Functionalized carbon nanoparticles for smartphone-based sensing of formaldehyde.

Formaldehyde (FA) is a volatile organic compound of significant environmental and health concern due to its toxicity and widespread presence in indoor and industrial settings. The development of sensitive, selective, and user-friendly detection systems for FA is therefore of critical importance. In this work, we report a novel fluorescent nanosensor based on carbon nanoparticles functionalized with dopamine for the detection of FA in both aqueous and gaseous phases. The system achieved remarkable limits of detection-87 ppb in water and 10 ppb in air-well below the safety thresholds recommended by the World Health Organization. The sensing performance arises not only from the intrinsic photophysical properties of the carbon core but also from its architecture, which allows the anchoring of multiple recognition sites on a single nanoparticle. This multivalent interaction strategy increases the likelihood of FA binding events, enhancing both sensitivity and selectivity. Computational analysis supports the central role of the nanoparticle in the recognition process. The sensor operates effectively in solution and the solid state, and its compatibility with smartphone-based detection paves the way for the development of portable, low-cost devices for real-time FA monitoring.