Wurtzite Cu₂GeS₃ Nanocrystals: Phase- and Shape-Controlled Colloidal Synthesis.

The first colloidal synthesis of Cu2 GeS3 (CGS) nanocrystals with a thermodynamically metastable wurtzite crystal phase is reported. As a benefit of the sulfur precursors used in the synthesis, the shape of the as-synthesized wurtzite CGS nanocrystals can be controlled in the form of spherical nanoparticles, nanorectangles, and hollow nanorectangles. A detailed investigation into the effects of reaction conditions necessary to obtain phase-pure wurtzite CGS nanocrystals is presented. The choice of sulfur precursor and precursor injection temperature play a significant role in determining the crystal phase of the CGS nanocrystals. The band gap of the new wurtzite phase CGS was measured to be 1.76 eV and the CGS nanocrystals exhibited a good electrochemical photoresponse, which was indicative of their potential application as an active layer in the field of solar cells.