Design and Synthesis of a Terbium(III) Complex-Based Luminescence Probe for Time-Gated Luminescence Detection of Mercury(II) Ions

Time-gated luminescence detection technique using lanthanide complexes as luminescent probes is a useful and highly sensitive method. However, the effective application of this technique is limited by the lack of the target-responsive luminescent lanthanide complexes that can specifically recognize various analytes in aqueous solutions. In this work, a dual-functional ligand that can form a stable complex with Tb³⁺ and specifically recognize Hg²⁺ ions in aqueous solutions, N,N,N ¹ ,N ¹ -{[2,6-bis(3′-aminomethyl-1′-pyrazolyl)-4-[N,N-bis(3″,6″-dithiaoctyl)-aminomethyl]- pyridine]} tetrakis(acetic acid) (BBAPTA), has been designed and synthesized. The luminescence of its Tb³⁺ complex is weak, but can be effectively enhanced upon reaction with Hg²⁺ ions in aqueous solutions. The luminescence response investigations of BBAPTA-Tb³⁺ to various metal ions indicate that the complex has a good luminescence sensing selectivity for Hg²⁺ ions, but not for other metal ions. Thus a highly sensitive time-gated luminescence detection method for Hg²⁺ ions was developed by using BBAPTA-Tb³⁺ as a luminescent probe. The dose-dependent luminescence enhancement of the probe shows a good linearity with a detection limit of 17 nM for Hg²⁺ ions. These results demonstrated the efficacy and advantages of the new Tb³⁺ complex-based luminescence probe for the sensitive and selective detection of Hg²⁺ ions.     

A Fluorescent Chemodosimeter for Hg2+Based on a Spirolactam Ring-Opening Strategy and its Application Towards Mercury Determination in Aqueous and Cellular Media

A novel fluorescent chemosensor rhodamine B phenyl hydrazide (RBPH) for Hg²⁺ was designed and synthesized. This probe is highly sensitive, selective, and irreversible for Hg²⁺ and exhibits fluorescent response at 580 nm. RBPH also displayed detectable color change from colorless to pink upon treatment with Hg²⁺. This property has been utilized as naked eye detection for Hg²⁺ in various industrial samples. Fluorescence microscopic experiments demonstrated that this chemosensor is cell permeable and can be used for fluorescence imaging of Hg²⁺ in cellular media. This probe can detect Hg²⁺ with good linear relationships from 1 to 100 nM with r?=?0.99983 and the limit of detection were found to be 0.019 nM with?±?0.91 % RSD at 10 nM concentrations.     

Synthesis and Analytical Application of a Novel Fluorescent Hg2+ Probe 3′, 6′-Bis(Diethylamino)-2-((2,4-Dimethoxybenzylidene)Amino)Spiro[Isoindoline-1,9′-Xanthene]-3-Thione

A novel probe, 3′,6′ - bis(diethylamino) -2- ((2,4-dimethoxybenzylidene)amino) spiro [isoindoline-1,9′-xanthene]-3-thione (RBS), was designed and synthesized. Its structure was characterized with elemental analysis, IR spectra and ¹H NMR. The probe displayed highly selective and sensitive recognition of Hg²⁺. Reacting with mercury ions in aqueous solution, its fluorescence intensity was enhanced significantly, while its color was changed from colorless to pink. So, a new fluorescence method of detection of Hg²⁺ was proposed. Its dynamic response concentration range and detection limit for Hg²⁺ were 5.00?×?10^?9 M to 1.00?×?10^?6 M detected and 1.83?×?10^?9 M, respectively. Satisfying results were obtained when the probe was applied to detect spiked Hg²⁺ in samples.     

Electrospun nanofibers decorated with bio-sonochemically synthesized gold nanoparticles as an ultrasensitive probe in amalgam-based mercury (II) detection system

In this study, bio-ultrasound-assisted synthesized gold nanoparticles using Gracilaria canaliculata algae have been immobilized on a polymeric support and used as a glassy probe chemosensor for detection and rapid removal of Hg²⁺ ions. The function of the suggested chemosensor has been explained based on gold-amalgam formation and its catalytic role on the reaction of sodium borohydride and rhodamine B (RhB) with fluorescent and colorimetric sensing function. The catalyzed reduction of RhB by the gold amalgam led to a distinguished color change from red and yellow florescence to colorless by converting the amount of Hg²⁺ deposited on Au-NPs. The detection limit of the colorimetric and fluorescence assays for Hg²⁺ was 2.21 nM and 1.10 nM respectively. By exposing the mentioned colorless solution to air for at least 2 h, unexpectedly it was observed that the color and fluorescence of RhB were restored. Have the benefit of the above phenomenon a recyclable and portable glass-based sensor has been provided by immobilizing the Au-NPs and RB on the glass slide using electrospinning. Moreover, the introduced combinatorial membrane has facilitated the detection and removal of Hg²⁺ ions in various Hg (II)-contaminated real water samples with efficiency of up to 99%.     

A Disulfide-Linked Naphthalimide Dimer for Hg(II) Detection in Aqueous Solution

A disulfide linked naphthalimide dimer probe was designed for mercury ion (Hg²⁺) recognition in this work. The recognition was based on the strong affinity of mercury for sulfur. The experimental results revealed that the probe exhibited high selectivity and sensitivity toward Hg²⁺ in comparison to other metal ions via a turn-on and reversible response to Hg²⁺ in neutral buffer solution. More importantly, the probe demonstrated a linear response for Hg²⁺ over a concentration range from 0 to 150 μM with a detection limit of 0.38 μM, which is just the limit of the safe concentration for humans. Upon addition of 150 μM Hg²⁺, the enhancement of fluorescence reached a maximum (∼7-fold). The performances of the probe indicated that it could meet the selectivity requirements for biomedical and environmental application and also was sensitive enough to detect Hg²⁺ in environmental and biological samples.     

Metallophilic Bond‐Induced Quenching of Delayed Fluorescence in Au25@BSA Nanoclusters

The metallophilic bond is a weak interaction between closed‐shell ions and has been widely used a probe for various sensing of toxic chemicals for environmental safety concerns. Here, the interaction between Au nanoclusters (NCs) and metallic ions (mercury (Hg²⁺) and copper (Cu²⁺) ions) is explored using steady‐state and time‐resolved luminescence and transient absorption measurements. For Hg²⁺ ions, the delayed fluorescence (DF) of bovine serum albumin (BSA) protected Au₂₅ (Au₂₅@BSA) NCs is quenched via an effective triplet state electron transfer through the metallophilic bond. However, the Cu²⁺ ions do not alter the DF in Au₂₅@BSA NCs because of the absence of the metallophilic interaction. Furthermore, for Au₈@BSA and Au₁₀@histidine, in which there are no Au⁺ ions on the surface, the fluorescence is not quenched by Hg²⁺ ions. Such a novel triplet electron transfer process through metallophilic bonds are observed and reported for the first time. The reduction of the reverse intersystem crossing is the crucial for Hg²⁺ ion sensing in the fluorescent Au₂₅@BSA NCs.     

A New Reactive 1,8-Naphthalimide Derivative for Highly Selective and Sensitive Detection of Hg<Superscript>2+</Superscript>

A 1,8-naphthalimide derivative with a reactive aliphatic hydroxyl was designed and synthesized as a fluorescent probe. Its structure was characterized by IR, ¹H NMR, ¹³C NMR, LC-MS and HPLC. The probe showed high selectivity and sensitivity to Hg²⁺ over other metal ions such as Pb²⁺, Na⁺, K⁺, Cd²⁺, Cr³⁺, Zn²⁺, Cu²⁺, Ni²⁺, Ca²⁺, Fe³⁺, Fe²⁺, Co²⁺, Mn²⁺ and Mg²⁺ in MeCN/H₂O (15/85, v/v). The increase in fluorescence intensity was linearly proportional to the concentration of Hg²⁺ in the range of 18–40 μM with a detection limit of 1.38 × 10^?7 mol/L. The probe could work in a pH span of 4.3–9.0 and respond to Hg²⁺ quickly with strong anti-interference ability. Job’s plot suggested a 1:2 complex of the probe and Hg²⁺.     

Novel Pyrazoline-Based Selective Fluorescent Sensor for Hg2+

This paper presents the preparation of a pyrazoline compound and the properties of its UV–Vis absorption and fluorescence emission. Moreover, this compound can be used to determine Hg²⁺ ion with selectivity and sensitivity in the EtOH:H₂O?=?9:1 (v/v) solution. This sensor forms a 1:1 complex with Hg²⁺ and shows a fluorescent enhancement with good tolerance of other metal ions. This sensor is very sensitive with fluorometric detection limit of 3.85?×?10^?10 M. In addition, the fluorescent probe has practical application in cells imaging.     

Detection of Fe3+ and Hg2+ Ions by Using High Fluorescent Carbon Dots Doped With S And N as Fluorescence Probes

In this paper, carbon quantum dots (N-S-CDs) containing sulfur and nitrogen were synthesized using citric acid and thiourea. The average particle size of N-S-CDs is 8 nm. The N-S-CDs surface contains various of functional groups, which has good water solubility. The fluorescence quantum yield of N-S-CDs is as high as 36.8%. N-S-CDs emits strong blue fluorescence in aqueous solution and has good photostability in neutral and alkaline NaCl solution. N-S-CDs has unique selectivity and high sensitivity to Fe³⁺ and Hg²⁺ ions, and the lowest detection limits are 1.4 μM and 0.16 μM, respectively. Under the interference of other metal ions, Fe³⁺ and Hg²⁺ ions can still effectively and stably quench the fluorescence of N-S-CDs. In addition, in the detection of actual samples, N-S-CDs can effectively detect Fe³⁺ and Hg²⁺ ions in tap water and lake water.

     

Both “Naked-Eye” and Fluorescent Sensor for Hg2+ Based upon 8-Hydroxyquinoline

A chemosensor, 2,2′-(1,4-phenylenedivinylene)bis-8-acetoxyquinoline (1), its fluorescent sensing behavior toward representative alkali ions (Na⁺, K⁺), alkaline earth ions (Mg²⁺, Ca²⁺), and transition-metal ions (Ni²⁺, Cu²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Cd²⁺) was intensively investigated. The compound (1) exhibited pronounced Hg²⁺ selective on–off-type fluoroionophoric properties among the representative ions in DMF/ethanol (1:9, v/v) solution. Moreover, the highly Hg²⁺-selective fluorescence quenching property in conjunction with a visible colorimetric change from colorless to light yellow can be observed, leading to potential fabrication of both “naked-eye” and fluorescent detection of Hg²⁺.     

A Fluorescence Turn-on Sensor for Hg<Superscript>2+</Superscript> with a Simple Receptor Available in Sulphide-Rich Environments

Detection of Hg²⁺ in complex natural environmental conditions is extremely challenging, and no entirely successful methods currently exist. Here we report an easy-to-prepare fluorescent sensor B3 with 2-aminophenol as Hg²⁺ receptor, which exhibits selective fluorescence enhancement toward Hg²⁺ over other metal ions. Especially, the fluorescence enhancement was unaffected by anions and cations existing in environment and organism. Moreover, B3 can detect Hg²⁺ in sulphide-rich environments without cysteine, S^2- or EDTA altering the fluorescence intensity. Consequently, B3 is capable of distinguishing between safe and toxic levels of Hg²⁺ in more complicated natural water systems with detection limit ≤2 ppb.     

Rhodamine B-based “turn-on” fluorescent and colorimetric chemosensors for highly sensitive and selective detection of mercury (II) ions

Two novel macromolecules based on 2-[3-(2-aminoethylsulfanyl)propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-B moieties, 1 and 2, were prepared and utilized as fluoroionophores and chromophores for the optical detection of Hg²⁺ ions. The sensors were readily prepared by a conventional two-step synthesis. Especially, sensor 1 exhibits high sensitivity and selective OFF–ON fluorescence enhancement and chromogenic change upon binding to Hg²⁺, which served as a “naked-eye” indicator by a noticeable color change of the solution (from colorless to pink–red color). 1 is shown to discriminate various competing metal ions, particularly Ag⁺ and Cu²⁺, as well as Cd²⁺, Na⁺, Li⁺, K⁺, Ba²⁺, Co²⁺, Ni²⁺, Mg²⁺, Mn²⁺ and Al³⁺, with a detection limit of 10 ppb.     

Differential pulse anodic stripping voltammetric determination of Hg2+ at poly(Eriochrome Black T)-modified carbon paste electrode

The electrochemical behavior of Hg²⁺ was investigated in poly(Eriochrome Black T)-modified carbon paste electrode (CPE) using cyclic voltammetry (CV). Poly(Eriochrome Black T) was prepared in an alkaline medium on the surface of the CPE using a solution of Eriochrome Black T with the CV technique. The electrochemical impedance study revealed a better charge transfer kinetics at the modified electrode. The effects of variation of the experimental conditions, such as the concentration of electrolytes, pH, deposition time, and the deposition potential, which maximize current efficiency were studied. The optimum response of Hg²⁺ was observed in 1.0 M KCl solution. The differential pulse anodic stripping voltammetric technique was employed successfully to detect Hg²⁺, which gave a good linear response at low concentration levels of Hg²⁺. The detection limit was found to be 2.2?×?10^?10 M (S/N?=?3), which is comparable with that achieved in multiwall carbon nanotube-modified electrode. The remarkable electroanalytical performance of the modified electrode makes it amenable to employ it successfully as an electrochemical sensor for the determination of hazardous pollutant Hg²⁺ in environmental samples.     

DNA hybridization and phosphinothricin acetyltransferase gene sequence detection based on zirconia/nanogold film modified electrode

This study reports a novel electrochemical DNA biosensor based on zirconia (ZrO₂) and gold nanoparticles (NG) film modified glassy carbon electrode (GCE). NG was electrodeposited onto the glassy carbon electrode at 1.5 V, and then zirconia thin film on the NG/GCE was fabricated by cyclic voltammetric method (CV) in an aqueous electrolyte of ZrOCl₂ and KCl at a scan rate of 20 mV/s. DNA probes were attached onto the ZrO₂/NG/GCE due to the strong binding of the phosphate group of DNA with the zirconia film and the excellent biocompatibility of nanogold with DNA. CV and electrochemical impedance spectroscopy (EIS) were used to characterize the modification of the electrode and the probe DNA immobilization. The electrochemical response of the DNA hybridization was measured by differential pulse voltammetry (DPV) using methylene blue (MB) as the electroactive indicator. After the hybridization of DNA probe (ssDNA) with the complementary DNA (cDNA), the cathodic peak current of MB decreased obviously. The difference of the cathodic peak currents of MB between before and after the hybridization of the probe DNA was used as the signal for the detection of the target DNA. The sequence-specific DNA of phosphinothricin acetyltransferase (PAT) gene in the transgenic plants was detected with a detection range from 1.0 × 10⁻¹⁰ to 1.0 × 10⁻⁶ mol/L, and a detection limit of 3.1 × 10⁻¹¹ mol/L.     

A Colorimetric and Fluorescent Indicator for Hg<Superscript>2+</Superscript> Detection Based on Cinnamamide Group-Containing Rhodamine Derivative

A colorimetric and fluorescent indicator based on cinnamamide group-containing rhodamine derivative was synthesized for the detection of Hg²⁺. The rhodamine B and cinnamamide were connected via ethylenediamine as a bridging molecule through a condensation reaction to obtain a colorimetric and fluorescent indicator for the detection of Hg²⁺ in H₂O-EtOH (4:1, v/v). The indicator was excellent in the selectivity of Hg²⁺ and was almost unaffected by other common ions such as Na⁺, K⁺, Mg²⁺, Fe³⁺, Cu²⁺, Zn²⁺, Cr³⁺. The Hg²⁺-containing aqueous solution turned from colorless to red within 7 min after the addition of the indicator, and had an absorption peak at 564 nm in UV-vis, which implies a significant colorimetric phenomenon. Their characteristic peaks varied with the Hg²⁺ content, and they reached a linear relationship at low concentrations. The binding stoichiometry proved to be 1:1. The lowest detection limit was 4.1?×?10^?7 mol/L, ranging from acidic to neutral.     

A Novel Hg<Superscript>2+</Superscript> Selective Ratiometric Fluorescent Chemodosimeter Based on an Intramolecular FRET Mechanism

A irreversible Hg²⁺ selective ratiometric fluorescence probe FR, a fluorescein fluorophore linked to a rhodamine B hydrazide by a thiourea spacer, was designed and synthesized. The developed probe FR exhibited great ratiometric fluorescence enhancement and remarkable yellow-magenta color change toward Hg²⁺ with excellent selectivity in aqueous acetone solution, and the ratiometric fluorescence response to Hg²⁺ was not interfered by other metal cations including Fe³⁺, Co²⁺, Ni²⁺, Cr³⁺, Zn²⁺, Pb²⁺, Cd²⁺, Ca²⁺, Mg²⁺, Ba²⁺ and Mn²⁺. The linear range and the detection limit of this supposed ratiometric fluorescence method for Hg²⁺ were 0.0–10.0 × 10⁻⁶ and 5 × 10⁻⁸ M, respectively.     

Synthesis and Characterization of New Light Emitter Symmetrical Phenoxazinium Salt and Its Potential Application as Sensor for Assessment of Hg2+

The sensitization of the excited triplet state of a novel symmetrical Bis(dialkylamino)phenoxazinium salt was developed in the presence of Hg²⁺. This effect was used to determine the concentration of Hg²⁺ in different water samples. The phenoxazinium salt sensor was characterized by different spectroscopic tools such as: UV, FTIR, NMR and fluorescence spectra. The sensor has an emission band at 347 nm in DMSO. Hg²⁺ in DMSO at pH 5.6 can remarkably quench the fluorescence intensity of the sensor at 347 nm and a new band was appeared at 436 nm due to the strong complex formation between Hg²⁺ and sensor. The quenching of the band intensity at 347 and the enhancement of the intensity of the new band at 436 were used to determine the Hg²⁺ in different waste water samples. The dynamic range found for the determination of Hg²⁺ concentration is 8.7?×?10^-10 – 1.4?×?10^-6 mol L^?1 with a detection limit of 5.8?×?10^?10 mol L^?1 and quantification detection limit of 1.8?×?10^-9 mol L^-1.     

A Dansyl-Rhodamine Ratiometric Fluorescent Probe for Hg<Superscript>2+</Superscript> Based on FRET Mechanism

Based on resonance energy transfer (FRET) from dansyl to rhodamine 101, a new fluorescent probe (compound 1) containing rhodamine 101 and a dansyl unit was synthesized for detecting Hg²⁺ through ratiometric sensing in DMSO aqueous solutions. This probe shows a fast, reversible and selective response toward Hg²⁺ in a wide pH range. Hg²⁺ induced ring-opening reactions of the spirolactam rhodamine moiety of 1, leading to the formation of fluorescent derivatives that can serve as the FRET acceptors. Very large stokes shift (220 nm) was observed in this case. About 97-fold increase in fluorescence intensity ratio was observed upon its binding with Hg²⁺.     

Developing a novel fluorescence chemosensor by self-assembly of Bis-Schiff base within the channel of mesoporous SBA-15 for sensitive detecting of Hg ions

A novel fluorescence chemosensor for Hg²⁺ ion has been developed by the assembly of fluorescence Bis-Schiff base PMBA within the channels of CPTES-modified SBA-15. The ordered porous structure of SBA-15 is still retained on the hybrid chemosensor material PMBA-SBA. A remarkable fluorescence quenching of PMBA-SBA by Hg²⁺ ion was attributed to heavy atom effect of Hg²⁺ ion. The linear detecting range of the hybrid mesoporous chemosensor for Hg²⁺ ion is 2-15 μM and the lowest detection limit is 0.6 μM in ethanol/water (9:1, v/v) solution.     

A Highly Selective Turn on Fluorescence Sensor for Hg2+ Based on Rhodamine Derivative

A novel fluorescent rhodamine based chemosensor (E)-3′,6′-bis(diethylamino)-2-((2-(pyridin-2-ylmethoxy)benzylidene)amino)spiro[isoindoline-1,9′-xanthen]-3-one, RSP, had been successfully developed and well characterized by NMR, FT-IR and Mass spectroscopy. The chemosensor exhibits high selectivity for Hg²⁺ over other ions (Ag⁺, Pb²⁺, Cu²⁺, Ni²⁺, Fe³⁺, Co²⁺, Zn²⁺ and Cd²⁺) with fluorescence enhancement in ethanol solution. More over the detection limit of the sensor is in the 10^?6 M level. The binding ratio of RSP-Hg²⁺ complex was determined to be 1:1 according to the Job plot. Test strips based on RSP were fabricated, which showed the application of the sensor for detection of mercuric ions in water by naked eyes.