Chemosensing hybrid materials: Chalcones‐functionalized cage‐like mesoporous SBA‐16 material for highly selective detection of toxic metal ions

Highly selective and low‐cost optical nanosensors of organic–inorganic hybrid materials for heavy metal ions detection have been prepared via the functionalization of mesoporous silica (SBA‐16) with chalcone fluorescent chromophores. The successful attachment of organic chalcone moieties and preservation of original structure of SBA‐16 after the anchoring process were confirmed by extensive characterizations using various techniques like Fourier transform infrared and UV–visible spectroscopies, transmission electron microscopy, nitrogen adsorption–desorption isotherms, low‐angle X‐ray diffraction and thermogravimetric analysis. The colorimetric behaviour, selectivity and sensitivity were also investigated. The optical nanosensors respond selectively to heavy metal ions, such as Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺, with observable colour changes in 0.01 M Tris–HCl aqueous buffer solution. Also, the optical sensing ability of the investigated nanosensors to the mentioned metal ions was investigated using steady‐state absorption and emission techniques. Significant increase in the absorption spectra and a static quenching in the emission spectra are observed upon adding various concentrations of the studied metal ions. The spectral changes as well as the observable colour changes suggest that the investigated nanosensors are suitable for simple, economic, online analysis and remote design of these toxic metal ions with fast kinetic responses. Finally, the low detection limits for all the studied metals are in good agreement with those recommended by both the US Environmental Protection Agency and World Health Organization, except for Hg²⁺ and Cd²⁺, indicating that the investigated nanosensors have hypersensitivity, selectivity and better recognition for all the studied metal ions.     

Polymer‐based colorimetric and “turn off” fluorescence sensor incorporating benzo[2,1,3]thiadiazole moiety for Hg2+ Detection

A conjugated polymer was synthesized by the polymerization of 4,7‐dibromobenzo[2,1,3]thiadiazole ( M‐1 ) with tri{1,4‐diethynyl‐2,5‐bis(2‐(2‐methoxyethoxy)‐ethoxy)}‐benzene ( M‐2 ) via Pd‐catalyzed Sonogashira reaction. The polymer shows strong orange fluorescence. The responsive optical properties of the polymer on various metal ions were investigated through photoluminescence and UV–vis absorption measurements. The polymer displays highly sensitive and selective on‐off Hg²⁺ fluorescence quenching property in tetrahydrofuran solution in comparison with the other cations including Mg²⁺, Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Cd²⁺, and Pb²⁺. More importantly, the fluorescent color of the polymer sensor disappears after addition of Hg²⁺, which could be easily detected by naked eyes. The results indicate that this kind of polymer sensor incorporating benzo[2,1,3]thiadiazole moiety as a ligand can be used as a novel colorimetric and fluorometric sensor for Hg²⁺ detection. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

基于四丹磺酰胺杯[4]芳烃的汞离子荧光化学传感器

我们方便地合成了上沿修饰四丹磺酰胺基团的杯[4]芳烃衍生物1,发现该化合物在含50％水的乙腈中显示出对汞离子高选择性和灵敏性的识别作用,竞争实验表明多数金属离子对其检测干扰较小。机理研究结果表明荧光萃灭源于由丹磺酰胺基团到汞离子的光致电子转移过程。另外,通过研究1和1-Hg2+的荧光衰减实验,以及对比双丹磺酰胺杯[4]芳烃2和单丹磺酰胺杯[4]芳烃3对汞离子的识别作用,发现化合物1的四丹磺酰胺基团具有很好的预组织和协同作用。化合物1对汞离子的检测限为3.41×10-6 mol·L-1,这可以使1成为一个潜在的汞离子荧光化学传感器。     

Detection of Hg2+ and F− Ions by Using Fluorescence Switching of Quantum Dots in an Au‐Cluster–CdTe QD Nanocomposite

A single probe of an Au nanocluster–CdTe quantum dots nanocomposite has been developed by using tripeptide‐capped CdTe quantum dots (QD) and bovine serum albumin (BSA) protein‐conjugated Au₂₅ nanocluster (NC) for detection of both Hg²⁺ ion and F^? ion. The formation of Au‐NC–CdTe QD nanocomposite has been confirmed by TEM, steady state and time resolved spectroscopy, CD and FTIR studies. A significant signal off (74 % PL quenching at 553 nm) phenomenon of this nanocomposite is observed in presence of 6.56×10^?7 M Hg²⁺ ion, due to salt‐induced aggregation. However, a dramatic PL enhancement (128 %) of the Au‐NC–CdTe QD nanocomposite is observed in presence of 8.47×10^?7 M F^? anion. The calculated limit of detections (LOD) of Hg²⁺ ion concentration and F^? ion concentration are found to be 9 and 117 nM , respectively, which are within the safety range set by the United States Environment Protection Agency. Thus, the simple Au‐NC–CdTe QD optical‐based sensor is very useful to detect both toxic cations and anions.     

Synthesis of N,N,N-4,4＂-Di-（4-methylphenyl）-2,2＇：6＇,2＂- terpyridine-N,N,N-tris（isothiocyanato） Ruthenium（Ⅱ） and Application to Colorimetric Hg^2＋ Sensor

A terpyridine derivative DPTP [di-（4-methylphenyl）-2,2＇：6＇,2＂-terpyridine] was conveniently synthesized from 2-bromopyridine via halogen-dance reaction, Kharash coupling and Stille coupling reaction. Then its corresponding ruthenium complex Ru-DPTP [N,N,N-4,4＇＇-di-（4-methy,phenyl）-2,2＇：6＇,2＂-terpyridine-N,N,N-tris（is,-thi,cyanat,）- ruthenium（H） ammonium] was obtained and fully characterized by IR, UV-Vis, ESI MS and elemental analysis. The MLCT absorption band of Ru-DPTP was blue-shifted from 570 to 500 nm upon addition of Hg^2＋. Among a series of surveyed metal ions, the complex showed a unique recognition to Hg^2＋, indicating that it can be used as a selective colorimetric sensor for Hg^2＋.     

A Schiff base‐grafted nanoporous silica material as a reversible optical probe for Hg2+ ion in water

A novel organic–inorganic silica‐based fluorescent probe was designed, synthesized and characterized by different techniques such as XRD, BET, TGA, and FT‐IR. The fluorescence properties of the probe were studied in the presence of a variety of metal‐ions in water. The results revealed that various metal‐ions negligibly vary the emission intensity of the probe except for Hg²⁺, which quenched the intensity dramatically. The selectivity of the probe toward Hg²⁺ ion was further investigated in the presence of common competing metal‐ions and the results demonstrated the high selectivity of the probe toward Hg²⁺ ion. The fluorescence emission of the probe was also studied as a function of the concentration of Hg²⁺ ion. A nanomolar limit of detection was estimated for Hg²⁺, indicating a high sensitivity. Furthermore, the probe showed INHIBIT‐type logic behavior with Hg²⁺ and H⁺ as inputs. Also, the optimum pH range was studied in addition to reversibility and real world applicability of the probe.     

A New Fluorescent Chemosensor for Metal Ions Based upon 1,8‐Naphthalimide and 8‐Hydroxyquinoline

A new fluorescent chemosensor based upon 1,8‐naphthalimide and 8‐hydroxyquinoline was synthesized, and its fluorescent properties in the presence of different metal cations (Hg²⁺, Ag⁺, Zn²⁺, Fe²⁺, Cd²⁺, Pb²⁺, Ca²⁺, Cu²⁺, Mg²⁺, and Ba²⁺) were investigated. It displayed fluorescence quenching with some heavy and transition metal (HTM) ions, and the quenching strongly depended on the nature of HTM ions.     

Probing the mechanism of the interaction between l‐cysteine‐capped‐CdTe quantum dots and Hg2+ using capillary electrophoresis with ensemble techniques

A good understanding of the mechanism of interaction between quantum dots (QDs) and heavy metal ions is essential for the design of more effective sensor systems. In this work, CE was introduced to explore how l ‐cysteine‐capped‐CdTe QDs (l ‐cys‐CdTe QDs) interacts with Hg²⁺. The change in electrophoretic mobility can synchronously reflect the change in the composition and property of QDs. The effects of the free and capping ligands on the system are discussed in detail. ESI‐MS, dynamic light scattering (DLS), zeta potential, and fluorescence (FL) were also applied as cooperative tools to study the interaction mechanism. Furthermore, the interaction mechanism, which principally depended on the concentration of Hg²⁺, was proposed reasonably. At the low concentration of Hg²⁺, the formation of a static complex between Hg²⁺ and the carboxyl and amino groups of l ‐cys‐CdTe QDs surface was responsible for the FL quenching. With the increase of Hg²⁺ concentration, the capping l ‐cys was stripped from the surface of l ‐cys‐CdTe QDs due to the high affinity of Hg²⁺ to the thiol group of l ‐cys. Our study demonstrates that CE can reveal the mechanism of the interaction between QDs and heavy metal ions, such as FL quenching.     

Synthesis of Novel Dibenzo‐18‐crown‐6‐ ether‐Functionalized Benzimidazoles and its Applications in Colorimetric Recognition to Hg2+ and as Antifungal Agents

New crown ether‐functionalized benzimidazoles was designed and synthesized via formylation of dibenzo‐18‐crown‐6 followed by condensation with different o‐phenylene diamines. The complexation properties of crown ether‐functionalized benzimidazoles with various metals (K⁺, Ca²⁺, Ba²⁺, Co²⁺, Hg²⁺) were examined using UV–vis spectroscopy. Hg²⁺ showed a well‐defined peculiar absorption maximum at 366 nm exclusively. All these newly synthesized compounds were screened for antifungal activity against Aspergillus niger and Aspergillus oryzae, respectively.     

Polymer‐based fluorescence sensors incorporating chiral binaphthyl and benzo[2,1,3]thiadiazole moieties for Hg2+ detection

Three chiral polymers P‐1 , P‐2 , and P‐3 could be obtained by the polymerization of (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2, 2′‐binaphthol (R‐M‐1) , (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2,2′‐bisoctoxy‐1,1′‐binaphthyl ( R‐M‐2 ), and (R)‐6,6′‐dibutyl‐3,3′‐diiodo‐2,2′‐bis (diethylaminoethoxy)‐1,1′‐binaphthyl ( R‐M‐3 ) with 4,7‐diethynyl‐benzo[2,1,3]‐thiadiazole ( M‐1) via Pd‐catalyzed Sonogashira reaction, respectively. P‐1 , P‐2 , and P‐3 can show pale red, blue–green, and orange fluorescence. The responsive optical properties of these polymers on various metal ions were investigated by fluorescence spectra. Compared with other cations, such as Co²⁺, Ni²⁺, Ag⁺, Cd²⁺, Cu²⁺, and Zn²⁺, Hg²⁺ can exhibit the most pronounced fluorescence response of these polymers. P‐1 and P‐2 show obvious fluorescence quenching effect upon addition of Hg²⁺, on the contrary, P‐3 shows fluorescence enhancement. Three polymer‐based fluorescent sensors also show excellent fluorescence response for Hg²⁺ detection without interference from other metal ions. The results indicate that these kinds of tunable chiral polybinaphthyls can be used as fluorescence sensors for Hg²⁺ detection. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 997–1006, 2010     

Meta‐linked and para‐linked water‐soluble poly(arylene ethynylene)s with amino acid side chains: Effects of different linkage on Hg2+ ion sensing properties in aqueous media

Water‐soluble, meta‐ and para‐linked poly(arylene ethynylene)s containing L ‐aspartic acid‐functionalized fluorene units (P1 and P2) and their model compounds (M1 and M2) have been synthesized, and their photophysical properties and fluorescent sensing properties were investigated in aqueous solution. P1 and M1 with the meta‐linkage show blue‐shifted absorption and emission spectra, and decreased photoluminescence quantum yields compared with those of P2 and M2 with para‐linkage. Their absorption and fluorescence spectra are pH dependent perhaps due to the aggregation of the polymer chains at low pH values. In buffer solutions, both polymers and their model compounds exhibit the excellent selectivity and sensitivity to Hg²⁺ over other common metal ions. Furthermore, the quenching constant and detection limit of P1 are determined to be 1.04 × 10⁷ M^?1 and 10 nM, and show the higher sensitivity compared to P2. Further comparison of their model compounds reveal that the sensitivity and quenching efficiency of M1 is also higher than that of M2, indicating that the meta‐linkage pattern plays a key role in improving their Hg²⁺ ion sensing properties. In addition, both meta‐ and para‐linked polymers exhibit the higher quenching efficiency than their model compounds due to the amplified fluorescence response of conjugated polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Hg2+‐Induced In Situ Generated Radical Cation of (S)‐BINOL‐Based Polymer for Highly Enantioselective Recognition of Phenylalaninol

Phenylalaninol enantiomers are one of the most important chiral compounds due to its presence in biologically active molecules and pharmaceutical products. In this paper, a novel chiral fluorescence polymer sensor incorporating (S)‐BINOL and oligomeric aniline via a nucleophilic addition–elimination reaction is designed and synthesized. Polymer sensor exhibits “turn‐off” fluorescence quenching response upon the addition of Hg²⁺, and “turn‐on” moderate fluorescence enhancement behavior towards phenylalaninol enantiomers. Meanwhile, this kind of (S)‐BINOL‐based polymer sensor can exhibit highly selective enantioselective recognition response towards (L)‐phenylalaninol upon the addition of Hg²⁺ and the value of ef can reach as high as 5.4, which can be attributed to the formation of in situ generated radical cation arisen from oligomeric aniline moiety by Hg²⁺ induction.

     

A Fluorescent Probe for Hg2+ Based on Gold(I) Complex with An Aggregation‐Induced Emission Feature

A gold(I) complex that exhibited aggregation‐induced emission in acetonitrile‐water mixtures was designed. It showed high selectivity and sensitivity for Hg²⁺ in acetonitrile‐H₂O (1:1, V:V) solution. Dynamic light scattering measurements were conducted to verify that the addition of Hg²⁺ changed the particle size and induced fluorescence quenching.     

Water‐soluble hyperbranched polyelectrolytes with high fluorescence quantum yield: Facile synthesis and selective chemosensor for Hg2+ and Cu2+ ions

New water‐soluble hyperbranched polyfluorenes bearing carboxylate side chains have been synthesized by the simple “A2 + B2 + C3” protocol based on Suzuki coupling polymerization. The linear polyfluorene analogue LPFA was also synthesized for comparative investigation. The optical properties of the neutral precursory polymers in CHCl₃ and final carboxylic‐anionic conjugated polyelectrolytes in buffer solution were investigated. The obtained hyperbranched polyelectrolyte HPFA2 with lower content of branch unit (2%) showed excellent solubility and high fluorescence quantum yield (?_F = 89%) in aqueous solution. Fluorescence quenching of HPFA2 by different metal ions was also investigated, the polyelectrolyte showed high selectivity for Hg²⁺ and Cu²⁺ ions relative to other various metal ions in buffer solution. The Stern‐Volmer constant K_sv was determined to be 0.80 × 10⁶ M^?1 for Hg²⁺ and 3.11 × 10⁶ M^?1 for Cu²⁺, respectively, indicating the potential application of HPFA2 as a highly selective and sensitive chemosensor for Hg²⁺ and Cu²⁺ ions in aqueous solution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3431–3439, 2010     

Carboxylic‐functionalized water soluble π‐conjugated polymer: Highly selective and efficient chemosensor for mercury(II) ions

Here, we report a new carboxylic‐functionalized water soluble π‐conjugated polymer for selective detection of highly toxic Hg²⁺ in neutral pH condition. carboxylic‐functionalized thiophene containing oligophenylenevinylene was synthesized and polymerized under oxidative route to obtain water soluble polymer. Free carboxylic groups present in the π‐conjugated materials provide opportunity to use pH as external stimuli for studying secondary interaction such as hydrogen bonding and aromatic π‐stacking of the chromophores. The pH changes strongly influence on the molecular interactions in the monomer, whereas the long chain polymer was less disturbed. The polymer showed high selectivity for detecting Hg²⁺ ions compared with any other transition metal ions in water. The detection efficiency of the polymer was found almost 40 times higher than that of its monomeric unit. Stern‐Volmer constant for the Hg²⁺ ion sensing was determined through concentration dependent studies as 6.4 × 10⁵ M^?1. The carboxylic‐functionalized polymer showed reversibility in the metal‐ion detecting capabilities which was further investigated by NaCl complexation with Hg²⁺ complex. Both funneling of excitation energy to the Hg²⁺ center and also excitation energy migration through chain π‐conjugated backbone were correlated to the superior sensing characteristics of the polymer compared to its monomeric counterpart. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5144–5157, 2009     

A highly sensitive “test paper” for Hg2+ ions based on polyurethane membrane

Heavy metals have caused a lot of serious problems to human beings. A reusable, highly sensitive metal sensor based on polyurethane membrane, which can detect and remove Hg²⁺ ions, was prepared and tested in this work. A sensor with hydroxyl (?OH) group was grafted to polyurethane, and the heavy metal sensitive membrane was synthesized accordingly. Upon addition of Hg²⁺ ion solution to the as‐prepared membrane, the color change occurred instantly. Moreover, different colors appeared with different concentration of the Hg²⁺ ions, which could make the membrane be employed as a heavy metal “test paper”. In addition, the membrane sensor could be recycled after the interaction with Hg²⁺ ions by treating the used membrane with dilute ethylenediaminetetraacetic acid 2Na solution. This efficient and easily prepared membrane‐based sensor has a promising application in environmental science. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of the Counterion on Light Emission: A Displacement Strategy to Change the Emission Behaviour from Aggregation‐Caused Quenching to Aggregation‐Induced Emission and to Construct Sensitive Fluorescent Sensors for Hg2+ Detection

In this paper, a simple strategy to change the emission behaviour of luminogenic materials was developed. Tetraphenylethene (TPE)‐functionalised benzothiazolium salts with different counteranions (TPEBe?X; X=I^?, ClO₄^? and PF₆^?) were designed and synthesised. All the luminogens show weak red emission in the solution state that originates from intramolecular charge transfer from TPE to the benzothiazolium unit. Whereas aggregate formation enhances the light emission of TPEBe?ClO₄ and TPEBe?PF₆, that of TPEBe?I is quenched, thus demonstrating the phenomena of aggregation‐induced emission and aggregation‐caused quenching. TPEBe?I works as a light‐up fluorescent sensor for Hg²⁺ in aqueous solution with high sensitivity and specificity owing to the elimination of the emission quenching effect of the iodide ion by the formation of HgI₂ as well as the induction in aggregate formation by the complexation of Hg²⁺ with the S atom of the benzothiazolium unit of TPEBe?I. A solid film of TPEBe?I was prepared that can monitor the level of Hg²⁺ in aqueous solution with a detection limit of 1 μM .     

Multimodal Use of New Coumarin‐Based Fluorescent Chemosensors: Towards Highly Selective Optical Sensors for Hg2+ Probing

Despite several types of fluorescent sensing molecules have been proposed and examined to signal Hg²⁺ ion binding, the development of fluorescence‐based devices for in‐field Hg²⁺ detection and screening in environmental and industrial samples is still a challenging task. Herein, we report the synthesis and characterization of three new coumarin‐based fluorescent chemosensors featuring mixed thia/aza macrocyclic framework as receptors units, that is, ligands L1 – L3 . These probes revealed an OFF–ON selective response to the presence of Hg²⁺ ions in MeCN/H₂O 4:1 (v/v), which allowed imaging of this metal ion in Cos‐7 cells in vitro. Once included in silica core–polyethylene glycol (PEG) shell nanoparticles or supported on polyvinyl chloride (PVC)‐based polymeric membranes, ligands L1 – L3 can also selectively sense Hg²⁺ ions in pure water. In particular we have developed an optical sensing array tacking advantage of the fluorescent properties of ligand L3 and based on the computer screen photo assisted technique (CSPT). In the device ligand L3 is dispersed into PVC membranes and it quantitatively responds to Hg²⁺ ions in natural water samples.     

Synthesis of Novel 4‐((Substituted bis‐indolyl)methyl)‐benzo‐15‐crown‐5 for the Colorimetric Detection of Hg2+ Ions in an Aqueous Medium

A practical, two‐step synthesis of novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 has been reported. The strategy employed for the synthesis of the desired molecules involved Duff formylation of benzo‐15‐crown‐5 to get 4‐formyl benzo‐15‐crown‐5 followed by subsequent reactions with substituted indoles in trifluoroacetic acid to yield novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 in moderate to good yield. One of the reported novel molecule tested for the complexation behavior with various metal cations, such as Li⁺, Na⁺, K⁺, Mg²⁺ Ca²⁺, Al³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn²⁺, Ba²⁺, Hg²⁺, and Pb²⁺, showed a visual colorimetric probe for the detection of mercury cations (Hg²⁺) in an aqueous medium.     

All Solid State Chromium(III) Selective Potentiometric Sensor Based on 2‐(1‐(2‐((3‐(2‐Hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol

Highly selective all solid state electrochemical sensor based on a synthesized compound i.e. 2‐(1‐(2‐((3‐(2‐hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol (I) as an ionophore has been prepared and investigated for the selective quantification of chromium(III) ions. The effect of various plasticizers, viz. dibutyl phosphonate (DBP), dibutyl(butyl) phosphonate (DBBP), nitrophenyl octyl ether (NPOE), tris‐(2‐ethylhexyl)phosphonate (TEP), tri‐butyl phosphonate (TBP), dioctyl phthalate (DOP), dioctyl sebacate (DOS), benzyl acetate (BA) and acetophenone (AP) along with anion excluders NaTPB (sodium tetraphenyl borate) and KClTPB (potassium(tetrakis‐4‐chlorophenyl)borate was also studied. The optimum composition of the best performing membrane contained (I):KClTPB:NPOE:PVC in the ratio 15 : 3 : 40 : 42 w/w. The sensor exhibited near Nernstian slope of 20.1±0.2 mV/decade of activity in the working concentration range of 1.2×10^?7–1.0×10^?1 M, and in a pH range of 3.8–4.5. The sensor exhibited a fast response time of 10 s and could be used for about 5 months without any considerable divergence in potentials. The proposed sensor showed very good selectivity over most of the common cations including Na⁺, Li⁺, K⁺, Cu²⁺, Sr²⁺, Ni²⁺, Co²⁺, Ba²⁺, Hg²⁺, Pb²⁺, Zn²⁺, Cs⁺, Mg²⁺, Cd²⁺, Al³⁺, Fe³⁺and La³⁺. The activity of Cr(III) ions was successfully determined in the industrial waste samples by using this sensor.