A sensitive detection of Cr(VI) in wide pH range using polyethyleneimine protected silver nanoclusters

Polyethyleneimine protected silver nanoclusters (AgNCs@PEI) were prepared and used as high sensitive fluorescence probes for detecting Cr(VI). The mechanism worked by combining Cr(VI) with a primary amine of AgNCs@PEI causing electrostatic interaction, which led to the aggregation of AgNCs, as well as fluorescence quenching. Compared with other fluorescence sensors of Cr(VI) detection, this probe shows excellent performances: (i) The fluorescence probe responds immediately after adding Cr(VI). (ii) The fluorescence quenching efficiency of AgNCs@PEI was linearly related to the concentration of Cr(VI) over the range from 0.5 nM to 25 μM. (iii) The limit of detection is as low as 0.05 nM. (iv) High selectivity for Cr(VI) in 14 types of normal metal ions were obtained and especially the probe can be applied in both acidic and alkaline conditions (pH 2.0–11.0). (v) The probe can be used for the determination of Cr(VI) in real samples with satisfactory results. Therefore, the fluorescence probe is of practical significance and application prospects.