Engineering Mono- to Trimetallic Nanoclusters for Next-Generation Luminescence Sensing of Narcotic Drugs

Monometallic, bimetallic, and trimetallic fluorescent nanoclusters (NCs) stabilized by lysozyme (Lyz), glutathione (GSH), and 4-mercaptopropionic acid (MPA) were synthesized using gold (Au), silver (Ag), and cadmium (Cd) via a simple chemical route. Among the synthesized NCs, the trimetallic systems demonstrated superior photoluminescent and sensing properties. Specifically, the quantum yields of AuAgCd-Lyz and AuAgCd-GSH nanoclusters were determined to be 1.42% and 2.09%, respectively. Comparative analysis revealed that trimetallic NCs exhibited significantly enhanced sensitivity in the detection of the narcotic drugs amphetamine and morphine, supported by distinct differences in their photoluminescence (PL) lifetimes. Furthermore, AuAgCd-Lyz clusters outperformed their GSH- and MPA-stabilized counterparts, which is attributed to weaker Au-amide interactions compared to the stronger Au-thiol bonds, allowing for more favorable analyte-cluster interactions. Binding constant values calculated using the Benesi-Hildebrand equation were found to be Ka = 5.82 × 10³ M⁻¹ for amphetamine and 7.89 × 10³ M⁻¹ for morphine. These findings establish trimetallic nanoclusters, particularly those stabilized by lysozyme, as highly effective and selective fluorescent probes for drug sensing, surpassing the capabilities of mono- and bimetallic analogues. TOC GRAPHICS.