Nanostructured TiO2 Films Research Articles

Nanostructured TiO2-X/CuXO-based electrochemical sensor for ultra-sensitive glyphosate detection in real water samples

Glyphosate, a widely employed non-selective pesticide for enhancing crop productivity through weed control, poses significant health and environmental concerns due to its potential link to chronic diseases, cancers, and disruptions in natural symbiotic relationships. Quantifying glyphosate values becomes imperative for effective monitoring and mitigation of associated risks. In response, a novel electrochemical sensor was developed utilizing nanostructured TiO2 films modified with Ti3+ ions and copper oxides for precise detection and quantification of glyphosate in real water samples. The nanotubular structure, synthesized via potentiostatic anodization, underwent further modification through cathodic reduction of Ti4+ to Ti3+ ions and copper electrodeposition. Under optimal experimental conditions, the sensor exhibited a notable ability to detect glyphosate traces by inhibiting peak current in Differential Pulse Voltammetry (DPV). It achieved low limits of detection (LOD = 0.34 pmol/L) and quantification (LOQ = 0.70 pmol/L) within a linear working range of 0.55 to 1000.00 pmol/L. The sensor demonstrated robust stability and excellent precision (repeatability and intermediate precision) without significant variations in analytical response and yielded recovery rates ranging from 91.06 to 99.38 %. These promising results underscore the sensor’s potential application for detecting glyphosate in real aquatic matrices, contributing to effective environmental monitoring and health protection.

Effect of time and voltage on the morphology of TiO2 films produced by anodization

This study investigates the influence of various anodic oxidation parameters on the photocatalytic activities of the nanostructured titanium dioxide (TiO2) films. TiO2 films were prepared by anodic oxidation of titanium substrate using 1 M Na2SO4 / 5 wt. % NH4F electrolyte, and then annealed at 500 °C. Anatase appears in all calcined samples. The anodic oxidation process was performed in two steps at different voltages (5–80 V) and times (15–480 min) to reveal the relationship between the surface morphologies, wettability and photocatalytic properties. The results showed that the voltage and anodization time can play important role in the surface morphology of nanostructured TiO2 films and thus in various properties. While 40 V showed the most efficient photocatalytic degradation among voltage values, 60 min was the most efficient time for photocatalytic degradation efficiency and lowest contact angle. In addition, a pore area fraction of 39.54%, equal diameter of 96.81 nm, and circularity of 66.7% were obtained from image analysis of the 60-min anodized sample. While increasing the voltage and time benefited up to a point in terms of photocatalytic efficiency, changes in morphology had a negative effect after a point. At low voltage and time values, small pore diameters result in low photocatalytic properties. This titania can be readily utilize to meet application expectations in areas such as gas sensors, photocatalysis and photovoltaic cells.

Photoelectrochemical properties of anatase TiO2 nanostructures prepared by hydrothermal method: Effect of illumination and external bias on charge transport

A systematic study of photoelectrochemical properties in terms of carrier transport was conducted for TiO2 nanostructure films fabricated on Ti foil at different temperatures (130 °C–210 °C) through alkaline hydrothermal technique, along with the morphological, structural, and optical properties. For samples, the morphology transformed from nanosheets to nanowires, the phase converted from bi-phase of brookite and anatase to pure anatase along with the reduction in the amount of oxygen vacancies as temperature increases. Among them, the dark blue bi-phased TiO2 (brookite and anatase) prepared at 130 °C of hydrothermal treatment (TiO2-130) with nanosheets morphology displayed the optimum photoelectrochemical performance with the highest photocurrent density of 265 μA/cm2 at 1 V (vs. Ag/AgCl), largest carrier density of 1.809 × 1019cm−3 and narrowest space charge region of 11.73 nm. Besides, the large reduction in charge transfer resistance and the width of space charge region caused by simulated solar illumination facilitate the charge transport in photoelectrode especially the TiO2-130 with the largest reduction, indicating the great influence of illumination on carrier dynamics. Moreover, the external bias caused the reduction of resistance under irradiation, the increase in the resistance in the dark. Importantly, the TiO2-210 showed p-type conductivity under illumination inferred from the negative slope of Mott-Schottky plots, which is first observed and further confirm the influence of light on the charge transfer process.

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.

Interfacial electron transfer of perylenes: Influence of the anchor binding mode.

Interfacial electron transfer (IET) through saturated single-linker and dual-linker groups from a perylene chromophore into nanostructured TiO2 films was studied by ultrafast spectroscopy. Perylene chromophores with one and two propanoic acid linker groups in the peri and ortho positions were investigated. In comparison to previously studied perylenes bound via unsaturated acrylic acid linkers, the chromophores with saturated linkers showed bi-exponential IET dynamics. Two distinct transfer times were observed that indicate the presence of two concurrent binding modes. A comparison between ortho- and peri-substituted sensitizers resulted in slower IET dynamics and weaker electronic coupling for ortho substitution. Finally, IET from sensitizers with saturated linker groups is neither promoted nor hindered by a second linker group. This indicates that only one of the two linkers binds covalently to the surface. This study reveals the importance of the anchor-binding mode and design considerations of the linker for regulating IET.

TiO2-UV detection under different types of acids and rinsing process for films preparation

Titanium dioxide (TiO2) films were prepared by the sol–gel method under different types of acids. Effect of hydrochloric acid (HCl), nitric acid (HNO3) and nature-based solutions (NBS) under ultraviolet (UV) detection of films were investigated. Films were coated by dip coating on glass substrate. Moreover, TiO2 films were compared properties on water rinsing (Ri) and without rinsing (WRi) processes. The phase structure of prepared samples was characterized by means of X-ray powder diffraction (XRD). The results confirm that films were highly crystalline anatase TiO2 and free from other phases of titanium dioxide. For the optical property, the transmittance (%T) observed sharp rise in the violet-ultraviolet transition region and a maximum transmittance of ~80%. Photocurrents were measured under UV intensity of 260 mWcm–2 and DC bias voltage of -20 – 20 volts (V). The results observed that currents increased as bias voltage increased. Current - Voltage (I-V) curves observed different slopes under the different of acids and rinsing process. The photocurrent of TiO2-NBS-Ri was greater than TiO2-HCl-WRi and TiO2-HNO3-WRi of 10 and 20 times; respectively. These findings suggest that the significant effect of the acid and rinsing process on crystalline, morphological, optical, and electrical properties of nanostructured TiO2 films would be useful for applying the device in UV photoelectric detection.

Growth of Nanocolumnar TiO2 Bilayer by Direct Current Reactive Magnetron Sputtering in Glancing-Angle Deposition Configuration for High-Quality Electron Transport Layer.

The electron transport layer (ETL) plays a crucial role in solar cell technology, particularly in perovskite solar cells (PSCs), where nanostructured TiO2 films have been investigated as superior ETLs compared to compact TiO2. In this study, we explored the nanocolumnar growth of TiO2 in the anatase phase for bilayer thin films by DC reactive magnetron sputtering (MS) technique and glancing-angle deposition (GLAD). For the growth of the compact TiO2 layer, it was found that the crystalline quality of the films is strongly dependent on the sputtering power, and the samples deposited at 120 and 140 W are those with the best crystalline quality. However, for the nanocolumnar layer, the reactive atmosphere composition determined the best crystalline properties. By optimizing the growth parameters, the formation of TiO2 nanocolumns with a cross-sectional diameter ranging from 50 to 75 nm was achieved. The average thickness of the films exceeded 12.71 ± 0.5 µm. All nanostructured films were grown at a constant GLAD angle of 70°, and after deposition, the measured inclination angle of the nanocolumns is very close to this, having values between 68 and 80°. Furthermore, a correlation was observed between the quality of the initial layer and the enhanced growth of the TiO2 nanocolumns. All bilayer films are highly transparent, allowing light to pass through up to 90%, and present a band gap with values between 3.7 and 3.8 eV. This article offers the experimental parameters for the fabrication of a nanocolumnar TiO2 using the magnetron sputtering technique and the glancing-angle deposition configuration.

Photocatalytic Degradation of Pharmaceutical Trimethoprim in Aqueous Solution over Nanostructured TiO2 Film Irradiated with Simulated Solar Radiation

Pharmaceuticals are characterized by a wide range of physical, chemical, and biological properties and functionalities that contribute to their inherent complexity as compounds. Unfortunately, human carelessness during the production, use, and disposal of these compounds results in their presence in the environment. This study utilized a nanostructured TiO2 film on a glass ring at the bottom of a reactor and simulated a solar radiation lamp as the radiation source for both photocatalytic and photolytic experiments, with the aim of unraveling the mechanism behind the degradation of trimethoprim (TMP), a pharmaceutical compound. This approach provides a novel perspective on the role of TiO2 in the degradation of pharmaceuticals and could pave the way for more efficient and sustainable wastewater treatment methods. Scavenger studies were carried out using isopropanol, ammonium oxalate, and triethanolamine to examine the photocatalytic mechanism. Isopropanol and triethanolamine were found to impede the photocatalytic degradation of TMP, highlighting the significance of hydroxyl radicals and positive holes in the degradation process, while no inhibition was observed in the presence of ammonium oxalate. The complete degradation of TMP through photocatalysis under simulated solar radiation was observed in ultra-pure water in fewer than 3 h, as indicated by the results. Our findings suggest that utilizing natural solar radiation as a source of UV-A radiation in reactor configurations based on this approach holds promise for cost-effective pharmaceutical degradation treatment in wastewater treatment plants. The practical potential of this approach is supported by the results obtained under simulated solar radiation with an irradiation intensity in the UV-A region of 33 ± 2 W/m2.

The influence of hydrothermal treatment on TiO2 nanostructure films transformed from titanates and their photoelectrochemical water splitting properties

Anatase non-stoichiometric TiO2 nanostructure films transformed from titanates were fabricated using the alkaline hydrothermal method at different treatment durations. The field emission scanning electron microscopy (FESEM) images demonstrated the morphological change of TiO2 from nanosheets to nanowires. The X-ray diffraction (XRD) patterns confirmed the anatase phase for TiO2 nanostructures. The UV–vis-NIR measurement indicated the decline in visible light absorption with increasing treatment duration. For the photoelectrochemical (PEC) measurement, four hours hydrothermal synthesis TiO2 annealed in air at 500 °C for 90 min showed the optimal photocurrent response with the maximum photocurrent density of 149.1µA/cm2 at 0.8 V vs. Ag/AgCl, which is attributed to the narrow bandgap (3.22 eV), improved carrier density (4.806×1018 cm−3) and longest lifetime of carriers (3.2 ms). Thus, nanosheet morphology was found to be more superior than nanowire morphology and a relatively short hydrothermal treatment duration was beneficial to PEC water splitting properties. In addition, for superior PEC performance, appropriate nanosheet density and surface area are necessary. The results demonstrated that TiO2 nanostructures transformed from titanates could be used for PEC application and the PEC characteristics could be tuned and modified for better water splitting performance.

Photocatalytic degradation of gaseous pollutants on nanostructured TiO2 films of various thickness and surface area

This work deals with the preparation of TiO2 nanoparticulate layers of various mass (0.05 mg/cm2 to 2 mg/cm2) from three commercial nanopowder materials, P90, P25 and CG 300, their characterisation (profilometry, BET and SEM) and evaluation of their photocatalytic activity in the gaseous phase in a flow-through photoreactor according to the ISO standard (ISO 22197-2). Hexane was chosen as a single model pollutant and a mixture of four compounds, namely acetaldehyde, acetone, heptane and toluene was used for the evaluation of the efficiency of simultaneous removal of several pollutants. A linear dependence between the layer mass and the layer thickness for all materials was found. Up to a layer mass 0.5 mg/cm2, the immobilisation P90 and P25 powder did not result in a decrease in BET surface area, whereas with an increase in layer mass to 1 mg/cm2, a decrease of the BET surface was observed, being more significant in the case of P90. The photocatalytic conversion of hexane was comparable for all immobilised powders up to a layer mass of 0.5 mg/cm2. For higher layer mass, the photocatalytic conversion of hexane on P25 and P90 differ; the latter achieved about 30% higher conversion. In the case of the simultaneous degradation of four compounds, acetaldehyde was degraded best, followed by acetone and toluene; the least degraded compound was heptane. The measurement of released CO2 revealed that 90% of degraded hexane was mineralised to CO2 and water while for a mixture of 4 VOCs, the level of mineralisation was 83%.Graphical abstract

Visible Light Reductive Photocatalysis of Azo-Dyes with n-n Junctions Based on Chemically Deposited CdS.

New composite photocatalysts have been obtained by chemical bath deposition of CdS on top of either nanostructured crystalline ZrO2 or TiO2 films previously deposited on conductive glass FTO. Their morphological, photoelectrochemical and photochemical properties have been investigated and compared. Time resolved spectroscopic, techniques show that in FTO/TiO2/CdS films the radiative recombination of charges, separated by visible illumination of CdS, is faster than in FTO/ZrO2/CdS, evidencing that carrier dynamics in the two systems is different. Photoelectrochemical investigation evidence a suppression of electron collection in ZrO2/CdS network, whereas electron injection from CdS to TiO2 is very efficient since trap states of TiO2 act as a reservoir for long lived electrons storage. This ability of FTO/TiO2/CdS films is used in the reductive cleavage of N=N bonds of some azo-dyes by visible light irradiation, with formation and accumulation of reduced aminic intermediates, identified by ESI-MS analysis. Needed protons are provided by sodium formate, a good hole scavenger that leaves no residue upon oxidation. FTO/TiO2/CdS has an approximately 100 meV driving force larger than FTO/ZrO2/CdS under illumination for azo-dye reduction and it is always about 10% more active than the seconds. The films showed very high stability and recyclability, ease of handling and recovering.

Photoelectrocatalytic degradation of diclofenac with a boron-doped diamond electrode modified with titanium dioxide as a photoanode

The electrophoretic deposition of titanium dioxide (TiO2) nanoparticles (Degussa P25) onto a boron-doped diamond (BDD) substrate was carried out to produce a photoanode (TiO2/BDD) to apply in the degradation and mineralization of sodium diclofenac (DCF-Na) in an aqueous medium using photoelectrocatalysis (PEC). This study was divided into three stages: i) photoanode production through electrophoretic deposition using three suspensions (1.25%, 2.5%, 5.0% w/v) of TiO2 nanoparticles, applying 4.8 V for 15 and 20 s; ii) characterization of the TiO2/BDD photoanode using scanning electron microscopy and cyclic voltammetry response with the [Fe(CN)6]3-/4- redox system; iii) degradation of DCF-Na (25 mg L−1) through electrochemical oxidation (EO) on BDD and PEC on TiO2/BDD under dark and UVC-light conditions. The degradation of DCF-Na was evaluated using high-performance liquid chromatography and UV–Vis spectroscopy, and its mineralization measured using total organic carbon and chemical oxygen demand. The results showed that after 2 h, DCF-Na degradation and mineralization reached 98.5% and 80.1%, respectively, through PEC on the TiO2/BDD photoanode at 2.2 mA cm−2 under UVC illumination, while through EO on BDD applying 4.4 mA cm−2, degradation and mineralization reached 85.6% and 76.1%, respectively. This difference occurred because of the optimal electrophoretic formation of a TiO2 film with a 9.17 μm thickness on the BDD (2.5% w/v TiO2, time 15 s, 4.8 V), which improved the electrocatalysis and oxidative capacity of the TiO2/BDD photoanode. Additionally, PEC showed a lower specific energy consumption (1.55 kWh m−3). Thus, the use of nanostructured TiO2 films deposited on BDD is an innovative photoanode alternative for the photoelectrocatalytic degradation of DCF-Na, which substantially improves the degradation capacity of bare BDD.

The thrust enhancement for SDBD with nanostructured TiO2 films

Design requirements of the structural features, the material properties, and the processing capabilities are hard to be satisfied in nanotechnologies simultaneously. In this paper, TiO2 nanoparticles that are chemically reliable have been processed through the doctor blade method to realize a kind of field enhancement nanostructure, aiming to enhance the dielectric-barrier-discharge plasma actuation performance. It is found that the thrust enhancement rate could be approximately 72% at 13 kV and 8 kHz, compared to the controlled samples. In addition, a threshold phenomenon of the thrust enhancement effect was also found from the experiments, where the applied voltage and frequency lower than specific criteria could both lead to a decrease in the thrust generation and vice versa. It is suggested that the increase in the ionization frequency resulted from the field enhancement effect of the nanostructures is the leading mechanism for the extra thrust generation, which is inconsistent with the experimental examinations of the plasma characteristics and the plasma kinetic simulation. The results suggested that TiO2 nanoparticles could be used to improve the actuation performance in harsh environments with sound substrate compatibility.

Mechanically Switchable Wetting Petal Effect in Self-Patterned Nanocolumnar Films on Poly(dimethylsiloxane).

Switchable mechanically induced changes in the wetting behavior of surfaces are of paramount importance for advanced microfluidic, self-cleaning and biomedical applications. In this work we show that the well-known polydimethylsiloxane (PDMS) elastomer develops self-patterning when it is coated with nanostructured TiO2 films prepared by physical vapor deposition at glancing angles and subsequently subjected to a mechanical deformation. Thus, unlike the disordered wrinkled surfaces typically created by deformation of the bare elastomer, well-ordered and aligned micro-scaled grooves form on TiO2/PDMS after the first post-deposition bending or stretching event. These regularly patterned surfaces can be reversibly modified by mechanical deformation, thereby inducing a switchable and reversible wetting petal effect and the sliding of liquid droplets. When performed in a dynamic way, this mechanical actuation produces a unique capacity of liquid droplets (water and diiodomethane) transport and tweezing, this latter through their selective capture and release depending on their volume and chemical characteristics. Scanning electron and atomic force microscopy studies of the strained samples showed that a dual-scale roughness, a parallel alignment of patterned grooves and their reversible widening upon deformation, are critical factors controlling this singular sliding behavior and the possibility to tailor their response by the appropriate manufacturing of surface structures.

Synthesis and Photoelectrocatalytic Activity of Anodic Nanostructured TiO₂ Films

Nanostructured titanium dioxide films were prepared by electrochemical oxidation technique, anodization voltage effect on structure morphology, optical and photoelectrocatalytic performances of the nanotubes were studied. The anodization voltage is shown to significantly affect structure of nanofilms and, accordingly, their photoelectrocatalytic activity. An active heterojunction photoanode was synthesised with electrodeposition of Cu₂O onanodized TiO₂. The anode photoelectroact ivityunder bias 1V (Ag/AgCl/3,5M KCl) is found to be 15 % higher than that of the original nanostructured TiO₂ film

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.

Inclined Substrate Deposition of Nanostructured TiO2 Thin Films for DSSC Application.

Nanostructured TiO2 films were deposited onto Indium Tin Oxide (ITO) and glass substrates by dc reactive magnetron sputtering at different substrate inclination angles. The structural and optical properties of the deposited films were studied by X-ray diffraction, scanning electron microscopy and UV–Vis spectrophotometer, respectively. Dye-sensitized solar cells (DSSC) were assembled using these TiO2 films as photoelectrodes and the effect of the substrate inclination angle in the preparing process of TiO2 films on the DSSC conversion efficiency was studied.

Thermal Stability of the Structure and Optical Properties of Nanostructured TIO2 Films

The structure and optical properties of titanium dioxide films have been studied during annealing from 100 to 400°C. The films were obtained by ion-plasma high-frequency magnetron sputtering of polycrystalline rutile target in an argon atmosphere. It was shown that as-prepared TiO2 films are nanostructured with ~8 nm rutile crystallites and ~3.3 A interplanar distances and contain a small fraction of anatase. The optical band gap of the films is 3.01 eV, and the refractive index under normal conditions is 2.25. The film annealing at tamperatures from 100 to 400°C does not practically change their structure, optical band gap, and refractive index under normal conditions, i.e., the obtained nanostructured TiO2 films are thermally stable.

Influence of Fe3+ ion doping on the luminescence emission behavior and photocatalytic activity of Fe3+, Eu3+-codoped TiO2 thin films

Abstract Thin films of Fe3+ doped TiO2:0.01Eu3+ nanoparticles were coated by sol-gel spin coating technique on glass substrates. The studies carried out by using X-ray Diffractometer, SEM-EDX, HRTEM, spectroscopic ellipsometer, Raman, EPR, UV–Vis, and fluorescence spectrometer techniques. The crystalline structure and phase formation of Fe doped TiO2:0.01Eu3+ nanoparticles were investigated using X-ray Diffractometer. The HRTEM pictures of 3%, and 5% Fe doped TiO2:0.01Eu3+ films confirmed that the particle size is about 11 nm and 9.5 nm respectively. Raman spectroscopy was used to study the phase identification and vibrational modes present in Fe, Eu codoped TiO2 films. The band gap declined with cumulative amount of Fe3+. The EPR analysis endorses that the Fe3+ ions are successfully doped in the lattice of Titania by replacing Ti4+ ions and formation of oxygen vacancies and Ti3+ sites. With 393 nm excitation, the Fe doped TiO2:0.01Eu3+ nanoparticles show characteristic photoluminescence in the visible range. The strong luminescence emission at 614 nm is related to the 5D0 → 7F2 ED transition. The emission peak intensity declined with an increase in the amount of Fe3+. J–O and radiative parameters of Fe doped TiO2:0.01Eu3+ films obtained from the emission spectra. These nanophosphor films having significant CIE chromaticity coordinate (x, y) values with high color purity might have potential applications in solid-state display devices. The photocatalytic activity (PCA) of Fe, Eu codoped TiO2 nanostructured films were estimated using decolorization of methylene blue (MB) and methyl orange (MO). Fe, Eu codoped TiO2 films exhibit strong photocatalytic performance than undoped and single doped TiO2 films. The degradation efficiencies significantly increase with an increase in Fe3+ doping concentration reached maximum at 3%Fe doping and then reduces gradually at high concentrations due to the formation of recombination centers for charge carriers at a higher amount of Fe doping.

Термическая стабильность структуры и оптических свойств наноструктурированных пленок TiO2

Термическая стабильность структуры и оптических свойств наноструктурированных пленок TiO2