Self-Narrowing and Photoetching Effects on the Size Distribution of CdS Quantum Dots Prepared by a Reverse-Micelle Method

Abstract

We have investigated self-narrowing and photoetching effects on the size distribution of CdS quantum dots (QDs). The QDs with a narrow size distribution are prepared by a reverse-micelle method and their mean radii are controlled by changing the water content in the reverse micelle. The mean radius and size-distribution width estimated from the line-shape analysis of absorption spectra agree well with those obtained from transmission electron microscope images, which indicates that the analysis is a convenient and reasonable method of estimating the size-distribution width. For the QDs whose initial size distribution is larger than ∼10%, the size-distribution reduction due to a “self-narrowing process” is observed: The size-distribution width is spontaneously reduced with the time elapsed after the QD preparation. The further reduction of the size-distribution width is achieved by performing a photoetching treatment. The above results clearly show the possibility of preparing CdS QDs with the narrow size distribution by using the self-narrowing and photoetching effects.