Phase-selective synthesis of bornite nanoparticles

Abstract

Nanoparticles of the copper iron sulfide phase bornite (ideally Cu₅FeS₄) have been synthesized phase selectively. Either the low or high bornite phase can be obtained through alteration of reactant ratios or reaction temperature, revealing a phase-selectivity that results from distinct rates of formation. The phase, shape, size, and composition of these novel nanomaterials are characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The light absorption behaviour was investigated using ultra-violet/visible/near-infrared spectroscopy (UV/vis/NIR), revealing direct band gaps that are phase-dependent (low bornite, E_g = 0.86 eV and high bornite, E_g = 1.25 eV). The band gap exhibited by high bornite nanoparticles lies in the range of optimal solar energy conversion efficiency for a single-junction photovoltaic, making it a potentially useful light absorber consisting of inexpensive, abundant elements. Lastly, the selective formation of bornite nanoparticles, as opposed to the copper sulphides, chalcocite (Cu₂S) and digenite (Cu_1.80S), or chalcopyrite (CuFeS₂) is demonstrated, suggesting solid solution formation between bornite and digenite nanoparticles.