Preparation of ultra-sensitive and selective hydrogen peroxide–based colorimetric sensor using highly exfoliated g-C₃N₄ nanosheets with peroxidase-like activity

A highly sensitive, portable, rapid, and accurate colorimetric sensing method is presented. It is based upon exfoliated g-C₃N₄ nanosheets (E–g-C₃N₄ NSs), having peroxidase nanozyme-like properties. The as-prepared catalyst (E–g-C₃N₄ NSs) tends to oxidize the colorless tetramethyl-benzidine (TMB) into oxidized-TMB in the presence of hydrogen peroxide (H₂O₂) generating a dark blue color and corresponding ultraviolet visible-spectral changes following a Michaelis–Menten kinetic. The prepared colorimetric sensor exhibited response within the range 0.001–0.450 μM having R² value of 0.999 and a detective limit (LOD) of 0.15 ± 0.04 nM. Furthermore, the sensor also displayed outstanding selectivity, ample stability (10 weeks), and excellent practicability in real sample applications. All these outstanding properties were highly attributed to the large surface area with exposed actives sites, high surface energy, and large conductive structure of E–g-C₃N₄ NSs. For comparison of the catalytic study, we have also explored the sensing mechanism of B-g-C₃N₄, using the same optimized experimental conditions. Resultantly, we concluded that the proposed sensor (E–g-C₃N₄ NSs) will gain considerable attention for on-site environmental and health monitoring in future endeavor.