Bottom-up fabrication of two-dimensional carbon nitride and highly sensitive electrochemical sensors for mercuric ions

Abstract

We report microwave assisted bottom-up fabrication of flat two-dimensional carbon nitride from formamide (HCONH₂). Microwave irradiation of HCONH₂ produces carbon nitride dots (CNDs) which are used as precursors for synthesis of carbon nitride (C₃N₄). The two-dimensional (2D) carbon nitride sheets are formed by evaporation induced self-assembly and condensation of CNDs on a solid substrate. The drying of CND solution generates different morphologies such as 0D carbon nitride quantum dots, 2D carbon nitride sheets and 3D carbon nitride, depending on the concentration of CNDs. The carbon nitrides are well characterized by TEM, AFM, SEM, XRD, XPS, FT-IR, FT-Raman Spectroscopy and TGA, CHN analysis. In addition, the C₃N₄ modified glassy carbon electrode can be used as a highly sensitive electrochemical sensor for mercuric ions in aqueous solution. The lower detection limit of Hg²⁺ is found to be 9.1 × 10⁻¹¹ M, which is far below the WHO guideline for drinking water (10⁻⁸ M). The simultaneous electrochemical detection of Pb²⁺, Cu²⁺ and Hg²⁺ using a C₃N₄ modified GC electrode is also described.