Thin Titania Research Articles

Growth of TiO2:Au thin films on Si substrates by Spin coating method

Thin titanium dioxide: gold (TiO2:Au) films are grown on n-type Si(100) substrates by spin coating, using 97% pure titanium (IV) isopropoxide [TTIP, Ti(O(C3H7)4] as a metal-organic precursor and powdered gold oxide (Au2O3) as a dopant. The Au2O3 was dissolved in tetrahydrofuran (C4H8O) to a concentration of 0.2 M, and this was then mixed with the TTIP in a 1:4 ratio. This experiment used a TTIP buffer layer to reduce lattice mismatch between the substrate and the film. The growth temperature was varied from 400°C to 550°C with an interval of 50 °C during deposition of TiO2:Au films, in which the experimental results show that the grown film exhibited rutile (002) (R (002)) crystal planes for all temperature conditions. In addition, while the films were grown at a temperature of 400 °C and 450 °C showed anatase (211) planes, the layers realized with a temperature of 450°C and 550°C exhibited rutile (200) planes. Increasing the amount of Au incorporation within a film will decrease its bandgap energy. The 500°C films showed a crystalline domain size in the R (002) plane of around 20.38 nm, making it a promising candidate base material for use in carbon monoxide (CO) gas sensors.

Anti-galling β-SiC coating dies for fine cold forging of titanium

β-SiC coating die and punch were employed for forging of titanium wire to triangular bar in high reduction of thickness by 35 %. CNC (computer numerical control) stamper was utilized to describe the elasto-plastic behavior of titanium wire in dry forging. Precise analyses on the contact interface between SiC coating and titanium work were made to investigate the mass transfer of metallic titanium as well as titanium oxide debris particles onto SiC coating surface. In particular, element mapping and Raman spectroscopic analyses were performed to describe the formation of thin titanium oxide film as well as the agglomeration of unbound carbon on the SiC coating punch.

Ceramic coating on Ti-6Al-4V by plasma electrolytic oxidation in molten salt: Development and characterization

The plasma electrolytic oxidation (PEO) method is one of the most promising methods for the formation of oxide coatings on metallic substrates. This process is usually conducted in an aqueous solution electrolyte; however, it has several disadvantages, such as heating-up of the system and the formation of the undesired chemical components. This study addresses these disadvantages by conducting the process in a molten salt electrolyte. The surface morphology, phase composition, hydrophobicity, and the effects of process current frequency were examined. Thin titanium oxide, rutile and anatase, coating of 2–2.5 μm was formed on the treated Ti-6Al-4V alloys. The potentiodynamic polarization test evaluated the highest polarization polarization resistance for the alloy obtained using current frequency of 150 Hz which was 364×10 4 Ω·cm 2 in comparison with the pristine alloy which was 6.93×10 4 Ω·cm 2 . Electrochemical impedance spectroscopy revealed the same behavior. Morphology evaluation revealed that the structure of this coating contained uniform sub-micron porosity and its surface exhibited the highest hydrophobicity. • TiO 2 coating was developed by plasma electrolytic oxidation in nitrate salt. • Effect of PEO current frequency on structure and performance was examined. • The highest PEO coating properties were obtained using current frequency of 150 Hz. • The highest contact angle was obtained on the most compact titanium oxide coating. • The highest corrosion resistance was obtained on the most uniform coating.

Photocatalytic CO2 reduction to CH4 on iron porphyrin supported on atomically thin defective titanium dioxide

The synergistic effect of OVs and FeTPP on 2D TiO2 improves the efficiency and selectivity of CO2 photoreduction to CH4.

TiO2/gold-graphene hybrid solid core SPR based PCF RI sensor for sensitivity enhancement

We propose a d-shaped photonic crystal fiber (PCF) refractive index (RI) sensor based on surface plasmon resonance (SPR), capable to work in both visible and near-infrared (NIR) wavelength (410–1790 nm) region. Gold (Au) is deposited on the flat outer surface of the PCF to excite the plasmons. A thin titanium dioxide (TiO2) layer is sandwiched between fiber surface and gold layer so that the gold nanoparticles can strongly attach with the fiber surface. It also helps to shift the resonance wavelength of the proposed sensor to near IR region which is much advantageous for biosensing. A thin graphene layer is applied on Au to assist adsorption of ample biomolecules on its surface. It also prevents gold from oxidation. Simulation results show the theoretical maximum wavelength sensitivity of 48,900 nm/RIU and average sensitivity of 13112.5 nm/RIU in the RI rage of 1.32−1.40. Besides this, the proposed sensor shows the higher amplitude sensitivity of 738.74/RIU with high resolution and maximum figure of merit (FOM) of 7.604×10-6RIU and 611.25/RIU, respectively. These promising outcomes of the proposed sensor make itself to be a potential candidate for the various analyte (organic chemicals, biomolecules) detection. Moreover, the fabrication feasibility of our proposed D-shaped sensor becomes easier than the circular PCF sensors as it avoids the internal coating of the plasmonic metals.

Dry Cold Forging of Pure Titanium Wire to Thin Plate with Use of β-SiC Coating Dies.

Dense β-SiC coating with 3C-structure was utilized as a dry cold forging punch and core-die. Pure titanium T328H wires of industrial grade II were employed as a work material. No adhesion or galling of metallic titanium was detected on the contact interface between this β-SiC die and titanium work, even after this continuous forging process, up to a reduction in thickness by 70%. SEM (Scanning Electron Microscopy) and EDX (Electron Dispersive X-ray spectroscopy) were utilized to analyze this contact interface. A very thin titanium oxide layer was in situ formed in the radial direction from the center of the contact interface. Isolated carbon from β-SiC agglomerated and distributed in dots at the center of the initial contact interface. Raman spectroscopy was utilized, yielding the discovery that this carbon is unbound as a free carbon or not bound in SiC or TiC and that intermediate titanium oxides are formed with TiO2 as a tribofilm.

Improving stress corrosion cracking behavior of AZ31 alloy with conformal thin titania and zirconia coatings for biomedical applications

Magnesium and its alloys have been widely studied as materials for temporary implant devices. However, corrosion-assisted cracking phenomena such as stress corrosion cracking (SCC) continue to prevent their mainstream use. For the first time, we explore the SCC susceptibility of Atomic Layer Deposition (ALD) coated AZ31 alloys in Simulated Body Fluid (SBF). Conformal 100 nm coatings of titania and zirconia were deposited on standard dogbone specimens and subjected to slow strain rate tests at 3.5 10-6 s-1 and a temperature of 37 °C. Remarkably, the SCC susceptibility index IUTS was reduced by 6% and 40% and the Iε was reduced by more than 70% and 76% with a titania and zirconia coating, respectively. Potentiodynamic polarization, hydrogen evolution and fracture behavior of the samples revealed the drastic corrosion reduction to be the main reason for the susceptibility reduction. We discuss the observed SCC behavior of our samples in light of the coatings’ electrochemical activities, wettabilities, surface integrities and mechanical properties. This straightforward conformal surface treatment can be useful as a workaround for one of the major bottlenecks of biomedical Mg based implants and hence provides a possible pathway for making them more commonplace in the field.

Using Hot Electrons and Hot Holes for Simultaneous Cocatalyst Deposition on Plasmonic Nanostructures

Hot electrons generated in metal nanoparticles can drive chemical reactions and selectively deposit cocatalyst materials on the plasmonic hotspots, the areas where the decay of plasmons takes place and the hot electrons are created. While hot electrons have been extensively used for nanomaterial formation, the utilization of hot holes for simultaneous cocatalyst deposition has not yet been explored. Herein, we demonstrate that hot holes can drive an oxidation reaction for the deposition of the manganese oxide (MnOx) cocatalyst on different plasmonic gold (Au) nanostructures on a thin titanium dioxide (TiO2) layer, excited at their surface plasmon resonance. An 80% correlation between the hot-hole deposition sites and the simulated plasmonic hotspot location is showed when considering the typical hot-hole diffusion length. Simultaneous deposition of more than one cocatalyst is also achieved on one of the investigated plasmonic systems (Au plasmonic nanoislands) through the hot-hole oxidation of a manganese salt and the hot-electron reduction of a platinum precursor in the same solution. These results add more flexibility to the use of hot carriers and open up the way for the design of complex photocatalytic nanostructures.

A study of the electrochemical reactivity of titanium under cathodic polarization by means of combined feedback and redox competition modes of scanning electrochemical microscopy

The effect of cathodic polarization on the electrochemical behavior of the thin titanium dioxide film formed by anodic pretreatment over pure commercial titanium metal for biomaterial application was investigated in situ using scanning electrochemical microscopy (SECM). Quantitative information on the electron transfer rates (keff) at the titanium surface was obtained using the feedback operation of SECM with ferrocene-methanol (FcMeOH) as electrochemical mediator. An increase of keff values with the increase of the negative polarization was detected, a feature that correlates well with the decrease of titanium oxide resistance with increasing cathodic polarization observed using electrochemical impedance spectroscopy (EIS). In addition, SECM operation in the redox competition mode proved that hydrogen was absorbed in the surface oxide film leading to changes in conductivity and electrochemical reactivity.

Binder‐Free TiO2‐Coated Polypropylene Separators for Advanced Lithium‐Ion Batteries

Modification with inorganic nanoparticles is a common method to enhance the thermal stability, electrolyte wettability, and overall functionality of commercial separators. However, the binders frequently used reduce the specific capacity of batteries and tend to swell in the electrolyte. Herein, a novel type of inorganic thin layer–coated separator that is easy to prepare and does not require a binder is designed. After treating by UV/O3, a thin titania layer is uniformly deposited on the surface of a commercial polypropylene (PP) separator by a facile sol–gel coating method. The thin TiO2 layer considerably improves the thermal stability of the separator, and there is no obvious shrinkage when the separator is heated at 170 °C for 30 min. At the same time, the electrolyte wettability is greatly improved after modification, which increases the Li+ migration rate. A LiFePO4/Li battery with the PP@TiO2 separator shows superior rate capability and cycle performance at high currents; particularly, it demonstrates a high capacity of 92.6 mAh g−1 at 15 C. The modified separator simultaneously improves the safety and electrochemical performance of the batteries, which will help to achieve the goal of preparing high‐safety, high‐capacity lithium‐ion batteries (LIBs).

Hierarchically-Structured Ti/TiO2 Electrode for Hydrogen Evolution Synthesized via 3D Printing and Anodization

Hierarchically-structured, electro-catalysts consisting of a titanium core with controlled macro-porosity and a thin titania surface-layer with controlled nano-porosity were synthesized via combination of additive manufacturing and in-situ anodization. The electrodes were tested for hydrogen evolution reaction and depicted competitive electro-catalytic activities, with Tafel slopes between 40 and 56 mV dec-1. The electrodes also depicted competitive onset and over potentials when compared with other electrode alternatives. The synthesis approach for the electro-catalysts reported in this work is being extended to other metal/metal-oxide pairs and applications.

HOR Activity of Pt-TiO2-Y at Unconventionally High Potentials Explained: The Influence of SMSI on the Electrochemical Behavior of Pt

The formation of strong metal support interactions (SMSI) is known for many metal/metal oxide systems and its consequences are well established in the field of heterogeneous catalysis, but this knowledge has only been recently transferred to the field of electrocatalysis. In this study, Pt was deposited via atomic layer deposition (ALD) onto TiO2−Y, which allowed a good control of the particle size through the number of ALD cycles. During the ALD process, a thin-film of reduced titania is formed on the Pt surface, which leads to SMSI effects. With increasing Pt particle size, the fraction of the titania-covered Pt surface decreases. As a result, the extent of platinum oxide formation in cyclic voltammetry (CV) measurements scales with the size of the Pt particles. The influence of these thin titanium oxide films, which cover the Pt surface, on the catalytic behavior with respect to oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), CO oxidation and oxygen evolution reaction (OER) is investigated by using an RDE setup. The covering TiOX thin-films reduce the ability to catalyze ORR, OER and CO oxidation, while it does not influence the HOR and Pt H-UPD formation. These findings indicate that proton and hydrogen transport are possible through the thin TiOX film, while oxygenated species suffer from transport limitations through the thin-film. Due to this selective permeability, these materials are able to oxidize hydrogen well beyond 1.2 VRHE.

Light-improved glucose sensing on ordered Au-Ti heterostructure

Non-enzymatic electrochemical platforms sensitive towards glucose presence have attracted a worldwide attention during last decades. We report on influence of solar light onto response of gold-titanium heterostructures prepared via controllable approach. The material based on Au nanoparticles orderly distributed over the structured titanium foil was obtained by electrochemical anodization followed by chemical etching, magnetron sputtering of gold and finally thermal treatment in the continuous regime. It is proven that the applied synthesis route leads to the enhanced visible light absorption boosting material photoactivity. Fabricated electrode immersed in the glucose containing solution and exposed to the solar light exhibits superior increase of oxidation current comparing to pristine substrate before thermal annealing. Photosensor is characterized by broad linear response up to 40 mM of glucose, limit of detection of 0.2 and 0.1 mM and sensitivity of 3.08 and 0.92 μA/cm2 in NaOH and PBS, respectively. It is concluded that the electrode exhibits enhanced performance taking advantage from plasmon resonance effect and the presence of thin titania passive film. Moreover, obtained material is stable under prolonged illumination and was verified in the presence of blood serum sample. Overall, presented results suggest that the impact of solar light should be taken into account during works on sensing devices.

Titanium dioxide nanoparticles and thin films deposited by an atomization method

Purpose: The article presents the results of research on titanium dioxide synthesized by a sol-gel method that is an easy process enabling the control of the shape and size of particles The purpose of this article is to examine titanium dioxide nanoparticles and thin films deposited by an atomization method. Design/methodology/approach: Titanium dioxide sol was synthesized by using titanium isopropoxide as a precursor. Optical properties were measured by a UV-Vis spectrometer. Structural studies were performed by Raman spectroscopy. Qualitative analysis was performed by the EDS. Surface morphology of nanoparticles and thin films was performed by the SEM technique. Findings: The sol-gel method allows the formation of uniform nanoparticles and thin films of titanium dioxide. The atomization method is a successful method for the deposition of sol to the surface of substrates. Research limitations/implications: The next step in the research will be to investigate the obtained thin films in dye-sensitized solar cells as a semiconductive layer. Practical implications: Unique properties of produced titanium dioxide nanostructural materials have caused the interest in them in such fields as optoelectronics, photovoltaics, medicine and decorative coatings. Originality/value: Titanium dioxide thin films and nanoparticles were synthesized using the sol-gel method and then deposited by the atomization method.

Effect of Al co-doping on the luminescence properties of Nd3+-doped TiO2 thin films

Co-doping Aluminium (Al) with neodymium (Nd) is shown to have a sensitizing effect on the rare earth luminescence in thin film titanium dioxide (TiO2) host materials. Whilst the Al co-doping has the effect of quenching the direct (resonantly) excited, steady state photoluminescence from Nd3+ emitting centers, for indirect (non-resonant) excitation, the emission is enhanced with increasing Al. Time-resolved PL measurements reveal a decrease in both the excitation/de-excitation rates (increases in lifetime) with increasing Al co-doping, confirming the indirect nature of excitation and implying a suppression of non-radiative de-excitation of the Nd3+ centers in TiO2. Suppression of non-radiative processes by Al is considered to be the result of reduced rare earth clustering, which is known to promote de-excitation via energy migration and thus has important implications for improved efficiency infra-red LED materials.

Photocatalytical decoration of thin titania coatings with silver nanostructures provides a robust and reproducible SERS signal

AbstractCost‐effective photocatalytic synthesis was used to fabricate silver nanostructures (AgNSs) on TiO2 coatings (AgNSs/TiO2) with plasmonic properties. In this study, the AgNSs growth controlled by variation of the concentration of Ag+ ions, hole scavengers, and ultraviolet illumination was systematically studied in terms of morphological characterization, extinction, and surface‐enhanced Raman spectroscopy (SERS). These structures with well‐defined and high photocatalytic properties show a plethora of shapes (from spherical to polygonal objects), diameter (8–108 nm), and surface coverage (12–62%). Morphological properties strongly affect nanoplasmonic features as revealed by electronic and SERS spectra. Surface enhancement of Raman signal was probed by using 4‐mercaptobenzoic acid to elucidate the stability and uniformity of the designed substrates. A detailed examination and correlation of geometrical parameters and SERS performance indicate synergistic contribution of the formation of hot spots between AgNSs. Some of the fabricated AgNSs present a very good homogeneity and reproducibility as well as long‐time stability. The highest enhancement factor in SERS was obtained for the Ag–TiO2 hybrids with a diameter and surface coverage of AgNSs less than 30 nm and larger than 50%, respectively.

Surface coating with Li-Ti-O to improve the electrochemical performance of Ni-rich cathode material

Abstract LiNi0.8Co0.1Mn0.1O2 is a promising cathode material for lithium-ion batteries due to its high capacity, high energy density and low cost. However, LiNi0.8Co0.1Mn0.1O2 suffers from an aggressive side reaction with electrolyte, resulting in poor cycling performance, large polarization and fast voltage degradation. To overcome these drawbacks, we use an acid coprecipitation method to prepare rod-shaped LiNi0.8Co0.1Mn0.1O2, and introduce a thin and uniform lithium titanium oxide layer on the surface by a solvothermal method. The 3 mol% lithium titanium oxide-coated LiNi0.8Co0.1Mn0.1O2 exhibits a much higher capacity retention (88.6%) than the pristine material after 100 cycles, and the polarization and voltage degradation of the Ni-rich cathode are largely alleviated. Furthermore, at an elevated temperature of 65 °C, the capacity retention of lithium titanium oxide–coated LiNi0.8Co0.1Mn0.1O2 is 81.1% after 50 cycles, which is much higher than that of pristine LiNi0.8Co0.1Mn0.1O2 (only 52.0%). These results suggest that the surface doping of Ti4+ and the introduction of the lithium titanium oxide layer help to improve the structure stability and mitigate the side reactions on the electrode-electrolyte interface, resulting in good electrochemical performance.

Integration of Nanoemitters onto Photonic Structures by Guided Evanescent-Wave Nano-Photopolymerization

In this article, we demonstrate the feasibility of self-positioning nanoemitters onto optical waveguides by visible-light nanoscale photopolymerization. A light-sensitive material containing nanoemitters is photopolymerized at interfaces by using the evanescent field of the light propagating in photonic structures. By exploiting this method, it is possible to pattern polymeric ridges containing CdSe/ZnS nanocrystals (NCs) directly on top of optical guiding structures. Photopolymerization experiments have been performed in the case of a single ion-exchange glass waveguide (IEx WG) and of a double waveguide made of the IEx WG with a thin titanium dioxide film fabricated on top of it. Atomic force microscopy (AFM) and spectroscopy analyses highlight the reliability and reproducibility of the fabrication technique. Continuous ridges of controlled thickness have been realized on top of a single waveguide interface with thicknesses as small as 18 nm, thus thick enough to contain only a photoluminescent NC monolayer in the vertical direction. In the presence of the double waveguide (TiO2 layer on top of the IEx WG), AFM measurements reveal that the thickness of the photopolymerized ridge has a sinusoidal modulation. This is due to a light beating phenomenon theoretically predicted in the case of light propagating in coupled waveguides. In our case, the light beating can be efficiently exploited to photopolymerize ridges with modulated thickness. Overall, the flexibility of the reported nanoscale fabrication technique paves the way toward the controlled positioning of single nanoemitters in proximity of nanoantennas or other elaborate plasmonic/photonic structures.

Nitrogen-Doped Titanium Dioxide Thin Films Formation on the Surface of PLLA Electrospun Microfibers Scaffold by Reactive Magnetron Sputtering Method

Nitrogen-doped thin titanium dioxide films formed by the reactive magnetron sputtering method on the surface of PLLA electrospun microfibers scaffold were investigated. It was shown that the chemical composition of the films is shifting from titanium dioxide (TiO2) composites saturated with C–NH, C=N, N–C=N and HN–C=O compounds to solid solutions of titanium oxides (TixOy) and titanium oxynitrides (TiOxNy) with the increased time of the treatment. An empirical model describing changes in the chemical composition of the surface due to the treatment was proposed. It was shown that the modification of the PLLA microfibers scaffolds surface improves cell-scaffold and cell–cell interactions with the highest number of viable adherent cells observed on the scaffold treated for 4 min.

A Hi-Bi Ultra-Sensitive Surface Plasmon Resonance Fiber Sensor

In this paper, a simple, miniature, and highly sensitive photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor is proposed. The target analyte and the plasmonic material are at the outer surface of the fiber making practical applications feasible. A 30-nm gold (Au) layer supports surface plasmons. A thin titanium dioxide (TiO 2 ) layer is used to assist adhesion of Au on the glass fiber. The fiber cross section is formed purely by circular-shaped holes simplifying the preform manufacturing process. A high-birefringence (hi-bi) fiber is obtained by means of an array of air holes at the center of the fiber. A finite element method (FEM) is employed to analyze the surface plasmon properties of the proposed PCF-SPR sensor. By optimizing the geometric parameters, a maximum wavelength sensitivity (WS) of 25 000 nm/RIU and an amplitude sensitivity (AS) of 1411 RIU -1 for a dielectric refractive index (RI) range of 1.33-1.38 are obtained. Moreover, an estimated maximum resolution of 4 × 10 -6 and a figure of merit (FOM) of 502 are obtained that ensures high detection accuracy of small refractive index (RI) changes. Owing to its sensitivity and simple architecture, the proposed sensor has potential application in a range of sensing application, including biosensing.