Deposition Of TiO2 Nanoparticles Research Articles

Optical visualization of individual ultralong carbon nanotubes by chemical vapour deposition of titanium dioxide nanoparticles

Direct visualization and manipulation of individual carbon nanotubes in ambient conditions is of great significance for their characterizations and applications. However, the observation of individual carbon nanotubes usually requires electron microscopes under high vacuum. Optical microscopes are much more convenient to be used, yet their resolution is low. Here we realize the visualization and manipulation of individual ultralong carbon nanotubes under optical microscopes by deposition of TiO2 nanoparticles on them. The strong scattering of TiO2 nanoparticles to visible light renders them visible by optical microscopes. Micro-Raman-spectroscopy measurement of individual carbon nanotubes is greatly facilitated by their optical visualization. With the assistance of TiO2 nanoparticles, individual carbon nanotubes can be easily manipulated under an optical microscope at macroscopic scale and in ambient conditions. Based on our approach, various manipulation of ultralong carbon nanotubes, including cutting, transfer, fabrication of structures/devices and pulling out inner shells of multiwalled carbon nanotubes, are demonstrated.

Solid-phase microextraction of phthalate esters from aqueous media by electrophoretically deposited TiO2 nanoparticles on a stainless steel fiber

A novel SPME fiber was prepared by electrophoretic deposition of titanium dioxide nanoparticles (nano-TiO2) on a stainless steel wire. It was used in the direct immersion solid-phase microextraction (DI-SPME) of four phthalate esters from aqueous samples prior to gas chromatographic (GC) analysis. The effects of various parameters on the efficiency of the SPME process such as the mode of extraction, extraction temperature, film thickness of the SPME fiber, salt content, extraction time and stirring rate were investigated. The comparison of the fiber with another homemade poly(3,4-ethylenedioxythiophene)-TiO2 (PEDOT-TiO2) nanocomposite fiber and a commercial polydimethylsiloxane (PDMS) fiber showed the better extraction efficiency of the nano-TiO2 fiber for phthalate esters. Under optimized conditions, the limit of detection (LOD) for the phthalate esters varied between 0.05 and 0.12μgL−1. The inter-day and intra-day relative standard deviations for various phthalate esters at 10μgL−1 concentration level (n=6) using a single fiber were 6.6–7.5% and 8.3–11.1%, respectively. The fiber to fiber repeatabilities (n=4), expressed as relative standard deviation (RSD%), were between 8.9% and 10.2% at 10μgL−1 concentration level. The linear ranges varied between 0.5 and 1000μgL−1. The method was successfully applied to the analysis of the bottled mineral water sample with recoveries from 86 to 107%.

Functionalization of nanomaterials by non-thermal large area atmospheric pressure plasmas: application to flexible dye-sensitized solar cells

A key challenge to the industrial application of nanotechnology is the development of fabrication processes for functional devices based on nanomaterials which can be scaled up for mass production. In this report, we disclose the results of non-thermal radio-frequency (rf) atmospheric pressure plasma (APP) based deposition of TiO2 nanoparticles on a flexible substrate for the fabrication of dye-sensitized solar cells (DSSCs). Operating at 190 °C without a vacuum enclosure, the APP method can avoid thermal damage and vacuum compatibility restrictions and utilize roll-to-roll processing over a large area. The various analyses of the TiO2 films demonstrate that superior film properties can be obtained by the non-thermal APP method when compared with the thermal sintering process operating at 450 °C. The crystallinity of the anatase TiO2 nanoparticles is significantly improved without thermal agglomeration, while the surface defects such as Ti(3+) ions are eliminated, thus providing efficient charge collecting properties for solar cells. Finally, we successfully fabricated a flexible DSSC with an energy conversion efficiency of 4.2% using a transparent plastic substrate. This work demonstrates the potential of non-thermal APP technology in the area of device-level, nano-enabled material manufacturing.

Coassembly of Metal and Titanium Dioxide Nanocrystals Directed by Monolayered Block Copolymer Inverse Micelles for Enhanced Photocatalytic Performance

Functional nanostructures of self-assembled block copolymers (BCPs) incorporated with various inorganic nanomaterials have received considerable attention on account of their many potential applications. Here we demonstrate the two-dimensional self-assembly of anisotropic titanium dioxide (TiO(2)) nanocrystals (NCs) and metal nanoparticles (NPs) directed by monolayered poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymer inverse micelles. The independent position-selective assembly of TiO(2) NCs and silver nanoparticles (AgNPs) preferentially in the intermicelle corona regions and the core of micelles, respectively, for instance, was accomplished by spin-coating a mixture solution of PS-b-P4VP and ex situ synthesized TiO(2) NCs, followed by the reduction of Ag salts coordinated in the cores of micelles into AgNPs. Hydrophobic TiO(2) NCs with a diameter and length of approximately 3 nm and 20-30 nm, respectively, were preferentially sequestered in the intermicelle nonpolar PS corona regions energetically favorable with the minimum entropic packing penalty. Subsequent high-temperature annealing at 550 °C not only effectively removed the block copolymer but also transformed the TiO(2) NCs into connected nanoparticles, thus leading to a two-dimensionally ordered TiO(2) network in which AgNPs were also self-organized. The enhanced photocatalytic activity of the AgNP-decorated TiO(2) networks by approximately 27 and 44 % over that of Ag-free TiO(2) networks and randomly deposited TiO(2) nanoparticles, respectively, was confirmed by the UV degradation property of methylene blue.

Construction of Hierarchical Nanostructured TiO2/Bi2MoO6 Heterojunction for Improved Visible Light Photocatalysis

In this study, Bi2MoO6 hollow microspheres were modified by depositing TiO2 nanoparticles through a simple hydrothermal method. The prepared TiO2/Bi2MoO6 photocatalysts were characterized by scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic performance of the heterostructured catalysts was evaluated by degradation of methylene blue (MB) under visible-light irradiation (lambda>420 nm). The photocatalysts based on nanostructured Bi2MoO6 and TiO2 exhibit much higher photocatalytic activity than the single-phase Bi2MoO6 or TiO2 and the mechanical mixture of Bi2MoO6 and TiO2 for degradation of MB under the same conditions. The results reported in this study provide insight into constructing other heterostructured photocatalysts.

Au-TiO 2 Yolk-Shell Particles for Photocatalysis Application

Abstract Au-TiO2 yolk-shell particles with gold as core and mesoporous TiO2 as shell have been synthesized by deposition of TiO2 nanoparticles onto Au-silica core-shell particles via modified sol-gel method at room temperature followed by the removal of silica midlayer by NaOH treatment. The Au-TiO2 yolk-shell particles exhibit a high colloidal stability, which can be applied as excellent heterogeneous photocatalysts for the photodegradation of the dye Rhodamine B under UV irradiation. The Au-TiO2 yolk-shell particles have shown much higher photocatalytic activity than that of the hollow TiO2 particles without gold.

Deposition of TiO2 nano-particles on wood surfaces for UV and moisture protection

Deposition of TiO2 nanoparticles on wood surface was realised to improve the wood stability against ultraviolet (UV) light and moisture degradation. Photocatalytic activity of TiO2 nanoparticles was utilised for protection of the wood surface. TiO2 nano-particles were achieved by a sol–gel deposition method using EtOH/TiCl4 solution. Dip-coating process and subsequent annealing were used to realise nano-particles on wood surface. This method of deposition was utilised for the conformal covering of the wood structure as demonstrated by morphological investigation of the prepared samples by field emission scanning electron microscopy. Colour change measurements and Fourier transform infrared spectroscopy were used to analyse the lignin and carbonyl degradation of uncoated and coated wood during the UV exposure. Moisture protection of the coated wood was investigated by measuring the contact angle of the distilled water and wood surface. The measurements showed the UV and moisture protection of the TiO2 layer.

Short time deposition of TiO2 nanoparticles on SiC as photocatalysts for the degradation of organic dyes

The deposition of TiO2 nanoparticles on SiC was carried out by mechanical milling under different conditions. SiC–TiO2 samples were used as photocatalysts for the degradation of organic dyes such as methylene blue and rhodamine B. A short time deposition of TiO2 nanoparticles was observed during mechanical milling (2 min at 200 rpm) to cover the SiC particles. The presence of SiC and TiO2 (anatase and rutile) was confirmed by means of X-ray diffraction after thermal treatment at 450 °C. The deposition of TiO2 on SiC was corroborated by scanning electron microscopy analysis; the thickness of the thin layer of TiO2 deposited on SiC increases as the proportion of TiO2 increases. The energy band gap values obtained for these compounds were around 3.0 eV. SiC–TiO2 photocatalysts prepared by mechanical milling exhibited better activity under UV-light irradiation for the degradation of methylene blue and rhodamine B than commercial TiO2 powder (titania P25).

Modified multistep electrophoretic deposition of TiO2 nanoparticles to prepare high quality thin films for dye-sensitized solar cell

In this study, a modified procedure is introduced which consists of multistep process for improving the structure of mesoporous TiO2 films. The films were prepared by electrophoretic deposition (EPD) on FTO (F-SnO2 coated glass). It is shown that high quality TiO2 film can be produced by multistep EPD method. The effect of EPD time on the thickness and density of the films have been investigated. The performance of dye-sensitized solar cells (DSSCs) that were fabricated by improved layer are tested under AM 1.5 simulated sunlight. Finally, the structure and effective parameters of DSSCs that were fabricated by one step and multistep EPD are investigated precisely, using electrochemical impedance spectroscopy.

Combined Factors Influencing the Aggregation and Deposition of nano-TiO2 in the Presence of Humic Acid and Bacteria

This study investigates the contributions of natural organic matter (NOM) and bacteria to the aggregation and deposition of TiO(2) nanoparticles (TNPs) in aquatic environments. Transport experiments with TNPs were conducted in a microscopic parallel plate system and a macroscopic packed-bed column using fluorescently tagged E. coli as a model organism and Suwannee River Humic Acid as a representative NOM. Notably, TNPs were labeled with fluorescein isothiocyanate allowing particles and cells to be simultaneously visualized with a fluorescent microscope. Results from both experimental systems revealed that interactions among TNPs, NOM, and bacteria exhibited a significant dependence on solution chemistry (pH 5 and 7) and ion valence (K(+) and Ca(2+)), and that these interactions subsequently affect TNPs deposition. NOM and E. coli significantly reduced deposition of TNPs, with NOM having a greater stabilizing influence than bacteria. Ca(2+) ions played a significant role in these interactions, promoting formation of large clusters of TNPs, NOM, and bacteria. TNPs transport in the presence of both NOM and E. coli resulted in much less deposition than in the presence of NOM or E. coli alone, indicating a complex combination of interactions involved in stabilization. Generally, over the aquatic conditions considered, the extent of TNPs deposition follows: without NOM or bacteria > with bacteria only > with NOM only > combined bacteria and NOM. This trend should allow better prediction of the fate of TNPs in complex aquatic systems.

Dispersant-assisted low frequency electrophoretically deposited TiO2 nanoparticles in non-aqueous suspensions for gas sensing applications

The effect of dispersant on deposition mechanism of TiO2 nanoparticles at 1Hz under non-uniform AC fields was investigated. It was found that by adding Dolapix to suspension, deposition pattern is drastically changed enabling particles to enter the gap leaving the electrodes intact. Using low frequency AC electrophoretic deposition technique in the presence of dispersant, we succeeded in fabricating gas sensor in less than 2min. Gas sensing measurements were performed in the temperature range of 450–550°C. The results explained that the sensor has good stability in time and repeatability performance toward high response. The maximum sensitivity of about 180 for the TiO2 nanoparticles sensor is observed with 47ppm NO2 gas and the response and recovery times is about 60–150s. The optimum temperature of the gas sensor was obtained in 450°C where sensor showed a linear trend up to 50ppm of NO2 gas. This sensing behavior in un-doped TiO2 as NO2 sensor can be mainly ascribed to the porous structure of the sensing film and its good contacts to the substrate and electrode assembly.

Characterization and evaluation of the photocatalytic properties of wormhole-like mesoporous silica incorporating TiO2, prepared using different hydrothermal and calcination temperatures

TiO2–SiO2 mesoporous materials were synthesised by deposition of TiO2 nanoparticles prepared by the sol–gel method on to the internal pore surface of wormhole-like mesoporous silica. In this work we synthesised wormhole-like mesoporous silica of different surface area by changing the hydrothermal temperature (70, 100, or 130 °C). Subsequent to this, titania solution was deposited on to the inner surface of the pores and this was followed by calcination at different temperatures (400, 600, or 800 °C). The effect of different hydrothermal and calcination temperature on the photocatalytic properties was evaluated. The samples were characterized by N2-sorption, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The effect of different hydrothermal and calcination temperatures on the photocatalytic properties was evaluated by measuring the degradation of methylene blue in aqueous solution under UV light irradiation (mercury lamp, 125 W). The results indicated that appropriate surface area and degree of crystallinity are two important factors for obtaining high photocatalytic efficiency. Samples prepared at a hydrothermal temperature of 100 °C and calcined at 800 °C had the best photocatalytic performance, because of the highest surface area and high crystallinity.

Synthesis of mesoporous nanocrystalline TiO2 films in a premixed H2/O2/Ar flame

The synthesis of mesoporous nanocrystalline TiO2 films in a premixed (in vol %) 12.9/14.4/72.7 H2/O2/Ar flame doped with 0.1% titanium tetraisopropoxide [Ti(OC3H7)4] was studied. Stabilization of the flame and deposition of TiO2 nanoparticles were carried on the plane of a rotating disk. Spatial distributions of temperature and concentrations of major species in the flame were investigated. The applicability of the employed kinetic reaction scheme and the calculation method to the description of the structure of the investigated flame was tested. It was established that this method can be used to synthesize spherical crystalline nanoparticles of the anatase polymorphic form of TiO2 with an average diameter of 12 nm and a narrow size distribution (σ = 1.45), which can be used in the production of solar cells and gas analyzer sensors.

Growth of TiO2 nanorod arrays on reduced graphene oxide with enhanced lithium-ion storage

We demonstrate the synthesis of a sandwich-like nanocomposite by planting rutile TiO2 nanorods onto reduced graphene oxide (RGO) via a modified seed-assisted hydrothermal growth method. The synthetic process consists of functionalization of graphene oxide (GO), followed by hydrolytic deposition of TiO2 nanoparticles on GO and reduction, and finally hydrothermal growth of rutile TiO2 nanorods on RGO. The resultant nanocomposite, i.e. rutile TiO2 nanorod arrays on RGO (TONRAs–RGO), exhibits largely enhanced reversible charge–discharge capacity and rate capability compared to bare TiO2 nanorods (TONRs) due to its unique structure and superior conductivity. The rate performance of the nanocomposite is also better than that of anatase TiO2 nanoparticles. This study will inspire better design of RGO-based nanocomposites for high energy density lithium-ion battery applications.

Electrophoresis Deposition of TiO2 Nanoparticles on Etched Aluminum Foil for Enhanced Specific Capacitance

2011, Volume 15, Issue 1, Pages E1-E3. Electrochem. Solid-State Lett. Lan Sun, Junfu Bu, Wenxi Guo, Yingying Wang, Mengye Wang and Changjian Lin Etched Aluminum Foil for Enhanced Specific Capacitance Nanoparticles on 2 Electrophoresis Deposition of TiO service Email alerting click here in the box at the top right corner of the article or Receive free email alerts when new articles cite this article sign up

Highly porous TiO2 films for dye sensitized solar cells

Highly porous nanoparticle films were investigated as alternative working electrode morphology for the synthesis of dye sensitized solar cells (DSSCs). These films were rapidly assembled by flame synthesis and direct aerosol deposition of TiO2 nanoparticles with high specific surface area. Structural–functional analysis of their properties revealed that the film porosity is a key parameter greatly determining the resulting energy conversion efficiency (η). In fact, aerosol deposition at low substrate temperatures (∼100 °C) led to very high porosity (ε = 98%) and weak film cohesion. These films were easily resuspended upon immersion in the dye and/or electrolyte solutions resulting in very poor performances (η = 0.08%). In contrast, allowing for partial nanoparticle sintering by deposition at moderate temperatures (∼400 °C) decreased the film porosity from 98 to 95% leading to higher mechanical stability and partially preserving the large surface required for dye adsorption. As a result, these films had drastically higher current density (12.2 mA cm−2) and overall performances (η = 5%) representing an 8 times improvement with respect to the best reported for similar highly porous morphologies. Remarkably, their conversion efficiency decreased only slightly with increasing film thickness reaching 4.6% at 128 µm. This unique attribute suggests that high film porosity may inhibit recombination losses enabling utilization of thick films with enhanced light absorption properties.

Deposition mechanisms of TiO2 nanoparticles in a parallel plate system

In this study, a microscope-based technique was utilized to understand the fundamental mechanisms involved in deposition of TiO2 nanoparticles (TNPs). Transport and deposition studies were conducted in a parallel plate (PP) flow chamber with TNP labeled with fluorescein isothiocyanate (FITC) for visualization. Attachment of FITC-labeled TNPs on surfaces is a function of a combination of parameters, including ionic strength (IS), pH and flowrate. Significantly higher deposition rates were observed at pH 5 versus pH 7. This is attributed to the conditions being chemically favorable for deposition at pH 5 as compared to pH 7, as predicted by DLVO theory. Additionally, deposition rates at pH 5 were reduced with IS below 10mM due to the decrease in range of electrostatic attractive forces. Above 10mM, aggregate size increased, resulting in higher deposition rates. At pH 7, no deposition was observed below 10mM and above this concentration, deposition increased with IS. The impact of flowrate was also observed, with decreasing flowrate leading to greater deposition due to the reduction in drag force acting on the aggregate (regardless of pH). Comparisons between experimental and theoretical approximations indicate that non-DLVO type forces also play a significant role. This combination of observations suggest that the deposition of these model nanoparticles on glass surfaces was controlled by a combination of DLVO and non-DLVO-type forces, shear rate, aggregation state, and gravitational force acting on TNPs.

Electrophoretic deposition of TiO2 nanoparticles using organic dyes

Electrophoretic deposition method has been developed for the deposition of TiO2 nanoparticles modified with organic dyes. Alizarin red, alizarin yellow and pyrocatechol violet dyes were used for the dispersion and charging of TiO2 in ethanol and anodic electrophoretic deposition of TiO2 films. The deposition yield was varied by the variation of dye concentration in suspensions and deposition time. Aurintricarboxylic acid dye was used for the deposition of TiO2 from aqueous suspensions. It was found that thin films of pure aurintricarboxylic acid and composite aurintricarboxylic acid TiO2 films can be obtained. The deposition yield was studied by quartz crystal microbalance. Dye film thickness was varied in the range of 0.1–2μm by variation in the deposition time at a constant voltage. The composition of the films and the amount of the deposited material can be varied by the variation of TiO2 and dye concentration in suspensions and deposition time. The films were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and electron microscopy. The deposition mechanisms were discussed. The electrophoretic deposition method offers advantages for the fabrication of dye-sensitized TiO2 films.

Electronic structure of indium tin oxide/nanocrystalline TiO2 interfaces as used in dye-sensitized solar cell devices

Dye-sensitized solar cells are typically prepared under ambient conditions and contamination is inevitably introduced during the fabrication process. Hence, the electronic structure and charge injection properties of the indium tin oxide (ITO)/nanocrystalline titanium dioxide (TiO2) interface was studied by photoemission spectroscopy (PES) in the presence of environmental contaminants. The interface was formed by in situ multi-step electrospray thin film deposition of TiO2 nanoparticles onto ITO substrates cleaned prior in solvent under ambient conditions. In between deposition steps, the samples were characterized with PES yielding the band line-up at the ITO/TiO2 interface. In addition, the band line-up before and after annealing of the TiO2 layer was determined. The results of these measurements have in common that there are only small charge injection barriers between the valence bands of the oxides (∼0–0.2 eV), but more significant barriers for electron injection from TiO2 to ITO (∼0.3–0.5 eV), which has the potential to affect the performance of solar cell device structures. Another focus of the experiments was to investigate whether an earlier reported work function lowering measurement artifact occurring during ultraviolet photoemission spectroscopy (UPS) measurements on environmentally contaminated metal oxide surfaces would affect the characterization of ITO/TiO2 interfaces. For this purpose additional band line-up measurements using low intensity x-ray photoemission spectroscopy (LIXPS) were performed. LIXPS has been demonstrated to not cause the artifact, i.e., can be used to detect its occurrence. The results of these experiments show that the UV-induced work function reduction is not observed on the annealed interface, but that at contaminated interfaces care must be taken during data evaluation to take the artifact into account.

Mechanisms of TiO2 nanoparticle transport in porous media: Role of solution chemistry, nanoparticle concentration, and flowrate

The role of solution chemistry, nanoparticle concentration and hydrodynamic effects in the transport and deposition of TiO2 nanoparticles through porous media has been systematically investigated. Two solution chemistry variables, pH and ionic strength (IS), showed a significant influence on the transport due to their involvement in the aggregation of the nanoparticles and interaction with quartz sand. An electrostatically unfavorable condition for deposition existed at pH 7, at which the greatest retention occurred in the column, likely due to aggregation (>1000nm) and straining effects. Under electrostatically favorable conditions (pH 5) significant elution from the column was observed and attributed to smaller aggregate size (∼300nm) and blocking effects. Nanoparticle concentration was found to contribute to the increased breakthrough of nanoparticles at pH 5 due to blocking and subsequent particle–particle repulsion. Increased flowrate resulted in greater elution of nanoparticles due to hydrodynamic forces acting on aggregates and subsequently contributed to blocking. Overall, a combination of mechanisms including straining, blocking, and DLVO-type forces were involved over the range of solution chemistry and nanoparticle concentrations tested. Consideration of these mechanisms is necessary for improved removal of TiO2 nanoparticles via filtration and reliable prediction of transport of these potentially problematic nanoparticles through the subsurface.