Highly sensitive and selective rGO-LaFeO₃ nanocomposite based formaldehyde sensors towards air quality monitoring

Formaldehyde (HCHO), a ubiquitous volatile organic compound and recognized human carcinogen, is extensively used in industrial applications such as resin and adhesive production. Even minimal exposure to HCHO can induce serious health effects, including respiratory distress and dermal irritation. Thus, the advancement of highly sensitive and selective sensors for HCHO detection is imperative for safeguarding environmental and indoor air quality. Herein, we report the development of a very sensitive, highly selective, and stable HCHO sensor based on reduced graphene oxide (rGO) and lanthanum ferrite (LaFeO₃). LaFeO₃ and rGO-LaFeO₃ nanocomposites with different compositions were synthesized through an affordable and straightforward sol-gel process. Among them, the LFGO(50:1) sensor demonstrated the highest response and selectivity towards HCHO, with a detection limit (theoretically) as low as 19 ppb (1.5 fold). Notably, it exhibited approximately 15-fold p-type response to 1 ppm of HCHO, while operating at 260 °C. The sensor also showed quick response and recovery times of around 1.5 s and 36 s, respectively while having negligible response to other VOCs, including ethanol, methanol, and NH₃. A synergistic effect of rGO and LaFeO₃ is attributed to this improved sensing behavior. rGO offers a large surface area that facilitates the adsorption of HCHO molecules, while LaFeO₃ acts as a catalyst for the oxidation of HCHO. The sensor also showed good selectivity, stability, and reproducibility, making the material a promising candidate for practical applications towards environment monitoring, indoor air quality control, and industrial safety.