Selective detection of paraquat by a cucurbit[7]uril-based fluorescent probe.

A simple fluorescent "on-off" system that can be utilized for the selective identification and determination of paraquat (PQ) is presented herein. 1H NMR spectroscopic data indicated that in aqueous solution the alkaloid palmatine can be partially encapsulated within the cucurbit[7]uril (Q[7]) cavity, whereby a stable 1 : 1 host-guest inclusion complex is formed. Other characterization techniques including mass spectrometry, UV-Vis and fluorescence spectroscopy also provided further evidence, and the host-guest inclusion complex was found to exhibit reasonable fluorescence intensity. It is noteworthy that the addition of PQ resulted in quenching the fluorescence of the host-guest inclusion complex, whereas the presence of 12 other pesticides did not significantly affect the fluorescence intensity. Given the linear relationship between the intensity of the fluorescence and the PQ concentration, the PQ concentration in aqueous solution was easily detected. Thus, a new method for identifying and determining the fluorescence quenching of PQ has been developed in this work.

Facile fluorescent detection of o-nitrophenol by a cucurbit[8]uril-based supramolecular assembly in aqueous media.

The efficient and selective detection of isomers is an attractive but challenging area. In this study, a supramolecular fluorescent probe based on cucurbit[8]uril (Q[8]) and a pyrene-based derivative (G) was prepared, which effectively recognized and removed o-nitrophenol (o-NP) from a mixture of nitrophenol isomers. The newly designed probe G@Q[8] was characterized by NMR spectroscopy, fluorescence emission and UV-Vis spectroscopy, and its host-guest properties in aqueous solution were investigated. The results revealed that the system forms a stable inclusion complex with a stoichiometric ratio of 1:1, which was accompanied by a distinct fluorescence enhancement of G. Moreover, it was employed for the rapid detection of nitrophenol isomers where o-NP showed a dramatical quenching efficiency with a detection limit of 1.53 × 10-7 mol·L-1. This highly efficient supramolecular fluorescent probe offers a new strategy for the convenient detection and removal of o-NP from mixtures in aqueous medium.

Cucurbit[10]uril-mediated Supramolecular Assembly for Optically Tunable Dimers and Near White-light Emissive Materials.

Cucurbit[10]uril (Q[10]), the cucurbit[n]uril with a large cavity, exhibits several new features in the development of the host-guest complex. Thus, based on Q[10] and π-conjugated molecule, oligo(p-phenylenevinylene) derivative (OPVCOOH), the host-guest complexes with three different interaction ratios of 1 : 2, 2 : 2, and 3 : 2 assemblies (Q[10]: guest) were fabricated. Depending on the host/guest ratio, the emission color of these complexes ranged from blue to yellow-green. The extra Fe2+ coordinated with a bare carboxyl group of the Q[10]-OPVCOOH (3 : 2) assembly, obstructing its rotaxane structure and forming Q[10]-OPVCOOH-Fe2+ assembly, which may be used as a coating for near-white LED bulbs.

A fluorescent probe based on cucurbit[7]uril for the selective recognition of phenylalanine.

Herein we describe a simple fluorescence quenching method for the selective recognition and determination of the amino acid phenylalanine (Phe). The use of 1H NMR spectroscopy revealed that the alkaloid palmatine (PAL) can encapsulated partially into the cavity of cucurbit[7]uril (Q[7]) in aqueous solution to form a stable 1:1 host-guest inclusion complex. This host-guest complex exhibits fluorescence of moderate intensity. Interestingly, the addition of the Phe results in a dramatic quenching of the fluorescence intensity associated with the inclusion complex. By contrast, the addition of other natural amino acids resulted in no change in the fluorescence. Based on the linear relationship between the fluorescence intensity and the concentration of Phe, the detection of the concentration of Phe in aqueous solution is facile. Thus, a new fluorescence quenching method for the recognition and determination of the Phe has established herein.

Selective recognition and determination of phenylalanine by a fluorescent probe based on cucurbit[8]uril and palmatine.

This paper demonstrated a simple and validated fluorescence enhancing method to selectively recognize and discriminate the amino acid phenylalanine (Phe). 1H NMR spectroscopy reveal that the palmatine (PAL) can be encapsulated into the cucurbit [8]uril (Q [8]) in aqueous solution to form stable 1:2 host-guest inclusion complex PAL2@Q [8], which exhibits moderate intensity fluorescence property. Interestingly, the addition of the Phe into the inclusion complex PAL2@Q [8] leads to dramatically enhancing of the fluorescence intensity. In contrast, the addition of any other natural amino acids into the inclusion complex PAL2@Q [8] gives no fluorescence variation. Furthermore, it is easy to detect the concentration of Phe in target aqueous solution according to the linear relationship between fluorescence intensity and concentration of the Phe.