Development of a new series of thioacetal based fluorescence chemosensors for highly sensitive determination of Hg2+ in environmental samples and cell imaging

Mercury ion is one of the most harmful metal ions with significant hazards to the environment and human health. Thus, the development of innovative, sensitive, and selective sensors to help address the detrimental impacts of heavy metal contamination is necessary. In this work, we present three new chemosensors based on the deprotection reaction of the thioacetal group for distinguishing Hg2+ in environmental samples. These chemosensors show good photophysical properties with high quantum yield in aqueous medium. These prepared chemosensors were employed as fluorometric sensors for the determination of Hg2+ through the quenching of fluorescence emission due to the Hg2+-induced hydrolysis of the thioacetal to the aldehyde group. In the presence of Hg2+, chemosensors showed an emissive color transformation from blue fluorescence to non-fluorescence under UV light, which was readily seen by the visual eye. These chemosensors also exhibited highly distinctive selectivity toward Hg2+ over other interfering metal ions, with detection limits of 1.1 ppb, 13.4 ppb, and 12.7 ppb. Moreover, the practical applicability of chemosensor was successfully demonstrated in real water samples and herb extract samples.

Organic fluorescent compounds based on phenanthroimidazole: A review of highlight studies

Organic compounds containing phenanthroimidazole, and its optical, thermal, chemical, and high fluorescence, have drawn the interest of numerous researchers. Phenanthroimidazole derivatives are appealing for various applications due to these characteristics. This research provides a summary of the general information contained in studies on the synthesis, characterization, photophysical characteristics, and possible applications of phenanthroimidazole derivative compounds. The focus of this study revolves around the topic of utilization in technological fields such as sensors, solar cells, optical brighteners, and organic light-emitting diodes, and covers significant studies on mentioned topics. We anticipate that this study will provide an outline for researchers aiming to further examine fluorescent organic compounds for technological innovations. Furthermore, we anticipate that this research will be crucial in developing long-term high-organic compounds for optoelectronic devices.

Aryl-Phenanthro[9,10-d]imidazole: A Versatile Scaffold for the Design of Optical-Based Sensors

Fluorescent and colorimetric sensors are important tools for investigating the chemical compositions of different matrices, including foods, environmental samples, and water. The high sensitivity, low interference, and low detection limits of these sensors have inspired scientists to investigate this class of sensing molecules for ion and molecule detection. Several examples of fluorescent and colorimetric sensors have been described in the literature; this Review focuses particularly on phenanthro[9,10-d]imidazoles. Different strategies have been developed for obtaining phenanthro[9,10-d]imidazoles, which enable modification of their optical properties upon interaction with specific analytes. These sensing responses usually involve changes in the fluorescence intensity and/or color arising from processes like photoinduced electron transfer, intramolecular charge transfer, intramolecular proton transfer in the excited state, and Förster resonance energy transfer. In this Review, we categorized these sensors into two different groups: those bearing formyl groups and their derivatives and those based on other molecular groups. The different optical responses of phenanthro[9,10-d]imidazole-based sensors upon interaction with specific analytes are discussed.

Study on Photophysical Properties of Novel Fluorescent Phenanthroimidazole-Thiadiazole Hybrid Derivatives

Phenanthroimidazole-thiadiazole hybrid derivatives, which are new heterocyclic compounds with fluorescence properties, were synthesized by designing a two-step reaction mechanism and their photophysical properties were investigated. The synthesized derivatives were purified and their structures were elucidated by ATR-IR, ¹H-NMR, elemental analysis and HR-MS methods. In the next stage of the study, the absorption and emission spectra of the synthesized new phenanthroimidazole-thiadiazole hybrid derivatives were determined by UV-Vis and fluorescence spectroscopy. Stokes' shifts, molar extinction coefficients (ε), singlet energy levels (Es), quantum yield (ϕ_f), lifetimes (τ), the radiative (k_r) and the nonradiative (k_nr) constant for new hybrid derivatives were measured in DMSO. In addition, aggregation measurements, which is an important parameter that changes the photophysical properties were performed and for these compounds, structure: photophysical properties were discussed.

A Benzothiazole-Based Fluorescence Turn-on Sensor for Copper(II)

A new benzothiazole-based chemosensor BTN (1-((Z)-(((E)-3-methylbenzo[d]thiazol-2(3H)-ylidene)hydrazono)methyl)naphthalen-2-ol) was synthesized for the detection of Cu²⁺. BTN could detect Cu²⁺ with "off-on" fluorescent response from colorless to yellow irrespective of presence of other cations. Limit of detection for Cu²⁺ was determined to be 3.3 μM. Binding ratio of BTN and Cu²⁺ turned out to be a 1:1 with the analysis of Job plot and ESI-MS. Sensing feature of Cu²⁺ by BTN was explained with theoretical calculations, which might be owing to internal charge transfer and chelation-enhanced fluorescence processes.

Using a Modified Polyamidoamine Fluorescent Dendrimer for Capturing Environment Polluting Metal Ions Zn2+, Cd2+, and Hg2+: Synthesis and Characterizations

One of the most pressing global concerns is how to provide a clean environment for future generations given the exacerbation of urban, agricultural, industrial, and economic activities due to the escalating size of the global population. A polyamidoamine (PAMAM) dendrimer peripherally modified with 4-N,N′-dimethylethylenediamine-1,8-naphthalmide as a chromophore was synthesized and utilized to capture hazardous heavy metal ions. This modified fluorescent dendrimer (FCD) was complexed with Group 12 metal ions (Zn2+, Cd2+, and Hg2+) at a 2:1 (metal: FCD) ratio. Electronic absorption, fluorescence emission, Infra-red (IR), and nuclear magnetic resonance (1H NMR) spectroscopies, conductivity, CHN elemental, thermogravimetry, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were used to characterize the resulting metal complexes. These assays revealed that the synthesized complexes were yellow-colored, thermally stable, nanoscale-sized, and composed of [M2FCD]·4Cl2. Considerable spectral shifts were observed in the emission and absorption spectra of the FCD molecule after binding the Zn2+ ions, which can be used to differentiate the Zn2+ complex from the other two complexes. This work provides basic data to facilitate the detection, quantification, and removal of environmentally hazardous heavy metal ions through complexation with a fluorescent dendrimer.

A Rare Natural Benzo[k,l]xanthene as a Turn-Off Fluorescent Sensor for Cu2+ Ion

Rapid and efficient analyses of copper ions are crucial to providing key information for Cu²⁺ in living cells because of their biological importance. In this study, we reported one new turn-off fluorescent sensor for Cu²⁺ with a benzo[k,l]xanthene core, which served as an efficient cation sensor for copper ion over a wide range of other cations (Na⁺, K⁺, Ag⁺, Hg²⁺, Cd²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mg²⁺, and Fe³⁺) owing to the catechol group in the aromatic core. The sensor showed selectivity for Cu²⁺ over other ions; the logK_β for Cu²⁺ binding to compound 1 had a value of 13.265. In the presence of Cu²⁺, sensor 1 provided significant fluorescence decrement; Co²⁺, and Ni²⁺ caused a fluorescence decrement when employed at a higher concentration than Cu²⁺, while Na⁺, K⁺, Hg²⁺, Cd²⁺, Zn²⁺, and Mg²⁺ metal ions produced only minor changes in fluorescence intensity. Fluorescence experiments demonstrate that compound 1 may have an application as a fluorescent probe for detecting Cu²⁺ with a limit of detection of 0.574 µM.

An Acridine-Based Fluorescent Sensor for Monitoring ClO- in Water Samples and Zebrafish

A novel acridine-based fluorescent chemosensor, BK ((E)-2-((acridine-9-ylimino)methyl)-N-benzhydrylhydrazine-1-carbothioamide), for monitoring ClO- was prepared. The sensor BK was synthesized by introducing a new synthetic route of making aldehyde group using formic hydrazide. Probe BK displayed notable fluorescence quenching in the presence of ClO- and showed a great selectivity over other guest analytes. The detection limit was calculated to be 7.65 μM. Additionally, BK was satisfactorily applied for sensing ClO- in water samples and zebrafish.

Fluorescence "Turn On-Off" Sensing of Copper (II) Ions Utilizing Coumarin-Based Chemosensor: Experimental Study, Theoretical Calculation, Mineral and Drinking Water Analysis

Herein, we report the preparation of a fluorescent sensor based on coumarin derivative for copper (II) ion sensing in CH₃CN/HEPES media. 6,7-dihydroxy-3-(4-(trifluoro)methylphenyl)coumarin (HMAC) sensor was fabricated and analyzed by spectroscopic techniques. The sensor demonstrates "turn on-off" fluorescence quenching in the presence of copper (II) ions at 458 nm. A clear complex between the chemosensor HMAC and copper (II) ions was characterized by ESI-MS as well as the Job's method. Also, the limit of detection (LOD, 3σ/k) value was determined as 24.5 nM in CH₃CN/HEPES (95/5, v/v) buffer media (pH = 7.0). This value is lower than the admissible level of copper (II) ions in drinking water (maximum 31.5 μM) reported by EU Water Framework Directive (WFD) and World Health Organization (WHO) guidelines. The theoretical calculations (density functional theory, DFT) have been performed for the geometric optimized structures. As a final stage, real sample analyses have successfully been performed by using HMAC, as well as ICP-OES method. The relative standard deviation for copper (II) in mineral and drinking water samples has been determined to be below 0.15% and recovery values are in the range of 95.48-109.20%.

A novel fluorescent probe based on isocoumarin for Hg2+ and Fe3+ ions and its application in live-cell imaging

Synthesis of the 2-amino-4-phenyl-6- (isocoumarin-3-yl) -3-cyanopyridine (APICP) containing both isocoumarin and pyridine ring in its structure was carried out, and this compound was characterized by ATR-FTIR, ¹H NMR, and ¹³C NMR spectral techniques. A fluorescence sensor determining Hg²⁺ and Fe³⁺ ions in DMSO/HEPES buffer solution (9/1 v/v, 5 μM, pH 7.0) was developed using the synthesized compound, and the detection limits of the sensor with exquisite selectivity were calculated as 8.12 nM and 5.51 nM for Hg²⁺ and Fe³⁺ ions, respectively. Jobs plot method was used to determine the stoichiometry of APICP-Hg²⁺/Fe³⁺ complexes as 2:1 and FT-IR and ESI-MS methods confirmed the results. Besides, cell growth inhibitory potentials of the sensor over HepG2 cells and in vivo fluorescent cell imaging experiments were conducted. Findings revealed the relatively low cytotoxic effects of the synthesized sensor (IC₅₀: 0.541 ± 0.039 mM), and it could be utilized as an intracellular imaging agent for the determination of Fe³⁺ and Hg²⁺ ions in biological systems.

A Novel Ratiometric Fluorescent Probe for Mercury (II) ions and Application in Bio-imaging

Since the accumulation of mercury (II) ions in the environment and ecosystem causes serious problems to environment and disease, the recognition of Hg2+ ions and its bio-imaging is of high importance. In sight of the advantages of fluorescence probes, a new probe (PMH) was facilely synthesized by incorporating phenylimidazole fluorophore and 3-methyl-2- benzothiazolinone hydrazone hydrochloride monohydrate. The PMH probe exhibited a ratiometric response for Hg2+ ions with fluorescence intensity increasing at 520 nm and decreasing at 445 nm simultaneously. The PMH probe interacted with Hg2+ ions in seconds with high optical stability and showed good selectivity over other metal ions. In addition, the probe has excellent biocompatibility and imaging performance in cells and zebrafish.