Intriguing Manipulation of Metal‐Enhanced Fluorescence for the Detection of Cu^II and Cysteine

Abstract

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 AgNO3 , 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.

Metal‐Enhanced Fluorescence due to Salicylaldehyde‐Silver Nanoparticle Interactions for Fe3+ Sensing

“…Ganguly et al [5] reported silver-enhanced fluorescence (SEF) previously from SL with the exposure of UV light and Cu 2 + was sensed selectively employing fluorescence enhancement of the (SEF + Cysteine) system. In our present work, we sensed Fe 3 + selectively and sensitively using SEF hydrosol with fluorescence quenching.…”

“…Diiminic Schiff bases were designed by Ganguly et al [4–7] . to exhibit silver and copper‐enhanced fluorescence.…”

“…Such activities are termed as metalenhanced fluorescence (MEF). [2][3][4][5][6][7] Diiminic Schiff bases were designed by Ganguly et al [4][5][6][7] to exhibit silver and copper-enhanced fluorescence. Various toxic and important molecules were detected based on turn-on and turn-off fluorescence.…”

Designing an “Off–On” Fluorescence Sensor Based on Cluster-Based CaII-Metal–Organic Frameworks for Detection of l-Cysteine in Biological Fluids

“…Excess of l -cysteine in human blood can lead to a higher risk of coronary heart disease, peripheral diseases, and stroke. On the contrary, the deficiency of l -cysteine may give rise to hair depigmentation, weakness and edema, muscle and fat loss, skin lesions, sluggish growth, and liver damage. − Thus, the development of fluorescence sensors for l -cysteine determination has become quite desirable in diagnosis of some diseases.…”

Encapsulation of Dual‐Emitting Fluorescent Magnetic Nanoprobe in Metal‐Organic Frameworks for Ultrasensitive Ratiometric Detection of Cu2+

“…Based on the sensitivity and simplicity of the fluorescence technique, a number of ion induced fluorescence probes, including quantum dots (QDs), small molecules, and noble metals for detection of Cu 2+ have become more and more interesting. However, these probes also have some disadvantages, for instance, poor water solubility, low detection sensitivity, easy photo‐bleaching, toxicity of QDs, and the high price of noble metals, which seriously affected their application .…”