H2O2-induced photocurrent polarity reversal of chitosan stabilized I-BiOBr/CuS composite heterojunction for highly sensitive cholesterol detection.

Photocurrent polarity reversal reflects a crucial switching procedure between the anode and cathode paths, which is important for the eradication of false-positive signals and the enhancement of the detection sensitivity and reliability of photoelectrochemical (PEC) sensors. Herein, we constructed a PEC biosensor which exhibited excellent H₂O₂-induced photocurrent polarity reversal properties. In the sensor chitosan stabilized I-BiOBr/CuS semiconductor heterojunction was employed as the photosensitive material, which exhibited large cathode photocurrent. Upon the introduction of H₂O₂ the photocurrent polarity reversed due to the change of PEC mechanism. As an application proof of the mechanism, cholesterol was coupled with cholesterol oxidase to produce H₂O₂. The reversal photocurrent increased with increasing cholesterol concentration, achieving sensitive and selective PEC detection of cholesterol. Under the selected conditions, the PEC sensor showed a detection limit as low as 0.21 μM, a broad linear range and high stability. Moreover, the measurement results of actual samples were comparable to those of commercial cholesterol detection tool. Hence, it was promising in clinical diagnosis.