A fluorescence turn-on sensor for iodide based on a thymine-Hg(II)-thymine complex

Iodide plays a vital role in many biological processes, including neurological activity and thyroid function. Due to its physiological relevance, a method for the rapid, sensitive, and selective detection of iodide in food, pharmaceutical products, and biological samples such as urine is of great importance. Herein, we demonstrate a novel and facile strategy for constructing a fluorescence turn-on sensor for iodide based on a T-Hg(II)-T complex (T=thymine). A fluorescent anthracene-thymine dyad (An-T) was synthesized, the binding of which to a mercury(II) ion lead to the formation of a An-T-Hg(II)-T-An complex, thereby quenching the fluorescent emission of this dyad. In this respect, the dyad An-T constituted a fluorescence turn-off sensor for mercury(II) ions in aqueous media. More importantly, it was found that upon addition of iodide, the mercury(II) ion was extracted from the complex due to the even stronger binding between mercury(II) ions and iodide, leading to the release of the free dyad and restoration of the fluorescence. By virtue of this fluorescence quenching and recovery process, the An-T-Hg(II)-T-An complex constitutes a fluorescence turn-on sensor for iodide with a detection limit of 126 nM. Moreover, this sensor is highly selective for iodide over other common anions, and can be used in the determination of iodide in drinking water and biological samples such as urine. This strategy may provide a new approach for sensing some other anions.     

A fluorescent Cd(II) based 2-D coordination polymer for highly selective detection of nitroaromatics and Hg2+

A 2-D Cd(II) coordination polymer (CP), {[Cd₂(L)₂(4,4′-bipy)₂(H₂O)?7H₂O]_n (1), has been synthesized using 5-aminoisophthalic acid (H₂L) as ligand and 4,4′-bipyridine as co-ligand. A single-crystal X-ray diffraction study shows that 1 is an infinite 2-D layer. CP 1 behaves as a highly selective and sensitive fluorescence chemosensor for detection of Hg²⁺ and 2,4,6-trinitrotoluene (TNT). Furthermore, possible emission quenching in 1 in the presence of nitroaromatics has been addressed with the aid of theoretical calculations. The calculations indicated that there are both electron and energy transfer processes, in addition to electrostatic interaction between 1 and nitroaromatics which contributes to the selective fluorescence quenching.     

A liquid state Hg(2+)-sensitive electrode

The construction and basic characteristics of a liquid-state Hg(2+)-sensitive electrode are discussed. The membrane consists of the Hg(2+) chelate of diketohydrindylidene-diketohydrindamine (DYDA) in chloroform. The range of linear response of the electrode is 10(-1)-10(-5)M Hg(2+) with a slope of 31 mV/decade. The response time of the electrode is a few seconds in concentrated solutions. The electrode may be used with good results in potentiometric titrations involving Hg(2+).     

Iminodiacetic acid-functionalized gold nanoparticles for optical sensing of myoglobin via Cu2+ coordination

A novel gold nanoparticle (AuNP)-based optical sensing system has been developed for the detection of myoglobin (Mb), which is of significant importance for early disease diagnosis. Two thiol molecules containing an iminodiacetic acid moiety (IDA) were synthesized. This detection is based on the Mb-induced aggregation of IDA-functionalized AuNPs resulting from the structures of Mb sandwiched between the functionalized AuNPs via Cu(2+) bridges in the coordination interactions of IDA-Cu(2+)-histidine residues available on the Mb surface, which was confirmed by UV-vis spectroscopy, transmission electron microscopy, dynamic light scattering, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The induction aggregation resulted in a red shift in plasmon resonance band of the AuNPs concomitant with a change in solution color from red to purple. The qualitative and quantitative detections of Mb can be achieved by colorimetric observations and UV-vis spectral measurements, respectively. The selectivity of protein assay with the functionalized AuNPs was further investigated, and it is found that the optical sensing of histidine-rich proteins is closely related to number and distribution of surface histidine residues as well as size of proteins.     

A new Hg(2+)-selective chromoionophore based on calix[4]arenediazacrown ether

A new azophenol type chromogenic ionophore based on the p-tert-butylcalix[4]arenediazacrown ether was prepared: the ionophore exhibited a pronouncedly selective chromogenic behaviour toward Hg2+ ions among the surveyed guests of alkali, alkaline earth, transition and heavy metal ions in liquid-liquid extraction experiments.     

Highly selective and sensitive visualizable detection of Hg2+ based on anti-aggregation of gold nanoparticles

For the widely used gold nanoparticles (AuNPs)-based colorimetric probes, AuNPs generally change from dispersion to aggregation state accompanying with corresponding color turning from red to blue. Although colorimetric probes based on the anti-aggregation of AuNPs show exceptional selectivity and sensitivity, few examples have been reported in literature. A facile but highly sensitive and selective colorimetric probe based on the anti-aggregation of AuNPs transferred from the deactivation of aggregation agent 4,4′-dipyridyl by Hg²⁺ was developed in this work. This reported probe is suitable for real-time detection of Hg²⁺ in water with a detection limit of 3.0 ppb for Hg²⁺, and exhibits a selectivity toward Hg²⁺ by two orders of magnitude over other metal ions. The dynamic range of this probe can be conveniently tuned by adjusting the amount of 4,4′-dipyridyl used.     

A new quinoline-based chemosensor in ratiometric sensing of Hg2+ ions

A new quinoline-based chemosensor 1 has been designed and synthesised. Its metal ion-binding properties have been documented in organic and aqueous organic solvents. While chemosensor 1 recognises Hg²⁺ ions (K _a = 2.15 × 10⁴ M^? 1) by exhibiting ratiometric change in emission in CHCl₃/CH₃OH (1:1, v/v), under similar condition both Zn²⁺ and Cd²⁺ ions are sensed by significant non-ratiometric increase in emission with measurable red shift. In DMSO/H₂O (5:95, v/v), the sensor 1 exhibits a greater selectivity towards Hg²⁺ ions (K _a = 9.20 × 10³ M^? 1) over the other metal ions examined.     

Detection of mercury(II) based on Hg2+ -DNA complexes inducing the aggregation of gold nanoparticles

A DNA-Au NP probe for sensing Hg2+ using the formation of DNA-Hg2+ complexes through thymidine (T)-Hg2+ -T coordination to control the negative charge density of the DNA strands-thereby varying their structures-adsorbed onto Au NPs.     

A new "turn-on" chemodosimeter for Hg2+: ICT fluorophore formation via Hg(2+)-induced carbaldehyde recovery from 1,3-dithiane

A novel sensitive and specific Hg(2+) chemodosimeter, derived from 1',3'-dithiane-substituted 2,1,3-benzoxadiazole, displays "turn-on" fluorescent and colorimetric responses via an Hg(2+)-triggered aldehyde recovery reaction. Its potential to monitor Hg(2+) in living organisms has been demonstrated using zebrafish larvae.     

A novel Hg2+ fluorescence sensor TPE-TSC based on aggregation-induced emission

Abstract

A fluorescent sensor TPE-TSC with aggregation induced emission (AIE) characteristic is synthesized for detecting Hg²⁺ by attaching thiosemicarbazide (TSC) unit into tetraphenylethylene (TPE) group. TPE-TSC exhibits intense green emission in DMSO/H₂O (V:V?=?1:9) solution with the formation of the aggregation. TPE-TSC shows outstanding fluorescence quenching toward Hg²⁺ over other metal ions due to the formation of complex TPE-TSC/Hg²⁺ with a 2:1 binding ratio. The detection limit of TPE-TSC for Hg²⁺ is 1?×?10^?5 mol·L^?1.     

Highly selective ratiometric fluorescent sensing for Hg(2+) and Au(3+), respectively, in aqueous media

A nonsulfur probe based on a 1,8-naphthalimide and alkyne conjugate for the ratiometric fluorescent sensing for Hg(2+) and Au(3+) through the tuning of pH in different aqueous solutions is described. This work provides a novel reaction-based approach for selective recognition of these two ions with significant change of fluorescence color and constitutes the first ratiometric case for Au(3+).     

A new sensitive reagent for identifying Ag(+) and Hg(2+)

This paper describes the synthesis of a new reagent: N,N′-difuroyl thiourea for the purpose of improving coordination capacity of thiourea compounds. It has been characterized by IR, UV, MS and ¹H-NMR as well as elemental analytical data. According to the studies on its analytical performance, it is found that this reagent can be used to identify Ag⁺ and Hg²⁺. Both of their sensitivities and selectivities are the best in all methods for the time being. The new methods are simple and convenient, and can provide satisfactory results on synthetic and standard samples.     

A "turn-on" electrochemiluminescent biosensor for detecting Hg2+ at femtomole level based on the intercalation of Ru(phen)3(2+) into ds-DNA

A well-designed oligonucleotide functionalized for Hg(2+) identification and Ru(phen)(3)(2+) intercalation is used to develop a "turn-on" electrochemiluminescent (ECL) biosensor for the determination of Hg(2+) in a drop (10 μL) of sample.     

A selective fluorescent probe of Hg2+ based on triazole-linked 8-oxyquinoline calix[4]arene by click chemistry

Calixarene compound 1 with two 8-oxyquinoline subunits was synthesised using ‘click’ chemistry. Compound 1 shows strong fluorescence quenching by Hg²⁺ and lower pH. Using the fluorescence behaviour of 1 towards Hg²⁺ and lower pH, a NOR (not an OR) logic gate was established.     

Ratiometric fluorescent chemosensor for Hg(2+) based on heptamethine cyanine containing a thymine moiety

Based on a T-Hg(2+)-T binding mode, a sensitive ratiometric fluorescent chemosensor for aqueous Hg(2+) was developed with a heptamethine cyanine chromophore containing a thymine moiety.