Inner filter effect of gold nanoparticles on the fluorescence of quantum dots and its application to biological aminothiols detection.

We have demonstrated the design of a new type fluorescence assay based on the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of quantum dots (QDs). With a high extinction coefficient, AuNPs are expected to be capable of functioning as powerful absorbers. QDs with tunable emission wavelength are ideal fluorophores because the emission spectra of the rationally synthesized QDs can perfectly overlap with the absorption band of the absorber. Aminothiols are chosen as the model analytes, and the IFE-based fluorescent method for detection of aminothiols was suggested. Under the optimum conditions, the response is linearly proportional to the concentration of cysteine in the range of 0.05-0.9 μg mL(-1). The present IFE-based fluorescent strategy could be also used to detect glutathione and homocysteine. The linear concentration ranges were 0.05-1.0 μg mL(-1) for glutathione and 0.01-1.0 μg mL(-1) for homocysteine.