Phase-selective synthesis of bornite nanoparticles

Nanoparticles of the copper iron sulfide phase bornite (ideally Cu(5)FeS(4)) 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 (Cu(2)S) and digenite (Cu(1.80)S), or chalcopyrite (CuFeS(2)) is demonstrated, suggesting solid solution formation between bornite and digenite nanoparticles.