nano-TiO2 Thin Film Research Articles

Preparation and characterization of axially substituted silicon phthalocyanine-modified nano TiO2 thin films

Nowadays, reaching of industrial wastes containing durable organic pollutants to water resources is one of the important environmental problems. Cost-effective, nontoxic, thermally and chemically stable, light-sensitive photocatalysts are being developed for the removal of these wastes from water resources. Our aim in this study is to synthesize newly bis-[(4-pyrenebutoxy)]phthalocyaninato silicon (Pyrn-C4-SiPc) and bis-[n-(9-anthrylmethyl)-n-methylamino]phthalocyaninato silicon (Anthr-C3-SiPc) molecules and then modify onto TiO2 nanoparticles. The sol-gel method was used during the modification process to achieve synthesis at lower temperatures to obtain nano TiO2 crystals in the anatase form. 10% and 25% concentrations of silicon phthalocyanine-modified TiO2 nanoparticles which are approximately around 5 nm the particle sizes were added to the preparated hybride organic-inorganic polymer network, and were applied to the glass surface by spray method. The resulting coatings’ thicknesses, photocatalytic activities, and optical, physical, morphological, and mechanical properties were tested. The adhesion of the coatings sprayed onto the glass surface was measured as 5B The coatings created were found to have high hardness and resistance in the tests conducted. This research successfully developed photocatalytic hybrid nanocomposite films that are highly transparent with 90% light transmittance exhibit robust photocatalytic activity, and remain color-stable.

UV-reflecting sintered nano-TiO2 thin film on glass for anti-bird strike application

ABSTRACT A nanocrystalline TiO2 glass coating was developed by sintering sol–gel derived thin film at 450°C. FTIR spectroscopy confirmed the absence of hydroxide gel and unreacted precursor as well as the presence of TiO2. The crystalline phase was predominantly anatase as identified from the XRD measurement and the crystallite size obtained from Scherrer’s equation was 166 nm. This was in good agreement with the TiO2 nanoparticle size of 148 nm obtained from BET adsorption experiment. The approximate BET surface coverage was 10.38 m2 g−1 and the total pore volume was 0.02 cc g−1. Most importantly, the sintered TiO2 coated quartz glass showed a significant increase of 27.8% in UV reflectance, as obtained from UV-vis measurement and subsequent Kubelka–Munk function. This result is particularly advantageous to prevent bird-strike against high-rise glass buildings and windows.

Improved carrier transport in Mn:ZnSe quantum dots sensitized La-doped nano-TiO2 thin film**Project supported by the Natural Science Foundation of Hebei Province, China (Grant No. E2017203029).

Mn:ZnSe/ZnS/L-Cys core-shell quantum dots (QDs) sensitized La-doped nano-TiO2 thin film (QDSTF) was prepared. X-ray photoelectron spectroscopy (XPS), nanosecond transient photovoltaic (TPV), and steady state surface photovoltaic (SPV) technologies were used for probing the photoelectron behaviors in the Mn-doped QDSTF. The results revealed that the Mn-doped QDSTF had a p-type TPV characteristic. The bottom of the conduction band of the QDs as a sensitizer was just 0.86 eV above that of the La-doped nano-TiO2 thin film, while the acceptor level of the doped Mn2+ ions was located at about 0.39 eV below and near the bottom of the conduction band of the QDs. The intensity of the SPV response of the Mn-doped QDSTF at a specific wavelength was ∼2.1 times higher than that of the undoped QDSTF. The region of the SPV response of the Mn-doped QDSTF was extended by 191 nm to almost the whole visible region as compared with the undoped QDSTF one. And the region of the TPV response of the Mn-doped QDSTF was also obviously wider than that of the undoped QDSTF. These PV characteristics of the Mn-doped QDSTF may be due to the prolonged lifetime and extended diffusion length of photogenerated free charge carriers injected into the sensitized La-doped nano-TiO2 thin film.

Laser wavelength and energy effect on optical and structure properties for nano titanium oxide prepared by pulsed laser deposit

Nano TiO2 thin films on glass substrates were prepared at a constant temperature of (373 K) and base vacuum (10-3 mbar), by pulsed laser deposition (PLD) using Nd:YAG laser at 1064 nm wavelength. The effects of different laser energies between (700-1000)mJ on the properties of TiO2 films was investigated. TiO2 thin films were characterized by X-ray diffraction (XRD) measurements have shown that the polycrystalline TiO2 prepared at laser energy 1000 mJ. Preparation also includes optical transmittance and absorption measurements as well as measuring the uniformity of the surface of these films. Optimum parameters have been identified for the growth of high-quality TiO2 films.

Enhanced transient photovoltaic characteristics of core–shell ZnSe/ZnS/L-Cys quantum-dot-sensitized TiO2 thin-film**Project supported by the Natural Science Foundation of Hebei Province, China (Grant Nos. E2013203296 and E2017203029).

Photoanodic properties greatly determine the overall performance of quantum-dot-sensitized solar cells (QDSCs). In the present report, the microdynamic behaviors of carriers in the nanocomposite thin-film, a ZnSe QD-sensitized mesoporous La-doped nano-TiO2 thin-film, as a potential candidate for photoanode, are probed via nanosecond transient photovoltaic (TPV) spectroscopy. The results confirm that the L-Cys ligand has a dual function serving as a stabilizer and molecular linker. Large quantities of interface states are located at the energy level with a photoelectric threshold of 1.58 eV and a quantum well (QW) depth of 0.67 eV. This QW depth is approximately 0.14 eV deeper than the depth of QW buried in the ZnSe QDs, and a deeper QW results in a higher quantum confinement energy. A strong quantum confinement effect of the interface state may be responsible for the excellent TPV characteristics of the photoanode. For example, the peak intensity of the TPV response of the QD-sensitized thin-film lasts a long time, from 9.40 × 10−7 s to 2.96 × 10−4 s, and the end time of the PTV response of the QD-sensitized thin-film is extended by approximately an order of magnitude compared with those of the TiO2 substrate and the QDs. The TPV characteristics of the QD-sensitized thin-film change from p-type to n-type for the QDs before and after sensitizing. These properties strongly depend on the extended diffusion length of the photogenerated carries and the reduced recombination rate of photogenerated electron-hole pairs, resulting in prolonged carrier lifetime and an increased level of electron injection into the TiO2 thin-film substrate.

Atomic layer deposition of nano-TiO2 thin films with enhanced biocompatibility and antimicrobial activity for orthopedic implants.

Titanium (Ti) and its alloys have been extensively used as implant materials in orthopedic applications. Nevertheless, implants may fail due to a lack of osseointegration and/or infection. The aim of this in vitro study was to endow an implant surface with favorable biological properties by the dual modification of surface chemistry and nanostructured topography. The application of a nanostructured titanium dioxide (TiO2) coating on Ti-based implants has been proposed as a potential way to enhance tissue-implant interactions while inhibiting bacterial colonization simultaneously due to its chemical stability, biocompatibility, and antimicrobial properties. In this paper, temperature-controlled atomic layer deposition (ALD) was introduced for the first time to provide unique nanostructured TiO2 coatings on Ti substrates. The effect of nano-TiO2 coatings with different morphology and structure on human osteoblast and fibroblast functions and bacterial activities was investigated. In vitro results indicated that the TiO2 coating stimulated osteoblast adhesion and proliferation while suppressing fibroblast adhesion and proliferation compared to uncoated materials. In addition, the introduction of nano-TiO2 coatings was shown to inhibit gram-positive bacteria (Staphylococcus aureus), gram-negative bacteria (Escherichia coli), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus), all without resorting to the use of antibiotics. Our results suggest that the increase in nanoscale roughness and greater surface hydrophilicity (surface energy) together could contribute to increased protein adsorption selectively, which may affect the cellular and bacterial activities. It was found that ALD-grown TiO2-coated samples with a moderate surface energy at 38.79 mJ/m2 showed relatively promising antibacterial properties and desirable cellular functions. The ALD technique provides a novel and effective strategy to produce TiO2 coatings with delicate control of surface nanotopography and surface energy to enhance the interfacial biocompatibility and mitigate bacterial infection, and could potentially be used for improving numerous orthopedic implants.

Photoelectron characteristics of ZnSe quantum dots-sensitized mesoporous La-doped nano-TiO2 film

In the paper, the core-shell ZnSe quantum dots (QDs)-sensitized mesoporous La-doped nano-TiO2 thin film is prepared by a direct adsorption method. Photoelectron characteristics, photogenerated carriers transport mechanism, and microstructure of the QDs-sensitized nano-TiO2 thin film are probed via the stationary surface photovoltaic (SPV) and the transient photovoltaic technologies, supplemented by the Brunauer-Emmet-Teller adsorption isotherm technique, scanning electron microscope, Fourier transform infrared (FT-IR) absorption spectrum, and ultraviolet-visible (UV-VIS) absorption spectrum. The experimental results confirm that the surface of the nano-TiO2 film is covered with the ZnSe QDs with smaller particles by a chemical absorbing way, resulting in denser composite film of the QDs and the mesoporous nano-TiO2 than the nano-TiO2 film. In our experiment, the adsorption quantity of ZnSe QDs on nano-TiO2 film can be controlled effectively. The results show that ligand L-Cys capped at the outer layer of ZnSe QDs plays an important role in the sensitization process. Specifically, the peak of SH in the ligand disappears at 2552 cm-1 in the FT-IR spectrum of the ZnSe QDs capped by the ligand as a stabilizer. This indicates that the SH bond is broken. In the meantime, the peak of the CS stretching vibration in the ligand shifts from 638 cm-1 to 663 cm-1 due to the formation of ZnS bond. These imply that the core-shell ZnSe/ZnS/L-Cys QDs are obtained. On the other hand, according to the peak of COOH stretching vibration disappearing at 1600 cm-1 in the FT-IR spectrum of the core-shell QDs-sensitized mesoporous nano-TiO2 film, the unsaturated Ti atoms on the surface of the TiO2 film are bonded to carboxy groups from the ligand capped at the QDs. That is, the ligand acts as a bridge between the QDs and the nano-TiO2 film for achieving the sensitization. Some excellent photovoltaic characteristics of the composite film are found as follows. 1) The SPV responses of the QDs-sensitized film appear in a wavelength region of 300 nm to 800 nm (UV-VIS-Near-IR), causing the region of SPV response to enlarge about 200 nm over that of the ZnSe QDs, and 400 nm over that of the nano-TiO2 thin film. 2) The QDs-sensitized film displays an n-type photovoltaic characteristic that is different from that of the QDs. This may be more favorable for transferring those carriers from the film surface to the photo-anode material. 3) Both the separation rate and the diffusion length of photogenerated electron-hole pairs are obviously increased, and the lifetime of free charge carriers in the ZnSe QDs-sensitized film prolongs about an order of magnitude over that of the nano-TiO2 film and ZnSe QDs.

Synthesis of Nano-TiO2 Thin Films by Sol-gel Dip-coating Method

Synthesis of Nano-TiO2 Thin Films by Sol-gel Dip-coating Method

The effect of grafting a nano-TiO2 thin film on physical and mechanical properties of cellulosic natural fibers

This study aims at functionalizing flax fibers by grafting an amphiphilic TiO2 thin film. The film was created on the fiber by the Sol–Gel technique. The fibers were firstly primed to reach a minimum possible roughness, and then were coated using the dip-coat method. The crystalline structure and the morphology of the TiO2 particles, and, the TiO2-grafted film were determined using X-ray diffraction, and Transmission Electron Microscopy. Mechanical properties of the TiO2-grafted flax strands were investigated by a tensile test. Dynamic contact angle tensiometer was used to probe the differences between wettability of the TiO2-grafted and non-grafted flax strands. The results show that the particles obtained from the Sol–Gel technique created a 100 nm-thick film of TiO2 in the anatase form. The statistical evaluation of the tensile tests exhibits a significant improvement in mechanical properties of the TiO2-grafted flax strands. Moreover, the TiO2 coated flax fibers show a wide range of wetting angles in comparison with the other samples.

Efficient application of nano-TiO2 thin films in the photocatalytic removal of Alizarin Yellow from aqueous solutions

The aim of this investigation is to obtain thin films of nano-TiO2 on a borosilicate glass substrate using sol–gel template method. The thin film was immobilized with and without polyethylene glycol as filler media and annealed at 500°C. Further, thin films were characterized by the IR, XRD, XRF and XPS analytical methods. The surface morphology of these films was obtained by the FE-SEM images and the BET specific surface area and pore sizes were obtained. The nano-TiO2 was, perhaps, formed a nanopillar onto the substrate. The thin films were successfully employed in the photocatalytic degradation of Alizarin Yellow (AY), an azo dye, from aqueous solutions using the UV-light irradiation under batch reactor operations. Various physico-chemical parametric studies, viz., effect of pH, Alizarin Yellow concentration and interfering ions were studied to deduce the mechanism involved in photocatalytic degradation of this pollutant. The time dependence degradation of Alizarin Yellow was provided to demonstrate the kinetics of degradation of this pollutant from aqueous solutions. It was observed that the degradation of Alizarin Yellow followed pseudo-first-order rate kinetics. Study was further extended with total organic carbon measurement using TOC analyser to demonstrate an apparent mineralization of Alizarin Yellow from aqueous solutions. The presence of several interfering ions or even OH scavengers suppressed the photo-catalytic action of thin films in AY degradation from aqueous solutions.

TiCl4 assisted formation of nano-TiO2 secondary structure in photoactive electrodes for high efficiency dye-sensitized solar cells

A new kind of photoactive electrodes with nanocrystalline TiO2 (nano-TiO2) secondary structure is successfully prepared via a simple method of adding a small amount of TiCl4 2-propanol solution in conventional nano-TiO2 paste to form micro-sized nano-TiO2 aggregates. The benefits of this special structure include improved optical absorption, increased light scattering ability, and enhanced electron transport and collection efficiency. Dye-sensitized solar cells (DSCs) based on these photoactive electrodes show improved performance. The power conversion efficiency of the cells can be increased from 5.03% to 7.30% by substituting 6 μm conventional nano-TiO2 thin film with the same thickness of as-prepared nano-TiO2 aggregates film in the photoactive electrodes. A higher power conversion efficiency of the cells can be obtained by further increasing the thickness of the nano-TiO2 aggregates film.

Two-Membrane-Pieces Sensitizing Technology and Cyanines Sensitized Nano-TiO<sub>2</sub> Materials

Two-membrane-pieces sensitizing method and the corresponding equipments were developed to prepare cyanines sensitized nanoTiO2 photo anode materials. The cyanines were synthesized from N-p-carboxybenzyl-2,3,3-trimethyl-3H-indoleninium-5-sulfonate potassium and squaric acid or 2-chloro-1-formyl-3-(hydroxymethylene) cyclohex-1-ene. The maximum UV-Vis absorption wavelengths of them were 631 nm and 782 nm, respectively. The nanoTiO2 thin films were prepared on ITO conductive glass from tetrabutyl titanate by sol-gel technique, and were sensitized with the dyes by two-membrane-pieces dye sensitizing method or immersion sensitizing method. Compared with traditional immersion sensitizing method, two-membrane-pieces sensitizing method was an environmentally friendly and economical process due to less dye consumption and less waste formed.

Preparation and photo-catalytic activity of TiO2-coated medical stone-based porous ceramics

Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO2 thin films were loaded on the carrier by chemical liquid deposition method using titanium tetrachloride as a precursor. The micro-morphology and microstructure of the synthesized samples were characterized using X-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, and mercury injection method. The photo-catalytic activity of the TiO2 thin films was investigated by degrading formaldehyde. The main crystalline phase in the TiO2 thin films calcined at 550°C is anatase with the average particle size about 10 nm. The specific surface area of the carrier-coated nano-TiO2 increases from 3.68 to 5.32 m2/g. The formaldehyde removal rate of the TiO2/medical stone-based porous ceramics irradiated under an ultraviolet lamp for 120 min reaches 85.6%.

Synthesis of highly active thin film based on TiO2 nanomaterial for self-cleaning application

Highly active self-cleaning surfaces were prepared from hydrothermally treated TiO2 nanomaterials for different times (0, 12, 24 and 36h) under acidic condition. TiO2 thin films were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). TiO2 thin film (hydrothermal 24h) exhibited hybrid morphology from accumulated plates, clusters, rods and spheres. The photo self-cleaning activity in term of quantitative determination of the active oxidative species (OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results show that, the highly active thin film is the hydrothermally treated for 24h at 200°C. The structural, morphology and photoactivity properties of nano-TiO2 thin films make it promising surfaces for self-cleaning application. Mineralization of commercial textile dye (Remazol Red RB-133, RR) from highly active TiO2 thin film surface was applied. Moreover, the durability of this nano-TiO2 thin film (hydrothermal 24h) was studied.

Preparation, Microstructure and Photocatalytic Performance of the Anatase Nano-TiO2 Thin Film

Preparation, Microstructure and Photocatalytic Performance of the Anatase Nano-TiO2 Thin Film

Simultaneous improvement of photocatalytic and superhydrophilicity properties of nano TiO2 thin films

Anatase TiO2 nano thin films were prepared on glass substrates by sol–gel dip coating method using Tween-80 as a surfactant, TiCl4 as the Ti precursor, and ethanol as a solvent. Atomic force microscopy, X-ray diffraction, and UV–Vis. photospectrometery experiments were performed to analyze the surface, structural and optical characteristics of the films. The effects of chemical aging time on the morphology, photocatalytic and superhydrophilicity behaviors of the films were studied. We show there is an optimum aging time at 2h which photocatalytic and superhydrophilicity properties are at their maximum values simultaneously. This is useful in the self-cleaning industry.

Surface Structure and Photocatalytic Activity of Nano-TiO2 Thin Film for Selective Oxidation

Controlled titanium dioxide (TiO2) thin films were deposited on stainless steel surfaces using the flame-aerosol synthetic technique, which is a one-step coating process that does not require further calcination. Solid state characterization of the coatings was conducted by different techniques, including X-ray diffraction (XRD) spectrum, scanning electron microscope, and atomic force microscope. The coated thin films were used in a gas phase photoreactor for the partial oxidation of hydrocarbons to alcohols and ketones as an alternative production method for the highly sought oxygenates. For this purpose, the oxidation reaction of cyclohexane to form cyclohexanol and cyclohexanone was chosen as a model reaction. The effects of the film thickness, anatase-to-rutile ratio, and particle morphology on the reactivity of the catalyst were studied. Experimental results revealed that there is an optimal film thickness (between 400 and 700 nm) for the photooxidation process that gave a maximum rate of reaction. The yield and selectivity of TiO2 increased with the increase of the film thickness up to 350–400 nm. The activity decreased with a further increase in thickness. The influence of the crystallographic structure of TiO2 on the partial oxidation of cyclohexane showed that the catalyst efficiency increased almost linearly with the increase of the anatase fraction between 20 and 95%. The coating technique that formed highly porous and soft aggregated TiO2 thin films with rough morphology showed lower photoactivity than the technique that formed fine particle and transparent thin film.

The Cytocompatibility of Nano-TiO2 Thin Film Fabricated by Layer-by-Layer Assembly Technique

Nanosized TiO2 with suitable dimensions has been observed to enhance the functions of bone cells; however, the most effective type of nano-TiO2 remains unknown. The Layer-by-Layer (LBL) self-assembly technique has been wildly used to fabricate multilayer thin films of controlled composition, thickness, and architecture. Therefore, to find an appropriate material for orthopedic surgical usage, this study investigates the cytocompatibility and cell activity (using MC-3T3-E1 cells) of nano-TiO2 thin films fabricated by LBL. Four types of nano-TiO2 thin films were synthesized. Surface roughness w measured by field emission scanning electron microscopy (SEM). Hydrophilicity was measured using the contact angle meter. Cell attachment to the materials was observed using SEM. Fluorescent dyes were used to observe the generation of reactive oxygen species and DNA damage. Apoptosis was measured through lactate dehydrogenase leakage assay. The 2-(4,5-dimethyl-2-thiazol-2-yl)-3,5-diphenyl-2H-tetrazolium (MTT) assay was used to determine the viability of the cells attached to the materials. This new film was found to produce better cell proliferation and function; it is comparatively cytocompatible, and therefore may be a better material for orthopedic surgery.

Properties and Photocatalysis of Nanostructured Titania Prepared by Sol-Gel Method for Solar Hydrogen Production

Photoelectrochemical (PEC) devices based on Fe-doped and Pt-loaded nanostructured- TiO2 films acting as working electrodes were fabricated for solar hydrogen production. Anatase nanocrystalline titania (nano-TiO2) thin films were deposited on glass slides and Ti metal sheet substrates by a sol-gel dip-coating method. The sol-gel of nano-TiO2 was prepared in nitrogen atmosphere using a home-made nitrogen dry box and titanium tetraisopropoxide Ti[OCH(CH3)2]4 was used as a precursor. The effects of annealing temperatures on the crystallite size and the phase transformation also were investigated. The diameters of the particles in the rage of 12 nm were obtained in different methods of making the sol-gels and different annealing temperatures. Photoelectrochemical (PEC) devices consist of the Fe-doped and Pt-loaded TiO2 films as working electrodes, Pt as counter electrodes, 1.0 M KOH as electrolyte, and Nafion Perfluorinated membrane as a proton exchange membrane. The maximum photocurrent density occurred of 0.80 mA/cm2 without an external applied bias potential under irradiation of 100 mW/cm2 corresponding with photoconversion efficiency of 0.98 %. Impurity and undesired phases may be the cause of electron-hole recombination that results in lowering photocatalytic activity.

纳米TiO2薄膜的低温等离子体制备技术

纳米TiO₂薄膜的低温等离子体制备技术