Self-deposited ultrasmall Ru nanoparticles on carbon nitride with high peroxidase-mimicking activity for the colorimetric detection of alkaline phosphatase.

Carbon nitride (C3N4) nanosheets are known as peroxidase mimics, but the low activity hinders their further application. Embedding active metal nanoparticles onto the C3N4 nanosheets is expected to break this limitation. Herein, highly dispersed ultrasmall Ru nanoparticles are anchored onto the C3N4 through spontaneous redox reaction. The as-obtained Ru-C3N4 exhibits excellent peroxidase-like activity, which can be further regulated by adjusting the loading of Ru nanoparticles on C3N4. Using Ru-C3N4 as a mimetic peroxidase, a colorimetric sensing method for alkaline phosphatase (ALP) detection is developed based on the inhibitory effect of ascorbic acid produced by hydrolysis of ALP and l-ascorbic acid 2-phosphate (AAP) on the color development reaction of TMB catalyzed by Ru-C3N4. The sensor exhibits wide linear range and low detection limit for the ALP sensing. Finally, the assay is applied to ALP detection in human serum and satisfactory results are obtained, which provides a promising strategy for colorimetric sensing of ALP.