Nanocluster Synthesis and Optical Properties

Metal nanoclusters, typically composed of a few to a few hundred atoms with core diameters below 3 nm, occupy an intermediate realm between molecular complexes and larger nanoparticles. Synthesis strategies range from chemical reduction in the presence of thiolate or phosphine ligands to seed-mediated growth pathways that afford atomically precise sizes. Ligand exchange and core–shell architectures further enable fine control of surface chemistry and stability. Owing to strong quantum confinement, these clusters exhibit discrete electronic states rather than continuous bands, giving rise to size- and composition-dependent optical signatures. Photoluminescence spans from the visible into the near-infrared II window, while clusters above approximately 2 nm can display nascent surface plasmon resonance. Precise structural determination has revealed isomerism and twinning motifs that modulate absorption and emission. The tunable optical response underpins applications in biological imaging, sensing and photoredox catalysis, as well as emerging roles in optoelectronics and renewable‐energy conversion.

Research from Nature Portfolio

Recent studies have employed ultrafast spectroscopy on atomically precise gold clusters to map the transition from plasmonic to excitonic behaviour as size decreases. Three distinct regimes—metallic, transition and non‐metallic—have been delineated, correlating structural motifs with optical lifetimes and catalytic activity. In parallel, high‐resolution crystallographic analyses of twinned silver nanoparticles comprising hundreds of atoms have demonstrated the onset of surface plasmon resonance in structures just above the molecular regime. These experiments provide definitive links between atomic‐scale architecture and emergent plasmonic absorption, guiding the rational design of clusters with tailored optical fingerprints.

Nanocluster Synthesis and Optical Properties publication trend

The graph below shows the total number of articles in nanocluster synthesis and optical properties across all publications each year (not limited to Nature Index journals).

Technical terms

Quantum confinement: The effect by which electronic energy levels become discrete when particle dimensions approach the de Broglie wavelength of electrons.

Surface plasmon resonance: Collective oscillation of conduction electrons in metallic nanoparticles, leading to strong, size‐dependent light absorption.

Photoluminescence: Emission of light following electronic excitation, often characterised by emission wavelength and quantum yield.

Exciton: Bound state of an electron and a hole whose recombination yields characteristic optical transitions in nonmetallic clusters.

Ligand-protected nanocluster: A cluster of metal atoms stabilised by organic or inorganic ligands that define its surface chemistry and electronic structure.

References

1. Biological Interaction and Imaging of Ultrasmall Gold Nanoparticles. Nano-Micro Letters (2023).
2. Visible to NIR‐II Photoluminescence of Atomically Precise Gold Nanoclusters. Advanced Materials (2023).
3. Structural isomerism in gold nanoparticles revealed by X-ray crystallography. Nature Communications (2015).
4. Plasmonic twinned silver nanoparticles with molecular precision. Nature Communications (2016).
5. Stabilizing ultrasmall Au clusters for enhanced photoredox catalysis. Nature Communications (2018).
6. Evolution from the plasmon to exciton state in ligand-protected atomically precise gold nanoparticles. Nature Communications (2016).
7. Understanding seed-mediated growth of gold nanoclusters at molecular level. Nature Communications (2017).
8. Ultrasmall Glutathione-Protected Gold Nanoclusters as Next Generation Radiotherapy Sensitizers with High Tumor Uptake and High Renal Clearance. Scientific Reports (2015).