TiO2 Nanofilms Research Articles

From Structural Colors to Super-Hydrophobicity and Achromatic Transparent Protective Coatings: Ion Plating Plasma Assisted TiO<sub>2</sub> and SiO<sub>2</sub> Nano-Film Deposition

The implementation of the Ion Plating Plasma Assisted technology in the area of surface functionalization for structural color and relic preservation applications is presented. Interferometric structural colors on irregular bumped Titanium surfaces and transparent and achromatic nano films on ancient ceramic artifact have been investigated. Titanium metal and ceramic supports have been utilized for the surface functionalization tests: A metallic electron beam additive manufactured Titanium component and an ancient tile of the XIX century, which was characterized by strong chromatic valence and by a mixed porous and glazed surfaces, have been considered. A reactive magnetron sputtering Ion Plating Plasma Assisted apparatus operating in Argon or Oxygen atmospheres for TiO2 and SiO2 deposition has been utilized. Preliminary tests with two plasma treatments were carried out for optimal processing conditions definition. TiO2 nano-film deposition on irregular Ti surfaces has generated light direction depending color-changing surfaces while good achromatic and transparent coatings were obtained by using SiO2 coating. The high processing flexibility of the Ion plating technology is discussed. The SiO2 IPPA surfaces treatment resulted more convenient for restorative and preservation ancient historical tile was used to finally test the optimized process with Ion Beam Electron Microscopy, which was carried out on the tile porous structure, confirmed the high flexibility and efficiency of the innovative IPPA technology.

Surface characterization and gas sensing performance of yttrium doped TiO2 nanofilms prepared by automated nebulizer spray pyrolysis (ANSP)

YxTi1−xO2 nanofilms were deposited on glass substrate at 500 °C by automated nebulizer spray pyrolysis route. The influence of yttrium concentration on XRD shows the stabilized anatase tetragonal polycrystalline nature and *(222), *(400) plane orientation of Y2O3 were revealed by Y = 10%. An XPS spectrum reveals the primary elements such as O 1s, Ti 2p, Y 3d, Ti 3p and C 1s with a binding energy respectively. The morphological study of FESEM shows the modification from granular spherical to honeycomb structure based on yttrium concentration. Optical study shows the blue shift of sharp absorption edge with increased band gap values (E g = 3.20 eV–3.78 eV) is depends upon Y concentration. Notably, gas sensing performance of YxTi1−xO2 shows the highest sensitivity response to Y = 10% (Y0.10Ti9.90O2) of NH3 at 150 °C with 300 ppm gas concentration and all the films exhibits better sensitivity response in order to NH3 > C2H6O > C3H6O> CH4O > C3H8O.

Dragon fruit-inspired quantum scale-designed photocathodes

The development of environment-friendly, high-performance, and low-cost photoelectrocatalysts is hindered by the low separation efficiency of electron–hole pairs, corrosion from light illumination, and harsh environments. In this study, we propose a hierarchical structured nanocomposite that addresses all the aforementioned problems. Our design is inspired by the structure of a dragon fruit, in which CuInS2/CdS quantum dots (QDs) are encapsulated with TiO2 nanofilms. CuInS2/CdS QDs possess effective charge separation capability but suffer from photocorrosion, whereas TiO2 exhibits the opposite behavior. As a result of this hierarchical arrangement, the complementary system exhibits outstanding durability (lasting longer than 240 h without decay) and high-performance photoelectrocatalysis activity (potentials of approximately −0.219 V to obtain current densities of 100 mA cm−2) under light illumination.

A cost- and time-saving strategy of spraying TiO2 self-cleaning coatings in tubular substrates by air cold plasma

In this study, using an atmospheric pressure air plasma jet generated by a dielectric barrier structure with hollow electrodes (HEDBS), we developed an ultrafast process for spraying TiO2 self-cleaning films inside tubular substrates. Importantly, SEM images showed that the TiO2 particles were dispersed evenly in the tubular substrates. Furthermore, Raman and XRD pattern indicated the anatase structure of the HEDBS-spayed TiO2 coating after heating at 270°C. Further results of the self cleaning test suggested that the proposed cost- and time-saving HEDBS approach with air working gas could provide a feasible way for synthesizing thin TiO2 nanofilms.

Production and Characterization of TiO2 Nanofilms for Hemocompatible and Photocatalytic Applications

Fil: Schvezov, Carlos Enrique. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Nordeste. Instituto de Materiales de Misiones. Universidad Nacional de Misiones. Facultad de Ciencias Exactas Quimicas y Naturales. Instituto de Materiales de Misiones; Argentina

In situ construction of g-C3N4/TiO2 heterojunction films with enhanced photocatalytic activity over magnetic-driven rotating frame

Corn-shaped TiO2 nanofilms were fabricated by a glycerol-assisted hydrothermal method, and then g-C3N4 was deposited on the surface of TiO2 films using melamine as precursor under air atmosphere by an in site microwave-heating technique. The investigations indicate that microwave-heating process is a facile strategy to obtain g-C3N4 by thermal polymerization of melamine, which can achieve in situ constructing of g-C3N4/TiO2 heterojunction films with high stability. The as-prepared TiO2 films with crack and holes have visible light scattering capability, and the scattering light overlaps with the intrinsic absorption of g-C3N4, leading to an absorption plateau in the range of 400–550nm. Besides, a magnetic-driven rotating frame was developed to enhance the mass transfer processes during the photocatalytic water splitting. The result shows that g-C3N4/TiO2 films exhibit excellent activities under simulated-sunlight irradiation, in addition to the enhanced mass transfer, the overlapped visible light absorption, stable contact and effective charge transfer between g-C3N4 and TiO2 can facilitate the hydrogen production and light utilization efficiency as well. The hydrogen production rate can reach 13.8mmolh−1m−2 over g-C3N4/TiO2 films prepared using 0.5g of melamine and 16.0cm2 of TiO2.

Role of molar concentration in structural, optical and gas sensing performance of anatase phase TiO2 nanofilms: automated nebulizer spray pyrolysis (ANSP) technique

TiO2 nanofilms were deposited on a glass substrate at 500 °C using automated nebulizer spray pyrolysis. The anatase polycrystalline structure with increased grain size and variations of surfactant planes (T c) were influenced by molar concentration on XRD study. AFM study shows the average roughness values were increased with increase in molar concentration. A granular domain like microstructure with crack and void-free particle was examined by FESEM. The maximum transmittance ~95.5% (529.6 nm) for x = 0.05 M/L, further increment of molar concentration showed the decremented transmittance with red shift absorption edge and the calculated band gap values (E g = 3.53–3.20 eV) also noted. The gas sensing performances of films were studied with respect to various gas sensing parameters and the ammonia (NH3) gas showed better sensing response (S max = 89%) at 150 °C for 300 ppm gas concentration against other gases (C2H6O, CH4O, C3H8O and C3H6O).

Photocatalytic hollow TiO2 and ZnO nanospheres prepared by atomic layer deposition

Carbon nanospheres (CNSs) were prepared by hydrothermal synthesis, and coated with TiO2 and ZnO nanofilms by atomic layer deposition. Subsequently, through burning out the carbon core templates hollow metal oxide nanospheres were obtained. The substrates, the carbon-metal oxide composites and the hollow nanospheres were characterized with TG/DTA-MS, FTIR, Raman, XRD, SEM-EDX, TEM-SAED and their photocatalytic activity was also investigated. The results indicate that CNSs are not beneficial for photocatalysis, but the crystalline hollow metal oxide nanospheres have considerable photocatalytic activity.

Au-TiO2 nanofilms for enhanced photocatalytic activity

Au/TiO2 nanofilms are prepared on indium-tin oxide glass using magnetron sputtering. The bilayer nanofilms are heat-treated at 500°C in air for 2h. The microstructure evolution of the prepared Au/TiO2 nanofilms is characterized, using scanning electron microscope, energy dispersive spectrometer, and X-ray diffraction. The heat treatment leads to the migration of Au atoms to form Au/TiO2 nanofilms with TiO2 being in anatase phase and the presence of Au films/islands on the surface of the Au/TiO2 nanofilms. The photocatalytic activity of the prepared Au/TiO2 nanofilms in an aqueous solution of methylene blue (MB) is evaluated under the irradiation of visible light. The experimental results show that the photocatalytic activity of the prepared Au/TiO2 nanofilms depends on the loading amount of Au. The rate constant for the photodegradation of the MB compound in the aqueous solutions with pure TiO2 nanofilms is less than those with the prepared Au/TiO2 nanofilms. Such behavior can be likely attributed to the activation of the photo-generated charge carriers and the increase of the electron–hole separation efficiency through localized surface plasmon resonance.

A study of the physical properties and gas‐sensing performance of TiO2 nanofilms: Automated nebulizer spray pyrolysis method (ANSP)

Automated nebulizer‐sprayed TiO2 nanofilms were deposited on the glass substrate by using different temperature (300, 350, 400, 450, and 500 °C). The effect of temperature on the structural study by XRD and AFM reveals that the amorphous nature turns to stabilized anatase tetragonal phase with an enhancement of the preferred orientation (101), particle size, average roughness of the topographical view and thickness (238, 279, 304, 362, and 397 nm) of the coated films. The morphological study by the FESEM method shows a crack and a void free micro grain particle due to the effect of temperature. An optical study shows that the transmittances of all the samples gradually decreased and the redshift of the absorption edges with decreased bandgap (3.67–3.35 eV) value is observed by the influence of temperature. The n‐type semiconducting nature of TiO2 nanofilms shows the voltage drop across the sensor element on exposure to the reducing gas. Among the various gases (CH4O, C3H8O, NH3, C3H6O) the reducing gas C2H6O exhibits a better response for a 500 °C coating temperature at an optimal operating temperature of 300 °C with 150 ppm gas concentration.

Ultrathin amorphous TiO2 nanofilm-coated graphene with superior electrochemical performance for lithium-ion batteries

As a novel anode material for lithium-ion batteries, graphene has a higher theoretical capacity than graphite. However, the practical application of graphene suffers from a low coulombic efficiency and poor cycle stability due to the unstable solid electrolyte interphase layer. In this work, ultrathin amorphous TiO2 nanofilm-coated graphene is fabricated by controlled hydrolysis of tetrabutyl titanate on the surface of graphene, and shows superior cycle and rate performance compared to uncoated graphene because amorphous TiO2 nanofilms can prevent the detachment of graphene nanosheets and avoids the formation of thick and unstable solid-electrolyte interphase layers during cycling. Moreover, the electrochemical performance of TiO2-coated graphene can be further improved by controllable calcination of TiO2-coated graphene under a N2 atmosphere. The produced porosity of TiO2 nanofilms after calcination can improve both Li+ and electron transport, leading to the further improved lithium storage performance of graphene. This novel synthesis strategy may be employed in other graphene-based anode materials for high-performance lithium-ion batteries and other electrochemical devices.

Effect of thickness on the physical properties and gas sensing application: anatase titanium dioxide nanofilms by automated nebulizer spray pyrolysis (ANSP)

In this work, effects of thickness towards volume proportion of TiO2 nanofilms were deposited on a glass substrate at 500 °C by using ANSP method. The optical profilometer shows the coated films thicknesses were increased (186, 234, 311, 397 and 433 nm) by increasing the volume proportion. Based on the thickness, The XRD reveals a polycrystalline tetragonal anatase phase with decreased particle sizes. The topographical study (AFM) of 3D surface view shows the incremented average roughness (Ra) values. The surface morphological variations with decremented particle size were examined by FESEM. The maximum transmittance ~78.5% (λ = 612.8 nm) is obtained to 186 nm thickness and further increment of thickness shows the decremented value of transmittance with an absorption edge shifted from lower to higher wavelength (blue shift) and the calculated band gap value Eg = 3.65–3.26 eV. The gas sensing performances of films was studied by using a various sensing parameters, obviously C2H6O gas shows highest response (Sm = 13% as 397 nm) at 300 °C for 150 ppm gas concentration against other gasses (NH3, CH4O, C3H8O and C3H6O).

Effect of SiO2-doping on photogenerated cathodic protection of nano-TiO2 films on 304 stainless steel

In this study, SiO2-TiO2 composite films were prepared on 304 stainless steel (SS) by a sol-gel method and dip-coating technology. The impact of doping SiO2 on the microstructure and photoelectrochemical performance of the films was investigated. The results demonstrated that pure TiO2 film was composed of anatase and rutile. Doping the film with SiO2 suppressed the phase transformation of anatase to rutile and decreased particle sizes of the films. SiO2 also reduced fluorescence intensity of the composite films, inhibiting the recombination of electrons and holes. Optical absorption intensity of the films first increased and then decreased with increasing SiO2. The corrosion potential of the coated 304SS in 3.5% NaCl in the dark increased along with SiO2 content. Under illumination, however, the 304SS with 10% SiO2-TiO2 film behaved the lowest corrosion potential and smallest charge transfer resistance. Further SiO2 addition caused an amorphous film and suppressed light absorption, resulting in decreased photoelectrochemical performance.

A detailed investigation on the performance of dye-sensitized solar cells based on reduced graphene oxide-doped TiO2 photoanode

The sintered TiO2 nanofilms were immersed in the aqueous solution of graphite oxide and then were thermally reduced to reduced graphene oxide (RGO), resulting in RGO-doped TiO2 photoanodes employed in the dye-sensitized solar cells (DSSCs). This preparation method for the reduced graphene oxide–TiO2 (RGO–TiO2) photoanode could avoid the loss of RGO during the sintering process. The presence of RGO in the photoanodes was confirmed using Raman analysis, scanning electron microscopy, transmission electron microscopy, and energy-dispersive spectrometer. The amount of RGO in photoanode was obtained by thermo-gravimetric analysis. Other techniques such as X-ray diffraction, Brunauer–Emmett–Teller, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the composite materials of RGO–TiO2. The J–V measurement of RGO–TiO2-based DSSCs showed that the best photoelectric conversion efficiency (η) of 6.85% is 11.7% higher than that of the pure TiO2 (P25–TiO2)-based DSSCs. It was shown that RGO in the photoanode could facilitate the phase transition in TiO2 crystals (from anatase to rutile) resulting in the mixed crystals in the photoanodes. The existence of RGO and mixed-crystal structure of TiO2 changed the electronic transmission pathway, reduced the recombination rate of electron–hole pairs, and thus improved the η of DSSCs.

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.

Fabrication of Pr-PVP-Co-Doped NanoTiO2 Film on Titanium Matrix with Outstanding Electrocatalytic Reduction Activity for Oxalic Acid

A highly active and stable praseodymium-polyvinylpyrrolidone (Pr-PVP)-co-doped nanoTiO2 film/titanium matrix was successfully fabricated for the electrocatalytic reduction of oxalic acid. The structure, morphology, and electro catalytic activity of the as-synthesized Pr-PVP-doped nanoTiO2 film on a titanium matrix surface was studied with X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The electro catalytic properties were assessed by studying the electro reduction of oxalic acid on Pr-PVP-co-doped nanoTiO2 film electrodes. The results showed a high yield of glyoxylic acid (82.6%) and a high current efficiency (81%) with galvanostatic preparative reduction. Based on the results, Pr-PVP-modified nanoTiO2 film has a large electrochemical active surface area and small charge transfer resistance. The good electro catalytic performance of Ti/Pr-PVP-nano TiO2 makes it promising for use as an electrode in the electro catalytic reduction of oxalic acid.

Visible Light Excited Catalysis and Reusability Performances of TiO2@Pr:Y2SiO5 Upconversion Materials

To get high efficiency photodegradation on pollutants under visible light, Pr(III) doped Y2SiO5 upconversion materials and anatase TiO2 nanofilm coated Pr:Y2SiO5 composite have been prepared by using a sol-gel method. XRD and SEM test results indicated that TiO2 nanofilm was well coated on Pr:Y2SiO5 to form TiO2@Pr:Y2SiO5 composite particles with the sizes of 0.5–1.0 μm. To avoid secondary pollution resulting from incomplete recovery of catalyst particles, TiO2@Pr:Y2SiO5 was loaded on the glass fiber filters by using a dip-coating method. It is found that the catalyst particles were embedded into the carrier firmly, even after having been reused for 6 times. The luminescence intensities of TiO2@Pr:Y2SiO5 were getting down sharply with the coating contents of TiO2 increased, which was attributed to the adsorption of the luminescence by the TiO2 film in situ. As a result, TiO2@Pr:Y2SiO5 with 4% TiO2, which presented lowest luminescence intensity, showed the highest efficiency on the photodegradation of nitrobenzene wastewater. The catalysts loaded on glass fiber filters showed excellent reusability on the photodegradation of nitrobenzene and presented a photodegradation rate of 95% at the first time and up to 75.9% even after 6 times of reusing by the treatment time of 12 h.

Morphological influence of TiO2 nanostructures (nanozigzag, nanohelics and nanorod) on photocatalytic degradation of organic dyes

Hierarchical nanostructures have drawn significant attention and incredible performance in photodriven chemical conversion area due to its unique physicochemical properties. Herein, we study the morphological influence of TiO2 nanostructures on photocatalytic degradation of different organic dyes methyl blue, methyl violet and methyl orange present in industrial wastewater. Nanorod, nanohelics and nanozigzag TiO2 nanofilms were fabricated by using galancing angle deposition technique (GLAD). TiO2 nanofilms were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and raman analysis. BET surface area analysis were carried out by using nitrogen adsorption desorption curves. The results show that TiO2 morphology had great influence on photocatalytic degradation of organic dyes due to difference in specific surface area and pore volume of nanostructures. The photocatalytic degradation experiments were carried out for three hours under UV–vis light irradiation. Catalysis recycling and organic dyes concentration influence were also studied. In case of high concentration of organic dyes, negligible degradation rate is observed. TiO2 nanozigzag films show better degradation performance than nanohelics and nanorod due to presence of large surface area for reaction, higher porosity with dispersion of active sites at different length scales of pores and presence of oxygen vacancies.

PH deeds on structural, optical, electrical and gas sensing performance of TiO2 nanofilms by automated nebulizer spray pyrolysis technique

In this present study, TiO2 nanofilms were deposited at 773K by using titanium tetra isopropoxide as precursor and ethanol as solvent with the variation of pH for x=2.50, 6.50, and 10.50 through automated nebulizer spray pyrolysis (ANSP) technique. The properties of Structural (XRD), Topography (AFM) and surface morphology (FESEM) of the film shows the average particle size, average roughness and particle shape were drastically changed with respect to electrolyte pH parameter. Anatase phase of polycrystalline tetragonal structure was revealed by structural (XRD) and X-ray photoelectron study (XPS). The XPS study confirms the films that not detected with the other trace of impurity except carbon. The optical transmittance decreased at higher pH and their band gap energy in the range of 3.29–3.43eV was obtained with the change in electrolyte pH parameter for all the TiO2 film. The electrical study of dielectric constant, tan δ is continue to decrease with increase the frequency and the maximum dielectric constant and tan δ value observed as ∼41.73 and ∼03.62 for pH=6.50. The adsorption and desorption of various gas sensing performance of TiO2 film were analysed with the function of temperature and the high sensing response of NH3 where noted.

High Sensitivity Refractometer Based on TiO₂-Coated Adiabatic Tapered Optical Fiber via ALD Technology.

Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractometer based on an adiabatic tapered optical fiber. Different thicknesses of titanium dioxide (TiO2) nanofilm were coated around the tapered fiber precisely and uniformly under different deposition cycles. Attributed to the higher refractive index of the TiO2 nanofilm compared to that of silica, an asymmetric Fabry–Perot (F-P) resonator could be constructed along the fiber taper. The central wavelength of the F-P resonator could be controlled by adjusting the thickness of the TiO2 nanofilm. Such a F-P resonator is sensitive to changes in the surrounding refractive index (SRI), which is utilized to realize a high sensitivity refractometer. The refractometer developed by depositing 50.9-nm-thickness TiO2 on the tapered fiber shows SRI sensitivity as high as 7096 nm/RIU in the SRI range of 1.3373–1.3500. Due to TiO2’s advantages of high refractive index, lack of toxicity, and good biocompatibility, this refractometer is expected to have wide applications in the biochemical sensing field.