Heterometallic ion-regulated full-color gold nanoclusters for multicolor bioimaging and circularly polarized luminescence

Abstract

Achieving tunable full-color emission and high-efficiency circularly polarized luminescence (CPL) from a single type of nanocluster remains a major challenge due to weak dissymmetry factors and aggregation-induced quenching. This study reports a breakthrough synthesis of full-color-emitting gold nanoclusters via heterometallic ion doping. By reducing HAuCl₄ with 4-amino-2-mercaptopyrimidine (AMP) in the presence of Cr³⁺, Mg²⁺, or Ag⁺, blue (400 nm), green (495 nm), and red (700 nm) emissive NCs were obtained with respective quantum yields of 13.2%, 2.46%, and 3.34%. Structural analysis confirmed compositions of Au₇(AMP)₅Cr₂, Au₆(AMP)₄Mg₂, and Au₆(AMP)₃Ag, all <1.1 nm. Density functional theory calculations further reveal that b-NCs, g-NCs and r-NCs regulate emission energy through local coordination, electronic coupling, and structural rigidity of the Au(I)–SR framework. In summary, dopant ions serve as cross-linkers in surface Au(I)–thiolate motifs, with motif length determining emission color. Co-assembly with chiral lipid gelators induced full-color CPL (g_lum = 10⁻²) via structural rigidification within helical nanotubes. The NCs showed low cytotoxicity and enabled multicolor bioimaging. Anti-counterfeiting gels with dual-level encryption were developed using UV-triggered fluorescence and CPL-handedness. The materials remained stable over one month. This work establishes a metal-ion-directed strategy for emission tuning in Au NCs, linking structures to photophysical properties and offering a flexible platform for chiral optoelectronics.