Molecular clusters of binary and ternary mercury chalcogenides: Colloidal synthesis, characterization, and optical spectra

A series of binary (HgSe) and ternary (HgSe1-xSx) mercury chalcogenide clusters are synthesized utilizing a colloidal technique, involving the phase separation of metal and chalcogen precursors in the presence of strong Hg(II) coordinating ligands. The clusters vary in size between 2 and 3 nm and possess the cubic zinc blende structure of the bulk. Energy-dispersive X-ray measurements show that the composition of the ternary material can be varied throughout the entire composition range from HgS to HgSe. In all cases, the linear absorption of these binary and ternary species is narrow with well-resolved transitions at both the band edge and at higher energies. Complementary band edge emission is also observed with no apparent deep trap emission. Size- and composition (x)-dependent optical properties of these clusters are investigated using photoluminescence (PL) and photoluminescence excitation (PLE) spectra. In the case of HgSe clusters, the size-dependent behavior of up to four excited states is followed. For HgSe1-xSx clusters, where x varies from 0 to 1, a size/composition-dependent progression of up to five excited states is observed.