Browsing by Author "Akhoury Sudhir Kumar Sinha"

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Comparative in vitro antimicrobial and phytochemical evaluation of methanolic extract of root, stem and leaf of Jatropha curcas linn
(Pharmacognosy Network Worldwide, 2012) Amit Kumar Sharma; Mayank Gangwar; Ragini Tilak; Gopal Nath; Akhoury Sudhir Kumar Sinha; Yamini Bhusan Tripathi; Dharmendra Kumar
Background: Earlier researchers have reported antibacterial activity of different specific parts, but none of the reports show the comparative microbial and phytochemical studies of root, stem and leaf extract. Objective: To compare and investigate antimicrobial, qualitative phytochemical studies, phenol, flavonoid and TLC analysis of root, stem bark, leaf extracts of Jatropha curcas Linn family Euphorbiaceae. Methods: The dried plant powder was subjected to Soxhlet extraction with methanol. These solvent extracts were subjected to a preliminary phytochemical screening to detect the different chemical principles present viz., carbohydrates, proteins, amino acids, steroids, glycosides, alkaloids, flavonoids, tannins and phenolic compounds, fixed oils. Antimicrobial activity was evaluated by disc diffusion method and minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum fungicidal concentration (MFC) was calculated by micro dilution method. Thin layer chromatography was also performed using solvent system chloroform, benzene, hexane, and ethyl acetate for the analysis of a number of constituents in the plant extract. The content of the total phenolics in the extract was determined spectrometrically according to the Folin-Ciocalteu procedure and calculated as catechol equivalent. The content of total flavonoids in the extract was determined and calculated as quercetin equivalent. Result: These extracts showed antibacterial, antifungal activities against gram-positive and gramnegative bacteria with varying magnitudes. The phytochemical analysis showed the presence of alkaloid, saponin, tanins, terpenoids, steroids, glycosides, phenols and flavonoids. Maximum phenolic content (38.8) was found in leaf extract and flavonoid content (18.14) in latex of plant. Discussion: It is concluded that the antimicrobial activity showed by the plant was due to the presence of these phytochemicals. Further studies are highly needed for drug development.
Copper-iron-molybdenum mixed oxides as efficient oxygen evolution electrocatalysts
(Royal Society of Chemistry, 2014) Venkata Kali Vara Prasad Srirapu; Chandra Shekhar Sharma; Rahul Awasthi; Ravindra Nath Singh; Akhoury Sudhir Kumar Sinha
Ternary Cu, Fe and Mo mixed oxides having a nominal compositional formula, CuxFe2-x(MoO4)3 (0 ≤ x ≤ 1.5), have been prepared by a co-precipitation method at pH ≈ 2 and characterized by FT-IR, XRD, XPS, TEM and anodic polarization techniques for use as electrocatalysts for the oxygen evolution reaction (OER) in alkaline solutions. The crystallites of oxides with x ≤ 1 have the monoclinic crystal structure. The OER study shows that replacement of Fe in the Fe2(MoO 4)3 matrix by 0.25-1.0 mol Cu increases the apparent electrocatalytic activity. However, 1.5 mol Cu-addition is detrimental to the OER activity. At E = 1.51 V (vs. RHE) in 1 M KOH, the catalytic activity of the oxide with x = 1 was approximately 50 times the activity of the base oxide (i.e. Fe2(MoO4)3). The Tafel slope of oxides with 0.25 ≤ x ≤ 1.5 ranged between 31 and 37 mV. The reaction order of OH - concentration was nearly unity for oxides with x = 0.25 and 1.5 and it was ∼2 for oxides with x = 0.5, 0.75, and 1.0. Suitable reaction mechanisms consistent with the electrode kinetic parameters have also been proposed. This journal is © the Partner Organisations 2014.
Correction: Enhanced activity and chlorine protection in prolonged seawater electrolysis using MoS2/sulfonated reduced graphene oxide (Sustainable Energy and Fuels (2025) 9 (4300-4319) DOI: 10.1039/D5SE00541H)
(Royal Society of Chemistry, 2025) Prerna Tripathi; Renna Shakir; Amit Kumar Verma; Jeyakumar Karthikeyan; Biswajit Ray; Akhoury Sudhir Kumar Sinha; Shikha K. Singh
The authors regret that the details of the affiliations were not correct in the original manuscript. The corrected affiliations for this paper are as shown herein. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © 2025 The Royal Society of Chemistry.
Enhanced activity and chlorine protection in prolonged seawater electrolysis using MoS2/sulfonated reduced graphene oxide
(Royal Society of Chemistry, 2025) Prerna Tripathi; Renna Shakir; Amit Kumar Verma; Jeyakumar Karthikeyan; Biswajit Ray; Akhoury Sudhir Kumar Sinha; Shikha K. Singh
Electrolyzer technology necessitates the use of seawater instead of freshwater to achieve a comprehensive supply of clean and economical energy. However, the tendency of chloride ions (Cl−) to significantly erode the metal surface is a major challenge during seawater electrolysis. Therefore, designing an electrode that is resistant to chloride ions is of great importance to develop an efficient seawater electrolyser. In this work, we present a double layer anode consisting of a molybdenum sulfide electrocatalyst uniformly deposited over sulfonated graphene sheets coated over an Ni foam. The developed electrode (GNiMoOS) helps selectively convert H2O into H2 and O2 rather than chloride (Cl−) ions into ClO− in a seawater environment by resisting corrosion due to the Cl− ions in seawater. The chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) provides solid evidence that the GNiMoOS electrocatalyst blocks the chloride oxidation reaction owing to its distinct resistance to Cl−. In addition, density functional theory (DFT) calculations clearly validated the preference of sulfonic moieties towards OH− compared with Cl− ions, confirming the chlorine repelling properties of the GNiMoOS electrode. The successful in situ functionalisation of sulfonic moieties into the reduced graphene oxide (RGO) skeleton with simultaneous development of flower-like MoS2 was well confirmed using XPS, Raman, SEM, TEM, and FT-IR techniques. GNiMoOS delivered an impressive current density of 100 mA cm−2 for OER and HER at room temperature, requiring remarkably low overpotentials of just 180 mV and 201 mV, respectively. Industrial faradaic current densities (400-600 mA cm−2) were reported with the active electrode at combined overpotentials of ≤600 mV at room temperature. The unique morphology of MoS2 provides more active sites for the HER/OER, while sulfonated functional groups over graphene impart much-needed anticorrosion properties to the system. Moreover, the electrical coupling between MoS2 and RGO can make the electron transfer to RGO easier. Therefore, the synergistic interactions among MoS2, SO3H and RGO lead to improved catalytic activity and prolonged stability. © 2025 The Royal Society of Chemistry.
Graphene-cobaltite-Pd hybrid materials for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cells
(2013) Chandra Shekhar Sharma; Rahul Awasthi; Ravindra Nath Singh; Akhoury Sudhir Kumar Sinha
Hybrid materials comprising of Pd, MCo2O4 (where M = Mn, Co or Ni) and graphene have been prepared for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cells. Structural and electrochemical characterizations were carried out using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, chronoamperometry and cyclic, CO stripping, and linear sweep voltammetries. The study revealed that all the three hybrid materials are active for both methanol oxidation (MOR) and oxygen reduction (ORR) reactions in 1 M KOH. However, the Pd-MnCo2O4/GNS hybrid electrode exhibited the greatest MOR and ORR activities. This active hybrid electrode has also outstanding stability under both MOR and ORR conditions, while Pt- and other Pd-based catalysts undergo degradation under similar experimental conditions. The Pd-MnCo 2O4/GNS hybrid catalyst exhibited superior ORR activity and stability compared to even Pt in alkaline solutions. © 2013 the Owner Societies.
Graphene-Manganite-Pd Hybrids as Highly Active and Stable Electrocatalysts for Methanol Oxidation and Oxygen Reduction
(Elsevier Ltd, 2014) Chandra Shekhar Sharma; Rahul Awasthi; Ravindra Nath Singh; Akhoury Sudhir Kumar Sinha
Hybrids of graphene nanosheets (GNSs) with Pd and MMn2O 4 (M = Mn & Co) have been prepared and investigated as electrocatalysts for the methanol oxidation (MOR) and oxygen reduction (ORR) reactions in 1 M KOH at 25 °C. Results show that incorporation of Mn3O4 (or CoMn2O4) into 40wt%Pd/GNS increases the electrocatalytic activity toward both the reactions (MOR and ORR) greatly; the observed enhancement in the activity being much higher with CoMn2O4 addition. It is observed that at an anodic potential, E = 0.610 V vs RHE, 8wt% CoMn2O4 addition improves the methanol oxidation current density of 40wt%Pd/GNS by more than 3 times. Similarly, at E = 0.90 V vs RHE, 5wt% CoMn2O4 addition improves the ORR activity of 40wt%Pd/GNS nearly two times. The stability of the active hybrid electrode is also found to be outstanding under both MOR and ORR conditions. Similar stabilities have not been found with other fuel cell catalysts. In a chronoamperometry experiment at E = 0.626 V vs RHE, the methanol oxidation current observed on Pd-8%CoMn2O 4/GNS at 2 min decreased by only ∼5% at 120 min. © 2014 Published by Elsevier Ltd.