Major Electronic Transition Shift from Bandgap to Localized Surface Plasmon Resonance in CdxHg1–xSe Alloy Nanocrystals

Abstract

CdxHg1–xSe alloy nanocrystals are obtained from CdSe semiconductor nanocrystals via cation exchange. By varying the composition during the exchange process, the CdxHg1–xSe alloy nanocrystals offer a widely tunable electronic transition from visible to NIR and even to mid-IR range. The visible bandgap transition of the CdSe colloidal quantum dot gradually red-shifts to the near-IR with the addition of the Hg precursor, and then the steady-state intraband (or intersub-band) transition of the CdxHg1–xSe alloy nanocrystals appears. Finally, as the electron density is increased by successive addition of metal precursor, localized surface plasmon resonances (LSPRs) appear as a major electronic transition in the mid-IR regime. The shift of the major electronic transition from the bandgap to LSPRs infers that the exciton spatially moves to the surface from the inside of the nanocrystal through the cation change and further crystal growth. The corresponding variance of the nanocrystals’ structural, compositional, ...