Water molecule-triggered anisotropic deformation of carbon nitride nanoribbons enabling contactless respiratory inspection

Abstract

The exploitation of the interaction between nanostructured matter and small molecules, such as H2O at interfaces via dynamic hydrogen bonding, is essentially the key for smart, responsive nanodevices but remains challenging. Herein, the authors report that the carbon nitride nanoribbons (CNNRs) with an anisotropic intraplanar and interplanar molecular arrangement underwent a deformation by H2O triggering. Both experiments of bulk samples and single nanoribbons disclosed that the reversible formation of a hydrogen-bonded H2O adsorption layer was the source of the CNNRs deformation, reminiscent of the hydration-triggered twist of natural bean pods in seeding. Nonetheless, CNNRs had a more balanced H2O affinity, enabling a superior response and recovery time. By coupling with carbon nanotubes, the authors also converted the deformation of CNNRs into more straightforward electrical readouts with record-fast response time. Further applied to capture fluctuations in humidity in real-time respiration, a higher detection sensitivity was obtained in a contactless mode, which compared favorably with the clinical breath-testing station. Given the carbon nitride family with various C/N ratios, surface properties, and topography, this finding that CNNRs are an outstanding H2O transducer would significantly pave the way for the H2O-triggered smart devices in broad prospective applications.