One-step solvent-free synthesis and characterization of Zn _1-xMn_xSe@C nanorods and nanowires

The carbon-encapsulated, Mn-doped ZnSe (Zn_1-xMn_xSe@C) nanowires, nanorods, and nanoparticles are synthesized by the solvent-free, one-step RAPET (reactions under autogenic pressure at elevated temperature) approach. The aspect ratio of the nanowires/nanorods is altered according to the Mn/Zn atomic ratio, with the maximum being observed for Mn/Zn = 1:20. A 10-20 nm amorphous carbon shell is evidenced from electron microscopy analysis. The replacement of Zn by Mn in the Zn_1-xMn_xSe lattice is confirmed by the hyperfine splitting values in the electron paramagnetic resonance (EPR) experiments. Raman experiments reveal that the Zn _1-xMn_xSe core is highly crystalline, while the shell consists of disordered graphitic carbon. Variable-temperature cathodoraminescence measurements are performed for all samples and show distinct ZnSe near-band-edge and Mn-related emissions. An intense and broad Mn-related emission at the largest Mn alloy composition of 19.9% is further consistent with an efficient incorporation of Mn within the host ZnSe lattice. The formation of the core/shell nanowires and nanorods in the absence of any template or structure-directing agent is controlled kinetically by the Zn _1-xMn_xSe nucleus formation and subsequent carbon encapsulation. Mn replaces Zn mainly in the (111) plane and catalyzes the nanowire growth in the [111] direction.