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Rapid and efficient green synthesis of reduced graphene oxide (rGO) material has been carried out (by the reduction of graphite oxide (GO)) with tulasi (Holy Basil) green tea extract followed by microwave irradiation technique in 1 min. As prepared rGO material shows outstanding multifunctional performance as electrodes for supercapacitors and efficient adsorption of toxic organic dyes from aqueous solutions. The electrochemical performance of rGO electrode for supercapacitor showed that, it exhibits high specific capacitance of 164.6 F g −1 at a current density of 1 A g −1 under aqueous 1 M H 2 SO 4 electrolyte solution, good rate capability (59.6% retention when the current density increases from 1 to 10 A g−1). After 3000 cycles, the attenuation of the specific capacitance is less than 5%, indicating excellent electrochemical stability. Moreover, the maximum adsorption capacity of rGO reaches 416.7 mg/g for malachite green dyes at equilibrium under aqueous solutions. [ABSTRACT FROM AUTHOR]

Approximately 25 million tons of stems of Cajanus cajan are available as residue after harvesting the seeds. Currently, most of the stems are burnt or buried and do not have any major applications. The exploitation such unconventional agricultural waste to get novel bio-char and its chemical activation for efficient construction of symmetric supercapacitor device (SSD) is important from economic and conservational outlook. Herein, we demonstrate for the first-time utilization of stems of Cajanus cajan for the fabrication of SSD. Initially, the stems of Cajanus cajan were carbonized (CC) and activated using KOH at two different temperatures 700 & 800 °C (CC-1 & CC-2) in N 2 atmosphere. All the carbon materials were characterized by powder X-ray diffraction (P-XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analytical techniques. CC-1 & CC-2 exhibited almost the same electrochemical performances were found to be higher than CC in the presence of 1 M KOH solution in a three-electrode system. A symmetric coin cell was fabricated using CC-2, exhibited specific capacitance (Cs), energy density (ED) & power density (PD) of 126 F/g, 30.6 Wh/kg & 1.1 kW/kg respectively. Further, the device exhibited 50,000 cycle stability at high current densities (25 & 50 A/g) with 100% coulombic efficiency. The device was able to power four red colored LEDs connected in series for up to 8 min without any change in luminescence hence showing high potential to be used for supercapacitor applications. [Display omitted] • Bio-waste Cajanus cajan stems derived activated carbon was successfully used in SCs. • Designed coin cell using CC-2 exhibited ED 30.6 Wh/kg & PD 1.1 kW/kg. • A coin cell exhibited 50,000 cycles stability with 100% columbic efficiency. • Two coin cells connected in series were used to power four red colored LEDs. [ABSTRACT FROM AUTHOR]

• We have succefully synthesized SnO 2 -WO 3 nanocomposite using lemon juice as a fuel (reducing agent). • Synthesized SnO 2 -WO 3 nanocomposite was characterized using FTIR, PXRD, SEM, and TEM analytical methods. • SnO 2 -WO 3 nanocomposite shows good photocatalytic activity for Methylene Blue dye. • In addition to this, SnO 2 -WO 3 composite were used for the detection of H 2 O 2 using electrochemical techniques. The SnO 2 -WO 3 nanocomposite was synthesized through green combustion method using Citrus Limon (lemon Juice) as a fuel. Powder X-ray Diffraction (PXRD) pattern confirms the biphasic composite having (i) tetragonal SnO 2 (JCPDS No: 041-1445) and (ii) monoclinic WO 3 (JCPDS No: 033-1387) phases. Fourier Transform Infra-red (FTIR) spectrum shows the vibrational peaks at 598 cm-1 for Sn-O-Sn and 711 cm-1 and 807 cm-1 for W-O bonds, respectively. A strong absorption band was observed at 268 nm, which is corresponding to the bandgap of 4.09 eV. The SnO 2 -WO 3 nanocomposite shows agglomerated, irregular shape of nanoparticles. The average particle size was found to be 75 nm. SnO 2 -WO 3 nanocomposite shows marvellous photocatalytic activity against methylene blue (MB) dye degradation in all parameters. Also, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were employed to analyze the electrochemical properties of prepared samples by using modified carbon paste electrodes for the determination of hydrogen peroxide (H 2 O 2). [ABSTRACT FROM AUTHOR]

• Synthesized rGO using Indian gooseberry (Amla) extract as green reducing agent. • XPS, Raman, FTIR and UV–vis spectroscopy have confirmed the reduction of GO to rGO. • Demonstrated application of rGO in ammonia gas detection using chemiresistor. Graphene preparation from reduction of graphene oxide (GO) which is known as reduced graphene oxide (rGO) is considered as one of the promising methods for the development of graphene-based devices on a large scale at low-cost. In the present work, rGO has been successfully prepared using Indian gooseberry (Amla) extract, a green reducing agent, and its sensitivity for ammonia gas molecules has been studied using chemiresistor configuration. About 5 % sensitivity was observed for 3 ppm concentration of ammonia gas. Raman and X-ray photoelectron spectroscopy (XPS) spectra have confirmed the formation of rGO. Fourier transform infrared spectroscopy (FTIR), ultraviolet visible (UV–vis) spectroscopy and electron microscopy have been adopted for evaluating the quality of synthesized rGO. In addition, the green synthesized rGO has been evaluated for the device suitability by comparing its quality and performance with rGO synthesized using chemical reducing agent (hydrazine hydrate). [ABSTRACT FROM AUTHOR]