A near-infrared driven Ti2O3-TiO2-based photoelectrochemical sensor for detecting ascorbic acid based on the principle of photocurrent polarity reversal

Abstract

Ascorbic acid (AA) is a very common and important antioxidant, widely present in various daily foods, and more importantly, it is an indispensable vitamin in the human body. In this study, a 980 nm near-infrared (NIR)-driven Ti₂O₃-TiO₂-based photoelectrochemical (PEC) sensor was developed for the selective and sensitive detection of AA. Upon 980 nm irradiation, a heterojunction is established between the tetravalent (Ti⁴⁺) and trivalent (Ti⁺) titanium oxides in the Ti₂O₃-TiO₂ photoactive semiconductor. This heterojunction enhances the separation of photogenerated electron-hole pairs and accelerates electron transport. Due to its low redox potential, AA can reduce Ti⁴⁺ to Ti3+, leading to a reversal in the direction of photogenerated electron flow within the semiconductor. The material changes from an n-type semiconductor to a p-type semiconductor, resulting in the phenomenon of photocurrent polarity reversal in PEC only in the presence of AA. At the same time, the sensor has a wide detection range of 1 - 302 μM for AA and the detection limit is 0.43 μM. All of these make it possible to use it for the detection of AA content in real rat cerebrospinal fluid and human plasma, with high recovery rates and low relative standard deviations. This approach holds great potential as an accurate and convenient method for medical detection of AA levels in the human body.