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Intriguing Manipulation of Metal‐Enhanced Fluorescence for the Detection of Cu II and Cysteine
Author(s) -
Ganguly Mainak,
Pal Jaya,
Mondal Chanchal,
Pal Anjali,
Pal Tarasankar
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402505
Subject(s) - fluorescence , chemistry , cysteine , photochemistry , salicylaldehyde , quenching (fluorescence) , fluorophore , tryptophan , metal ions in aqueous solution , metal , inorganic chemistry , amino acid , crystallography , organic chemistry , biochemistry , physics , schiff base , quantum mechanics , enzyme
Commercially available salicylaldehyde, in alkaline medium, exhibits strong fluorescence after one hour of UV exposure in the presence of Ag I . The phenolic group of salicylaldehyde is converted into the quinone form under alkaline conditions in the presence of AgNO 3 , resulting in aggregated Ag(0), which causes approximately 250 times fluorescence enhancement of the in situ produced quinone. Such high silver‐enhanced‐fluorescence (SEF) is selectively quenched by cysteine, arginine, histidine, methionine, and tryptophan. In contrast to the other amino acids, ageing brings selectivity of the cysteine‐induced quenching effect. Interestingly, Cu II is found to be the only metal ion that exclusively regenerates the lost fluorescence. Thus, quenching and recovery of fluorescence (Turn Off/On) can be used for the selective and sensitive detection of cysteine as well as Cu II ions in one pot. Alteration of the electric field density around the fluorophore (lightening rod effect) and scattering/absorption cross‐section have been proposed to account for the Off/On fluorescence.