Nanostructured TiO2 Thin Films Research Articles

Effect of annealing temperature on the physical of nanostructured TiO2 films prepared by sol-gel method

This study uses glass substrates to create nanostructured TiO2 thin films employing SolGel method. Afterwards, TiO2 films are annealed in air for two hours at (400, 450, and 500) °C. The XRD tests demonstrate that all films are tetragonal polycrystalline and have orientations equal to those described in the literature. These findings suggest that when the annealing temperature rises, grain size increases. As the annealing temperature is raised, the Full Width at Half Maximum (FWHM) reduces from 0.57° to 0.0.51°, and the dislocation density drops from 45.22 to 39.22.18 nm, respectively. AFM has examined the thin films' surface morphology. The films formed using this method have good crystalline and homogenous surfaces, according to AFM tests. With an increase in annealing temperature, thin films' average particle size, average roughness, and Root Mean Square (RMS) value all drop. The films' optical characteristics. The transmission was over 97% decreased with increasing annealing temperatures. It is found that the band gap decreases from 3.42 to 3.3 eV with increasing annealing temperature. Between 300 and 900 nm, the films' refractive indices range from 2.89 to 2.2.76. With higher annealing temperatures, the films' extinction coefficients fall.

Nanostructured TiO2 thin films sputtered at room temperature as electron transport layer for flexible perovskite solar cell applications: Impact of varying RF power

This work examines the adoption of radio frequency (RF) sputtering at power ranging from 100 to 300 W to deposit nanostructured titanium dioxide (TiO2) thin films on indium tin oxide (ITO)-coated polyethylene terephthalate (PET) flexible substrate (ITO/PET) at room temperature. At higher RF power, X-ray diffraction (XRD) results exhibited evolution from amorphous into crystalline anatase with preferred (101) orientation and the films revealed spherical-like nanostructures with increasing grain size from 15.71 to 21.57 nm. Films transparency decreased from 79% to 70%. Estimated energy gap decreased from 3.57 to 3.36 eV, while refractive index increased from 2.19 to 2.25, denoting a red shift in the films. The thin film deposited at 300 W exhibited high conductivity and mobility of 19.65 × 10−5 Ω−1 cm−1 and 0.30 cm2/Vs, respectively. The film demonstrated its capability as an electron transport layer for flexible perovskite solar cells.

Nanostructured thin films of TiO2 tailored by anodization

Although nanostructured TiO2 layers have been widely prepared by anodization, thin films with thicknesses under 1 μm, over substrate other than Ti foils, with structures beyond the nanopores, had remained a challenge. In this work, such nanostructured TiO2 thin films were synthesized by anodization of Ti films deposited by sputtering on FTO/glass substrates. Anodization was performed in an electrolyte based on 0.6 wt% of NH4F, a graphite cathode and the application of 30 V during lapses ranging from 3 to 14 min. The amorphous TiO2 structures acquired the crystal anatase phase after a post-annealing treatment at 450 °C/4 h. Porous morphologies were observed for anodizing times of 3 and 4 min, sponges were formed with 5 and 6 min and vertical tubular structures were achieved by using 7 up to 9 min; dissolution was observed for longer times. Pore diameters of the structures were in the range of 27 to 47 nm, lengths were within the 330 and 1000 nm interval, transmittance was in the visible range of 70 ± 10%, the energy gap was 3.37 ± 0.02 eV and the wet contact angle was between 20 to 27°. One major contribution of the findings herein developed, is that they can be extended to TiO2 thin films, with a specific nanostructure, grown on a wide gamma of substrates, relevant for particular applications.

Supported MOCVD TiO2 Thin Films Grown on Modified Stainless Steel Mesh for Sensing Applications.

Among semiconductor metal oxides, that are an important class of sensing materials, titanium dioxide (TiO2) thin films are widely employed as sensors because of their high chemical and mechanical stability in harsh environments, non-toxicity, eco-compatibility, and photocatalytic properties. TiO2-based chemical oxygen demand (COD) sensors exploit the photocatalytic properties of TiO2 in inducing the oxidation of organic compounds to CO2. In this work, we discuss nanostructured TiO2 thin films grown via low-pressure metal organic chemical vapor deposition (MOCVD) on metallic AISI 316 mesh. To increase the surface sensing area, different inorganic acid-based chemical etching protocols have been developed, determining the optimal experimental conditions for adequate substrate roughness. Both chemically etched pristine meshes and the MOCVD-coated ones have been studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) microanalysis, and X-ray photoelectron spectroscopy (XPS). We demonstrate that etching by HCl/H2SO4 at 55 °C provides the most suitable surface morphology. To investigate the behavior of the developed high surface area TiO2 thin films as COD sensors, photocatalytic degradation of functional model pollutants based on ISO 10678:2010 has been tested, showing for the best performing acid-etched mesh coated with polycrystalline TiO2 an increase of 60% in activity, and degrading 66 µmol of MB per square meter per hour.

Enhancement of sensitization and electron transfer by kumkum dye in dye-sensitized solar cell applications

An anatase-based nanostructured TiO2 thin film paint was sprayed on FTO conducting glass to create dye-sensitized solar cells. Turmeric (Curcuma longa) and CaCO3 were used as natural sensitizers (DSSCs). FTIR and UV-Vis spectrophotometry was used to analyze the functional groups and optical characteristics of the dyes at absorbing photon energy of the semiconductor thin films, respectively. Both the XRD and UV results show that TiO2 has an anatase phase structure that is consistent with its broadband gap nature. The PL spectra of natural dyes were examined to determine their optical properties and the intensity of PL emission reported a bandgap of 4.72 eV and 4.95 eV respectively. The efficiency of the DSSC using Kumkum dye in ethanol is 0.9%, whereas in DI is 0.2%. Curcumin is a flavonoid polyphenol which is a very effective light-harvesting derivative required for the creation of charge carriers and generation of electric current has been found to be present in turmeric extract and is subjected to the coloring of natural sensitizers which enhance the absorption coefficient. Data Availability StatementThe datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request.

A highly stable room temperature titania nanostructure-based thin film transistor (TFT) alcohol sensor

The present study is concerned with the room temperature field-induced alcohol sensitivity of nanostructured TiO2 thin films in field-effect transistor (TFT) configurations.

Nanostructured TiO2: Analysis and characterization

Nanostructured TiO2 thin films were deposited on quartz glass at room temperature by sol–gel dip coat-ing method. The effects of annealing temperature between 200◦C to 1100◦C were investigated on the structural, morphological, and optical properties of these films. The X-ray diffraction results showed that nanostructured TiO2 thin film annealed at between 200◦C to 600◦C was amorphous trans- formed into the anatase phase at 700◦C, and further into rutile phase at 1000◦C. The crystallite size of TiO2 thin films was increased with increasing annealing temperature. From atomic force microscopy images, it was confirmed that the microstructure of annealed thin films changed from column to nubbly. Besides, surface roughness of the thin films in- creases from 1.82 to 5.20 nm, and at the same time, average grain size as well grows up from about 39 to 313 nm with increase of the annealing temperature. The transmittance of the thin films annealed at 1000 and 1100◦C was reduced significantly in the wavelength range of about 300–700 nm due to the change of crystallite phase. Refractive index and optical high dielectric constant of the n-TiO2 thin films were in- creased with increasing annealing temperature, and the film thickness and the optical band gap of nanostructured TiO2 thin films were decreased.

Large-Scale MOCVD Deposition of Nanostructured TiO2 on Stainless Steel Woven: A Systematic Investigation of Photoactivity as a Function of Film Thickness.

Heterogeneous photocatalysis is considered as one of the most appealing options for the treatment of organic pollutants in water. However, its definitive translation into industrial practice is still very limited because of both the complexity of large-scale production of catalysts and the problems involved in handling the powder-based photocatalysts in the industrial plants. Here, we demonstrate that the MOCVD approach can be successfully used to prepare large-scale supported catalysts with a good photocatalytic activity towards dye degradation. The photocatalyst consisted of nanostructured TiO2 thin film deposited on a stainless steel mesh substrate. The film thickness, the morphological features, and the crystallographic properties of the different portions of the sample were correlated to the position in the reactor chamber and the reaction conditions. The photocatalytic activity was evaluated according to the international standard test ISO 10678:2010 based on methylene blue degradation. The photocatalytic activity is essentially constant (PMB over 40 µmol·m−2·h−1) throughout the film, except for the portion of sample placed at the very end of the reactor chamber, where the TiO2 film is too thin to react properly. It was assessed that a minimum film thickness of 250–300 nm is necessary to reach the maximum photocatalytic performance.

Dip-coating sol–gel preparation and characterization of Rhodamine 6G-doped nanostructured TiO2 thin films on structural and spectroscopic properties

Dip-coating sol–gel preparation and characterization of Rhodamine 6G-doped nanostructured TiO2 thin films on structural and spectroscopic properties

Effect of Both Sn Doping and Annealing Temperature on the Properties of Dip-Coated Nanostructured TiO2 Thin Films

Effect of Both Sn Doping and Annealing Temperature on the Properties of Dip-Coated Nanostructured TiO2 Thin Films

INTERACTION OF TIO2 NANOPARTICLES AND PROTEINS OF AN IMMUNE COMPLEX IN PHOTOLUMINESCENCE BASED BIOSENSOR

Interaction between nanostructured semiconductor thin layers and immune complex based proteins is a fundamental issue of the formation of nanobiointerface in the various biosensors, in particular, optical biosensors. In this work, the main aspects of the interaction between photoluminescent TiO2 nanoparticles and Bovine leucosis virus (BLV) protein gp51, used as a model protein, during the formation of photoluminescence based immunosensor have been discussed. The antigens of gp51 were immobilized on the surface of a nanostructured TiO2 thin film formed on the glass substrates. As a result, an increase of the photoluminescence (PL) signal intensity and PL peak shift from 517 nm to 499 nm were observed. An incubation of TiO2/gp51 structure in a solution containing anti-gp51 antibodies resulted in the backward PL peak shift from 499 nm to 516 nm and decrease of the PL intensity. The main reason of the changes in the PL spectra (i.e. PL maxima shifts and PL intensity variations) as a result of BLV protein gp51 adsorption on the surface TiO2 thin film is an electrostatic interaction between negatively charged surface of TiO2 and positively charged atoms and groups provided by the adsorbed gp51 protein due to the presence of partial uncompensated charges within the proteins.

Phase field model of faceted anatase TiO2 dendrites in low pressure chemical vapor deposition

Anatase TiO2 nanorods with a well-defined ⟨110⟩ texture have been studied using a model-based characterization technique based on a previous modeling framework. Intricate secondary side facet characteristics of tilt angles of 26.5° have been indexed, and a ⟨112⟩ growth direction of the well-aligned facets is identified. These results have not been accessed experimentally but crucial in understanding the nature of the most abundant facets and their structural properties. We find agreement between our results and indirect experimental measurements. Highly exposed {116} facets are found to be responsible for excellent electrochemical surface properties in nanostructured anatase TiO2 thin films.

Cover Feature: Interplay Between Charge Accumulation and Oxygen Reduction Catalysis in Nanostructured TiO2 Electrodes Functionalized with a Molecular Catalyst (ChemElectroChem 14/2021)

The Cover Feature shows the competition between catalytic O2 reduction and reversible proton-coupled charge storage at nanostructured TiO2 thin films, in the presence or absence of an applied potential. More information can be found in the Article by B. Limoges, V. Balland and co-workers.

Surface morphology and optical properties of Ca and Mn doped TiO2 nano-structured thin films

This study was conducted to investigate the impact of Calcium (Ca) and Manganese (Mn) dopants on the optical and surface properties of Titanium dioxide (TiO2) nanomaterial. Ca and Mn doped TiO2 thin films were fabricated by sol–gel spin-coating method. By keeping the doping ratio of Ca constant, Mn was doped at the ratios of 1, 3, and 5%. The morphological, structural and optical properties of the fabricated samples were taken by Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Analysis (EDX), X-Ray Diffraction Method (XRD) and UV–VIS spectroscopy. AFM and SEM analysis revealed that the morphological properties of TiO2 changed depending on the increase in doping ratio of Mn. XRD values obtained from the samples showed that the increases of crystallite size with manganese ions doping into the TiO2 the optical band gap of the samples increased with Ca and Mn dopants. As a result of the investigations, it was determined that Mn doping has significant effects on the morphological and optical properties of TiO2 films and the produced samples can be used in transparent conductive electrode applications, optoelectronic devices, and sensor production.

Synthesis and characterisation of nano TiO2 film for enhancing antireflection properties

ABSTRACT A nanostructured TiO2 thin film was deposited on glass substrate by using sol gel dip-coating method to improve the antireflective property and performance of the solar PV cell. In this way, TiO2 was prepared by using titanium isopropoxide (TIP) as precursor and nitric acid (HNO3) as catalyst and the corresponding structural and optical properties were studied. The film thickness was tailored by varying the withdrawal rate. The X-ray diffraction results showed that TiO2 thin film calcined at 300°C was amorphous, and was transformed into anatase phase at 450°C with crystallite size of 22.6 nm. The microstructure of the film was analysed by Scanning Electron Microscope (SEM) and the elemental composition was confirmed by Energy Dispersive X-Ray Analysis (EDAX). The surface topography was characterised by Atomic force microscopy (AFM) which reveals that the surface has many spikes which confirms the surface is not smooth. The optical properties such as absorption and reflection were investigated by using UV-VIS spectrometer which indicates that the absorption was increased from 1.2% to 1.5% at the wavelength range from 250 to 314 nm and the reflectance was reduced from 23% to 5.7% after the TiO2 deposition and the conversion efficiency was increased from 14.22% to 17.54%.

Effects of Mn doping on the characterization of nanostructured TiO2 thin films deposited via chemical spray pyrolysis method

Nanostructured TiO2:Mn thin films at diverse concentrations of Mn were deposited via chemical spray pyrolysis method (CPM). The XRD patterns hexagonal wurtzite structure with a dominant peak towards (101) plane. The Grain size of the deposited films is about (10.71-12.71) nm with Mn, whereas the strain (%) parameter decrease from 32.34 to 27.26 with Mn. AFM images show the TiO2:Mn effects surface morphology of the film, The grain size was in the area of (91.13), (67.79) and (64.94) nm for the (TiO2, TiO2:2% Mn, TiO2:4% Mn) respectively. Surface roughness of TiO2 Thin films are RSM 16.6 to 3.68 nm, The average transmittance of the samples was 75 to 85% in the visible wavelength range from 300 to 900 nm. The bandgap values were 3.35 eV (undoped) to 3.15 eV (4 % Mn).

Turning Waste into Useful Products by Photocatalysis with Nanocrystalline TiO2 Thin Films: Reductive Cleavage of Azo Bond in the Presence of Aqueous Formate.

UV-photoexcitation of TiO2 in contact with aqueous solutions of azo dyes does not imply only its photocatalytic degradation, but the reaction fate of the dye depends on the experimental conditions. In fact, we demonstrate that the presence of sodium formate is the switch from a degradative pathway of the dye to its transformation into useful products. Laser flash photolysis experiments show that charge separation is extremely long lived in nanostructured TiO2 thin films, making them suitable to drive both oxidation and reduction reactions. ESR spin trapping and photoluminescence experiments demonstrate that formate anions are very efficient in intercepting holes, thereby inhibiting OH radicals formation. Under these conditions, electrons promoted in the conduction band of TiO2 and protons deriving from the oxidation of formate on photogenerated holes lead to the reductive cleavage of N=N bonds with formation and accumulation of reduced intermediates. Negative ion ESI–MS findings provide clear support to point out this new mechanism. This study provides a facile solution for realizing together wastewater purification and photocatalytic conversion of a waste (discharged dye) into useful products (such as sulfanilic acid used again for synthesis of new azo dyes). Moreover, the use of TiO2 deposited on an FTO (Fluorine Tin Oxide) glass circumvents all the difficulties related to the use of slurries. The obtained photocatalyst is easy to handle and to recover and shows an excellent stability allowing complete recyclability.

Optical constants and dispersion energy parameters of Zn-doped TiO2 thin films prepared by spray pyrolysis technique

The present work describes the deposition and investigation of structural and optical characteristics of bare and doped TiO2 thin films. The TiO2 products are obtained through simple and cost effective spray pyrolysis technique (SPT) using titanium (IV) butoxide as Ti precursor. The impact of Zn doping on the crystal structure and phase formation is studied by X-ray diffraction (XRD) analysis. The formation of anatase phase relative to pure TiO2 along with preferred orientation along the [101] direction is confirmed with the help of XRD analysis. Zn doping into TiO2 lattice network leads to an identical diffraction pattern. A deterioration of crystallinity is obtained in crystallite size employing the numerous methods such as Scherrer method, Williamson–Hall, Halder–Wagner and Wagner–Agua analysis in accordance with Zn. In addition, absorbance results obtained from UV–vis spectroscopy has been exerted to examine the optical characteristics. It is noted that the dopant introduction has an impact on the optical properties and the direct band gap value obtained from Tauc relation exhibits a red shift with Zn content. The influence of the Zn doping elements on the optical constants of TiO2 product has been investigated. The dielectric constants, dispersion parameters, loss factor and distribution of volume and surface energy loss of the TiO2 products have been computed as well. The as-prepared nanostructured Zn-doped TiO2 thin films can be used as potential candidates for different optoelectronic devices

Surface, structural and optical properties dependence of Fe-doped TiO2 films deposited onto soda–lime–glass

In this study, pure and Fe doped TiO2 thin films have been prepared via sol-gel method using the tetraethyl-orthotitanate as source of Ti and Fe(III) nitrate as a source of Fe3+ doping. XRD patterns exhibit typical peaks of TiO2 anatase phase. SEM observations confirm the nanometer grain size (below 10 nm) without a defined shape. Optical measurements indicate a transparency in the range 80–100%, it increases with Fe doping level while the energy band gap slightly decreases; 3.36 – 3.28 eV. Wettability test shows a super-hydrophilicity of Fe3+ doped TiO2 thin films and the low contact angle is founded for 0.6%Fe. However, no enhancement in photocatalytic activity of Fe doped TiO2 thin films have been achieved. This may be attributed to sodium diffusion from the substrate. The as-prepared nanostructured Fe-doped TiO2 thin films can be used as potential candidate for self-cleaning due to the super-hydrophilicity character in the visible light.

Modification of the optical properties and nano-crystallinity of anatase TiO2nanoparticles thin film using low pressure O2 plasma treatment

TiO2 nanoparticles (NPs) thin films with a thickness of 50 nm and a core-shell nanostructure were prepared using the spin coating technique and were treated using an inductively coupled O2 plasma at low pressure. While no significant features were observed during pumping, two kinetics can be identified during plasma processing using in situ spectroscopic ellipsometry. For very short plasma treatment times, the removal of solvent-based organic moieties surrounding TiO2 nanoparticles produces a densification of the inorganic TiO2 films. Such mineralization effect by the O2 plasma treatment was confirmed by X-ray photoelectron microscopy. For larger time scales, the average size of TiO2 NPs rises and significant changes of the optical properties occur. While no significant changes in the film nanostructure were observed by Scanning Electron Microscopy, a rise in the crystallite size and an increase in the agglomeration of TiO2 nanoparticles were confirmed by Transmission Electron Microscopy and Atomic Force Microscopy, respectively. The mechanisms involved in such plasma-induced modification of nanostructured TiO2 thin films are discussed in line with the energy fluxes of plasma-generated species.