Size-Dependent Response of CdSe Quantum Dots to Hydrostatic Pressure
Zifei Chen, J. Curtis Beimborn, Nicholas Kirkwood, Salvy P. Russo, J. Mathias Weber, Paul Mulvaney
Abstract
The size-dependent pressure response of oleate-stabilized CdSe quantum dots (QDs) in paraffin is investigated using diamond anvil cell experiments and density functional theory (DFT). For QDs above 3.0 nm, the photoluminescence shows a blue-shift of around 43 meV/GPa, close to the value for bulk CdSe, but the shift increases strongly for nanocrystals less than 3 nm in size. Conversely, the absorption shift is 45 meV/GPa above 3.0 nm but weakens to 35 meV/GPa for particles 1.5 nm in size. No crystallographic phase transitions occur below 2 GPa, and the optical effects are reversible. DFT calculations confirm that shifts in the bulk modulus begin for sizes estimated to be 1/2 of the Bohr radius, which we term the extreme confinement regime.