Zwijnenburg Martijn A
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
Phys Chem Chem Phys. 2022 Sep 21;24(36):21954-21965. doi: 10.1039/d2cp01342h.
Quantum confinement like behaviour in CdO and CdS nanoparticles is demonstrated through explicit ev-BSE many-body perturbation theory calculations on 0.6-1.4 nanometre particles of these materials. However, while the lowest optical excited-state, exciton, and the highest occupied and lowest unoccupied quasiparticle states in such nanoparticles are predicted to be delocalised, they are found to be delocalised over the surface of the particle only and not the whole particle volume. The electronic and optical properties of CdO and CdS rocksalt nanoparticles are predicted to differ dramatically from their structurally analogous MgO counterparts, where the lowest exciton and highest occupied and lowest unoccupied quasiparticle states are strongly localised, in contrast. This difference in behaviour between MgO and CdO/CdS is explained in terms of the more polarisable, less ionic, bonding in CdO and CdS. The effect on the optical and fundamental gaps of the particles due to the presence of amine capping agents on the particles' surface is explored and predicted to be relatively small. However, the highest occupied and lowest unoccupied quasiparticle states are found to consistently shift to more shallow values when increasing the surface density of capping agents. An explanation of this shift, finally, is proposed in terms of the dipole field induced by the aligned dipoles of the capping agents.
通过对这些材料0.6 - 1.4纳米颗粒进行显式的ev - BSE多体微扰理论计算，证明了CdO和CdS纳米颗粒中存在类似量子限制的行为。然而，虽然预计此类纳米颗粒中最低的光学激发态、激子以及最高占据和最低未占据准粒子态是离域的，但发现它们仅在颗粒表面离域，而非在整个颗粒体积内离域。预计CdO和CdS岩盐纳米颗粒的电子和光学性质与其结构类似的MgO对应物有显著差异，相比之下，MgO中最低激子以及最高占据和最低未占据准粒子态是强烈局域的。MgO与CdO/CdS之间这种行为差异是根据CdO和CdS中极化性更强、离子性更弱的键合来解释的。研究了颗粒表面存在胺封端剂对颗粒光学和基本能隙的影响，预计该影响相对较小。然而，当增加封端剂的表面密度时，发现最高占据和最低未占据准粒子态会持续向更浅的值移动。最后，根据封端剂排列的偶极子诱导的偶极场对这种移动提出了解释。
