Pressure-induced Large Emission Enhancements of Cadmium Selenide Nanocrystals.

Abstract

Pressure-quenching of optical emission largely limits the potential application of many materials in optical pressure-sensing devices, since emission intensity is crucially connected to performance. Boosting visible-light emission at high pressure is, therefore, an important goal. Here, we demonstrate that the emission of CdSe nanocrystals (NCs) can be enhanced by more than an order of magnitude by compression. The brightest emission can be achieved at pressures corresponding to the phase transitions in different sized CdSe NCs. Very bright blue emission can be obtained by exploiting the increase in bandgap with increasing pressure. First-principles calculations indicate that the interaction between the capping oleic acid (OA) layer and the CdSe core is strengthened with increased Hirshfeld charge at high pressure. The effective surface reconstruction associated with the removal of surface-related trap states is highly responsible for the pressure-induced emission enhancement of these CdSe NCs. These findings pave the way for designing a stress nanogauge with easy optical readout and provide a route for tuning bright-fluorescence imaging in response to an externally-applied pressure.