A highly selective fluorescence and absorption sensor for rapid recognition and detection of Cu2+ ion in aqueous solution and film

A Fluorescent Chemosensor for Detection pH and Cu2+ Ion Base on 7-((2-Aminoethyl)amino)-5-Bromo-6-Hydroxy-1-Methylquinolin-1-ium-3-Sulfonate: Experimental and DFT Calculation

A quinoline derivative 7-((2-aminoethyl)amino)-5-bromo-6-hydroxy-1-methylquinolin-1-ium-3-sulfonate (QEt) containing quinoline ring, -[Formula: see text] sulfonate, -OH phenol, and amine groups was synthesized and studied luminescence properties. The aqueous solutions QEt 10µM change luminescence color from green (λem = 490 nm) to yellow (λem = 563 nm) as increasing pH and the intensity at a peak of 563 nm is linearly proportional with pH value in the range of pH = 3,0-4,0. The QEt solution can be used as a chemosensor for Cu2+ with an LOD value at 0.66 [Formula: see text]. Along with the experiment, the structure, absorption and emission spectra of QEt have been investigated by TD-DFT calculation. The result shows that the absorption band centered at 420 nm is due to the electron transition from HOMO to LUMO (π → π*). The results also help to assign emission band centered at 490 nm is due to the S1 → S0 transition (LUMO → HOMO singlet transition), at 563 nm is due to the T1 → S0 transition (LUMO → HOMO triplet transition). The dependence of the relative intensity of each emission peak on pH, which is experimentally recorded, is explained based on the results of theoretical TD-DFT calculation.

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 Bifunctional Fluorescence Probe Based on AIE-ICT Strategy for Visual Detection of Cu2+/Co2+ in Complex Matrix

A novel fluorescence chemical sensor-based probe 1-{[(E)-(2-aminophenyl)azanylidene]methyl}naphthalen-2-ol (AMN) was designed and synthesized, which performed a "naked eye" detection ability toward Cu²⁺ and Co²⁺ based on aggregation-induced emission (AIE) fluorescence strategy. It has sensitive detection ability for Cu²⁺ and Co²⁺. In addition, the color changed from yellow-green to orange under the sunlight, realizing the rapid identification of Cu²⁺/Co²⁺, which has the potential of on-site visual detection under the "naked eye". Moreover, different "on" and "off" fluorescence expressions were exhibited under excessive glutathione (GSH) in AMN-Cu²⁺ and AMN-Co²⁺ systems, which could be employed to distinguish Cu²⁺ from Co²⁺. The detection limits for Cu²⁺ and Co²⁺ were measured to be 8.29 × 10^-8 M and 9.13 × 10^-8 M, respectively. The binding mode of AMN was calculated to be 2:1 by Jobs' plot method analysis. Ultimately, the new fluorescence sensor was applied to detect Cu²⁺ and Co²⁺ in real samples (tap water, river water, and yellow croaker), and the results were satisfying. Therefore, this high-efficiency bifunctional chemical sensor platform based on "on-off" fluorescence detection will provide significant guidance for the advance development of single-molecule sensors for multi-ion detection.

Quantification of tyramine in different types of food using novel green synthesis of ficus carica quantum dots as fluorescent probe

Tyramine (TYM) is catecholamine releasing compound, tyramine rich food causing hypertensive crisis due to combination with monoamine oxidase inhibitor (MAOIs). So, Analysis of TYM in tyramine rich food (old cheese, cured meat, sausage, pickled olive and canned fish) and environment is very essential for hypertensive patients and improvement food industries. In this work, TYM was analyzed in different types of food using novel green synthesis carbon dots from ficus carica (Fig fruits). The gradual addition of TYM to PA@CQDs led to enhancement of the quantum dots fluorescence due to formation of hydrogen bonding between quantum dots and TYM. The calibration graph plotted in the range 5-400 ng mL^-1 . The method was applied to determination of TYM in different types of food as old cheese, cured meat, sausage, pickled olive and canned fish. The lower limit of quantitation (LOQ) was found to be 1.68 ng mL^-1 . The method successfully applied for the quantification of TYM in varying types of food with high sensitivity and high economic effect due to the reusability of the quantum dots. The optical and morphological characters of quantum dots were studied carefully.