Pressure-Induced Emission Enhancements and Ripening of Zinc-Blende Cadmium Selenide Nanocrystals

Zinc blende cadmium selenide nanocrystals (Zb-CdSe NCs) were found to exhibit excellent photostability and high quantum yield compared with wurtzite (Wz) CdSe NCs, although Wz-CdSe NCs are more stable in nature. Previous studies were mainly focused on the pressure-induced structural phase transition of Zb-CdSe NCs limited by the in situ high-pressure fluorescence and absorption characterization. Here, we demonstrated that the Zb-CdSe NCs exhibited an intriguing pressure-induced emission enhancement and a ripening process through the in situ high-pressure optical measurements. The emission intensity of Zb-CdSe NCs was enhanced almost seven times because of the strengthened interaction between the capping stearic acid layer and the Zb-CdSe core under high pressure. Moreover, the stark discontinuity at 4 GPa in both the photoluminescence and absorption spectra was attributed to the increased size of Zb-CdSe NCs resulting from the ripening of samples under high pressure. This ripening of Zb-CdSe NCs was also corroborated by the corresponding size distribution based on high-resolution transmission electron microscopy. Our studies further indicated that the band gap of Zb-CdSe NCs could be fine-tuned to a desirable region by pressure. These findings pave the way for providing a route for tuning bright fluorescence imaging and band gap in application to semiconductor devices.