In situ growth of TiO 2 /Ti 3 C 2 MXene Schottky heterojunction as a highly sensitive photoelectrochemical biosensor for DNA detection.

In this work, a heterojunction composed of a TiO 2 nanosheet and layered Ti 3 C 2 was synthesized by directly growing TiO 2 in Ti 3 C 2 MXene. Compared with pure TiO 2 , TiO 2 /Ti 3 C 2 composites had increased surface area, and a light absorption range that extended from ultraviolet to visible light, which greatly extended the life of photogenerated carriers. A photoelectrochemical biosensor for DNA detection was constructed based on the TiO 2 /Ti 3 C 2 heterogeneous structure, which was comprehensively studied based on photocurrent responses. In the absence of the target, the CdSe QDs were close to the surface of the electrode, resulting in enhanced sensitization and increased photocurrent. In the presence of the target, the photocurrent decreases due to the formation of rigid double strands with the probe DNA, which caused the CdSe QDs to be far away from the electrode surface. The sensor had stability and sensitivity for DNA detection in the range of 10 nM-10 fM, and the lower detection limit was 6 fM. Its outstanding characteristics also provided ideas for detecting various other target DNA for early diagnosis of various diseases.