The unique properties of two dimensional (2D) materials make them promising candidates for chemical and biological sensing applications. However, most 2D nanomaterial sensors suffer very long recovery time due to slow molecular desorption at room temperature. Here, we report a highly sensitive molybdenum ditelluride (MoTe ₂ ) gas sensor for NO ₂ and NH ₃ detection with greatly enhanced recovery rate. The effects of gate bias on sensing performance have been systematically studied. It is found that the recovery kinetics can be effectively adjusted by biasing the sensor to different gate voltages. Under the optimum biasing potential, the MoTe ₂ sensor can achieve more than 90% recovery after each sensing cycle well within 10 min at room temperature. The results demonstrate the potential of MoTe ₂ as a promising candidate for high-performance chemical sensors. The idea of exploiting gate bias to adjust molecular desorption kinetics can be readily applied to much wider sensing platforms based on 2D nanomaterials.

Cavity optomechanics allows the parametric coupling of phonon- and photon-modes in microresonators and is presently investigated in a broad variety of solid-state systems. Optomechanics with superfluids has been proposed as a path towards ultra-low optical- and mechanical-dissipation. However, there have been no optomechanics experiments reported with non-solid phases of matter. Direct liquid immersion of optomechanics experiments is challenging, as the acoustic energy simply leaks out to the higher-impedance liquid surrounding the device. Here we confine liquids within hollow resonators to circumvent this issue and to enable optical excitation of mechanical whispering-gallery modes at frequencies ranging from 2 to 11,000 MHz. Our device enables optomechanical investigation with liquids, while light is conventionally coupled from the outer dry side of the capillary, and liquids are provided by means of a standard microfluidic inlet.

We enabled ultrafast, nonvolatile, and reversible band modulation of MoTe ₂ with spatial resolution by optoelectrical activation.