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ZnO Nanoparticles (zno + nanoparticle)
Selected AbstractsOrganization of Organic Molecules with Inorganic Nanoparticles: Hybrid Nanodiodes,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2008Kallol Mohanta Abstract A monolayer of inorganic nanoparticles and a monolayer of organic molecules have been electrostatically assembled in sequence. Such assemblies or organizations exhibit electrical rectification. When the sequence of the organization is reversed, the direction of rectification becomes opposite. In both n-type ZnO/organic and organic/n-ZnO assemblies, electron flow is favorable from the n-ZnO nanoparticle to the (electron-accepting) organic molecule. While the individual components do not show any rectification, substitutes of the organic molecule tune electrical rectification. Junctions between a p-type ZnO nanoparticle and an electron-donating metal phthalocyanine favor current flow in the nanoparticle-to-phthalocyanine direction. The rectification in a junction between a nanoparticle and an organic molecule is due to the parity between free carriers in the former component and the type of carrier-accepting nature in the latter one. By observing electrical rectification with the tip of a scanning tunneling microscope, organic/inorganic hybrid nanodiodes or rectifiers on the molecular/nanoscale have been established. [source] Comparison of UV optical properties of ZnO nanoparticles dispersed in traditional organic and novel bio-molecular solventsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010Liqiao Qin Abstract Two types of ZnO nanoparticles were dispersed in a bio-molecular solvent and in ethanol. The mixtures were characterized by photoluminescence and absorbance measurements. Strong UV emission was observed near the band gap of ZnO at 380 nm. The parasitic green emission which normally appears in ZnO suspensions was weakened when ZnO was dispersed in the bio-molecular solvent. Suspensions were spin-cast on quartz, and then Al contacts were deposited by a standard lift-off process via e-beam lithography. Point contact current-voltage characteristics of the samples were measured under equal intensity conditions using 340 nm UV LED and white LED sources. The ratio of the UV photo-generated current to dark current was as high as 105. Finally, the photocurrent response spectrum was measured. The results show that ZnO nanoparticle is favourable for visible blind UV photodetectors. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Facile and Reproducible Synthesis of Nanostructured Colloidal ZnO Nanoparticles from Zinc Acetylacetonate: Effect of Experimental Parameters and Mechanistic InvestigationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2009Alessia Famengo Abstract A facile and reproducible route to nanostructured colloidal ZnO nanoparticles was developed by controlled hydrolysis and condensation of zinc acetylacetonate in alkaline conditions. By reaction of an ethanolic solution of Zn(acac)2 with NaOH in a 1:2 molar ratio, after reflux, ZnO spherical nanoparticles were obtained that displayed a homogeneous size distribution; particle diameters ranged from 6 to 10 nm, as evidenced by transmission electron microscopy (TEM) analysis. The same reaction was carried out also in water, glycerol and 1,2-propanediol, to investigate the effect of the solvent viscosity and dielectric constant on the final features of the obtained material. Irrespective of the nature of the solvent, X-ray diffraction (XRD) analysis shows the formation ofhexagonal ZnO, whereas the presence of residual unreacted Zn(acac)2 could be ruled out. Indeed, different particle sizes and very different morphologies were obtained. Also the reflux step was shown to be a key factor in avoiding the fast precipitation of a floc and achieving a pure compound, which was isolated and thoroughly characterised. The composition of the obtained ZnO was determined by elemental analysis, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), showing the formation of pure ZnO. IR spectroscopy evidenced the presence of adsorbed organic ligands on the colloid surfaces. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) revealed the presence of medium- to high-strength acidic sites on the ZnO surface. To gain a deeper insight into the formation mechanisms of these nanostructures, time-resolved UV/Vis and XAS studies were performed on the ethanol solution used for the synthesis of the oxide and also on the solid specimen, obtained after the refluxing step. No remarkable changes could be evidenced in the solution after the addition of an understoichiometric amount of NaOH, but the growth of the ZnO nanoparticles could be followed by UV/Vis spectra. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] ZnO Nanoparticles From a Metal-Organic Framework Containing ZnII MetallacyclesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2007Harjyoti Thakuria Abstract Nitrilotriacetic acid (H3NTA) reacts in the solid phase with zinc hydroxide (1:1) to form a 3D ladder-like metal-organic framework that forms wurtzite ZnO nanoparticles when heated above 600 °C. Complex 1 contains a 1D zig-zag water chain. A mixed coordination network 2 is formed with excess ZnII hydroxide, which, on decomposition at about 500 °C, forms microwires of ZnO.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Preparation of ZnO Nanowires in a Neutral Aqueous System: Concentration Effect on the Orientation Attachment ProcessEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Ming Yang Abstract ZnO nanowires with diameters in the range of 10 to 30 nm and lengths of ca. several micrometers are prepared with the use of ZnO nanoparticles as building blocks. The length and diameter of the ZnO nanowires can be controlled by the variation of the concentration of the nanoparticles in the orientation attachment process. A plausible mechanism for the concentration-controlled orientation attachment process is suggested. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Nanocomposite Microcontainers with High Ultrasound SensitivityADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Tatiana A. Kolesnikova Abstract A water suspension of nanocomposite microcapsules with embedded ZnO nanoparticles in the capsule shell is reported. The microcapsule morphology is characterized by confocal microscopy, TEM, SEM, and AFM before and after ultrasound treatment. A remarkably high capsule sensitivity to ultrasound is evidenced, and it is observed to grow with increasing number of ZnO nanoparticle layers in the nanocomposite shell. This effect is correlated with the mechanical properties of microcapsules measured with AFM. [source] Enhanced Antibacterial Activity of Nanocrystalline ZnO Due to Increased ROS-Mediated Cell InjuryADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Guy Applerot Abstract An innovative study aimed at understanding the influence of the particle size of ZnO (from the microscale down to the nanoscale) on its antibacterial effect is reported herein. The antibacterial activity of ZnO has been found to be due to a reaction of the ZnO surface with water. Electron-spin resonance measurements reveal that aqueous suspensions of small nanoparticles of ZnO produce increased levels of reactive oxygen species, namely hydroxyl radicals. Interestingly, a remarkable enhancement of the oxidative stress, beyond the level yielded by the ZnO itself, is detected following the antibacterial treatment. Likewise, an exposure of bacteria to the small ZnO nanoparticles results in an increased cellular internalization of the nanoparticles and bacterial cell damage. An examination of the antibacterial effect is performed on two bacterial species: Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive). The nanocrystalline particles of ZnO are synthesized using ultrasonic irradiation, and the particle sizes are controlled using different solvents during the sonication process. Taken as a whole, it is apparent that the unique properties (i.e., small size and corresponding large specific surface area) of small nanometer-scale ZnO particles impose several effects that govern its antibacterial action. These effects are size dependent and do not exist in the range of microscale particles. [source] Low-Temperature Solution-Processed Memory Transistors Based on Zinc Oxide NanoparticlesADVANCED MATERIALS, Issue 30 2009Hendrik Faber We report on thin!film transistors based on ZnO nanoparticles processed from solution and with a maximum temperature of 100,°C. Electron mobilities up to 2.5,cm2V,1s,1 are obtained, and top-gate TFTs show non-volatile memory properties with a large, stable hysteresis and a memory ratio of 105. Memory TFTs operate in ambient, have good shelf-life (>6 months), and useful endurance properties. [source] Low-Temperature Synthesis of Zinc Oxide NanoparticlesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2006Po-Yi Wu Crystalline zinc oxide nanoparticles have been prepared by mixing aqueous solutions of zinc nitrate and hexamethylenetetramine (HMT) at 60°C and 80°C. Transmission electron microscopy and X-ray diffraction show that the ZnO nanoparticles of diameters ranging from 15,33 nm and 25,43 nm long are formed. Aspect ratio is observed to range from 1.18 to 1.74 at 60°C and 1.22 to 1.70 at 80°C as the HMT to zinc nitrate concentration ratio increases from 10 to 150. Nanoparticle size decreases as the concentration of HMT increases. Much larger ZnO particles are formed with ammonium hydroxide as a hydrolysis agent without HMT. In summary, HMT is an ammonium-hydroxide source in the reaction, a surfactant for retaining nanosize, and not necessarily a template for ZnO nucleation. [source] Efficient Hybrid Solar Cells from Zinc Oxide Nanoparticles and a Conjugated Polymer,ADVANCED MATERIALS, Issue 12 2004ZnO nanoparticles dispersed in a semiconducting polymer form the active layer of a solar cell (see Figure) that is able to convert up to 40,% of the incident photons at 500,nm into electrical current and has a power conversion efficiency of about 1.5,% in sunlight. Manufactured at low temperature using environmentally friendly materials, it represents a new step to ,green electricity'. [source] Optical and thermo electrical properties of ZnO nano particle filled polystyreneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Mulayam S. Gaur Abstract The study of optical and thermally stimulated electrical properties such as optical band gap, refractive index, X-ray spectra, SEM spectra, thermally stimulated discharge current (TSDC), differential scanning calorimetry (DSC) have been undertaken in ZnO nanoparicle filled polystyrene nanocomposite thin film of 30 ,m thickness. The appearance of single TSDC peak at temperature 408 ± 5 K in nanocomposite samples shows the charge carriers injected from deeper trapping levels. It is due to the modification of surface and bulk properties of polystyrene by filling of ZnO nanoparticles. In other hand, the strong interaction of nanoparticles with polymer matrix is the expected reason of improvement of crystallite size, optical energy band gap, refractive index, TSDC, glass transition temperature, and charge storage. It is confirmed from SEM images that the modifications of these properties are caused by creation of clusters in amorphous,crystalline boundaries of pristine polystyrene. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Effect of the origin of ZnO nanoparticles dispersed in polyimide films on their photoluminescence and thermal stabilityJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Anongnat Somwangthanaroj Abstract Polyimide (PI) films containing dispersed ZnO nanoparticles were prepared from both zinc nitrate hexahydrate (designated as Zn(NO3)2/PI) and ZnO nanoparticles, 2-nm average primary size (ZnO/PI). This work shows how the origin of ZnO affects both the photoluminescence and thermal decomposition of the film. The presence of ZnO derived from Zn(NO3)2·6H2O was confirmed by X-ray diffraction technique. The fluorescent intensities from Zn(NO3)2/PI and ZnO/PI were much higher than that from pure PI films. When the ZnO concentration exceeded a certain saturation level, the emission intensity decreased due to the undesirable aggregation of ZnO. At the same concentration, ZnO/PI exhibited higher emission intensity than Zn(NO3)2/PI. All samples prepared under nitrogen emitted higher intensity than their counterparts prepared under argon. The ZnO/PI film was thermally more stable than the Zn(NO3)2/PI one. From TEM images of 117.6 mol% ZnO/PI films, the ZnO aggregates, whose average size was 17,90 nm, were well distributed throughout the film but poorly dispersed in nanometer range. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Photocatalytic degradation of methyl tert -butyl ether (MTBE) in contaminated water by ZnO nanoparticlesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2008Akbar Eslami Abstract BACKGROUND: Over the past several decades methyl tert -butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV-visible/ZnO/H2O2 photocatalytic process. The effects of important operational parameters such as pH, amount of H2O2, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert -butyl formate and tert -butyl alcohol were measured. RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L,1. The first-order rate constants for degradation of MTBE were estimated to be 0.183,0.022 min,1 as the concentration increased from 10 to 500 mg L,1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L,1 MTBE complete mineralization was obtained after 100 min under UV-visible/ZnO/H2O2 photocatalysis. CONCLUSION: The data presented in this paper clearly indicated that UV-visible/ZnO/O2 as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE-contaminated waters. Copyright © 2008 Society of Chemical Industry [source] In situ thermo-TOF-SIMS study of thermal decomposition of zinc acetate dihydrateJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2004Anil Vithal Ghule Abstract Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for an in situ thermal decomposition study of Zn(CH3COO)2·2H2O forming ZnO nanoparticles. TOF-SIMS spectra were recorded at regular temperature intervals of 25 °C in positive and negative detection modes in a dynamic thermal process. Controlled heating (5 °C min,1) of Zn(CH3COO)2·2H2O was also carried out using thermogravimetric analysis (TGA) in an oxygen atmosphere (20 ml min,1). Nearly spherical ZnO nanoparticles with no agglomeration and a narrow size distribution (diameter ,50 nm) were observed, which were characterized using scanning electron microscopy, transmission electron microscopy and x-ray diffraction. In situ thermo-TOF-SIMS was used to monitor the 64Zn+ and 66Zn+ ion abundances as a function of temperature, which showed a similar profile to that observed for weight loss in TGA during decomposition. Based on the experimental results, a possible decomposition mechanism for the formation of ZnO is proposed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Microstructure of Varistors Prepared with Zinc Oxide Nanoparticles Coated with Bi2O3JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2004Fangli Yuan Zinc oxide (ZnO) nanoparticles coated with 1,5 wt% Bi2O3 were prepared by precipitating a Bi(NO3)3 solution onto a ZnO precursor. Transmission electron microscopy showed that a homogeneous Bi2O3 layer coated the surface of the ZnO nanoparticles and that the ZnO particle size was ,30,50 nm. Scanning electron microscopy showed that ZnO grains sintered at 1150°C were homogeneous in size and surrounded by a uniform Bi2O3 layer. When the ZnO grains were surrounded fully by Bi2O3 liquid phases, further increases in the ZnO grain size were not affected by the Bi2O3 content. This predesigned ZnO nanoparticle structure was shown to promote homogeneous ZnO grains with perfect crystal growth. [source] Kinetics of Electrophoretic Deposition for Nanocrystalline Zinc Oxide CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004Yuan-Chung Wang An integrated process combining the preparation of ZnO nanoparticles and the formation of ZnO coatings using electrophoretic deposition (EPD) is reported. The work focuses on the deposition kinetics of nanocrystalline ZnO coatings on copper electrodes during EPD by direct measurement of the thickness of the deposited layer. The experimental results show that the EPD process is a powerful route to fabricate uniform coatings with desired thickness and excellent surface smoothness, which might be attributed to small particle size and narrow size distribution. On the other hand, the deposition kinetics changes with applied voltage and deposition time. The deposition thickness increases with increasing applied voltage and deposition time. In a short deposition time, the deviation of deposition rate between the theoretical and experimental values is caused by voltage drops during deposition, and the discrepancy increases with the applied voltage. Moreover, the increasing voltage drop and depletion of the suspension lead to decreasing current and lower deposition rate after longer deposition time. The critical transition time of deposition kinetics is found to exponentially decrease with increasing applied voltage. [source] Nano-Level Mixing of ZnO into Poly(methyl methacrylate)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2010Mukesh Agrawal Abstract A simple, facile and versatile approach is presented for the preparation of PMMA/ZnO nanocomposite materials, which possess high transparency, no color, good thermal stability, UV absorption and improved mechanical properties. The employed process involved mixing of ZnO nanoparticles dispersed in DMAc with the PMMA matrix dissolved in the same solvent. The effect of ZnO content on the physical properties of the PMMA matrix is studied. A significant improvement in mechanical properties was observed with the incorporation of 0.5 wt.-% ZnO particles. The beauty of the described approach lies in the fact that despite being a simple and facile approach, it offers nano-level (2,5,nm) mixing of ZnO nanoparticles into a polymer matrix. [source] ZnO nanostructures for photovoltaic cellsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2010Belete A. Gonfa Abstract In this work the use of different ZnO nanostructures has been studied to assess the effect of morphology and surface modification on the performance of photovoltaic devices. ZnO nanostructures (nanoparticles, nanowires and nanofibres) have been produced by different techniques, and surface modified with pyrene-1-carboxylic acid (PCA). The materials prepared were characterized by XRD, UV,Visible spectroscopy, TEM and SEM. The photovoltaic devices have been prepared in two different configurations: glass/ITO/PEDOT:PSS/photoactive layer/Al and glass/ITO/ZnO/photoactive layer/PEDOT:PSS/Ag paste using spin coating and were characterized by current,voltage characteristics measurement under simulated standard illumination conditions. Whilst ZnO nanoparticles yielded the best results, surface modification with PCA resulted in solar cells with higher short circuit current densities but lower open circuit voltage pointing to a better carrier collection but also higher recombination. [source] Comparison of UV optical properties of ZnO nanoparticles dispersed in traditional organic and novel bio-molecular solventsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010Liqiao Qin Abstract Two types of ZnO nanoparticles were dispersed in a bio-molecular solvent and in ethanol. The mixtures were characterized by photoluminescence and absorbance measurements. Strong UV emission was observed near the band gap of ZnO at 380 nm. The parasitic green emission which normally appears in ZnO suspensions was weakened when ZnO was dispersed in the bio-molecular solvent. Suspensions were spin-cast on quartz, and then Al contacts were deposited by a standard lift-off process via e-beam lithography. Point contact current-voltage characteristics of the samples were measured under equal intensity conditions using 340 nm UV LED and white LED sources. The ratio of the UV photo-generated current to dark current was as high as 105. Finally, the photocurrent response spectrum was measured. The results show that ZnO nanoparticle is favourable for visible blind UV photodetectors. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sonochemical Preparation of Hierarchical ZnO Hollow Spheres for Efficient Dye-Sensitized Solar CellsCHEMISTRY - A EUROPEAN JOURNAL, Issue 29 2010Chun-Xiu He Abstract Hierarchical ZnO hollow spheres (400,500,nm in diameter) consisting of ZnO nanoparticles with a diameter of approximately 15,nm have been successfully prepared by a facile and rapid sonochemical process. The formation of hierarchical ZnO hollow spheres is attributed to the oriented attachment and subsequent Ostwald ripening process according to time-dependent experiments. The as-prepared ZnO hollow spheres are used as a photoanode in dye-sensitized solar cells and exhibit a highly efficient power conversion efficiency of 4.33,%, with a short-circuit current density of 9.56,mA,cm,2, an open-circuit voltage of 730,mV, and a fill factor of 0.62 under AM 1.5,G one sun (100,mW,cm,2) illumination. Moreover, the photovoltaic performance (4.33,%) using the hierarchical ZnO hollow spheres is 38.8,% better than that of a ZnO nanoparticle photoelectrode (3.12,%), which is mainly attributed to the efficient light scattering for the former. [source] | |||||||||||||||||||||||||||||||