Selective Detection of NH Gas by TiCT Sensors with the PVDF-ZIF-67 Overlayer at Room Temperature.

In the realm of NH gas-sensing applications, the electrically conductive nature of TiCT MXene, adorned with surface terminations such as -O and -OH groups, renders it a compelling material. However, the inherent challenges of atmospheric instability and selectivity in the presence of gas mixtures have prompted the exploration of innovative solutions. This work introduces a strategic solution through the deposition of a mixed-matrix membrane (MMM) composed of poly(vinylidene fluoride) (PVDF) as the matrix and zeolitic imidazolate framework-67 (ZIF-67) as the filler. This composite membrane acts as a selective filter, permitting the passage of a specific gas, namely NH. Leveraging the hydrophobic and chemically inert nature of PVDF, the MMM enhances the atmospheric stability of TiCT by impeding water molecules from interacting with the MXene. Furthermore, ZIF-67 is selective to NH gas via acid-base interactions within the zeolite group and selective pore size. The TiCT sensor embedded in the MMM filter exhibits a modest 1.3% change in the sensing response to 25 ppm of NH gas compared to the response without the filter. This result underscores the filter's effectiveness in conferring selectivity and diffusivity, particularly at 35% relative humidity (RH) and 25 °C. Crucially, the hydrophobic attributes of PVDF impart heightened stability to the TiCT sensor even amidst varying RH conditions. These results not only demonstrate effective NH detection but also highlight the sensor's adaptability to diverse environmental conditions, offering promising prospects for practical applications.