Voltammetric Sensor Modified by EDTA-immobilized Graphene-like Carbon Nitride Nanosheets: Preparation, Characterization and Selective Determination of Ultra-Trace Pb (II) in Water Samples

A voltammetric sensor for selective determination of ultra-trace Pb (II) was prepared based on EDTA-immobilized graphene-like carbon nitride nanosheets (EDTA-CN-NS), which has been designed to improve the accumulation performance for Pb (II) onto the electrode surface. The EDTA-CN-NS was prepared through pre-oxidation by K2S2O8 and silanization by N-(trimethoxysilylpropyl) ethylene-diamine triacetic acid sodium salt. The crystalline structure, morphology and the added functional groups of EDTA-CN-NS were characterized by XRD, SAED, TEM, STEM mapping and FT-IR, which are quite in accord with the catalysis action in cyclic voltammetry test generated by improved accumulation performance of the immobilized EDTA for Pb (II). The detection limit of EDTA-CN-NS/Nafion modified sensor reached 5.7 × 10−13 mol L−1 with two linear ranges from 2.1 × 10−12 ∼ 1.3 × 10−9 mol L−1 and 1.3 × 10−9 ∼ 1.7 × 10−6 mol L−1. The sensor behaves acceptable immunity from common interferences in Pb (II) determination and was employed for analyzing the Pb (II) concentration in different water samples. This work gives new instructions in designing ultra-high sensitive sensors for determination of heavy metal ions using 2D functional materials.