BODIPY Immobilized MCM-41 Based Multianalyte Sensor: Application in Detection and Removal of Trivalent (Al3+, Cr3+) and Divalent (Cu2+, Hg2+) Metal Ions in Aqueous Media

In the present study, a novel p-phenylcarboxylic acid BODIPY ( L ) immobilized MCM-41 based solid chemosensor material L-propylsilyl@MCM-41 ( MS4 ) was developed to detect multiple metal ions in a pure aqueous medium. The synthesized solid chemosensor material MS4 shows high sensitivity and removal ability towards trivalent (Al³⁺, Cr³⁺) and divalent (Cu²⁺, Hg²⁺) metal ions. The emission intensity of MS4 enhanced multifold selectively in the presence of trivalent (Al³⁺, Cr³⁺) metal ions and shows quenching in the presence of divalent (Cu²⁺, Hg²⁺) metal ions. The limit of detection was calculated to be in the nanomolar range with Al³⁺, Cr³⁺, Cu²⁺_, and Hg²⁺ metal ions in the aqueous medium. The spectroscopic and analytical results suggest that MS4 selectively binds with Al³⁺ and Cr³⁺ through −NH functionality and with Hg²⁺ and Cu²⁺ through −COOH functionality of p-phenylcarboxylic acid BODIPY ( L ). Further, MS4 selectively removes Al³⁺, Cr³⁺, Cu²⁺, and Hg²⁺ metal ions from the aqueous media with removal efficiency of 97.28 %, 96.34 %, 87.19 %, and 95.63 %, respectively. No noticeable change in the concentration was observed for other metal ions. The recycling potential of MS4 was evaluated using EDTA for up to seven cycles with no significant reduction in sensing capability.     

Rhodamine-Appended Bipyridine: XOR and OR Logic Operations Integrated in an Example of Controlled Metal Migration

A new bipyridyl derivative 1 bearing rhodamine B as visible fluorophore was designed, synthesized and characterized as a fluorescent and colorimetric sensor for metal ions. Interaction with Cu²⁺, Zn²⁺, Cd²⁺, Hg⁺, and Hg²⁺ ions was followed by UV/Vis and emission spectroscopy. Upon addition of these metal ions, different colorimetric and fluorescent responses were observed. “Off-on-off” (Cu²⁺, Zn²⁺, and Hg²⁺) and “off-on” (Hg⁺ and Cd²⁺) systems were obtained. Probe 1 was explored to mimic XOR and OR logic operations for the simultaneous detection of Hg⁺–Cu²⁺ and Hg⁺–Zn²⁺ pairs, respectively. DFT calculations were also performed to gain insight into the lowest-energy gas-phase conformation of free receptor 1 as well as the atomistic details of the coordination modes of the various metal ions.     

Silole‐Infiltrated Photonic Crystal Films as Effective Fluorescence Sensor for Fe3+ and Hg2+

We develop a highly effective silole‐infiltrated photonic crystal (PC) film fluorescence sensor with high sensitivity, good selectivity and excellent reproducibility for Fe³⁺ and Hg²⁺ ions. Hexaphenylsilole (HPS) infiltrated PCs show amplified fluorescence due to the slow photon effect of PC because the emission wavelength of HPS is at the blue band edge of the selected PC’s stopband. The fluorescence can be quenched significantly by Fe³⁺/Hg²⁺ ions owing to electron transfer between HPS and metal ions. The amplified fluorescence enhances the sensitivity of detection, with a detection limit of 5 nM for Fe³⁺/Hg²⁺ ions. The sensor is negligibly responsive to other metal ions and can easily be reproduced by rinsing with pure water due to the special surface wettability of PC. As a result, a highly effective Fe³⁺/Hg²⁺ ions sensor based on HPS‐infiltrated PC film has been achieved, which will be important for effective and practical detection of heavy metal ions.     

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.     

Hg-selective fluoroionophoric behavior of pyrene appended diazatetrathia-crown ether

Bis(pyrene) derivative of diazatetrathia-crown ether has been prepared and its Hg²⁺-selective fluoroionophoric properties were investigated. The compound showed a pronounced Hg²⁺-selectivity and other metal ions except for Cu²⁺ showed almost no discernible responses. The Hg²⁺-selectivity of the compound was also confirmed by the competitive experiments performed in the presence of physiologically important metal ions and the detection limit was found to be 1.6 × 10⁻⁶ M. The prominent selective and efficient fluorescence quenching behavior could be utilized as a new chemosensing system for the analysis of toxic Hg²⁺ ions in aqueous environment.     

A Simple and Highly Sensitive Electrochemically Reduced p‐Nitrobenzoic Acid Film Modified Sensor for Determination of Mercury

Herein, a simple electrochemical sensor was fabricated for sensing Hg²⁺ ions by using electrochemically reduced p‐nitrobenzoic acid molecules modified (ERpNBA) glassy carbon electrode (GCE). The modified electrode was applied for the determination of Hg²⁺ ions by using differential pulse anodic stripping voltammetry (DPASV). Experimental parameters such as concentration of p‐nitrobenzoic acid used for electrode modification, pH, accumulation time and deposition potential used for the determination of Hg²⁺ ions were optimized. The strong interaction between the Hg²⁺ ions and the lone pair of electrons on the nitrogen atoms of ERpNBA molecules leads to highly selective adsorption of Hg²⁺ ions on the modified electrode. Under the optimum experimental conditions, the sensor showed higher sensitivity and very low detection limit for Hg²⁺ ions than other metal ions such as Cd²⁺, Pb²⁺ and Zn²⁺ ions. The LOD for Hg²⁺ ions was 240 pM which is below the guideline value given by the World Health Organization and the earlier reports.     

Azo 8-hydroxyquinoline benzoate as selective chromogenic chemosensor for Hg and Cu

Azo 8-hydroxyquinoline benzoate (2) was synthesized and studied to detect metal ions. Distinct color change was found for compound 2 in the presence of transition metal ions Hg²⁺ or Cu²⁺ in CH₃CN, respectively, which makes it possible for distinguishing Hg²⁺ and Cu²⁺ from other metal ions by the ‘naked eye’.     

Hg- and Cu-selective fluoroionophoric behaviors of a dioxocyclam derivative bearing anthrylacetamide moieties

New dioxocyclam derivatives bearing two anthracene fluorophores were prepared, and their fluoroionophoric properties toward transition metal ions were investigated. Chemosensor 2 having anthrylacetamide moieties exhibited pronounced Hg²⁺- and Cu²⁺-selective fluoroionophoric properties in aqueous acetonitrile solution over other representative transition metal ions, as well as alkali and alkaline earth metal ions. Chemosensor 2 also exhibited Hg²⁺ and Cu²⁺ selectivity under competitive conditions in the presence of physiologically and environmentally important metal ions. The detection limits for the sensing of Hg²⁺ and Cu²⁺ ions were 7.8 × 10⁻⁶ and 1.5 × 10⁻⁶ M, respectively, in aqueous 95% acetonitrile solution.     

Selective detection of phosphaphenanthrenecontaining luminophors with aggregation-induced emission enhancement to transition metal ions

Transition metal ions (Pb²⁺, Zn²⁺, Cd²⁺, Co²⁺, Mn²⁺, Cu²⁺, Ni²⁺, Hg²⁺, Ag⁺, Fe³⁺) in water are used to quench emission of 2-(6-oxido-6H-dibenz 〈c,e〉 〈1,2〉 oxaphosphorin-6-yl)-1,4-phenylene-bis(p-pentyloxylbenzoate)s (MD5) with aggregation-induced emission enhancement (AIEE) in water-acetonitrile (AN) mixture (80:20 by volume). Among all metal ions, Fe³⁺ exhibits the highest quenching efficiency on AIEE of MD5 even when the concentration of Fe³⁺ is lower than 1×10⁻⁶ mol/L. The quenching efficiency of Hg²⁺ is lower than that of Fe³⁺ at the same concentration, though MD5 is used to detect Hg²⁺ efficiently, too. To other metal ions, low quenching efficiency has few relations with a wider concentration range. The UV absorbance spectra show only red shift of absorbance wavelength in the presence of Hg²⁺ and Fe³⁺, which indicates a salt-induced Jaggregation. SEM photos reveal larger aggregation and morphological change of nanoparticles of MD5 in water containing Hg²⁺ and Fe³⁺, which reduce the surface area of MD5 emission for further aggregation. The selective quenching effect of transition metal ions to emission of MD5 has a potential application in chemical sensors of some metal ions.     

Molecular Assembly Directed by Metal–Aromatic Interactions: Control of the Aggregation and Photophysical Properties of Zn–Salen Complexes by Aromatic Mercuration

There is widespread interest in non‐covalent bonding and weak interactions, such as electrostatic interactions, hydrogen bonding, solvophobic/hydrophobic interactions, metal–metal interactions, and π–π stacking, to tune the molecular assembly of planar π‐conjugated organic and inorganic molecules. Inspired by the roles of metal–aromatic interaction in biological systems, such as in ion channels and metalloproteins, herein, we report the first example of the use of Hg²⁺–aromatic interactions to selectively control the assembly and disassembly of zinc–salen complexes in aqueous media; moreover, this process exhibited significant “turn on” fluorescent properties. UV/Vis and fluorescence spectroscopic analysis of the titration of Hg²⁺ ions versus complex ZnL¹ revealed that the higher binding affinity of Hg²⁺ ions (compared to 13 other metal ions) was ascribed to specific interactions between the Hg²⁺ ions and the phenyl rings of ZnL¹ ; this result was also confirmed by ¹H NMR spectroscopy and HRMS (ESI). Further evidence for this type of interaction was obtained from the reaction of small‐molecule analogue L¹ with Hg²⁺ ions, which demonstrates the proximity of the N‐alkyl group to the aromatic protons during Hg²⁺‐ion binding, which led to the consequential H/D exchange reaction with D₂O. DFT modeling of such interactions between the Hg²⁺ ions and the phenyl rings afforded calculated distances between the C and Hg atoms (2.29 Å) that were indicative of C? Hg bond‐formation, under the direction of the N atom of the morpholine ring. The unusual coordination of Hg²⁺ ions to the phenyl ring of the metallosalen complexes not only strengthened the binding ability but also increased the steric effect to promote the disassembly of ZnL¹ in aqueous media.     

A new BODIPY-based fluorescent “turn-on” probe for highly selective and rapid detection of mercury ions

A new fluorescent sensor based on the BODIPY fluorophore and the carboxyl-thiol metal bonding receptor for Hg²⁺ was designed and synthesized. The sensor is highly selective for Hg²⁺ (about 630-fold fluorescence enhancement) over relevant competing metal ions, sensitive to ppb levels of Hg²⁺ (with detection limit of 5.7?nM), and fast response toward Hg²⁺ (within 30?s) in aqueous solution.     

Fluorescence turn-on chemodosimeter for rapid detection of mercury (II) ions in aqueous solution and blood from mice with toxicosis

The heavy metal mercury (Hg) is a threat to the health of people and wildlife in many environments. Among various chemical forms, Hg²⁺ salts are usually more toxic than their counterparts because of their greater solubility in water; thus, they are more readily absorbed from the gastrointestinal tract into circulation. Therefore, new chemical receptors for detecting Hg²⁺ ions in circulation are needed. In this study, we developed a rhodamine-based turn-on fluorescence probe to monitor Hg²⁺ in aqueous solution and in blood of mice with toxicosis. The chemodosimeter responds to Hg²⁺ ions stoichiometrically, rapidly, and irreversibly at room temperature as a result of a chemical reaction that produces strongly fluorescent oxadiazole. The new fluorescent probe shows good fluorescence response, with high sensitivity and selectivity, toward Hg²⁺ ions in aqueous solution and in blood from mice with toxicosis and facilitates the naked-eye detection of Hg²⁺ ions.     

Reaction-based Hg signaling by excimer–monomer switching of a bis-pyrene dithioacetal

A novel reaction-based probe for fluorescence signaling of Hg²⁺ ions was developed. Selective Hg²⁺-induced cleavage of a dithioacetal resulting in switching from pyrene excimer to monomer emission was used for the signaling. Changes in excimer and monomer emissions of pyrene were readily employed for ratiometric signaling of Hg²⁺ ions in aqueous acetonitrile. Selective signaling of Hg²⁺ ions over other common metal ions was observed with a detection limit of 9.8 × 10⁻⁷ M.     

Spectrofluorometric Determination of Mercury and Lead by Colloidal CdS Nanomaterial

Heavy metal ions such as Hg and Pb are hazardous due to very high toxicity, mobility, and ability to accumulate through the food chain or atmosphere in the environment system. Therefore, ultrasensitive determination of mercury and lead is important to provide an evaluation index of ions in aqueous environment. This paper describes the investigation of surface modified quantum dots (QDs) as a sensing receptor for Hg²⁺ and Pb²⁺ ion detection by optical approach. Water-soluble L-cysteine-capped CdS QDs have been synthesized in aqueous medium. These functionalized nanoparticles were used as a fluorescence sensor for Hg²⁺ and Pb²⁺ ions, involved in the fluorescence quenching. The effect of foreign ions on the intensity of CdS QDs showed a low interference response toward other metal ions except Cu²⁺ and Fe²⁺ ions. The limit of detection (LOD) of this system is found to be 1.0 and 3.0 nM for Hg²⁺ and Pb²⁺ ions, respectively.     

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。     

Dimethylcyclam based fluoroionophore having Hg- and Cd-selective signaling behaviors

Diametrically disubstituted bis(anthrylmethyl) derivative of 1,8-dimethylcyclam exhibited pronounced Hg²⁺- and Cd²⁺-selective fluorogenic behaviors in aqueous acetonitrile solution. A distinctive OFF-ON type signaling was observed for Hg²⁺ and Cd²⁺ ions in aqueous acetonitrile (CH₃CN-H₂O = 90:10, v/v) solution, while a selective ON-OFF type switching behavior toward Hg²⁺ ions was observed in solution having higher water content (CH₃CN-H₂O = 50:50, v/v). The detection limit for the analysis of Hg²⁺ ions in 50% aqueous acetonitrile was found to be 3.8 × 10⁻⁶ M. The selective OR logic gate behavior of the prepared compound toward two toxic heavy metal ions of Hg²⁺ and Cd²⁺ ions in CH₃CN-H₂O (90:10, v/v) suggests the possibility as a new chemosensing device for the two important target metal ions.     

Highly Sensitive Electrochemical Bioassay for Hg(II) Detection Based on Plasma-Polymerized Propargylamine and Three-Dimensional Reduced Graphene Oxide Nanocomposite

In this study, a nanocomposite consisting of three-dimensional reduced graphene oxide (3D-rGO) and plasma-polymerized propargylamine (3D-rGO@PpPG) was prepared and used as a highly sensitive and selective DNA sensor for detecting Hg²⁺. Given the high density of amino groups in the resultant 3D-rGO@PpPG nanocomposite, thymine-rich and Hg²⁺-targeted DNA was preferentially immobilized on the fabricated sensor surface via the strong electrostatic interaction between DNA strands and the amino-functionalized nanocomposites, followed by detecting Hg²⁺ through T–Hg²⁺–T coordination chemistry between DNA and Hg²⁺. The results of electrochemical measurements revealed that the anchored amount of DNA strands anchored on the 3D-rGO@PpPG nanofilm surface affects the determination of Hg²⁺ in aqueous solution. It showed high sensitivity and selectivity toward Hg²⁺ within concentrations ranging from 0.1 to 200 nM and displayed a low detection limit of 0.02 nM. The new strategy proposed also provides high selectivity of Hg²⁺ against other interfering metal ions, good stability, and repeatability. The excellent applicability of the developed sensor confirms the potential use of plasma-modified nanofilms for the detection of heavy metal ions in real environmental samples and water.     

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.     

New acridine derivatives bearing immobilized azacrown or azathiacrown ligand as fluorescent chemosensors for Hg and Cd

Two new acridine derivatives bearing azacrown or azathiacrown ligand were synthesized as fluorescent chemosensors for Hg²⁺ and Cd²⁺ in aqueous solution. Compounds 1 and 2 displayed selective CHEF (chelation enhanced fluorescence) effects with Hg²⁺ or Cd²⁺ among the metal ions examined. The practical use of these probes was demonstrated by their applications to the detection of Hg²⁺ and Cd²⁺ ions in mammalian cells.     

2-Aminopyridine derivative as fluorescence ‘On–Off’ molecular switch for selective detection of Fe3+/Hg2+

2-Amino-6-methyl-4-phenyl-nicotinonitrile 1, a 2-aminopyridine-based fluorescent compound, was found to be a fluorescent chemosensor for the detection of Fe³⁺ and Hg²⁺ ions over a number of other metal ions. Compound 1 was synthesized in one step using a multicomponent reaction, and characterized using common spectroscopic tools. During Fe³⁺/Hg²⁺ sensing the compound 1 followed a ‘switch-off’ mechanism. Further, compound 1 could sense Fe³⁺ over Hg²⁺ by its distinct absorption and fluorescence quenching behaviors. 1:1 complex formation of 1 with Fe³⁺ and Hg²⁺ was clearly understood from Job’s plot. The present work brings additional evidence on the importance of multicomponent reactions which could lead to the development of fluorescence chemosensor in one step for the selective detection of biologically important metal ions.