2014 Fall Meeting
MATERIALS FOR OPTICS AND OPTOELECTRONICSC
Inorganic nanoarchitectonics : from design and fabrication to sustainable solutions
Nanoarchitectonics is a novel paradigm in nanotechnology aimed at designed assembling of nanoscaled structural units and elaborating strategies for achieving a versatile functionality through their controlled assemblies into higher dimensions. In these perspectives, inorganic nanoarchitectonics can trigger innovation and give sustainable solutions in nanocatalysis, nanoelectronics, nanomedicine, light-energy conversion and not only.
Construction of inorganic materials based on the concept of nanoarchitectonics give rise to powerful means to develop materials with complex functionalities, able to trigger innovative solutions in many fields. In this perspective, research on the exploration of the key features of inorganic nanoarchitectonics and further, how these can be used for obtaining novel, useful and clean technologies, might play a critically important role in developing a sustainable future. To address these issues, this symposium will cover general topics of inorganic nanostructures manufacturing, organization and elaborating techniques and strategies for their assembly into higher dimensions for giving rise to more complex architectures. Fundamental issues related to assembling and organizing at nanoscale, critically influence the functionalities and applications of inorganic nanostructures will be also included.
Specifically, this symposium will focus on:
- manufacturing of inorganic nanostructures and strategies to manipulate their nanoarchitectonics
- characterizations of inorganic nano-assemblies and emergence of collective behaviours and multifunctionality through inorganic nanoarchitectonics
- inorganic nanoarchitectonics for heterogeneous (photo)catalysis applications
- inorganic nanoarchitectonics for biomedical applications
- interfacial inorganic nanoarchitectonics.
To meet the challenge, researchers with diverse backgrounds need to work closely together across different disciplines. The symposium will contribute to spread the knowledge in nanoarchitectonics of inorganic materials by providing a platform for materials scientists, chemists, physicists and engineers, involved in fundamental, as well in applied research, to communicate their vision and the latest exciting new results.
Hot topics to be covered by the symposium (but is not limited):
- TiO2 and MeNPs/TiO2 nanoarchitectonics: from design to enhanced photocatalytic efficiency.
- Nanoarchitetonics based on graphene and 2-D layered oxides, nitrides and sulfides.
- Plasmonic metal nanoparticles (MeNPs) nanoarchitectonics.
- Layered double hydroxides nanoarchitectonics.
- Mesoporous inorganic nanoarchitectonics.
- Nanoarchitectonics of nanodiamonds.
- Inorganic nanoarchitectonics for photocatalytic water splitting, photocatalytic CO2 fixation and energy storage.
- Multifunctional inorganic nanoarchitectonics for application in green chemistry
- Inorganic nanoarchitectonics for drug delivery and functional biomaterials
- Inorganic nanoarchitectonics for application in nanoelectronics and nanophotonics
List of invited speakers:
- Jiefang Zhu, Uppsala University, Sweden
- Min Wei, University of Chemical Technology, Beijing, P. R. China
- Testuro Majima, University of Osaka, Japan
- James Durrant, Imperial College, London
- Paolo Fornasiero, University of Trieste, Italy
- Valérie Keller, University of Strasbourg, France
- Guido Mül, University of Twente, The Netherlands
- Jorge Gascón, University of Delft, The Netherlands
List of scientific committee members:
- Eduardo Ruiz-Hitzky, Materials Science Institute of Madrid, Spain
- Raffaele Molinari, University of Calabria, Italy
- Valerie Keller, University of Strasbourg, France
- Nobuhiro Matsushita, Tokyo Institute of Technology, Japan
- Rune Lødeng, SINTEF, Norway
- Kazunori Takada, National Institute for Materials Science, Japan
- Katsuhiko Ariga, World Premier International (WPI), Research Center for Materials Nanoarchitectonics (MANA), Japan
- Magnus Rønning Norwegian University of Science and Technology, Norway
- Yusuke Yamauchi, National Institute for Materials Science (NIMS), Japan
- Barbara Malič, Jozef Stefan Institute, Slovenia
- Dragos Ciuparu, Petrol – Gaze University Ploiesti, Romania
- Vicente Rives, University of Salamanca, Spain
- Mateo Cargnello, University of Pennsylvania, USA
- Maria Dinescu, National Institute for Lasers, Plasma and Radiation Physics, Romania
- David Evans, University of Chemical Technology, P. R. China
- Yasuo Izumi, Chiba University, Japan
- Jaime S. Valente, Mexican Petroleum Institute, Mexico
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Inorganic Nanoarchitectonics : Hermenegildo Garcia
Authors : Andreas Kafizas (Imperial), Raul Q. Cabrera (UCL), Carlos S. Vazquez (UCL), Ivan P. Parkin (UCL) and James R. Durrant (Imperial)
Affiliations : Imperial College London, South Kensington Campus, Department of Chemistry, London, SW7 2AZ University College London, Department of Chemistry, 20 Gordon Street, London, WC1H 0AJ
Resume : Solar driven H2 synthesis from water could hold the key to virtually unlimited clean energy production. This talk addresses the need to understand the mechanism of charge transfer in the most promising inorganic heterojunction nanostructure devices used in the solar driven H2 synthesis from water. Recent research, including our own transient kinetic studies, has made it clear that inorganic heterojunctions are of key interest to achieve high efficiency in H2 generation. In this talk we will discuss the anatase TiO2/ rutile TiO2 heterojunction system, which is one of the most important heterojunction systems in this field made highly popular by the high photocatalytic activity of Degussa P25 TiO2. The nanostructures were grown using chemical vapour deposition; a technique that can create high quality interfaces and is also a low-cost and up-scalable process. The heterojunctions were characterised using transient absorption spectroscopy a unique method that allows us to determine the dynamics and kinetics of charge transfer processes. The transient absorption spectroscopy method will be explained and the implications of the kinetic studies on the materials function in water photolysis will be discussed.
Authors : A.Duta, A. Enesca, L. Isac, D. Perniu
Affiliations : Transilvania University of Brasov, Eroilor 29, 500036 Brasov, Romania, R&D Centre: Renewable Energy Systems and Recycling
Resume : To extend the UV response of TiO2 photocatalyst towards Vis, several paths are already established including anion (and possible cation) doping, metal NP association, etc. The paper discusses another route that exploits the advantages of n-p junctions, developed between TiO2 photocatalyst coupled with p-type CuxS. Bi-layered thin films of n-p photocatalysts and multi-layered structures are further analysed, detailing the main design principles based on energy bands alignment. Further on, the importance of the working conditions is outlined, allowing the selection of the favorable pH window that supports: (1) to get enhanced electrostatic attraction substrate ? pollutant, and (2) the choice of the electrochemical potential of the oxidant species, according to the substrate?s band energy system. This design concept is discussed for the TiO2/CuxS and the TiO2/CuxS, CuO/SnO2 tandem structures, which were further obtained by sequential spray pyrolysis deposition. The experimental results prove the importance of the crystallinity and morpohology control of each layer and of the entire assembly, to reach an optimal charge carriers flow and to limit recombinations. The concept is validated based on the results obtained in investigating the tandems as photocatalysts under simulated solar radiation (85% Vis 15%UV) for the methylene blue decomposition. The results show that bleaching efficiency is very good and mineralization reaches (in optimized conditions) over 70% after 360 h.
Authors : Chittaranjan Das, Massimo Tallarida, and Dieter Schmeisser
Affiliations : Department of Applied physics and Sensors Brandenburg University of Technology, Cottbus-Senftenberg , Germany
Resume : Photo-electrochemical (PEC) water splitting is one of the most emerging fields for green energy generation and storage. For efficient PEC devices two efficient and stable photoelectrodes are needed. n-type Si can be used as photoanode but it suffers of surface oxidation and has an unfavorable band edge position for oxygen evolution; p-type Si can be instead used as photocathode, it has a favorable band edge position for hydrogen evolution. Although the p-type Si is considerably more stable against photo oxidation than the n-type, it has a low quantum yield (QY). Also its high reflectance is typically an issue. The QY of p-type Si can be increased by surface modification, e.g. using a catalyst. Reflectance can be reduced by surface structuring. In the present work we show a study of microstructured Si covered by a TiO2 layer and nano-islands. The microstructures are prepared by Galvanostatic selective etching of Si in HF medium. The TiO2 layer was deposited by atomic layer deposition (ALD) to protect the microstructured photocathode against corrosion. The microstructured TiO2/Si were decorated with TiO2 nano islands using a modified ALD technique to enhance the absorption of light in the photocathode. The obtained microstructured photocathode showed a shift in onset potential of 300mV towards anodic direction as compared to bare Si.
Authors : Seongsoo Park, Sungho Choi, Ha-Kyun Jung
Affiliations : Korea Research Institute of Chemical Technology, Seoul, South Korea
Resume : In general, white LEDs are fabricated by combination of a yellow phosphor and a blue LED based on GaN. In order to improve the efficiency of phosphor-converted LED (pc-LED), to use the appropriate phosphors is important. At fabricating a pc-LED, the mixture of phosphors and encapsulant is coated on the LED chip. Small particle size, narrow size distribution and spherical shape of the phosphor particles can provide better mixing with encapsulant in the fabrication of pc-LED. Ce3+-activated yttrium aluminum garnet Y3Al5O12:Ce3+ (YAG:Ce3+) has been known to be efficient for converting the blue emission by LED into yellow light. In this work, one-pot solution process using the hydrolysis reaction of urea with a dispersant was designed to synthesize YAG:Ce nanospheres. In the reaction, the used solvent was a mixed solution of alcohol and water. As a precipitant for co-precipitation of Y3+, Al3+ and Ce3+ metal ion components, excess urea was used. The volume ratio of alcohol to water and the concentration of metal ions, dispersant (Hydoroxy propyl cellulose) and urea were optimized based on the morphology and the emission intensity of the nanospheres. Several tens to 500 nm of YAG nanospheres were prepared with the changes of synthetic conditions. The optimum ratio of the alcohol/water mixture was around 5. The XRD study indicated that the single phase of yttrium aluminum garnet is formed with firing at 900℃ without the formation of intermediate phases such as YAlO3 (YAP) and Y4A
Authors : C. Thanachayanont*, C. Junin*, C. Photiphitak*, B. Chayasombat*, B. Shollock**, D. Proprentner***
Affiliations : * National Metal and Materials Technology Center, Thailand Science Park, Klong 1, Klong Luang, Pathumthani 12120 Thailand; ** WMG, University of Warwick, Coventry, CV4 7AL, UK; *** Faculty of Engineering, Department of materials, Royal School of Mines, South Kensington SW7 2AZ, UK
Resume : Silver nanoparticles (AgNPs) decorated on TiO2 photoelectro-catalytic thin films were prepared by immersion of AgNO3 under UV irradiation. Prior to the immersion, the TiO2 films were prepared by dip-coating, spray-coating and screen-printing techniques. Using Focus Ion Beam (FIB) and Field Emission Scanning Electron Microscope (FE-SEM), AgNPs were found to evenly distribute in the TiO2 films with narrow size distribution of around 20 nm. Photoelectro-catalytic activities of all the TiO2 films decorated with the AgNPs were tested with methylene blue and textile wastewater effluents and compared.
Authors : V. P. Krasovskyy, Yu.V. Naidich, E. P. Chernigovtsev, N. A. Krasovskaya
Affiliations : Frantsevitch Institute for Problems of Materials Science of NASU 3, Krzhyzhanovsky str., 03142, Kyiv, Ukraine; E-mail: email@example.com
Resume : The low wetting by aluminum melt of solid nonmetallic phases is a significant problem at reception of composite materials on the basis of a Almatrix reinforced by oxide, basalt, carbon and other fibres, by a free spontaneous impregnation method, and at the soldering of nonmetallic materials by aluminum solders. The dense Al2O3film on a surface of metal is the reason of bad wetting. Special methods of capillary purification of the surface of aluminum alloy, the substantial increase of temperature of the soldering or impregnation (the last is possibly only in some cases), and also drawing of metal coatings are giving the limited effect (exception a Nifilm). The wetting (sessile drop method) of many nonmetallic materials (Al2O3, SiO2, SiC, CaF2, basalt, graphite and others), on surfaces of which the nickel coating (thickness of 150400 nm) is put, is investigated. The high degree of wetting (the contact angle makes 2050°) at temperature 700 °C is observed. It is explained that similar is wetted similar, and also in system Al/Ni the exothermic reaction with intermetalles formation takes place. Reaction is accompanied by rise in temperature (strong, local, small time of action), by dispersion, and evaporation and, it is possible, is by result of formation of pure contact between a solid phase and liquid aluminum. This effect for receipt oxide ceramics soldering joining and manufacturing of composite material Al/basalt fibres is used.
Authors : Jung Eun Lee, Min Hyung Lee
Affiliations : Department of Applied Chemistry, Kyung Hee University
Resume : 2D layered materials such as MoS2 and WS2 have received much attention as alternatives to Pt for hydrogen evolution reaction (HER) catalysts. Here, we synthesized several types of MoS2/rGO hybrid catalysts with tunable size and morphology by controlling amount of graphene oxide during solvothermal synthesis of MoS2. Catalytic performance of MoS2/rGO for HER depended on surface area of catalytically active edge site of MoS2. Also, we studied correlation of catalytic performance and crystallinity of MoS2 after annealing of each MoS2/rGO catalyst.
Authors : Cristina Bogatu, Dana Perniu, Anca Duta
Affiliations : Transilvania University of Brasov, R&D Centre Renewable Energy systems and Recycling, Romania
Resume : TiO2 nanoparticles are widely used as powder, thin films or dispersions, in a broad field of photocatalysis applications like wastewater treatment, self-cleaning,etc. In special applications (chemical weapon decontamination) the development of TiO2 photocatalytic inks represents an alternative, if certain stability of the nano-particles disperse system is reached. In a continuous medium the nanoparticles naturally tend to agglomerate and deposit driven by the van der Waals and electrostatic forces. The stability remains a key problem in designing proper dispersions for specific applications. In this study, TiO2 Degussa P25 dispersions were obtained in aqueous, alcoholic or water:alcohol solvent. The influence of the suspensions concentration, the solvent, pH and the surfactant (STA)/polymer addition on the dispersion stability was studied. Based on the double layer and DLVO theories, a stabilization mechanism is proposed, considering the steric effect of STA/polyvinylpyrrolidone adsorbed at the particles/liquid interface with formation of stabilized architectural structures and the double layer formation/modification and charge in the presence of alcohol. The dispersions photocatalytic activity was tested on methylorange, after the deposition on glass/textile substrates via spraying at room temperature. Correlations on the film stability-morphologyphotocatalytic activity were discussed considering the interactions between the dispersions components and dispersionsubstrate.
Authors : C. Bazioti1, N. Kalfagiannis2, G. Vourlias1, A. Siozios3, M. Cranton2,4, E. Lidorikis3, D. Koutsogeorgis2, G.P. Dimitrakopulos1, and P. Patsalas1
Affiliations : 1 Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; 2 School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, UK; 3 Department of Materials Science and Engineering, Univ. of Ioannina, Ioannina, GR-45110, Greece; 4 Faculty of Arts, Computing, Engineering & Sciences at Sheffield Hallam University, S1 1WB, UK
Resume : Ag:AlN nanocomposites have been shown to exhibit plasmonic behavior making them suitable for a range of applications. We explored structurally the photo-modulation of the nanoarchitecture of multilayered nanocomposites. Stratified composites of Ag nanoparticles (NPs) were deposited on Si substrates by magnetron sputtering. Both amorphous AlN (a-AlN) and wurtzite AlN (w-AlN) matrices were employed. The multilayers were then processed by laser annealing (LA) in order to promote ripening of embedded NPs. The effect of LA was assessed through structural characterization performed by TEM/HRTEM and XRD. It was found that LA led to a grading of NP size through partial dissolution of NP layers. w-AlN appears to constrain the phenomenon compared to a-AlN. De-stratification was promoted by LA under pressure. The NPs retained their average spherical shape and became better separated through ripening. HRTEM showed a local crystallization of a-AlN by LA. Optical reflectivity measurements confirmed the improved optical response due to enhanced localized surface plasmon resonance after LA. Structural features were quantified by peak profile analysis, which identified the variation of Ag NP size vs LA conditions. Acknowledgement: Research funded from the EU (ESF) and Greek national funds through the Research Funding Program: Heracleitus II (A. Siozios) and from the People Programme (MC Actions) LASER-PLASMON (FP7/2007-2013) under REA grant agreement PIEF-GA-2012-330444 (N. Kalfagiannis).
Authors : Luís Pinho1, Chrysi Kapridaki2, Maria J. Mosquera1*, Pagona Maravelaki-Kalaitzaki2*
Affiliations : 1TEP-243 NanomaterialsGroup, Departamento de Química-Física, Facultad de Ciencias, Campus Universitario Río San Pedro, Universidad de Cádiz, 11510 Puerto Real, Cádiz, Spain.Tel: + 34 956 016331; Fax: + 34 956 016471; E-mail: firstname.lastname@example.org, email@example.com 2 School of Architectural Engineering, Technical University of Crete, Akrotiri University Campus, 73100 Chania, Crete, Greece. Tel: +30 2821037661; Fax: +30 2821037841; E-mail: firstname.lastname@example.org, email@example.com
Resume : This work deals with the design of a low energetic demanded and simple synthesis route for producing SiO2-crystalline-TiO2 nanocomposites at ambient temperature. The as-prepared nanocomposites are designed to provide self-cleaning activities, along with the ability to strengthen and protect the building substrates. The SiO2-crystalline-TiO2 self-cleaning nanocomposites are obtained by mixing titanium and silicon alkoxides in the presence of oxalic acid. An organosilane was also added in order to provide hydrophobic properties through the reduction of the surface energy. The designed nanocomposites differed in the concentration of the oxalic acid. In the proposed synthesis route, the oxalic acid acts as: (a) a hole-scavenger during the photocatalytic process; (b) a sol-gel catalyst; (c) a chelating agent of the titanium precursor; (d) an increasing agent of the gel time of the nanomaterial and finally, (e) it contributes to the formation of anatase crystals at ambient temperature through a peptization process. The nanostructure and the chemical bonds formed proved that the formation of the independent domains of anatase crystals inside the silica matrix was essential for improving the photocatalytic properties of the nanocomposites. The nanocomposites were assessed on marbles and limestones as protective and strengthening agents; they exhibit self-cleaning and hydrophobic properties and are able to reinforce the microstructure of the examined lithic substrates.
Authors : Alexandru Mihai Grumezescu1, Oana Fufa2, Ecaterina Andronescu1, Valentina Grumezescu 1,3,*, Alina Maria Holban 1,4, Laurențiu Mogoantă5, George Dan Mogoșanu6, Alexandra Elena Oprea1, Gabriel Socol3, Florin Iordache7
Affiliations : 1Department of Science and Engineering of Oxidic Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 17 Polizu Street, 011061 Bucharest, Romania 2Department of Biomaterials and Medical Devices, Faculty of Medical Engineering, University Politehnica of Bucharest, Polizu Street, No 1-7, RO-011061m Bucharest, Romania 3Lasers Department, National Institute for Lasers, Plasma & Radiation Physics, P.O. Box MG-36, Magurele, Bucharest, Romania 4Microbiology Immunology Department, Faculty of Biology, University of Bucharest, 13 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania 4Department of Biomaterials and Medical Devices, Faculty of Medical Engineering, University Politehnica of Bucharest, Polizu Street, No 1-7, RO-011061m Bucharest, Romania 5 Research Center for Microscopic Morphology and Immunology, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 6 Department of Pharmacognosy & Phytotherapy, Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 7Institute of Cellular Biology and Pathology of Romanian Academy, Nicolae Simionescu, Department of Fetal and Adult Stem Cell Therapy, 8, B.P. Hasdeu, Bucharest 050568, Romania
Resume : Because of their direct contact with the external and internal environment, one of the main risk occurred in patients with feeding tubes is the high rate of infection. As device associated infections are difficult to treat health threatening conditions, novel approaches for reducing the incidence of infections in prosthetised patients are needed. The purpose of this study was to prepare and assess the biological effect of silver/sodium oleate nanostructures deposited as thin films through matrix assisted pulsed laser evaporation (MAPLE) on the surface of gastrastomy (G) tubes in order to increase their resistance to microbial contamination. Silver nanoparticles coated with sodium oleate (NanoSilver) were prepared by a simple wet chemical route and characterized by FT-IR, DTA-TG, TEM, SAED and EDS. After the primary characterization, the prepared nanopowder was used to create a thin uniform surface by advanced laser processing in order to obtain G tubes with high resistance to microbial colonization and biofilm development. The prepared surfaces were characterized by SEM, TEM, IR Microscopy, XRD, in vitro and in vivo biological activity was assessed. In vitro results demonstrate that the prepared nano-silver coatings have improved resistance to both Gram-positive and Gram-negative bacteria colonization and interfere with biofilms formation. On the other hand, these coatings have no citotoxic effect on human cultured cells, allowing their normal growth and development. In vivo experiments demonstrated that the nanoparticle solution used for the preparation of coated G tubes have no pathologic impact on treated mice. These nanoparticles are completely eliminated from the body in few days, after 2 weeks the only anatomical place that was positive for their presence being the spleen. According to our results, the NanoSilver coatings have a remarkable potential to be used in creating customized surfaces for different catheters and medical tubes with a low risk of infection.
Authors : Vlad Mihaela1, Alina Maria Holban 1,2, Ecaterina Andronescu1, Valentina Grumezescu 1,3,*, Raluca Meștercă4, Eliza Tote4, Laurențiu Mogoantă5, George Dan Mogoșanu6, Alexandra Elena Oprea1, Alexandru Mihai Grumezescu1, Gabriel Socol3, Florin Iordache7
Affiliations : 1Department of Science and Engineering of Oxidic Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 17 Polizu Street, 011061 Bucharest, Romania 2Microbiology Immunology Department, Faculty of Biology, University of Bucharest, 13 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania 3Lasers Department, National Institute for Lasers, Plasma & Radiation Physics, P.O. Box MG-36, Magurele, Bucharest, Romania 4Department of Biomaterials and Medical Devices, Faculty of Medical Engineering, University Politehnica of Bucharest, Polizu Street, No 1-7, RO-011061m Bucharest, Romania 5 Research Center for Microscopic Morphology and Immunology, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 6 Department of Pharmacognosy & Phytotherapy, Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 7Institute of Cellular Biology and Pathology of Romanian Academy, Nicolae Simionescu, Department of Fetal and Adult Stem Cell Therapy, 8, B.P. Hasdeu, Bucharest 050568, Romania
Resume : In this study, we report the synthesis and characterization of newly prepared thin magnetic coatings deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) to be used as antimicrobial surfaces for medical purpose. The magnetite nanoparticles were prepared by co-precipitation method. Silica was generated from TEOS and CTAB as a coating agent on the surface of magnetite. Prepared magnetite@silica was calcinated for 24 h at 650 oC in order to eliminate the CTAB template and to create a new nanoarhitectonics. Tetracycline was entrapped into 10 nm iron oxide@silica structure and further used for preparation of thin coatings. The obtained surfaces were characterized by SEM, TEM, IR and XRD. In order to establish the biologic effect of the obtained material we realized we in vitro tests on eukaryotic and prokaryotic cells and in vivo assays using a mice model treated for up to 14 days with the prepared nanostructures. The anti-microbial adherence properties were tested for up to 3 days and the results recommend this newly prepared coating to prevent Gram-positive and Gram-negative attachment and biofilm development on different medical surfaces. The biodistribution of these nanoarhitectonics revealed that they are well tolerated and eliminated by the host organisms, after 14 days the structures being presented only in spleen of tested mice. The results proved that the prepared surface based on iron oxide, silica network and tetracycline deposited by advanced laser technique can be used without any impediments to improve the resistance to colonization of medical devices.
Authors : Vlad Mihaela1, Alina Maria Holban 1,2, Ecaterina Andronescu1, Valentina Grumezescu 1,3, Alexandra Elena Oprea1, Laurențiu Mogoantă4, George Dan Mogoșanu5, Alexandru Mihai Grumezescu1, Gabriel Socol3, Florin Iordache6
Affiliations : 1Department of Science and Engineering of Oxidic Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 17 Polizu Street, 011061 Bucharest, Romania 2Microbiology Immunology Department, Faculty of Biology, University of Bucharest, 13 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania 3Lasers Department, National Institute for Lasers, Plasma & Radiation Physics, P.O. Box MG-36, Magurele, Bucharest, Romania 4 Research Center for Microscopic Morphology and Immunology, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 5 Department of Pharmacognosy & Phytotherapy, Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 6Institute of Cellular Biology and Pathology of Romanian Academy, Nicolae Simionescu, Department of Fetal and Adult Stem Cell Therapy, 8, B.P. Hasdeu, Bucharest 050568, Romania
Resume : The aim of this study was to prepare a novel bioactive medical surface in order to prevent microbial contamination and biofilm formation. For this purpose, Cobalt ferrite was prepared by co-precipitation in basic aqueous solution. Silica was applied as a shell from TEOS and CTAB in order to create a nanoarchitectonics. Prepared nanostructure was calcinated for 24 h at 650 oC to remove the template and create a well-ordered nanostructure. Cobalt ferrite@silica/streptomycin was used to prepare a novel surface by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. Prepared thin coatings were characterized by Scanning Electron Microscopy, Infrared Microscopy and Transmission Electron Microscopy. Time lap in vitro drug release and different biological assays were also performed. The results demonstrated that the obtained thin coated surfaces ensures the controlled release of the active antimicrobial agent and inhibits bacterial colonization and development. Furthermore, experiments performed on human cultured endothelial cells demonstrated that eukaryote cells have a normal morphology and growth rate when cultivated on these surfaces and they do not interfere with any cellular process. In vivo results performed in mouse models also revealed that these nanoparticles tend to agglomerate in intensively blood irrigated organs and cause a low immune response, which is normal for any situation when a foreign material is introduced in the body. After less than two weeks, all organs ale cleared from the tested nanoparticles, they being still persistent in low amounts in spleen only. . Our results have demonstrated that the cobalt ferrite@silica/streptomycin bioactive coatings have significantly inhibited the microbial development on the coated surfaces, and manifested a great in vitro and in vivo biocompatibility.
Authors : Matilte Halma, Christine Mousty, Claude Forano, Martine Sancelme, Pascale Besse-Hoggan, Vanessa Prevot
Affiliations : Clermont Université, Université Blaise Pascal, ICCF, BP 10448, F-63000 Clermont-Ferrand, France, CNRS, UMR 6296, BP 80026, F-63177 Aubière, France
Resume : Bio-hybrid materials, based on immobilisation of bacteria in organic or inorganic matrices, are crucial for biotechnology uses. These living materials present several applications such as catalysts for environmental bioremediation, optical and electrochemical sensors (1-3). Atrazine, a broad-leaf weed control herbicide is mainly used in agriculture (3). Pseudomonas sp. strain ADP (ADP) is the best-characterized bacteria able to mineralize the herbicide atrazine to CO2 and ammonia (3). A soft chemical process was successfully used to immobilize ADP within a Mg2Al- layered double hydroxide (LDH) host matrix. This approach is based on a simple, quick and ecofriendly direct coprecipitation of metal salt in the presence of a colloidal suspension of bacteria in water. It must be stressed that the ratio between biological and inorganic components was easily tuned and influence the biological activity of the bacteria toward atrazine degradation. The cell viability and growth and the conservation of the biological activity were studied. An enhanced atrazine degradation rate was achieved by immobilized bacteria compared to free cells for an optimized ADP/LDH ratio. Moreover the biohybrid material maintains the same biological activity after four cycles of reutilization and allows the cells to further grow. This synthetic approach could be readily extended to other whole-cell immobilization of interest for new developments in biotechnological systems  P. Besse-Hoggan, T. Alekseeva, M. Sancelme, A.-M. Delort and C. Forano, Environ. Pollut., 2009, 157, 2837.  T. Alekseeva, V. Prevot, M. Sancelme, C. Forano and P. Besse-Hoggan, J. Hazard. Mater., 2011, 191, 126-135.
Authors : Alina Maria Holban1,2, Valentina Grumezescu1,3,*, Ecaterina Andronescu1, Alexandru Mihai Grumezescu1, Laurențiu Mogoantă4, George Dan Mogoșanu5, Gabriel Socol3, Florin Iordache6, Veronica Lazar1
Affiliations : 1Department of Science and Engineering of Oxidic Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 17 Polizu Street, 011061 Bucharest, Romania 2Microbiology Immunology Department, Faculty of Biology, University of Bucharest, 13 Portocalilor Lane, Sector 5, 77206 Bucharest, Romania 3Lasers Department, National Institute for Lasers, Plasma & Radiation Physics, P.O. Box MG-36, Magurele, Bucharest, Romania 4 Research Center for Microscopic Morphology and Immunology, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 5Department of Pharmacognosy & Phytotherapy, Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova, 2 Petru Rareş Street, 200349 Craiova, Romania 6Institute of Cellular Biology and Pathology of Romanian Academy, Nicolae Simionescu, Department of Fetal and Adult Stem Cell Therapy, 8, B.P. Hasdeu, Bucharest 050568, Romania
Resume : With the increased rates of antimicrobial resistant bacterial infections, researchers strive to find alternative methods to limit their spread. In the hospital environment are found the highest multiresistance rates, which result in severe infections affecting mainly intensive care patients and individuals with implanted medical devices. The purpose of this study was to optimize the surface of wide use medical devices with antimicrobial ZnO@silica/erytromycin nanoparticles prepared by matrix assisted pulsed laser evaporation (MAPLE) in order to improve the resistance of medical surfaces to microbial colonization and biofilm formation. The nanoarchitectonics was prepared by Sol-gel method and further subjected to calcination. The functionalized surfaces, ZnO@silica/erytromycin, were characterized by Infrared microscopy, Scanning electron microscopy and High-Resolution Transmision Electron Microscopy, and in vitro / in vivo tests were also performed to establish their biological activity. Their anti-infectious potential was established by evatuating microbial adherence and biofilm formation on the modified surfaces. The microbiological assays proved that MAPLE deposed ZnO@silica/erytrhomycin inhibited the adherence capacity and biofilm development of all tested Gram-positive and Gram-negative bacterial strains, by ensuring a perfect controlled release of the active drug, erytrhomycin. Furthermore, qualitative and quantitative analyses demonstrated that the prepared nanoarchitectonics have a good biocompatibility, allowing the normal growth and metabolism progression on cultured human endothelial cells. In vivo assay, using a balbC mouse model demonstrated that immediately after the injection of the nanoparticles suspension prepared for the MAPLE deposition, a normal inflammatory infiltrate can be observed and the injected nanoparticles tend to aggregate within the well blood irrigated organs (liver, spleen and lungs). However, after 7 days post-treatment all organs are cleared from nanoparticles, excepting the spleen, where small amounts of nanoparticles are still present.
Authors : árka Pauová, Josef Krýsa, Jaromír Jirkovský, Gilles Mailhot, Vanessa Prevot
Affiliations : Clermont Université, Université Blaise Pascal, ICCF, BP 10448, F-63000 Clermont-Ferrand, France, CNRS, UMR 6296, BP 80026, F-63177 Aubière, France Institute of Chemical Technology Prague, Technická 5, 166 28 Prague, Czech Republic J. Heyrovský Institute of Physical Chemistry, Dolejkova 3, 182 23 Prague, Czech Republic
Resume : TiO2 colloidal particles have been in recent years extensively used in the photocatalytic oxidation of organic compounds in water, because of their low cost, reduced toxicity and high chemical stability. The assembly of nanosized TiO2 onto porous solids represents a topic largely studied with the aims to develop supported heterogeneous catalysts. The nanocomposites then formed, often display large specific area, porosity and high adsorption capacity. These nanoparticle-immobilized solids are of great interest in the study of photocatalytic reactions for the recovery of catalyst and for limiting the TiO2 nanoparticles aggregation. In this work, new inorganic-inorganic nanocomposite particles based on Layered Double Hydroxides (LDH) associated to titanium dioxide has been prepared. LDH are lamellar solids showing interesting chemical variability, anion exchange capacity and adsorption properties. The LDH/TiO2 nanocomposites were successfully prepared by spray drying starting from a mixture of two colloidal suspensions of both TiO2 and LDH nanoparticles. The characterization of the spherical nanocomposite particles as prepared and their photocatalytic activity toward Orange II degradation used as a model organic dye molecule will be presented and discussed. For comparison, the photocatalytic activity of both acidic and basic TiO2 was also measured.
Authors : Karol Miszta1, Rosaria Brescia1, Mirko Prato1, Giovanni Bertoni1,2, Sergio Marras1, Yi Xie1, Mee Rahn Kim1 and Liberato Manna1*
Affiliations : 1 Department of Nanochemistry, Istituto Italiano di Tecnologia (IIT), via Morego, 30, 16163 Genova, Italy 2 IMEM-CNR, Parco Area delle Scienze 37/A, IT 43124 Parma, Italy
Resume : Hollow and concave nanocrystals find applications in many fields and their fabrication can follow different possible mechanisms. We report a new route to these nanostructures exploiting the oxidation of Cu2-xSe/Cu2-xS core/shell nanocrystals with various etchants. Even though the Cu2-xSe core is encased in a thick Cu2-xS shell, the initial effect of oxidation is the creation of a void in the core. This is rationalized in terms of diffusion of Cu+ ions and electrons from the core to the shell (and from there to the solution). Differently from the classical Kirkendall effect, which entails an unbalance between in-diffusion and out-diffusion of two different species across an interface, the present mechanism can be considered as limit case of such effect and is triggered by the stronger tendency of Cu2-xSe over Cu2-xS to oxidation and by fast Cu+ diffusion in copper chalcogenides. As the oxidation progresses, expansion of the inner void erodes the entire Cu2-xSe core, accompanied by etching and partial collapse of the shell, yielding Cu2-xSySe1-y concave particles. KEYWORDS: hollow nanoparticles, cation exchange, plasmonic materials, copper chalcogenides
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Inorganic Nanoarchitectonics : Vanessa Prevot
Authors : Frank Szmulowicz(1), Kurt G. Eyink(2), Krishnamurthy Mahalingam(2), Lawrence Grazulis(1), Elizabeth H. Steenbergen(2), David Esposito(2), Andrew Aronow(2), Joseph Massengale(2), Murray Hill(2), Luke J. Bissell and V. Pustovits(2)
Affiliations : (1) Univ. of Dayton Research Institute, Dayton, Ohio 45469-0072, USA (2) AFRL/RXAN, Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Dayton, OH, 45433-7707, USA
Resume : Enhanced optical absorption and emission properties compared to normal quantum dots are expected from metal nanoparticle-quantum dot complexes. Typically these complexes are formed from colloidal particles tethered together using ligands. Here we have formed these complexes using molecular beam epitaxy. In particular, we have coupled ErAs semimetal nanoparticles to InAs quantum dots in a GaAs host. Preliminary calculations show the potential for an optical field enhancement factor as large a 100. We have made stacks of these ErAs-InAs complexes with a GaAs spacer layer thickness that was varied from 8 nm to 40 nm. TEM and XRD show these structures to be high quality. Photoluminescence and spectroscopic ellipsometry were used to study the optical properties as a function of the GaAs spacing layer thickness. We found that PL intensity decreases as the spacer layer thickness decreases. The spectroscopic ellipsometry data shows that the complexes have metal-dielectric stack characteristics.
Authors : Thomas Cottineau, Michel Roux, Jean-Luc Rehspringer, Nicolas Keller, Valérie Keller.
Affiliations : ICPEES-Institute of Chemistry and Processes for Energy, Environment and Health CNRS/University of Strasbourg 25, rue Becquerel 67087 Strasbourg cedex
Resume : The patient number world-wide concerned ranges from 200,000 when considering only a class of rare diseases such as retinitis pigmentosa, to several millions, when including only part of those affected with age-related macular degeneration. This confers a first-order societal interest to this research area. The retinal prosthesis concept with external electrical stimulation of partially-persistent neuronal network has been implemented so far with implanted parts located both inside and outside of the eyeball, for authorizing information and/or energy transfer to the electrodes. Even if clinical trials validated the concept, with restoration of some visual perception to implanted patients, models tested till now do not allow for a useful vision, i.e. for assuring motion autonomy, face recognition and reading ability (beyond large letter recognition). Our strategy would lead to single implantation of a photoreceptive matrix inside eyeball, with no need of passing a cable through the eye wall. Originality and novelty turn are based on the use of a semi-conductor material made of TiO2 single oxide, nanostructured as pixellized vertically aligned nanotubes architecture, obtained by electrochemical anodic synthesis, and carefully modified for transferring its light absorption to the visible range and thus obtaining an architecturized material photoresponsive to visible light stimulation. We aim to develop a new kind of artificial retina containing pixellized architectures of vertically aligned TiO2-based nanotubes, acting as artificial photoreceptors in replacement of degenerated natural ones, when the smart neuronal network of retina is partially maintained. This approach benefits from the photosensitive properties of TiO2 allowing to combine photoresponse and neuronal stimulation inside a unique sensor. TiO2 can easily be synthesized as films. Furthermore, this approach benefits from aligned TiO2 nanotubes architectures in terms of light capture and photogenerated electron transport properties for enhancing the neuronal response. The photoresponse of the vertically aligned TiO2 nanotubes architectures have been obtained implementing electrophysiological experiments in a patch-clamp configuration with different irradiation conditions (wavelength, frequency...). The influence of both TiO2 nanotubes length and thickness of an additional gold nanoparticle top-layer has also been studies. First results were very promising for use in retinal prosthesis application. Indeed, a strong spatial localization of the photoresponse was obtained under illumination at the surface of the architecturized TiO2 nanotubes photosensors, and trans-membranar polarization was observed for neuroblastome-like cells cultured at the photosensor surface. Furthermore, series of action potentials, issued from ganglionic cells of complete rat retinas applied on the architecturized photosensor, have been recorded in a reproducible way. Different strategies aiming at the improvement of the photoresponse in the visible part of the light ─ like cationic/anionic co-doping and decoration by metal nanoparticles inducing plasmomic effects ─ have been carried out and will be discussed. The authors are grateful to the Region Alsace, OSEO and ANR funding.
Inorganic Nanoarchitectonics : Gabriela Carja
Authors : J.E. ten Elshof
Affiliations : University of Twente, MESA+ Institute for Nanotechnology, P.O. Box 217, 7500 AE Enschede, the Netherlands
Resume : Two-dimensional oxide nanosheets can be used to locally control the nucleation and growth direction of functional perovskite-type films deposited by pulsed laser deposition (PLD), thereby tuning the film properties. Oxide nanosheets are the oxide equivalents of graphene. They have a thickness of ~1 nm and can have lateral sizes up to tens of micrometers. They are made by exfoliation of layered oxides in aqueous solution. We studied the mechanism of exfoliation and restacking of lepidocrocite-type titanates into Ti0.87O2 nanosheets in solution by small angle x-ray scattering. The resulting colloidal solution of nanosheets can be used for the formation of nanosheet monolayers with >99% coverage on arbitrary substrates via Langmuir-Blodgett deposition. These monolayers have a very well-defined crystal termination, which can serve as nucleation plane for subsequent film deposition. SrRuO3 films were grown on Ca2Nb3O10 and Ti0.87O2 nanosheet films by PLD. SrRuO3 is ferromagnetic below 160 K and shows strong magnetic anisotropy. Depending on the nature of the seed layer,  oriented films grew on Ca2Nb3O10, and  oriented films on Ti0.87O2. The influence of the seed layer on magnetization and Curie temperature is discussed. Also micropatterning of the nanosheets by photolithography and lift-off is demonstrated. Alternating micrometer-wide lines of Ti0.87O2 and Ca2Nb3O10 were made to locally control the orientation of SrRuO3.
Authors : Lakshminarayana Polavarapu, Guangchao Zheng, Luis M. Liz-Marzán, Isabel Pastoriza-Santos, and Jorge Pérez-Juste*
Affiliations : Lakshminarayana Polavarapu, Guangchao Zheng, Luis M. Liz-Marzán, Isabel Pastoriza-Santos, and Jorge Pérez-Juste* Departamento de Química Física, Universidade de Vigo, 36310 Vigo, Spain Luis M. Liz-Marzán BioNanoPlasmonics Laboratory, CIC biomaGUNE, Paseo de Miramón 182, 20009 Donostia - San Sebastián, Spain Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
Resume : Cellulose paper has been an integral part of our daily lives and their composites with other materials such as polymers and nanoparticles (NPs) have been widely used in analytical chemistry and medicine due to their advantages such as cost efficient, abundance, flexibility, three-dimensional porous structure, biocompatible, and biodegradable.1-3 Recently, plasmonic NP-loaded paper substrates have attracted great attention toward the fabrication of highly efficient surface enhanced Raman scattering (SERS) substrates.2,3 Plasmonic NPs have paid significant attention as optical sensors because of their ability to manipulate the light at nanoparticle surface by their strong surface plasmon resonance, which makes them potential candidates for enhanced optical sensing of chemical and biological species for detection and diagnosis. On the other hand, metal NPs exhibit high catalytic activity, but their applications have been largely hampered by their aggregation. This problem could be solved by the deposition of NPs on solid substrates, particularly flexible substrates such as paper. Fabrication of NP-paper hybrids in a large scale by controlled assembly of NPs on paper is important for future applications such as SERS and catalysis.2 The preparation of NP-paper hybrids via solution process and their applications as SERS substrates and reusable catalysts will be discussed in this talk. References: 1. Bodelón, G.; Mourdikoudis, S.; Yate, L.; Pastoriza-Santos, I.; Pérez-Juste, J.; Liz-Marzán, L. M. Nickel Nanoparticle-Doped Paper as a Bioactive Scaffold for Targeted and Robust Immobilization of Functional Proteins. ACS Nano 2014, DOI: 10.1021/nn5016665 2. Polavarapu, L.; Liz-Marzan, L. M. Towards low-cost flexible substrates for nanoplasmonic sensing. Physical Chemistry Chemical Physics 2013, 15, 5288-5300. 3. Polavarapu, L.; Porta, A. L.; Novikov, S. M.; Coronado-Puchau, M.; Liz-Marzán, L. M. Pen-on-Paper Approach Toward the Design of Universal Surface Enhanced Raman Scattering Substrates. Small 2014, DOI: 10.1002/smll.201400438
Authors : Xiangjun Liu, Gang Zhang and Yong-Wei Zhang
Affiliations : Institute of High Performance Computing, A*STAR, Singapore 138632;Institute of High Performance Computing, A*STAR, Singapore 138632;Institute of High Performance Computing, A*STAR, Singapore 138632
Resume : Controlling the thermal conduction across graphene layers is of great importance for their applications in nanoscale thermal management. However, how to quantitatively control the thermal conduction across the graphene layers is still largely unknown. Here, we performed molecular dynamics simulations to investigate the thermal transport across a junction formed by covalent cross-linkers between two graphene nanoribbons (GNRs). We find that the cross-linkers are effective for transmitting the out-of-plane phonon modes of GNRs, but ineffective for the in-plane modes. Each cross-linker possesses a constant thermal conductance, and there is little thermal coupling between them. Interestingly, the total heat current across the junction is not linearly dependent on the number of cross-linkers, instead, it increases sublinearly initially, and then levels off to about 50% of that of the same size single-layer GNR. A theoretical model is proposed to explain this surprising observation. Our work reveals important new insights into the fundamental principles governing the thermal conduction across chemically cross-linked junctions and provides useful guidelines for the applications of graphene in practical temperature management.
Authors : cells containing halide perovskites Emilio J. Juarez-Perez, Ivan Mora-Sero, Juan Bisquert
Affiliations : Dept. Physics. Group of Photovoltaic and Optoelectronic devices Universitat Jaume I, Avda Sos Baynat s/n, 12071 Castello de la Plana, Spain.
Resume : Recently, a new type of photovoltaic cells using halide perovskites as light harvester materials have rised onto the scene receiving great attention in the scientific community. It has been mainly due to an emergence of record devices in a short time period, which it is now reaching profiles close to 18 % of certified PCE. The light- absorbing semiconductor material is based on a hybrid halide perovskite polycrystalline structure with formula AMX3, where A is a small organic cation (methylammonium, formamidinium), B is a metal cation (Pb2+, Sn2+) and X is a halide anion (I-, Cl-, Br-). An interesting aspect of the manufacture of these photovoltaic devices is that the active layer is solution processable using common lab solvents. The proﬁcient operation of these ABX3 halide perovskite solar has been accomplished by many different approaches as thin-film or mesosuperstructured devices pointing out for an underlying robust photovoltaic operation mechanism. However, a deep understanding of the mechanisms of transport, accumulation of charges and working principles is highly mandatory to assess the possibilities and properties of these materials for further development. Impedance spectroscopy (IS) is a technique capable to discriminate between the different components of the device and provides abundant and useful information on the device working mechanism. Parameters as diffusion length, carrier conductivity and recombination resistance can be straightforwardly extracted using IS.
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Inorganic Nanoarchitectonics : Vanessa Prevot
Authors : M.Zimbone*, P.Baeri*, E. Messina+, G.Compagnini+ , M.E. Fragalà+ and L.Calcagno*
Affiliations : *Dipartimento di Fisica ed Astronomia ,Via S.Sofia, 64 95125 Catania +Dipartimento di Scienze Chimiche, Viale A.Doria, 6 95125 Catania
Resume : Metal Nanoparticles (MeNPs) have recently received large attention for the application in the emergimg plasmonic-based nanotechnology. In MeNPs, the characteristic plasmonic modes, typical of metal surfaces, is combined with nanometric size, giving rise to unique optical properties such as an absorption resonance on the visible wavelength range that depends on the size and shape of nanoparticles. In the present work polarized and depolarized dynamic light scattering methodology was conducted in silver nanoplatelets in water solution, where strong plasmon-enhanced scattering was observed. The hydrodynamic properties of the nanoparticle solutions were determined by measuring the translation and rotational diffusion coefficients for in resonant conditions and the translation diffusion coefficient for out of resonant conditions. The simultaneous measurements of translation and rotational diffusion coefficients allows us to determine the nanoparticle main size. The dynamic properties of nanoparticles have been interpreted by applying an oblate ellipsoidal model which allows a direct evaluation of size and shape in good agreement with Scanning Electron Microscopy results. The characterized nanoparticles reveals a transversal size of 20 nm and a longitudinal length in the range 75-95 nm. Our investigation indicates that depolarized dynamic light scattering in resonant condition is a simple, powerful and non invasive technique to determine the size and shape of plasmonic nanoparticles directly in solution and it can be successfully applied to this type of metallic nanoparticles for characterization and exploration of their dynamics.
Authors : Felicia Iacomi
Affiliations : Physics Department, Alexandru Ioan Cuza University of Iasi, Iasi, Romania
Resume : Inter-particle interactions in iron oxide nanocomposites is investigated by means of electron spin resonance method. Iron oxide/MCM-41, iron oxide/clay mineral and iron oxide/polymer were synthesized using solid reaction, ion exchange and making mixtures from siloxane polymer with hydrophobized silica and iron oxide nanoparticles, choosing certain iron oxide contents and certain silica contents. Information related to the structure, morphology, electrical and magnetic properties is extracted from XRD, FTIR, SEM, TEM, AFM and electrical and magnetic investigations. Electron Spin Resonance results allow to conclude that by controlling the distance between the magnetic particles it is possible to control the dipolar interaction between the aligned particles and that the chemical neighborhood is important. The effect of gamma irradiation on the structure and magnetic properties of iron oxide/clay mineral composites is also analyzed
Authors : Hao Yang, Chun-Kai Lan, Jenq-Gong Duh
Affiliations : R429, Department of Materials Science and Engineering, No. 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013, R.O.C.
Resume : Synthesized nano-sized material with special architecture is a quite considerable challenge when using a simple procedure. Metal doping is one of the useful methods to enhance the conductivity as well as to promote the electrochemical performance. However, fewer research point out other benefits of it. So as to study the advantages of doping, different types of metal ions are chosen for doping into TiO2. By controlled the amount of metal ions, the morphology of TiO2 can be strongly alternated. For niobium ions, the architecture of anatase TiO2 is transformed from spherical-like to plate-like. The plate is constructed by several nanorods which show special orientation along (001) facets. Otherwise, tungsten ions induce some dendrite-like morphology on the top of TiO2 nanosphere. In electrochemical performance, both of niobium and tungsten-doped TiO2 show excellent performance in cyclability and rate capability. The plate-like niobium-doped TiO2 displays a high specific capacity of ~ 220 mAhg-1 at 0.5 C and still retains ~127 mAhg-1 at 10 C and shows 90 % capacity retention even for 10000 cycles at 20 C. The cyclic voltammetry reveals that the improvements of rate capability are beneficial from the surface storage process. The near-surface redox behaviors recognized as the pseudocapacitance plays an important part at high current density. In consequence, all of the results help to understand the importance of pseudocapacitive storage in the high rate capability anode materials.
Authors : Beata Kalska-Szostko, Urszula Wykowska, Dariusz Satuła
Affiliations : Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Bialystok, Poland Faculty of Physcis, University of Bialystok, Lipowa 41, 15-424 Bialystok, Poland
Resume : Nanowires are one of many forms of the nanomaterials. Among others magnetic nanowires quickly won interest of scientist due to their potential applications in high-density storage media or optoelectronic devices. The electrodeposition process is the easiest way to fabricate the nanowires. Such structures can be obtained in structured matrixes for example in pores of anodic aluminum oxide( AAO). It provides to well-ordered arrays of highly packed and oriented nanowires. Size of nanostructures is determined by pores diameter. Their surface coverage, ordering and length can be modified by matrix fabrications process. Obtained in AAO matrix nanowires can be made of the single magnetic element or as alloy-like structures. Modification of the chemical composition of particular layers inside the nanowire structure, influence on their response to external magnetic field what is especially important from the application point of view. Especially there where fluctuation of magnetic moments are of main importance. Modified core-shell structures can serve alone or in composites as sensors, catalyst, delivery carriers, sieves etc. In the paper we are going to present Fe wires covered by noble metal or oxide surface. Structure of the wires and their special arrangement will be studied by XRD, SEM, TEM, EDX while magnetic moment orientation will be characterized by Mössbauer spectroscopy.
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