Monoclinic Copper(I) Selenide Nanocrystals and Copper(I) Selenide/Palladium Heterostructures: Synthesis, Characterization, and Surface-Enhanced Raman Scattering Performance

We have developed a simple and facile approach to the fabrication of monoclinic Cu2Se nanocrystals and Cu2Se/Pd heterostructures. [(C2H5)(4)N](2)[CuCl4] was chosen as the copper source and SeO2/terpineol was used as the Se-II precursor for the generation of hexagonal CuSe and cubic Cu2-xSe through the hot-injection and one-pot methods, respectively. Both CuSe and Cu2-xSe could be further transformed into monoclinic Cu2Se through heat treatment with trioctylphosphine (TOP) at 220 degrees C. Cu2Se/Pd as well as CuSe/Pd and Cu2-xSe/Pd were readily obtained by simply mixing copper selenides and Pd(NO3)(2) in a 2-propanol solution. The Pd nanoparticles were distributed on the surface of the copper selenides. The effect of certain reaction parameters on the formation of copper selenides was studied. The amount of terpineol used played an important role in the phase-selective synthesis of CuSe and Cu2-xSe. The surface-enhanced Raman scattering (SERS) performance of the heterostructures was investigated with 4-mercaptopyridine (4-Mpy) as a probe molecule. Owing to the strong synergistic effects between Cu2Se and Pd, Cu2Se/Pd showed greater SERS performance than pure Pd or Cu2Se. Moreover, compared to those of CuSe/Pd and Cu2-xSe/Pd, Cu2Se/Pd exhibited the highest SERS sensitivity to 4-Mpy with a detection limit as low as 1.0x10(-9) M, which revealed its phase- and composition-dependent characteristics. This Cu2Se/Pd heterostructure exhibits potential applications in the chemical and biological sensing fields.