Nm For TiO2 Research Articles

Effect of Variable Nanogeometry of Titanium oxide-gold Nanocomposite: Application in Electrochemical Sensing of Hydrazine

3-Aminopropyltrimethoxysilane (3-APTMS) and 3-glycidoxypropyltrimethoxy-silane (3-GPTMS) mediated synthesis of gold nanoparticles (AuNPs) of two different sizes [AuNP1 (10 nm) and AuNP2 (20 nm)] were made and used for nano-composite formation with TiO2 nanoparticle suspension. The resulting TiO2-AuNP1 and TiO2-AuNP2 nanocomposites were used for making chemically modified electrodes to understand the role of nanogeometry in chemical sensing. TiO2-AuNP1 and TiO2-AuNP2 nanocomposites were characterized by transmission electron microscopy and UV-VIS spectroscopy. The analytical results revealed the average size of the nanocomposite in the range of 20-25nm. The nanocomposites were employed for modification of graphite paste electrodes and applied in electrochemical sensing of hydrazine. The results demonstrated that TiO2-AuNP1 exhibit better electrocatalytic activity as compared to that of TiO2-AuNP2 and only TiO2 towards oxidation of hydrazine. Amperometric analysis of hydrazine on these electrodes at the applied potential of 0.4 V vs Ag/AgCl was made to quantify the sensing ability of modified electrodes. The sensitivity and lowest detection limit was found as 25, 57.2 and 145.7 μAmM-1cm-2 and 50, 100, 20 nM for TiO2, TiO2-AuNP2 and TiO2-AuNP1 respectively.

A Cost-Effective Method of Aerosolizing Dry Powdered Nanoparticles

The ability to produce nanoscale aerosols from dry powdered material is needed for studies of the toxicity and environmental transformation and fate of manufactured nanoparticles. Wet aerosol generation methods can alter particle chemistry, while dry methods often cannot produce truly nanoscale aerosols. We have developed a cost-effective dry dispersion technique for manufactured nanoparticles and have demonstrated its use with C60 fullerene, TiO2, and CeO2. The system disperses dry powders to create aerosols with mode diameters below 100 nm. Average mode and median diameters for each of the tested manufactured nanoparticles are 91 and 107 nm for C60, 65 and 77 nm for TiO2, and 40 and 43 nm for CeO2. All aerosols exhibit right-skewed unimodal distributions and irregular morphology. Aerosol mass concentrations produced by the dispersion system vary linearly with the mass of nanomaterial loaded into it and are of a magnitude appropriate for inhalation nanotoxicology studies. This work demonstrates the abili...

Stabilizing Cu2S for Photovoltaics One Atomic Layer at a Time

Stabilizing Cu2S in its ideal stoichiometric form, chalcocite, is a long-standing challenge that must be met prior to its practical use in thin-film photovoltaic (PV) devices. Significant copper deficiency, which results in degenerate p-type doping, might be avoided by limiting Cu diffusion into a readily formed surface oxide and other adjacent layers. Here, we examine the extent to which PV-relevant metal-oxide over- and underlayers may stabilize Cu2S thin films with desirable semiconducting properties. After only 15 nm of TiO2 coating, Hall measurements and UV-vis-NIR spectroscopy reveal a significant suppression of free charge-carrier addition that depends strongly on the choice of deposition chemistry. Remarkably, the insertion of a single atomic layer of Al2O3 between Cu2S and TiO2 further stabilizes the active layer for at least 2 weeks, even under ambient conditions. The mechanism of this remarkable enhancement is explored by in situ microbalance and conductivity measurements. Finally, photoluminescence quenching measurements point to the potential utility of these nanolaminate stacks in solar-energy harvesting applications.

Effect of TiO<SUB>2</SUB> Nanoparticles on the Hydrogen Sorption Characteristics of Magnesium Hydride

The present paper explores the enhancement in hydrogen sorption behavior of MgH2 with TiO2 nanoparticles. The catalytic effect of TiO2 nanoparticles with different sizes (7, 25, 50, 100 and 250 nm) were used for improving the sorption characteristics of MgH2. The MgH2 catalyzed with 50 nm of TiO2 exhibited the optimum catalytic effect for hydrogen sorption behavior. The desorption temperature of MgH2 catalyzed through 50 nm TiO2 was found to be 310 degrees C. This is 80 degrees C lower as compared to MgH2 having a desorption temperature of 390 degrees C. It was noticed that the dehydrogenated MgH2 catalyzed with 50 nm TiO2 reabsorbed 5.1 wt% of H2 within 6 minutes at temperature and pressure of 250 degrees C and 50 atm, respectively. The 50 nm TiO2 catalyst lowered the absorption activation energy of MgH2 from - 92 to - 52.7 kJ mol(-1).

Preparation of New Magnetic Nanocatalysts Based on TiO2 and ZnO and Their Application in Improved Photocatalytic Degradation of Dye Pollutant Under Visible Light

Photocatalytic degradation of methyl orange (MO) as a model of an organic pollution was accomplished with magnetic and porous TiO(2)/ZnO/Fe(3)O(4)/PANI and ZnO/Fe(3)O(4)/PANI nanocomposites under visible light irradiation. The structures of nanocomposites were characterized by various techniques including UV-Vis absorption spectroscopy, XRD, SEM, EDS, BET and TGA. Optical absorption investigations show two λ(max) at 450 and 590 nm for TiO(2)/ZnO/Fe(3)O(4)/PANI nanocomposites respectively possessing optical band gaps about 2.75 and 2.1 eV smaller than that of the neat TiO(2) and ZnO nanoparticles. Due to these optical absorptions, the nanocomposites can be considered promising candidates as visible light photocatalysts to produce more electron-hole pairs. The degradation of MO, extremely increased using polymeric photocatalysts and decolorization in the presence of visible light achieved up to 90% in less than 20 min in comparison with the neat nanoparticles (about 10%). All these advantages promise a bright future for these composites as useful photocatalysts. The degradation efficiency of MO using stable nanocomposites was still over 70% after ten times reusing. The highest decolorizing efficiencies were achieved with 0.75 g L(-1) of catalyst and 10 mg L(-1) of MO at natural pH under visible light irradiation in less than 20 min.

Electromagnetic properties of microwave sintered xTiO2 + (1 − x) CoFe2O4 nanocomposites

The nanocomposites of xTiO2 + (1 − x) CoFe2O4 (where 0 ≤ x ≥ 1) were prepared using microwave–hydrothermal method at 165 °C/45 min. The as-synthesized powders were characterized using X-ray diffraction (XRD), transmission electron microscope and Fourier transform infrared spectroscopy. The particle size was found to be ~18, ~22 and 24 nm for TiO2, CoFe2O4, 50 mol% TiO2 + 50 mol% CoFe2O4 composite powder, respectively. The as-prepared powders were densified at 500 °C/30 min using microwave sintering method. The sintered composite samples were characterized using XRD and field emission scanning electron microscopy. The bulk densities of the present composites were increasing with an addition of TiO2. The saturation magnetization of composites decreased with an increase of TiO2 content. The grain sizes of all the composite lies between 54 and 78 nm. The addition of TiO2 to ferrite increased e′ and e″ and the resonant frequency of all the sintered samples were found to be >1 GHz. The value of μ″ found to increase with an increase of TiO2.

Nanostructured titanium dioxide film preparation using inorganic nanoparticles instead of organic precursor materials.

Carbon dioxide is a major contributor to global warming. A promising method of reducing the concentration of atmospheric carbon dioxide is by photocatalytic conversion of carbon dioxide into renewable fuels, which has to be done using a photocatalytic film. The nanostructured film preparation method proposed in this study is a preparation of colloidal solution followed by film deposition using manual coating methods, mostly vertical dip-coating. Deposited films were calcined to forma crystalline film on the glass substrate. This method was adopted in case of film preparation from titanium dioxide. Comprehensive study on impact of different factors including temperature, type of surfactants, type of solvents, concentration of surfactants, and concentration of solvents on quality of thin film including band gap, particle size, strength and homogeneity was performed in this work. Material characterisation tests including UV-visible spectroscopy and field emission scanning electron microscopy were carried out to analyse the film characteristics. Mechanical tests including wipe test, rinse test, acetone test, scratch test and scotch tape test were performed to analyse the mechanical strength of obtained thin film. Nanostructured films were successfully prepared with controlled particle size in the range of 70 - 100 nm for TiO2. Films obtained in this study demonstrate acceptable durability and partial uniformity. The film preparation method used in this study was markedly economical, facile and reproducible.

Toward a Low-Temperature Sol−Gel Synthesis of TiO2(B) Using Mixtures of Surfactants and Ionic Liquids

An approach toward the synthesis of nanocrystalline TiO2(B) in surfactant/ionic liquid systems at low temperature (100 °C) by means of sol−gel chemistry is presented. As reaction medium, a solution of imidazolium- and ammonium-based surfactants in ionic liquids was applied. Interestingly, TiO2(B), in coexistence with anatase, was observed only in cases where the ionic liquid is based on imidazolium moieties. The final product contained up to 60 wt % TiO2(B), depending on the initial amount of surfactant. X-ray powder diffraction measurements and transmission electron microscopy revealed small particle sizes (ca. 2 nm for TiO2(B), around 6 nm for anatase) as well as a high crystallinity of the material. The materials possessed surface areas up to 300 m2/g. Electrochemical studies further confirmed the presence of the two titania polymorphs anatase and TiO2(B) in similar proportions. Small-angle X-ray scattering experiments gave insight into the phase behavior of the surfactant in the ionic liquid under reaction conditions. The formation of TiO2(B) is discussed based on systematic variation of diverse parameters.

Experimental evaluation of individual protection devices against different types of nanoaerosols: graphite, TiO2, and Pt

In this study different conventional individual protection devices, well-qualified for submicron particles were tested for different types of polydispersed nanoaerosols of TiO2, Pt, and graphite. The electrical mobility diameters of the generated particles are ranging from 9 to 19 nm for Pt, 9 to 90 nm for TiO2, and 15 to 90 nm for graphite. Toward this purpose, two specific test benches were used: one for the filter-based devices which are tested under a controlled air flow, and the other one for protective clothing and gloves under diffusion and without air flow. Different types of nanoaerosols, such as TiO2, Pt, and graphite, were generated. Electrostatic and HEPA (High Efficiency Particle Air) filters have shown the highest efficiency for graphite nanoparticles. The main hypothesis for explaining this effect is that electrostatic forces could enhance the graphite nanoparticles capture. Air-tight fabrics made of non-woven textile seem much more efficient in protecting workers against Pt, and TiO2 nanoparticles than cotton and polypropylene. With regard to protective clothing, no obvious effect linked to the aerosol type was observed. Gloves are found very efficient for TiO2 and Pt nanoaerosols. Therefore, no effect of aerosol on the protection efficiency of gloves was evidenced.

The deposition of nanocrystalline TiO 2 thin film on silicon using Sol–Gel technique and its characterization

TiO 2 thin films were deposited using Sol–Gel spin coating technique using titanium isoperoxide as the Titania precursor. The films were characterized using X-ray diffraction, capacitance voltage measurement and Raman characterization technique. The XRD and Raman spectra indicate the presence of anatase TiO 2 phase in the film. The grain size as calculated using the Scherrer’s formula was found to be 30, 66 and 59 nm for TiO 2(0 0 4), TiO 2(2 0 0) and TiO 2(2 1 1), respectively. The grain size was found to increase after annealing at 800 °C. The dielectric constant as calculated using capacitance voltage measurement was found to be 25. The refractive index of the film was 2.34.

Conducting Polymer Memory Devices Based on Dynamic Doping

Molecular electronic junctions consisting of a 20 nm thick layer of polypyrrole (PPy) and 10 nm of TiO2 between conducting layers of carbon and gold were investigated as potential nonvolatile memory devices. By making the polymer layer much thinner than conventional polymer electronic devices, it is possible to dynamically oxidize and reduce the polypyrrole layer by an applied bias. When the electrode in contact with the PPy is biased positive, oxidation of the PPy occurs to yield a conducting polaron state. The junctions exhibit a large increase in conductance in response to the positive bias, which is reversed by a subsequent negatively biased pulse. Switching between the conducting and nonconducting state can occur for pulses at least as short as 10 micros, and the conducting state persists after a positive bias pulse for at least 1 week. The read/write/read/erase cycle may be repeated for at least 1700 cycles, although with an error rate of approximately 3% due mainly to an incomplete "erase" step. The speed and retention of the PPy/TiO2 junctions are far superior to those of the analogous fluorene/TiO2 devices lacking the polymer, and the conductance changes are absent if SiO2 is substituted for TiO2. The observations are consistent with "dynamic doping" of the solid-state polymer layer, with the possible involvement of adventitious mobile ions. Although the speed of the current polymer/TiO2 junctions is slower than commercial dynamic random access memory, their retention is approximately 5 orders of magnitude longer.

Polyhedral oligomeric silsesquioxane trisilanols as dispersants for titanium oxide nanopowder

AbstractTrisilanol isobutyl polyhedral oligomeric silsesquioxane (POSS) was used to disperse nanosized titanium dioxide (TiO2) particles in polypropylene (PP). The silanol groups of the POSS cage were bound to the surface of the TiO2 particles, creating a layer of isobutyl POSS that improved compatibility with the PP matrix. POSS was an effective dispersant both when applied in a chemical pretreatment of TiO2 and when simply added to the blend during melt compounding. The average particle size of TiO2 was reduced from 70 nm for neat TiO2 to 50 nm for the POSS/TiO2 blend to 33 nm for TiO2 chemically treated with POSS. Additionally, the POSS coating improved the color of the material and reduced the catalytic effect of TiO2 on thermooxidative degradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

From particle self-assembly to functionalized sub-micron protein patterns

Biologically relevant nanopatterns are useful platforms to address fundamental questions,for example, regarding protein–protein and cell–protein interactions. For the creation ofnanopatterns, complex and expensive instrumentation is often needed. We presenta simple but versatile patterning method using a combination of particle andsubsequent molecular self-assembly to produce ordered structures in the micronand sub-micron range. Polystyrene particles were, in a first step, assembled viadip-coating or dried in a drying cell. Silicon wafers and glass slides coated withSiO2 and a top layerof 11 nm of TiO2 were used as substrates. Large hexagonally ordered particle monolayers were formed with highreproducibility. These were subsequently shrunk in a controlled manner by exposure to aO2/N2 plasmaand subsequently used as etching masks to transfer the particle pattern onto the substrate, creatingTiO2 featuresin an SiO2 background. After removing the mask the oxide contrast was translated in three simpledip-and-rinse steps into a biochemical contrast of protein-coated features in an inertbackground. In short, alkane phosphates were first selectively adsorbed to theTiO2 features.Then the SiO2 background was backfilled using poly(L-lysine)–graft-poly(ethylene glycol) and finallystreptavidin was adsorbed to the hydrophobic alkane phosphate SAMs, allowing subsequentbinding and hybridization of biotinylated DNA.

Photocatalytic inactivation of Gram-positive and Gram-negative bacteria using fluorescent light

A batch photocatalytic study was carried out to inactivate six different species of bacteria using fluorescent light and TiO 2 photocatalyst. Several surface loadings of TiO 2 varying from 234 to 8662 mg/m 2, impregnated on membrane filters were used with fluorescent light of constant illuminance of 3900 lux for the inactivation of four ATCC bacteria ( Escherichia coli K-12, Pseudomonas fluorescens, Bacillus subtilis and Microbacterium sp.) and two other species of bacteria collected from outdoor air in Singapore ( Microbacteriaceae str. W7 and Paenibacillus sp. SAFN-007). Gram-negative bacterium E. coli K-12 was the most effectively inactivated, while Gram-positive B. subtilis exhibited the least response to the photocatalytic treatment. The inactivation rate increased with an increase in the TiO 2 loading, the maximum inactivation of most bacteria was achieved at an optimum TiO 2 loading of 511–1666 mg/m 2, corresponding to a thickness of 294–438 nm of TiO 2 layer on the surface. 100% of the E. coli K-12 was inactivated after 30 min of treatment at a TiO 2 loading of 1666 mg/m 2, while inactivation of 1 log 10 was obtained for Microbacterium sp., Paenibacillus sp. SAFN-007 and Microbacteriaceae str. W7 after 2 h of illumination at a TiO 2 loading of 1116 mg/m 2.

Iron-doped photocatalytic TiO 2 sputtered coatings on plastics for self-cleaning applications

Titanium dioxide is among the few semiconductors that have good chemical/photochemical stabilities and high oxidation power. However, its relatively high band gap makes it only effective when exposed under UV light. It has been found that the addition of transition metals to TiO 2 can improve the photocatalytic activity by UV irradiation and extend its use in the visible region of the electromagnetic spectrum. In this work, the reactive magnetron sputtering method was used to prepare pure and Fe-doped titanium dioxide thin films. The films were deposited onto microscope glass slides and polycarbonate plates at different total pressures and iron-doping concentrations. The morphology of the films was analysed by atomic force microscopy (AFM) and their structure by X-ray diffraction (XRD). The effect of Fe-doping and total sputtering pressure on the photocatalytic activity, was evaluated by measuring the degradation rates of the rhodamine-B (RhB) dye under UV irradiation. The experimental results show that the deposited TiO 2 films on the glass substrate were of the anatase phase with a 〈0 0 4〉 preferred orientation. On contrary, for TiO 2 films deposited on the polycarbonate substrate only an amorphous structure was obtained. The crystallite sizes of the films were 4.1 and 7.1 nm for TiO 2 films deposited at total sputtering pressures of 0.4 and 0.5 Pa, respectively. The iron doped films resulted in the light absorbance shifting to the visible range of the electromagnetic spectrum. In general, iron doping led to a decrease in the photocatalytic activity of TiO 2 films deposited on both substrates. However, the highest photodegradation rates were obtained for films deposited on the polymer substrate under the lower total pressure of 0.4 Pa.

Layer-by-layer nanoparticle coatings on lignocellulose wood microfibers

The layer-by-layer (LbL) self-assembly technique was applied to deposit organized multilayers of TiO 2 or SiO 2 nanoparticles of 30–80 nm diameter, and 50-nm diameter halloysite clay nanotubes on softwood fibers. Fluorescent and scanning electron microscopy images showed complete nanoparticle coating on these fibers. The thickness of the two-layer coating was estimated as 46, 58, and 115 nm for TiO 2, SiO 2, and halloysite tubules, respectively, which corresponds to ca. 1 wt% nanoparticle loading of the fibers. The brightness test of paper handsheets prepared from nanocoated fibers showed that TiO 2 nanoparticle coating gave handsheet reflectance of 84% at 450 nm, which is 4% higher than the brightness of the control sample from virgin fibers. The paper handsheets prepared with nanoparticle-coated fibers had 30–50% higher porosity with tensile strength index retained close to the control sample.

Oxide nanopowders from the low-temperature processing of metal oxide sols and their application as gas-sensing materials

SnO 2, TiO 2, and In 2O 3 sols were prepared by a chemically modified sol–gel process. By injecting the sols into a solution of two components at 160 °C in non-solvothermal conditions, differently crystallized products were obtained, which were finally crystallized and purified by heat-treatments at 500 °C. The heat-treatments did not result in remarkable grain growth, as shown by X-ray diffraction and transmission electron microscopy. The mean crystallite size in the heat-treated powders was found to range from 3.5 nm for In 2O 3 to 8.5 nm for TiO 2. Drop-coating of the powders onto alumina substrates allowed the fabrication of gas-sensing devices. The SnO 2 and In 2O 3 based devices were tested to NO 2, displaying outstanding responses even at temperatures as low as 100 °C, and fast responses and recovery times.

Preparation and Characterisation of Nano-Structured WO3-TiO2 Layers for Photoelectrochromic Devices

Nano-structured WO3-TiO2 layers were prepared by the sol-gel route. To obtain transparent, porous and crack free layers up to 0.8 μ m with a single dipping cycle a templating strategy was used. As a template three-dimensionally network based on organically modified silane was introduced to the WO3 and TiO2 sols. The WO3 layers were dip-coated onto the conductive glass substrate (TCO) and the TiO2 layers on the top of the WO3 layer. The morphology and the structure of the layers were determined by Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), Energy Dispersive X-Ray Spectroscopy (EDXS), Auger and Infrared spectroscopy. SEM image of the WO3-TiO2 layer confirmed the nano-porosity of the layers and give the size of the particles of about 10 nm for TiO2 and 30 nm for WO3 layer. Further analysis indicated that the titanium sol penetrates the WO3 layer. Particles in the WO3 layer consist of a crystalline monoclinic WO3 core surrounded by a 5–10 nm amorphous phase consisting of WO3, TiO2 and SiO2. The WO3-TiO2 layers were used to assemble all solid state photoelectrochromic (PE) devices. Under 1 sun irradiation (1000 W/m2) the visible transmittance of the PE device changes from 62% to 1.6%. The colouring and bleaching processes last about 10 minutes.

Development of fabrication process for metal oxide with nano-structure by the liquid-phase infiltration (LPI) method

To develop a preparation method for size-controlled nanoparticles, we applied a liquid-phase infiltration (LPI) method to the reverse micelle (RM) reaction. The average sizes of the nanoparticles were 4.6 and 2.0 nm for TiO 2 and FeO, respectively. The size distribution was narrow, and particle crystallization was promoted by the nanoscale reaction field. We have also fabricated the TiO 2/Au films with a highly ordered periodic structure by the LPI method using colloidal crystals as a template. The LPI process is conducive to the preparation of advanced nanoceramics with highly ordered structures.

A SANS Study of 3PEG−LiClO4−TiO2 Nanocomposite Polymer Electrolytes

Nanocomposite polymer electrolytes based on a fully amorphous polymer electrolyte (trihydroxypoly(ethylene oxide-co-propylene oxide), known as 3PEG, with LiClO4 salt) were studied by means of small-angle neutron scattering with the aim to clarify how the filler particles (nanosized TiO2 or Al2O3) are distributed in the polymer. The scattering data show that the particles are not well dispersed but aggregate in fractal, polymer-like structures. The structures, with a fractal dimension of ∼2 on length scales from 100 nm up to at least 400 nm, consist of branched chains which are about 1−2 primary particles wide (∼40 nm for TiO2 and ∼30 nm for Al2O3). The obtained results provide structural support for the hypothesis of earlier works that the ionic conductivity increase observed in nanocomposite polymer electrolytes is due to the formation of a percolating layer close to the filler particles with higher conductivity.