Highly Selective and Sensitive Colorimetric and Fluorimetric Sensor for Cu2

Highly selective, sensitive and biocompatible rhodamine-based isomers for Al3+ detection: A comparative study

Selective detection of a metal ion with high selectivity is of great importance to understand its existence and its role in many chemical and biological processes. We report here the synthesis, characterization and Al3+ sensing properties of two rhodamine-based isomers, (E)-2-((2-(allyloxy)benzylidene)amino)ethyl)-3',6'-bis(ethylamine)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one (L-2-oxy) and (E)-2-((4-(allyloxy)benzylidene)amino)ethyl)-3',6'-bis(ethylamine)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one (L-4-oxy). L-2-oxyand L-4-oxy show pink coloration, significant enhancement in absorbance at 530 nm and fluorescence intensity at 553 nm in the presence of Al3+ among several cations. Quantum yield and lifetime of the probes increase in the presence of Al3+. LOD values have been determined as low as ∼1.0 nM for both the isomers. DFT study suggests that the cation induces opening of spirolactam ring resulting in the changes of the rhodamine dyes. Additional reason could be Chelation Enhanced Fluorescence (CHEF) effect due to the subsequent chelation of the metal ion. Between two isomers, L-2-oxy displays better sensing ability towards Al3+ in terms of fluorescence enhancement, limit of detection, lifetime enhancement. Both the probes have been utilized in cell imaging studies using rat skeletal myoblast cell line (L6 cell line).

SDS-capped 1-pyrenecarboxaldehyde nanoprobe for selective detection of Cu2+ ion from water samples: Spectroscopic approach

Sodium dodecyl sulfate (SDS)-capped 1-pyrenecarboxaldehyde nanoparticles (PyalNPs) were prepared using a reprecipitation method in an aqueous medium and exhibited red-shifted aggregation-induced enhanced emission (AIEE). The dynamic light scattering (DLS) examination showed narrower particle size distribution with an average particle size of 41 nm, whereas -34.5 mV zeta potential value indicate the negative surface charge and good stability of nanoparticles (NPs) in an aqueous medium. The AIEE was seen at λmax  = 473 nm in a fluorescence spectrum of a PyalNP suspension. In the presence of Cu2+ ions, the fluorescence of PyalNPs quenches very significantly, even in the presence of other metal ions like Ba2+ , Ca2+ , Cd2+ , Co2+ , Al3+ , Fe2+ , Hg2+ , Ni2+ and Mg2+ . The changes in the fluorescence lifetime of PyalNPs in the presence of Cu2+ ions suggested that the type of quenching was dynamic. The fluorescence quenching data for the NPs suspension fitted well into a typical Stern-Volmer relationship in the concentration range 1.0-25 μg/ml of Cu2+ ions. The estimated value of the correlation coefficient R2  = 0.9877 was close to 1 and showed the linear relationship between quenching data and Cu2+ ion concentration. The limit of detection (LOD) was found to be 0.94 ng/ml and is far below the tolerable intake limit value of 1.3 μg/ml accepted by the World Health Organization for Cu2+ ions in drinking water. The fluorescence quenching approach for a SDS-capped Pyal nanosuspension for copper ion quantification is of high specificity and coexisting ions were found to interfere very negligibly. The developed method was successfully applied for the estimation of copper ions in river water samples.

A New Reversible Colorimetric Chemosensor Based on Julolidine Moiety for Detecting F. J Fluoresc 2021;31:1675-1682. [PMID: 34387807 DOI: 10.1007/s10895-021-02801-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

We synthesized an original reversible colorimetric chemosensor PDJ ((E)-9-((2-(6-chloropyridazin-3-yl)hydrazono)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol) for the detection of F^-. PDJ displayed a selective colorimetric detection to F^- with a variation of color from colorless to yellow. Limit of detection of PDJ for F^- was calculated as 12.1 µM. The binding mode of PDJ and F^- turned out to be a 1:1 ratio using Job plot. Sensing process of F^- by PDJ was demonstrated by ¹H NMR titration and DFT calculation studies that suggested hydrogen bond interactions followed by deprotonation. Moreover, the practicality of PDJ was demonstrated via a reversible test with TFA (trifluoroacetic acid).

A Rhodamine-based Fluorescent Chemodosimeter for Au3+ in Aqueous Solution and Living Cells

A highly selective rhodamine hydrazide-based fluorescent chemosensor for Au3+ detection was developed. The aqueous solution of rhodamine N-hydroxysemicarbazide (RHS), in the presence of Au3+, exhibited a significant 55-fold turn-on fluorescence response at 591 nm and a colorimetric change from colorless to pink. Other interested ions including Li+, Na+, K+, Cs+, Mg2+, Ca2+, Ba2+, Pb2+, Mn2+, Co2+, Ni2+, Ag+, Cd2+, Cu2+, Hg2+, Zn2+, Sn2+, Fe2+, Fe3+, Cr3+, Ce3+ did not induce any distinct color/spectral changes. The irreversible detection mechanism occurred via Au3+-promoted 5-exo-trig ring closure to yield 1,3,4-oxadiazole-2-one product. The RHS probe is non-responsive to other biologically relevant metal ions and the limit of detection for Au3+ was calculated to be 0.5 µM with a linear range of 0 to 90 µM. Fluorescence bioimaging of Au3+ in HepG2 cells was also successfully demonstrated.

Recent advances (2017-20) inthe detection of copper ion by using fluorescence sensors working through transfer of photo-induced electron (PET), excited-state intramolecular proton (ESIPT) and Förster resonance energy (FRET)

An essential trace element copper plays several physiological roles in living systems. But at excess concentration, it exerts toxicity and becomes associated with numerous disorders. In this article, we have reviewed the recent developments (from 2017 to 2020) in the field of fluorescence-based chemosensors for the detection of Cu²⁺ ion. The sensing probes which were built to work through transfer of photo-induced electron (PET), excited-state intramolecular proton (ESIPT) and Förster resonance energy (FRET) mechanisms have been included in this review. Emphasis is given on the design, sensitivity and response of the probe molecules for the detection of Cu²⁺ ion. Using suitable examples, applications of these three recognition mechanisms for the probing of copper ion have been addressed.