Tailoring the interaction between a gold nanocluster and a fluorescent dye by cluster size: creating a toolbox of range-adjustable pH sensors.

We present a novel strategy for tailoring the fluorescent azadioxatriangulenium (KU) dye-based pH sensor to the target pH range by regulating the p value of the gold nanoclusters. Based on the correlation between the p and surface curvature of ligand-protected nanoparticles, the p value of the gold nanoclusters was controlled by size. In particular, three different-sized -mercaptobenzoic acid (-MBA) protected gold nanoclusters, Au(-MBA), Au(-MBA), and Au(-MBA) were used as the regulator for the pH range of the KU response.

Systematic study of SYBR green chromophore reveals major improvement with one heteroatom difference.

Five nucleic acid binding cyanine dyes were synthesized and their photophysical properties were evaluated. Changing a single heteroatom in the chromophore causes major differences both in brightness and photostability between the dyes. With such alteration, the brightness of the chromophore increased two-fold compared to the one found in SYBR Green I.