No abstract

In this paper, we explore whether interparticle spacing affects steady-state and transient-state optical properties by comparing close-packed CdSe/ZnS–quantum dots (QDs) and CdSe/ZnS–QDs dispersed in polymethyl methacrylate (PMMA). High–pressure is an effective physical means to adjust the interparticle spacing of QDs, which may artificially expand the application of QDs further. The results under high–pressure indicate that it is the reduced interparticle spacing rather than the enhanced quantum confinement effect with volume compression that has a stronger effect on exciton relaxation of CdSe/ZnS–QDs. This work is hoped to help us further understand the effect of interparticle spacing among QDs in various integrated environments.

The interparticle spacing of a heterostructure is a crucial factor affecting electron transfer (ET) process. Herein, binary nanoparticle superlattices (BNSLs) composed of CdSe/ZnS quantum dots (QDs) and Au nanoclusters (NCs) are prepared. Steady-state and time-resolved spectra illustrate that the ET accelerates as the pressure increases because pressure effectively adjusts the interparticle spacing. The results also demonstrate that the trap state of the CdSe/ZnS QDs affects the ET process of BNSLs.

Following the gradual maturation of synthetic techniques for nanomaterials, exciton–plasmon composites have become a research hot-spot due to their controllable energy transfer through electromagnetic fields on the nanoscale. However, most reports ignore fluorescence resonance energy transfer (FRET) under electrostatic repulsion conditions. In this study, the FRET process is investigated in both electrostatic attraction and electrostatic repulsion systems. By changing the Au : quantum dot ratio, local-field induced FRET can be observed with a lifetime of ns and a fast component of hundreds of ps. These results indicate that the intrinsic transfer process can only elucidated by considering both steady and transient state information.

Pressure can reduce the distances among atoms, thereby modifying the overall optical characteristics of molecules. In this article, the excited state behavior of perylene is carefully observed under isotropic pressure and non-complexing condition. In a steady state, absorption peak shows red shift and spectral width are broadened with pressure increasing, which is ascribed to the π-electron delocalization between molecules. In a transient state, the transition dynamics presents a wavelike tendency with pressure increasing because the shift of self-tapping exciton state is contrary to that of Y-state with pressure increasing. The results conduce to understanding the influence of inter-molecule interaction on excited state behavior with inter-molecule distance decreasing, which contributes to studying the materials under extreme condition.