Synthesis of Bismuth‐Nanoparticle‐Enriched Nanoporous Carbon on Graphene for Efficient Electrochemical Analysis of Heavy‐Metal Ions

A BiNPs@NPCGS nanocomposite was designed for highly efficient detection of multiple heavy‐metal ions by in situ synthesis of bismuth‐nanoparticle (BiNP)‐enriched nanoporous carbon (NPS) on graphene sheet (GS). The NPCGS was prepared by pyrolysis of zeolitic imidazolate framework‐8 (ZIF‐8) nanocrystals deposited on graphene oxide and displayed a high surface area of 1251 m² g^?1 and a pore size of 3.4 nm. BiNPs were deposited on NPCGS in situ by chemical reduction of Bi³⁺ with NaBH₄. Due to the restrictive effect of the pore/surface structure of NPCGS, the BiNPs were uniform and well dispersed on the NPCGS. The BiNPs@NPCGS showed good conductivity and high effective area, and the presence of BiNPs allowed it to act as an efficient material for anodic‐stripping voltammetric detection of heavy‐metal ions. Under optimized conditions, the BiNPs@NPCGS‐based sensor could simultaneously determine Pb²⁺ and Cd²⁺ with detection limits of 3.2 and 4.1 nM , respectively. Moreover, the proposed sensor could also differentiate Tl⁺ from Pb²⁺ and Cd²⁺. Owing to its advantages of simple preparation, environmental friendliness, high surface area, and fast electron‐transfer ability, BiNPs@NPCGS showed promise for practical application in sensing heavy‐metal ions.