Titania Films Research Articles

Recent Advances in the Raman Investigation of Structural and Optical Properties of Graphene and Other Two-Dimensional Materials

This research work presents our recent advancements in the study of graphene and other two-dimensional (2D) materials. This review covers studies on graphene oxide (GO) thin films deposited on various substrates, including titanium and silver thin films. The analysis reveals the role of surface-enhanced Raman scattering (SERS) and the influence of film thickness and laser intensity on the observed Raman peaks. Investigations of a silver/GO/gold sandwich structure demonstrate the presence of sharp Raman modes attributed to localized surface plasmon resonances. This review also discusses the characterization of exfoliation-synthesized graphene nanoplatelet (GNPs) thin films and of single-layer graphene deposited via chemical vapor deposition (CVD). The optical properties of molybdenum disulfide (MoS2) films are also explored. The utilization of micro-Raman spectroscopy provides valuable insights into the structural and optical properties of graphene and other 2D materials. These results hold the potential to drive advancements in various applications, such as electronics, photonics, and nanocomposites.

Chemical Design of Efficient Photoelectrodes by Heterogeneous Nucleation of Carbon Dots in Mesoporous Ordered Titania Films

Chemical Design of Efficient Photoelectrodes by Heterogeneous Nucleation of Carbon Dots in Mesoporous Ordered Titania Films

Synergistic effects of Mg doping on TiO2 for improved toxic gas sensing performance at room temperature

The gas sensing characteristics of magnesium (Mg)-doped titanium dioxide (TiO2) films were investigated using a spray pyrolysis method. TiO2 Thin films with varying Mg doping concentrations (0, 2.5, and 5 weight percentages) were deposited and tested for their gas detection ability to organic compounds such as ethanol, butanol, toluene, xylene, and formaldehyde at room temperature. Results disclosed that introducing Mg into TiO2 enhanced the gas sensing characteristics, particularly for formaldehyde. Mg-doped TiO2 film improved the change in electrical resistance during gas adsorption, leading to an increased response in formaldehyde detection. Additionally, XRD revealed the crystal structure, while Raman spectroscopy provided insights into molecular vibrational modes of the fabricated films. FESEM allowed for high-resolution imaging of surface morphology, and atomic force microscope assessed surface roughness and other properties of the as deposited samples. UV-Vis spectroscopy was utilized to examine the optical characteristics. The collective results strongly indicated that the introduction of Mg significantly improved the gas-sensing capabilities of TiO2 films, making them highly promising for various gas-sensing applications.

Preparation, optimization and electrochromic properties of dual-band device with four modes

A dual-band electrochromic device with four modes was fabricated to selective modulate the transmittance from visible to near-infrared bands for the energy-saving field. The new LiClO4 + TBACl + AgNO3 electrolyte was prepared to respectively regulate the redox reactions of silver ion and lithium ion to prove the four modes of the device. The dual-band device with a sandwich structure was fabricated by the titanium dioxide electrochromic film, the gallium doped zinc oxide ion storage film and the LiClO4 + TBACl + AgNO3 electrolyte. The titanium dioxide and gallium doped zinc oxide films were prepared by a nanoparticle deposition system, which is an environmentally friendly dry deposition technique. By controlling the supplied potential, the redox reactions of silver ion and lithium ion present four modes, including transparent mode, warm mode, cold mode and full block mode. For warm mode, the localized surface plasmon resonance effect was excited by generating silver nanoparticles using two-stage potential. Moreover, the titanium dioxide film with high surface roughness shown the large light scattering effect, the transmittance of ∼0% at whole wavelengths was obtained in full block mode. The electrochromic device shown the large transmittance modulation (71%) and excellent cyclic stability (600 cycles). Therefore, it is proved that the transmittance can be adjusted at a specific wavelength by the electrochromic device, which provides an effective way for developing dual-band smart devices to reduce energy consumption.

Self-assembled gold nanoribbons via surface plasmon polaritons: The role of femtosecond laser

Plasmonic nanostructures have emerged as a critical component in broad fields ranging from optical modulation to biosensing and energy harvesting. Here, an ultrathin titanium (Ti) film (8 nm) is introduced between the gold (Au) film and fused silica (SiO2) substrate to facilitate energy deposition of the surface plasmon polariton (SPP) waves excited at the Ti/SiO2 interface under 1030 nm fs laser irradiation. The femtosecond laser-SPPs patterning results in the formation of Au nanoribbons with a width of about 270 nm and a spatial period of about 700 nm. Notably, centimeter-scale, self-assembled nanoribbons of high uniformity are achieved within several minutes. The localized surface plasmon resonance (LSPR) induced absorption peak is measured at the near-infrared band, confirming the high quality of the fabricated plasmonic nanostructures. Our findings suggest that the femtosecond laser-SPPs patterning technique represents a promising approach for the rapid and cost-effective production of large-scale plasmonic nanostructures.

Characterising Hydroxyapatite Deposited from Solution onto Novel Substrates: Growth Mechanism and Physical Properties.

Whilst titanium, stainless steel, and cobalt-chrome alloys are the most common materials for use in orthopaedic implant devices, there are significant advantages in moving to alternative non-metallic substrates. Substrates such as polymers may have advantageous mechanical biological properties whilst other substrates may bring unique capability. A key challenge in the use of non-metal products is producing substrates which can be modified to allow the formation of well-adhered hydroxyapatite films which promote osteointegration and have other beneficial properties. In this work, we aim to develop methodology for the growth of hydroxyapatite films on surfaces other than bulk metallic parts using a wet chemical coating process, and we provide a detailed characterisation of the coatings. In this study, hydroxyapatite is grown from saturated solutions onto thin titanium films and silicon substrates and compared to results from titanium alloy substrates. The coating process efficacy is shown to be dependent on substrate roughness, hydrophilicity, and activation. The mechanism of the hydroxyapatite growth is investigated in terms of initial attachment and morphological development using SEM and XPS analysis. XPS analysis reveals the exact chemical state of the hydroxyapatite compositional elements of Ca, P, and O. The characterisation of grown hydroxyapatite layers by XRD reveals that the hydroxyapatite forms from amorphous phases, displaying preferential crystal growth along the [002] direction, with TEM imagery confirming polycrystalline pockets amid an amorphous matrix. SEM-EDX and FTIR confirmed the presence of hydroxyapatite phases through elemental atomic weight percentages and bond assignment. All data are collated and reviewed for the different substrates. The results demonstrate that once hydroxyapatite seeds, it crystallises in the same manner as bulk titanium whether that be on a titanium or silicon substrate. These data suggest that a range of substrates may be coated using this facile hydroxyapatite deposition technique, just broadening the choice of substrate for a particular function.

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.

Features of Structuring and Ablation of Thin Titanium Films by Femtosecond Laser Pulses

Features of Structuring and Ablation of Thin Titanium Films by Femtosecond Laser Pulses

Colloidal TiO2 Nanorod Films Deposited Using the MAPLE Technique: Role of the Organic Capping and Absence of Characteristic Surface Patterns

Thin films of titanium dioxide (TiO2) nanocrystals, widely acknowledged for their unique physical-chemical properties and functionalities, are used in disparate technological fields, including photovoltaics, sensing, environmental remediation and energy storage. In this paper, the preparation of thin films consisting of anatase-phase TiO2 nanorods deposited using the matrix-assisted pulsed laser evaporation (MAPLE) technique and their characterization in terms of morphology, elemental composition and wettability are presented and discussed. Particular attention is paid to the effects of the laser fluence, varied over a broad range (F = 25, 50, 100 mJ/cm2), and to the role of the capping surfactants bound to the surface of the nanorod precursors. Whereas increasing fluence favored a partial removal of the surface-bound surfactants, a post-growth UV-light-driven photocatalytic treatment of the films was found to be necessary to reduce the incorporated fraction of organics to a further substantial extent. It was noteworthy that, under our experimental conditions, the distinctive surface patterns and roughness that commonly degrade the morphology of films deposited using the MAPLE technique were not observable. This previously unreported experimental evidence was rationalized on the basis of the interaction dynamics between solvent/solute droplets ejected from the laser-irradiated target and the rough surfaces of the growing film.

Quantification of the Stability of ALD-Grown TiO2 Protective Coatings on Photoanodes for Solar Water Splitting

Semiconducting photoabsorbers used in photoelectrochemical applications often exhibit low stability under operating conditions. One strategy implemented in recent years to prevent corrosion of photoelectrodes is the application of thin films of titanium dioxide (TiO2), coated by atomic layer deposition (ALD). However, the stability of these coatings under photoelectrochemical conditions is also limited. We are using spectroscopic ellipsometry (SE) and in-situ atomic force microscope (AFM) characterization[1, 2] in order to quantify the influence of the coating process parameters and of post-deposition treatments on the degradation of these protective layers. Here we show our recent investigations under anodic operation in acidic environment. For fully amorphous TiO2 layers, a significant contributor to the corrosion is a purely chemical process, with an activation energy of 57 kJ/mol. Furthermore, the degradation rate doubles upon illumination under simulated sunlight. With increasing pH, the stability increases significantly. Partially crystalline protective coatings exhibit improved stability under operating conditions in sulfuric acid.

(Invited) Redox Chemistry Driven by Atmospheric Pressure Plasma Jet

Plasmas may be considered as mixed ionic and electronic conductors. From an electrochemical point of view, a conducting gas presents a wonderful opportunity to explore redox reactions without all the restrictions a solvent medium provides. Identifying a plasma medium suitable to allow electrochemical measurements can be technically challenging, often due to the electrical energy used to create the plasma. However, atmospheric pressure plasma jets (APPJ)1&2 have been shown to be accessible and convenient as laboratory plasma sources. They present a medium that may be considered as an electrode, due to the presence of electrons or as electrolytes, due to their electrical conduction.3 Although its definition is not too important, the presence of free electrons gives an opportunity to drive reduction processes.The interesting aspect of non-thermal plasmas, and the root of their interesting chemistry, is partly due to the imbalance of thermal kinetic energy distribution between the electron and all the other species, neutral or ionized. As a consequence plasma jets are found in routine industrial applications such as etching or cleaning of surfaces for adhesion promotion. Furthermore, there is a growing body of evidence to suggest that APPJ may be used for the treatment of solid tumors. These highly energized electrons can drive redox reactions, as well as other chemical reactions, at solid or liquid can be unexpected. In this presentation I will explore the use of APPJ for reduction of metal oxides under potentiostatic control and material synthesis.4-6 References Ratcliffe, L.V., et al., Surface analysis under ambient conditions using plasma-assisted desorption/ionization mass spectrometry. Analytical Chemistry, 2007. 79(16): p. 6094-6101.Golda, J., et al., Concepts and characteristics of the 'COST Reference Microplasma Jet'. Journal of Physics D-Applied Physics, 2016. 49(8).Rumbach, P.; Bartels, D. M.; Sankaran, R. M.; Go, D. B., The solvation of electrons by an atmospheric-pressure plasma. Nature Communications 2016, 6, 7248.Sener, M. E., Quesada Cabrera, R., Parkin, I.P., Caruana, D. J., Facile formation of black titania films using an atmospheric-pressure plasma jet, Green Chemistry 2022 , 24, 2499-2505.Sener, M. E., Palgrave, R., Quesada Cabrera, R., Caruana, D. J., Patterning of Metal Oxide thin Films using H2/He Atmospheric Pressure Plasma Jet. Green Chemistry 2020, 22, 1406-1413.Sener, M. E.; Caruana, D. J., Modulation of copper(I) oxide reduction/oxidation in atmospheric pressure plasma jet. Electrochemistry Communications 2018, 95, 38-42.

Effect of surface characteristics of sputtered titanium and niobium thin alloy films on cell growth and adhesion

Titanium (Ti)–niobium (Nb) thin alloy films were prepared by on-chip sputtering. Their surface properties were characterized, and their cell growth and adhesion properties were investigated. Protrusions were observed on the surface of a thin film made of Ti mixed with a small amount of Nb; these protrusions were smaller and more numerous than those on Ti and Nb thin films. Addition of a small amount of Nb enhanced cell adhesion and cell growth compared to those of Ti or Nb thin films. In addition, cell growth and adhesion decreased with an increase in Nb content. Therefore, the stable morphology, negative zeta potential and suitable protrusion size of these Ti–Nb thin alloy films enhance cell adhesion and cell growth on their surfaces.

Electrochemical and microscopic characterization of titanium dioxide electrodes modified with platinum nanoparticles

This study investigates glass/Ti/Pt/TiO2 surfaces, wherein Pt nanoparticles (NPs) were potentiostatically deposited with an amount of Pt that varies based on deposition time. The size and distribution of NPs were analyzed by scanning electron microscopy (SEM). Subsequently, a thicker titanium dioxide film was grown via anodization. Topography and roughness were examined by atomic force microscopy (AFM). Remarkably, TiO2 grows independently of Pt NPs and remains stable under working conditions, including acid, neutral, and alkaline media. Under steady-state conditions, the open circuit potentials (OCPs) of the modified semiconductor/electrolyte interfaces corresponding to 1, 5, and 10 s of electrodeposited Pt, showed a shift of 167 mV, 42 mV, and 24 mV toward more positive values, respectively. Notably, these surfaces exhibit the activity of a Pt quasi-electrode and the band structure of a titanium dioxide semiconductor, making them ideal for use as photoanodes. In addition, it can be highlighted that the methodology employed in the preparation of the surfaces allows for reproducibility.

Synergistic Effect of Strontium Ions and Graphite as Dual Cocatalysts for Enhancing Photocatalytic Activity of Small Area Titania Film Stacked by One-Dimensional Nanofibers

Focusing on the degradation of organic dyes in wastewater, a novel titania composite nanofiber small area film photocatalyst with improvedphotocatalytic activity using strontium ions and graphite as dual cocatalysts has been synthesized by electrospinning and hydrothermal methods.Morphology control, doping causing crystal defect engineering (strontium ion doping), and heterojunction building (graphite surface modification) strategies are simultaneously applied to the synthetic design of new photocatalysts.In degradation tests of rhodamine B, methyl orange, methylene blue, and malachite green, the degradation rate constants were 2.57, 2.85, 3.06, or 3.54 times higher than those of pure titania, respectively.The composite nanofiber small area film exhibited excellent recyclability in fourrecycling tests.The improved photocatalytic activity of titania composite nanofiber small area film is attributed to the morphology of the nanofibers with the addition of more reaction sites, dopingwith more crystal defects, and heterojunctions providing channels for the transfer of photogenerated carriers.Design solutions with the synergistic effects of multiple strategies inform the use of titania in industrial applications.

Atomic Layer Deposition of Titanium Oxide-Based Films for Semiconductor Applications-Effects of Precursor and Operating Conditions.

Two widely used atomic layer deposition precursors, Tetrakis (dimethylamido) titanium (TDMA-Ti) and titanium tetrachloride (TiCl4), were investigated for use in the deposition of TiOx-based thin films as a passivating contact material for solar cells. This study revealed that both precursors are suited to similar deposition temperatures (150 °C). Post-deposition annealing plays a major role in optimising the titanium oxide (TiOx) film passivation properties, improving minority carrier lifetime (τeff) by more than 200 µs. Aluminium oxide deposited together with titanium oxide (AlOy/TiOx) reduced the sheet resistance by 40% compared with pure TiOx. It was also revealed that the passivation quality of the (AlOy/TiOx) stack depends on the precursor and ratio of AlOy to TiOx deposition cycles.

Formation of nanostructured films of titanium dioxide for solar cells sensitized with Roselle flower pigment

In this paper, the study is focused on the assembly and analysis of nanostructured films of titanium dioxide (TiO2) for solar cells sensitized by dyes. An important application of nanostructured films is saved the most among dye because is responsible for absorbing photons. For this reason, the fabrication method of porous TiO2 films is crucial to get a good efficiency of dye-sensitized solar cells (DSSC). The preparation of TiO2 pastes was made by mixing the nanometric and submicron particles of TiO2 with PEG as a plasticizer, α-terpineol, water, and acetic acid to avoid the creation of defects in the films. The screen-printing method was used to build thin films.The analyses of the film were accomplished by employing techniques such as SEM, UV–vis, and adherence, while we used the Van der Pauw method to determine the resistivity of the TiO2 porous film. In conclusion, the ratio PEG/ TiO2 is important for the increase of porosity, so the higher the ratio PEG/ TiO2 higher the porosity thanks to the volume left by the PEG behind the calcination of the films. Three-layer films were obtained by screen-printing with good stability and a thickness of 60 μm.

Thickness dependent physical and optical properties of SILAR deposited titania films

Uniform and crystalline titanium dioxide (TiO2) thin films were obtained using Successive Ionic Layer Adsorption and Reaction (SILAR) technique. Films having varied thicknesses over a range from 700 nm to 1000 nm are deposited on glass substrate. Further TiO2 films were annealed at 673 K for 2 h. X-ray diffraction measurements of both annealed and as deposited films were done to analyze the effect of temperature. Crystallite size and micro strain of the TiO2 films were calculated to study their trend with different thicknesses of the film. Morphological and compositional characteristics are studied by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX) respectively. Images showed formation of uniform film without discontinuities on the base substrate. Optical constants of the films are figured out using UV–vis spectrophotometry. Absorbance spectra showed that as the thickness of the films increased absorbance of the films also increased. Direct and indirect bandgap values of TiO2 films was found using Tauc’s plot.

Influence of water content on structural and electrochromic properties of TiO2 nanotube prepared by anodization

TiO2 nanotubes (TNTs) and bamboo-type TNTs structure films were synthesized via anodization from sputtered titanium (Ti) films on indium tin oxide (ITO) glass. Herein, the anodization process was adjusted electrolyte with different amounts of deionized water and ethylene glycol. The optical and structural properties of all films before and after annealing were investigated, which affected electrochromic application. The increasing deionized water content in electrolytes resulted in an increase in the average diameter and a decrease in the average length of TNTs. Furthermore, the bamboo-type TNTs structure was produced at the deionized water volume condition of 3 vol%. The crystallite size of annealed TNTs (a-TNTs) was calculated from the Scherrer equation, which was enhanced when increasing deionized water. TNTs conditions before annealing showed that the amorphous structure and high energy band gap (Eg) exhibited more electrochromic phenomena than the crystal structure. Due to the disordered arrangement of structures, it was easy to insert ions in TNTs. The bamboo-like structure with separate tubes increased the surface area of the reaction, thus exhibiting the best electrochromic properties with ΔT equal to 12.58%.

Effect of fluoride ion concentration and fluctuating conditions on titanium bipolar plate in PEM water electrolyser environment

In this work, we investigated the corrosion behavior and passive film of commercial pure titanium (TA1) bipolar plates in a simulated proton exchange membrane (PEM) water electrolyser anode environment under different concentrations of fluoride ions and fluctuation conditions. Our findings indicate that the denseness and protective ability of the passive film are weakened by fluoride ions, leading to severe corrosion damage of TA1. The dynamic potential loading altered the anodic reaction process of potentiodynamic polarization, resulting in a reduced corrosion current density. However, the stability of the passive film was still affected, and the Ti-oxides in the passive films decreased.

Demonstration and kinetics of hydrogen loading in titanium thin films

Experimental hydrogen loadings in titanium thin films were compared to the Mintz-Bloch model. 500 nm titanium thin films were deposited with an electron-beam evaporator onto sapphire substrates and were capped with a 10 nm palladium thin film. The titanium films were loaded with hydrogen in a custom Sievert apparatus where the pressure drop showed full hydriding at a hydrogen pressure of 2 bar and loading temperatures of 100 °C, 150 °C, 200 °C and 250 °C. Comparisons of X-ray diffractions of loaded and unloaded films showed the presence of titanium hydride in loaded films. The experimental loadings were compared to the Mintz-Bloch model where the Mintz-Bloch model overpredicted experimental loadings. This was due to the Mintz-Bloch assuming that hydride forms immediately upon hydrogen exposure in the metal. However, the difference between the experimental loading kinetics and Mintz-Bloch model was reduced as loading temperatures increased until the temperature reached 250 °C where some titanium hydride outgassing occurred.