Fabrication of silver nanoclusters with enhanced fluorescence triggered by ethanol solvent: a selective fluorescent probe for Cr 3+ detection

We present a facile method for the preparation of red-emitting and water-soluble silver nanoclusters (Ag NCs) using dihydrolipoic acid and sodium borohydride as the template and reducing agent. Ethanol solvent is demonstrated to endow Ag NCs with dramatically enhanced fluorescence; therefore, the Ag NCs are synthesized in ethanol/water solution (e/w-Ag NCs) instead of aqueous solution. Specific trivalent chromium (Cr 3+ ) recognition capability of the e/w-Ag NCs can thus be obtained on the basis of its fluorescence quenching. The mechanisms for fluorescence enhancement and quenching of the e/w-Ag NCs triggered by ethanol and Cr 3+ , respectively, are investigated in detail. Next, a fluorescence method for detection of Cr 3+ is established and its analytical performance is evaluated: the detection limit for Cr 3+ is 0.71 μM and the linear range is from 2 to 40 μM. The fluorescent probe exhibits sufficient sensitivity and good selectivity toward Cr 3+ , illustrating that it has great promise for practical application in Cr 3+ detection.