Layered Sulfur Nanosheets: From Ultrasensitive Ammonia Detection to High-Performance Pressure Sensing

This work reports on the innovative application of layered sulfur nanosheets (S-NSs) in high-performance ammonia (NH3) sensing and flexible piezoresistive sensing. To address the challenges of precise band structure tailoring in two-dimensional materials and the limited performance enhancement of piezoresistive sensors, we successfully synthesized S-NSs with an optimized band structure via a dual-ligand strategy employing sodium dodecyl benzenesulfonate (SDBS) and bovine serum albumin (BSA). The resulting material exhibited exceptional sensitivity in NH3 detection, achieving a 20-fold enhancement in the response signal to an ultralow NH3 concentration (10 ppt) compared to its single-ligand (BSA) counterpart along with a rapid response (5.2 s) and recovery (3.5 s). More importantly, we pioneered the integration of S-NSs with carbon nanotubes (CNTs) into a polyvinylidene fluoride (PVDF) matrix to construct a ternary “PVDF/CNTs/S-NSs” composite for piezoresistive sensing. This sensor demonstrated a remarkable 100-fold improvement in piezoresistive response relative to the control group without S-NSs, featuring high sensitivity, good linearity (0.3 to 1.4 kPa), a fast response time of as low as 220 ms, and enabling the effective monitoring of a wide range of human motions, including finger tapping, joint movement, and walking. This study not only provides a paradigm for designing ultrasensitive gas sensors through ligand engineering but also pioneeringly demonstrates the vast potential of S-NSs as a versatile nanomaterial for achieving cross-modal sensing capabilities, paving a material pathway for the development of next-generation flexible electronics.