Alloying is an important strategy in tailoring the functionality of materials. In metal nanoclusters (NCs), the introduction of a heterometal leads to alloy nanoclusters that often outperform the homometal ones in terms of the physical and chemical properties. In this work, a series of four M₁₄₄(PET)₆₀ alloy NCs (where, M = Au/Ag, PET = –SCH₂CH₂Ph) are synthesized and characterized. The silver doping into the homogold template (Au₁₄₄) leads to more prominent optical absorption features in the steady-state spectrum in the visible range. Femtosecond transient absorption spectroscopy reveals the effect of Ag doping on the electronic relaxation dynamics compared to Au₁₄₄ and the pump fluence independent dynamics. Electrochemical results reflect a narrowing of HOMO–LUMO gap (E_g) induced by Ag doping. A temperature dependence of the single-electron charging is also observed for the series of alloy NCs, in which the E_g values of the alloy NCs enlarge as the temperature decreases, which is characteristic of semiconducting behavior.

Luminescent metal nanoclusters (NCs) have recently emerged as a novel class of luminescent nanomaterials and hold significant potential in biomedicine owing to their ultrasmall (< 2 nm) size, excellent photostability, and good biocompatibility. The recent rapid advances in the synthesis and functionalization of luminescent metal NCs have enabled scientists to develop colorful nanomaterials and nanodevices for a wide range of biomedical applications. In this review, we summarize the characteristics and advantages of luminescence from metal NCs, and highlight their applications in biomedicine. We focus on the research in biomedical detection, bio-imaging, drug delivery, and therapy, especially for the advances in the last five years. Luminescent metal NCs display a series of unique superiorities in biomedical applications, and the recent achievements have brought a lot of benefits to the diagnosis and treatment of clinical diseases, especially for tumors and cancers. Finally, we put forward the main challenges that currently still hinder the basic science studies and the practical development of luminescent metal NCs in biomedical applications. Overall, we expect that luminescent metal NCs will play a much more important role in future biomedicine and clinical applications.

The recent success in the synthesis and total structure determination of atomically precise gold nanoparticles has provided exciting opportunities for fundamental studies as well as the development of new applications. These unique nanoparticles are of molecular purity and possess well defined formulas (i.e., specific numbers of metal atoms and ligands), resembling organic compounds. Crystallization of such molecularly pure nanoparticles into macroscopic single crystals allows for the determination of total structures of nanoparticles (i.e., the arrangement of metal core atoms and surface ligands) by X-ray crystallography. In this perspective article, we summarize recent efforts in doping and alloying gold nanoparticles with other metals, including Pd, Pt, Ag and Cu. With atomically precise gold nanoparticles, a specific number of foreign atoms (e.g., Pd, Pt) can be incorporated into the gold core, whereas a range of Ag and Cu substitutions is observed but, interestingly, the total number of metal atoms in the homogold nanoparticle is preserved. The heteroatom substitution of gold nanoparticles allows one to probe the optical, structural, and electronic properties truly at the single-atom level, and thus provides a wealth of information for understanding the intriguing properties of this new class of nanomaterials.