Fully Flexible WSe2/V2C MXene Heterostructure-based Gas Sensor: a detailed Sensing Analysis for ppb level Detection of Ammonia at Room Temperature

Abstract

Designing a robust room temperature gas sensor has become indispensable in the new era for environmental and health monitoring. However, achieving high sensitivity and stability for ammonia detection at ambient conditions remains a significant challenge. In this work, we present a novel p-p type heterostructure-based flexible gas sensor comprising two-dimensional (2D) V₂C MXene nanosheets and WSe₂ nanoparticles on PET substrate. The composite is synthesized via an electrostatic self-assembly technique. A comprehensive morphological investigation utilizing FESEM and TEM reveals the WSe₂ nanoparticles are uniformly anchored on the large specific surface of mesoporous 2D layered V₂C MXene sheet as evaluated by BET. The increased I_D/I_G ratio (1.01) in Raman analysis suggests more number of surface defects present on the WSe₂/V₂C MXene heterostructure as compared to bare V₂C MXene (I_D/I_G = 0.98), which was further confirmed by XPS analysis (O_c% = 15.76%). The heterostructure achieves ultra-high sensitivity (131%) to ammonia at 2.78 ppm, significantly outperforming pristine WSe₂ (13.2%) and V₂C MXene (52.81%). It also exhibits excellent linearity over a wide range (187 ppb to 23.4 ppm), a remarkably low detection limit (178 ppb), and long-term stability (up to 60 days). Moreover, it is seen that the composite sensor shows better selectivity towards oxygen-containing VOCs as compared to the hydrocarbon-based VOCs because of the stronger interaction of polar groups with the surface of the sensor. These results underscore the potential of this sensor for practical applications in medical diagnostics, industrial monitoring, and agricultural sectors. A detailed sensing mechanism is also proposed to elucidate the role of surface defects and heterojunction effects in enhancing performance.