Tridentate Lysine-Based Fluorescent Sensor for Hg(II) in Aqueous Solution

Organic Molecules Containing N, S and O Heteroatoms as Sensors for the Detection of Hg(II) Ion; Coordination and Efficiency toward Detection

Rapid detection of potentially toxic heavy metals like Hg(II) has attracted great attention in the last few decades due to the importance to maintain a safe and sustainable environment for human beings. Coordination chemistry and concepts therein, play an important role in the detection of Hg(II). Size, charge, and nature of the donor atom and the respective cation (metal ion), are crucial in selective interactions between the sensor and metal ions. The sensors designed for the purpose, coordinate to Hg(II) ion through various donor sites, coordination causes a change in the electron density in organic molecules and results in either visible color change or enhancing/quenching fluorescence intensity. Since Hg(II) is soft metal, with d10 electron system, so majority of the sensors have soft donor sites which prefer to coordinate with Hg(II). Oxygen is also present in some chelating ligands which is least preferred coordination site, due to its hard nature. There are several reports of replacing other ligating sites by sulfur for enhanced mercury sensing. In some cases, desulfurization is being detected as clear change in spectral behavior during the sensing process. Efforts are still in progress to design and introduce a sensor with utmost sensitivity and selectivity. In this review, we made an attempt to explain the coordination aspects of Hg(II) detectors, reasons for poor efficiency and possible suggestions to improve the selection criterion of various compounds. It will help researchers to know about important concepts in designing more sensitive and selective sensors for detection of Hg(II) in environmental and biological samples.

Architecture of multi-channel and easy-to-make sensors for selective and sensitive Hg2+ ion recognition through Hg‒C and Hg‒N bonds of naphthoquinone-aniline/pyrene union

The aim of this work is, for the first time, to develop new inexpensive, easy-to-make and multi-channel receptors, naphthoquinone-aniline/pyrene union ((Nq-An) and (Nq-Pyr)) and their Hg²⁺ complexes [Hg-(Nq-An)₂] and [Hg-(Nq-Pyr)₂] to supply an efficient solution to critical deficiencies to be encountered for Hg²⁺ recognition. This study is based on colorimetric, fluorometric, and voltammetric methods for determination of Hg²⁺ ions through Hg-C and Hg-N binding mode of the naphthoquinone-aniline/pyrene union in aqueous media. The binding mode of the receptors with Hg²⁺ cation was confirmed by usual characterization techniques for the synthesized Hg²⁺-complexes [Hg-(Nq-An)₂] / [Hg-(Nq-Pyr)₂] and voltammetric, ¹H NMR titration experiments as well as Job's method, indicating a 2:1 complex between the receptors and Hg²⁺ cation. The receptors showed a considerable color switching from orange to pink along with a red-shift of absorption wavelength, and fluorescence enhancement via the Chelation Enhanced Fluorescence effect (CHEF), and distinctive changes on the voltammogram of the electroactive naphthoquinone unit with Hg²⁺ cation. The experiments indicate that the sensors are highly selective and sensitive toward Hg²⁺ among the studied metal ions in aqueous media compared with other reported Hg²⁺ sensors.

Sulfur Conversion to Multifunctional Poly(O-thiocarbamate)s through Multicomponent Polymerizations of Sulfur, Diols, and Diisocyanides

Sulfur, which is generated from the waste byproducts in the oil and gas refinery industry, is an abundant, cheap, stable, and readily available source in the world. However, the utilization of excessive amounts of sulfur is mostly limited, and developing novel methods for sulfur conversion is still a global concern. Here, we report a facile one-step conversion from elemental sulfur to functional poly(O-thiocarbamate)s through a multicomponent polymerization of sulfur, diols, and diisocyanides, which possesses a series of advantages such as mild condition (55 °C), short reaction time (1 h), 100% atom economy, and transition-metal free in the catalyst system. Seven poly(O-thiocarbamate)s are constructed with high yields (up to 95%), large molecular weight (up to 53100 of M_w), good solubility in organic solvents, and completely new polymer structures. The poly(O-thiocarbamate)s possess a high refractive index above 1.7 from 600 to 1700 nm by adjusting the sulfur content. By incorporating tetraphenylethene (TPE) moieties into the polymer structure, the poly(O-thiocarbamate)s can also be designed as fluorescent sensors to detect harmful metal cation of Hg²⁺ in a turn-on mode with high sensitivity (LOD = 32 nM) and excellent selectivity (over interference cations of Pb²⁺, Au³⁺, Ag⁺). Different from the previous reports, the exact coordination structure is first identified by single-crystal X-ray diffraction, which is revealed in a tetracoordination fashion (two sulfur and two chloride) using a model coordination compound.

A sensitive pH fluorescent probe based on triethylenetetramine bearing double dansyl groups in aqueous solutions and its application in cells

pH fluorescent probes possess many advantages, including intracellular detection, rapid response time and nondestructive testing. In this paper, a highly selective and sensitive fluorescent pH probe based on triethylenetetramine bearing double dansyl groups (1) was synthesized. This probe offers fluorescent measurement of pH value in the range of 5.81-7.21 in aqueous solution, with an 8.64-fold enhancement of fluorescent emission intensity over the unmodified probe. Probe 1 shows a fluorescent color change from a pale yellow to bright green when the pH is increased from 5.81 to 7.21. In addition, probe 1 shows good potential as a fluorescent visualizing sensor for pH values in living GS cells of epinepheluscoioides. The mechanism of the fluorescent response of probe 1 to solution pHs was further clarified by NMR, fluorescent spectra, and UV-vis absorption spectra. The results indicate that the fluorescent emission will shift with an increase in solution pHs, due to increasing deprotonation of the nitrogen atom on the sulfonamides. Deprotonation of the sulfonamide group will inhibits the intramolecular charge transfer process between the imino group and the naphthalene ring, resulting in the recognition phenomenon of blue shift and enhancement of fluorescent emission intensity.

Multifunctional tryptophan-based fluorescent polymeric probes for sensing, bioimaging and removal of Cu2+ and Hg2+ ions

Fluorescent polymeric probes were synthesized by amalgamating tryptophan and pyridine side-chain moieties through an imine bond with the aim of selectively sense and remove both Cu²⁺ and Hg²⁺ ions from aqueous media.

A novel bimacrocyclic polyamine-based fluorescent probe for sensitive detection of Hg2+ and glutathione in human serum

Detection of glutathione in human serum is of great importance for clinical diagnosis of various diseases, such as AIDS, diabetes mellitus, Alzheimer disease and cancer. In this work, a new water-soluble bismacrocyclic polyamine-derived compound, namely L, which contains two molecules of 4-nitro-1,2,3-benzoxa-diazole as the fluorophores, was designed and prepared. The experiments of selectivity of L toward metal ions showed it could rapidly and sensitively detect Hg²⁺ with a detection limit of 27 nM. Furthermore, the cell imaging and co-staining experiments in HeLa cells demonstrated that the L-Hg²⁺ probe had selectivity for the Golgi apparatus to a certain degree. Moreover, it had excellent selectivity for biothiols, especially for glutathione. Finally, the probe was successfully applied to sensitively detect glutathione (GSH) in human serum and fetal bovine serum.

Sensitive Water-Soluble Fluorescent Probe Based on Umpolung and Aggregation-Induced Emission Strategies for Selective Detection of Hg2+ in Living Cells and Zebrafish

Using Hg²⁺-induced umpolung reaction and aggregation induced emission (AIE), we have rationally developed a water-soluble fluorescent probe 2,2'-(((4-(4,5-bis(4-methoxyphenyl)-1-phenyl-1H-imidazol-2-yl)phenyl)methylene)bis(sulfanediyl))diethanol (MPIPBS) for Hg²⁺ detection. MPIPBS was found to have high selectivity and sensitivity toward Hg²⁺ detection. The mechanism of MPIPBS response to Hg²⁺ was verified by ¹H NMR titration, HPLC, and HRMS spectroscopy. The detection limit was examined to be 1.45 nM, which is lower than most reported probes for Hg²⁺. Taking advantage of excellent optical properties of AIEgen, a paper based sensor for Hg²⁺ detection was fabricated by immobilizing the MPIPBS on Waterman test paper. Meanwhile, MPIPBS showed satisfactory analytical performance in real water and urine samples. Further, thanks to the high water solubility, cell membrane permeability and low cytotoxicity, MPIPBS was further used to detect Hg²⁺ both in living cells and zebrafish. We anticipate that the prepared probe was available to detect Hg²⁺ in environment and biosamples.

Determination of lysine content based on an in situ pretreatment and headspace gas chromatographic measurement technique

This work reports on a simple method for the determination of lysine content by an in situ sample pretreatment and headspace gas chromatographic measurement (HS-GC) technique, based on carbon dioxide (CO₂) formation from the pretreatment reaction (between lysine and ninhydrin solution) in a closed vial. It was observed that complete lysine conversion to CO₂ could be achieved within 60 min at 60 °C in a phosphate buffer medium (pH = 4.0), with a minimum molar ratio of ninhydrin/lysine of 16. The results showed that the method had a good precision (RSD < 5.23%) and accuracy (within 6.80%), compared to the results measured by a reference method (ninhydrin spectroscopic method). Due to the feature of in situ sample pretreatment and headspace measurement, the present method becomes very simple and particularly suitable to be used for batch sample analysis in lysine-related research and applications. Graphical abstract The flow path of the reaction and HS-GC measurement for the lysine analysis.

Isatin functionalized nanoporous SBA-15 as a selective fluorescent probe for the detection of Hg(II) in water

A highly ordered mesoporous silica material functionalized with isatin (SBA-Pr-IS) was designed and synthesized. Characterization techniques including XRD, TGA, BET, SEM, and FT-IR were employed to characterize the pore structure, textural properties, microscopic morphology, and molecular composition of grafted organic moieties of SBA-Pr-IS. The successful attachment of the organic moiety (0.34 mmol g^-1) without the SBA-15 structure collapsing after the modification steps was confirmed. Fluorescence characterization of SBA-Pr-IS was examined upon addition of a wide variety of cations in aqueous medium and it showed high sensitivity toward Hg²⁺ ions. During testing in an ion competition experiment, it was observed that the fluorescence changes of the probe were remarkably specific for Hg²⁺ ions. Furthermore, a good linearity between the fluorescence intensity of this material and the concentration of Hg²⁺ ions was constructed with a suitable detection limit of 3.7 × 10^-6 M. Finally, the applicability of the proposed method was successfully evaluated for the determination of Hg²⁺ ions in real samples. Therefore, SBA-Pr-IS can be used as an efficient fluorescence probe for Hg²⁺ ions. Graphical Abstract A novel organic-inorganic hybrid material was designed and synthesized by functionalization of SBA-15 mesoporous silica material with isatin. The evaluation of the sensing ability of SBA-Pr-IS using fluorescence spectroscopy revealed that the SBA-Pr-IS was a selective fluorescent probe for Hg²⁺ ion in water in the presence of a wide range of metal cations.

Design and construction of a new optical solid-state mercury(ii) sensor based on PVC membrane sensitized with colloidal carbon dots

A new Hg²⁺ ion solid-state double layer sensor impregnated with colloidal carbon dots and N′-(3-(4-(dimethylamino)phenyl)allylidene)isonicotinohydrazide (NDPAI, as a second layer) was inserted in plasticized polyvinyl chloride (PVC) as the first layer.

A facile synthesis of a highly water-soluble and selective fluorescent sensor towards zinc ions derived from β-cyclodextrin based on an unexpected sensing process

A highly selective and sensitive fluorescent sensor for Zn²⁺ derived from a β-cyclodextrin derivate was fabricated. Through fluorescence micrograph experiments, the sensor showed an excellent image effect on onion epidermal cells.

Optical sensor: a promising strategy for environmental and biomedical monitoring of ionic species

In this review, we cover the recent developments in fluorogenic and chromogenic sensors for Cu²⁺, Fe²⁺/Fe³⁺, Zn²⁺and Hg²⁺.

A facile naphthalene-based fluorescent chemodosimeter for mercury ions in aqueous solution

A facile naphthalene-based fluorescence “turn-on” chemodosimeter for rapid, selective and sensitive detection of Hg²⁺ by mercury-promoted hydrolysis of the vinylether group has been reported.

Fluorescent and colorimetric sensors for environmental mercury detection

The development of fluorescent and colorimetric sensing strategies for environmental mercury is described.

A highly sensitive hemicyanine-based fluorescent chemodosimeter for mercury ions in aqueous solution and living cells

A novel hemicyanine-based fluorescence turn-on chemodosimeter for Hg²⁺ by mercury triggered hydrolysis of vinyl ether group has been reported.

New cellulose-lysine Schiff-base-based sensor-adsorbent for mercury ions

Mercury is a highly toxic environmental pollutant; thus, there is an urgent need to develop new materials for its simultaneous detection and removal from water. In the present study, new oxidized cellulose-based materials, including their Schiff bases, were synthesized and investigated as a sensor-adsorbent for simple, rapid, highly selective, and simultaneous detection and removal of mercury [Hg(II)] ions. Cellulose was extracted from the pine needles, etherified, oxidized, and modified to Schiff base by reaction with l-lysine. The well-characterized cellulose Schiff base materials were used as a sensor-adsorbent for Hg(II) from aqueous solution. Hg(II) sensing was analysed with naked-eye detection and fluorescence spectroscopy. Schiff base having a decyl chain, C10-O-cell-HC═N-Lys, was observed to be an efficient adsorbent with a very high maximum adsorption capacity of 258.75 mg g(-1). The data were analyzed on the basis of various kinetic and isotherm models, and pseudo-second-order kinetics and Langmuir isotherm were followed for Hg(II) adsorption.

Ratiometric fluorescence chemosensor based on tyrosine derivatives for monitoring mercury ions in aqueous solutions

Ratiometric fluorescent chemosensors1and2were synthesized based on tyrosine amino acid derivatives with a pyrene fluorophore.

Glutamine-containing "turn-on" fluorescence sensor for the highly sensitive and selective detection of chromium (III) ion in water

In this study, we reported a new fluorescence sensor for chromium (III) ion, dansyl-L-glutamine (1). The sensor displayed a unique selective fluorescence "turn-on" response to Cr(3+) over other common metal ions in water. Notably, 1 still showed a ratiometric response to Cr(3+) in UV-vis absorption spectra. The binding mechanism of 1 to Cr(3+) was further clarified by using NMR and ESI-MS spectra. The experiment results indicated that the dual-responses of 1 to Cr(3+) should attribute to the coordination of deprotonated sulfonamide group with Cr(3+) and the protonation of the dimethylamino group due to the coordination of Cr(3+) for 1. In addition, two chloride ions also coordinated to the complex of sensor-chromium (III) ion, which further strengthened the conformation of 1-Cr(3+).