High sensitivity and ultra-low detection limit of violet phosphorus-based formaldehyde gas sensor by ultrasonic-assisted laser ablation

Formaldehyde (HCHO) pollution has emerged as a progressively critical environmental concern, with the detection of formaldehyde at trace levels being an indispensable requirement. Violet phosphorus (VP) nanoplates, recognized as innovative two-dimensional materials, are promising candidates for gas sensing due to their rich active sites and substantial specific surface area. This work pioneered the use of ultrasonic-assisted laser ablation in the synthesis of VP nanoplates. The as-produced VP nanoplates had the lateral dimension of 6.5 μm and the thickness of 2–6 nm (1–5 layers), which was strongly influenced by the ablation techniques employed and the processing parameters. The VP nanoplates demonstrated excellent sensitivity towards formaldehyde: gauge factor is 7.23 × 10⁹; and resistance response is 144.6 % for detecting 20 ppb of formaldehyde. The detection limit is only 3 ppb. This work employed experiments and calculations to study the sensing mechanism. The binding energy between VP/G and HCHO is −1.276 eV, demonstrating the strong chemical adsorption. This paper provided a novel approach to fabricate VP nanoplates with superior formaldehyde sensitivity and ultra-low detection limitation, thereby showcasing significant potential for applications in detecting of air pollution.