Anisotropic manganese antimonide nanoparticle formation by solution–solid–solid growth mechanism: consequence of sodium borohydride addition towards reduced surface oxidation and enhanced magnetic moment

Abstract

A new approach to the solution-phase synthesis of manganese antimonide nanoparticles was developed to reduce competitive oxide formation by exploitation of sodium borohydride (NaBH₄) (0.53–2.64 mmol) as a sacrificial reductant. However, in the presence of near-stoichiometric precursor amounts of manganese carbonyl and triphenyl antimony, the introduction of NaBH₄ results in a different growth mechanism, Solution–Solid–Solid (SSS), leading to tadpole-shaped manganese antimonide nanoparticles with antimony-rich heads and stoichiometric manganese antimonide tails. We hypothesize that a solid antimony-rich manganese antimonide cluster acts as an initiator to tail growth in solution. Notably, the length of the tail correlated with the amount of NaBH₄ used. Interestingly, these anisotropic particles can be transformed progressively into spherical-shaped nanoparticles upon the addition of excess manganese carbonyl. The anisotropic manganese antimonide particles possess saturation magnetizations ca. twenty times higher than that reported for MnSb nanoparticles prepared without NaBH₄, attributed to limitation of oxidation.