Uncovering the Mechanism for the Formation of Copper Thioantimonate (SbV) Nanoparticles and Its Transition to Thioantimonide (SbIII)

Ternary sulfide nanostructures are small band gap materials that combine relatively low toxicity with useful optical properties for several applications, including photovoltaics. A systematic experimental study on the synthesis and mechanism of formation of copper thioantimonates (Cu3SbS4) and thioantimonides (CuSbS2) nanoparticles is presented. Antimony oxide (Sb2O3) was formed in an initial step by hydrolysis with oleylamine. The injection of a sulfur precursor led to the conversion to Cu3SbS4 driven by an excess of sulfur in oleylamine medium and at high temperatures (>200 °C). The sulfur excess was depleted as the reaction progressed, causing the reduction of the antimony(V) of the Cu3SbS4 back to antimony(III). Consequently, the Cu3SbS4 was converted to CuSbS2. In addition, the rate of antimony reduction increased with the reaction temperature. The formation mechanism unveiled here provides important insights toward the synthesis of analogous materials.