An efficient visible light photocatalyst prepared from TiO<Subscript>2</Subscript> and polyvinyl chloride

An efficient visible light photocatalyst has been prepared from TiO₂ nanoparticles and a partly conjugated polymer derived from polyvinyl chloride (PVC). It was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The visible light photocatalytic activity of the as-prepared photocatalyst was evaluated by the photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The XPS, FT-IR, and Raman spectra show that the partly conjugated polymer derived from PVC exists on the surface of the TiO₂ nanoparticles. The UV–Vis DRS, XRD, and TEM results reveal that the modification of the partly conjugated polymer can obviously improve the absorbance of the TiO₂ nanoparticles in the range of visible light and hardly affect their size and crystallinity. The visible light photocatalytic activity of the as-prepared TiO₂ nanocomposites is higher than that of commercial TiO₂ (Degussa P25) and comparable with those of visible light photocatalysts reported in the literature. Their visible light photocatalytic stability is also good. The reasons for their excellent visible light photocatalytic activity and the major factors affecting their photocatalytic activity are discussed.     

Characterization and photoactivity of TiO2 sols prepared with triethylamine

Using triethylamine as a surface protective agent, a transparent and pale yellowish TiO₂ sol had been prepared at 90 °C. This method was very different from the traditional methods, which produced titanium dioxide nanoparticles with anatase crystalline structure either at high acid condition or high temperature. X-ray diffraction (XRD) and transmission electron spectroscopy (TEM) demonstrated that the as-prepared TiO₂ sol nanoparticles with anatase crystalline structure were uniformly distributed, and the average size was 3 nm. X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra showed that triethylamine was adsorbed on TiO₂ sol particles surface. FTIR spectroscopy noted that TiO₂ sol particles had the similar spectra with Degussa P25. Photoactivity of the as-prepared TiO₂ sol was studied by investigating the photodegradation of methyl violet in hydrosol reaction system under visible light irradiation.     

Low temperature facile synthesis of anatase TiO2 coated multiwalled carbon nanotube nanocomposites

Anatase TiO₂ coated multiwalled carbon nanotube (MWNT) nanocomposites were prepared by combining the sol-gel method with a self assembly technique at a low temperature. XRD, TEM, FTIR and XPS spectra were applied to characterize the crystal phase, microstructure, and other physicochemical properties of the sample. The results showed that MWNTs were covered with a 12-20 nm thickness layer of anatase TiO₂ or surrounded by a 30 -290 nm thickness coating of anatase TiO₂. The layer or coating is constructed of TiO₂ nanoparticles about 5.8 nm. Furthermore, as-prepared composite was rich in surface hydroxyl groups.     

Photocatalytic activity of polypyrrole/TiO<Subscript>2</Subscript> nanocomposites under visible and UV light

A series of polypyrrole (PPy)/titanium dioxide (TiO₂) nanocomposites were prepared in different polymerization conditions by ‘in situ’ chemical oxidative polymerization. The nanocomposites were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectra (XPS), and UV–Vis diffuse reflectance spectra. The photocatalytic degradation of methyl orange (MO) was chosen as a model reaction to evaluate the photocatalytic activities of TiO₂/PPy catalysts. The results show that a strong interaction exists at the interface between TiO₂ and PPy, the deposition of PPy on TiO₂ nanoparticles can alleviate their agglomeration, PPy/TiO₂ nanocomposites show stronger absorbance than neat TiO₂ under the whole range of visible light. The obtained PPy/TiO₂ nanocomposites exhibit significantly higher photocatalytic activity than the neat TiO₂ on the degradation of MO aqueous solution under visible and UV light illumination. The reasons for improving the photocatalytic activity were also discussed.     

Structural characterisation and antibacterial activity of PP/TiO2 nanocomposites prepared by an in situ sol–gel method

Polypropylene/titanium dioxide (PP/TiO₂) nanocomposites can be prepared using a novel method based on the hydrolysis–condensation reactions (sol–gel method) of titanium alkoxide inorganic precursors that have been premixed with polypropylene under molten conditions. The resultant nanocomposites were characterised by transmission electronic microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These techniques showed the formation of the titanium oxi-hydroxide chemical structure (Ti_xO_y(OH)_z) with a diameter of approximately 10 nm in the polymer matrix. Furthermore, a condensation degree of around 17% was determined using XPS analysis. The antibacterial activity was tested according to the JIS Z 2801:2000 standard with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in the absence of light. Correlations between the microstructure and the chemical composition of PP/TiO₂ nanocomposites and the antibacterial properties of these nanocomposites were discussed. The structure of titanium oxi-hydroxide derivative particles (Ti_xO_y(OH)_z) within the polypropylene matrix has been shown to impact strongly on the antibacterial properties in comparison with the results obtained with a dispersion of anatase titanium dioxide into the PP.     

The microwave effect on the properties of silica-coated TiO2 fine particles prepared using sol-gel method

The silica coating of TiO₂ fine particle was conducted using microwave assisted sol-gel method and conventional sol-gel method to suppress its photo-catalytic activity. The amount and uniformity of silica coating on TiO₂ surface were characterized by X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF), infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and zeta potential measurements. XPS and XRF results showed that the presence of catalyst and reaction time were important factors to reach high silica amounts. SEM, TEM, and zeta potential results indicated that dense film coating of SiO₂ layer formed on TiO₂ surface in conventional sol-gel method, whereas the nucleation coating was observed on sample prepared by microwave assisted sol-gel method. When photo-catalytic activities and ultraviolet (UV) shielding abilities of these samples were evaluated, the sample prepared by microwave processing showed higher inhibition of photo-catalytic activity and better UV shielding ability than the sample prepared by conventional method. These results suggested that the coating method significantly affected the photo-catalytic activity and UV shielding ability of coated TiO₂.     

Decoration of carbon nanotubes with nearly monodisperse MFe2O4 (MFe2O4, M = Fe, Co, Ni) nanoparticles

Magnetic monodisperse ferrite MFe₂O₄ (M = Fe, Co, Ni) nanoparticles have been successfully deposited on carbon nanotubes (CNTs) by in situ high-temperature hydrolysis and inorganic polymerization of metal salts and CNTs in polyol solution. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometry (EDS) and vibrating sample magnetometer (VSM) investigations were used to characterize the final products. The influencing factors for formation of CoFe₂O₄ nanoparticles along CNTs have also been discussed briefly. The main advantage of this synthetic strategy is that it is beneficial for the fabrication of magnetic CNTs with a compact layer of nanoparticles and could be extended to prepare series of ferrite/CNTs nanocomposites via the substitution of metal cations.     

Quantum dot sensitized solar cell based on poly (3-hexyl thiophene)/CdSe nanocomposites

The optoelectronic properties of P3HT–CdSe nanocomposites prepared by insitu chemical oxidative polymerization were studied. CdSe QDs were synthesized by hot injection method using tri octyl phosphine oxide (TOPO) as capping ligand whereas the P3HT polymer was prepared by chemical oxidative polymerization. FTIR studies confirmed the regioregularity of the P3HT and revealed the chemical interaction of P3HT and CdSe in nanocomposite. Absorption studies showed blue shift for the nanocomposites as compare to pristine P3HT, the electron transfer from conducting polymer to the CdSe was detected by the measurements of quenching of photoluminescence from conducting polymer after the addition of semiconductor nano crystals which confirmed that an optimum amount of nanoparticles provide networking in hybrid composites. The optimal result for device prepared by P3HT–CdSe nanocomposites was open circuit voltage (V_oc) 0.5, short circuit current density (J_sc) 0.66, Fill factor (FF) 0.6855 and efficiency (η) 0.22%.     

The fabrication of the antibacterial paste based on TiO2 nanotubes and Ag nanoparticles-loaded TiO2 nanotubes powders

ABSTRACT

We successfully synthesised TiO₂ nanotubes (TNTs) and silver nanoparticles (Ag NPs)-loaded TiO₂ nanotubes paste. These were coated on a glass substrate by spin coating method, and their antibacterial activities were surveyed. The morphology of materials was defined by transmission electron microscopy (TEM) image; the crystalline structure and the composition of the materials were determined by X-ray diffraction (XRD) pattern and X-ray photoelectron spectroscopy (XPS). Vibrational properties of the molecules existing in the sample were investigated by Fourier transform infrared (FTIR) spectroscopy, and the transmittances of films were determined by UV–Vis transmittance spectroscopy. This research shows that the structure and morphology of TNTs did not change after they underwent the processes of paste preparing and film coating on a glass substrate. Furthermore, the transmittance of TNTs film (about 75%) is higher than Ag NPs-loaded TiO₂ nanotubes (Ag/TNTs) film (about 65%) in the visible region. Moreover, the antibacterial property of Ag/TNTs film shows its effectiveness against Escherichia coli bacteria, and the antibacterial efficiency is 99.06% for 24 h-incubation period in the dark condition.     

Ar assisted carbidization of TiO2 (1 1 0) supported Mo nanoparticles by decomposition of C2H4

Ar⁺ assisted carbidization of Mo nanoparticles supported on TiO₂ (1 1 0) is studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In order to activate the diffusion of carbon into the bulk of Mo nanoparticles we applied Ar ions (1 keV) during the exposure of C₂H₄. XPS exhibited that the decomposition of C₂H₄ at 850 K accompanied by ion bombardment results in an almost complete carbidization of nanocrystalline Mo while this treatment performed without ion bombardment results only in the carbidization of the particle surface. The modification of the crystallinity of the Mo-carbide particles was deduced from STM measurements.     

Improvement of epoxy resin properties by incorporation of TiO2 nanoparticles surface modified with gallic acid esters

Epoxy resin/titanium dioxide (epoxy/TiO₂) nanocomposites were obtained by incorporation of TiO₂ nanoparticles surface modified with gallic acid esters in epoxy resin. TiO₂ nanoparticles were obtained by acid catalyzed hydrolysis of titanium isopropoxide and their structural characterization was performed by X-ray diffraction and transmission electron microscopy. Three gallic acid esters, having different hydrophobic part, were used for surface modification of the synthesized TiO₂ nanoparticles: propyl, hexyl and lauryl gallate. The gallate chemisorption onto surface of TiO₂ nanoparticles was confirmed by Fourier transform infrared and ultraviolet–visible spectroscopy, while the amount of surface-bonded gallates was determined using thermogravimetric analysis. The influence of the surface modified TiO₂ nanoparticles, as well as the length of hydrophobic part of the gallate used for surface modification of TiO₂ nanoparticles, on glass transition temperature, barrier, dielectric and anticorrosive properties of epoxy resin was investigated by differential scanning calorimetry, water vapor transmission test, dielectric spectroscopy, electrochemical impedance spectroscopy and polarization measurements. Incorporation of surface modified TiO₂ nanoparticles in epoxy resin caused increase of glass transition temperature and decrease of the water vapor permeability of epoxy resin. The water vapor transmission rate of epoxy/TiO₂ nanocomposites was reduced with increasing hydrophobic part chain length of gallate ligand. Dielectric constant of examined nanocomposites was influenced by gallate used for the modification of TiO₂ nanoparticles. The nanocomposites have better anticorrosive properties than pure epoxy resin, because the surface modified TiO₂ nanoparticles react as oxygen scavengers, which inhibit steel corrosion by cathodic mechanism.     

Photochemical synthesis and characterization of Ag/TiO2 nanotube composites

TiO₂ nanotubes were fabricated by a hydrothermal method. Silver nanoparticles with diameters around 3–5 nm were loaded onto the surface of TiO₂ nanotubes via a deposition approach followed by a photochemical reduction process under ultraviolet irradiation. Transmission electron microscopy (TEM), N₂ adsorption measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis), and fluorescence spectroscopy (FL) were applied to characterize the as-prepared Ag/TiO₂ nanotube composites. The photocatalytic activity of the as-prepared materials was investigated by photodegrading of methyl orange. The results showed that silver particles were in zero oxidation state and highly dispersed on the surface of TiO₂ nanotubes when the concentration of Ag⁺ was low. The presence of metallic silver can help the electron-hole separation by attracting photoelectrons. The Ag/TiO₂ nanotube composites with a suitable amount of silver showed a further improvement on the photocatalytic activity for degradation of methyl orange in water.     

Preparation N-F-codoped TiO2 nanorod array by liquid phase deposition as visible light photocatalyst

An efficient method for the preparation of N-F-codoped visible light active TiO₂ nanorod arrays is reported. In the process, simultaneous nitrogen and fluorine doped TiO₂ nanorod arrays on the glass substrates were achieved by liquid phase deposition method using ZnO nanorod arrays as templates with different calcination temperature. The as-prepared samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra measurements. It was found that calcination temperature is an important factor influencing the microstructure and the amount of N and F in TiO₂ nanorod arrays samples. The visible light photocatalytic properties were investigated using methylene blue (MB) dye as a model system. The results showed that N-F-codoped TiO₂ nanorod arrays sample calcined at 450 °C demonstrated the best visible light activity in all samples, much higher than that of TiO₂ nanoparticles and P25 particles films.     

Synthesis and characterization of CdS doped TiO2 nanocrystalline powder: A spectroscopic study

This report aimed to study the effect of CdS doping in TiO₂ on the phase transformation of TiO₂ from anatase to rutile using X-ray diffraction (XRD) and Raman spectroscopy. CdS-doped TiO₂ nanocomposites have been prepared and characterized using Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). We have observed that contrary to bare TiO₂, phase transformation of TiO₂ from anatase to rutile is hindered when doped with CdS at high temperature. Raman spectroscopy is found to be more sensitive for detection of the surface of TiO₂ as compared to XRD.     

Synthesis of WO3 in nanoscale with the usage of sucrose ester microemulsion and CTAB micelle solution

WO₃ nanoparticles were successfully prepared using first the low temperature hydrolysis method and second the chemical reaction method in water-in-oil sucrose ester microemulsion consisting of S1570, 1-butanol, tetradecane and aqueous phase. In this study WO₃ nanoparticles also were prepared using the CTAB micelle solution. The resultant WO₃ nanoparticles have been investigated with X-ray diffraction (XRD), transmission electron microscopy (TEM), variable pressure scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). The shape and particles size of the resultant WO₃ nanoparticles from both methods in sucrose ester microemulsion show similar spherical shape and size range between 10 and 50 nm. The WO₃ nanoparticles prepared with the CTAB micelle solution show spherical shape with the size range average of 25-50 nm.     

Enhancement of photoelectrochemical performance of CdSe sensitized seeded TiO<Subscript>2</Subscript> films

In this work, we highlight the effect of TiO₂ seed layer (SL) on the photoelectrochemical performances of CdSe/TiO₂ photoanodes (PAs). TiO₂ thin films were prepared by spin coating starting from a sol gel solution containing TiO₂ nanopowder, then sensitized with electrodeposited CdSe nanoparticles. Structural, optical and photoelectrochemical properties of the CdSe/TiO₂ PAs with and without the SL were investigated. Charge accumulation processes and charge transfer characteristics were identified by electrochemical impedance spectroscopy. The introduction of the compact TiO₂ SL was found to significantly increase the electron transport. The photocurrent density produced by the CdSe/TiO₂/SL PA reached 0.95 mA/cm², about two times higher than that performed by the CdSe/TiO₂ PAs. This enhancement might be attributed to a substantial decrease of the leakage current induced by a better crystallization of TiO₂ thin films as well as a higher sensitizing effect of the CdSe nanoparticles.     

Synthesis and photocatalytic properties of TiO2 nanostructures

TiO₂ particles, rods, flowers and sheets were prepared by hydrothermal method via adjusting the temperature, the pressure and the concentration of TiCl₄. The as-prepared TiO₂ powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra and N₂ adsorption–desorption measurements. It was found that pressure is the most important factor influencing the morphology of TiO₂. The photocatalytic activity of the products was evaluated by the photodegradation of aqueous brilliant red X-3B solution under UV light. Among the as-prepared nanostructures, the flower-like TiO₂ exhibited the highest photocatalytic activity.     

Pd nanoparticle loaded TiO<Subscript>2</Subscript> semiconductor for photocatalytic degradation of Paraoxon pesticide under visible-light irradiation

Overuse of the organophosphorus pesticides such as Paraoxon in agriculture industry has raised significant threats to the environment by contamination of soils and groundwaters. Therefore, extensive studies have been carried out to develop an effective method for removing of these poisonous pollutants from contaminated resources. In the current study, Pd nanoparticle loaded TiO₂ nanocomposites with different weight percentages of Pd were prepared via a facile photoreduction method and for the first time, were used for photocatalytic degradation of Paraoxon under visible-light irradiation. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy techniques. In these nanocomposites, the presence of Pd nanoparticles enhances the photocatalytic activity of TiO₂ by their surface plasmon resonance effect and also by narrowing the band gap energy of TiO₂. The results of photocatalytic activity measurements indicate that the nanocomposite with 0.8 wt% content of Pd (PT0.8) has the best photocatalytic activity. The result of total organic carbon test shows that Paraoxon was completely mineralized by PT0.8 photocatalyst after 120 min, under visible-light irradiation.     

Green synthesis of zinc oxide nanoparticles using tomato (Lycopersicon esculentum) extract and its photovoltaic application

With an increasing awareness of green and clean energy, zinc oxide-based solar cells were found to be suitable candidates for cost-effective and environmentally friendly energy conversion devices. In this paper, we have reported the green synthesis of zinc oxide nanoparticles (ZnONPs) by thermal method and under microwave irradiation using the aqueous extract of tomatoes as non-toxic and ecofriendly reducing material. The synthesised ZnONPs were characterised by UV–visible spectroscopy (UV–vis), infra-red spectroscopy, particle size analyser, scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction study (XRD). A series of ZnO nanocomposites with titanium dioxide nanoparticles (TiO₂) and graphene oxide (GO) were prepared for photovoltaic application. Structural and morphological studies of these nanocomposites were carried out using UV–vis, SEM, XRD and AFM. The current–voltage measurements of the nanocomposites demonstrated enhanced power conversion efficiency of 6.18% in case of ZnO/GO/ TiO₂ nanocomposite.     

Preparation and characterization of N–I co-doped nanocrystal anatase TiO2 with enhanced photocatalytic activity under visible-light irradiation

N–I co-doped TiO₂ nanoparticles were prepared by hydrolysis method, using ammonia and iodic acid as the doping sources and Ti(OBu)₄ as the titanium source. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible diffuse reflection spectroscopy (UV–vis DRS). XRD spectra show that N–I–TiO₂ samples calcined at 673 K for 3 h are of anatase structure. XPS analysis of N–I–TiO₂samples indicates that some N atoms replace O atoms in TiO₂ lattice, and I exist in I⁷⁺, I⁻ and I⁵⁺ chemical states in the samples. UV–vis DRS results reveal that N–I–TiO₂ had significant optical absorption in the region of 400–600 nm. The photocatalytic activity of catalysts was evaluated by monitoring the photocatalytic degradation of methyl orange (MO). Compared with P25 and mono-doped TiO₂, N–I–TiO₂ powder shows higher photocatalytic activity under both visible-light (λ > 420 nm) and UV–vis light irradiation. Furthermore, N–I–TiO₂ also displays higher COD removal rate under UV–vis light irradiation.