Highly fluorescent, water-soluble, size-tunable gold quantum dots.

Highly fluorescent, water-soluble, few-atom Au quantum dots have been created that behave as multielectron artificial atoms with discrete, size-tunable electronic transitions throughout the visible and near IR. Correlation of nanodot sizes with emission energies fits the simple relation, EFermi/N1/3, predicted by the jellium model. Providing the "missing link" between atomic and nanoparticle behavior in noble metals, these emissive, water-soluble Au nanoclusters open new opportunities for biological labels, energy transfer pairs, and light emitting sources in nanoscale optoelectronics.