Self-supporting porous S-doped graphitic carbon nitride as a multifunctional support of Au catalyst: Application to highly sensitive and selective determination of arsenic (III) in a wide range of pH

To investigate heteroatom-doped carbon nitride (C3N4) materials as supports, Au nanoparticles anchored on sulfur-doped carbon nitride nanosheets (AuNPs@SCNN) was prepared and used as a catalyst for arsenic elec-troreduction. Novel SCNN was synthesized for the first time via a simple thermally induced copolymerization route using ammonium persulfate (APS) as a low-cost sulfur source. Thereafter, the SCNN was used to integrate with AuNPs for the benefit of enhancing the quality of assembly and interface between SCNN and AuNPs and improving the catalytic activity of the AuNPs@SCNN nanocatalyst. This optimized assembly was characterized by different techniques, morphologically favorable heterojunction formation between SCNN and AuNPs. More importantly, it was confirmed that the addition of APS during the polymerization of urea not only afforded a significant morphological change from a layered material to a porous structure with many in-plane holes, but also resulted in a higher yield than urea. The electrocatalytic reduction of arsenic was considered at a glassy carbon electrode modified by the composite (AuNPs@SCNN/GCE), which exhibited enhanced electrochemical responses in a wide range of pH conditions with minimal interference of Cu. More distinctly, this robust and repeatable detection method exhibits a linearity range of 0.2-30.0 ppb and a detection limit of 0.07 ppb. The successful determination of arsenic concentration in real water samples also underpins its practical applications in the real world. This promotes innovative design for the synthesis of novel functional nanocomposites.