Microwave assisted greener synthesis of nickel nanoparticles using sodium hypophosphite

Nickel nanoparticle (NiNP) was synthesized by reduction of less toxic nickel acetate tetrahydrate (Ni(CH3CO2)2·4H2O) precursor, using sodium hypophosphite monohydrate (NaPH2O2·H2O) under microwave irradiation. By varying the molar ratio of [Ni+ 2]/[NaPH2O2]/[NaOH], NiNP of 3.8 to 7.1 nm was obtained. Increasing NaOH concentration resulted in morphological change from isolated spherical particles (7.2 ± 1.5 nm) to agglomerated nano flowers (72 ± 14 nm). Phase analysis and interplanar spacing measurements confirmed the particles as fcc-Ni. Quantitative analysis showed the presence of P and O due to HPO2− radical in reaction product. Addition of small amounts of polyvinylpyrolidone (PVP) or cetyltrimethylammonium bromide (CTAB) resulted in slight increase in particle size.

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► NiNP was synthesized using a safer reducing agent NaPH2O2.
► Increasing [NaOH], resulted in morphological change and agglomeration.
► Varying [Ni+ 2]:[NaPH2O2]:[NaOH] ratio resulted in NiNP of 3.9 to 7.2 nm.
► Addition of stabilizing agent did not yield any better size reduction.