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A facile one-step green synthesis of stable gold nanoparticles (AuNPs) has been described using chloroauric acid (HAuCl 4 ) and the leaf extract of Lantana camara Linn (Verbenaceae family) at room temperature. The leaf extract enriched in various types of plant secondary metabolites is highly efficient for the reduction of chloroaurate ions into metallic gold and stabilizes the synthesized AuNPs without any additional stabilizing or capping agents. Detailed characterizations of the synthesized gold nanoparticles were carried out by surface plasmon resonance spectroscopy, transmission electron microscopy, dynamic light scattering, Zeta potential, X-ray diffraction and Fourier transform-infrared spectroscopy studies. The synthesized AuNPs have been utilized as a catalyst for the sodium borohydride reduction of 4-nitrophenol to 4-aminophenol in water at room temperature under mild reaction condition. The kinetics of the reduction reaction has been studied spectrophotometrically.

The charge transfer effect at the graphene/transition metal interface has been studied extensively during the last few years; however, the experimental results are very poor. In the present work, a Co atom capped with porphyrin is attached on the graphene surface to realize the induced magnetic properties arising due to the charge transfer effect at the interface. Ferromagnetic ordering with fairly large coercivity (516 Oe) is observed as a result of this induced magnetism in graphene due to the presence of a transition metal atom on the graphene surface. Temperature dependent magnetotransport has also been investigated to understand the effect of spin-orbit coupling arising due to the electric field generated at the interface as a result of this charge transfer effect.

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A low-cost, platinum-free electrocatalyst for hydrogen (H 2 ) generation via the water splitting reaction holds great promise to meet the demand of clean and sustainable energy sources. Recent studies are mainly concerned with semiconducting materials like sulfides, selenides, and phosphides of different transition metals as electrocatalysts. Doping of the transition metals within the host matrix is a good strategy to improve the electrocatalytic activity of the host material. However, this activity largely depends on the nature of the dopant metal and its host matrix as well. To exploit this idea, here, in the present work, we have synthesized semiconducting Ag 2 S nanoparticles and successfully doped them with different transition metals like Mn, Fe, Co, and Ni to study their electrocatalytic activity for the hydrogen evolution reaction from neutral water (pH = 7). Among the systems doped with these transition metals, the Ni-doped Ag 2 S (Ni–Ag 2 S) system shows a very low overpotential (50 mV) with high catalytic current in neutral water. The trend in electrocatalytic activity of different transition metals has also been explained. The Ni–Ag 2 S system also shows very good stability in ambient atmosphere over a long period of time and suffers no catalytic degradation in the presence of oxygen. Structural characterizations are carried out using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy to establish the phase purity and morphology of the materials.