These interactions are extremely specific and the host (receptor) can be used to develop technological devices, such as membranes, catalysts and sensors. Small molecule chemosensors mainly rely on the direct interaction of the receptor with the analyte. Small molecule chemosensors have been frequently used due to their high sensitivity, selectivity and facile process.
Thiosemicarbazone Based Water-Soluble Polymeric Probe for the Selective Sensing
A water-soluble polymer probe based on thiosemicarbazone was developed for selective colorimetric detection of Cu(II) ions with pH-tunable sensitivity. Successful separation of Cu(II) ions from several alkali and transition metal cations by thermal precipitation has been demonstrated. After the addition of Cu(II) ions to the aqueous solution of P2, the color of the solution changed from colorless to yellow due to the formation of a coordination complex between Cu(II) ions and the phenylthiosemicarbazone units of P2, here P2− Cu(II).
A number of molecular probes have been reported for the detection of Cu(II) ions, but the development of chemosensors that can be used in aqueous media is still challenging.9, 25-27. In this regard, stimuli-responsive water-soluble polymers with molecular receptor moieties or sensing units for Cu(II) ions are attractive. Compared to other conventional detection systems based on small molecular probes, stimuli-responsive polymeric probes offer.
The reason the wavelength 390 nm was drawn is that wavelengths shorter than 390 nm are part of the UV spectrum and are not visible, and 390 nm is the onset of the greenish-yellow color.37-39 A decrease at 318 nm and an increase in absorbance at 390 nm was monitored upon stepwise addition of Cu(II) ions up to 35 μM, above which no further changes were observed. As a result, the color of the P2 solution changed from colorless to greenish yellow, which could be easily seen with the naked eye. After demonstrating the selective and sensitive detection of Cu(II) ions with P2, we tried pH-dependent control of Cu(II) ion detection.
For this, we examined the UV-Vis spectra of the P2 solution at different pH after the addition of 50 μM Cu(II) ions (Figure 3a). As expected, the Δλmax of the solution at pH 7 showed a 10 nm red shift with spectral broadening upon the addition of Cu(II) ions. Schematic diagram of colorimetric detection of Cu(II) ions with adjustable detection sensitivity driven by pH change in aqueous solution; a) high pH (tertiary amine with lone pairs of electrons): formation of P2-Cu(II) coordination complexes via thiourea sulfur and imino nitrogen atoms with rearrangement of the thiourea part into a favorable syn-conformation and b) low pH (quaternary amine salt): no formation of coordination complexes P2- Cu(II) due to protonation of imino nitrogen atoms.
The effects of the formation of P2-Cu(II) coordination complexes on the LCST point were also investigated by dynamic light scattering (DLS) at the same aqueous concentration (10 mg/mL) as used for turbidimetry studies. The LCST point was defined as the onset temperature of the increase in particle size. After showing the thermal phase transition behavior of the P2-Cu(II) coordination complexes, the efficient separation of Cu(II) ions between other metal cations was attempted.
This separation was made possible by the thermoresponsive nature of the P2-Cu(II) coordination complexes; upon heating the P2-Cu(II) coordination complexes above the LCST (47 oC), only P2-Cu(II) precipitated from an aqueous solution, leaving other metal cations intact, facilitating the separation of Cu(II) ions from other metal cations. ICP-OES was used to evaluate the efficiency of the separation of Cu(II) ions by thermal precipitation. Before adding P2, the amount of metal ions in the original solution varied from 30 to 50 ppm (black column).
Plots of apparent hydrodynamic diameters as a function of temperature measured by DLS for an aqueous solution (10 mg/mL) of the original P2 and P2 + Cu(II) ion complexes (after the addition of 50 μM Cu(II) ions) .
Efficient rhodamine-thiosemicarbazide-based colorimetric/fluorescent "turn-on" chemodosimeters for the detection of Hg 2+ in aqueous samples. A new highly selective, ratiometric and colorimetric fluorescence sensor for Cu2+ with a remarkable red shift in absorption and emission spectra based on internal charge transfer. Water-soluble and highly selective fluorescent sensor of naphthol-aldehyde-tris-derivative for the detection of aluminum ion.
Hydrophilic copolymer bearing dicyanomethylene-4 H-pyran moiety as fluorescent film sensor for Cu2+ and pyrophosphate anion. Competition of divalent metal ions with monovalent metal ions for the adsorption on water-soluble polymers. Removal of heavy metal ions and humic acid from aqueous solutions by co-adsorption on thermosensitive polymers.
An eye-free chemosensor for simultaneous detection of iron and copper ions and its copper complex for colorimetric/fluorescence sensing of cyanide. Novel highly selective off-on-off coumarin-based fluorescent sensor for Cu2+ and S2- in aqueous solution. Inhibition of ribonucleotide reductase by metal complexes of Triapin (3-aminopyridine-2-carboxaldehyde thiosemicarbazone): A combined experimental and theoretical study.
A water-soluble polymer for selective colorimetric detection of cysteine and homocysteine with temperature adjustable sensitivity.
Thiosemicarbazone Based Polymeric for the Sustained Release of a Model Drug via
The well-defined amphiphilic phenylthiosemicarbazone-based block copolymer was successfully synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, followed by post-polymerization modification. The resulting pDMA macrochain transfer agent (macroCTA) was further extended with 3-vinylbenzaldehyde (VBA) to yield poly[(N,N-dimethylacrylamide)-b-(3-vinylbenzaldehyde)]p(DMA-b-VBA) block copolymer. The core of p(DMA-b-PVHC) micelles was cross-linked via the slow penetration of Cu(II) ions into the core, and the resulting particles with cross-linked ionic nuclei were swollen in water.
Recently, the selective detection and efficient separation of transition metal ions have become increasingly important. Among them, the detection of Cu(II) ions has attracted more attention because they may have both advantages and disadvantages for human health and the environment. In the past, Cu(II) ions were detected by atomic absorption spectroscopy (AAS), inductively coupled plasma (ICP), voltammetry, and the piezoelectric effect, which are often expensive and time-consuming methods.16 An alternative method for selective detection is the use of colorimetric or fluorescence spectroscopy. .
While these methods have been widely used for the detection of Cu(II) ions, thiosemicarbazone ligand complexes with Cu(II) ions have attracted attention as they cause anticancer, antiviral, anti-inflammatory agents and less side effects.17-23. Cu(I) or Cu(II) ions not only play a vital role in normal cells, but also play a critical role in cancer. Interestingly, many studies reported high concentrations of Cu ions in blood serum and breast cancer.
Lymphoma, bronchogenic, reticulum cell sarcoma, and cervical, breast, stomach, and lung cancer showed high concentrations of Cu ions in serum.24 For example, higher concentrations of Cu ions in serum and tissue were. Cu ions have certainly been shown to promote cancer growth and metastasis.24-26 Considering the increase of Cu ions by malignant cells and the promotion of cancer progression, thiosemicarbazone appears as a potential target for the development of new anticancer therapeutics.27-30 we recently reported a selective colorimetric detection of Cu(II) ions by the phenylthiosemicarbazone units of polymer-based sensors in aqueous media.16 Compared with the small molecule thiosemicarbazone sensor, p(DMA-co-PVHC) was used to detect Cu(II) ions and the tunable sensitivity that driven by pH. Cu(II) ions can slowly penetrate into the micelle core and act as a time-dependent cross-linker.
On the other hand, through coordinated interactions, the complexes of thiosemicarbazone blocks with Cu(II) ions would make the polymers more hydrophilic, leading to increased hydrophilicity of the hydrophobic core of pVHC blocks of p(DMA-b-PVHC) micelles .
The original colorless solution turned yellow upon addition of Cu(II) ions due to the formation of coordination complexes between Cu(II) ions and phenylthiosemicarbazone units of p(DMA-b-PVHC) micelles.16, 31 As previously reported, p.(DMA-b-PVHC) exhibited good selectivity towards Cu(II) ions over several alkali and transition metal cations (Figure 2b). The time required for complete detection of Cu(II) ions with p(DMA-b-PVHC) micelles was found to be about 24 h. For this, 100 μM Cu(II) ions were added to 0.01 mg/ml p(DMA-b-PVHC) micellar solution in water and the evolution of size distributions was measured as time progressed (Figure 4a).
After the addition of 100 μM Cu(II) ions, the average hydrodynamic diameter gradually increased with time and reached 75 nm after 24 h. The time-dependent slow penetration of Cu(II) ions into the core of micelles led to the intermolecular tetradentate coordination complexation with phenylthiosemicarbazone ligands, which caused the formation of the polymer micelles with cross-linked ionic cores (Figure 4b). 10 μM Cu(II) ions were then added to the p(DMA- b -PVHC) micelle solution (0.01 mg/ml) and spun onto a mica substrate 24 h later for AFM analysis.
After the addition of 100 μM Cu(II) ions, the emission intensity of coumarin 102 decreased steadily with time. The release kinetics were further investigated with different concentrations of Cu(II) ions (33 and 66 μM) in parallel with a control experiment in which no Cu(II) ions were added (Figure 6b). However, after the addition of 100 μM Cu(II) ions, the initially colorless solution turned yellow with no fluorescence intensity, indicating that almost quantitative release was achieved.
While it took one day to complete the detection of Cu(II) ions, followed by full swelling of core-crosslinked p(DMA-b-PVHC) micelles, the sustained release of the encapsulated dye up to 1 month continued. The observation of Cu(II) ions in aqueous media described here relies on the slow penetration of Cu(II) ions into the hydrophobic core of PVHC blocks of p(DMA-b-PVHC) micelles. DLS and AFM investigations revealed that the size of micelles increased after the addition of Cu(II) ions due to the swelling of crosslinked ionic cores generated by the detection of Cu(II) ions .