Ag-doped ZnO nanorods embedded reduced graphene oxide nanocomposite for photo-electrochemical applications.

In this paper, the Ag-doped zinc oxide nanorods embedded reduced graphene oxide (ZnO:Ag/rGO) nanocomposite was synthesized for photocatalytic degradation of methyl orange (MO) in the water. The microstructural results confirmed the successful decoration of Ag-doped ZnO nanorods on rGO matrix. The photocatalytic properties, including photocatalytic degradation, charge transfer kinetics and photocurrent generation, are systematically investigated using electrochemical impedance spectroscopy (EIS), photocurrent transient response (PCTR) and open circuit voltage decay (OCVD). The results of photocatalytic dye degradation measurements indicated that ZnO:Ag/rGO nanocomposite is more effective than pristine ZnO to degrade the MO dye, and the degradation rate reached 40.6% in 30 min. The decomposition of MO with ZnO:Ag/rGO nanostructure followed first-order reaction kinetics with a reaction rate constant (K a) of 0.01746 min-1. The EIS, PCTR and OCVD measurements revealed that the Ag doping and incorporation of rGO could suppress the recombination probability in ZnO by the separation of photo-generated electron-hole pairs, which leads to the enhanced photocurrent generation and photocatalytic activity. The photocurrent density of ZnO:Ag/rGO, ZnO/rGO and pristine ZnO are 206, 121.4 and 88.8 nA cm-2, respectively.

Electrochemical properties of reduced graphene oxide derived through camphor assisted combustion of graphite oxide.

A facile method was demonstrated for the one-step synthesis of reduced graphene oxide (rGO) from graphite oxide (GO) using a camphor assisted combustion (CAC) process. Analysis of samples was carried out using FT-IR, XRD, TGA, Raman, BET, SEM and TEM techniques. The electrochemical properties of the rGO samples derived through the CAC process were determined using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. It has been observed that the specific surface area and porosity of the rGO samples decrease with the increasing concentration of camphor during the CAC synthesis process. Thus, different mass ratios of GO and camphor such as 1 : 12, 1 : 16, and 1 : 20 in the CAC process yield rGO samples having surface areas (SBET) of 313.3, 297.5 and 177.4 m2 g-1. The pore volumes of the respective samples are 0.44, 0.45 and 0.23 cm3 g-1, respectively. The rGO derived using the 1 : 12 mass ratio of GO and camphor (rGO-12C) exhibits a high specific capacitance of 241 F g-1, which is significantly higher than that observed for chemically reduced graphene oxide (rGO-CR), which exhibits a specific capacitance value of only 153 F g-1. The capacitance retention of rGO-12C was found to be 98% even after 1000 galvanostatic charge-discharge (GCD) cycles, suggesting its potential applications in electrochemical energy storage.

Aryl fluoride functionalized graphene oxides for excellent room temperature ammonia sensitivity/selectivity.

Herein, we report the covalent functionalization of graphene oxide (GO) through ''click'' reaction and its applications towards ammonia sensing. This inimitable method of covalent functionalization involves linking GO with azide moiety and click coupling of different derivatives of aryl propargyl ether, which enhances the sensitivity towards ammonia. The functionalized GO were characterized using NMR, XRD, SEM, FT-IR, Raman, UV-Vis, TGA and DSC. Compared to pristine GO, the GO functionalized with Ar samples (GO-Ar) exhibit excellent room temperature ammonia sensing properties with good response/recovery characteristics. It has been observed that 2,3-difluoro and 2,3,4-trifluoro substituted aryl propargyl ether functionalized GO (GO-Ar2 and GO-Ar3) shows superior ammonia sensing with response/recovery of 63%/∼90% and 60%/100%, respectively at 20 ppm. The GO-Ar3 exhibits high sensitivity towards ammonia at 20-100 ppm. Computational studies supports the high sensitivity of GO-Ar towards ammonia due to its high adsorption energy.

Organic semiconductor/graphene oxide composites as a photo-anode for photo-electrochemical applications.

An intimate physical mixture of graphene oxide (GO) and semiconducting organic molecules like bromophenathrene (BrPh) and bromopyrene (BrPy) was prepared by using a ball milling technique. The structural, microstructural, physical and chemical properties of the mixtures (20 wt% of GO) were analyzed by X-ray diffraction, SEM, FT-IR, TGA and TCSPC studies. Furthermore, the electrochemical properties like AC electrical conductivity, transient photocurrent response (PCTR) and open circuit voltage (OCVD) of the samples were analyzed. It has been observed from TCSPC and OCVD measurements that 20 wt% of GO in the semiconductor composite leads to an enhanced life-time of photo-generated charge carriers. The physical mixture composites exhibit a higher photocurrent than pure BrPh and BrPy.