Synthesis of ultrasmall water-soluble fluorescent gold nanoclusters is reported. The clusters have a decent quantum yield, high colloidal stability, and can be readily conjugated with biological molecules. Specific staining of cells and nonspecific uptake by living cells is demonstrated.

Amphiphilic polymer‐coating for nanoparticles: The facile one‐pot synthesis of a comblike polymer can be tailored in order to vary its hydrophobic side‐chains or to directly incorporate functional molecules without the need for crosslinkers. This leads to a general and robust method of phase‐transfer of hydrophobic nanoparticles to aqueous solution, as well as to their modification with functional molecules.

A concept is describe that facilitates the modification of colloidal nanoparticles of different materials with an exactly known number of variable functional groups. In particular, a procedure for the surface functionalization of nanoparticles with a controlled number of mono‐ or bifunctional poly(ethylene glycol) (PEG) molecules of suitable chain length is reported. Conjugates of nanoparticles with one, two, and three PEG molecules per nanoparticle could be separated using gel electrophoresis. Molecules with additional functionalities could be conjugated to the free ends of the bifunctional PEG molecules. In this way the PEG molecules act as convenient spacers that allow for the sorting of nanoparticles with a discrete number of functional groups.