Label‐Free and Low‐Power Driven Cancer Biomarker Detection Enabled by 2D Hexagonal Titanium Oxide

Abstract 2D nanomaterials have shown significant advances in next‐generation biosensor development. However, current 2D‐enabled electronic biosensors rarely achieve a detection limit down to pico‐gram level, possibly due to their intrinsic low carrier mobilities, biocompatibility or instability. TiO 2 , a biocompatible material, has been widely adopted in bio‐applications. Recently, 2D TiO 2 with a unique planar hexagonal phase exhibits a reduced bandgap of 2 eV and high p‐type mobility. A small perturbation could stimulate an observable electronic swing, enabling a high‐performance biosensor in a label‐free manner. Here, 2D h‐TiO 2 is fabricated into a liquid‐gated field‐effect transistor, while a wide spectrum, nonspecific biomarker carcinoembryonic antigen (CEA) is selected as the target molecule. The h‐TiO 2 surface is first functionalized with 3‐aminopropyltriethoxysilane and subsequently decorated with anti‐CEA, creating an affinity probe toward CEA molecules. The real‐time response to different concentrations of CEA is tested from 1 pg mL −1 to 10 ng mL −1 under a low working voltage of 0.05 V, and an ultralow detection limit of 0.22 pg mL −1 is achieved. Meanwhile, the selectivity of the devices is demonstrated using cytokeratin‐19‐fragment and neuron‐specific enolase. The results highlight the potential of layered hexagonal metal oxides for high‐performance biosensors, enabling future low‐power portable devices for disease diagnosis.