Photocatalytic activity of nitrogen and copper doped TiO2 nanoparticles prepared by microwave-assisted sol-gel process

Cu and N-doped TiO₂ photocatalysts were synthesized from titanium (IV) isopropoxide via a microwave-assisted sol-gel method. The synthesized materials were characterized by X-ray diffraction, UV-vis diffuse reflectance, photoluminescence (PL) spectroscopy, SEM, TEM, FT-IR, Raman spectroscopy, photocurrent measurement technique, and nitrogen adsorption–desorption isotherms. Raman spectra and XRD showed an anatase phase structure. The SEM and TEM images revealed the formation of an almost spheroid mono disperse TiO₂ with particle sizes in the range of 9-17 nm. Analysis of N₂ isotherm measurements showed that all investigated TiO₂ samples have mesoporous structures with high surface areas. The optical absorption edge for the doped TiO₂ was significantly shifted to the visible light region. The photocurrent and photocatalytic activity of pure and doped TiO₂ were evaluated with the degradation of methyl orange (MO) and methylene blue (MB) solution under both UV and visible light illumination. The doped TiO₂ nanoparticles exhibit higher catalytic activity under each of visible light and UV irradiation in contrast to pure TiO₂. The photocatalytic activity and photocurrent ability of TiO₂ have been enhanced by doping of the titania in the following order: (Cu, N) - codoped TiO₂ > N-doped TiO₂ > Cu-doped TiO₂ > TiO₂. COD result for (Cu, N)-codoped TiO₂ reveals ∼92% mineralization of the MO dye on six h of visible light irradiation.     

Transition metal loaded TiO2 for phenol photo-degradation

Photocatalytic degradation of phenol under both UV radiation and visible light, using TiO₂ (Degussa P-25) and TiO₂ loaded with some transition metal ions (Co, Cu, Fe and Mo) was examined. From the series of metal loaded catalysts, Mo/TiO₂ was the most efficient one. In the presence of Mo, neither TiO₂ anatase/rutile fraction nor its pore size diameter has been affected. However, Mo made its surface more acidic. The percentage of phenol degradation reached under visible light was significantly lower than that under UV radiation due to the lower degree of light absorption by the catalyst surface. From the series of studied catalysts, 2 wt% Mo/TiO₂ was the most efficient one. The synergetic effect between S_BET, mean pore size diameter, catalyst agglomerate size, band gap, ZPC and the type of Mo_xO_y species on TiO₂ surface, depending on Mo loading, created its photocatalytic performance.     

F–B-codoping of anodized TiO2 nanotubes using chemical vapor deposition

Chemical vapor deposition (CVD) was firstly used to simultaneously codope fluorine and boron into TiO₂ nanotubes anodized Ti in C₂H₂O₄ · 2H₂O + NH₄F electrolyte. F–B-codoping was successfully carried out by annealing the anodized TiO₂ nanotubes through CVD, as evidenced from XPS analysis. SEM images showed that the higher the annealing temperature, the greater structure damage of F–B-codoped sample. XRD results confirmed that annealing temperature had an influence on the phase structure and boron and fluorine impurities could retard anatase–rutile phase transition. F–B-codoped samples displayed remarkably strong absorption in both UV and visible range. Under visible-light irradiation, F–B-codoped samples showed the higher I_ph and catalytic activity in methyl orange photoelectrodegradation than F-doped sample and B-doped sample. This showed a convincing evidence of F–B-codoping of TiO₂ had an obvious synergistic effect on the enhancement of photocurrents and photoelectrocatalytic activity.     

Visible light photocatalysis by a Titania–Rhodium(III) complex

Titania hybrid photocatalysts containing 0.5, 1.0, 2.0, and 5.0 wt% of rhodium(III) were prepared by chemisorption of RhCl₃ × 3H₂O onto anatase hydrate powder (TH). Analytical data suggest that a titania–trichlororhodate complex is produced containing a [TiO₂]–O–Rh bond.Similar results are found in the case of modification by RhBr₃ × 3H₂O. Diffuse reflectance spectra exhibit an absorption shoulder throughout the visible region down to 700 nm. Photoelectrochemical measurements indicate that the quasi-Fermi level of electrons is gradually shifted to more anodic potentials with increasing rhodium loading reaching a value of ?0.34 V at pH 7 (vs. NHE) in the case of 5.0%RhCl₃/TH. This is more anodic by 210 mV as compared to unmodified TH. Upon visible light irradiation this photocatalyst induces a fast mineralization of 4-chlorophenol whereas cyanuric acid, which is known to be mineralized in the presence of the analogous Pt(IV) modified titania, is not degraded.     

TiO2 nanotubes as recyclable catalyst for efficient photocatalytic degradation of indigo carmine dye

TiO₂ nanotubes have been synthesized in a hydrothermal system. The nanotubes were characterized by scanning electronic microscopy (SEM), FT-Raman spectroscopy and surface charge density by surface area analyzer. These nanocatalysts were applied to photocatalyse indigo carmine dye degradation. Photodegradation ability of TiO₂ nanotubes was compared to TiO₂ anatase photoactivity. Indigo carmine dye was completely degraded at 60 and 110 min of reaction catalysed by TiO₂ nanotubes and TiO₂ anatase, respectively. TiO₂ nanotubes presented high photodegradation activity at pH 2 and TiO₂ anatase at pH 4. TiO₂ nanotubes were easily recycled whereas the reuse of TiO₂ anatase was not effective. Nanotubes maintained 90% of activity after 10 catalytic cycles and TiO₂ anatase presented only 10% of its activity after 10 cycles.     

Mesoporous TiO2−xAy (A = N,S) as a visible-light-response photocatalyst

Mesoporous TiO_2?xA_y (A = N, S) thin films were fabricated using thiourea as a doping resource by a combination of sol-gel and evaporation-induced self-assembly (EISA) processes. The results showed that thiourea could serve two functions of co-doping nitrogen and sulfur and changing the mesoporous structure of TiO₂ thin films. The resultant mesoporous TiO_2?xA_y (A = N, S) exhibited anatase framework with a high porosity and a narrow pore distribution. The formation of the O–Ti–N and O–Ti–S bonds in the mesoporous TiO_2?xA_y (A = N, S) were substantiated by the XPS spectra. A new bandgap in visible light region (520 nm) corresponding to 2.38 eV could be formed by the co-doping. After being illuminated for 3 h, methyl orange could be degraded nearly completely by the co-doped sample under both ultraviolet irradiation and visible light illumination. While pure mesoporous TiO₂ could only degrade 60% methyl orange under UV illumination and showed negligible photodegradation capability in the visible light range. Furthermore, the photo-induced hydrophilic activity of TiO₂ film was improved by the co-doping. The mesoporous microstructure and high visible light absorption could be attributed to their good photocatalytic acitivity and hydrophilicity.     

TiO2/EDTA-rich carbon composites: Synthesis,characterization and visible-light-driven photocatalytic reduction of Cr(VI)

TiO₂/EDTA-rich carbon composites exhibits excellent photoreduction of Cr(VI) activity via ligand-to-metal charge transfer process.     

Hydrogen peroxide-photofuel cell using TiO2 photoanode

Hydrogen peroxide-fuel cell (H₂O₂-FC) possesses a theoretical power generating efficiency of 119% much larger than hydrogen/oxygen (H₂/O₂)-FC (82.9%) with a thermodynamic electromotive force of 1.09 V. This communication presents the prototype of H₂O₂-photofuel cell (PFC) without using noble metal catalyst. The H₂O₂-PFC is comprised of mesoporous anatase TiO₂ nanocrystalline film coated on fluorine-doped tin oxide electorode (mp-TiO₂/FTO, photoanode), glassy carbon (cathode), and an aqueous electrolyte solution containing 0.1 M NaClO₄ and 0.1 M H₂O₂. Under UV-light irradiation, the H₂O₂-PFC stably works, providing a short-circuit current of 0.24 mA cm^− 2 and an open-circuit voltage of 0.72 V at ambient temperature and pressure, while current hardly flows in the dark. Further, the PFC responds to visible-light due to the charge-transfer complex formation of H₂O₂ on the TiO₂ surface.     

Synthesis,characterization and photocatalytic performance of W,N, S-tri-doped TiO2 under visible light irradiation

W–S–N-tri-doped TiO₂ photocatalysts (WSNTiO₂) were prepared by a simple sol–gel method. Tungstic acid, sodium sulfate and urea were used as tungsten, sulfur and nitrogen sources, respectively. The morphology and microstructure characteristics of the photocatalysts were evidenced by means of XRD, BET, TEM, SEM and UV–vis DRS techniques. The XRD results show that the main crystal phase of samples is anatase. It was also found that the tri-doping of TiO₂ increases its BET specific surface area from 95 to 121 m²·g⁻¹. Besides, it was shown that tri-doping narrows the band gap of TiO₂ effectively, which has greatly improved the photocatalytic activity in the visible light region. The photocatalytic activity of tri-doped TiO₂ powders was compared to that of bi-doped ones through the degradation of Congo Red (CR) under visible irradiation. Thus, the prepared 0.5% W–N–S–TiO₂ heat treated at 450 °C showed the best photocatalytic activity compared to the prepared pure TiO₂, Degussa P25, and co-doped samples (WNTiO₂ and WSTiO₂). In particular, a Congo Red degradation rate of approximately 99% was reached after only 35 min of visible light irradiation in the presence of 0.5% of WNSTiO₂. Total organic carbon (TOC) removal of CR was up to 72% and confirmed its significant mineralization in the presence of 0.5% of WNSTiO₂ photocatalyst.     

Bubble-like CdSe nanoclusters sensitized TiO2 nanotube arrays for improvement in solar cell

Solar cells were fabricated using novel bubble-like CdSe nanoclusters sensitized highly ordered titanium oxide nanotube (TiO₂ NT) array, prepared by anodization technique. The CdSe sensitization of TiO₂ NT arrays was carried out by a chemical bath deposition method with freshly prepared sodium selenosufite, ammonium hydroxide and cadmium acetate dehydrate at different deposition times: 20, 40 and 60 min. The adsorption of CdSe nanoclusters on the upper and inner surface of the TiO₂ NT arrays has been confirmed by field emission scanning electron and transmission electron microscopes. The results show the variation in cell a performance with different deposition times (20, 40, and 60 min) of CdSe on TiO₂ NT arrays. The solar cell with CdSe, deposited for 60 min, shows reasonably high photovoltaic property compared to the reported results of similar studies. This solar cell shows the maximum photoelectric conversion efficiency of 1.56% (photocurrent of 7.19 mA/cm²; photovoltage of 0.438 V; and fill factor of 49.5%) and average incident photon to current efficiency of 50.2%. The photocurrent, incident photon-current efficiency and electron lifetime have been improved due to the increase of covered area and size of bubble-like CdSe nanoclusters on TiO₂ NT arrays with the increase of deposition time.     

Anatase TiO2 nanosheet: An ideal host structure for fast and efficient lithium insertion/extraction

Anatase TiO₂ nanosheets with largely exposed (0 0 1) facets have been synthesized by a modified method. Exploitation of these nanosheets as a host structure for reversible lithium insertion/extraction has been investigated. It is found that these TiO₂ nanosheets manifest much lower initial irreversible losses compared to other anatase TiO₂ nanostructures, and excellent cycling performance at a charge–discharge rate as high as 20 C. The superior reversible lithium storage capability can be attributed to the ultrathin nanosheet structure: a large exposed effective area and a very short diffusion path. It thus attests the promising use of these anatase TiO₂ nanosheets in high-power lithium–ion batteries.     

Solar active nano-TiO2 for mineralization of Reactive Red 120 and Trypan Blue: 1st Nano Update

Nano-TiO₂ was synthesized by sol–gel method. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) images, transmission electron microscope (TEM), BET surface area measurement and DRS analysis. The formation of anatase phase nano-TiO₂ was confirmed by XRD measurements and its crystalline size is found to be 15.2 nm. SEM images depict the crystalline nature of prepared TiO₂. The BET surface area of prepared TiO₂ is found to be 86.5 m² g^?1 which is higher than that of commercially available TiO₂–P25. The photocatalytic activity of prepared anatase phase TiO₂ has been tested for the degradation of two azo dyes: Reactive Red 120 (RR 120) and Trypan Blue (TB) using solar light. The photocatalytic activity of nano-TiO₂ is higher than TiO₂–P25 under solar light. The mineralization of dyes has been confirmed by chemical oxygen demand (COD) measurements.     

Photocatalytic decomposition of 4-chlorophenol over an efficient N-doped TiO2 under sunlight irradiation

Using a new nitrogen precursor of a mixture of ammonia and hydrazine hydrate, N-doped TiO₂ photocatalyst with a high efficiency under visible light was synthesized by a precipitation method. The analysis of X-ray photoelectron spectroscopy (XPS) suggested that the doping concentration of nitrogen was 0.45 at%, while it was 0.21 at% or 0.24 at% using single ammonia or hydrazine hydrate as nitrogen precursor. The patterns of the electron paramagnetic resonance spectroscopy (EPR) indicated that the paramagnetic species of NO₂^2?, NO and Ti³⁺ existed as the proposed active species. The ultraviolet–visible (UV–vis) spectra revealed that the band-gap of the N-doped TiO₂ was 3.12 eV, which was slightly lower than 3.15 eV of pure TiO₂. The N-doped TiO₂ showed higher efficiency under both ultraviolet (UV) and visible light irradiations. Moreover, the degradation grade of 4-chlorophenol (4-CP) using the as-synthesized N-doped TiO₂ under sunlight irradiation for 6 h was 82.0%, which was higher than 66.2% of the pure TiO₂, 60.1% or 65.2% of the N-doped TiO₂ using single ammonia or hydrazine hydrate as precursor. Density functional theory (DFT) calculations were performed to investigate the visible light response of the N-doped TiO₂. Our study demonstrated that the visible activities vary well with the concentrations of NO₂^2? species incorporated by N–TiO₂ series photocatalysts and the higher activity of the as-prepared N-doped TiO₂ was attributed to the enhancement of the concentration of NO₂^2? species.     

Facile preparation of large aspect ratio ellipsoidal anatase TiO2 nanoparticles and their application to dye-sensitized solar cell

A simple one-step heat-treatment of peroxotitanate complex aqueous solution at around 100 °C was resulted in the formation of ellipsoidal anatase TiO₂ nanoparticles having a high aspect ratio with no branches. The length of these ellipsoidal TiO₂ falls in the range of 200–350 nm, depending on mole ratio of Ti⁴⁺/H₂O₂. Dye-sensitized solar cell based on these ellipsoidal nanocrystalline TiO₂ as photoanode was fabricated and characterized.     

Improved anti-inflammatory and anticancer properties of celecoxib loaded zinc oxide and magnesium oxide nanoclusters: A molecular docking and density functional theory simulation

Present study offers great prospects for the adsorption of anti-inflammatory celecoxib molecule (CXB) over the surface of zinc oxide (Zn₁₂O₁₂) and magnesium oxide (Mg₁₂O₁₂) nanoclusters in several environments by performing robust theoretical calculations. Density functional theory (DFT), time-dependent density functional theory (TDDFT) and molecular docking calculations have been extensively carried out to predict the foremost optimum site of CXB adsorption. It has been observed that the CXB molecule prefers to be adsorbed by its SO₂ site on the Zn-O and Mg-O bonds of the Zn₁₂O₁₂ and Mg₁₂O₁₂ nanoclusters instead of NH₂ and NH sites, where electrostatic interactions dominate over the bonding characteristics of the conjugate complexes. Furthermore, the presence of interactions between the CXB molecule and nanoclusters has also been evidenced by the UV–Vis absorption spectra and IR spectra. Molecular docking analysis has revealed that both adsorption states including CXB/Zn₁₂O₁₂ and CXB/Mg₁₂O₁₂ have good inhibitory potential against protein tumor necrosis factor alpha (TNF-α) and Interleukin-1 (IL-1), and human epidermal growth factor receptor 2 (HER2). Hence they might be explored as efficient TNF-α, IL-1, and HER2 inhibitors. Hence from the study, it can be anticipated that these nanoclusters can behave as an appropriate biomedical carrier for the CXB drug delivery.     

The adsorption and activation of formic acid on different anatase TiO_2 surfaces

Formic acid photodegradation is one of the most important reactions in organic pollution control, and helps to improve the hydrogen generation efficiency in titanium dioxide catalyzed water photodecomposition. Based on density functional theory and Reax FF molecular dynamics, the adsorption, diffusion and activation of formic acid on the different anatase TiO_2(101),(001),(010) surfaces are investigated.The result shows that the adsorption of COOH on anatase TiO_2 surface shrinks the energy gap between the dehydrogenation intermediate COOH and HCOO. On the anatase TiO_2(101) surface, the formic acid breaks the O–H bond at the first step with activation energy 0.24 eV, and the consequent break of α-H become much easier with activation energy 0.77 eV. The dissociation of α-H is the determination step of the HCOOH decomposition.     

Synthesis and properties of polyfluorene copolymers bearing thiophene and porphyrin

To search for more wider absorption and higher charge carriers mobilities materials of polymer solar cell, a series of soluble alternating polyfluorene copolymers were synthesized by palladium-catalyzed Suzuki coupling reaction. Their structures were determined by 1H NMR, IR and UV-vis. And their UV-vis absorption spectra indicated that they had strong absorption over 600 nm spectral range and nearly cover 400-700 nm visible region. The band gaps of copolymers calculated according to cyclic voltammetry （CV） were between 1.96 and 2.03 eV. Polymer：TiO2 bulk-heterojunction films were made from mixtures of polymer and titanium isopropoxide, a precursor for TiO2, via hydrolysis in air overnight. The photoluminescence at 380-800 nm of the blend film of PT-TPP20 （5 mg/mL）：Ti（OC3H7）4 （80 μL/mL） （20% volume fraction） was significantly quenched in the 50% Ti（OC3H7）4 blend film, indicating that rapid and efficient separation of photoinduced electron-hole pairs.     

Visible LED light photoelectrochemical sensor for detection of L-Dopa based on oxygen reduction on TiO2 sensitized with iron phthalocyanine

The present work describes the development of a new strategy to photoelectrochemical detection of L-Dopa at low potential based on oxygen reduction on TiO₂ sensitized with iron phthalocyanine (FePc/TiO₂). The FePc/TiO₂ composite shows a photocurrent 10-fold higher than that of pure TiO₂ nanoparticles and it was 4-fold higher than that of FePc exploiting visible light. The band gaps of pure TiO₂ nanoparticles, FePc and FePc/TiO₂, calculated according to the Kubelka–Munk equation, were 3.22 eV, 3.11 eV and 2.82 eV, respectively. The FePc/TiO₂ composite showed a low charge transfer resistance in comparison to the photoelectrode modified with FePc or TiO₂. Under optimized conditions, the photoelectrochemical sensor shows a linear response range from 20 up to 190 μmol L^− 1 with a sensitivity of 31.8 μA L mmol^− 1 and limit of detection of 1.5 μmol L^− 1 for the detection of L-Dopa.     

TiO2/polyaniline composites： An efficient photocatalyst for the degradation of methylene blue under natural light

Polyaniline (PAn) sensitized nanocrystalline TiO_2 composites (TiO_2/PAn) were successfully prepared and used as an efficient photocatalyst for the degradation of dye methylene blue (MB).The results showed that PAn was able to sensitize TiO_2 efficiently and the composite photocatalyst could be activated by absorbing both the ultraviolet and visible light (λ:190～800nm),whereas pure TiO_2 absorbed ultraviolet light only (λ<380nm).Under the irradiation of natural light,MB could be degraded more efficiently on the TiO_2/PAn composites than on the TiO_2.Furthermore,it could be easily separated from the solution by simple sedimentation.     

Temporal evolution study of the plasma induced by CO2 pulsed laser on targets of titanium oxides

This paper reports studies on time-resolved laser induced breakdown spectroscopy (LIBS) of plasmas induced by IR nanosecond laser pulses on the titanium oxides TiO and TiO₂ (anatase). LIBS excitation was performed using a CO₂ laser. The laser-induced plasma was found strongly ionized yielding Ti⁺, O⁺, Ti^2 +, O^2 +, Ti^3 +, and Ti^4 + species and rich in neutral titanium and oxygen atoms. The temporal behavior of specific emission lines of Ti, Ti⁺, Ti^2 + and Ti^3 + was characterized. The results show a faster decay of Ti^3 + and Ti^2 + ionic species than that of Ti⁺ and neutral Ti atoms. Spectroscopic diagnostics were used to determine the time-resolved electron density and excitation temperatures. Laser irradiation of TiO₂-anatase induces on the surface sample the polymorphic transformation to TiO₂-rutile. The dependence on fluence and number of irradiation pulses of this transformation was studied by micro-Raman spectroscopy.