Telluride Nanocrystals with Adjustable Amorphous Shell Thickness and Core-Shell Structure Modulation by Aqueous Cation Exchange

Engineering the structure of core-shell colloidal semiconductor nano- particles (CSNPs) is attractive due to the potential to enhance photo-induced charge transfer and induce favorable optical and electronic properties. Nonetheless, the sensitivity of telluride CSNPs to high temperatures makes it challenging to precisely modulate their surface crystallinity. Herein, we have developed an efficient strategy for synthesizing telluride CSNPs with thin amorphous shells using aqueous cation exchange (ACE). By changing the synthesis temperature in the range of 40-110 degrees C, the crystallinity of the CdTe nanoparticles was controllable from perfect crystals with no detectable amorphous shell (c-CdTe) to a core-shell structure with a crystalline CdTe NP core covered by an amorphous shell of tunable thickness up to 7-8 nm (c@a-CdTe). A second ACE step transformed c@a-CdTe to crystalline CdTe@HgTe core-shell NPs. The c@a-CdTe nanoparticles synthesized at 60 degrees C and having a 4-5 nm thick amorphous shell exhibited the highest surface-enhanced Raman scattering activity with a high enhancement factor around 8.82 x 10(5), attributed to the coupling between the amorphous shell and the crystalline core.

Automated summary

This study developed an efficient strategy to synthesize telluride core-shell colloidal semiconductor nanoparticles (CSNPs) with thin amorphous shells using aqueous cation exchange (ACE). The crystallinity and shell thickness of the CSNPs could be controlled by changing the synthesis temperature. The CSNPs synthesized at 60 degrees C exhibited the highest surface-enhanced Raman scattering activity.