Oxide(ATO) thin films, which are ion storage materials for charge balance within the devices, were fabricated by nanoparticle deposition system(NPDS), one of the dry deposition methods. ATL electrolyte which stands for mixing silver nitrate(AgNO3), tetrabutylammonium bromide(TBABr), and lithium perchlorate(LiClO4), has been developed in this study. The ECD was successfully produced by injecting ATL electrolytes including lithium and silver ions between WO3 and ATO thin films. Despite the simple structure, controlling the ion movements as well as the surface roughness of thin films overcomes the limitation of the single coloration of WO3 thin films. Indeed, NPDS can fabricate a much rougher surface than other methods such as sputtering. NPDS has supersonically sprayed ceramic or metal powders to the substrate through the pressure difference using a vacuum pump and air compressor. NPDS has the advantage of being cheap due to the low-temperature and low-vacuum process. Moreover, NPDS is an eco-friendly method since it does not require any toxic binder by directly spraying powders. In the case of WO3, it can only change from transparent to a blue color when lithium ions are intercalated to the atomic structure of WO3. At the blue state, WO3 thin films selectively block near-infrared wavelength. ?T which means the difference in light transmittance was measured to be 57 % at 900 nm. To achieve multiple modes, silver ions were controlled by the applied voltage. The optical properties of the ECD depend on the roughness of the surface which silver ions could deposit. When silver ions were deposited on the rough WO3 thin films, the scattering of incident light was maximized within the ECD. As a result, the ECD can block visible light wavelength and 0 % transmittance at all wavelength ranges was achieved due to the synergistic effect of WO¬¬3 coloration due to intercalation of lithium ions. Finally, the LSPR effect was used to selectively block visible light. LSPR is the phenomenon in which metal nanoparticles absorb a specific wavelength through an amplified electric field within the particles. Two-step voltages were applied to rough ATO thin films and then spherical silver nanoparticles were formed on ATO thin film and observed by SEM. Moreover, ?T was measured to be 51 % at 600 nm. In conclusion, the inorganic ECD successfully demonstrated four states using the rough surface of thin films as well as unique ATL electrolytes inducing the LSPR effect.

12:15 Discussion    
12:30 Lunch break    
Session III : Bernard Dam – Daniel Primetzhofer
Authors : D. Primetzhofer
Affiliations : Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden

Resume : A decade ago, photochromic properties were first reported for yttrium-hydride thin films oxidized by air-exposure [1]. Since then, the material systems have been subject to thorough investigation by several research groups, in order to explain the physical origin of the effect, understand the details of the material?s nature as well as to tailor the material?s properties towards application. The group at Uppsala University has initially contributed to the field by comprehensive investigations of the chemical composition of ex-situ deposited thin films using in particular ion beam analysis. These studies included a correlation of the optical performance of the thin films with chemical composition, and helped to establish a phase diagram [2]. Specifically, we observe photochromism for an Y/O ratio of 0.5 to 1.5, with the largest photochromic effect close to 0.5 and monotonically decaying to 1.5. Later, these efforts were broadened to include a wider number of techniques for a comprehensive characterization of the systems, indicating a dual-phase nature of the investigated photochromic systems [3]. In parallel, we started to perform in-situ characterization correlating optical properties with the materials chemistry [4]. Subsequently, full in-situ synthesis and characterization of the systems was conducted, revealing details of the oxygen uptake and illustrating the complete synthesis pathway [5]. Very recently, the interaction of the material system with the environment and its necessity for the photochromic effect were investigated in detail [6][7]. These results showed a pronounced interaction of the system with different ambients but also proved the photochromic effect to be not dependent on material exchange with the environment. Additionally, we have recently started experiments using isotopic labelling to study diffusion in the material systems, revealing that long-distance migration of hydrogen does not play a role in the photochromic effect and that the oxidation of the films progresses along the grain boundaries of the columnar structure [8][9]. Finally, we currently perform complementary characterization of other properties such as photoresistivity during illumination and bleaching cycles. [1] T. Mongstad et al., Sol. Ener. Mat. Sol. Cells 95 (2011) 3596 [2] D. Moldarev et al., Phys. Rev. Mat. 2 (2019) 115203 [3] M. Hans et al., Adv. Opt. Mat. (2020) 2000822 [4] M.V. Moro et al., Sol. Ener. Mat. Sol. Cells 201 (2019) 110119 [5] K. Kantre et al., Scr. Mat. 186 (2020) 352 [6] D. Moldarev et al., J. Appl. Phys. 129 (2021) 153101 [7] M.V. Moro et al., Phys. Stat. Sol. RLL (2021) 2000608 [8] M.V. Moro et al., Phys. Stat. Sol. RLL (2021) 2100508 [9] D. Moldarev et al., Eur. J. Phys. Conf. Ser. (accepted)

Authors : Bernard Dam1, Giorgio Colombi1, Diana Chaykina1, Zying Wu1, Gilles A. De Wijs2, Shrestha Banerjee2, Arno P. M. Kentgens2, Stephan W. H. Eijt1
Affiliations : 1) Faculty of Applied Science, TU Delft, Delft, The Netherlands 2) Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands

Resume : The oxyhydride thin film research is a spin-off from the intensive research on the metal-to-insulator transition in yttrium and related rare earth metal hydrides. This transition can be induced by 1)hydrogenation from the dihydride to the trihydride phase [1], by 2)a reduction in free carrier density [2], and by 3)applying GPa pressure on a trihydride film [3]. Photochromism was first observed under 5GPa pressure and co-existing fcc dihydride and hcp trihydide phases[4]. No photochromism is observed in the transparent trihydride state. Only when adding a substantial amount of oxygen to the lattice do the transparent semiconducting films become photochromic. In most cases, these photochromic films are derived from reactively sputtered dihydride films. The metallic films oxidize on exposure to air, provided that they have a sufficient porosity. The oxidation is self-limiting and results in semiconducting films with a bandgap of about 2.6 to 3.5eV.[] The mechanism of photochromism in rare-earth oxyhydrides is still unclear. In my talk I will show recent characterization experiments using EXAFS, NMR, muSR and positron annihilation spectroscopy. While no final conclusion regarding the mechanism can yet be drawn, these experiments show that the point defect structure is important for the effect to occur. Moreover, indications for a reversible segregation into a small fraction of a metallic state is observed. Acknowledgements: This work was partially supported by the Mat4Sus Research Program with Project Number680.M4SF.034 and by the Open Technology research program with Project Number 13282; both financed by The Netherlands Organisation for Scientific Research (NWO). [1] Huiberts, J. N. et al. Yttrium and lanthanum hydride films with switchable optical properties. Nature 380, 231 (1996). [2]Hoekstra, A.F.Th. Light-induced metal-to-insulator transition in a switchable mirror, Phys. Rev. Lett. 86 (2001) 5349 [3] Palasyuk T., Tkacz M., Pressure-induced structural phase transition in rare-earth trihydrides. Part III. Systematics, Solid State Communications 141, (2007) Pages 354-358 [4] Ohmura,A. et al., Photochromism in yttrium hydride Appl. Phys. Lett. 91 (2007) p151904 [5] Mongstad, T. et al., A new thin film photochromic material: Oxygen-containing yttrium hydride, Solar Energy Materials & Solar Cells 95 (2011) 3596?3599

Authors : Patricia Bolle (a), Oleh Stetsiuk (a,b), Clotilde Menet (a), Marin Puget (a), Hélène Serier-Brault (a), Marie Cordier (b), Shohei Katao (c), Véronique Guerchais (b), Florent Boucher (a), Tsuyoshi Kawai (c), Julien Boixel (b), Rémi Dessapt (a)
Affiliations : (a) Université de Nantes, CNRS, Institut des Matériaux Jean Rouxel, IMN, F-44000 Nantes, France. ; (b) Univ Rennes, CNRS, ISCR ? UMR6226, F-35000, Rennes, France. ; (c) Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.

Resume : The reversibility and fatigability of the light triggered commutation of photochromic materials are crucial specifications for concrete applications. The family of dithienylethenes (DTE) is known for its excellent photochromic behavior in solution [1], but has shown limitation in the solid state in terms of complete, fast and reversible photoswitching. In particular, some of DTE crystals demonstrate breaking with high photoconversion yield, which makes structural analysis complicated. Polyoxometalates (POMs) are metal-oxide clusters that can efficiently tune or exalt the optical properties of photoactive molecules in the solid state [2-4]. Very recently, we have elaborated the first supramolecular assembly of a normal DTE cation with an octamolybdate unit [5]. This coupling modifies the photoresponse of the organic switch via both steric and electronic effects, and gives rise to an increased cycloreversion rate, resulting in a fast and complete re-opening process. The hybrid material also exhibits high light-driven ?recording?erasing? potentialities. The crystal structure after UV-light irradiation contains a mixture of open- and closed-ring DTE isomers with a conversion rate of about 28% which represents one of the highest conversions for a DTE-based material. Geometry optimization and electronic structures have been performed by ab initio DFT calculations to improve the structural model and nicely model the solid-state optical properties. In addition, five other supramolecular assemblies have been obtained by associating normal or mixed cationic DTEs with different POM units [6]. Combined X-ray crystallographic and spectroscopic analyses have highlighted the precise impact of DTEs and POMs on the photoswitching ability of the assemblies, and gave fine understanding on synergistic effects between both organic and inorganic components. References [1] M. Irie, T. Fukaminato, K. Matsuda, S. Kobatake, Chem. Rev. 2014, 114, 12174?12277. [2] H. Dridi, A. Boulmier, P. Bolle, A. Dolbecq, J.-N. Rebilly, F. Banse, L. Ruhlmann, H. Serier-Brault, R. Dessapt, P. Mialane, O. Oms, J. Mater. Chem. C 2020, 8, 637-649. [3] P. Bolle, T. Benali, C. Menet, M. Puget, E. Faulques, J. Marrot, P. Mialane, A. Dolbecq, H. Serier-Brault, O. Oms, R. Dessapt, Inorg. Chem. 2021, 60, 12602-12609. [4] P. Bolle, Y. Chéret, C. Roiland, L. Sanguinet, E. Faulques, H. Serier-Brault, P.-A. Bouit, M. Hissler, R. Dessapt, Chem. Asian J. 2019, 14, 1642-1646. [5] P. Bolle, C. Menet, M. Puget, H. Serier-Brault, S. Katao, V. Guerchais, F. Boucher, T. Kawai, J. Boixel, R. Dessapt, J. Mater. Chem. C 2021, 9, 13072-13076. [6] O. Stetsiuk, P. Bolle, M. Cordier, J. Boixel, R. Dessapt, J. Mater. Chem. C 2022, DOI : 10.1039/D1TC04561J.

Authors : Marios Adamidis, Ioannis Konidakis, Emmanuel Stratakis
Affiliations : Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), 70013 Heraklion-Crete, Greece

Resume : Silver chloride (AgCl), as a compound among the photochromic class of silver halides, exhibits a reversible alteration in transparency and colour when exposed to sunlight and in particular, under intense ultraviolet (UV) radiation. Based on this it poses an excellent candidate for the development of advanced photochromic materials targeting a variety of applications. Aerospace applications in low earth orbit devices is among others a typical example in which the remarkable photochromic switching features of the AgCl salt could be explored. In principle, AgCl crystal can reversibly become non-transparent to the sunlight?s harmful ionizing rays that radiate onto the structure and electronics, while being transparent to higher-wavelength light (IR) that induces useful solar heat flux. Despite these benefits, a continuous scientific and technological challenge remains how to practically employ AgCl coatings and exploit its reversible photochromic features in real life applications. On this basis, we herein present a simple, low-temperature, post-glass melting encapsulation fabrication protocol in which AgCl thin layers are incorporated within silver metaphosphate glass (AgPO3). The selection of AgPO3 glass is mainly based on its relative ?soft? nature (Tg=192 oC) that allows the feasible embedment of the AgCl layer, while being transparent in most of the visible range, and thus suitable for smart photochromic windows applications. The described synthesis procedure allows the controlled positioning of a AgCl layer within the host glass matrix, while the properties of the layer itself could be modified accordingly. Namely, preliminary results show a direct dependence of the composite AgCl-AgPO3 glass photochromic response with the morphological features of the encapsulated AgCl layer, i.e. thickness and position. The photochromic response time upon varying UV irradiation dose is also considered. Ongoing work involves efforts on further enhancing the photochromic performance upon exploiting the presence of silver nanoparticles within the glass, as well as, by introducing periodic patterns on the glass surface by means of laser processing. As a final part of this study, theoretical studies of the developed composite glasses photochromic performance are conducted by means of 3U thermal nanosatellite structure model, targeting the optimization of the photochromic performance, upon varying the composition and structure of the proposed AgCl-AgPO3 glass architectures.

Authors : A. Pishtshev*(1), E. Strugovshchikov(2), S. Z. Karazhanov(3)
Affiliations : (1)Institute of Physics, University of Tartu, W.Ostwaldi 1, 50411 Tartu, Estonia;(2)University of Rovira i Virgili, Tarragona, Spain;(3)Department for Solar Energy, Institute for Energy Technology, Kjeller, Norway

Resume : Rare-earth metal oxyhydrides represent a very promising class of new materials that exhibit a powerful synergy of oxide and hydride properties due to the strong coupling of charge, lattice, and composition degrees of freedom. This opens up the most interesting possibilities for the development of highly functional materials capable of working in different environments. Our studies were motivated by the experimental work performed on the synthesis and various properties of oxyhydride chemical systems [1-3]. However, numerous studies of these systems have raised a number of fundamental questions concerning the key factors and underlying mechanisms responsible for the formation pathways, stability, structural, electronic, and electrical features of these materials [4]. For example, the synthesis of a single-phase oxyhydride material is complicated by the fact that very little is known about how to control the formation of a given structural configuration and composition during oxidation. In the context of first-principles materials engineering, our main focus has been the systematic study of the structure and mechanisms of phase formation to understand how material properties can be controlled, manipulated, and altered. Based on the results of high-performance computational and crystal chemical modeling, we performed a structure-oriented analysis of the relevant structure-property-function relationships to explore how partial oxidation, stoichiometry effects, atomic packing, and compositional differences can be used to systematically govern the physical properties of rare earth metal oxyhydrides [5,6]. In the context of multifunctionality, we describe the technological perspectives of various applications of materials derived from rare earth metal oxyhydrides. Acknowledgments: A.P. was supported by the Estonian Research Council grant PRG347, S.Z.K. received funding from the Research Council of Norway through project 309827. References: [1] V.N. Fokin et al., Russ. J. Gen. Chem. 2004, 74(4), 489. [2] T. Mongstad et al., Sol. Energy Mater. Sol. Cells 2011, 95, 3596. [3] J. P. Maehlen et al., J. Alloys Compd. 2013, 580(1), 119. [4] A. Pishtshev, S. Z. Karazhanov, Solid State Commun. 2014, 194, 39. [5] A. Pishtshev et al., Cryst. Growth Des. 2019, 19, 2574. [6] E. Strugovshchikov et al., Pure Appl. Chem. 2021, 93(11), 1293.

15:30 Discussion    
Poster Session 1 : B. Dam, F. Capon, S. Karazhanov, A. Rougier
Authors : Jian Chen, Zhen Wang, Chenglong Liu, Zhigang Chen, Xueqing Tang, Qi Wu, Shu Zhang, Shan Cong, Qin Chen, Zhigang Zhao*
Affiliations : Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China?Key Laboratory of Multifunctional Nanomaterials and Smart Systems, Chinese Academy of Sciences (CAS), 215123 Suzhou, China?Institute of Nanophotonics, Jinan University, Guangzhou 511443, China

Resume : Some butterfly species such as the orange oakleaf (Kallima inachus) have strikingly different colors on the dorsal (front) sides of their wings compared to those on the ventral (back) sides of their wings, which helps camouflage the butterflies from predators and attract potential mates. However, few human-made materials, devices and technologies can mimic such differential coloring for a long time. Here, we develop a new type of Janus-structured two-sided electrochromic devices that, upon application of different voltages, exhibits a coloration state on one side that is distinctly different from that on the other side. This is achieved by inserting an optically thin (4-8 nm) metallic layer with a complex refractive index, such as a layer composed of tungsten, titanium, copper or silver, into typical electrochromic structures. As an example, the resulting structure can appear green, mid-aquamarine, turquoise, ultramarine, deep blue-violet, and dark purple when viewed from one side, and red lilac, plum, purplish red, sandy brown, olive yellow or dark yellow when viewed from the other side. Based on this, an artificial butterfly with color variations between the dorsal and ventral wing surfaces is created, which closely resembles a dry leaf when its wings are close and exhibits various bright colors when its wings are open.

Authors : John Marc C. Puguan, Hern Kim
Affiliations : Department of Energy Science and Technology, Environmental Waste Recycle Institute, Myongji University, Yongin, Gyeonggi-do 17058, Republic of Korea

Resume : Transmissive-to-black chromism is a result of continuous pursuit of complete and null transmissive optical material for full control of the intensity and spectrum of incoming solar light in smart windows. While most transmissive-to-black devices are electrically activated, an alternative approach based on dual stimulation of a novel dual responsive molecule has been developed by anchoring asymmetrically alkylated viologen onto an engineered poly(2-isopropyl-2-oxazoline)-based polymer. Its thermochromic and electrochromic capability when triggered concurrently displays absorption of the entire visible light resulting to a black state that is ideal for building facades requiring absolute privacy. Autonomous chromic switchability is likewise conceivable by independently stimulating the material electrically or thermally where it shows unique colored state of vibrant magenta and a hazy state, respectively. Tunability of the material?s overall performance in terms of optical contrast, switching kinetics, coloration efficiency and cyclic stability based on the lattice water concentration was also elucidated. Additionally, the switchable device exhibits self-bleaching ability and short-term ?memory? effect that may expand its potential in many other applications.

Authors : Pramod Vithal Rathod, Hern Kim* Lead Presenter: Pramod Vithal Rathod, Email: Corresponding author*: Hern Kim. Email:
Affiliations : Department of Energy Science and Technology / Environmental Waste Recycle Institute Myongji University, Yongin, Gyeonggi-do 17058, Republic of Korea

Resume : This study demonstrates the synthesis of switchable single-molecule dual responsive (electrochromic and thermochromic) devices generated by tethering a viologen onto thermo-responsive poly(ionic liquid)s via an alkyl linker. With the combined properties of an electrochromic viologen and thermochromic PNIPAM and ion conductive PIL in a single molecule, this novel dual responsive (electro- and thermo-responsive) material exhibits multiple functionalities such that it acts both as an electrochrome, thermochrome, and electrolyte. One single molecule (all-in-one) single-layer device consisting of ITO/smart PIL/ITO was assembled on a glass substrate that can enhance its optical efficiency and characteristics of phase shift. The proposed smart device exhibits tunable transparency and electrochromic properties due to the thermo-responsive property of PNIPAM and the electrochromic property of a viologen and PIL as electroactive, respectively. This study?s results present a promising tool for the material design of high-performance stable devices for long-term operation in smart windows. Keywords: Dual response; Thermochromic; Electrochromic; Smart window

Authors : Yeung, C.P.K.*(1)(2), Habets, R.(1)(2), Leufkens, L.(1)(2), Colberts, F.(3), Stout, K.(3), Verheijen, M.A.(4)(5), Vroon, Z.(1)(2)(3), Mann, D.(1)(2), Buskens, P.(1)(2)(6).
Affiliations : (1) The Netherlands Organisation for Applied Scientific Research (TNO), High Tech Campus 25, 5656AE Eindhoven, The Netherlands. (2) Brightlands Materials Center, Urmonderbaan 22, 6167RD Geleen, The Netherlands. (3) Zuyd University of Applied Sciences, Nieuw Eyckholt 300, 6400AN Heerlen, The Netherlands. (4) Department of Applied Physics, Eindhoven University of Technology, 5600MB Eindhoven, The Netherlands. (5) Eurofins Materials Science, 5656 AE Eindhoven, The Netherlands. (6) Hasselt University (UHasselt), Institute for Materials Research (IMO), DESINe group, Martelarenlaan 42, 3500 Hasselt, Belgium. * lead presenter

Resume : Considering the fact that energy usage for heating and cooling of buildings is a major contributor to the energy consumption of the built environment, there is a clear need for energy-efficient windows. For intermediate climates with hot summers and cold winters, smart windows with switchable solar control properties are ideal.[1] Thermochromic materials are of interest for application in smart windows since their optical properties change based on changing outdoor temperature. In our study, we used VO2 as thermochromic material because of its reversible structural phase transition from a semiconductive monoclinic to a conductive rutile structure at a defined switching temperature of 68°C. Dopants, such as W, can reduce the switching temperature to values between 15°C and 30°C, which is required for smart windows.[1] Here, we report a nanocomposite single-layer coating comprising VO2 and SiO2, and yielding unrivalled optical properties.[2] We prepared these coatings by dip coating of a SiO2-coated float glass in an alcoholic solution of a vanadium(IV) oxalate complex and pre-oligomerized tetraethoxysilane, and thermally annealed the dried xerocoat in a two-step process. During thermal anneal of the xerocoat, phase separation occurred which resulted in Si and V rich domains. This process was studied in detail for a series of coatings with varying VO2/SiO2 ratio and varying coating thickness using high resolution transmission electron microscopy. We obtained non-scattering coatings with low surface roughness and randomly distributed VO2 nanodomains, incorporated in a SiO2 matrix. They displayed unrivalled optical properties combining Tvis > 60% with ?Tsol ? 10%. Additionally, we demonstrate that with a pencil hardness ? 4H and a stability in ambient environment of at least 11 months, the coatings are suitable for industrial processing into insulating glass units. With building energy simulations on a typical Dutch building, we demonstrated that the use of smart windows with our thermochromic coatings can lead to energy savings of 24%, which equals annual cost savings of up to 470 ? per household.[2] [1] Mann D, Yeung C, Habets R, Vroon Z, Buskens P, Comparative building energy simulation study of static and thermochromically adaptive energy-efficient glazing in various climate regions, Energies 2020, 13, 2842. [2] Yeung CPK, Habets R, Leufkens L, Colberts F, Stout K, Verheijen MA, Vroon Z, Mann D, Buskens P, Phase separation of VO2 and SiO2 on SiO2-Coated float glass yields robust thermochromic coating with unrivalled optical properties, Solar Energy Materials and Solar Cells 2021, 230, 111238.

Authors : H.Arslan, I.Aulika, A. Sarakovskis, L.Bikse, J. Gabrusenoks, M. Zubkins, J.Purans
Affiliations : Institute of Solid State Physics, University of Latvia, R?ga LV-1063, Latvia

Resume : In recent decade(s) there has been an increasing interest in the chromic materials because of the remarkable optoelectronic features they possess. Being the fact that the structural evaluation stays still uncertain, yttrium based oxyhydride thin films are the one of the most promising structures with photochromic behaviour. In contemplation of the understanding/constructing, as regards the scope of this research, the relation between crystal arrangements and spectroscopic and electrical characteristics; yttrium, yttrium oxide and yttrium oxyhydride thin films were deposited by e-beam evaporator. The deposition, around 200 nm in thickness, were carried out from metal pieces (% 99.99, Purity) at 298 K (± 5) onto Si (001) and soda-lime glass and kapton substrates. And the following approaches were performed with the intention of creating this correlation: X-ray diffraction and Transmission Electron microscopy (structural investigation), Vacuum Fourier transform infrared spectrometer (vibrational spectrum analysis), Spectroscopic ellipsometer (optical characterization), X-ray photoelectron spectroscopy (oxidation state determination), and X-ray absorption spectroscopy (local structure analysis and chemical state identification). The findings of the absorption edge (K) of yttrium reveal that the oxidation state of Y in oxyhdride structure stays in the between the metallic yttrium and fully oxidized yttrium structure that corresponds to an unusual oxidation state. This result is in correspondence with the outcomes obtained from XPS, where the binding energy (Y 3d) shifts to the higher values depending on the chemical state of yttrium. The fully oxidized yttrium lattice vibrations at around 300, 380 and 550 cm-1 were detected by IR spectroscopy for yttrium oxide and yttrium oxyhydride thin films. The differences in the intensities and the widths of the vibration peaks indicates either the H atoms disturb the original cubic structure of sesquioxides and /or formation of new phases. This effect is visible either in the TEM images or on the X-ray diffractograms. The findings from this study might enhance our understanding on the arrangements of H atoms in the host crystal structure which is directly related to the photochromic demeanour. This research is partially supported by The Latvian Council of Science (LZP FLPP) Nr. lzp-2020/1-0345

Authors : Ayushi Rai1, Vidar Hansen1, Cristian N. Mihailescu2, and Andreas Delimitis1
Affiliations : 1 Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, PO box 8600, N-4036 Stavanger, Norway 2 National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, 077125 Magurele, Romania

Resume : Thermochromic materials based on VO2 thin films and multilayers are highly promising candidates for applications in smart windows, due to their ability of solar modulation and luminous transmittance. Prevention or minimization of energy losses and enhancement of the thermal performance of the glass will reduce energy consumption in buildings and prevent excess CO2 emissions. Their efficiency is governed by precise control and minimization of the critical temperature Tc by various ways, buffer layers or imposed strain being some of them. In this study, a detailed structural characterization of VO2 thin films has been performed, using predominately electron microscopy methods, post-experimental image analysis and processing. The VO2 thin films have been grown by Pulsed Lased Deposition (PLD) on (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT) or Si substrates, with variable thickness. The general morphology, film thickness, interfacial and surface roughness, crystallographic orientation and epitaxial relationship of films and substrates were deduced. Microscopy results revealed that thin films adopt a columnar morphology and predominately crystallize in the rutile VO2 polymorph, although regions of the monoclinic VO2 phase have been also detected. These findings are consequently compared with complementary physical property measurements of the VO2 thin films and discussed in detail.

Authors : Belenchuk, A.(1,2), Stroh, K.(3), Shapoval, O.(1,2), Vatavu, S.*(1)
Affiliations : (1) Physics of Semiconductors and Devices Lab, Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD 2009, Chisinau, Moldova; (2) Solid State Structures Lab, Institute of Electronic Engineering and Nanotechnologies, 3/3 Academiei str., MD 2028, Chisinau, Moldova; (3) I. Institute of Physics, Georg-August University of Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen, Germany

Resume : The first-order insulator-to-metal transition of VO2 at 68°C keeps VO2?based coatings at the top amid promising thermochromic materials for energy-saving windows with smart control of solar heat transmission. However, for actual applications, the thermochromic performance of VO2?based coatings must be optimized by lowering the transition temperature, increasing the luminous transmittance, and improving the switching parameters. To address all the above challenges in polycrystalline films, an alternative strategy is highly demanded. Here we show an improvement of all issues together by combining a nanothermochromic approach for enhancing the luminous transmittance with a strain-driven one for reducing both the transition temperature and hysteresis loop width. The laminar VO2-TiO2 nanocomposite films were fabricated by a temperature-driven spinodal decomposition of VxTi1xO2 solid solution. The latter was grown on fused quartz substrates by using a cost-effective technique of metalorganic aerosol deposition. The optical properties of the nanocomposites were compared to those of single-phase VO2 by measuring the transmittance in the wavelength range of 400÷2500 nm at temperatures 25÷100°C. The nanocomposite film reveals a 15-degrees reduced transition temperature and a 7-degrees narrowed hysteresis loop width, pointing to a strained state, which emerges as a result of the elastic coupling between V- and Ti-rich layers. The nanocomposite films exhibit a 5% integral luminous transmittance enhancement, demonstrating the nanothermochromic approach principle in action. In our case, this approach was realized by the integration of functional VO2?rich layers into a more transparent matrix of TiO-rich ones. As a result of both advances, the thermochromic performance, which was calculated as the difference between integral solar transmittances at 25°C and 100°C, increases up to 14% for the nanocomposite compared to 8.5% for VO2. We expect that subsequent process optimizations may further enhance the thermochromic performance, opening thus the way to the application of strained VO2-TiO2 nanocomposites as thermochromic coatings for smart windows. Financial support from Deutsche Forschungsgemeinschaft via SFB 1073 (TP Z02 and B02) and Moldavian State Program 20.80009.5007.12 is acknowledged.

Authors : Ana-Maria IORDACHE1, Stefan-Marian IORDACHE1, *, Roxana BOHILTEA2, *, Valentin BARNA3, Constantin RIZEA4, Alexandra MAZLUM4, Valentina CAPATINA5, Cristiana Eugenia Ana GRIGORESCU1
Affiliations : 1National Institute of R&D in Optoelectronics, INOE 2000, 409 Atomistilor, 077125, Magurele, Jud. Ilfov, Romania23 2Carol Davila" University of Medicine and Pharmacy Bucharest, 37 DionisieLupu, 020021, Bucharest, Romania 3University of Bucharest, Faculty of Physics,405 Atomistilor, P.O. Box MG-38, 077125, Magurele, Romania 4Roxy Veterinary S.R.L.,52AUnirii Str.,Magurele, 077125, Romania 5MGM Star Construct S.R.L., 7B Pancota Str., Bucharest, Romania

Resume : In this paper, we report the fabrication of a chromogenic sensor for fast identification of Candida spp. The responsible mechanism is chemo-recognition: functionalized materials with targeted sensitivity towards VOCs produced by Candida species are immobilized onto a disposable, low cost and simple SiO2 support. The color changes when the sensitive layer is exposed to a medium containing Candida species. This color variation can be clearly seen with the naked eye. This sensor can be used by physicians as a new instrument for real-time identification of pathological cases involving candidiasis. This is extremely important in obstetrics because infections can be transmitted to the newborn. Keywords: chromogenic sensor, Candida spp., medicine sensor. Acknowledgements: 87PD/2020, 393PED/2020, 18/N/2019, 18PFE/30.12.2021

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Session IV : Smagul Karazhanov – Chih-Wei Hu
Authors : Chih-Wei Hu, Kaori Nishizawa, Yasusei Yamada
Affiliations : Innovative Functional Materials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Japan

Resume : Here we introduce two of our recent results in gasochromic (GC) materials. One shows the first multi-color changeable gasochromic characters and the other has a superior waterproof property that could be used in a humidity environment. The first GC material is composed of polyaniline (PANI) conducting polymer, neutral red (NR) dye, and polystyrene sulfonate (PSS), which is named PANI-NR:PSS nanocomposite. Neutral red dye serves as a doping compound to attach on PANI main chain and PSS side, then provide complementary absorbance in the visible range. Platinum nanoparticles (PtNPs) are coated onto the PANI-NR:PSS film surface to obtain the hydrogen spillover ability for gasochromic application. A simple two layers structure, PtNPs/PANI-NR:PSS/substrate can be easily obtained by wet-coating methods. When thin films are exposed to H2, PANI-NR:PSS film switches from deep brown to transparency with a maximum transmittance change (?T) of 55.6 % at 700 nm, which accompanies a broad transmittance change in the whole visible range. PANI-NR:PSS film switches to the red intermediate state after exposure to air shortly, then slowly back to their neutral color. Cyclic voltammetry analysis shows PANI-NR:PSS film is only suitable for GC application but not electrochromism due to the weak attach force of NR on polymers. The second GC material is based on Prussian blue nanoparticles (PBNPs) with hydrophobic ligands on their surface. In order to enhance the initial H2 response-ability, ethanol post-processing is been used to further modify the surface of those hydrophobic PBNPs. PBNPs thin films show novel waterproof ability and GC characters. The gasochromic mechanisms of both GC materials are proposed. CV, in-situ FT-IR analyses, UV?Vis absorbance spectra, optical transmittance kinetic curves, SEM, and AFM are used to measure the properties of both GC materials.

Authors : Sungjun Choi* (1), Jiseon Kim (1), Dongwon Shin (1) and Caroline Sunyong Lee (?,1)
Affiliations : (1) Department of Material science & Chemical engineering in Hanyang University, Korea (?

Resume : A zero-energy building minimizes energy loss using high-performance insulation materials and high-airtight windows to enhance the building's energy performance. Smart windows are mainly used as windows of zero-energy buildings. Smart windows have the advantage of saving energy loss caused by indoor cooling and heating through solar heat control using electrochromism. Therefore, we attempted to fabricate a trimodal electrochromic device for a smart window that can be applied to a zero-energy building. Transparent, black, and mirror states were implemented through the manufactured device. The device used in this study was fabricated using WO3 thin film, ITO glass, and silver electrolyte. WO3 was deposited using a dry deposition method (NPDS; Nano-Particle Deposition System). NPDS is a deposition method by accelerating the powder in the nozzle to supersonic speed due to the pressure difference between the chamber and the nozzle in a low vacuum atmosphere. Through this, NPDS has the characteristic of being able to produce a rough and thin-film while dry deposition is possible in a room-temperature atmosphere. Using these characteristics, silver was deposited on the rough WO3 thin film to increase light scattering. To measure its characteristics, transmittance and reflectance were measured. Through this, nearly 0% transmittance was obtained when implementing the Black mode. In addition, when silver was deposited on the ITO substrate, 75.77% of reflectance was obtained at a wavelength of about 600 nm by implementing a mirror mode. It was attempted to be applied in various environments through each mode using the manufactured device. For the transparent state, solar heat was entered into the room on a cold day and insulated the internal thermal energy. The black mode was used to absorb light in the evening when the temperature is lowest to use the insulation effect. Finally, the mirror mode was used to reflect the solar heat on a hot day to keep the internal temperature cool to reduce air conditioning. The stability of the device was confirmed through the CV test and cycle test. Tsol is a numerical value indicating the transmittance of solar heat energy that enters the room through the windows. By measuring Tsol, the amount of solar energy entering the room through the device was measured, while checking the possibility of the fabricated trimodal device as a smart window for a zero-energy building.

Authors : Gillissen, F.*(1,2), Maho, A.(1), De Moor, N.(3), Faceira, B.(4), Lobet, M.(3), Rougier, A.(4), Henrard, L.(3), Cloots, R(1).
Affiliations : (1) Group of Research in Energy and Environment for MATerials (GREEnMAT), University of Liège, Allée du Six Août 13, 4000 Liège, Belgium; (2) FRS ? FNRS, Rue d?Egmont 5, 1000 Bruxelles, Belgium ; (3) Laboratoire de Physique du Solide, University of Namur, Rue de Bruxelles 61, 5000 Namur, Belgique ; (4) Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), University of Bordeaux, Avenue du Dr Albert Schweitzer 87, 33600 Pessac, France. * lead presenter

Resume : The development of advanced energy efficient fenestration technologies capable to selectively modulate both visible (luminosity) and near infrared (NIR) wavelengths (heat) ranges are expected to further improve the energetic performances of conventional smart windows, offering an optimal use adapted to a large range of weather and meteorological conditions, and better respond to the user?s preferences. In many configurations, smart windows are made of inorganic electrochromic materials based on transition metal oxides (WO3, NiO, V2O5) formulations, in which the optical properties of the active species are modified through the insertion/extraction of electrons and cations (H+, Li+,?) into the crystal lattice and the ensuing reduction/oxidation of the metallic ions. When exploiting nanocrystals of highly doped semi-metal oxides (ITO, AZO, Cs-doped WO3) as advanced electrochromic materials, the optical modulation occurs mainly in the NIR range thanks to the electrochemical modulation of the localized surface plasmon resonance (LSPR) effects in the nanoparticles, ruling their carrier concentration (10^21-10^22 cm-3) and therefore their absorption wavelength. In this context, Yamashita et al. were able to synthesize an oxygen-deficient molybdenum-tungsten hybrid oxide displaying a very strong LSPR signal around 700 nm, straddling both visible and NIR regions. This position of the plasmonic resonance frequency and its intensity makes this hybrid oxide an interesting candidate for the development of a novel electrochromic formulation exhibiting the selective modulation of visible and NIR wavelength with good contrasts between the different operating modes. In this work, we study the synthesis, dispersion and wet deposition of hybrid molybdenum-tungsten oxide as ?new generation? electrochromic material. The hybrid oxide is successfully synthesized through a one-step hydrothermal route. The recovered powder can be dispersed in low toxic solvent and coated onto glass substrates by spin or bar coating. The morphological, structural and optoelectronic properties of the powders and films are investigated through characterization methods including SEM, DRX, XPS, EPR, UV-VIS-NIR spectrophotometry and electrochemistry. The best results are obtained for an initial Mo/W ratio of 2/1, treated hydrothermally for 1h at 160°C, with the hybridation process leading to the formation of a high ratio of oxygen vacancies in the crystal lattice. In-situ spectroelectrochemistry characterizations highlight the dual-band solar-control function of thin films processed on conducting glass substrates from this formulation, with transmittance contrasts (respectively in VIS and NIR ranges) of 10 and 22% in the intermediary ?cool? mode, and of 31 and 68 % in the ?fully dark? mode. This research is funded by FRS ? FNRS (Projet de Recherches PDR ?PLASMON_EC? #T.0125.20).

Authors : Cots, A. (1)*, Raho, R. (2)a, Dicorato, S. (2)b, Magni, M. (3), González, R.M. (1)c, Martínez, S. (1), Manca, M.(1)
Affiliations : (1) LEITAT Technological Center, c/ de la Innovació, 2, 08225, Terrassa (Bacelona)- SPAIN; (2) IIT-CBN Istituto Italiano di Tecnologia- Center for Biomolecular Nanotechnologies, via Barsanti 14, 73010, Arnesano (Lecce)- ITALY; (3) Università degli Studi di Milano, Dipartamento di Chimica, via Golgi 19, Milano- ITALY; * lead presenter

Resume : Motivated by the great potential to reduce the energy consumption for heating, cooling and lighting,[1] the research in the field of solar control glazing has been moving towards the development of intelligent electrochromic windows whose optical features can be tuned in-situ to provide a dynamic selective control of the intensity incoming solar radiation in the NIR range.[2] These systems promise to enable the development of a new generation of intelligent dynamic glazing technologies capable of maximizing both the visual and thermal comfort and minimizing the energy loses for overheating and overcooling. To this aim, spectral selectivity still represents a key issue towards the market up-taking of the 2nd generation smart electrochromic glazing. Our achievements in this field range from understanding the fundamental spectroelectrochemical properties of engineered plasmonic electrochromic films [3] (also referred as ?plasmochromic?) to the fabrication of large-area dual-band electrochemically tunable devices, which make available a full series of vis/NIR spectral modes that can be independently controlled through the sign and intensity of the external applied potential. To bring plasmochromic technology at a pre-industrialization TRL, it is essential to replace the conventional liquid electrolytes with more robust solid or semi-solid electrolytes, capable of enabling manufacture processes for compact, laminable structures free from leaks. In this regard, the manufacturing of stable plasmochromic devices based on polymeric gel electrolytes is here presented [4] along with a preliminary assessment of their superior benefits in terms of energy savings and visual comfort. In addition, some insights about the development of these systems on flexible substrates ? based on a roll-to-roll fabrication process that enable low manufacturing costs ? are also provided. References [1] Nunes, C; Timmermans, T. ADVANCED BUILDING SKINS (conference proceeding), 2019, Electrochromic windows with smart control to deliver promised comfort and energy performance. [2] Llordés, A.; Garcia, G.; Gazquez, J., Milliron, D. J.; Nature 2013, 500, 323?326 [3] Giannuzzi R.; Scarfiello, R.; Sibillano, T.; Nobile, C.; Grillo, V.; Giannini, C.; Cozzolib, P.D.; Manca M. Nano Energy, 2017, 41, 634-645 [4] Cots, A.; Dicorato, S.; Giovannini, L.; Favoino, F.; Manca, M. Nano Energy, 2021, 84, 105894

Authors : A. Ambreen 1,2, A. Sekkat 1, D. Muñoz-Rojas1, D. Bellet 1, A. Rougier 2
Affiliations : 1Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38000 Grenoble, France 2CNRS, Univ. Bordeaux, Bordeaux INP, ICMCB, UMR 5026, F-33600 Pessac, France

Resume : Transparent electrode is a key component in many devices such as solar cells, flexible light-emitting devices, transparent heaters and electrochromic devices (ECDs). The latter have attracted great attention due to their potential applications, for instance in smart windows and other energy-efficient devices. ECDs can control the amount of heat entering or leaving a building; therefore, they can decrease the need for energy-intensive heating or air conditioning. These devices use electrochromic materials, which reversibly change the colour upon oxidation and reduction, in response to an applied voltage [1]. The most efficient and widely used transparent electrode for these devices is indium tin oxide (ITO) owing to its high transparency and electrical conductivity. However, the scarcity of indium and brittleness urged a new flexible, stable and low-cost transparent electrode having properties comparable to ITO. Silver nanowire networks appear as a promising alternative to ITO thanks to their high optical transparency, excellent electrical properties and mechanical flexibility [2]. Indeed silver nanowires based transparent electrodes are gaining more and more attention. In order to improve the integration of silver nanowire networks into industrial devices, their stability when submitted to electrical and/or thermal stress should be enhanced. The aim of the present contribution is to prepare stable silver nanowires deposition through spray-coating on glass substrate. The parameters of deposition such as speed, number of cycles and concentration of silver nanowires solution are optimised in order to optimize physical properties. To overcome the instability issues, silver nanowire networks are coated with a thin conformal zinc oxide layer using atmospheric pressure spatial atomic layer deposition [3]. The influence of zinc oxide layer deposition conditions on silver nanowires network properties and stability will also be presented. The obtained silver nanowire based transparent electrode are designed for future integration into electrochromic device used for smart windows applications. References 1. Mjejri, I., et al., Crystallized V2O5 as oxidized phase for unexpected multicolor electrochromism in V2O3 thick film. ACS Applied Energy Materials, 2018. 1(6): p. 2721-2729. 2. Sannicolo, T., et al., Metallic nanowire?based transparent electrodes for next generation flexible devices: a review. Small, 2016. 12(44): p. 6052-6075. 3. Munoz-Rojas, D. and J. MacManus-Driscoll, Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics. Materials Horizons, 2014. 1(3): p. 314-320.

10:30 Discussion    
Session V : Bernard Dam - Juris Purans
Authors : Juris Purans
Affiliations : Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063, Riga, Latvia

Resume : X-ray absorption spectroscopy (XAS) is an ideal non-destructive technique for characterizing chromogenic materials, devices as well as for the study of chromogenic processes [1-3]. Synchrotron radiation XAS, comprised of both the high-resolution near-edge structure (XANES) and extended fine structure (EXAFS), is element sensitive to the local physical and electronic structure about both the metal (W, Ir, Mo, Ni, etc.) and oxygen target atoms in the chromogenic oxides. Starting from our pioneering works in the 90s, we have applied XAS to the study of cathodic electrochromic oxides such systems as WO3, WO3-NiO, MoO3, ReO3-WO3 [4] and to anodic oxides such as NiOx, IrOx, and recently ZnO-IrOx, NiO-VOx, NiO-IrOx. In the study of thermochromic materials, XAS has been applied to V(W)O2, CuWO4-ZnWO4, and recently, to the photochromic YH3 and Y-O-H systems [3]. Here we examine chromogenic metal oxides of tungsten, molybdenum, iridium, nickel and mixed oxides and compare them to related crystalline species in order to set a foundation for the structure-property relationships in these oxides. In the amorphous electrochromic oxides (a-WO3, a-MoO3, a-ReO3, a-IrOx, a-Ta2O5, a-V2O5), the EXAFS analysis indicates the first coordination shell consists of oxygen atoms in a distorted octahedral geometry, with a second shell consisting of metals. No higher shells are observed beyond 3.5 ? for all samples, indicating the metal oxides are truly amorphous, consistent with X-ray diffraction results. While in the nanocrystalline anodic films (n-NiO, n-NiO-IrOx), the EXAFS analysis indicates the structural peaks well visible up to 6 ?. The effect of size reduction is observed as a progressive decrease in peak amplitude upon increasing distance [2]. The oxidation state and local geometry of the metal centers in amorphous or nanocrystalline thin films of WO3 (W6+/W5+ oxidation state), IrOx (Ir4+/Ir3+), Y-O-H (Y3+/Y2+) are determined using XANES spectroscopy. Financial support was provided by ERDF Project no. [1] J. Purans, A. P. Menushenkov, S. P. Besedin, A. A. Ivanov, V. S. Minkov, I. Pudza, A. Kuzmin, K. V. Klementiev, S. Pascarelli, O. Mathon, A. D. Rosa, T. Irifune, M. I. Eremets, Local electronic structure rearrangements and strong anharmonicity in YH3 under pressures up to 180 GPa, Nat. Commun. 12 (2021) 1765. [2] A. Kuzmin, J. Chaboy, EXAFS and XANES analysis of oxides at the nanoscale, IUCrJ, 1 (2014) 571. [3] I. Pudza, A. Kalinko,A. Kuzmin, Study of the thermochromic phase transition in CuMo1-xWxO4 solid solutions at the W L3-edge by resonant X-ray emission spectroscopy, Acta Mater. 205 (2021) 116581. [4] B. Polyakov, E. Butanovs, A. Ogurcovs, A. Sarakovskis, M. Zubkins, L. Bikse, J. Gabrusenoks, A. Kuzmin, J. Purans, Study of layered and mixed ReO3-WO3 thin films deposited by reactive DC magnetron sputtering, ACS Omega 7 (2022) 1827.

Authors : Maho, A.* (1), Saez Cabezas, C.A. (2), Gillissen, F. (1), Kim, D.K. (3), Heutz, S. (3), Milliron, D.J. (2), and Cloots, R. (1)
Affiliations : (1) Group of Research in Energy and Environment for Materials (GREENMAT), University of Liège, B6a ? Agora, Allée du Six-Août 13, 4000 Liège, Belgium. (2) McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States. (3) Department of Materials, Imperial College London, Prince Consort Road, SW7 2AZ London, United Kingdom. * lead presenter

Resume : Tin-doped indium oxide (ITO) has been used for decades as efficient visibly-transparent conducting material in numerous optoelectronic devices. When processed as nanocrystals (NCs), ITO bears localized surface plasmon resonance (LSPR) properties allowing for intense absorption in the near-infrared (NIR) wavelength range. Following their thin film wet deposition onto conducting glass electrodes, ITO NCs assemblies submitted to an external electrical bias show a selective and controlled modulation ability of the NIR transmittance, independently of the optical behavior in the VIS range, as a consequence of NCs carrier concentration tuning. ITO is therefore highlighted as a benchmark plasmonic electrochromic material for dynamic heat-filtering smart windows devices showing extremely fast switching kinetics as well as high optical contrasts, coloration efficiency, and cycling durability. This talk will address different colloidal methodologies leading to stable and easily-workable dispersions of ITO nanocrystals in highly polar and low-toxic media. More specifically, we will discuss the progressive elaboration of aqueous ITO dispersions from the re-functionalization of the nanocrystals surface previously stripped of their native hydrophobic ligands with a hydrophilic polymer. Alternatively, a one-step solvothermal protocol in benzyl alcohol is considered to synthesize ITO NCs that are straightforwardly dispersible in alcohol media (methanol, ethanol, isopropanol), without the need of extra additives or surfactants. In both cases, dispersions are then used as ?precursor inks? in spray deposition processes, leading to uniform and highly-covering electrochromic thin films onto glass substrates. Ultimately, optical and electrochemical properties of the generated NIR-modulating layers are shown to be strongly dependent on the synthetic and post-synthetic treatments and conditions. The presentation will also tackle original concepts of sustainable, self-powered architectures of plasmonic electrochromic layers and devices. These involve singlet fission organic chromophores in a will to provide a sufficient amount of electrons that will accumulate in the deposited layers of ITO NCs, and thereby allow the dynamic tuning of their LSPR properties without the need of an external electrical bias. More particularly, the hybridization of pentacene and tetracene molecular layers, processed through organic molecular beam deposition, with ITO NCs films will be explored and discussed.

Authors : B. Faceira*, L. Teule-Gay, A. Rougier
Affiliations : Université de Bordeaux, CNRS, BxINP, UMR5026, F-33600 Pessac, France

Resume : Electrochromic (EC) materials and devices, able to modify their optical properties under applied voltage, are recognized as one of the key green technologies for sustainability and energy savings. Smart windows in residential and commercial buildings are one of the typical example of applications [1]. Among electrochromic oxides, WO3 shows a cathodic coloration upon reduction with insertion of small cations (H+, Li+, Na+) associated with a visual change from colourless to dark blue. Aiming at low energy consumption devices and applications, the unusual property of so-called the memory effect, known as the persistence of the coloured state for electrochromic materials under open circuit conditions, has recently received particular attention. Herein, WO3 films from 200 nm to 400 nm were grown by Radio-Frequency Magnetron Sputtering (RFMS) using WO3 ceramic target. While maintaining good performance, the adjustment of the sputtering conditions allowed a careful control of the memory effect. Depending on the substrate temperature (RT or 400°C) during the deposition process, amorphous or crystalline thin films were obtained. The optimisation of the deposition conditions, including power density and oxygen partial pressure, allows to produce WO3 thin films with high optical modulation. Values of transmittance modulation at 550 nm increases from 64% for crystalline films to 83% for amorphous ones. The optical memory effect of WO3 is characterised by an evolution of the visible transmittance in air which strongly depends on the film crystallinity (25% increase for crystalline versus only 2% for amorphous films at 550 nm in 35 days). Hence in air, amorphous films show a longer memory effect than crystalline ones. In an electrolyte media, the transmittance slowly increases of about 0.7% in 20h for both films illustrating an influence of the environment on the memory effect. In this presentation, the relationship between crystallinity, composition, thickness and optical memory effect will be discussed. [1] C.G. Granqvist, M.A. Arvizu, ?. Bayrak Pehlivan, H.-Y. Qu, R.-T. Wen, G.A. Niklasson, Electrochromic materials and devices for energy efficiency and human comfort in buildings: A critical review, Electrochimica Acta, 259 (2018) 1170?1182.

11:45 Discussion    
12:00 Lunch break and Plenary Session    
Session VI : Smagul Karazhanov – Elbruz Murat Baba
Authors : Elbruz Murat Baba* 1-2 , Chang Chuan You 2, Erik Roenneberg 1, Smagul Karazhanov 2
Affiliations : 1 Sunphade AS, Oslo, Norway; 2 Department for Solar Energy, Institute for Energy Technology (IFE), Kjeller, Norway

Resume : Rare earth oxyhydrides (REHO) belong to an emerging class of mixed-anion compounds and contain both oxide and hydride anions. While conventional solid-state research has focused on the chemistry surrounding the cation(s), investigations focused on anion chemistry have only recently begun. Upon illumination with sunlight, thin films of the REHO exhibit photochromic properties at ambient temperatures and pressures. The property present interest for applications in windows and glasses as the optical control coating for suppressing glare and blockage of harsh ultraviolet part of the sunlight. The present talk is focused on window and some other possible applications of the yttrium oxyhydride (YHO). The talk includes future perspectives, market requirements, advantages and deficiencies of using the photochromic coatings on windows, and challenges related to it. One of the challenges is related to understanding the mechanism of photochromic effect and of degradation. The talk will include some preliminary information about it also.

Authors : D. Mamedov, S. Zh. Karazhanov
Affiliations : 1) Department for Solar Energy, Institute for Energy Technology, 2027 Kjeller, Norway 2) Department of Materials Science, National Research Nuclear University, 115409 Moscow, Russia; 1) Department for Solar Energy, Institute for Energy Technology, 2027 Kjeller, Norway 2) Department of Materials Science, National Research Nuclear University, 115409 Moscow, Russia

Resume : Cerium dioxide (CeO2) as well as other Rare-Earth Oxides (REOs) is known as water repelling material which enables their usage in glass industry. One of the limitation factors towards real practical application of CeO2 as transparent layer remains high refractive index and absorption in the visible range which can be overcome by doping. In this study, we investigate electronic, optical and wetting properties of pure and doped CeO2 by first-principles calculations. It is found that tetravalent doping atoms (Zr, Ti, Sn and Si) significantly modify the optical response of CeO2 by shifting the absorption edge which also effects on the refractive index of the material. For these systems, the water contact angle has been computed through adsorption energy of water layers. We report the intrinsic hydrophilicity of the low-index surfaces of CeO2, which is enhanced by introduction of the impurity atom. Influence of the dopants on the oxygen vacancy formation energy E_f (V_O ) is considered and discussed with respect to its possible effect on the hydrophobic behavior of CeO2. It is found out that all the considered doping atoms reduce E_f (V_O ) , resulting in enhanced adsorption of the air hydrocarbons at the surface, which leads to an increased water contact angle. Based on the obtained results it is concluded that Zr-doped CeO2 possesses the most prominent properties among considered systems for the application as transparent layer in glass industry.

Authors : M. Zubkins, I. Aulika, J. Gabrusenoks, E. Strods, V. Vibornijs, G. Chikvaidze, L. Bikse, A. Sarakovskis, H. Arslan, J. Purans
Affiliations : Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063, Riga, Latvia

Resume : Neither the structure of photochromic oxygen-containing yttrium hydride (YHO) nor the responsible mechanism of photochromism is fully understood. The synthesis of YHO films is based on the oxidation of deposited yttrium hydride in ambient conditions. The actual state of the films during the deposition process, which is influenced by the deposition pressure and the oxidation caused by the residual gases, is not completely known. We report on the YHxOy and the isotopically exchanged YDxOy thin films deposited by reactive pulsed-DC magnetron sputtering. Since the visible light transmittance is closely related to the phase and chemical composition of the films, in situ transmittance measurements during and after deposition are performed to investigate the oxidation in more detail. Spectroscopic ellipsometry is used to determine the optical constants of YHxOy throughout the film thickness. In order to obtain metallic YH2-x films with a low oxygen content, a low sputtering pressure (< 1 Pa) is required, otherwise the films are already partially transparent during the deposition. The oxidation is faster when higher deposition pressures are used. This is due to the more porous growth of the microstructure at higher pressures that is observed at the surface and cross-section images of the films. The films exhibit a refractive index gradient perpendicular to the substrate surface, which is related to the porosity and variation of the chemical composition [1]. Vibrational spectroscopy techniques (Raman and FTIR) were exploited to study the structure of YHxOy in more detail. Several measurement techniques/geometries and samples/structures were used. The detected vibration bands are relatively wide due to the disordered structure and small crystallite size of approximately 10 nm determined from XRD data. This is the result of low temperature deposition by reactive sputtering, which can be considered as a non-equilibrium process. Both experiment and theory were used to interpret the spectra. Isotopically exchanged films were synthesised to identify hydrogen related vibrations. Based on the theoretically stable YHxOy structures [2] and our XRD data, YHxOy was modelled using the crystallographic structure belonging to different space groups. Linear combination of atomic orbitals (LCAO) method within the framework of the hybrid density functional approach was used. LCAO calculations, including analyses of phonon frequencies and vibration intensities, were performed using algorithms as implemented in CRYSTAL17 code. [1] Oxidation dynamics and optical properties of oxygen-containing yttrium hydride thin films, Vacuum, 2022, article in review. [2] Cryst. Growth Des. 2019, 19, 2574?2582. Financial support was provided by ERDF Project no.

Authors : Aurély BAGGHI Philippe DENIARD Hélène SERIER-BRAULT Rémi DESSAPT
Affiliations : Institut des matériaux Jean Rouxel (IMN), UMR 6502 CNRS, Université de Nantes, 2 rue de la Houssinière, BP 32229, 44322 Nantes cedex 3, France

Resume : The detection and quantification of water either as trace in organic solvents, or as relative humidity (RH) in air have attracted wide interest over the past years, because of their great significance in industrial process controls, batteries life extension and indoor air quality improvement [1]. In the last six years, photoluminescent (PL) solid sensors for water molecules [2] have been considered as an attractive potential alternative to traditional analytical technics due to their faster response, higher sensitivity and ability of in situ detection. However, new sustainable and reusable sensors are still highly desirable. Polyoxometalates (POMs) are molecular oxides of transition metals (W, Mo, V) which are widely investigated as PL sensors of a wide range of analytes in aqueous solution,[3] but their ability to detect water in gas and liquids have been very scarcely explored [4]. Moreover, most of POM sensors incorporate lanthanide (Ln3+) ions as active emission centers, but considering rising costs associated with the difficulties of extracting or recycling rare earths, PL Ln-free POM sensors represent a promising lower cost alternative. We have recently designed new crystallized anhydrous alkali Ln-free POM materials and their structures have been solved from ab initio powder X-ray diffraction analysis.[5] These materials are highly luminescent at room temperature and exhibit reversible vapoluminescence properties in the presence of water. Indeed, upon exposure to a humid atmosphere, they are fully converted into their crystallized hydrated analogues, and the rehydration processes are accompanied by strong and complete PL quenching effects. Moreover, the rehydration rate of these materials can vary in function of their counterion. The anhydrous phases quantitatively sense relative humidity in the air with limit of detection values around 2% which are among the best values of recent PL sensors. Moreover, they can also detect trace amounts of water (0.008 v%) in acetonitrile. Finally after use, the complete regeneration of the PL-active anhydrous phases can be achieved by simple thermal dehydration, making them highly relevant for the development of new sustainable and reusable heterogeneous solid sensors. [1]. H. Sung Jung, P. Verwilst, W. Young Kim, J. Seung Kim, Chem.Soc.Rev., 2016,45,1242. [2]. Y. Guo, W. Zhao, Analyst, 2019, 144, 388-395. [3] (a) W. Salomon, A. Dolbecq, C. Roch-Marchal, G. Paille, R. Dessapt, P. Mialane, H. Serier-Brault, Front. Chem., 2018, 6, 425. (b) N. Lei, D. Shen, X. Chen, Soft Matter, 2019,15, 399-407. [4] Qiu, Y.-F.; Liu, H.; Liu, J.-X.; Zhang, C.; Ma, Z.; Hu, P.-A.; Gao, G.-G. J. Mater. Chem. C 2015, 3, 6322?6328. [5] Article in preparation

Authors : William René, Véronique Lenoble, Katri Laatikainen, Catherine Branger
Affiliations : William RENE, Université de Toulon, MAPIEM Laboratory, France & Aix Marseille Université, CNRS, IRD, MIO, Toulon, France; Véronique LENOBLE, Aix Marseille Université, CNRS, IRD, MIO, Toulon, France; Katri LAATIKAINEN, Lappeenranta-Lahti University of Technology LUT, School of Engineering Science, Department of Separation Science, Lappeenranta, Finland; Catherine BRANGER, Université de Toulon, MAPIEM Laboratory, France

Resume : Fluorescent ion-imprinted polymers (IIPs) are a class of smart materials that can convert the selective binding of a target ion into a fluorescent signal. IIPs are synthetic polymers with remarkable recognition properties. Combined with various transduction mechanisms, they are the key stones of a large panel of chemical sensors thanks to these high recognition properties, their easy synthesis and their high stability. In a classical approach of IIP preparation, a target ion interacts with a functional monomer and a cross-linker in a porogen solvent. After polymerization, the removal of the template generates the recognition cavities inside the three-dimensional copolymer network. Fluorescent IIPs are prepared in a similar manner by introducing as a functional monomer a fluoroionophore functionalized by a polymerizable group. In the present work, we designed new fluorescent Pb(II) imprinted polymers based on an original fluorescent functional monomer prepared by coupling the chelating 5-amino-8-hydroxyquinoline moiety with anthracene as the fluorescent dye and styrene as the polymerizable group. This monomer was specially designed to present an ?off-on? effect upon Pb(II) binding to improve the sensitivity of the sensor. The synthetic conditions for the preparation of the IIPs were first optimized by studying the complex formation between the monomer and Pb(II) in the polymerization conditions. Then, the influence of other parameters, such as the polymerization solvent and the crosslinker (ethyleneglycol dimethacrylate, EGDMA, or divinylbenzene, DVB), was also evaluated. Solid-state 13C NMR spectroscopy was used to analyse the structure of the polymers and confirmed the correct integration of the fluorescent monomer in the polymer matrix. The morphology of the prepared materials was studied by scanning electron microscopy and nitrogen adsorption/desorption experiments. The binding and selectivity properties of the IIPs were determined by three-dimensional fluorescence through the realisation of fluorescence excitation-emission matrices. These measurements revealed that the IIPs showed remarkably selective fluorescent on-off characteristics towards Pb(II) compared to their corresponding non-imprinted polymers, emphasizing an imprinting effect. The IIPs based on EGDMA as a crosslinker were very sensitive to the presence of Pb(II) ions and almost not to other tested ions (Ag(I), Na(I), Ca(II), Cd(II), Co(II), Cu(II) and Zn(II)), even introduced in high excess. Calibration curves were performed in various matrices: ultra-pure water, buffered water at pH 7.0 and 8.1, seawater, tap water. They highlighted the low impact of the tested matrices onto the detection leading to a limit of detection as low as 2.1 µg/L for the best IIP. The very good recovery obtained in natural samples emphasized the potential for the synthesized IIP to detect Pb(II) in natural waters.

16:45 Discussion and Closing Session    

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Symposium organizers

87 Avenue du Dr Albert Schweitzer, 33608 Pessac, France

+33 (0)5 40 00 62 63
Bernard DAMDelft University of Technology, Chemical Engineering

Van der Maasweg 9, Delft, The Netherlands

+31 152784342
Fabien CAPONInstitut Jean Lamour

Campus Artem, 2 allée André Guinier, 54011 Nancy, France

+33 3 72 74 25 96
Smagul KARAZHANOVInstitute for Energy Technology

Instituttveien 18, 2027 Kjeller, Norway

+47 45163599