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 (I0.2:BiOCI0.8) as a photocathode, which can generate the electrical output under visible light irradiation with no external power supply. In addition, the p-type semiconductor I0.2:BiOCI0.8 with a special internal electric field between the iodide ion layer and the [Bi2O2]2+ 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 (•O2-) in the self-powered cathodic PEC system. The further enhanced cathodic photocurrent response can be achieved by eliminating •O2- 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-1 to 50 ng·mL-1) with a low detection limit (25.8 fg·mL-1), which opens up a new horizon of potential for sensitively detecting other kinds of disease markers.