Efficient Capping of Growing Gold Nanoparticles by Porphyrin Having Two Disulfide Straps over One Face

Abstract

Abstract Two types of tetrathiolated surface passivants were synthesized in order to explore the effect of S-functional groups (disulfide vs. S-thioester) to control the size of gold nanoparticles prepared by a simple one-pot reduction of tetrachloroaurate with sodium tetrahydroborate. Both the passivants have four thiolated arms in the same direction perpendicular to a porphyrin plane, and produced small porphyrin-coated gold nanoparticles 2 to 4 nm in size by one-pot reduction of AuIII ions at S/Au from 1 to 16. The constancy in particle size at S/Au ratio less than 4 was greater with use of tetradentate disulfide passivant compared with use of tetradentate S-thioester ligand, which should be attributed to faster adsorption of disulfide groups with gold than that of S-thioester groups. The results described here suggest that passivants having multivalent disulfide bonds should be promising candidates for constructing monolayer-protected gold nanoparticles of well-defined size.