title: Visual Recognition of Aliphatic and Aromatic Amines Using a Fluorescent Gel: Application of a Sonication-Triggered Organogel.
abstract: A naphthalimide-based fluorescent gelator (N1) containing an alkenyl group has been designed and characterized. This material is able to gelate alcohols via a precipitate-to-gel transformation when triggered with ultrasound for less than 2 min (S-gel). The gelation process in n-propanol was studied by means of absorption, fluorescence, and IR spectra, scanning electron microscopy (SEM) images, and X-ray diffraction patterns. The fluorescence intensity of N1 decreased during the gelation process in a linear relationship with the sonication time. The S-gel of N1 could be used to sense aliphatic and aromatic amines by measuring the change in the signal output. For example, the addition of propylamine to the S-gel of N1 resulted in a dramatic enhancement of the fluorescence intensity, accompanied by a gel-to-sol transition. On the contrary, when the S-gel of N1 was treated with aromatic amines such as aniline, fluorescence was quenched and there was no gel collapse. The sensing mechanisms were studied by (1)H NMR, small-angle X-ray scattering, SEM and spectroscopic experiments. It is proposed that isomerization of the alkenyl group of N1 from the trans to cis form occurs when the S-gel is treated with propylamine, resulting in a gel-sol transition. However, the aromatic aniline molecules prefer to insert into the gel networks of N1 via hydrogen-bonding and charge-transfer interactions, maintaining the gel state. As potential applications, testing strips of N1 were prepared to detect aniline.
authors.affiliation: †College of Science and Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Yuhua Road 70, Shijiazhuang 050080, PR China.
authors.forename: Xuelei
authors.initials: X
authors.lastname: Pang
authors.affiliation: †College of Science and Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Yuhua Road 70, Shijiazhuang 050080, PR China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Yu
authors.affiliation: ‡Department of Chemistry and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, 220 Handan Road, Shanghai 200433, China.
authors.forename: Haichuang
authors.initials: H
authors.lastname: Lan
authors.affiliation: †College of Science and Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Yuhua Road 70, Shijiazhuang 050080, PR China.
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Ge
authors.affiliation: †College of Science and Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Yuhua Road 70, Shijiazhuang 050080, PR China.
authors.forename: Yajuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: †College of Science and Hebei Research Center of Pharmaceutical and Chemical Engineering, Hebei University of Science and Technology, Yuhua Road 70, Shijiazhuang 050080, PR China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Zhen
authors.affiliation: ‡Department of Chemistry and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, 220 Handan Road, Shanghai 200433, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Yi
keywords: amine sensor; fluorescence; naphthalimide; organogel; supramolecular chemistry; ultrasound