A facile method for the alkylation of fluorene achieved via direct C-H alkylation under aqueous conditions is reported, wherein the formation of fluorenone is inhibited, resulting in the exclusive formation of the desired dialkyl-substituted fluorene monomer. As a proof of concept, this method has also been successfully extended to perform N-alkylation of carbazole, diphenylamine, and N,N-dialkylation of aniline in high yields.
The synthesis and application of a neutral polymer, poly(1,4-bis-(8-imidazole-octyloxy)-benzene) (PPI), is performed by economical and simple reaction steps. The PPI polymer demonstrates exemplary activity to be used as a film on a TLC plate, or as a membrane by blending it with a desired polymer or in a solution phase to detect fluoride anions from contaminated water in the presence of competing anions at ppb levels easily and rapidly. This polymer PPI works on the simple displacement principle where fluorescence turn-on/turn-off are observed as signals. On selectively binding Cu 2+ it displays extraordinary fluorescence quenching, resulting in >97% reduction in the fluorescence intensity. This effect could be visualized in solution phase, on a TLC plate and on a blended polymer membrane. Furthermore, the fluorescence of this PPI-Cu 2+ assay showed 81% enhancement on selectively binding F À anions in contaminated water in the presence of other competing anions with higher positive free energies of hydration. Polymeric systems with such robust fluorescence dequenching activity are novel, providing a unique platform for detection and possible removal of fluoride anions. To validate this potential, two experiments were performed: (a) preparation of a film on a TLC plate and (b) preparation of a membrane by mixing 1% PPI in polystyrene and casting as a membrane film of desired shape and thickness. Our results confirm that PPI-Cu 2+ films and membranes described above have the highest specific activity to sense fluoride in a competitive environment, observed by the unique enhancements in fluorescence intensities at varying and extremely low quantities of 1 ppm, 10 ppm and 50 ppm of fluoride. The detection limit of fluoride in contaminated water for the TLC plate and membrane methods was very low and was in the range of 2.5-10.0 ppb. We have further used these methods for the detection of fluoride in natural ground water samples and ascertained the percentage of fluoride.
A neutral polyfluorene derivative, poly(9,9-bis(6′-benzimidazole)hexyl) fluorene-alt-1,4-phenylene (PBP), is synthesized and well characterized by 1H NMR, 13C NMR, and GPC. PBP exhibits exemplary activity as noninvasive fluorescence sensor and accomplishes in situ monitoring of important biological targets like Fe3+ and inorganic phosphates in saliva. On binding Fe3+, the fluorescence of PBP is quenched by 97% in label free conditions. The fluorescence of PBP is regained back on adding inorganic phosphate with a fluorescence enhancement of 106% due to the displacement of Fe3+ from the PBP. This PBP assay is further used to detect and estimate inorganic phosphate in fresh saliva samples which is also able to enhance the fluorescence by >94%. This ability of PBP to accomplish in situ monitoring and estimation of indispensable biological targets like Fe3+ and inorganic phosphates rapidly, at very low concentration with very high selectivity corroborates the extension of this assay system for safe clinical applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.