A Turn off-on Fluorescent Chemosensor for Sequential Determination of Mercury and Biothiols

Selective Chromo-Fluorogenic Chemoprobe for nM Al3+ Recognition: Experimental and Living-Cell Applications

A rhodamine based chemoprobe BESN was engineered and employed as a selective ''OFF-ON'' chromo-fluorogenic sensor for Al3+ in H2O:MeOH (1:9, v:v). Notable changes in the absorption and emission spectra of BESN were clearly detectable upon the addition of Al3+. Sensitivity and binding mechanism studies demonstrated a good sensing performance of BESN with nanomolar detection limit (130 nM), and it was found to be highly selective towards interfering metal ions. Besides, the binding constant between BESN and Al3+ was found to be 3.19 × 103 M-1. Then, the validation study of BESN for Al3+ was performed based on significant analytical parameters and statistical tests. The binding of Al3+ with BESN (1:1) was probed via infrared, high-resolution mass and emission (Job's plot) spectroscopy measurements. The sensing performance of BESN could make it ideal chemosensor for real applications including vegetable, tuna fish and water samples, also for Smartphone and test-kit applications. The recovery values of the BESN to Al3+ were estimated within a range from 95.13% to 105.30% for water, 94.63% to 109.62% for tuna fish and 94.80% to 109.80% for vegetable samples. Additionally, the BESN has very low cytotoxicity and was triumphantly utilized for the recognition of Al3+ in living-cells.

A Benzothidiazole-Based Reversible Fluorescent Probe with Excellent Performances in Selectively and Sensitively Sensing of Hg2+ in Water

The development of mercury ion selective fluorescent probe is significant because it is one of toxic heavy metals and poses great risks and hazards to human health. Herein, we develop a mercury ion-selective fluorescent probe, namely IB, based on imidazole decorated benzothiadiazole that obtained by a facile palladium catalytic C-N coupling reaction. IB exhibits high selectivity and sensitivity towards mercury ion in water with nearly 32-fold fluorescent enhancement. The detection limit is calculated to be 0.93 nmol/L. In addition, the sensing of mercury ion can be conducted in a wide pH scope ranging from 4.0 to 10.0. Subsequently, the mercury ion elicits fluorescence of IB solution can be quenched by the addition of cyanide anions, showing "off-on-off" fluorescence transformation with at least 5 cycles, demonstrating the reversible sensing ability of IB. Furthermore, an INHIBIT logical detector has been developed using mercury ion and cyanide anions as inputs and fluorescence of IB as output. Significantly, IB can be utilized for mercury ion detection in real water sample.

The first tryptophan based turn-off chemosensor for Fe2+ ion detection

In this research work, we have designed and synthesized a novel Tryptophan-Quinoline conjugated turn-off chemosensor 4 for the selective detection of Fe²⁺ ion with high sensitivity (3.06 μM) among 21 metal cations such as Ag⁺, Ca⁺, Cs⁺, Cu⁺, K⁺, Na⁺, NH₄⁺, Ba²⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Mn²⁺, Ni²⁺, Pb²⁺, Zn²⁺, Al³⁺, Au³⁺, Cr³⁺ and Fe³⁺ in DMF-HEPES (1 mM, pH = 7.0, 1:1, v/v) aqueous-organic solvent system. It showed a fluorescence quenching mechanism through the blocked PET process. The optical properties, binding mode of the metal ion with the receptor, plausible electron transfer mechanism, and its practical applications have been discussed. This work will open up a new avenue in amino acid-based Fe²⁺ ion sensors.

Review on application of perylene diimide (PDI)-based materials in environment: Pollutant detection and degradation

Environment pollution is getting serious and various poisonous contaminants with chemical durability, biotoxicity and bioaccumulation have been widespreadly discovered in municipal wastewaters and surface water. The detection and removal of pollutants show great significance for the protection of human health and other organisms. Due to its distinctive physical and chemical properties, perylene diimide (PDI) has received widespread attention from different research fields, especially in the area of environment. In this review, a comprehensive summary of the development of PDI-based materials in fluorescence detection and advanced oxidation technology for environment was introduced. Firstly, we chiefly presented the recent progress about the synthesis of PDI and PDI-based nanomaterials. Then, their application in fluorescence detection for environment was presented and categorized, principally including the detection of heavy metal ions, harmful anions and organic contaminants in the environment. In addition, the application of PDI and PDI-based materials in different advanced oxidation technologies for environment, such as photocatalysis, photoelectrocatalysis, Fenton and Fenton-like reaction and persulfate activation, was also summarized. At last, the challenges and future prospects of PDI-based materials in environmental applications were discussed. This review focuses on presenting the practical applications of PDI and PDI-based materials as fluorescent probes or catalysts (especially photocatalysts) in the detection of hazardous substances or catalytic elimination of organic contaminants. The contents are aimed at supplying the researchers with a deeper understanding of PDI and PDI-based materials and encouraging their further development in environmental applications.

A simple organic probe for ratiometric fluorescent detection of Zn(II), Cd(II) and Hg(II) ions in aqueous solution via varying emission colours to distinguish one another

A bis (thiosemicarbazone) based probe has been synthesized and structurally characterized. The probe exhibits good selectivity towards Zn(II), Cd(II) and Hg(II) ions in an aqueous solution containing 95% water with ratiometric fluorescence changes. The modes of coordination of the probe with these metal ions and binding properties have been examined using different spectral techniques. The binding constants, determined using fluorescence titration data, are found to be 9.8 × 10³, 1.39 × 10⁵ and 2.03 × 10¹³ M^-1, respectively for Zn(II), Cd(II) and Hg(II) complexes. The high sensitivity of the probe has been demonstrated by the very low limit of detection i.e. 5.1, 3.4 and 0.51 μM for Zn(II), Cd(II) and Hg(II) ions, respectively. Different coordination mode of these metal ions with the probe has resulted in varying intra-ligand fluorescence (λ_em nm, Zn(II): 488, Cd(II): 470 and Hg(II): 578) among these metal complexes.

Fluorescent sensing platform for low-cost detection of Cu2+ by coumarin derivative: DFT calculation and practical application in herbal and black tea samples

A fluorogenic probe based on a coumarin-derivative for Cu2+ sensing in CH3CN/H2O media (v/v, 95/5, 5.0 μM) was developed and applied in real samples. 3-(4-chlorophenyl)-6,7-dihydroxy-coumarin (MCPC) probe was obtained by synthetic methodologies and identified by spectral techniques. The probe MCPC showed remarkable changes with a "turn-off" fluorogenic sensing approach for the monitoring of Cu2+ at 456 nm under an excitation wavelength of 366 nm. The response time of the probe MCPC was founded as only 1 min. The detection limit of the probe MCPC was recorded to be 1.47 nM. The binding constant and possible stoichiometric ratio (1:1) values were determined by Benesi-Hildebrand and Job's plot systems, respectively. The mechanism of the probe MCPC with Cu2+ was further confirmed by ESI-MS and FT-IR analyses, as well as supported by theoretical calculations. Furthermore, the probe MCPC was successfully employed for the practical applications to sense Cu2+ in different herbal and black tea samples. The proposed sensing method was also verified by ICP-OES method.

Perylene Diimide-Based Fluorescent and Colorimetric Sensors for Environmental Detection

Perylene tetracarboxylic diimide (PDI) and its derivatives exhibit excellent thermal, chemical and optical stability, strong electron affinity, strong visible-light absorption and unique fluorescence on/off features. The combination of these features makes PDIs ideal molecular frameworks for development in a broad range of sensors for detecting environmental pollutants such as heavy metal ions (e.g., Cu2+, Cd2+, Hg2+, Pd2+, etc.), inorganic anions (e.g., F-, ClO4-, PO4-, etc.), as well as poisonous organic compounds such as nitriles, amines, nitroaromatics, benzene homologues, etc. In this review, we provide a comprehensive overview of the recent advance in research and development of PDI-based fluorescent sensors, as well as related colorimetric and multi-mode sensor systems, for environmental detection in aqueous, organic or mixed solutions. The molecular design of PDIs and structural optimization of the sensor system (regarding both sensitivity and selectivity) in response to varying analytes are discussed in detail. At the end, a perspective summary is provided covering both the key challenges and potential solutions for the future development of PDI-based optical sensors.

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 simple and sensitive fluorescent sensor platform for Al3+ sensing in aqueous media and monitoring through combined PET and ESIPT mechanisms: practical applications in drinking water and bio-imaging

A novel hydrazide-based probe was designed and prepared as a fluorogenic “turn-on” sensor for Al³⁺ sensing in aqueous media.