Precursor and oxygen dependence of the unidirectional seeded growth of CdSe nanorods

摘要

It was recently shown that, by controlling the O2 concentration, the seeded-growth of CdSe nanocrystals (NC) can be manipulated to proceed either unidirectionally (from the (0001) facet) or three-dimensionally. In this contribution, we investigate two new Se precursors (i.e. SeO2 and NaHSe) and compare them with Se obtained from etching of smaller NC seeds. Under anaerobic conditions, both precursors led to successful 3-dimensional (3D) NC growth. At high O2 concentrations, the seeded growth of rods was enhanced by the NaHSe precursor, while impeded by the use of SeO2. Mechanistic studies showed that the reduction of SeO2 to Se^2- produces an excessive amount of O2. This leads to rod fragmentation due to etching as well as the production of deep traps that quench their luminescence. These new precursors, along with a heightened understanding of oxygen's role, expand the synthetic repertoire of the redox-assisted, seeded-growth of CdSe and better position this low temperature (125 °C) methodology towards realizing advanced NC heterostructures.