Colorimetric and fluorescence sensing of Cu2+ in water using 1,8-dihydroxyanthraquinone-β-cyclodextrin complex with the assistance of ammonia

A multi-responsive pyranone based Schiff base for the selective, sensitive and competent recognition of copper metal ions

Exploring a new multi-responsive pyranone chemosensor capable of sensing copper ions specifically and selectively through colorimetric, UV-Vis absorption and fluorescence methods is of great importance. In this piece of work, a novel pyranone based Schiff base ligand 4-Hydroxy-6-methyl-3-[1-(2-morpholin-4-yl-ethylimino)-ethyl]-pyran-2-one (DM) was synthesized by the condensation of dehydroacetic acid and 4-(2-aminoethyl) morpholine. The structural determination of ligand DM was executed using distinct spectral techniques i.e.,¹H NMR, ¹³C NMR, FT-IR and HR-MS techniques. The reported Schiff base DM showed an immediate colorimetric change from pale yellow to colorless accompanied by a strong change in the UV-Vis absorption band onto the addition of Cu (II) ions. This metal ligand chelation leads a decrease in ICT process. Also the decrease in fluorescence emission intensity of Schiff base DM with Cu (II) ions addition showed its turn-off behavior towards copper ions. Further absorption/ emission titration studies, Job's plot, HR-MS and ¹H NMR titration data designated 2:1 stoichiometric ratio between DM and Cu (II) ions respectively. Density functional theory studies were also performed to authenticate the binding mechanism theoretically. The sensitivity of Schiff base DM towards Cu (II) ions was applicable at every pH conditions and at the same time DM exhibited selectivity towards Cu (II) ions with a negligible interference of other metal ions. DM showed a detection limit of 7.7 nM towards copper ions via fluorescence emission studies. The best part about DM is that it has good stability but showed an instant chemical reversibility when titrated with EDTA solution.

Simple admixture of 4-nitrobenzaldehyde and 2,4-dimethylpyrrole for efficient colorimetric sensing of copper(II) ions

An easily accessible chemo-probe based on physical mixture of 2,4-dimethylpyrrole and 4-nitrobenzaldehyde has been developed. Based on NMR spectroscopic analysis, catalyst free formation of dipyrromethane was observed in the physical mixture of chemo-probe. The probe is utilized in effective colorimetric sensing of copper(II) ions present in environmental solutions by instantaneous appearance of red colour, even in the co-existence of various metal ions. The lowest detection limit of 2.51 μM for this chemo-probe towards copper(II) sensing is significantly lower than the WHO prescribed level (<30 μM of copper(II) ions) in potable water. The sensing mechanism is explained via rapid formation of bis(dipyrrinato)copper(II) complex, as confirmed by Jobs plot, UV-Vis spectroscopy and IR spectroscopy.

A "Turn-On" Fluorescence Copper Biosensor Based on DNA Cleavage-Dependent Graphene Oxide-dsDNA-CdTe Quantum Dots Complex

A novel “turn-on” fluorescent copper biosensor is developed successfully based on the graphene oxide (GO)-dsDNA-CdTe quantum dots (QDs) complex via chemical crosslink method. The optical and structure properties of GO-dsDNA-CdTe QDs complex are studied by fluorescence (FL) spectra and transmission electron microscopy (TEM) in detail. It is demonstrated that the fluorescence quenching of CdTe QDs is a process of fluorescence resonance energy transfer (FRET) due to the essential surface and quenching properties of two-dimensional GO. Copper ions induce the catalytic reaction of DNA chain and irreversibly break at the cleavage site, which will cause the G-quadruplex formation, moreover further result in the CdTe QDs separated from GO and restored its fluorescence. Therefore, a significant recovery effect on the fluorescence of the GO-dsDNA-CdTe QDs complex is observed in the presence of copper ions. The fluorescence responses are concentration-dependent and can be well described by a linear equation. Compared with other metal ions, the sensor performs good selectivity for copper ions.

C–H oxidation and chelation of a dipyrromethane mediated rapid colorimetric naked-eye Cu(ii) chemosensor

Selective C–H oxidation and chelation of DPMs mediated by copper is demonstrated and utilized in the development of a rapid colorimetric naked-eye Cu(ii) chemosensor.

An anthraquinone-based highly selective colorimetric and fluorometric sensor for sequential detection of Cu2+ and S2− with intracellular application

An anthraquinone-based highly selective colorimetric and fluorometric probe for sequential detection of Cu²⁺ and S²⁻ with intracellular application is reported.

A new fluorescent PET sensor probe for Co2+ ion detection: computational, logic device and living cell imaging applications

A new probe, 2 exhibit quenching with Co²⁺ (∼80% at 634 nm) while 2·Co²⁺ ensemble exhibit enhancement with NO₃⁻ (∼82% at 632.5 nm). On–Off–On behavior of 2 (Co²⁺ and NO₃⁻ ions) the function of a sequential XNOR gate and can be utilized in live cell imaging.

Photophysical properties of some poly(siloxane–azomethine)s

The responsive optical properties of some poly(siloxane–azomethine)s incorporating 1,8-dihydroxyanthraquinone units (PSA1 and PSA2) toward various metal ions (nickel (Ni2+), copper (Cu2+), silver, zinc, ferric, manganese, calcium (Ca2+), chromium, cadmium, barium, magnesium, lead, mercury, strontium, and cobalt) were investigated by steady-state and time-resolved fluorescence techniques. The fluorescence quenching has shown a significant deviation from the Stern–Volmer linearity due to the effect of combination of dynamic and static quenching for PSA1 in the presence of metal ions. Generally, the fluorescence decay is described by a two-exponential relation. The fluorescence of these PSAs was efficiently quenched by Cu2+ and Ni2+ ions, and these derivatives could be investigated as a promising system for the development of new sensors for the detection of Cu2+.

A fluorescent “turn on” chemosensor based on Bodipy–anthraquinone for Al(iii) ions: synthesis and complexation/spectroscopic studies

A fluorescent “turn on” Al(iii) chemosensor based-on bodipy–anthraquinone with two triazole ring was prepared and studied for its complexation and spectroscopic properties.

Fluorometric sensing of Pb2+and CrO42−ions through host–guest inclusion for human lung cancer live cell imaging

The formation of an inclusion complex between 1,5-dihydroxyanthraquinone (1,5-DHAQ;1) and β-cyclodextrin (β-CD) in aqueous media has been studied by UV-visible and fluorescence spectroscopy.

Synthesis, characterization of conjugated oligo-phenylene-ethynylenes and their supramolecular interaction with β-cyclodextrin for salicylaldehyde detection

Four new conjugated oligo-phenylene-ethynylenes derivatives, N-methyl-4-(4-acetylthiophenylethynyl)-1,8-naphthalimide (1), thioacetic acid S-[4-(4-aminophenyl-ethynyl)phenyl]ester (2), 4-methylthiophenylethynylbenzenamine (3), N-methyl-4-(4-methyl-thiophenyl-ethynyl)-1,8-naphthalimide (4), were synthesized by Sonogashira and Eglinton cross-coupling reactions. The structures of the four compounds were confirmed by (1)HNMR, (13)CNMR, MS and IR and their spectral characteristics were studied by ultraviolet and visible (UV) spectroscopy as well as fluorescence spectroscopy in different medium. It was found that the fluorescence properties of compounds 2 and 3 were notably improved in aqueous solutions in the presence of β-cyclodextrin (β-CD). Spectral analysis supported the suppositions that the fluorescence intensity enhancement was due to the formation of inclusion complex with β-CD. The supramolecular interaction was investigated in detail and the reaction mechanism was provided. A salicylaldehyde determination method in aqueous medium was established based on the supramolecular complex of compound 3. Under the optimum conditions, the supramolecular complex exhibited a dynamic fluorescence response range for salicylaldehyde from 0.6 to 240×10(-6) molL(-1), with a detection limit of 1×10(-8) molL(-1).