High-performance photoelectrochemical biosensor with Bi2S3/RuO2 heterojunction cascade multi-tetrahedral DNA nanonet for ultrasensitive lead ions detection.

Herein, a novel signal-off photoelectrochemical (PEC) biosensor was rationally constructed by integrating a Bi2S3/RuO2 heterojunction with the multiple tetrahedral DNA nanonet (mTDN) for ultrasensitive and accurate lead ions detection. This photoactive Bi2S3/RuO2 composite was synthesized through a simple ultrasonic-assisted mixing method, in which the RuO2 not only functioned as an efficient electron conductor and a protective layer for Bi2S3, but also formed a typical p-n heterojunction with Bi2S3, effectively promoting the separation of photogenerated electron-hole pairs for achieving an extremely high initial photocurrent that twelve-times higher than individual component. Afterwards, the present of target lead ions (Pb2+) led to the specific DNAzyme cleavage on electrode, thus exposing abundant binding sites for immobilizing mTDN. Compared with traditional DNA nanostructures, the designed mTDN prone to form a continuous, dense, and uniform three-dimensional rigid network film, and thus endowed the effective obstructing of electronic transfer derived from non-conductive characteristic and spatial steric hindrance, significantly depressing the photocurrent for achieving sensitive and accurate Pb2+ detection. As a result, the proposed PEC biosensor exhibited excellent analytical performance with a low detection limit down to 0.82 fM (S/N = 3), providing a sensitive and reliable approach for environmental pollution monitoring and drinking water safety controlling.