Selective turn-on fluorescence detection of formaldehyde in the gas phase

Reliable detection of formaldehyde in gas phase still remains a challenge regarding either sensitivity or selectivity or both. In this study we report on a simple, unique sensor composite, which enables efficient detection of gaseous formaldehyde with both low limit of detection (LOD) and extremely high selectivity. The primary components of the sensor composite include a hydroxylamine sulfuric acid salt ((NH2OH)(2)center dot H2SO4) and a fluorescence turn-on probe, which both are coated within the porous matrix of a cellulose plate. The fluorescence probe is based on a perylene diimide (PDI) molecule modified with an aniline group, which is non-fluorescent in its pristine state due to the photoinduced intramolecular electron transfer. Upon interaction with formaldehyde, the hydroxylamine salt will be converted to the corresponding Schiff base through aldimine condensation, releasing the sulfuric acid. The acid released will protonate the aniline group on PDI, resulting in a quick fluorescence turn-on. By measuring the fluorescence increase we can detect formaldehyde both quantitatively and specifically. Under the optimized condition, the sensor demonstrated a LOD of 3.7 ppb, which is much lower than the air quality threshold set by WHO. The sensor was also proven highly selective towards formaldehyde, with negligible response towards other common chemicals. The work reported will not only provide a new sensor for formaldehyde, but moreover open a unique design pathway for sensor composite that combines reactive components with various fluorescence indicators so as to enable highly efficient detection of many other air pollutants and toxic chemicals.

Automated summary

In this study, a simple and unique sensor composite was created for efficient detection of gaseous formaldehyde with low limit of detection and high selectivity. The sensor composite consists of a hydroxylamine sulfuric acid salt and a fluorescence turn-on probe coated within a porous cellulose plate. By measuring the fluorescence increase, formaldehyde can be detected quantitatively and specifically. This work not only provides a new sensor for formaldehyde, but also opens up a new design pathway for sensor composites to detect other air pollutants and toxic chemicals.