Chemosensor For Ag Research Articles

1,10-Phenanthroline-based hexacatenar LCs with complex self-assembly, photophysical and binding selectivity behaviors

A novel series of V-shaped phenanthroline-based hexacatenars containing a 1,10-phenanthroline which was substituted on 2,9- positions with two cyanovinyl units were synthesized using oxidation and Knoevenagel reactions. The self-assembly, photophysical properties and chemosensor behavior were investigated by POM, DSC, XRD, SEM, DFT calculation, UV–vis absorption and luminescence emission spectroscopies. The shorter homologues are non-mesogens, whereas the highest homologue could self-assemble into complex CubI/Pm3¯n mesophase in the bulk state. These compounds could form fluorescence organogels and the self-assembly morphologies could be tuned from disordered plate morphologies via winkled morphologies and nanofibers to nanosheets by changing the solvent polarity. The UV–vis absorption and fluorescence spectra demonstrated that these compounds showed obvious solvatochromism and strong fluorescence in both solution and aggregated states. The fluorescence intensity in the solution was much higher than that in the aggregated state due to the poor solubility and large conjugated planar of 1,10-phenathroline which was demonstrated by DFT calculation. These compounds could act as chemosensor for Ag+ among the different anions and cations with an extremely low detection limit of 50 nM, and the binding site and recognition mechanism were proved by FT-IR, 1H NMR and DFT calculation. Therefore, the design strategy of such luminescent LCs would offer a new perspective for constructing novel 3D self-assembly materials and expand their applications in chemosensor.

A novel chemosensor for Ag(I) ion based on its inhibitory effect on the luminol–H2O2 chemiluminescence response improved by CoFe2O4 nano-particles

In the present study, we report on a simple, sensitive and selective chemosensor for the recognition and monitoring of silver ions in aqueous solutions. It is based on the inhibitory effect of Ag(I) ion on the chemiluminescence signal of H2O2–luminol system, which could be improved by at least 10-folds in the presence of cobalt ferrite (CoFe2O4) magnetic nano-particles. The structure and morphology of the synthesized CoFe2O4 nano-particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The as-prepared CoFe2O4 nano-particles were then used as catalysts for H2O2–luminol chemiluminescence system. The enhanced chemiluminescence signal was dramatically decreased by adding trace levels of Ag(I) ion into the solution. The possible mechanism to explain this finding was discussed. Several parameters affecting the analytical signal such as the pH value, the concentrations of H2O2, luminal and CoFe2O4 nano-particles, incubation time and interfering ions were investigated and optimized. Under the optimized experimental conditions, chemiluminescence intensity of luminol–H2O2–CoFe2O4versus Ag(I) concentration gave a linear response within the range of 0.5–100ngmL−1 with a detection limit of 0.15ngmL−1. The method was successfully applied to monitoring Ag(I) in various water samples.

Nanoaggregates of benzothiazole-based amidine-coupled chemosensors: a chemosensor for Ag+ and the resultant complex as a secondary sensor for Cl−

Nanoaggregates of benzothiazole-based amidines were prepared for study as sensors in aqueous medium. Sensor N2 was found to behave as a selective primary sensor for Ag+, and the subsequent complex N2·Ag+ acted as a secondary sensor for Cl− in aqueous medium through a cation displacement mechanism. The cation displacement mechanism was further supported by a CV titration of complex N2·Ag+ with Cl−.

A Highly Selective Chemosensor Probe for Ag<sup>+</sup> in 50% THF/H<sub>2</sub>O

A highly selective chemosensor for Ag+ based on heterocyclic compound Diethyl 6-anilino-5H-2,3-dithia-5,7-diazacyclopenta (cd) indene-1,4-dicarboxylate (D1) was investigated. The deprotonation of N-H was observed easily in spectra of D1 (2.5×10-5 M) in 50% H2O/THF solution after NaOH addition, and the deprotonated D1 could interact with Ag+, resulted in the sharp decrease of deprotonated absorption. The addition of other metal ions would not produce an obvious change, which means quite extreme selectivity for Ag+ compared with other metal ions. The LOD of the method to detect Ag+ was 8.07×10-8 M. It is indicated that a novel high selective chemosensor for Ag+ was build up.