Abstract
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•Stabilization of short-lived intermediate during the reduction of Co2+ by sodium borohydride.•Stoichiometric ratios of reactants are responsible to the formation of intermediate in presence of stabilizers.•Nature of stabilizers have significant impacts on the morphology of cobalt nanoparticles.
Upon addition of sodium borohydride to a solution of cobalt nitrate, a transient species appears within the time of mixing, which is stable for some time ca. 10min. The molar ratios of reactants (Co2+ ions and sodium borohydride), presence of stabilizer, ageing of an aqueous NaBH4 solution, mixing order of stabilizers sodium dodecyl sulfate (SDS), n-hexadecyltrimethylammonium bromide (CTAB), and poly(vinyl) alcohol (PVA) and reactants have immense influence on the stabilization of short-lived transient. Decomposition rate constant of transient have been determined (kobs=0.76, 4.2, 4.9×10−4s−1 for SDS, PVA and no stabilizer). The complex formation constant, KC and difference in absorption coefficients, Δϵ between SDS and Co2+ ions were found to be 2.4×10−2mol−1dm3 and 2298mol−1dm3cm−1, respectively. The characteristics of the Co-nanoparticles were also studied using energy-dispersive spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscope (TEM). EDX spectrum XRD confirmed the presence of an elemental sulphur signal along with cobalt without any peaks of other impurities.