Recognition and determination of multi-metal ions based on silver nanoclusters capped by polyethyleneimine with different molecular weights

Abstract

Ag nanoclusters templated by hyperbranched polyethyleneimine (PEI) with different molecular weights have been developed as a new fluorescent platform for the sensitive and selective recognition of Hg²⁺, Cu²⁺, Co²⁺ and Ni²⁺ based on fluorescence quenching of the Ag nanoclusters. This sensing system shows good linear ranges and lower detection limits: the linear ranges are 0.1 nM to 10 μM for Hg²⁺, 0.1 nM to 20 μM for Cu²⁺, 1 nM to 20 μM for Co²⁺, and 1 nM to 30 μM for Ni²⁺; the limits of detection for Hg²⁺, Cu²⁺, Co²⁺, and Ni²⁺ are estimated to be 35 pM, 28 pM, 0.33 nM, and 0.30 nM, respectively. In addition, the different molecular weights of PEI reveal little effect on the sensitivity and linear ranges of detection. Most importantly, by adding different masking agents, the presence of Hg²⁺, Cu²⁺, Co²⁺ and Ni²⁺ could be selectively quantified without interference from other metal ions, for instance thymine was used for masking Hg²⁺, potassium pyrophosphate for masking Cu²⁺, nitrilotriacetic acid for masking Co²⁺ and dimethylglyoxime for masking Ni²⁺. On this basis, not only the content of a single type of metal ion but also the total amount of metal ions could be readily detected, which would further improve the convenience and practicability of metal ion sensors. Furthermore, this sensing system has been applied successfully for the detection of Hg²⁺, Cu²⁺, Co²⁺ and Ni²⁺ in real water samples.