Photocatalytic Activity In Visible Region Research Articles

Density Functional Theory Approach to Evaluate the Structure Of Modified Titania/Graphene Composite and Photooxidation Products of 9-(N,N-Dimethylaminomethyl) Anthracene System

The current work reports the modification of graphene/titania composite by metal and non-metal to improve the photocatalytic activity in visible region. The M-RGO-TiO2-N system was prepared by Hummer’s method followed by hydrothermal technique. On reaction, tertiary amine appended anthracene and its phenyl derivative yielded anthraquinone as the major product with almost 90% yield. Photo-oxidation of phenyl protected derivative of 9-NN-dimethyalaminomethyl anthracene yielded a very stable intermediate, 9-hydroxy 9-phenyl anthrone over a short span of time. All the products were separated by silica column chromatography using 70:30 hexane/DCM as the mobile phase. The separated compounds were characterized by 1HNMR. Theoretical investigations on the structure of the catalytic system and photo oxidation products of anthracene compounds were studied in detail by using Density functional theory calculations. Significant reduction in band gap of titania was observed from 2.84 eV to 1.84 eV after the modification of titania/graphene heterojunction with metal ions. The geometry optimized structures and energy calculations unmistakably confirmed various interactions of titania and graphene via metal ion and feasibility of the photo oxidation reaction, respectively.

SURFACTANT ASSISTED HYDROTHERMAL SYNTHESIS OF ZINC SULFIDE NANOPARTICLES USING SINGLE SOURCE PRECURSORS

Lot of research is being carried out to develop solar cells which are economical with higher efficiencies. Many nanomaterials have been explored to tackle this issue. In this paper we have been used pure ZnS and cobalt doped ZnS nanoparticles which were hydrothermally synthesized from single source precursors using TX-100 as surfactant. The prepared precursors and samples were characterized using FTIR, TGA, XRD and UVVisible. The crystallite size of the nanoparticles calculated from the XRD analysis have been found in the range of 20-25 nm. UV-Visible analysis at room temperature shows absorption peaks in the UV-region. The optical bandgap calculated using Tauc’s plot from the absorption data lies in the region of 3.2-3.5 eV. This study helps in understanding novel performance of Co-ZnS in comparison to pure ZnS nanoparticles for its use in solar cell applications due to increase in photocatalytic activity in visible region.

Effect of Ce on piezo/photocatalytic effects of Ba0.9Ca0.1CexTi1-xO3 ceramics for dye/pharmaceutical waste water treatment

Ba0.9Ca0.1CexTi1-xO3 (x = 0, 0.1, 0.12 and 0.15) ferroelectric ceramics were fabricated via conventional solid-state reaction route. Ba0.9Ca0.1CexTi1-xO3 (BCT-Ce) powder was poled using corona poling. Systematic investigation was carried out for microstructural, photocatalytic and piezocatalysis performance of various compositions of poled and unpoled Ba0.9Ca0.1CexTi1-xO3 ceramics. To assess catalytic activities, rhodamine B (RB) dye, methylene blue (MB) dye and diclofenac (pharmaceutical compounds) were degraded from water under ultrasonication (piezocatalysis) and using 420 nm light (photocatalysis). Photocatalytic activities were improved by almost 100% in poled samples (as compare to the that of observed from unpoled samples) of all the compositions understudy. Incorporation of Ce in Ba0.9Ca0.1TiO3 (BCT) induces photocatalytic activity in visible region along with enhancement in piezocatalytic performance.

A study of light induced surface reactions of sildenafil citrate on hybrid AgCl/Ag nanoparticle dimers by surface enhanced Raman scattering and pulse radiolysis techniques

AgCl/Ag nanoparticle dimers (NPD) are important from photocatalysis point of view as it is reported to show photocatalytic activity in visible region. In this work, AgCl/Ag NPDs were synthesized by controlling the concentration of available chloride ions as well as the capping agent, sildenafil citrate (SC). Transmission electron microscopy (TEM), selected area electron diffraction (SAED) and UV–vis absorption property was used to probe morphology, lattice structure and optical property of as synthesized AgCl/Ag NPDs. SERS spectrum of SC adsorbed on the AgCl/Ag NPD excited at 632 nm, which is energetically closer to the coupled plasmon peak at 605 nm, showed some unexplained vibrational peaks. The above system was probed further by using pulse radiolysis technique and time-dependent density functional theory (TD-DFT) calculations. The results suggest that a direct electron transfer reaction from AgCl/Ag NPD to SC is involved in appearance of anomalous features in SERS spectrum.

Facile and large-scale preparation of N doped TiO2 photocatalyst with high visible light photocatalytic activity

High visible light photocatalytic activity of N-doped TiO2 (N-TiO2) photocatalysts were prepared by facile sol-gel method in large-scale without separation, purification and thermal treatment at high temperature. Ammonium nitrate (AN) was used as nitrogen source and solid substrates, hydrous TiO2 deposited onto the surface of AN micro-particles during the formation of compound gel. AN thermal decomposed and N-TiO2 photocatalysts were obtained by compound dry gel (CDG) calcined at low temperature. N element thermal diffused enter into lattice of TiO2, and the effects of AN evidently facilitated the product transformation from amorphous to anatase. Meanwhile, the doped N element promoted the formation of doping level and its light absorption edge extended to visible region. We systematically research the doping ratio of AN, the different calcined time at low temperature to prepare N-TiO2 with high photocatalytic activity in visible region. As-prepared N-TiO2 photocatalysts exhibited excellent photocatalytic activity under the illumination of visible light, and the photodegradation reaction rate constant was approximately 6 times higher than pure TiO2 samples.

Synthesis, characterization and photocatalytic activity of inexpensive and non-toxic Fe2O3−Fe3O4 nano-composites supported by montmorillonite and modified by graphene

Abstract Inexpensive and non-toxic novel Fe 2 O 3 −Fe 3 O 4 nano-composites supported by montmorillonite and modified by graphene were successfully synthesized using the liquid phase reduction hydrothermal method. The presence of montmorillonite reduced sizes of iron crystals, and the loading of graphene enhanced the separation efficiency and electron-conductivity of photo-induced electron-hole pairs. The methyl orange degradation experiment was made to investigate the photocatalysis performance of pure Fe 2 O 3 −Fe 3 O 4 , Fe 2 O 3 −Fe 3 O 4 −Montmorillonite and Fe 2 O 3 −Fe 3 O 4 −Montmorillonite−Graphene at the same condition. The absorption of nano-composites was a slight blue-shifted with a decreasing crystallite size of iron nano-particles, while it was clearly shifted toward longer wavelengths upon the modification using graphene. Fe 2 O 3 −Fe 3 O 4 −Montmorillonite−Graphene exhibited the excellent optical response and photocatalytic activity in visible region: the degradation rate of methyl orange reached 2.77 times faster than that of Fe 2 O 3 −Fe 3 O 4 and 1.61 times faster than that of Fe 2 O 3 −Fe 3 O 4 −Montmorillonite within 30 min irradiation. Results implied that applications of montmorillonite helped to prevent agglomeration of iron nano-particles, and graphene helped to reduce the charge recombination rate, further validated an enhanced photocatalytic performance of Fe 2 O 3 −Fe 3 O 4 −Montmorillonite−Graphene superiorly. The current study shed new light on synergetic effects of the inexpensive and non-toxic iron oxide nano-photocatalyst with visible-light responsible and magnetic-active compositions, agglomeration-preventive nano-structures by montmorillonite and enhanced electron separation by graphene.

Enhanced photoelectrochemical response of reduced-graphene oxide/Zn1−xAgxO nanocomposite in visible-light region

Graphene based nanocomposites have the potential to work as efficiently, multifunctional materials for energy conversion & storage. These composites may exhibit better photocatalytic properties by the improvement of their electronic and structural properties than pure photocatalysts. In the present work, reduced graphene oxide (rGO) & ZnO nanocomposite with 0–5 atom% Ag doping was prepared by electrodeposition method and characterized by XRD, Raman spectroscopy, FE-SEM, EDX, UV–Vis spectroscopy and final photoelectrochemical activity was assessed under 1.5 AM solar simulator in 1 M NaOH as electrolyte. Significant changes in the Raman spectrum for the nanocomposite suggest the possible electronic interaction between rGO and ZnO nanocomposite and its successful fabrication, which improves the charge separation and enhanced photoelectrochemical activity in the nanocomposite. We find a red-shift of 0.35 eV in the UV–vis spectrum and therefore an enhanced photoelectrochemical activity in the visible range on Ag doping in rGO/ZnO nanocomposite. Nanocomposite with 1 atom% Ag doping showed the highest photocurrent density of 2.48 mA/cm 2 at 0.8 V vs Ag/AgCl over other samples, which was almost five times higher than that for undoped rGO/ZnO composite. Calculated Flat-band potential and donor densities using Mott–Schottky data also supported the better photoelectrochemical response for Ag doping in nanocomposite. • Graphene based nanocomposite was successfully fabricated by electrodeposition. • Nanocomposite exhibited good photocatalytic activity in visible region with Ag-doping. • Significant changes in Raman suggest possible electronic interaction in nanocomposite. • Nanocomposite with 1 atom% Ag doping exhibited best photocurrent of 2.48 mA/cm 2 .

Engineering the metathesis and oxidation-reduction reaction in solid state at room temperature for nanosynthesis.

It is a long-standing goal to explore convenient synthesis methodology for functional materials. Recently, several multiple-step approaches have been designed for photocatalysts AgnX@Ag (X = Cl−, PO43−, etc.), mainly containing the ion-exchange (metathesis) reaction followed by photoreduction in solution. But they were obsessed by complicated process, the uncontrollability of composition and larger sizes of Ag particles. Here we show a general solid-state route for the synthesis of AgnX@Ag catalysts with hierarchical structures. Due to strong surface plasmon resonance of silver nanoparticles with broad shape and size, the AgnX@Ag showed high photocatalytic activity in visible region. Especially, the composition of AgnX@Ag composites could be accurately controlled by regulating the feed ratio of (NH2OH)2·H2SO4 to anions, by which the performance were easily optimized. Results demonstrate that the metathesis and oxidation-reduction reactions can be performed in solid state at room temperature for nanosynthesis, greatly reducing the time/energy consumption and pollution.

Remarkably enhanced photocatalytic activity by nickel nanoparticle deposition on sulfur-doped titanium dioxide thin film

To enhance the photocatalytic performance of titanium dioxide, the structures of both bulk and surface were modified. Doping of sulfur atoms to be substituted for lattice oxygen atoms of titanium dioxide was carried out to extend the light absorption by atmosphere-controlled pulsed laser deposition, which allows direct preparation of impurity-included thin film such as sulfur-doped titanium dioxide. On the other hand, to enhance the surface catalytic reaction, nickel nanoparticles were deposited at the thin film substrate by chemical vapor reductive deposition method, which is a novel preparation technique of metallic nanoparticles on the substrate surface. Obtained sulfur-doped titanium dioxide was found to possess sensitivity to visible light with the wavelength up to 550nm, indicating the photocatalytic activity in visible region. Sulfur doping induced the dye degradation activity under visible light irradiation. When nickel nanoparticles were deposited, a remarkable enhancement of the hydrogen evolution activity through ethanol decomposition of more than 20 times as much as unmodified titanium dioxide thin film was accomplished. In addition, the stability of sulfur atom doped into titanium dioxide structure was investigated.