Highly sensitive label-free photoelectrochemical aptasensor based on Cu2MoS4@Ti3C2Tx MXene heterojunction for tetracycline detection in milk

A label-free photoelectrochemical (PEC) biosensing strategy was constructed based on a Cu 2 MoS 4 @Ti 3 C 2 T x MXene heterojunction for the sensitive detection of tetracycline (TC) in milk. The Cu 2 MoS 4 @Ti 3 C 2 T x MXene heterojunction substantially facilitates the separation of photogenerated electron–hole pairs, a key element in enhancing the photocurrent response. Cu 2 MoS 4 , renowned for its visible-light absorption and photocatalytic properties, is combined synergistically with Ti 3 C 2 T x MXene, contributing a large surface area and outstanding electrical conductivity. The heterojunction not only elevates photocatalytic efficiency but also provides abundant π–π stacking sites on the surface of Ti 3 C 2 T x MXene. These sites enable the direct immobilization of the TC aptamer without chemical modification, thereby minimizing marker interference and improving the detection accuracy. Furthermore, the heterojunction structure broadens the light-absorption spectrum and enhances charge-transfer efficiency, resulting in a higher photocurrent response. The proposed PEC aptasensor demonstrates a favorable linear response to TC within the concentration range 5 to 300 nM, with a detection limit of 1.24 nM. These results are comparable to those achieved by high-performance liquid chromatography. This study is expected to pioneer a novel approach for the design of a label-free PEC aptasensor applicable to the bioanalysis of food samples. Graphical abstract