Efficient ratiometric fluorescence probe utilizing silicon particles/gold nanoclusters nanohybrid for "on-off-on" bifunctional detection and cellular imaging of mercury (II) ions and cysteine.

An effective ratiometric fluorescent probe based on silicon particles/gold nanoclusters (SiNPs/AuNCs) nanohybrid has been fabricated and applied to be a "on-off-on" switch sensing platform for detection of Hg and cysteine. In this elaborated sensing platform, the SiNPs just acted as internal reference signal, providing a build-in correction for background interferences and environmental effects, to which the AuNCs as a signal report unit for Hg response was covalently grafted by amidation reaction. The fluorescence intensity of SiNPs/AuNCs could be effectively quenched upon adding Hg, accompanied with an easily distinguishable fluorescent color change. The ratiometric fluorescence signal (F/F) of the established nanoprobe was linearly proportional to the concentration of Hg ranging from 0.02 to 24 μM with a low detection limit of 5.6 nM, which is below the guideline value of Hg in drinking water set by the World Health Organization. Interestingly, upon addition of cysteine, the Hg-quenched fluorescence intensity was recovered gradually. Furthermore, the approach developed has also been utilized for Hg detection in real complex biological samples with satisfactory results. More importantly, benefiting from the good water-solubility and excellent biocompatibility, this nanoprobe can monitor the intracellular Hg and cysteine in living cells, indicating its potential applications in advanced biosensing and bioimaging.