Kefayat Ullah

The characteristic study and sonocatalytic performance of CdSe–graphene as catalyst in the degradation of azo dyes in aqueous solution under dark conditions

The sonocatalytic degradation of azo dyes; methyl orange (MO) and rhodamine B (RhB) were studied catalyzed by cadmium selenide (CdSe)-graphene in dark ambiance. The CdSe-graphene composites were prepared by simple hydrothermal method. The characterizations of composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), specific surface area (BET) and with energy dispersive X-ray (EDX). The UV-spectroscopic analysis of the dyes was done by measuring the change in absorbance. The degradation of the organic dyes was calculated based on the decrease in concentration of the dyes with respect to regular time intervals. The rate coefficients for the sonocatalytic process were successfully established and the reusability tests were done to test the stability of the used catalysts.

Synergistic effect of PtSe2 and graphene sheets supported by TiO2 as cocatalysts synthesized via microwave techniques for improved photocatalytic activity

Here we report a new composite material consisting of TiO2 nanoparticles grown in the presence of a layered PtSe2/graphene hybrid as a high-performance photocatalytic material. The heterogeneous PtSe2–graphene/TiO2 nanocomposites were successfully synthesized through a facile and fast microwave-assisted method. The prepared composites were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), Raman spectroscopic analysis, X-ray photoelectron spectroscopy (XPS), and UV-vis absorbance spectra and UV-vis diffuse reflectance spectra (DRS) analyses were obtained. The catalytic behavior was investigated through the decomposition of rhodamine B (Rh. B) as a standard dye and Texbrite MST-L as an industrial dye. This extraordinary photocatalytic activity arises from the positive synergetic effect between the PtSe2 and graphene components in this heterogeneous photocatalyst. In this study the graphene behaves as an electron transfer agent, collector, contributor and a source of active adsorption sites. The optical properties were also observed to be affected by the different weight% of graphene in the composites by observing their respective band gaps from DRS spectra.

Optical and photocatalytic properties of novel heterogeneous PtSe2-graphene/TiO2 nanocomposites synthesized via ultrasonic assisted techniques.

Novel material PtSe2-graphene/TiO2 nanocomposites were successfully synthesized through a facile ultrasonic assisted method. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX),transmission electron microscopy (TEM), Raman spectroscopic analysis, UV-vis absorbance spectra and UV-vis diffuse reflectance spectra (DRS) analysis were obtained. The catalytic behavior was investigated through the decomposition of rhodamine B (Rh.B) as a standard dye. Enhanced photocatalytic activities were observed by increasing the weight% of graphene in the PtSe2-graphene/TiO2 nanocomposites. We observed that the coupling of TiO2 with PtSe2-graphene alter the optical properties by observing a precise band gap in the visible range.

Fullerene modification CdSe/TiO2 and modification of photocatalytic activity under visible light.

CdSe, CdSe-TiO2, and CdSe-C60/TiO2 composites were prepared using sol–gel method, and their photocatalytic activity was evaluated by measuring the degradation of rhodamine B solutions under visible light. The surface area, surface structure, crystal phase, and elemental identification of these composites were characterized by nitrogen adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and UV-visible (vis) absorption spectrophotometry. XRD showed that the CdSe-C60/TiO2 composite contained a typical single and clear anatase phase. SEM of the CdSe-C60/TiO2 composites revealed a homogenous composition in the particles. EDX revealed the presence of C and Ti with strong Cd and Se peaks in the CdSe-C60/TiO2 composite. The degradation of dye was determined by UV–vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase in the photoabsorption effect by fullerene and the cooperative effect of the CdSe. The repeatability of photocatalytic activity was also tested in order to investigate the stability of C60 and CdS-C60/TiO2 composites.

Microwave synthesis of a CoSe2/graphene–TiO2 heterostructure for improved hydrogen evolution from aqueous solutions in the presence of sacrificial agents

A heterogeneous material consisting of a tube type TiO2 was grown in the presence of a CoSe2/graphene hybrid, as a high-performance photocatalyst material, through a fast microwave-assisted technique. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopic analysis, UV-vis absorbance spectra and UV-vis diffuse reflectance spectra (DRS) analysis. The hydrogen evolution rate for ternary composites was found to be markedly high compared to bare TiO2 and binary CoSe2/graphene composites. This extraordinary photocatalytic activity for hydrogen evolution arises from the positive synergistic effect between the CoSe2 and graphene components in our heterogeneous system. The optical properties were also found to be affected by the different weight% of graphene in the composites by observing their respective band gaps from the DRS spectra.

Rhodamine B degradation and reactive oxygen species generation by a ZnSe-graphene/TiO2 sonocatalyst

Abstract Nanostructured ZnSe-graphene/TiO 2 was synthesized by a hydrothermal-assisted approach. ZnSe-graphene/TiO 2 exhibited favorable adsorption of rhodamine B, a wide wavelength absorption range, and efficient charge separation. Reactive oxygen species were generated by the oxidation of 1,5-diphenyl carbazide to 1,5-diphenyl carbazone. The sonocatalytic reaction mechanism was proposed. These findings potentially broaden the applications of sonocatalytic technologies.

Synthesis and characterization of novel PtSe2/graphene nanocomposites and its visible light driven catalytic properties

In this study, we report a novel PtSe2/graphene nanocomposite by facile ultrasonic-assisted techniques. The “as-prepared” nanocomposites were further characterized by various techniques such as X-ray diffraction, scanning electron microscopy with an energy dispersive X-ray analysis, transmission electron microscopy, UV–Vis absorbance spectra analysis, diffuse reflectance analysis, and Raman spectroscopic analysis. The photocatalytic activities of the composites were investigated by the degradation of rhudamine B and methylene blue as a standard dyes. The photodegradation rates of organic dyes by the nanocomposites are found to be markedly high. This study suggests that the as-prepared PtSe2/graphene composite can be utilized as highly efficient photocatalyst materials that employed visible light as an energy source.

Enhanced Visible Light Photocatalytic Activity of Ag2S-graphene/TiO2 Nanocomposites Made by Sonochemical Synthesis

Ag2S‐graphene/TiO2 composites were synthesized by a facile sonochemical method. The products were characterized by X‐ray diffraction, scanning electron microscopy, energy dispersive X‐ray spectroscopy, transmission electron microscopy, and UV‐Vis diffuse reflectance spectrophotometry. During the synthesis reaction, the reduction of graphene oxide and loading of Ag2S and TiO2 particles were achieved. The Ag2S‐graphene/TiO2 composites possessed a large adsorption capacity for dyes, an extended light absorption range, and efficient charge separation properties. Hence, in the photodegradation of rhodamine B, a significant enhancement in the reaction rate was observed with the Ag2S‐graphene/TiO2 composites as compared to pure TiO2. The generation of reactive oxygen species was detected by the oxidation of 1,5‐diphenyl carbazide to 1,5‐diphenyl carbazone. The high activity was attributed to the synergetic effects of high charge mobility and the red shift in the absorption edge of the Ag2S‐graphene/TiO2 composites.

Degradation of Organic Dyes by CdSe Decorated Graphene Nanocomposite in Dark Ambiance

Cadmium selenide (CdSe)-graphene composite materials were synthesized via a facile hydrothermal method and the intriguing catalytic activity of the composites was investigated using organic dyes in complete absence of irradiation source (UV or visible light). The catalytic activity of CdSe-graphene composites was measured using methyl orange (MO) and rhodamine B (Rh.B) dye solutions. The characterizations of composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and with energy dispersive X-ray (EDX). The catalytic degradation was measured by analyzing the decrease in absorbance spectra in UV-Vis spectroscopy. The degradation of the organic dyes in absence of any irradiation was illustrated by the degradation property of CdSe and charge mobility. The catalytic activity after repeated use of the composites was also tested in order to investigate the stability of CdSe-graphene composites.

Detection of Oxygen Species Generated in the Presence of CNT by Loading ZnS

ZnS-CNT nanocomposites were synthesized using simple cheap and less toxic ZnCl2 as the zinc (II) precursor. The prepared nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectra. XRD and TEM results indicate that the prepared product is ZnS nanoparticles and has a grain size of 30 nm in diameter. DRS show that ZnS-CNT possesses the absorption profile across the whole visible-light region. The generation of reactive oxygen species were detected through the oxidation reaction from 1,5-diphenyl carbazide to 1,5-diphenyl carbazone. It is found that the photocurrent density and the photocatalytic effect increase in the case with the modified ZnS. Excellent catalytic degradation of methylene blue solution was observed using the ZnS-CNT composites under visible light irradiation. It is proposed that both the strong visible-light absorption and the multiple exciton excitations contribute to the high visible-light photocatalytic activity.