Colorimetric assay based on NiCo(2)S(4)@N,S-rGO nanozyme for sensitive detection of H(2)O(2) and glucose in serum and urine samples

Traditional bimetallic sulfide-based nanomaterials often have a small specific surface area (SSA), low dispersion, and poor conductivity, thereby limiting their wide applications in the nanozyme-catalytic field. To address the above issues, we herein integrated NiCo(2)S(4) with N,S-rGO to fabricate a nanocomposite (NiCo(2)S(4)@N,S-rGO), which showed a stronger peroxidase–mimetic activity than its pristine components. The SSA (155.8 m(2) g(−1)) of NiCo(2)S(4)@N,S-rGO increased by ∼2-fold compared to NiCo(2)S(4) with a pore size of 7–9 nm, thus providing more active sites and charge transfer channels. Based on the Michaelis–Menten equation, the affinity of this nanocomposite increased 40% and 1.1∼10.6-fold compared with NiCo(2)S(4) with N,S-rGO, respectively, highlighting the significant enhancement of the peroxidase-like activity. The enhanced activity of this nanocomposite is derived from the joint participation of ˙OH, ˙O(2)(−), and photogenerated holes (h(+)), and was dominated by h(+). To sum up, N,S-codoping, rich S-vacancies, and multi-valence states for this nanocomposite facilitate electron transfer and accelerate reaction processes. The nanocomposite-based colorimetric sensor gave low detection limits for H(2)O(2) (12 μM) and glucose (0.3 μM). In comparison with the results detected by a common glucose meter, this sensor provided the relative recoveries across the range of 97.4–101.8%, demonstrating its high accuracy. Moreover, it exhibited excellent selectivity for glucose assay with little interference from common co-existing macromolecules/ions, as well as high reusability (>6 times). Collectively, the newly developed colorimetric sensor yields a promising methodology for practical applications in H(2)O(2) and glucose detection with advantages of highly visual resolution, simple operation, convenient use, and satisfactory sensitivity.