One-pot preparation of graphene–Ag nano composite for selective and environmentally-friendly recognition of trace mercury(ii)

Abstract

A graphene–silver nano composite (G–Ag NPs) has been identified and prepared by a simple one-pot redox method using ascorbic acid as the catalytic reagent. After its structure was characterized by UV-vis spectroscopy, Raman spectroscopy and transmission electron microscopy, the absorption spectral properties were investigated in detail. The characteristic absorption peak of the as-prepared G–Ag NPs at ca. 420 nm could be selectively quenched upon addition of Hg²⁺ in the presence of ascorbic acid, owing to the formation of a specific amalgam between mercury and silver nano particles. Under pH 5.0, the response possessed an excellent selectivity and sensitivity to Hg²⁺ over the linear range of 2.0 × 10⁻⁷ to 3.25 × 10⁻⁶ M with a detection limit of 3.1 × 10⁻⁸ M. Other commonly existing metal ions had almost no influence on the absorption response. Importantly, the proposed low-toxicity G–Ag NPs were successfully applied to detect trace Hg²⁺ in three real environmental water samples with a relative standard deviation (R.S.D.) of less than 4.6% (n = 5) and with little secondary pollution.