An aldimine condensation reaction based fluorescence enhancement probe for detection of gaseous formaldehyde

Abstract Formaldehyde, a volatile organic compound that is ubiquitous in gas pollutants, has an indelible hazard to the health system of humans. Development of simple and convenient ways for the visual detection of formaldehyde in air is still of importance and challenging. In this paper, we report a new type of fluorescence enhancement probe (FAP), which directly exhibited fluorescence enhancement response to formaldehyde with high sensitivity and selectivity. The FAP was synthesized through the substitution reaction between hydrazine and NBD (7-nitrobenzo-2-oxa-1, 3-diazolyl) chloride, that the hydrazine group acted as both fluorescence quencher based on the photo-induced electron transfer (PET) pathway and reaction triggering factor for selectively recognizing formaldehyde. When the FAP was incubated with a formaldehyde-containing circumstance, Schiff base compound was produced by means of the aldimine condensation reaction which inhibited the PET pathway from hydrazine group to NBD, and thus turned on the fluorescence of the FAP significantly. It is worth mentioning that the FAP showed more remarkable response to formaldehyde under acid conditions. Under the optimal experimental conditions, the FAP responded linearly toward formaldehyde in a wide range of 0.015–0.8 mg•L−1, while the fluorescence enhancement was close to 30 times. This FAP was successfully used to detect gaseous formaldehyde in indoor air.