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Nanosized zinc stannate Zn₂SnO₄ (ZTO) was synthesized via a simple hydrothermal method using sodium hydroxide NaOH as a mineralizer. Hydrothermally treated at 150, 200, and 250°C for 24 h and 48 h, the X-ray diffraction (XRD) pattern showed that highly crystalline ZTO nanostructures could be formed at 200 and 250°C. Transmission electron microscopy (TEM) images showed that ZTO nanocubes were formed at 250°C, and a sheet-like structure was found at 200°C. Raman spectra revealed that ZTO had a spinel structure and there were two Raman shift peaks at approximately 668 and 535 cm^-1, which were similar to the peaks of ZTO nanowires. Furthermore, the photocatalytic activity of the ZTO samples was assessed utilizing methylene blue (MB) under ultraviolet irradiation, and the UV-Visible light absorption spectra was investigated to interpret the relationship between photocatalytic properties and light absorptivity. The sheet-like ZTO nanostructures exhibited better photocatalytic activity due to their excellent light absorption properties.

In this paper, the electronic structures and optical properties of N-doped, S-doped and N/S-codoped InNbO₄ were systematically investigated by first-principles calculations based on density functional theory (DFT). As for N-doped InNbO₄, the acceptor N-$2p$ states would introduce on the upper edge of the valence band (O-$2p$). While S-$3p$ states would mix with O-$2p$ states when O atom was replaced by S atom in InNbO₄. As for N/S-codoped InNbO₄, N-$2p$ states mixed with S-$3p$ states above the valence band, resulting in the energy bandgap further narrower in contrast to those of the individual N(S)-doped InNbO₄. The optical absorption edge of N/S-codoped InNbO₄ displayed an obvious redshift and was successfully extended to visible light region due to the synergistic effect of N/S co-doping. This research proposed that N/S co-doping was a promising method to improve the photocatalytic properties of InNbO₄.

A liquid fuel high velocity oxy-fuel (HVOF) thermal spray process has been used to deposit TiO₂ photocatalytic coatings utilizing a commercially available anatase/rutile nano-powder as the feedstock. The coatings were characterized in terms of the phases present, its crystallite size and coating morphology by means of X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy, respectively. The results indicate that the sprayed TiO₂ coatings were composed of both TiO₂ phases, namely anatase and rutile with different phase content and crystallite size. A high anatase content of 80% by volume was achieved at 0.00015 fuel to oxygen ratio with nanostructure coating by grain size smaller than feedstock powder.

It is found that fuel to oxygen ratio strongly influenced on temperature and velocity of particles in stream jet consequently on phase transformation of anatase to rutile and their crystallite size and by optimizing the ratio which can promote structural transformation and grain coarsening in coating.

Two TiO₂/SnO₂:F/substrate hetero-structures (HS) with different geometry were deposited by spray pyrolysis. The thickness for the TiO₂ and SnO₂:F films was 3.8 μm and 2.3 μm, and the band gap energy 3.3 eV and 3.6 eV, respectively. Both films have a transmittance greater than 70% in most of the visible spectrum. The electrical resistivity of the SnO₂:F film was ρ = (1.7)×10^-4Ω ⋅ cm. The surface morphology of the TiO₂ film shows hemispheric agglomerates formed by nano-metric needle/platy shaped particles that give them a porous texture much like a "ball of wool," the length of the needles is from 100 nm and its thickness close to 20 nm. The geometry of HS has an important influence on its efficiency as photocatalyst under low-powered UV radiation. One of the geometry for this HS, in which the TiO₂/SnO₂:F interface is exposed, showed greater efficiency than the TiO₂ and SnO₂:F films separately, or than the common "sandwich" type HS geometry. Specifically, a decrease by 62% of the initial concentration of a watery solution of methylene blue (mb) of 20 ppm in approximately 5 h of UV radiation is observed for the exposed interface HS compared with less than 30% reduction observed for the common sandwich type HS.

Titanium dioxide (TiO₂) and iron oxide (Fe₂O₃) nanoparticles (NPs) were successfully deposited on multiwall carbon nanotubes (MWCNTs) films using a low-cost and simple sparking process. The as-deposited film was annealed at $350^{\circ }$C for 2h to improve their crystallinity. The results show the anatase TiO₂ and hematite Fe₂O₃ NPs with the size of 5–10nm are coated on MWCNTs. The bandgap energy of the as-prepared and the annealed films were 2.3eV and 2.7eV. Photocatalytic activity of the annealed films under visible irradiation is greater than the as-prepared films. Moreover, TiO₂:Fe₂O₃ with the ratio of 3:1 was the optimized condition. Interestingly, the relative current of the annealed films increased to 0.75 when increasing the irradiation time for 5h. This result confirmed that the excited electron from photocatalytic activity can be transferred through the MWCNTs. This is an alternative way to produce the electric current from photocatalysis in the future.

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The properties influencing the photocatalytic activity of TiO₂ particles have been suggested to include the surface area, crystallinity, crystallite size and crystal structure. Therefore, manipulation of the microstructure of titania, especially of nanocrystalline powders, is very important in the preparative process. In this study, nanocrystalline TiO₂ powders with controlled particle size and phase composition were synthesized at low temperature (<80°C) by a modified sol–gel method. The effects of gelation temperature were systematically investigated. It was found that this parameter played a critical role in determining the crystallinity of single phase anatase. With increasing gelation temperature, the crystallinity of anatase improved initially and then decreased if the temperature was raised to 80°C. These nanomaterials were characterized comprehensively by powder X-ray diffraction (including Rietveld analysis), high-resolution transmission electron microscopy, DSC/TGA thermal analysis and UV–Vis spectrometry.

A newly designed fullerodendron was synthesized in good yield (84%) by the use of a Diels-Alder reaction of C₆₀ with an anthryl dendron. Interestingly, the fullerodendron acts as a new catalyst that uses oxygen and light to generate singlet oxygen (¹O₂). The dendron facilitates various types of singlet oxygenation reactions including ene reaction, Diels-Alder reaction, and oxidation of phenol and sulfide.

N-doped anatase TiO₂ has been prepared by thermal decomposition of Ti containing metal complexes. The light absorption onset has been shifted to the visible region by ~ 100 nm when compared to pure TiO₂. The N environment of N-doped TiO₂ has been studied by XPS and the results confirm the presence of N–Ti–O in the N-doped samples. Also, there is a shift in the binding energy values of Ti 2_p3/2, and the additional peak for O 1s in N-doped TiO₂ confirms the increase in the covalent nature of TiO₂ during the N-doping. The photocatalytic activity of N-doped TiO₂ has been studied both in the UV and visible regions and N-doped TiO₂ shows higher activity than the Degussa TiO₂ in the visible region.

Facile, low temperature solvo-combustion synthesis route is used to prepare nanocrystalline ZnFe₂O₄ having spinel structure. Synthesized ZnFe₂O₄ has been analyzed using X-ray diffraction (XRD), TEM and UV-Visible spectrometry. XRD analysis indicates the single-phase of the material ZnFe₂O₄, whose crystallite size was found to be 10 nm evaluated using Scherrer's equation and confirmed from TEM image. The visible-light-activated photocatalytic activity of the nanocrystalline ZnFe₂O₄ has been compared to P-25 degussa TiO₂ reference catalyst, using a visible light for the degradation of phenol.

Nanocrystalline titanium dioxide, TiO₂, is a well studied and commonly used material for photocatalytic applications. However, the control of particle size, monodispersity, large catalytic surface for sufficient adsorption of organic pollutants, recovery and recycle of TiO₂ nanoparticles are challenging tasks. Hence in this work, titania has been introduced into the nanopores (2–10 nm size) of MCM-41 to produce stable nanoparticles of uniform size and shape. Further, the photocatalytic efficiency can be improved by lengthening the life time of the excited electrons/holes during photoreaction. This could be achieved by incorporating molybdenum in to the MCM-41 silica matrix in addition to titania loading. In the present study, the synthesis and the photocatlaytic efficiency of a new photocatalyst TiO₂@Mo-MCM-41 (25 wt.% TiO₂ loaded Mo incorporated MCM-41) are reported. Mo-MCM-41, with different ratios of Si to Mo(Si/Mo = 25,50,75), is synthesized by hydrothermal method and loaded with 25 wt.% TiO₂ using sol–gel method. The photocatalytic activity of the prepared samples was evaluated using methyl orange as a model organic compound. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and nitrogen adsorption–desorption isotherm (BET analysis) measurements were used to investigate the effects of the incorporated elements in the structure of MCM-41. It was found that the photodegradation ability of 25% TiO₂ loaded Mo-MCM-41 was highly related to the amount of Mo atoms present in the sample with the optimum atomic ratio of Si to Mo being 50.

We have synthesized nanocrystalline ZnO by a simple precipitation method. The prepared ZnO was found to be highly phase pure and nanocrystalline hexagonal wurtzite structure. UV–Visible–DRS spectroscopy showed the material to have bandgap energy of 3.22eV. HR-SEM image revealed the material to be made up of distinct hexagonal particles with a highly porous surface. AFM analysis was employed to confirm the high surface roughness and porosity of the material. The photocatalytic activity of the prepared ZnO was evaluated by the degradation of benzene-1,4-diol (hydroquinone), under visible light irradiation. Preliminary experiments showed the catalyst to be effective at neutral pH with an optimum catalyst dosage of 4g/L. Kinetic studies showed the degradation reaction to follow pseudo-first-order kinetics. In the presence of commonly used industrial electrolytes, the catalyst exhibited a decrease in efficiency. Reusability studies showed the catalytic efficiency of ZnO to diminish marginally after the third cycle of reuse.

This work presents the results of pulsed plasma-chemical modification of silicon dioxide nanopowder with zinc oxide nanoparticles (ZnO@SiO₂). The obtained ZnO@SiO₂ powders were characterized by transmission electron microscopy (TEM) and X-ray phase analysis. The size of the synthesized particles was in the range of 20–100nm. The photocatalytic characteristics of ZnO@SiO₂ were studied. When exposed to ultraviolet radiation, the methylene blue (MB) decomposes efficiently. Two samples characterized by the content of silicon tetrachloride in the initial mixture were synthesized. The band gap estimated from the absorption spectra calculated from the diffuse reflectance spectra for these samples was 2.4eV and 2.95eV for indirect transitions and 3.03eV and 3.24eV for direct allowed transitions.

Well crystalline Ag/CdO nanocomposite has been synthesized via the solution combustion synthesis (SCS) route. The Ag/CdO nanocomposite has been characterized in term of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Raman spectroscopy. The crystallinity of the as-synthesized nanocomposite was obtained by using XRD technique. The crystallite size of the nanocomposite was calculated by the Scherrer equation and was found to be 47 nm. The surface morphology was obtained by FESEM spectroscopy. The particles appear to be porous in nature and wool-like morphology was obtained. Raman band at about 278 cm${}^{-1}$ is because of the combination of transverse acoustic and optical phonon modes of cadmium oxide (CdO). Further, the Ag/CdO nanocomposite was used as a photocatalyst for the degradation of methyl orange (MO) dye. Results revealed that the photocatalytic activity of Ag/CdO nanocomposite for the degradation of MO dye increases with increasing the amount of photocatalyst. The rate constant, $k$ values for 100 mg, 150 mg and 200 mg of photocatalyst were 0.83, 2.21 × 10${}^{-3}$ min${}^{-1}$ and 3.81 × 10${}^{-3}$ min${}^{-1}$, respectively.

Porphyrin-based polymers of intrinsic microporosity (PIMs) in photocatalytic degradation of a mustard-gas simulant (2-chloroethyl ethyl sulfide (2-CEES)) was demonstrated. Under blue-ultraviolet (UV) light-emitting diode (LED) irradiation, porphyrin-based PIMs PP-H2 and PP-Zn(II) worked as effective heterogeneous photocatalysts for oxidation of 2-CEES. Solvent played an important role in the conversion and selectivity of 2-CEES oxidation. When AcCN was used as a solvent, PP-H2 and PP-Zn(II) demonstrated complete conversion of 2-CEES in 30 and 50 min, respectively, whereas they showed complete conversion at 60 and 70 min, respectively, when MeOH was used as a solvent. Moreover, these PIMs produced 2-chloroethyl ethyl sulfoxide (2-CEESO) as a major product with small amounts of 2-chloroethyl ethyl sulfone (2-CEESO${}_2)$, ethyl methoxyethyl sulfoxide (EMSO), and vinyl sulfoxide (EVS) as side products in most solvents. However, when MeOH was used as a solvent, highly toxic 2-CEESO₂ was not observed as a side product. Furthermore, these PIMs showed no significant changes in photocatalytic activity even after five cycles of reuse, indicating their high stability. Thus, the series of PIMs prepared herein can perform well as heterogeneous catalysts in photooxidation of 2-CEES under blue-UV LED light, with PP-H2 being the most effective oxidation catalyst, leading to fast conversion and high selectivity.

The well dispersed ZAO nanoparticle with 25–30 nm in diameter was prepared by an ultrasonic-template method. The morphologies, structures, and photoelectricity of the ZAO nanoparticles were analyzed by TEM, XRD, UV-Vis, etc. The thermochemistry behaviors of the precursor were studied by TG-DSC. The composite film with semipermeable structure made from ZAO nanoparticles and collodion can be explored firstly. The photocatalytic properties of the ZAO nanoparticles and composite film were investigated. The composite film can be applied in the sewage treatment field.

Photocatalytic activity can be improved through modified morphology and structure. Sodium tantalate (NaTaO₃) as a semiconductor photocatalyst is extensively used for photocatalytic water splitting. A novel electrochemical route was developed for preparing NaTaO₃ spheres. The method can easily and fast synthesize high pure phase NaTaO₃ spheres at room temperature. The NaTaO₃ sphere structure consists of a crystalline core and an amorphous shell. After a thermal treatment, the NaTaO₃ spheres show an enhanced photoelectrochemical water splitting ability.

The removal of CIP from the environment has become a mandatory issue. In our paper, we have realized the visible-light-driven degradation of CIP on the BiVO₄–Bi₂WO₆ nano-heterojunction photocatalysts. The synthesized photocatalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-Vis) absorption spectra and photoluminescence (PL) spectra. Compared with the single-phase BiVO₄ and Bi₂WO₆ counterparts, BiVO₄–Bi₂WO₆ nano-heterojunction photocatalysts show enhanced photocatalytic degradation activities in visible-light-driven CIP degradation. Particularly, when R_{(Bi2WO6∕BiVO4)} = 10 wt.%, the products exhibit the highest CIP degradation ratio in 60 min of 76.8% under visible light illumination. The tentative mechanism of the interface charge transfer (IFCT) effect in the BiVO₄–Bi₂WO₆ heterojunction structure is also discussed by using the band position calculation.

A new-type photocatalyst of cadmium sulfide carbon nanotubes (CdS/CNTs) was prepared by the hydrothermal method. This as-prepared CdS/CNTs composite photocatalyst was proved to exhibit an excellent photocatalytic activity for degradation of tetracycline (TC). Specially, the 95%-CdS–5%-CNTs composite photocatalyst played the best degradation rate (81.2%) in 60 min under the visible light irradiation. Moreover, this 95%-CdS–5%-CNTs composite photocatalyst possessed great stability and could be used at least four cycles with almost no loss of photocatalytic efficiency. Furthermore, the as-synthesized CdS/CNTs composite photocatalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffused reflectance spectra (UV-Vis), Raman and thermal gravimetry (TG). In addition, the possible mechanism and kinetics of photodegradation of TC with CdS/CNTs photocatalyst was also discussed.

Palygorskite (denoted as Pal) was used as an economical carrier of hybrid photocatalyst TiO₂–Fe_xO_yvia an in situ depositing technique (marked as Pal–TiO₂–Fe_xO_y). The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), brunner-emmet-teller (BET) measurements, X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectra measurements. Results showed that TiO₂–Fe_xO_y composite particles with average size of about 10 nm were loaded onto the Pal fibers' surface. Fe_xO_y acted not only as magnetic source but also took part in the formation of TiO₂–Fe_xO_y heterojunction structure, which resulted in the obvious absorption in visible light region for the obtained Pal–TiO₂–Fe_xO_y composite photocatalyst. The obtained Pal–TiO₂–Fe_xO_y shows excellent photocatalytic activity toward photodegradation of Methyl orange (MO) under visible light irradiation and the degradation ratio reached 94% within 180 min. Moreover, Pal–TiO₂–Fe_xO_y could be readily recovered from the reaction solution by the magnet. Possible mechanism for the enhancement was also proposed.