Intrinsically fluorescent gold nanoclusters stabilized within a copper storage protein that follow the Irving-Williams trend in metal ion sensing.

Creating new environmentally friendly and non-toxic biomaterials with novel properties is required for numerous applications in healthcare and sensing. Protein bound gold nanoclusters constitute one such class of materials that offer promise in fluorescence imaging and sensing applications. However, unlike alkane thiol-protected gold nanoclusters, the number of protein-templated gold nanoclusters with such properties is limited and there is a need to expand the repertoire of such attractive hybrid quantum clusters.

Unique Energy Transfer in Fluorescein-Conjugated Au Nanoclusters Leading to 160-Fold pH-Contrasting Photoluminescence.

Accurate measurements of intracellular pH are of crucial importance in understanding the cellular activities and in the development of intracellular drug delivery systems. Here we report a highly sensitive pH probe based on a fluorescein-conjugated Au nanocluster. Steady-state photoluminescence (PL) measurements have shown that, when conjugated to Au, fluorescein exhibits more than 160-fold pH-contrasting PL in the pH range of 4.