Stability and Fluorescence Quantum Yield of CdSe–ZnS Quantum Dots—Influence of the Thickness of the ZnS Shell


Address for correspondence: Dr. Ute Resch-Genger, Federal Institute for Materials Research and Testing, Department I.5, Richard-Willstaetter-Str. 11, 12489 Berlin, Germany. Voice: +049-30-81041134; fax: +049-30-81045005.


We investigated the correlation between the thickness of the ZnS shell of CdSe–ZnS quantum dots (QDs), the stability of the particles, and the fluorescence quantum yield. As a measure for stability, a new shell quality test was developed. This test is based on the reaction of the QDs with photochemically formed thiophenol radicals and communicates an imperfect ZnS shell by a rapid and complete loss of fluorescence. The quantum yield increases from less than 5% for unshelled CdSe up to 50%, with an increase in ZnS shell thickness up to 0.6–0.8 nm. At the same time, the particles become significantly more stable, as revealed by the shell test.