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

A highly sensitive, portable, rapid, and accurate colorimetric sensing method is presented. It is based upon exfoliated g-CN nanosheets (E-g-CN NSs), having peroxidase nanozyme-like properties. The as-prepared catalyst (E-g-CN NSs) tends to oxidize the colorless tetramethyl-benzidine (TMB) into oxidized-TMB in the presence of hydrogen peroxide (HO) 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 R 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-CN NSs. For comparison of the catalytic study, we have also explored the sensing mechanism of B-g-CN, using the same optimized experimental conditions. Resultantly, we concluded that the proposed sensor (E-g-CN NSs) will gain considerable attention for on-site environmental and health monitoring in future endeavor.