TiO2 Nanocomposite Thin Films Research Articles

Preparation of Transparent ZIF-8/TiO2 Nanocomposite Thin Films for Photocatalytic Applications

Transparent ZIF-8/TiO2 nanocomposite thin films were prepared by a two-stage dip-coating method. TiO2 was first deposited on glass substrates by sol-gel dip-coating. Heat treatment temperature, number of layers and doping metal type/level were optimized in the first step. In the next step, ZIF-8 was grown by solvent based crystallization method on TiO2 layers. Cu, Ce, Fe or Zn doped TiO2 thin films were prepared in order to increase the photocatalytic performance of ZIF-8/TiO2 nanocomposite. The highest photocatalytic methylene blue degradation activities were obtained with the ZIF-8/TiO2 nanocomposite thin films prepared by using 1% Cu or 1% Ce doped TiO2 thin films as the substrates. Both films exhibited 19% dye removal in 1 hour under 254 nm LED light irradiation whereas the dye removal efficiencies were 36% and 29%, respectively, in 1 hour under 365 nm LED light irradiation.

Thermoelectric properties and microstructure of nanocomposite Sb-GeO2 and Sb–TiO2 thin films

This work reports on fabrication and thermoelectric properties of Sb-GeO2 and Sb–TiO2 nanocomposite thin films. The formation of nanocomposite structure includes the precipitation of Sb phase and the amorphous GeO2 or TiO2 phase. In the Sb-GeO2 nanocomposite, the formation of large rhombohedral Sb grains is observed, where monoclinic Sb are formed as intermediate phase. This contributes remarkably to the elevation of conductivity, while results in the reduction of Seebeck coefficient and power factor. Contrary, the effective inhibition of Sb crystallization caused by TiO2 leads to the smaller monoclinic and rhombohedral Sb grains with homogeneous distribution in annealed Sb–TiO2 thin film. The existence of monoclinic Sb facilitates to acquire excellent thermoelectric properties. Tiny grains within the films introduce more grain boundaries, making it possible to scatter and filter low energy carriers. This leads to high conductivity, remarkable rise of the Seebeck coefficient, and excellent power factor of 765.5 μW/mK2 at 650 K. The results demonstrate that the Sb–TiO2 nanocomposite materials with high power factor can be a candidate for thermoelectric devices.

Enhancement of opto-electrical properties in Co doped CdS–TiO2 nanocomposite thin film as photoanode for Semiconductor Sensitized Solar Cells (SSSCs)

Cobalt doped CdS–TiO 2 nanocomposite thin films were coated on glass substrates by bottom up approaching methods. ZnS nanolayer over cobalt doped CdS–TiO 2 films act as a protective layer of CdS nanocrystal which enhances the photo stability. The structural, optical, electrical and surface morphological properties of ZnS-cobalt CdS–TiO 2 composite thin film were systematically evaluated. Structural analysis indicates that Co 2+ ions have been successfully incorporated in CdS site. The doping of cobalt in ZnS–CdS–TiO 2 film gives rise to an increase in the lattice parameter while the band gap decreased with increasing cobalt concentration. The bandgap of doped film decreases indicating the easy way of electron transfer from valence band to conduction band of CdS and TiO 2 . Surface morphological studies shows the diffusion of cobalt doped CdS nanoparticles into TiO 2 nanoporous structure of the composite film . The emission peaks in photoluminescence spectrum of ZnS-cobalt CdS–TiO 2 film proved the clear interaction of cobalt dopant with CdS nanocrystals. An enhancement in conductivity was observed due to incorporation of cobalt in CdS site and the resistance value (∼47%) was significantly decreased for cobalt doped CdS under illumination condition. Electrical analysis proved that the doped film is preferred as conductive electrode in solar cells than undoped film. • Cobalt doped CdS–TiO 2 composite thin films were synthesized by simple wet chemical method. • Interlocked CdS nanocrystals observed in SEM analysis, facilitate easy penetration into TiO 2 nanoporous structure of the composite film. • The doped film exhibit shifting of absorption edge towards longer wavelength (red shift), indicates decreased optical band gap. • The doped film shows superior electrical performance due to decreased resistance, preferred as conductive electrode in solar cells.

Deep understanding in physical and electrochemical performance of WO3–TiO2 nanocomposite thin films deposited onto ITO and FTO coated glass substrates using a thermionic vacuum arc deposition system

In this work, WO3–TiO2 nanocomposite thin films were deposited via thermonic vacuum arc technique and the physical and electrochemical features of these nanocomposites were investigated. The average transmittance values were obtained 66.9% and 58.7%, particularly the mean absorbance values were 0.49 and 0.59 onto ITO and FTOcoated glass substrate. The optical band gap of the layers were calculated 2.59 and 2.62 eV upon ITO and FTO coated glass substrates, respectively. Measurement outputs show that both coated thin films are conductive and good storage capabilities for Li+ ions. The reversibility of the films is calculated at 7% and 15% on ITO coated glass and FTO coated glass substrates, respectively. Considering that WO3 and TiO2 materials separately show high quality electrochromic properties, it is aimed to produce these two materials as composites and to examine their electrochromic properties using different producing techniques.

Influence of nanofiller concentration on polypropylene nanocomposites for high voltage cables

Abstract Polymeric insulation for HVDC cable is attracting more attention in the modern power transmission system. Especially, the thermoplastic material is desirable for power cable insulation because of its recyclability and ease of processing. Thermoplastic material development is a good alternative to cross-linked polyethylene in the future. Polypropylene has the advantage of avoiding by-products during cable production, which can minimize space accumulation and degassing costs. Therefore, this study investigates the influence of nanofillers on the structural properties of isotactic polypropylene. In addition, the proposed composite material’s morphology, melting, dielectric permittivity, and breakdown strength are examined. Different weight percentages of inorganic nanofillers such as TiO2 and ZnO are used to make nanocomposite thin films. With increasing filler concentration, the dielectric constant of the nanocomposite thin film increases. Apart from that, the dielectric loss of the TiO2 nanocomposite thin film increases with weight percentage initially and it falls nearer to virgin material at a higher frequency. The breakdown strength of the nanocomposite materials shows a similar variation with filler concentration. TiO2 is more resistant to deterioration than ZnO composite. Based on the results of the complete investigation, the TiO2 nanocomposite is better suited for the insulation of HVDC cables.

Substrate effect on electrochromic properties of Nb2O5:TiO2 nanocomposite thin films deposited by thermionic vacuum arc

In this paper, substrate effect on electrochromic properties of Nb2O5:TiO2 nanocomposite thin films have been investigated. Thin films have been deposited by thermionic vacuum arc deposition technology. Nb2O5 and TiO2 are known to be electrochromic materials. Nb/Ti rate was obtained 1.4. Average thicknesses of the films were found as 113 nm and 111 nm and band gap values for bleached states were calculated as 3.96 eV and 3.85 eV for the films deposited onto ITO and FTO coated glass substrates, respectively. The coloration efficiency values were calculated as 17 cm2/C and 26 cm2/C for the film onto ITO layered glass substrate and 31 cm2/C, 23 cm2/C and 24 cm2/C for the film onto FTO layered glass substrate at a different wavelength values in the visible region. The obtained results shows that films for each transparent conductive oxide material is promising material to obtain the high performance TiO2 active layer.

Spatially selective nanoplasmonic response in Ag embedded GLAD TiO2 nanocomposite thin films

The nanoplasmonic behaviour of Ag decorated TiO2 film structure was spatially varied across the sample surface by utilizing the tailored optical response of the underlying dielectric TiO2 thin film prepared using a novel collimated glancing angle deposition technique (collimated-GLAD). A blue shift in maximum attenuation coefficient region and minimum film transmittance region of the Ag/collimated-GLAD TiO2 nanocomposite coating with increase in height from the evaporation source was detected. The presence of minimum transmittance region was found to have occurred due to localized surface plasmon resonance (LSPR) phenomenon with additional contribution from thin film interference. The measured transmittance spectra showed spatial selectivity in LSPR wavelength of ∼22 nm with increase in height from the evaporation source. The variation of surrounding medium's (i.e. the TiO2 layer) refractive index (with height from the evaporation source) of the Ag nanostructures was the key factor responsible for the spatially varying nanoplasmonic response of Ag/collimated-GLAD TiO2 film across the sample surface. The Surface enhanced Raman scattering (SERS) characterization of the Ag/collimated-GLAD TiO2 film revealed photocatalysis driven dimerization conversion of p-aminothiophenol (p-ATP) molecules to p,p’-dimercaptoazobisbenzene (DMAB) due to the localized surface plasmons of the film structure along with the substantial enhancement in the Raman peak intensities compared to the blank substrate.

Optical characterizations of PMMA/metal oxide nanoparticles thin films: bandgap engineering using a novel derived model

We synthesize and optically characterize pure PMMA and PMMA incorporated with metal oxides nanoparticles (MO NPs) such as ZnO, CuO, TiO2 and SiO2 NPs nanocomposite thin films with weight concentration of 10% using dip-coating technique. SEM images of MO NPs show that all NPs have nearly an average size of around 50 nm. The optical parameters such as, optical parameters (n and k), optoelectronics properties, dispersion, band-gap energy and band structure of as-prepared nanocomposite thin films were determined by analyzing the transmittance and reflectance spectra. Mainly, optical band-gap energy (Eg) and the thickness of thin films are evaluated to a high degree of accuracy by utilizing Q-functional derived using a mathematical model recently published. The Q(E) is a functional containing experimental transmission and reflection data and the incident photon energy. The Eg value of un-doped PMMA thin films is found to be 4.273 eV. This value decreases as pre-selected MO NPs are introduced into thin films. These values are in excellent agreement with those determined using Tauc method. The FTIR technique is employed to elucidate the vibrational bands of the nanocomposites and the intermolecular bonding between PMMA matrix and the MOs NPs. Thermal stability is investigated by employing thermogravimetric analysis (TGA) at temperatures up to 400 °C. The obtained TGA thermograms indicate that adding MOs NPs to PMMA yield thin films of better thermal stability. The obtained doped thin films show a great promise for fabricating high-efficient optoelectronic devices.

Sun light driven photocatalytic performance of Ag decorated TiO2 nanocomposite thin films by sol gel method

High performance, low cost photocatalysts are essential for water treatment applications. However the existing majority of the photocatalysts limited to Ultra violet and visible region only. Besides the fabrication of photocatalysts, there is a huge demand for low cost, recyclable and solar light trapping photocatalysts, thereby effectively remove the organic pollutants present in water. Here, we have synthesized the solar light active Ag loaded TiO2 nanocomposite thin films by sol gel method. X ray diffraction, scanning electron microscopy and UV–visible spectroscopy were applied to characterizing the product. The results show that we successfully synthesized the silver doped titanium dioxide thin films. The silver doped titanium dioxide thin films show red shift and broad absorption band in the whole UV visible region in comparison with bare titanium dioxide. The results show that the Ag-TiO2 nanocomposite exhibit best photocatalytic efficiency under direct sun-light irradiation due to increased electron transfer and charge separation. The photodegradation activities of the Ag doped TiO2 were studied with model organic pollutants. Ag doped TiO2 sample showed 98% degradation efficiency in just 70 min under sun light irradiation. Repeated cycle runs revealed that these catalysts exhibit reusability and excellent stability, able to trap solar light efficiently and suitable for degradation of many organic pollutants. The performances of the Ag-TiO2 nanocomposites indicate that, these catalysts can find potential applications in photocatalytic water treatment plants.

Propose of high performance resistive type H2S and CO2 gas sensing response of reduced graphene oxide/titanium oxide (rGO/TiO2) hybrid sensors

Few studies have investigated the electrical and gas sensing properties of reduced graphene oxide/titanium dioxide (rGO/TiO2) composite thin films by spray pyrolysis technique. In this work, we report the synthesis and systematic investigation of structural, morphological and gas sensing properties of rGO-loaded TiO2 nanocomposite thin films. The XRD and AFM results suggest that both pure and rGO/TiO2 nanocomposite showed crystalline with tetragonal anatase phase and individual spherical shaped nanoparticles with average diameter of around 20–30 nm was observed. rGO/TiO2 nanocomposite showed high surface area (112 m2/g) and larger pores (11.2 nm) than bare TiO2 (89 m2/g; 32.3 nm). This huge surface area can beneficial for enhancing the gas sensing performance. Resistive type gas sensor set up was constructed and studied the sensing responses towards H2S and CO2 gases. The results suggest that the rGO/TiO2 nanocomposite sensor showed high sensitivity (92%), stability (only loss 3.5%), fast response (30 s) and recovery time (25 s) towards CO2 gas. The improved gas sensing mechanism of the proposed sensor was discussed in detail.

Effect of CdO ratios on the structural and optical properties of CdO–TiO2 nanocomposite thin films

Nanocomposite CdO–TiO2 thin films have been successfully synthesized via sol–gel and spin coating techniques. The physical properties of the prepared thin films were studied by varying the Cd:Ti ratio (0, 25, 50, 75, and 100%). The structural characterization has been performed by X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Optical transmission and reflectivity of the obtained films have been studied by UV–Vis-NIR spectroscopy. The obtained results showed that the amount of Cd into the TiO2 matrix can significantly affect the properties of TiO2 thin films; the XRD analysis revealed the appearance of new diffraction planes by increasing the of Cd:Ti ratios, a fact that was also confirmed by the Raman spectra. Effects of incorporated Cd amounts on the crystal phase, crystallite size, surface morphology were investigated. The results showed that most of Cd2+ substituted Ti4+ in the crystal lattice of TiO2 and led to the appearance of the CdTiO3 phase for thin films at a relatively low temperature, which inhibited the growth of crystallite size and suppressed the transformation from anatase to rutile of TiO2 at 450 °C. Moreover, formation of different binary and ternary nanocomposite films are justified by varying the Cd:Ti ratios. The optical analysis revealed a high transparency in the visible region, strongly affected by the different Cd:Ti ratios. Incorporated CdO initially increased the bandgap for low values of the Cd:Ti ratio, followed by a bandgap decrease for the highest one.

Thermal annealing induced cave in and formation of nanoscale pits in Ag–TiO2 plasmonic nanocomposite thin film

Ag–TiO2 nanocomposite thin films on silica glass were prepared through thermal evaporation in combination with RF magnetron sputtering. Thermal annealing induced changes in the optical, morphological and structural properties of Ag–TiO2 nanocomposites were examined using optical absorption, photoluminescence spectroscopy, Raman spectroscopy, FESEM, AFM and XRD. FESEM and AFM studies revealed cave in of the Ag–TiO2 thin film at various places leading to the formation nanoscale pits upon thermal annealing at 600 °C. The computed average size of pits was found to be 54 nm. Raman studies indicated 600 °C annealing induced transformation of anatase phase of TiO2 into anatase/rutile mixed phase TiO2. Optical absorption spectra showed systematic changes due to the effects of mixed phase formation and variation in the plasmonic behavior upon annealing. PL results of the as deposited Ag–TiO2 thin film showed peaks at 377, 402, 432 and 486 nm. PL studies of Ag–TiO2 nanocomposites treated at different annealing temperatures revealed changes in defect concentration in TiO2. The tentative mechanism for the creation of nanoscale pits in Ag–TiO2 thin film through thermal annealing was proposed.

High-energy 120 MeV Au9+ ion beam-induced modifications and evaluation of craters in surface morphology of SnO2 and TiO2 nanocomposite thin films

The electronic excitation and modification in the properties of the target material occur due to the kinetic energy loss of incident ions mainly through the inelastic collision with atomic electrons in the process of electronic energy stopping. Nanocomposite tin oxide (SnO2) and titanium dioxide (TiO2) thin film were grown on silicon and ITO substrates using RF magnetron-sputtering process. These thin films were irradiated by 120 MeV Au9+ Swift Heavy Ion (SHI) beam with varying fluence from 5 × 1011 ions cm−2 to 2 × 1013 ions cm−2 to induce modifications in thin films by dense electronic excitation. Surface morphology and depth profile of craters (approx. 85 nm) have been characterized by multimode atomic force microscopy (AFM). Grain mapping of AFM images provided the variation in grain size in the range of 72–279 nm and RMS roughness increased (4.01–23.6 nm) with increasing the ion fluence. Scanning Electron Microscopy (SEM) was also carried out to confirm the formation of craters in the irradiated film. X-ray diffraction (XRD) technique has been used for the structural analysis of virgin and irradiated thin films. XRD patterns established the formation of film in mixed (rutile and gamma) phase. Further, the crystallite size was evaluated using the Debye–Scherrer and Williamson–Hall method. It was found that crystallite size lie in the range of 36–54 nm which increased for the lower fluence and then decreased for higher fluence. The ion irradiation-induced strain has been explained by Thermal spike and Coulomb explosion model. UV–Vis study showed that the optical band gap reduced from 3.87 to 3.72 eV with increasing the ion fluence which can be ascribed to the formation of intermediate states and free radicals between the valance and band conduction band. Rutherford Backscattering Spectrometry (RBS) ensured that the film thickness decreased from 210 to 183 nm with increasing the ion fluence. The simulation of the RBS spectra provides the elemental composition of Sn (0.37), Ti (0.65) and O (0.85) in SnO2 and TiO2 nanocomposite thin films.

Modification in the properties of SnO2 and TiO2 nanocomposite thin films by low energy ion irradiation

The nanocomposite thin films of Tin oxide (SnO2) and Titanium dioxide(TiO2) were deposited on silicon and ITO substrate by RF magnetron sputtering technique using sintered pellet formed by mixing SnO2 and TiO2 in the mass percentage ratio of 25:75 respectively. These thin films were irradiated with low energy carbon negative ion (C−1) at varying fluence from 5e14 to 1e17 ions/cm2 to create modifications in the material properties. Crystallinity and phase transformation was studied by X-ray diffraction (XRD) technique. An increase in crystalline size was observed from 13.33 nm to 27.38 nm with an increase of ion fluence. Also the strain values were found to decrease from 1.485 to 0.507. Surface morphology was characterized by Atomic Force Microscopy (AFM) technique that confirmed the grain size dependence on ion fluence. The optical properties of thin films were investigated using UV/Visible Spectroscopy and decreasein band gap (3.91-2.55eV) was observed. The variation in optical band gap is due to the formation of defect states and phase transformation. Rutherford Backscattering Spectrometry (RBS) was used to confirm the change in elemental composition. A decrease in the width of the tin peak was observed with increase in the ion fluence that shows a decrease in thickness of thin films from 230 ± 2 nm to 220 ± 2 nm. The modification in the properties can be attributed to the formation of defects, vacancies and temperature spike generated in the samples due to irradiation.

Few-layers MoS2 sensitized Ag–TiO2 nanocomposite thin film for enhancing photocatalytic activity

The novel few-layers MoS2 sensitized Ag–TiO2 were prepared through hydrothermal method, photoreduction method and spin-coating method, respectively. The microstructure, surface morphology, chemical composition and ultraviolet–visible absorbance of the samples were investigated systematically. The results indicated that the Ag nanoparticles and few-layers MoS2 were deposited successfully on the surface of TiO2 NRAs. The visible photocatalytic activity was estimated by degradation of methylene blue solution. The results indicated that the photocatalytic properties of MoS2/Ag–TiO2 was larger than pure TiO2 NRAs and Ag–TiO2. The significantly increased photocatalytic properties was attributed to the stronger visible light capture capability and the enhanced electron–hole pairs separation.

WO<sub>3</sub>-TiO<sub>2</sub> Nanocomposite and its Applications: A Review

Design and development of nanostructure of titanium dioxide (TiO2) assemblies has gained significant scientific interest and become the most studied material as it exhibits promising functional properties. Nevertheless, formation of TiO2 nanocomposite thin film, especially WO3-loaded TiO2 nanotubes without bundling is essential for high efficiency in many potential applications, including photocatalytic oxidation related applications, solar cell related applications, electrochromic devices and sensing related applications. Thus, this chapter aims to summarize on the development of an efficient WO3-loaded TiO2 nanotubes catalyst for the improving the performance for charge carriers transportation and extended the spectral response of TiO2 to visible spectrum. In fact, coupling TiO2 with W6+ species will lead to an additional electronic state in the band-gap of nanocomposite thin film, which in turn affect a change in the electronic and functionality of TiO2 itself. As a result, band gap narrowing effects could expand the range of excitation light to the visible region and provide sites that slow down the recombination of charge carriers. To bring more TiO2 related applications to the point of commercial readiness and viability in terms of performance and cost, substantial research on the development of high efficient nanocomposite thin film (WO3-TiO2) is necessary. In this chapter, different synthesis strategies and research findings for WO3-TiO2 nanocomposite thin film as well as its prospects in potential applications will be reviewed in detail.

Preparation of PANI doped TiO2 nanocomposite thin film and its relevance as room temperature liquefied petroleum gas sensor

Present work reports the utility of PANI doped titanium dioxide thin film prepared by spin coating technique as LPG sensing. Optical properties were studied using UV–Vis absorption spectroscopy and FTIR spectroscopy. The surface morphology and structure of synthesized material were characterized by SEM and XRD analysis, respectively. The structural analysis confirmed the formation of TiO2–PANI having an average crystallite size 21 nm. Variations in the resistance with exposure of LPG to the sensing element were observed. Sensor response (S) as a function of time was calculated and its maximum value was found as 2.37 towards 2000 ppm of LPG, response time of the sensor was 2 min. The sensor was quite sensitive to LPG and results were found reproducible.

Effect of annealing on the structural, optical, electrical and photocatalytic activity of ZrO2–TiO2 nanocomposite thin films prepared by sol–gel dip coating technique

ZrO2–TiO2 nanocomposite thin films were deposited onto quartz substrate by sol–gel dip coating technique. The structural, morphological, optical, electrical and photocatalytic properties of the films were studied for different annealing temperatures (500, 800 and 1200 °C). X-ray diffraction pattern of films annealed at 500 °C showed amorphous nature. Increase in crystallinity was observed in the films annealed at higher temperature. Films annealed at higher temperature showed the formation of orthorhombic ZrTiO4 phase. Field emission scanning electron microscopy (FESEM) revealed crack free surface and surface roughness was found to increase with increase in annealing temperature. Energy dispersive X-ray analysis confirmed the presence of Zr, Ti and O in these films. Band gap of the films decreased from 3.93 to 3.50 eV with increase in annealing temperature. Photoluminescence spectra of the films exhibited emission peaks in both UV and visible region of the electromagnetic spectra. The conductivity of the films increased with increase in annealing temperature. Photocatalytic activity of these films evaluated by monitoring the degradation of methylene blue solution increased with increase in annealing temperature.

Synthesis of Ag –TiO2 Thin Films by Spin Coating process

In this research, Sol-gel technique prepared Ag–TiO2 nano-composite thin films, which were deposited onto a glass substrate by the spin coating process. The microstructures and chemical ingredients of the obtained thin films were characterized by UV-visible spectroscopy (UV), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). It was discovered that the silver nano-particles completely joined to the TiO2 matrix, where those nanoparticles distributed uniformly. In this way, the molar percent of the silver nitrate watery solution dominated the morphology of the thin film. Ag-TiO2 Nano composite is very useful for expanding antibacterial of nanomaterials purpose.

Structural, optical and electronic properties of Ag–TiO2 nanocomposite thin film

Nanocomposite thin films of Ag nanoparticles in TiO2 matrices were synthesised by RF magnetron co-sputtering and characterised by X-ray diffraction (XRD), Rutherford back scattering (RBS) spectrometry, UV–Vis, high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The composition of Ag was varied from 0 to 45 at.%. The thickness and the concentrations of Ag in the nanocomposite thin film were revealed by RBS. XRD analysis confirmed that the TiO2 matrix is in anatase phase and shows change in phase with Ag concentration. The UV–visible absorption spectroscopy revealed low-intense and broad surface plasmon resonance (SPR) peak at ~500 nm for the thin film with 33 at.% Ag content that was red-shifted to ~525 nm with increasing its intensity for 45 at.% of Ag. The red shift in SPR peak understood by Maxwell–Garnett theory and explained further nonexistence of SPR by interparticle separation from HR-TEM images and crystallinity. This HR-TEM image analysis confirmed the formation of Ag nanoparticles, and average radii were ~5, 12, 15 nm. The Tauc plot reveals reduction in band gap from 3.05 to 2.25 eV with increase in Ag content. Above results are understood based on the XPS analysis which shows a strong interaction between the Ag nanoparticle and TiO2. This decrease in band gap was advantageous to enhance the properties like photocatalytic and bioactivities through SPR.