Unmasking the glow of silver clusters: Small silver clusters stabilized by organic materials or inorganic surfaces can exhibit bright photoluminescence, but the origin of this effect has been difficult to establish, in part because the materials are heterogeneous and contain many larger but inactive clusters. Grandjean et al. studied silver clusters in zeolites, using x-ray excited optical luminescence to monitor only the emissive structures (see the Perspective by Quintanilla and Liz-Marzán). Aided by theoretical calculations, they identified the electronic states of four-atom silver clusters bound with water molecules that produce bright green emission—thus identifying candidate materials for application in lighting, imaging, and therapeutics. Science , this issue p. 686 ; see also p. 645

Stabilized fullerene and tubular forms can be produced in boron clusters B_nin small sizes fromn∼ 14 to 20 upon doping by transition metal atoms.