Aggregation-induced structural clamping drives NIR photoluminescence switching in Au2Cu6 nanoclusters by suppressing El-Sayed-allowed intersystem crossing

Abstract

Aggregation of Au₂Cu₆ nanoclusters (NCs) triggers a drastic near-infrared phosphorescence-to-fluorescence switch. This transition originates from structural clamping that suppresses the El-Sayed allowed intersystem crossing pathway by hindering the geometric relaxation, causing a 25,600-fold rate reduction. This mechanism provides a unified framework to explain the anomalous photoluminescence behaviors in Au₂Cu₆-based NCs.