Self-Powered Cathodic Photoelectrochemical Aptasensor Comprising a Photocathode and a Photoanode in Microfluidic Analysis Systems.

An intriguing self-powered cathodic photoelectrochemical (PEC) microfluidic aptasensor with enhanced cathodic photocurrent response is proposed for sensitive detection of prostate-specific antigen (PSA). The self-powered system is constructed by a cadmium sulfide-sensitized zinc oxide nanorod array (CdS/ZnO NA) as a photoanode with an iodide-doped bismuth oxychloride flower-array (I:BiOCI) as a photocathode, which can generate the electrical output under visible light irradiation with no external power supply. In addition, the p-type semiconductor I:BiOCI with a special internal electric field between the iodide ion layer and the [BiO] layer could increase the cathodic photocurrent response by facilitating the separation of electron/hole pairs under visible light excitation. It is worth noting that dissolved oxygen as an electron acceptor can be reduced by the photogenerated electron to form a superoxide radical (O) in the self-powered cathodic PEC system. The further enhanced cathodic photocurrent response can be achieved by eliminating O that reacts with the luminol anion radical (L) to produce chemiluminescence emission, which serves as an inner excitation light source. What is more exciting is that the integration of the photoanode and the photocathode into a microfluidic chip could realize automatic sample injection and detection. On this basis, the proposed aptasensor presents excellent reproducibility and high sensitivity for detecting PSA and exhibits a good linearity range (50 fg·mL to 50 ng·mL) with a low detection limit (25.8 fg·mL), which opens up a new horizon of potential for sensitively detecting other kinds of disease markers.