Spontaneous transition and concomitant self-assembly of CdTe nanoparticles into CdS nanosheets induced by L-cysteine

摘要

In this paper, we investigated carefully the influence of the added L-cysteine on the stability of mercaptopropionic acid (MPA)-stabilized CdTe nanoparticles (NPs). Transmission electron microscopy (TEM) imaging revealed that the addition of pH ～11.5 L-cysteine solution could reduce the stability of MPA-capped CdTe NPs, which resulted in the formation of sheet-shaped nanostructures finally after about seven days of storage in darkness under ambient conditions. The typical size of these resulting nanosheets was ～6 μm in length, ～1 μm in width and ～50 nm in thickness. The high-resolution TEM characterization and elemental analysis from energy-dispersed X-ray (EDX) spectrum indicated that these resulting sheets were made from well-crystallized nanopartilces (~4 nm) of CdS rather than CdTe. In addition, XRD analysis and optical microscopy also supported further these experimental observations. Hence, here, the post addition of L-cysteine induced the spontaneous transition and concomitant self-assembly of MPA-stabilized CdTe nanoparticles into luminescent CdS nanosheets.