Microsecond-Lived Luminescence in Semiconductor Quantum Dots and Metal Nanoclusters: Unveiling a Common Origin

Nanoscale materials, including semiconductor quantum dots (QDs) and metal nanoclusters (NCs), exhibit extraordinary photoluminescence (PL) properties compared to their bulk counterparts. However, their study has largely been separate, lacking direct comparison. This study provides compelling evidence of a shared photophysical mechanism underlying the μs-lived luminescence in both colloidal organically-capped PbS QDs and gold (Au) NCs, despite their differing material compositions and electronic structures. The absorption spectra underscore fundamental differences: PbS QDs, with a mean size of approximately 3 nm, exhibit sharp excitonic peaks due to quantum confinement (QC), while Au NCs, approximately 1.4 nm in size, show broad, featureless absorption indicative of molecular-like states. However, both PbS QDs and Au NCs display similar long-lived μs-range PL lifetimes and large Stokes shifts. Crucially, the study reveals that when the PL and lifetime spectra of both materials are normalized and spectrally aligned, their lifetime spectra overlap remarkably, while their PL spectra match closely in their peaks, suggesting a shared underlying mechanism governing their emission properties. This finding challenges the conventional view that QC solely dictates the PL of semiconductor QDs with μs-lived PL. Instead, metal-sulfur interactions are suggested to play a pivotal role in governing the long-lived emission in both materials.