Electrophoretic deposition of nanocomposites formed from polythiophene and metal oxides

An electrophoretic deposition (EPD) procedure was adopted for the cathodic preparation of thin films of conducting polymer/metal oxide nanocomposites with a core-shell structure. The deposition process was investigated at different potentials and in various solvents. The mechanism and kinetics of the electrophoretic deposition were studied via quartz crystal microbalance (QCM) and zeta-potential measurements.The properties of the composite layers were studied by electrochemical methods (cyclic voltammetry, impedance spectroscopy) and photocurrent measurements. The reversible redox potential of polythiophene films was about 0.75 V_SCE. The p-type semiconducting behaviour of the reduced polythiophene was studied by photocurrent measurements. In the case of using TiO₂ (n-type semiconductor) as a core material, an n/p heterojunction was observed. In the photocurrent spectra the maximum of the cathodic peak of polythiophene was found around λ = 500 nm (2.5 eV), depending on the applied potential. It is in agreement with the results of UV-vis optical spectra of deposited layers and of pressed pellets. The flatband potential of polythiophene in the heterojunction with TiO₂, obtained from photocurrent measurements, was 0.53 V_SCE.     

Microstructural and Optoelectronic Studies on Polyaniline: TiO2 Nanocomposites

Thin films of polyaniline (PANi) and PANi: titanium oxide (TiO₂) composites have been synthesized by sol–gel spin coating technique. The TiO₂ powder of particle size 50–60 nm was synthesized by the sol–gel technique and the polyaniline was synthesized by the chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and the four-probe method. The results were compared with corresponding data on pure polyaniline films. The intensity of diffraction peaks for PANi:TiO₂ composites is lower than that for TiO₂. The characteristic FTIR peaks of pure PANi are observed to shift to a higher wavenumber in PANi:TiO₂ composite, which is attributed to the interaction of TiO₂ particles with PANi molecular chains. The resistivity measurement shows that the molecular chain constitution of polyaniline is the most important carrier in the polyaniline: nano-TiO₂ composite.     

Characterization and photonic properties for the Pt-fullerene/TiO2 composites derived from titanium (IV) n-butoxide and C60

In this study, the structural variations, surface states, and mass transformations of fullerene [C₆₀] derivatives were investigated through the preparation of Pt-decorated oxidized fullerene and a Pt-fullerene/TiO₂ composite and comparison to an oxidized fullerene [C₆₀O]. These derivatives were synthesized with an improved oxidation method using m-chloroperbenzoic acid (MCPBA). Weak and strong peaks of metallic platinum and titanium dioxide, along with weak pristine fullerene [C₆₀] peaks, were observed in the XRD patterns for the Pt-fullerene and Pt-fullerene/TiO₂ composite. SEM micrographs for the metallic Pt-fullerene and Pt-fullerene/TiO₂ composite indicated that practically all the platinum and titanium dioxide that were introduced were located on the carbon cages and consequently, were dispersed into very small crystallites with growth of platinum metals and titanium dioxide. The EDX spectra of Pt-fullerene and Pt-fullerene/TiO₂ composite showed the presence of C, O, and Pt, with strong Ti peaks. From the MALDI-TOF mass spectra, the differences in the spectra for the three kinds of fullerene derivatives were due to oxidation including chemical bonding and interposing of metallic platinum and titanium dioxide in the fullerene [C₆₀] molecules. And, absorption property demonstrated by UV–vis diffuse reflectance method. From the photocatalytic results, the excellent activity of the Pt-fullerene/TiO₂ composites for organic dye and UV irradiation time could be attributed to the synergetic effects between photocatalysis of the supported TiO₂ and absorptivity of the platinum and fullerene.     

Influence of cathodic reduction on the photoelectrochemical behaviour of titanium dioxide under UV radiation measurement of the photocurrent in chloride medium

It is established that a cathodic pretreatment of thermic titanium dioxide increases considerably the photoresponse to TiO₂ under uv radiation in chloride solution. The effects of the duration of the pretreatment and of the nature of the acidic media used to perform the cathodic pretreatment are investigated. The variation law of the increase of the photocurrent with the pretreatment duration, which is the sum of two exponential laws at least, reveals the presence of various phenomena in the improvement of the energetic efficiency. The various mechanism involved there are discussed according to different hypotheses.     

Electrochemical synthesis and in situ spectroelectrochemistry of conducting polymer nanocomposites. I. polyaniline/TiO2, polyaniline/ZnO,and polyaniline/TiO2+ZnO

The polyaniline (PAn), polyaniline/titanium dioxide (PAn/TiO₂), polyaniline/zinc oxide (PAn/ZnO), and a novel conducting polymer nanocomposites, polyaniline/titanium dioxide + zinc oxide (PAn/TiO₂+ZnO), were synthesized by in situ electropolymerization and potential cycling on gold electrode. The PAn and nanocomposite films were characterized by cyclic voltammetry, Fourier transform infra‐red (FTIR) spectroscopy, in situ resistivity measurements, in situ UV–Visible, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The differences between cathodic and anodic peaks of three redox couples were obtained for PAn and polymeric nanocomposite films. During cathodic and anodic scans, the shift of potential was observed for polymer nanocomposite films. The characteristic FTIR peaks of PAn were found to shift to lower wavelengthsin polymer nanocomposite films. These observed effects have been attributed to interaction of TiO₂, ZnO, and TiO₂+ZnO particles with PAn molecular chains. Significant differences from in situ resistivity of PAn and nanocomposite films were obtained. The resistance of PAn/TiO₂, PAn/ZnO, and PAn/TiO₂+ZnO films were found to be smaller than the PAn film. The in situ UV–Visible spectra for Pan and polymer nanocomposite films were studied. The results show the intermediate spectroscopic properties between PAn and polymer nanocomposite films. The morphological analyses of PAn and nanocomposite films have been investigated. The nanocomposites SEM and TEM micrographs suggest that the inorganic semiconductor particles were incorporated in organic conducting polymer, which consequently modifies the morphology of the films significantly. POLYM. COMPOS., 35:351–363, 2014. © 2013 Society of Plastics Engineers     

Kinetics of Nano Titanium Dioxide Catalyzed Thermal Decomposition of Ammonium Nitrate and Ammonium Nitrate‐Based Composite Solid Propellant

This study deals with the influence of nanosized titanium dioxide (TiO₂) catalysts on the decomposition kinetics of ammonium nitrate (AN) and ammonium nitrate‐based composite solid propellant. TiO₂ nanocatalyst with an average particle size of 10 nm was synthesized by sol‐gel method using titanium alkoxide as precursor. Formation of nanostructured TiO₂ and presence of its anatase and brookite phases was confirmed by powder X‐ray diffraction (PXRD) and selected area diffraction (SAED) studies. Nano TiO₂ was further characterized by transmission electron microscopy (TEM), infrared (IR) spectroscopy, and thermogravimetry. The catalytic effect of TiO₂ nanocatalysts on the solid state thermal decomposition reaction of AN and nonaluminized HTPB/AN propellant was evaluated. To ascertain the effectiveness of the TiO₂ nanocatalyst, the thermal kinetic constants for the catalytic and non‐catalytic decomposition of AN and AN propellant samples were computed by using a nonlinear integral isoconversional method. Catalytic influence was evident from the lowering of activation energy for the catalyzed decomposition reactions. Apparently, the nanocatalysts provide Lewis acid and/or active metal sites, facilitating the removal of AN dissociation products NH₃ and HNO₃ and thereby enhance the rate of decomposition. The changes in the critical temperature of thermal explosion of AN and AN propellant samples due to the addition of TiO₂ nanocatalyst were also computed and the possible reasons for the changes are discussed.     

Characterization and relative photonic efficiencies of a new Fe-ACF/TiO2 composite photocatalysts designed for organic dye decomposition

The effect of Fe treatment on the Fe-activated carbon fiber (ACF)/TiO₂ composite catalysts was studied. Then the characterizations of Fe-ACF/TiO₂ composite catalysts were determined by employing BET, SEM, XRD and EDX instruments to analyze the potential factors. The adsorption data showed that the composites had decreased surface compared with the pristine ACF. From the results, it was shown the blocking of the micropores on the surface of ACF by treatment of Fe compound and Ti source. SEM micrographs for the Fe-ACF/TiO₂ composite catalysts indicated that practically all the ferric compounds and titanium dioxide introduced were located onto the ACF surfaces and consequently, there were dispersed into very small crystallites with growth of titanium dioxide. The XRD results showed patterns for the anatase and rutile typed titanium dioxide structure with a Fe mediated compound from the composites. The EDX results showed that the presence of C and O with Ti peaks on the Fe-ACF/TiO₂ composites decreased with an increase Fe concentration incorporated. Finally, organic dye (MB) decomposition showed the synergetic effects of adsorption, photo-degradation and enhancement of photonic activity of Fe component.     

Synthesis and characterization of polythiophene/titanium dioxide composites

Polythiophene/titanium dioxide (PT/TiO₂) composites were prepared by the in situ chemical oxidative polymerization method. The resulting PT/TiO₂ composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and field emission scanning electron microscopy (SEM). UV–Vis diffuse reflectance spectra measurements show that the PT/TiO₂ composites can adsorb light of wavelengths ranging from 200 nm to 800 nm. The PT/TiO₂ composites showed good adsorption properties and were more efficient in removing dye from solution than pure PT and pure TiO₂. The PT/TiO₂ composites exhibited photocatalytic activities to some extent under UV light illumination.     

Synthesis and Characterization of Polyaniline:TiO2 Nanocomposites

Thin films of polyaniline (PANi) and PANi:titanium oxide (TiO₂) composites have been synthesized by sol—gel spin coating technique. The TiO₂ powder of particle size 50–60 nm was synthesized by sol–gel technique and the polyaniline was synthesized by chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) Fourier transform infrared (FTIR) and UV-vis spectroscopy, and the results were compared with polyaniline films. The intensity of the diffraction peaks for PANi:TiO₂ composites is lower than that for TiO₂. The characteristic FTIR peaks of PANi were found to shift to a higher wave number in the PANi:TiO₂ composite. These observed effects have been attributed to the interaction of TiO₂ particles with PANi molecular chains. The room temperature resistivity of polyaniline:nano-TiO₂ composite is 3.43 × 10³ Ω cm and the resistivity of pure nano-TiO₂ particles is 1.60 × 10⁶ Ω cm.     

Fabrication of a TiO2/carbon nanowall heterojunction and its photocatalytic ability

A two-dimensional TiO₂/carbon nanowall composite material was fabricated by growing carbon nanowalls on a Ti sheet with hot filament chemical vapor deposition, followed by metal-organic chemical vapor deposition using titanium isopropoxide as TiO₂ precursor and argon as carrier gas. Scanning electron microscopy showed that TiO₂ was uniformly coated on the entire carbon nanowall and a TiO₂/carbon nanowall composite was obtained. Raman spectroscopy and X-ray diffraction indicated that the crystal phase of the TiO₂ coating was anatase. The asymmetry of the current-voltage plot for the material revealed that a heterojunction was formed between the TiO₂ and the carbon nanowall. As a result of this heterojunction, enhanced separation of photogenerated electrons and holes was confirmed by surface photovoltage and photocurrent measurements. The investigation of photocatalytic ability showed that the TiO₂/carbon nanowall had a higher photocatalytic activity than TiO₂ nanotubes for the degradation of phenol under UV light irradiation.     

Effects of nanosilica and titanium oxide on the performance of epoxy–amine nanocoatings

Different types of composite coatings were prepared by the blending of colloidal nanosilica (SiO₂) and titanium dioxide (TiO₂) in epoxy resin to investigate their coating performances. A fixed amount of silica nanoparticles (20 wt %) and different amounts (5, 10, and 15 wt %) of microsized TiO₂ particles were used in the coatings. The functional groups of the formulated coatings were confirmed by Fourier transform infrared spectroscopy. These results indicate that the SiO₂–TiO₂ particles interacted well with epoxy. Scanning electron microscopy images of the composite coatings revealed a good dispersion of TiO₂ particles at a lower amount of loading; this improved the adhesiveness, glass-transition temperature, thermal stability, and chemical resistance properties. At higher loadings, the performances decreased. The composite coatings were also characterized by their UV radiation-absorption properties with an ultraviolet–visible spectrophotometer. Interestingly, this property was found to be enhanced at higher loadings. An impressive result was noticed in the nanocomposites in terms of oxygen transmission rate performance compared to that of the neat epoxy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47901.     

Removal of gaseous toluene by using TiO<Subscript>2</Subscript> film doped of Ru-dye/Pt in a pilot scale photoreactor

The photodegradation efficiency (PE) of gaseous toluene was investigated by using titanium dioxide (TiO₂) film doped of ruthenium (Ru)-dye/platinum (Pt) in a 3,600 L pilot reactor. Ru-dye was applied as a sensitizer to enhance PE of toluene in both UV and visible wavelength range since its major peaks are 225 nm, 325 nm, 375 nm, and 525 nm. PE by using Pt/TiO₂ was more enhanced since Pt plays a role as an electron trapper in UV light range. The 3.2 μm thickness of TiO₂ film was optimized for the highest PE. The highest PE was 75%, 85%, and 90% by TiO₂, Pt/TiO₂, and Ru-dye/Pt/TiO₂ film, respectively.     

New effective process to fabricate fast switching and high contrast electrochromic device based on viologen and Prussian blue/antimony tin oxide nano-composites with dark colored state

We developed a new electrochromic device by using compact Prussian blue (PB)/antimony tin oxide (ATO) nano-composites as anodic electrode and viologen anchoring on titanium dioxide (TiO₂) nano-particles as cathodic electrode. The anodic electrode was based on a transparent nanostructured ATO nano-particle film and was electro-deposited by Prussian blue to form compact Prussian blue/ATO nano-composites by means of galvanostatic electrodeposition process. Nanocrystalline TiO₂ thin films on conducting glass were modified with a mono-layer of viologen with two anchoring groups, which were much strongly adsorbed onto the surface of TiO₂ nano-particles. A polymer gel electrolyte sandwiched between the anodic and cathodic layers is used as the ionic transport layer. The 2.5 cm × 2.5 cm electrochromic device shows high contrast (64.8%, at 600 nm) very low transmittance at colored stage (0.1%, at 600 nm), fast switching time (600 and 720 ms for coloration and bleaching, respectively), high coloration efficiency of 912 cm² C⁻¹ at 600 nm and good stability. The enhanced performance of the electrochromic device can be attributed to the ATO nano-particles as inter-conductive materials.     

Electrochemical study of TiO2 modified with silver nanoparticles upon CO2 reduction

A systematic cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) study on titanium dioxide (TiO₂) and silver–TiO₂ surfaces was performed in order to decouple electrochemical reduction processes of carbon dioxide in aqueous solutions. CV studies indicate cathodic current increase on Ag–TiO₂ compared to bare TiO₂ surfaces. An equivalent circuit based on transmission line model was applied in order to adjust EIS data, and a modification of this model was made to account for Ag particle interaction with the electrolyte solution. Electrochemical processes were then decoupled upon applied potential where the role of TiO₂ surface states was identified and separated from (a) silver reduction, (b) electronic transport on TiO₂, and (c) charge transfer on TiO₂ and Ag surfaces. The Ag–electrolyte interface impedance has considerably lower values than the TiO₂–electrolyte interface, suggesting that the silver particles may be considered as favorable reaction sites for the electrochemical reduction of water and carbon dioxide.     

Morphological,structural and ellipsometric investigations of Cr doped TiO2 thin films prepared by sol–gel and spin coating

Pure and chromium doped titanium dioxide (TiO₂) thin films at different atomic percentages (0.5%, 1.3% and 2.9%) have been elaborated on ITO/Glass substrates by sol–gel and spin–coating methods using titanium (IV) isopropoxide as a precursor. The surface morphology of films was investigated by scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM), the structure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission microscopy (HRTEM). SEM and HRTEM show homogenous and polycrystalline films. XRD patterns indicate a phase transition from anatase to anatase-rutile leading to expand the absorption band of TiO₂ molecules around 520 cm⁻¹ in FTIR spectra. The optical constants such as the refractive index (n), the extinction coefficient (K) and the band gap (E_g) as well as the film thickness are determined using spectroscopic ellipsometry technique and Fourouhi–Blommer dispersion model. Results show three major changes; (i) the thickness of pure TiO₂ layer is 54 nm, which linearly decreases when the layer is doped with chromium and reaches 33 nm for a doping concentration of 2.9%, (ii) the band gap energy (E_g) is also linearly reduced from 3.24 eV to 2.80 eV when the Cr-doping agent increases, and, (iii) a phase transition from anatase to anatase-rutile is observed causing an increase in values of n(λ) for wavelength greater than 350 nm.     

Multifunctional ZnO/TiO2 nanoarray composite coating with antibacterial activity,cytocompatibility and piezoelectricity

Metal oxides with nanostructures such as zinc oxide (ZnO), titanium dioxide (TiO₂) have been used in biomedical fields for their multifunctional properties. In this study, ZnO/TiO₂ nanoarray (nZnO/TiO₂) coatings were prepared via hydrothermal synthesis followed by low temperature liquid phase method. The particle size of the composites were no more than 100 nm in diameter, assembled into nanoarray on the Ti substrate. In vitro antibacterial experiments showed that the maximum bacteriostatic rate could reach 99% against Staphylococcus aureus and 90% against Escherichia coli, respectively. Moreover, the nZnO/TiO₂ coatings were of cytocompatibility and biocompatibility, promoting the proliferation of MC3T3-E1 and the expression of alkaline phosphatase (ALP). The piezoelectric properties of nZnO/TiO₂ coatings were preliminarily investigated. The smaller the size of the composite particle was, the better the antibacterial property, biocompatibility and piezoelectric properties were. Under the stimulation of the periodic loading, the growth of MC3T3-E1 was promoted, so the secretion of ALP was. The nZnO/TiO₂ composite coating with antibacterial activity, osteogenesis and intellectual stimulation would be a promising smart coating for orthopedic implants.     

Effect of oxidisable substrates on the photoelectrocatalytic properties of thermally grown and particulate TiO<Subscript>2</Subscript> layers

The photoelectrochemical properties of titanium dioxide layers, prepared by thermal oxidation of titanium at 500–750 °C, were compared with those of layers of particulate (Degussa) P25, especially for oxidation of oxalic acid. The thermally formed oxide layers had rutile structures with a particle size of about 100 nm. Values of incident photon-to-current conversion efficiencies increased with rutile layer thickness and reached a maximum at about 1 μm. Photocurrents for particulate TiO₂ layers were about one order lower than those for thermal layers, due to the poor contact among individual particles, resulting in high electric resistance of the whole layer. The presence of oxalic acid had no effect on the photocurrent of thermal TiO₂ layers, while in the case of porous particulate layers, the photocurrent increased strongly, due to oxalate adsorption and subsequent enhanced oxidation rate with photogenerated holes. For oxalic acid concentrations ≤10⁻³ M, the photocurrent decayed due to mass transfer limitations, resulting in oxalate depletion in the porous particulate layer.     

Photoelectrochemical oxidation of salicylic acid and salicylaldehyde on titanium dioxide nanotube arrays

We report on the kinetics of photoelectrochemical oxidation of salicylic acid (SA) and salicylaldehyde (SH) on titanium dioxide nanotube arrays. The TiO₂ nanotubes were prepared by the electrochemical oxidation of titanium substrates in a nonaqueous electrolyte (DMSO/HF). Scanning electron microscopy (SEM) was employed to examine the morphology of the formed nanotubes. Linear voltammetry was used to study the electrochemical and photoelectrochemical behavior of the synthesized TiO₂ nanotube arrays. The photoelectrochemical oxidation of SA and SH on the TiO₂ nanotubes was monitored by in situ UV-vis spectroscopy, showing that the kinetics of the photoelectrochemical oxidation of SA and SH follows pseudo first-order and that the rate constant of SH oxidation is 1.5 times larger than that of SA degradation. Quantum chemical calculations based on the DFT method were performed on SA and SH to address the large difference in kinetics. The relatively higher E_LUMO − E_HOMO makes SA more stable and thus more difficult to be oxidized photoelectrochemically. The impact of temperature and initial concentrations on the kinetics of SA and SH photoelectrochemical degradation was also investigated in the present work.     

A novel synthesis route of titanium dioxide with (NH4)0.3TiO1.1F2.1 as by-product

This work explores a new route for the synthesis of titanium dioxide using scraps and titanium chips, which are typically discarded as waste, as the precursor materials. The band-gap energy of the synthesised materials was determined using diffuse reflectance spectroscopy. The morphology, elemental analysis, crystallinity, and chemical structure of the synthesised materials were determined by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, and infrared and Raman spectroscopies, respectively. The X-ray and Raman analyses confirmed the formation of titanium dioxide in its tetragonal (anatase) crystalline form after heat treatment (400 °C, 2 h). Moreover, a mixture of (NH₄)_0,3TiO_1,1F_2,1 and anatase TiO₂ was obtained as a by-product. After heat treatment, this by-product was converted into fluorine-doped titanium dioxide, also in anatase crystalline form. The apparent crystallite size (L_c) of anhydrous titanium dioxide was found to be smaller than that of the calcined by-product. The diffuse reflectance spectroscopy analysis revealed that the calcined by-product has a significantly higher absorption capacity at higher wavelengths, as well as a lower band-gap energy value. The scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) analyses showed large particulates on which smaller particles are deposited and good dispersion of the elemental components. The anhydrous titanium dioxide sample presents a smaller particle size than the calcined by-product.     

Low-temperature fabrication of TiO<Subscript>2</Subscript> film on flexible substrate by atmospheric roll-to-roll CVD

Titanium dioxide (TiO₂) thin film was fabricated using titanium isopropoxide as a precursor through an atmospheric low-temperature roll-to-roll chemical vapor deposition method. TiO₂ was deposited on the PET substrate in the temperature range of room temperature to 100°C, and the working pressure was 740 Torr. The surface morphology of TiO₂ thin film was analyzed by field emission scanning electron microscopy and a 2D surface profiler. The results revealed that the growth rate of TiO₂ film was 31 nm/min at 100°C, and it also showed that the surface is uniform and smooth. Moreover, the lowest root mean square roughness (R _q) value of 1.87 nm was obtained for TiO₂ film prepared at 100°C. The composition of TiO₂ film was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The film showed very good chemical and optical properties while increasing the substrate deposition temperature. The UV–Vis spectroscopy analysis revealed that TiO₂ films exhibited excellent optical transmittance, more than 91% observed in the visible region.