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ABSTRACT Polyaniline/TiO2−SiO2 composites were prepared by an in situ chemical oxidation polymerization approach in the presence of hybrid TiO2−SiO2 fillers. The obtained polyaniline/TiO2−SiO2 composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), and current−voltage (I−V) measurements. SEM picture shows a variation in morphology of polyaniline (PANI) from fiber shape to relatively regular particle shape with increasing TiO2−SiO2 contents in the composites. The floccule-like structures were observed by high resolution TEM, which may help improve the efficiency of conductive network. SEM, XRD, TG, and FTIR spectra all reveal that a relatively strong interaction exist between TiO2−SiO2 and PANI. The I−V characteristics in such composites indicate that the charge transport is mainly governed by the space charge effects, which occurs at the interface between the conducting PANI and TiO2−SiO2. Meanwhile, PANI/TiO2−SiO2 composites exhibit significant increase in conductivity than PANI/TiO2 or PANI/SiO2. The reasons about high conductivity of PANI/TiO2−SiO2 have also been discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2288-2295, 2013 [ABSTRACT FROM AUTHOR]

Abstract: Various contents of Ag nanoparticles were successfully introduced into the N-doped TiO2 photocatalysts via a hydrothermal procedure in the silver-ammonia solutions with different Ag concentrations. Effects of Ag loading on the structure and properties of N-doped TiO2 photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, fluorescence spectroscopy (FL), UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and N2 physical adsorption analysis. The relationship between the stability of N dopants in TiO2 lattice and the Ag loading content was investigated for the first time. The results confirm that Ag nanoparticles loading on TiO2 surfaces significantly restrain the escape of the N dopants from the oxide during the hydrothermal process, and the escape rate of N dopants decreased gradually with the increase of Ag loading amount. The dependence of photocatalytic activity on Ag content was also investigated through degradation of rhodamine B (RhB) under visible light irradiation. It was found that the photocatalytic activity increases gradually with increasing Ag content first, and then decreases after exceeding the optimal Ag content. Therefore, the photocatalytic activity of Ag/N co-modified TiO2 photocatalysts can be adjusted by the Ag content. [Copyright &y& Elsevier]

Abstract: In this paper, TiO2 film coated on fiberglass cloth was synthesized by sol–gel method and further sensitized by CdS nanoparticles using a sequential chemical bath deposition technique. Gaseous benzene was adopted as a model pollutant to evaluate the photocatalytic performances of the supported TiO2 films sensitized with variable content of CdS nanoparticles, which obtained by adjusting the concentration of Cd2+ or S2− precursor solution. Along with the increase of the CdS amount, the photocatalytic activity of these samples initially increases and then shows a downward trend. When the concentration of Cd2+ or S2− precursor solution achieved 0.005M, the sample performs the best photocatalytic property and the degradation efficiency reaches 92.8% and 32.7% under UV–vis and visible light irradiation, respectively. The enhancement of the photocatalytic activity could be attributed to the formation of micro-heterojunction. However, a thick CdS sheath covered catalyst surface will form when high concentration of Cd2+ or S2− solution is used. The low photogenerated electron–hole pairs separation efficiency and the photocorrosion process of CdS decrease the photocatalytic activity gradually. [Copyright &y& Elsevier]

Abstract: TiO2-based nanosheet (TNS) was prepared by the alkaline hydrothermal treatment of P25, which was characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD) and nitrogen adsorption–desorption measurement. Its adsorption and regeneration properties for removal of high-chroma crystal violet (CV) were systematically investigated. The prepared TNS has much higher specific surface area of 207m2/g and exhibits much stronger adsorption for CV than the raw material P25. The maximum adsorption capacity of TNS as determined from the Langmuir isotherm is 56.3mg/g. The enhancement of adsorption capacity is ascribed to the increasing of specific surface area and surface hydroxyl groups, which can provide much more adsorption sites and stronger electrostatic attraction. It was further found that H2O2 can produce a synergetic photocatalytic degradation effect with TNS under UV–Vis irradiation, and the regeneration of TNS was effectively achieved by H2O2-assisted photocatalytic degradation process. The good reusability of prepared TNS in the cyclic adsorption–regeneration experiments indicates that it may be useful for dealing with dye wastewater. [Copyright &y& Elsevier]

Vanadium doped TiO 2 -based nanosheets (V-TNSs) with different V/Ti ratios were prepared by a facile one-pot hydrothermal method using vanadium nitrate and P25 as the vanadium precursor and titanium precursor, respectively. The results indicated that as-synthesized photocatalysts exhibited sheet-like structure with large specific surface area (270–340 cm 2 /g) and small thickness (4–5 nm). XPS results revealed that vanadium exists in the form of V 4+ and V 5+ , and the binding energies of Ti O bonds have been changed with the concentration of vanadium. Vanadium doping resulted in considerable enhancement of visible light absorption, red-shift, and the band-gap of photocatalysts reduced from 3.18 eV to 2.91 eV. The density functional theory (DFT) calculations for band structure and total energy also provided a good explanation and further confirmation for the experimental results. It has been found that the photo-activity increased gradually with the concentration of vanadium, and then decreased after attaining a maximum with an optimal content of vanadium at 1.0 at.% for RhB or Cr(VI). The reaction rate K app of 1.0%-V-TNSs are 9.27-fold and 3.26-fold as compared to undoped TNSs under UV–vis and visible light irradiation, respectively. The cyclic tests that performed six times demonstrated high stability and reusability of the photocatalysts. A possible alternate mechanism for the enhancement of the photocatalytic activity under visible-light irradiation was also proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photoelectrochemical-electrostatic co-sense is realized with black phosphorus. • Multivariate van der Waals heterojunctions are used to engineer material defects. • Response can be promoted to 236.4 μA cm−2 stimulated by AEF combined with light. • Response is 1.8 and 19.4 times higher than that stimulated by AEF or light alone. Nowadays, the two-dimensional (2D) materials have shown broad prospects for their fascinating attributes, yet the ineluctable material defects still restrict their applications. Herein, a spin-coating technology is employed to establish few-layers borophene/bismuthene/Ti 3 C 2 T x MXene/black phosphorus (BP) laminations, and then a photoelectrochemical-electrostatic coupling sensor is developed. It is demonstrated that the rough defects on the Si/Ag substrate can be patched by the upper few-layers borophene and bismuthene, and the residual defects on the Ti 3 C 2 T x layer can be exactly patched by the as-derived TiO 2 and the upper 2D BP layers. These 2D metals have been bounded with adjacent 2D semiconductors through van der Waals interactions to greatly depress the metal-induced gap states and enhance the carrier transport. Under just light irradiation or ambient electric field (AEF), the current response of the lamination electrode obviously increases, compared to that without the key BP cover layer. Further, the response can be promoted to 236.4 μA cm−2, stimulated by AEF combined with light irradiation, which is about 1.8 times and 19.4 times higher than that of light irradiation alone and AEF alone, respectively. These can be attributed to the defect engineering effect, by which the 2D materials constantly mending the defects. [ABSTRACT FROM AUTHOR]

Abstract: Different mesostructured titania (TiO2) powders were synthesized via a sol–gel method using amphiphilic triblock copolymer F38 as the structural template. Mesostructural evolution of TiO2 powders depending on template loading and calcination was investigated systematically. Results showed that the polymeric template as well as calcination played an important role in tuning morphology, grain size, crystal phase, mesoporosity and specific surface area of the synthesized mesoporous TiO2. [Copyright &y& Elsevier]

Abstract: TiO2/SiO2 composite photocatalysts were prepared via a simple reflux-stir process. These composites exhibit a highly distributed state between TiO2 (P25) and fumed silica (SiO2) nanoparticles, and the SiO2 nanoparticles surround the TiO2 crystalline grains closely. The photoactivity of the composites was investigated by photocatalytic oxidation of gaseous benzene. By adjusting the Ti/Si mole ratio from 50:1 to 1:1, the photocatalytic efficiency of the TiO2/SiO2 composites ascends firstly and then decreases. The optimum Ti/Si mole ratio is 30:1, and the photocatalytic efficiency reaches 92.3% within 120min, which is 6.8 times higher than that of P25. Additionally, recycled tests which performed ten times demonstrate the nanocomposites possess a pretty good recyclability. The excellent photocatalytic performances can be chiefly attributed to the good dispersion state between TiO2 and SiO2. The special structure helps the formation of a high population of hydroxyl groups on the catalysts surface, and these hydroxyl groups greatly improve the charge separation efficiency and the reaction rate. In addition, the enhanced adsorption powers to water vapor and benzene also contribute to the high photoactivity. [Copyright &y& Elsevier]

Abstract: The adsorption of a NO molecule on 72 atom N-doped TiO2 nanoparticles has been studied by first principles calculations. Two types of adsorption are considered in the calculations. In one type of the adsorption, the NO molecule forms one bond with the particle, while in the other type of adsorption, the NO molecule forms two bonds with the particle. The second type of adsorption is more energetic favorable. The adsorption energies, bond lengths, density of the states (DOSs), and the difference of the charge density are calculated to investigate the adsorption. In the adsorption process, the unpaired electron of the NO molecule transfers to the empty state of the particle, making the Fermi levels lower. As a result, the electrons of the N-doped system occupy lower energy states, making the system energy lower than that of the undoped particle. Since the adsorption of a NO molecule on N-doped nanoparticles is stronger than that on undoped particles, N-doped particles can adsorb more NO molecules on their surfaces than the undoped particles do. Meanwhile, there are more adsorption sites on the N-doped particles, on which the adsorption energies are much higher than that of the undoped particle, some of them are even higher than the highest adsorption energy of the undoped particle. It suggests that N-doped particles are more active and they can adsorb more small toxic gas molecules in the air. So, the doping method can be used to remove NO molecules for the air pollution control through the surface adsorption strategy. [Copyright &y& Elsevier]

Graphical abstract Highlights • Ni-TNSs with high stability and recyclable usability were prepared by one-pot method. • Ni x O y loading results in the changes in the structure of the TNSs and red shift. • Ni x O y loading leads to obviously increase of the Ti3+ ions content. • Ni x O y loading can effectively trap electrons to enhance the separation of charges. • Ni-TNSs exhibit excellent visible-light photocatalytic activities for organic pollution. Abstract Two-dimensional (2D) TiO 2 -based nanosheets (TNSs) decorated with surface-enriched Ni x O y (Ni = Ni2+, Ni3+) nanoparticles (Ni-TNSs) were synthesized and found to exhibit a high visible light photocatalytic activity. The thickness and high specific surface area of the Ni-TNSs were measured to be ∼5 nm and 280–350 cm2/g, respectively. Properties, such as the crystal structure, crystallinity, surface area and visible light absorption of the TNSs, were closely associated with the distributed nanoparticles of Ni x O y (The particle size is less than 2 nm) on the surface. Surface photocurrent, fluorescence spectroscopy, linear sweep voltammetry and Tafel measurements revealed that the separation efficiency of the photogenerated charge carriers can be improved by optimizing the concentration of Ni x O y (the optimized ratio of Ni/Ti = 3.0 at.%). The photocatalytic degradation of organic pollutants (RhB and MB) under visible light was measured, and the efficiency also strongly depended on the amount of Ni x O y nanoparticles with an optimal percentage of 3.0 at.%. The photoreactivity of the sample was further studied by determining the formation of photoinduced hydroxyl radicals (OH) by applying coumarin (COU) as a probe material and by obtaining ESR spectra of the superoxide radical adducts (O 2 −) trapped by DMPO (5,5-dimethyl-1-pyrroline n-oxide). Ten cyclic tests were used to confirm the high stability. A feasible mechanism is described to interpret the enhanced photocatalysis. [ABSTRACT FROM AUTHOR]

Buffer layers of TiO 2 nanoparticles are introduced on the surface of the MIL-101-Cr, a kind of metal-organic frameworks (MOFs), to improve performances of MOFs/Nafion proton exchanging membranes. A series of Nafion composite membranes are fabricated by doping TiO 2 -wrapped MIL-101-Cr (TiO 2 @MIL-101-Cr). The water uptakes of composite membranes reasonably increase while their swelling ratios unexpectedly reduce in comparison to pristine Nafion. Nevertheless, the swelling ratios of composite membranes gradually increase with the increment of TiO 2 @MIL-101-Cr due to their enlarged free volumes and more amorphous phases. The introduction of additive facilitates water molecules diffusion as well as overall hydration of the composite membranes, resulting in a significant increment in the proton conductivity. As a result of the formation of extra proton conducting highways both around/in TiO 2 @MIL-101-Crs and the Nafion matrix, a composite membrane in single-cell possesses a maximum power density of 0.946 W/cm2. Furthermore, higher thermal and oxidative stabilities are observed for the composite membranes. This work demonstrates that the addition of encapsulated structural TiO 2 @MIL-101-Crs in Nafion is promising for fabricating proton exchanging membranes with superior electrochemical performance and high thermal, oxidative stabilities. [Display omitted] • TiO 2 @MIL-101-Cr is synthesized for preparation MOFs/Nafion composite membranes. • More amorphous phases and high water uptake for MOFs/Nafion membranes are found. • Extra highways for proton diffusion are formed in the composite membranes. • TiO 2 @MIL-101-Cr-5/Nafion membrane possesses a power density of 0.946 W/cm2. • Higher thermal and oxidative stabilities are observed for the composite membranes. [ABSTRACT FROM AUTHOR]

Y 2 O 3 modified TiO 2 nanosheets (Y 2 O 3 @TNSs), capable of exhibiting sun light, were synthesized through one pot/hydrothermal method using Y (NO 3 ) 3 as precursor. Multiple techniques were applied to investigate the structures, morphologies, optical and electronic properties and photocatalytic performance of the as-prepared samples. The Y 2 O 3 @TNSs, with thickness of approximately 3–4 nm, large surface area of 240–350 m 2 /g, were full of Y 2 O 3 nanoparticles highly dispersed on the surface. The introduction of Y 2 O 3 influenced the crystallinity and the structure evolution of TNSs, besides, improved the light absorption ability. The surface photo-current and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be improved by an appropriate modification. The degradation activity of this sun-light-induced photocatalytic has enhanced apparently on 4-Chlorophenol and K 2 Cr 2 O 7 solution, the degradation efficiency of 4-Chlorophenol reached 5.69 times than that of P25, and the maximum TOC removal obtained after 120 min was 67.6%, indicating that most organic compounds were released from the solution. The enhancement in the photocatalytic activity was attributed to the synergetic effect of the Y 2 O 3 and TNSs, which led to a fast separation and slow recombination of photo-induced electron-hole pairs. Consequently, the high efficiency in the experiments showed a promising application of the catalyst in the oxidation or reduction degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

TiO 2 -based nanosheets (TNSs) co-modified by Fe 2 O 3 and Ho 2 O 3 were synthesized by one-pot hydrothermal method using Fe(NO 3 ) 3 and Ho(NO 3 ) 3 as precursors compositing with TiO 2 . The Fe 2 O 3 /Ho 2 O 3 -TNSs heterojunctions possessed a thickness of approximately 3–4 nm, large specific surface area of 210–310 cm 2 /g, with Fe 2 O 3 and Ho 2 O 3 nanoparticles highly dispersed over the surface of the nanosheets. The crystallization of the samples gradually increased with the amount of Fe 2 O 3 nanoparticles, which was confirmed by the XRD, BET and Raman spectra, indicating that Ho 2 O 3 and Fe 2 O 3 influenced the crystallinity and structure evolution of the TNSs, besides, led to an improved the visible-light absorption. Surface photocurrent and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be efficiently improved by an appropriate amount of modification. The Fe 2 O 3 /Ho 2 O 3 -TNSs exhibited synergistic effect on photocatalytic degradation of RhB as well as MO under visible light. The highest efficiency was obtained by 0.05%-Fe 2 O 3 /Ho 2 O 3 -TNSs (Fe:Ho:Ti = 0.05:1:100), which was 8.86 and 6.72 times than that of individual 1.0%-Ho 2 O 3 -TNSs (Ho:Ti = 1:100) and 0.05%-Fe 2 O 3 -TNSs (Fe:Ti = 0.05:100), respectively. The possible mechanism for enhanced visible-light-induced photocatalytic activity was proposed. Ho 2 O 3 introduced in the photocatalysts may act as the hole capture while Fe 2 O 3 may share the same Fermi levels with TNSs and serve as the electron capture center in the n-n-p system, which reduced the recombination rate of photo-induced electron-hole pairs. [ABSTRACT FROM AUTHOR]

Visible-light-driven (VLD) CoO x loaded TiO 2 -based nanosheets (Co-TNSs) with surface-enrich CoO x nanoparticles were successfully synthesized by using a facile one-pot hydrothermal method. The photocatalysts were characterized by SEM, AFM, HRTEM, XRD, Raman, XPS, FL and the surface photocurrent (SPC) technique, etc. The as-synthesized samples exhibit sheet-like structure with large specific surface area (260–350 cm 2 /g) and small thickness (3–4 nm). The CoO x nanoparticles (1–2 nm) are highly dispersed on the surface of TNSs. Loaded CoO x nanoparticles not only have influenced the crystal structure, crystallinity and surface area of the TNSs, but also resulted in considerable enhancement of visible-light (VL) absorption and a red-shift of the band gap of the TNSs. XPS results reveal that cobalt mainly exists in the form of Co 2+ and Co 3+ , and the binding energies of Ti O bonds are changing with the loaded amount of CoO x nanoparticles. FL and SPC results indicate appropriate amount of CoO x (2.5 at.%) loading can effectively inhibit the recombination of photo-generated electron-hole pairs, thus improve the separation efficiency of charge carriers. The photocatalytic activity of the samples was evaluated by the dichromate (Cr(VI)) solution under VL irradiation. It can be found that the Co-TNSs photocatalysts showed excellent VL photocatalytic activity for the removal of Cr(VI). Initially the photocatalytic activity increased with the content of CoO x , and then decreased after attaining a maximum value at an optimal content (2.5 at.%) for degradation of aqueous Cr(VI) solution. The addition of Ca 2+ promotes photocatalysis owing to its ionic bridging function in the form of TiOH + Cr(VI)–Ca 2+ Cr(VI) linkages, while SO 4 2− slightly inhibits the photo-reduction of Cr(VI), indicating good synergy of photocatalysis and adsorption even at higher ionic strength of electrolyte. The photocatalytic reduction of Cr(VI) is also significantly promoted by phenol and synergism between Cr(VI) reduction and degradation of phenol which is demonstrated by measuring the effect of multiple usage of Co-TNSs on its photocatalytic efficiency. Desorbed Co-TNSs (Co-TNSs-Des) are easily regenerated and reused for Cr(VI) removal with excellent performance. A possible alternate mechanism for the enhancement of photocatalytic activity under visible light irradiation is also proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple and effective way for growing MoS 2 lamellar vertical structure is employed. • The few-layer edge-on MoS 2 is subtly constructed on TiO 2 octahedral nanoparticles. • The structure evolution and interfacial structure are systematically studied by TEM. • Edge-on structure MoS 2 has excellent piezoelectric catalytic degradation ability. Imaging the lattice origin of few-layer edge-on MoS 2 /TiO 2 heterostructure at different growth stages could provide direct information for understanding the mechanism of its enhanced piezoelectric property. Via modifying the substrate surface to grow anatase TiO 2 nanoparticles with truncated octahedron structure, few-layer MoS 2 was exquisitely grown along the {1 0 1} basal planes of TiO 2 by Van der Waals contact, and finally form an edge-on structure at the top edge of TiO 2 nanoparticles due to steric hindrance. The vertical growth of few-layer MoS 2 on the TiO 2 surface endows not only better electronic contact between MoS 2 and TiO 2 substrate for fast electrons transfer but also high structure stability of piezoelectric properties. The piezocatalytic degradation ability is enhanced with the increase of hydrothermal reaction time, and the MoS 2 /TiO 2 -24 h sample exhibits the highest piezocatalytic activity under dark condition which demonstrates a high removal efficiency of 96.0% Rhodamine B within 60 min. This study establishes a relationship between the piezoelectric property of few-layer edge-on MoS 2 /TiO 2 heterostructure and its growth mechanisms, and sheds light on the rational design of electric contact between transition metal dichalcogenide and semiconductor with specific crystal plane which is significant to the improvement of carrier separation and transport. [ABSTRACT FROM AUTHOR]

Abstract: TiO2-based nanosheet (TNS) was modified with Ag2O, and the adsorption and photocatalytic performances of modified nanosheet were characterized by the removal of high-concentration methylene blue (MB). When TNS was loaded with a proper amount of Ag2O, the adsorption capacity is enhanced to 2.2 times, with a maximum of 172.4mg/g determined from Langmuir isotherm. The adsorption results also show that a small amount of Ag2O-modified TNS can quickly enrich large amounts of MB molecules onto its surface via adsorption. Furthermore, Ag2O-modified TNS exhibits novel separation efficiency of photogenerated carriers evidenced by photoluminescence measurements, and enhanced photocatalytic activity proved by the degradation of MB. The good reusability of Ag2O-modified TNS implies a potential application for dealing with high-concentration dyes by adsorption–photocatalytic degradation. [Copyright &y& Elsevier]