Chemical substitution of Cd ions by Hg in CdSe nanorods and nanodots: Spectroscopic and structural examination

Abstract

► We studied cadmium-by-mercury chemical substitution in CdSe nanocrystals. ► Zinc blende CdSe quantum dots can be easily converted to isostructural Cd x Hg 1− x Se. ► Wurtzite CdSe QDs require longer time to convert to a zinc blende Cd x Hg 1− x Se. ► Wurtzite CdSe nanorods transform to nanoheterogeneous luminescent Cd x Hg 1− x Se rods. The chemical substitution of cadmium by mercury in colloidal CdSe quantum dots (QDs) and nanorods has been examined by absorption, photoluminescence and Raman spectroscopy. The crystalline structure of original CdSe QDs used for Cd/Hg substitution (zinc blende versus wurtzite) shows a strong impact on the optical and structural properties of resultant Cd x Hg 1− x Se nanocrystals. Substitution of Cd by Hg in isostructural zinc blende CdSe QDs converts them to ternary Cd x Hg 1− x Se zinc blende nanocrystals with significant NIR emission. Whereas, the wurtzite CdSe QDs transformed first to ternary nanocrystals with almost no emission followed by slow structural reorganization to a NIR-emitting zinc blende Cd x Hg 1− x Se QDs. CdSe nanorods with intrinsic wurtzite structure show unexpectedly intense NIR emission even at early Cd/Hg substitution stage with PL active zinc blende Cd x Hg 1− x Se regions.