Self-assembled nano-particles of chitosan amphiphilic derivative for formaldehyde fluorescent detection and its application in test strips.

Excessive levels of formaldehyde (FA) represent serious health risks. Aiming at the detection of formaldehyde content, this paper proposes a self-assembly method of proportional nanoprobes. Spherical nanoparticles (NPs) were prepared by one-step condensation reaction between rhodamine B (RhB) and chitosan (CS). After CS was modified by RhB, the linear structure changed and self-assembled under the action of "hydrophilic/hydrophobic" to form a core-shell structure with a cavity structure. The hydrophobic small molecule probe N-Butyl-4-Hydrazo-1,8-Naphacticimide (NBHN) spontaneously entered into the hydrophobic cavity to form spherical particles Chitosan-Rhodamine B@N-Butyl-4-Hydrazo-1,8-Naphacticimide (CS-RhB@NBHN) with a size of about 60 nm. The hydroxyl groups on CS enrich formaldehyde through charge interaction, and promote the reaction of formaldehyde with NBHN, so that the probe can detect formaldehyde at a lower concentration (detection limit 87 nmol·L-1). The self-assembled CS-RhB@NBHN nanoparticles significantly increased the response speed of NBHN (from 30 min to 10 min). After the reaction of NBHN with formaldehyde, the PET effect is released, the fluorescence transition from red to yellow of CS-RhB@NBHN, and the visual fluorescence response effect to formaldehyde is significantly improved. With the help of smartphone color recognition software, we converted the color of the probe solution into RGB values to realize the quantitative and visual detection of formaldehyde. In addition, CS-RhB@NBHN was used for the detection of FA in leather and air.