Formation of size-tunable CdS rhombic dodecahedra

Abstract

By preparing an aqueous solution of cadmium acetate, thioacetamide (TAA), and nitric acid at 23 to 29 °C, then heating the solution to 110 °C for 40 min, unprecedented {110}-bound CdS rhombic dodecahedra were produced with tunable sizes of 64, 83, 99, 110, and 150 nm. The particles have a pure zinc blende crystal structure. Despite their relatively large dimensions, both the absorption and emission bands of these rhombic dodecahedra red-shift progressively with increasing particle size. Their band gaps decrease steadily from 2.27 to 2.21 eV toward larger rhombic dodecahedra, showing that band gap changes continue to very large CdS nanocrystals. Furthermore, electrical conductivity measurements show that the {110} faces of CdS are barely electrically conductive.