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Synthesis of reduced graphene oxide (RGO) from graphite oxide (GO) usually involves the use of some harmful reducing agents. Here, we report a simple approach for the reduction of GO at room temperature using a mixture of potassium iodide and hydrochloric acid. The reduction of GO involves (a) iodide mediated epoxide ring-opening, resulting in hydroxyl groups and dehydration to the corresponding olefins, (b) hydroxyl group substitution by iodide ions, and (c) elimination of iodide ions on the surface. The as-synthesized RGO has an electrical conductivity of 1251 S m À1 and an excellent electrocatalytic activity. The electrocatalytic activity of RGO towards the electrochemical reduction of oxygen and the oxidation of hydrazine was investigated. The RGO-based electrode showed pronounced electrocatalytic activity towards the reduction of oxygen and the oxidation of hydrazine in 0.1 M KOH. At alkaline pH, the reduction of oxygen and oxidation of hydrazine were observed at À0.35 and 0.5 V, respectively. In comparison with the bare glassy carbon (GC) electrode, a spectacular decrease in the overpotential and considerable increase in the oxidation peak current for hydrazine were observed on the RGO-based electrode without using any redox mediator. The RGO-based platform is highly sensitive towards the electrochemical oxidation of hydrazine and reproducible results were obtained. Moreover, the RGO-based electrode showed excellent operational and long time storage stabilities. The sensitivity of the electrode was calculated to be 0.137 AE 0.02 mA mM À1 .

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The present study reports the usefulness of ascorbic acid for reducing lenticels browning (LB) in mango, which impairs the cosmetic appeal and thereby the export. Postharvest dip treatment of ascorbic acid at different concentrations (100, 150 and 200 ppm) was given to four varieties of mango (Indian-'Dashehari', 'Langra'; Exotic-'Sensation', 'Eldon'). After treatment, fruits were stored at ambient conditions (35 ± 4°C and 65 ± 5 % RH) for 10 days. At the end of storage period, observations were recorded on several parameters. Our results revealed that fruits of 'Langra' mango exhibited 100 % LB, followed by 'Dashehari' (52.8 %), 'Sensation' (42.9 %) and 'Eldon' (38.3 %). All concentrations of ascorbic acid reduced the LB to greater extent and improved the cosmetic appeal of fruits of all the varieties significantly over untreated fruits but the best results were obtained with 200 ppm concentration for LB (4.8, 1.6, 3.7, 3.2 %, respectively) and other attributes, non-significantly followed by 150 ppm concentration. All concentrations of ascorbic also reduced the activities of polyphenol oxidase, peroxidase and lipoxigenase enzymes, and also reduced respiration rate and ethylene evolution rate but without impairing eating quality attributes (soluble solids concentrates and total carotenoids). It can be concluded that postharvest dip application of ascorbic acid at 150 ppm reduced LB and improve face value without impairing fruit quality.

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