title: Optical properties of PbS nanocrystal quantum dots at ambient and elevated pressure.
abstract: We investigated pressure-dependent changes in the optical properties of PbS nanocrystal quantum dots (NQD) by combining X-ray scattering and optical absorption spectroscopy in a diamond anvil cell. We discovered that the excitonic absorption peak vanishes as the NQD crystal structure reversibly undergoes the pressure-induced phase transition from rock-salt to orthorhombic structure. In the rock-salt phase, the pressure coefficient ∂E(g)/∂P of PbS NQD is negative and decreases in magnitude with decreasing NQD size. The basic theoretical model based on literature values of the PbS bulk modulus significantly overestimated the change in pressure coefficient with NQD size. We present a model that includes the size-dependence of both the pressure coefficient and bulk modulus to describe the experimentally observed optical and structural trends.
authors.affiliation: School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA. th358@cornell.edu.
authors.forename: Kaifu
authors.initials: K
authors.lastname: Bian
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Richards
authors.forename: Hanqing
authors.initials: H
authors.lastname: Yang
authors.forename: William
authors.initials: W
authors.lastname: Bassett
authors.forename: Frank W
authors.initials: FW
authors.lastname: Wise
authors.forename: Zhongwu
authors.initials: Z
authors.lastname: Wang
authors.forename: Tobias
authors.initials: T
authors.lastname: Hanrath