ABSTRACT
In this study, four polyureas with triazine moiety (PUAs) were successfully synthesized through the polymerization of triazine-containing diamine and diisocyanate. The intramolecular aggregation of triazine rings and urea groups along the macromolecular backbone gives PUAs a significant polymerization-induced emission (PIE). Among the four PUAs, PUA-LP shows a significant fluorescent emission at 450 nm, compared to non/weak fluorescent 2,4-diamino-6-phenyl-1,3,5-triazine and L-Lysine diisocyanate ethyl ester monomers. Additionally, the external factors such as solution concentration, excitation wavelength, and precipitants also play a crucial role in the fluorescence of PUAs. As expected, PUA-LP can selectively recognize and detect Fe3+/Fe2+ ions even in the presence of 12 other metal ions and 10 anions. The limit of detection of PUA-LP to Fe3+/Fe2+ is as low as 1.02 µM (0.06 mg/L) and 0.86 µM (0.05 mg/L), respectively, and far below 0.3 mg/L of the allowable national standard for drinking water by WHO. Furthermore, the quenching mechanism of Fe3+/Fe2+ to PUA-LP is attributed to static quenching caused by the coordination of Fe3+/Fe2+ ions with a coordination ratio of 2:1. Based on PIE, the fluorescent PUA-LP was made into an observable and portable testing paper for detecting Fe3+/Fe2+ ions. Finally, we measured the recovery rate of the actual tap water samples and compared the performance of PIE-active PUA-LP with the other reported fluorescent probes to Fe3+/Fe2+ ions.
ABSTRACT
In this work, three morpholine-modified polyacrylamide derivatives (MMPAm) were successfully prepared by free radical polymerization of monomers with morpholine moiety. The intramolecular aggregation of morpholine rings on macromolecular backbone gives MMPAm a significant polymerization-induced emission (PIE). Particularly, poly(N-morpholine acrylamide) (PNMPA) has the characteristics of strong fluorescence at 450 nm, and its fluorescence quantum yield reaches 2.87 %. The introduction of morpholine moiety, the length of CH2 spacer between morpholine ring and the backbone and the molecular weight play the important roles in PIE properties of PNMPA. Interestingly, PNMPA can recognize and detect Cu2+ specifically even in the presence of 12 other metal ions by thorough fluorescence quenching, and the detection limit of PNMPA is 17.3 µM. Furthermore, the dynamic quenching of PNMPA by Cu2+ ions and the complexation ratio of 1:2 according to JOB's working diagram were confirmed by fluorescence titration. Under the assistance of EDTA, a reversible detection system for Cu2+ is achieved, and a portable test paper from PNMPA for the detection of Cu2+ was also made. In conclusion, PNMPA is endowed with a significant PIE effect by the intramolecular aggregation of morpholine rings along the backbone in the polymerization of non-fluorescent monomer, and is expected to be a promising material for specific detection to Cu2+ ions.
ABSTRACT
Species of Cosmocerca Diesing, 1861 (Ascaridomorpha: Cosmocercoidea), are common nematode parasites of amphibians. In the present study, a new species of Cosmocerca, namely C. simile n. sp., was described using light and scanning electron microscopy, and sequencing different nuclear and mitochondrial genetic markers (i.e. small ribosomal DNA (18S), large ribosomal DNA (28S), internal transcribed spacer (ITS) and cytochrome c oxidase subunit 1 (cox1)). Cosmocerca simile n. sp. differs from its congeners based on body size, morphology and number of plectanes, relative length of spicules and gubernaculum and spicules to total body length and morphology and length of tail. Molecular analysis showed no nucleotide polymorphisms among different individuals of the new species regarding nuclear DNA. Very low intraspecific nucleotide variation (0.52-0.78%) was detected in cox1 mtDNA. In contrast, the level of interspecific nucleotide variation between C. simile n. sp. and its congeners were distinctly higher (2.74-18.1% in the partial ITS region and 10.2-13.5% in the partial cox1 region, respectively) than that of intraspecific variation. Phylogenetic analyses using maximum likelihood (ML) inference based on the partial ITS and cox1 sequence data both supported the new species to be a member of the genus Cosmocerca, and formed a sister relationship to C. japonica. The newly obtained genetic data are important for further studies of DNA-based taxonomy, population genetics and phylogenetics of the Cosmocercoidea.
