Assimilating green chemistry principles in nanotechnology
is a
developing area of nanoscience research nowadays. Thus, there is a
growing demand to develop environmentally friendly and sustainable
methods for the synthesis of nanoparticles that utilize nontoxic chemicals,
environmentally benign solvents, and renewable materials to avoid
their adverse effects. A simple, economic, and environmentally benign
experimental route to synthesize gold nanoparticles using tea leaves
in an aqueous media at room temperature is described with a goal to
introduce chemistry students to the concept of green chemistry as
well as nanotechnology. The single-step method circumvents the use
of surfactant, capping agent, or template and follows several principles
of green chemistry. The experiment can be conducted in a typical laboratory
session and is suitable for incorporation into the undergraduate introductory
chemistry laboratory curriculum and constitutes an influential example
of green chemistry in action.
Cubic spinel Co3O4 nanoparticles with spherical (0D) and hexagonal platelet (2D) morphologies were synthesized using a simple solvothermal method by tuning the reaction time. XRD and HRTEM analyses revealed pure phase with growth of Co3O4 particles along [111] and [110] directions. UV-vis studies showed two clear optical absorption peaks corresponding to two optical band gaps in the range of 400-500 nm and 700-800 nm, respectively, related to the ligand to metal charge transfer events (O(2-) → Co(2+,3+)). Under the electrochemical study in two electrode assembly system (Co3O4/KOH/Co3O4) without adding any large area support or a conductive filler, the hexagonal platelet Co3O4 particles exhibited comparatively better characteristics with high specific capacitance (476 F g(-1)), energy density 42.3 Wh kg(-1) and power density 1.56 kW kg(-1) at current density of 0.5 Ag(-1), that suited for potential applications in supercapacitors. The observed better electrochemical properties of the nanoporous Co3O4 particles is attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.
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