Self-assembly of Copper Sulfide Nanoparticles to Solid, Hollow Spherical and Wire-Shaped Structures

Nanoscale copper sulfide hollow spheres with phase-engineered composition: covellite (CuS), digenite (Cu1.8S), chalcocite (Cu2S)

Covellite (CuS), digenite (Cu(1.8)S) and chalcocite (Cu(2)S) are prepared as nanoscaled hollow spheres by reaction at the liquid-to-liquid phase boundary of a w/o-microemulsion. According to electron microscopy (SEM, STEM, TEM, HRTEM) the hollow spheres exhibit an outer diameter of 32-36 nm, a wall thickness of 8-12 nm and an inner cavity of 8-16 nm in diameter. The phase composition is determined based on HRTEM, electron-energy loss spectroscopy, X-ray powder diffraction and thermal analysis. In face of the advanced morphology of the hollow spheres, precise control of its phase composition is nevertheless possible by adjusting the experimental conditions (i.e. type and concentration of the copper precursor, concentration of ammonia inside of the micelle). Such phase-engineering of nanoscale hollow spheres is firstly observed and might allow adjusting even further compositions/structures as well as tailoring of phase-specific properties in the future.

Fast synthesis, formation mechanism, and control of shell thickness of CuS hollow spheres

CuS hollow spheres were quickly synthesized under mild conditions with spherical aggregates of Cu(2)O nanoparticles as sacrificial templates. The mechanism involved in the synthesis process has been studied using transmission electron microscopy, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, thermal gravimetry, and Fourier transform infrared spectra. The results show that the formation of loose aggregates of Cu(2)O nanoparticles is the key to the fast synthesis of hollow spheres at low temperature. The thickness of the shell can be controlled easily by adjusting the aggregation degree of the Cu(2)O nanoparticles.