Elimination of oxygen interference in the photoelectrochemical sensor with ferricyanide shield oxygen reduction for point of care testing

As a sensitive and promising detection method, photoelectrochemical (PEC) sensor has been widely used in biochemical analysis field. However, the interferences from environment, especially dissolved oxygen, often impact the stability and precision of PEC sensors, which limit its practical applications. Here, we report a dissolved oxygen insensitive PEC sensor based on a proposed indirect electron transfer model. Through the detailed study of the charge transfer process, we determined that the photocurrent mainly comes from the electrochemical reaction between the photochemical products and the electrode, rather than direct charge transfer between the photoelectric materials and the electrode. The newly designed PEC sensor used ferricyanide to shield oxygen reduction and eliminated the influence from variable oxygen solubility. This sensor maintained robust responses over an extremely wide range (1.0-7.5 mg/L) of dissolved oxygen concentrations. To further demonstrate its capability, a smartphone based portable immunosensor was constructed for the detection of human serum albumin (HSA), which exhibited excellent stability and accuracy. The relative error of current was reduced by 81.3% over traditional electron donor solution. This work effectively improves the stability of PEC sensors, and lays the foundation for the subsequently practical applications of PEC sensor in point-of-care testing.