TiO2 Films Research Articles

Polyimide impregnated silver nanowire-titanium oxide core–shell nanostructures as ultra-stable flexible transparent electrode for multiple applications

Silver nanowires (AgNWs)-based flexible-transparent conducting electrode (f-TCE) have various optoelectronic applications. Although, bare AgNW-based f-TCE faces challenges of poor adhesion with the substrate, rough surface and low thermal stability. In this work, we demonstrate preparation of f-TCE by coating a very thin layer of TiO2 over AgNWs to form AgNW-TiO2 core–shell structures. Due to very thin TiO2 film in core–shell structure, the amorphous TiO2 converted into crystalline and delivered excellent conductivity at low curing temperature of 100 °C. The adhesion and roughness issues are solved by impregnating the core–shell AgNW-TiO2 within polyimide (PI) matrix. The PI impregnated AgNW-TiO2 core–shell structure as f-TCE delivered excellent stability after 5000 times of bending and number of peeling off cycles. The as prepared f-TCE delivered sheet resistance (Rs) of 8.61 Ω/sq with transmittance of 85 % at 550 nm and Rs of 4.2 Ω/sq with transmittance of 81 % when cured at 250 °C. The surface temperature of f-TCE was found to increase up to 90 °C in 40 s after applying 4 V of supply indicating its potential as transparent heater. In addition to that the CIGS solar cell fabricated by utilization of our f-TCE exhibited efficiency of 9.6 %, demonstrating its applicability for photovoltaic applications.

Multifunctional organic salts synergize interfacial passivation for efficient PSCs

Fully inorganic metal halide perovskite solar cells (PSCs) exhibit high efficiency and excellent thermal stability. However, the presence of surface traps caused by oxygen vacancies in the electron transport layer leads to significant non-radiative charge recombination, which limits both the short-circuit current density (JSC) and photoelectric conversion efficiency (PCE). In this study, we propose a dual-purpose strategy by incorporating the multifunctional organic salt dopamine hydrochloride (DACl) as an additive into the electron transport layer. Firstly, DACl acts as a Lewis base when added to TiO2 films, facilitating improvements in electron transport properties and resulting in higher photovoltaic quality of subsequently deposited perovskite layers. This enhancement significantly improves overall photovoltaic performance. Secondly, DACl's electron-rich aromatic structure and -NH2 functional group can anchor undercoordinated Pb2+ ions and passivate defects within the perovskite film. Additionally, its -OH functional group and charged ion Cl- play crucial roles in improving perovskite grain size and crystallinity. As a result of these modifications, cell efficiency increased ∼35 %, from 9.37 % to 12.70 %, while short-circuit current density increased from 15.44 mA cm−2 to 17.80 mA cm−2 at an illumination intensity of 100 mW cm−2. These findings suggest that introducing DACl into the ETL layer is a promising approach for achieving efficient and stable PSCs.

TiO2‐Based Schottky Diodes as Bidirectional Switches for Bipolar Resistive Memories

This study presents TiO2‐based Schottky diodes designed as bidirectional switches for bipolar resistive memories. The TiO2 films in these Schottky diodes are prepared through an anodization process. The reverse current of these diodes exhibits an exponential increase with rising reverse voltage, ultimately matching the forward current. When two diodes are connected back‐to‐back, they demonstrate superior current–voltage symmetry and provide a wider off‐state voltage range compared to a single diode, reaching up to 3.65 V. The adjustable off‐state voltage range (0.40–3.65 V) of the switch, whether utilizing two diodes or a single diode, correlates well with the TiO2 layer thickness and oxygen partial pressure during Pt electrode sputtering. These diodes possess bidirectional switching characteristics and can serve as effective switch elements to address the sneak‐path issue in bipolar resistive memories.

Effect of annealing temperature on the structural, optical, morphological, and photocatalytic properties of TiO2 thin films prepared by sol-gel spin-coating and electron beam physical vapor deposition

TiO2 thin films were prepared by sol-gel spin-coating (SGSC) and electron beam-physical vapor deposition (EB-PVD) methods and annealed at different temperatures (Ta ). X-ray diffraction spectroscopy (XRD) results show that the TiO2 films prepared by the SGSC method transformed from the anatase single phase to the coexistence of anatase and rutile with the increase of Ta . However, TiO2 films prepared by the EB-PVD method existed only in the anatase phase, and the crystalline strength was enhanced with the increase of Ta . Meanwhile, particles of TiO2 targets annealed at different Ta showed a rutile phase for TiO2 target particles in the EB-PVD method. The results indicate that the EB-PVD method hinders the nucleation growth and phase transformation of TiO2 films. Scanning electron microscopy and atomic force microscopy also show that the grain size and R ms of TiO2 thin films prepared by the SGSC method increased with the increase of Ta , and the grain size becomes inhomogeneous when the rutile phase is formed. Ultraviolet–visible results show that the forbidden bandwidth and light absorption capacity increase with increasing Ta . For the EB-PVD method, the grain size and surface roughness gradually increased when the Ta of the films was less than 800 °C, while annealing at 800 °C changed the direction of growth and nucleation, and also produced surface cracks; XRD verified the hypothesis that the EB-PVD method hinders the nucleation growth as well as the phase transition of the films. Weak differences in the optical absorption properties and bandgap values of the films also indicate that the EB-PVD method hinders the phase transformation of TiO2 films. Finally, the results of degradation of methylene blue (MB) under simulated visible light showed that the films prepared by the SGSC method gradually improved the photocatalytic performance with the enhancement of the crystalline strength of the anatase phase. The TiO2 films prepared by the EB-PVD method improved the photocatalytic performance with the increase of the active area.

Corrosion of Anodized Titanium Alloys

Ti and Ti alloys are employed in demanding industries such as aerospace, automotive, biomedical, aeronautic, structural, naval, and chemical, thanks to their resistance to corrosion due to the formation of the TiO2 film on the surface. Diverse research has established that different corrosive media could attack the oxide layer. One way to generate a stable, compact, and continuous oxide film is through anodizing treatment. The efficiency of anodization depends on diverse factors such as the microstructure, chemical composition of alloys, pH of electrolyte, time, and temperature of anodizing. This review aims to examine the corrosion resistance of the anodized layer on Ti and Ti alloys, with different parameters. The discussion is centered on the influence of the different parameters and alloy properties in the effectivity of anodizing when they are characterized by electrochemical techniques while studying the behavior of oxide.

In-situ and wavelength-dependent photocatalytic strain evolution of a single Au nanoparticle on a TiO2 film

Photocatalysis is a promising technique due to its capacity to efficiently harvest solar energy and its potential to address the global energy crisis. However, the structure–activity relationships of photocatalyst during wavelength-dependent photocatalytic reactions remains largely unexplored because it is difficult to measure under operating conditions. Here we show the photocatalytic strain evolution of a single Au nanoparticle (AuNP) supported on a TiO2 film by combining three-dimensional (3D) Bragg coherent X-ray diffraction imaging with an external light source. The wavelength-dependent generation of reactive oxygen species (ROS) has significant effects on the structural deformation of the AuNP, leading to its strain evolution. Density functional theory (DFT) calculations are employed to rationalize the induced strain caused by the adsorption of ROS on the AuNP surface. These observations provide insights of how the photocatalytic activity impacts on the structural deformation of AuNP, contributing to the general understanding of the atomic-level catalytic adsorption process.

An ultraviolet photodetector based on conductive hydrogenated TiO2 film prepared by radio frequency atmospheric pressure plasma

The growing demand for real-time ultraviolet (UV) monitoring calls for a simple, rapid, and low-cost strategy to prepare UV photodetectors (PDs). We prepare a wearable real-time UV PD based on hydrogenated titanium dioxide film synthesized by radio frequency atmospheric pressure plasma. The conductivity of our hydrogenated titanium dioxide is improved to 10.2 S cm−1, nine orders of magnitude higher than that of pristine titanium dioxide after 10 min plasma treatment. Plasma hydrogenation disrupts the surface crystal structure, introducing oxygen vacancies (OVs) that create self-doped titanium(III) and titanium(II) species. First-principles calculations indicate that the OVs raise the Fermi level of TiO2 and distort the lattice locally. Our optimized film has a distinctive periodic switching characteristic under intermittent illumination; its responsivity is good from 280 to 400 nm, peaking at 632.35 mA W−1 at 365 nm. The fabricated wearable sensor based on the optimized film effectively monitors the daily variation of ambient UV intensity in three typical weather types, transferring its data to a smartphone via Wi-Fi.

Investigating resistive and gas sensing properties of TiO2, CuO and TiO2-CuO thick films

New inventions in modern research work related to material science always based on the preparation of a well adhered film (thin or thick) of suitable base material on a suitable substrate and investigating their functional characteristics. In our work we used TiO2 and CuO as base materials. In our work, we prepared thick films of TiO2, CuO and TiO2-CuO films of variable percentage. All the films were prepared on a suitably small electrode pattern Printed Circuit Board. Then the I-V characteristic of all prepared thick film was investigated by simple lab prepared two probe method. Variation in resistive properties of each film was investigated. Also, gas sensing performance of each film was investigated.

Boosting of structural, thermal, linear, and nonlinear optical properties of PVA/PVP blend using titanium dioxide filler

AbstractIn the current work, a blend matrix that combines polyvinyl alcohol and polyvinyl pyrrolidone (PVA/PVP) was reinforced by titanium dioxide (TiO2) nanoparticles via the casting technique. The FTIR spectra and XRD examinations of nanocomposites offer insight into the structural changes that have taken place with the inclusion of TiO2 in the blend matrix. TiO2 elements were detected via the EDX detector linked to a scanning electron microscope (SEM). The transmission and absorption of the PVA/PVP‐TiO2 blend were evaluated via a UV–visible spectrophotometer. Tauc's model demarcated the optical bandgap (Eg), which declined from 4.91 eV for the pure to 4.66 eV for PVA/PVP—0.75 wt.%TiO2 film. The refractive index increases from 1.903 to 6.646 for pure blend and PVA/PVA/0.75 wt%TiO2, respectively. The nonlinear optical features (as predicted by the Wemple‐DiDomenico model) are enriched. The proliferation of TiO2 into the blend matrix significantly increased the third‐order nonlinear optical susceptibility χ(3), from 1.87 × 10−14 for pure blend to 5.091 × 10−13 for PVA/PVP‐0.75 wt.% TiO2, attributed to the oscillation of surface plasmons of TiO2 NPs. The thermal stability of the films was inspected. Doping the blend with TiO2 enhanced its thermal stability. The TiO2‐filled PVA/PVP films demonstrate hopeful features for various requests and can be utilized in optoelectronics and optical devices due to their tunable optical parameters and thermal stability.Highlights Thermal stability was enhanced with loading TiO2 nanoparticles in PVA/PVP matrix. The PVA/PVP–TiO2 films optical parameters were studied. Extinction coefficient and refractive index were enhanced with loading TiO2 in PVA/PVP matrix. Proliferation of TiO2 into the matrix significantly increased the nonlinear optical susceptibility of third‐order χ(3).

Effect of titanium alkoxide on structure, morphology, and biocompatible properties of sol-gel synthesized TiO2 films

The purpose of this work was to study the influence of the nature of titanium alkoxide, used as a precursor for the synthesis of TiO2 films by the sol-gel method, on the crystal structure and morphology of coatings, as well as their biological compatibility. TiO2 coatings were synthesized on silicon substrates using the dip-coating method. Titanium alkoxides with different molecular weights were used as precursors: titanium tetraethoxide, titanium tetraisopropoxide, and titanium tetrabutoxide. The influence of the nature of the titanium precursor on the morphology and thickness of TiO2 films was determined using scanning electron microscopy. The structural properties of the coatings were studied by X-ray diffraction and Raman spectroscopy. Cell viability assay was performed on TiO2/Cu-Si(111) structures to evaluate the ability of TiO2 coatings synthesized from different precursors to prevent the release of toxic ions from the substrate. The biological compatibility of TiO2 films with various surface morphologies and structures was assessed based on the chorioallantoic membrane assay. It has been demonstrated that the type of titanium alkoxide utilized has a substantial influence on the morphology and crystal structure of TiO2 films produced through the sol-gel method. Furthermore, the structural properties of the coatings consequently impact their biological compatibility. Coatings synthesized from titanium tetrabutoxide exhibited the highest protective properties and biological compatibility.

Impact of Graphene oxide (GO) and reduced Graphene Oxide (rGO) on the TiO2 thin film composite (TiO2: GO/ rGO) photoanodes

Graphene and its derivatives have several advantages such as large surface area, great chemical stability, high transmittance, and good electrical conductivity, which are the fundamental qualities required by photovoltaic industries. GO and rGO are mixed in various proportions ranging 0 wt.% - 15 wt.% to spin coat TiO2: GO/rGO composite thin films. The effect of graphene oxide and reduced graphene oxide on the performance the TiO2 based composite photoanodes are obtained. A tetragonal anatase phase of TiO2 was confirmed by the XRD analysis. The calculated crystallite size decreases with lower concentrations of GO and rGO but starts to increase for higher concentrations. The spectrophotometer studies have confirmed that the optical bandgap of pure TiO2 films is decreased on doping with GO and rGO. The SEM analysis have confirmed that the surface is tightly packed with the uniformly distributed grains, and they are very compact.

Comparative investigation of structural, morphological, mechanical, tribological and electrochemical properties of TiO2 films formed on Cp-Ti, Ti6Al4V and Ti45Nb alloys

This study focuses on the comparison of structural, morphological, mechanical, tribological and electrochemical properties of TiO2 films fabricated on Cp-Ti, Ti6Al4V and Ti45Nb alloys, which are widely used in different industries. For this purpose, TiO2 films were grown on Cp-Ti, Ti6Al4V and Ti45Nb materials by anodization method. Structural, morphological and mechanical properties of the samples were determined using XRD, SEM, Micro Raman, contact angle, surface roughness and micro hardness devices. Afterwards, the samples were subjected to wear and corrosion tests using a pin-on-disc wear device and a corrosion device, respectively. Wear tests were carried out in both dry and liquid environments. In electrochemical corrosion tests, Ringer's solution was used and open circuit potential (OCP) and electrochemical polarization analyzes were performed. According to the results of XRD and Raman analyses, it was determined that TiO2 films were successfully grown on the surface of the samples. Additionally, it was observed that these films were in Rutile and Anatase phases and their peak intensities increased with increasing anodization time. While the thickest films were obtained from Ti45Nb samples, the thinnest films were obtained from Cp-Ti samples. As a result of the increase in surface roughness with anodization, surface wettability increased in all samples. It was seen that electrical resistance of the materials was highly effective on the film thickness, surface roughness and surface structures. Wear coefficients decreased in all samples for both dry and liquid wear conditions due to the increased surface hardness and anodic film thickness and the lowest wear coefficients were obtained from the Ti45Nb sample. Corrosion performance of the samples increased with anodization because TiO2 films acted as protective layers on surface of materials.

Atomic Layer Growth of Rutile TiO2 Films with Ultrahigh Dielectric Constants via Crystal Orientation Engineering.

In general, the electronic and optical properties of oxide films can significantly benefit from highly textured crystallinity. However, oxide films grown by atomic layer deposition (ALD), a powerful technique for the synthesis of high-quality, nanoscale thin films, usually exhibit amorphous or randomly oriented polycrystalline phases. Here, we demonstrate the growth of highly textured rutile phase ALD TiO2 films through rational substrate design. Both a- and c-axis preferentially oriented TiO2 films are obtained by varying the lattice parameters of the initial ALD growth surface. Under optimized conditions, we find that it is possible to deposit high-quality, c-axis preferentially aligned TiO2 films with a bulk dielectric constant approaching 185, rivaling the single crystal limit. These films display a remarkably high dielectric constant of 117 despite thin thickness of 5.2 nm. Moreover, the addition of a single doping sequence of Al2O3 successfully suppresses leakage currents to levels compatible with modern dynamic random access memory cells, all the while maintaining the high bulk dielectric constant of 137. These results clearly highlight the prospect of utilizing crystal orientation engineering in ALD thin films for emerging semiconductor devices.

The role of Cu and film thickness on the photocatalytic activity of mesoporous spin coated TiO2 films

Most practical applications of photocatalysts will involve coatings on an inert support; here we have examined how copper doping of spin coated porous TiO2 films affects their physical characteristics and photocatalytic activity. The photocatalytic degradation of stearic acid was used as a measure of photocatalytic activity for catalysts spin coated from a sol-gel onto glass with 0, 0.1, 0.5, 1, 2.5 and 5 wt% copper introduced into the catalyst lattice before gelation. The effects of spin coating speed on film thickness, structure and band gap were studied and the nature of the copper incorporated into the films examined with XPS and XANES measurements. Increased spin coating speeds reduces the thickness of the deposited films from ∼ 50 μm to ∼ 20 μm until a spin speed of ∼ 3000 rpm at which point non-Newtonian behaviour of the gels prevents further reductions in film thickness. A larger effect on film thickness is the presence of the added copper nitrate which results in thinner films. After calcining, XANES shows the bulk of the copper to be in a Cu(II) state but at the surface of the thinnest, most active films XPS shows only Cu(I). Photocatalytic activity is much more strongly affected by the presence of the copper than the thickness of the films with 0.1 wt% Cu catalysts as much as 10 times more active than the undoped catalysts. Increasing the copper content, however, reduces activity until at ∼ 5 wt% activity is lower than for the pure TiO2 films.

Fabrication of binder-free TiO2 P 25 films on flexible PET/ITO substrate for photoanode in dye-sensitized solar cells

In this work, TiO2 P 25 films for photoanode in dye-sensitized solar cells (DSSCs) have been fabricated using a flexible PET/ITO substrate with a low-temperature heating technique. Ammonium hydroxide/ethanol solution was used as an alternative binding agent to fabricate TiO2 paste, which can be removed at low-temperature heating. The conventional screen print method is still used in DSSC fabrication because it is a very cheap and easy technique. A hot-pressing method is also used to improve the quality of TiO2 films and the performance of DSSCs. The encapsulation technique used in the assembly of DSSC is expected to increase the stability of DSSC devices to prevent electrolyte leakage. The resulting TiO2 film shows the highest DSSC performance using the hot-pressing and encapsulation method with PCE 0.29%. The encapsulation technique increased the stability of DSSC devices with more extended durability than without encapsulation.

Laser-induced growth of metal oxide films on quartz tubes for photocatalytic water treatments

A solid-state pulsed laser technique was developed to in situ grow arbitrary immobilized catalysts (Fe3O4, CeO2, WO3 etc.) on the inner surface of quartz tube with robust adhering strength. In a case study, anatase/rutile hetero-phase TiO2 film was deposited to serve as immobilized photocatalysts for the effective removal of antibiotics from aqueous environment. The X-ray absorption spectroscopy, low temperature electron paramagnetic resonance and the density functional theory simulation directly confirm a defect-assisted type-II band alignment was established to facilitate the charge transfer at the hereto-interphase. In addition, the oxygen vacancy enriched anatase phase with greater binding energy towards the dissolved oxygen facilitated the O2– generation. Meanwhile, the rutile phase enriched with Ti3+ could effectively activate the antibiotics to promote the direct h+ mediated oxidation. Such integration of unique atomic vacancies prevent defects from becoming electron-hole recombination centers and consequently extend the lifetime of the photoexcited charge carrier. The degradation mechanism of oxytetracycline was thoroughly examined by ultra-high resolution electrospray time-of-flight mass spectrometry and Fukui function, while the ecological structure–activity relationships program assessed the toxicity of contaminant to the environment. Milewhile, a continuous water treatment apparatus employing the catalytic tubes as reactors was established and demonstrated a ∼ 95 % OTC degradation under the natural sunlight adopting river water as the background. The experimental studies also claimed that ∼ 90 % of the initial activity could be retained after 100 cycles reuse, which permits their great potential for the applicational scenarios.

Thymus schimperi Ronniger plant flower extract dye-sensitized solar cells

The demand for energy is greatly increasing due to the world’s population growth and technological advancement. Natural dye-sensitized solar cells are attracting research as an alternative and renewable energy source due to their simple preparation technique, availability, cost effectiveness and environmental friendliness. In the present work, we have successfully fabricated dye-sensitized solar cells (DSSCs) from Thymus schimperi Ronniger plant flowers for the first time. The solvents used for extraction of the flower dye were deionized water and its mixture with ethanol. The T. schimperi Ronniger flower extract dye solutions and sensitized photoanodes were characterized by Fourier transform infrared and ultraviolet–visible techniques. The crystallinity of TiO2 films was analyzed by x-ray diffraction, and the films showed pure anatase phase behavior. The photoelectrochemical solar cell performance parameters, such as short circuit current density, open circuit voltage, fill factor and efficiency, were evaluated from current density–voltage measurements using a Keithley 2450 source meter. DSSCs sensitized with dye solution extracted by a mixture of water and ethanol showed better performance (1.37%) than those sensitized with dye solution extracted by deionized water alone (1.02%).

Preparation and electrochromism of amorphous Bi-doped TiO2 film for aqueous-based electrochromic device

Amorphous Bi–TiO2 films with improved electrochromic properties have been successfully fabricated by a facile sol-gel spin-coating technology. The influence of dopant bismuth (Bi) content and sol amount on the electrochromic performance of Bi–TiO2 films was studied. The optimized Bi–TiO2 films show outstanding electrochromic properties, including wide transmittance modulation (ΔT = 74.26 % at 640 nm), short switching times (2.6 s/3 s for bleaching and coloring), and large coloration efficiency (52.77 cm2 C−1). A proton-based electrochromic device was prepared by the amorphous Bi–TiO2 film as the electrochromic film and Cu sheet as the counter electrode. The prepared device has a small operating potential range (1.0 V) in aqueous electrolyte due to the excellent electrochromic performance and high proton activity for the amorphous Bi–TiO2 film. In addition, the device shows excellent performance (ΔT = 67.41 %, 2.5 s/3.9 s for bleaching and coloring), providing an important reference value for the development of high-efficiency electrochromic device.

Effects of oxygen sources on the growth characteristics and dielectric properties of atomic-layer-deposited TiO2 films for aluminum electrolytic capacitors

TiO2 is a promising high dielectric material which can be introduced into aluminum anode foils for realizing miniaturization, lightweight, and high quality of aluminum electrolytic capacitors because of its excellent permittivity. However, the complex porous framework of etched aluminum foil gives rise to the low step coverage and residual carbon impurities of TiO2 films, which can restrict the specific capacitance improvement. In this work, the TiO2 films were deposited by atomic layer deposition (ALD) using O3, O2 plasma (O2*), H2O as oxygen sources, respectively. The effects of oxygen sources on step coverage, carbon impurity content, crystalline structure, oxygen vacancies (OVs) concentration and band gap (Eg) of TiO2 films were studied. Besides, the capacitor performances of aluminum foils were investigated. The O3–TiO2 films showed the best conformability and the least carbon impurity content, while the O2*-TiO2 films exhibited the lowest step coverage due to the directionality of plasma. And the highest carbon impurity content in H2O–TiO2 films was caused by the poor reactivity of H2O. Moreover, the anatase TiO2 peak intensity of H2O–TiO2 films through sintering and anodization was the highest due to the highest deposited mass. The O3–TiO2 films were found to be optimally insulating by characterization of OVs concentration and Eg. Surprisingly, the composite dielectric films using O3 as oxygen source exhibited the excellent withstanding voltage of 21.9 V, while the specific capacitance of 159.9 μF cm-2 was maintained, and there were about 45.89% and 33.63% enhancements in the specific capacitance and CV compared with those without TiO2. These outstanding properties demonstrate that O3 is more favorable for depositing high-performance ALD TiO2 films on aluminum electrolytic capacitors.

Synthesis, Characterization, and Photocatalytic Properties of Sol-Gel Ce-TiO2 Films

In this study, nanostructured cerium-doped TiO2 (Ce-TiO2) films with the addition of different amounts of cerium (0.00, 0.08, 0.40, 0.80, 2.40, and 4.10 wt.%) were deposited on a borosilicate glass substrate by the flow coating sol-gel process. After flow coating, the deposited films were dried at a temperature of 100 °C for 1 h, followed by calcination at a temperature of 450 °C for 2 h. For the characterization of sol-gel TiO2 films, the following analytic techniques were used: X-ray diffraction (XRD), differential thermal analysis (DTA), thermal gravimetry (TG), differential scanning calorimetry (DSC), diffuse reflectance spectroscopy (DRS), and energy dispersive X-ray spectroscopy (EDS). Sol-gel-derived Ce-TiO2 films were used for photocatalytic degradation of ciprofloxacin (CIP). The influence of the amount of Ce in TiO2 films, the duration of the photocatalytic decomposition, and the irradiation type (UV-A and simulated solar light) on the CIP degradation were monitored. Kinetics parameters (reaction kinetics constants and the half-life) of the CIP degradation, as well as photocatalytic degradation efficiency, were determined. The best photocatalytic activity was achieved by the TiO2 film doped with 0.08 wt.% Ce, under both UV-A and solar irradiation. The immobilized catalyst was successfully reused for three cycles under solar light simulator radiation, with changes in photocatalytic efficiency below 3%.