Colorimetric and Fluorescence Dual-Mode Biosensors Based on Peroxidase-Like Activity of the Co(3)O(4) Nanosheets

The mimic enzyme has become a research hotspot in recent years because of its advantages of high stability, convenient preparation, and low price. In this article, Co(3)O(4) nanosheets synthesized by a simple hydrothermal method possess the characteristics of a peroxidase-like activity. The results demonstrated that 3,3′,5,5′-Tetramethylbenzidine (TMB) could be oxidized by H(2)O(2) to produce a typical blue product (oxTMB) which has a strong absorption at 650 nm wavelength with the help of the Co(3)O(4) nanosheets. Thus, a simple and sensitive colorimetric detection method for H(2)O(2) was established with a good linear relationship (2–200 μM) and a low limit of detection (0.4 μM). Meanwhile, the colorimetric product can effectively quench the fluorescence emitted by Ru(bpy)(3) (2+). Therefore, a colorimetric and fluorescence dual detection mode photochemical sensor for H(2)O(2) detection is constructed based on the principle of the inner filter effect (IFE) between the colorimetric product (oxTMB) and Ru(bpy)(3) (2+). It can effectively avoid the false positive problem of a single detection mode. In the presence of glucose oxidase, glucose can be catalyzed to produce gluconic acid and H(2)O(2); therefore, the sensor can also be used for the determination of glucose with a good linear relationship (0.02–2 μM) and a low limit of detection (5 nM). Experimental results showed that the sensor has a high sensitivity and strong anti-interference ability which can be used for the detection of actual samples.