Preparation of PSSS‐grafted polysulfone microfiltration membrane and its rejection and removal properties towards heavy metal ions

3‐Hydroxy‐N,N‐diethylaniline (HDEA) as a tertiary aromatic amine was introduced onto the surface of chloromethylated polysulfone (CMPSF) microfiltration membrane through modification reaction, resulting in the modified membrane PSF‐DEA. A redox surface‐initiating system (DEA/APS) was constituted by the bonded tertiary aromatic amine group DEA and ammonium persulfate (APS) in aqueous solution, and so, the free radicals formed on the membrane initiated sodium p‐styrenesulfonate (SSS) as an anionic monomer to produce graft polymerization, getting the grafting‐type composite microfiltration membrane, PSF‐g‐PSSS membrane. Subsequently, the adsorption property of PSF‐g‐PSSS membrane for three heavy metal ions, Pb²⁺, Zn²⁺, and Hg²⁺ ions, was fully examined, and the rejection performance of PSF‐g‐PSSS membrane towards the three heavy metal ions was emphatically evaluated via permeation experiments. The experimental results show that by the initiating of the surface‐initiating system of DEA/APS, the graft polymerization can smoothly be carried out under mild conditions. PSF‐g‐PSSS membrane as a functional microfiltration membrane has strong adsorption ability for heavy metal ions by right of strong electrostatic interaction (or ion exchange action) between the anionic sulfonate ions on the membrane and heavy metal ions. The order of adsorption capacity is Pb²⁺ > Zn²⁺ > Hg²⁺, and the adsorption capacity of Pb²⁺ ion gets up to 2.18 μmol/cm². As the volume of permeation solutions, in which the concentrations of the three metal ions are 0.2 mmol/L, are in a range of 50 to 70 mL, the rejection rate of PSF‐g‐PSSS membrane for the three heavy metal ions can reach a level of 95%, displaying a fine rejection and removing performance towards heavy metal ions.     

Reversible Self‐Assembly of Carboxylated Peptide‐Functionalized Gold Nanoparticles Driven by Metal‐Ion Coordination

Carboxylated peptide‐functionalized gold nanoparticles (peptide‐GNPs) self‐assemble into two‐ and three‐dimensional nanostructures in the presence of various heavy metal ions (i.e. Pb²⁺, Cd²⁺, Cu²⁺, and Zn²⁺) in aqueous solution. The assembly process is monitored by following the changes in the surface plasmon resonance (SPR) band of gold nanoparticles in a UV/Vis spectrophotometer, which shows the development of a new SPR band in the higher‐wavelength region. The extent of assembly is dependent on the amount of metal ions present in the medium and also the time of assembly. TEM analysis clearly shows formation of two‐ and three‐dimensional nanostructures. The assembly process is completely reversible by addition of alkaline ethylenediaminetetraacetic acid (EDTA) solution. The driving force for the assembly of peptide‐GNPs is mainly metal ion/carboxylate coordination. The color and spectral changes due to this assembly can be used for detection of these heavy‐metal ions in solution.     

Elucidation of Metal‐Ion Accumulation Induced by Hydrogen Bonds on Protein Surfaces by Using Porous Lysozyme Crystals Containing RhIII Ions as the Model Surfaces

Metal‐ion accumulation on protein surfaces is a crucial step in the initiation of small‐metal clusters and the formation of inorganic materials in nature. This event is expected to control the nucleation, growth, and position of the materials. There remain many unknowns, as to how proteins affect the initial process at the atomic level, although multistep assembly processes of the materials formation by both native and model systems have been clarified at the macroscopic level. Herein the cooperative effects of amino acids and hydrogen bonds promoting metal accumulation reactions are clarified by using porous hen egg white lysozyme (HEWL) crystals containing Rh^III ions, as model protein surfaces for the reactions. The experimental results reveal noteworthy implications for initiation of metal accumulation, which involve highly cooperative dynamics of amino acids and hydrogen bonds: i) Disruption of hydrogen bonds can induce conformational changes of amino‐acid residues to capture Rh^III ions. ii) Water molecules pre‐organized by hydrogen bonds can stabilize Rh^III coordination as aqua ligands. iii) Water molecules participating in hydrogen bonds with amino‐acid residues can be replaced by Rh^III ions to form polynuclear structures with the residues. iv) Rh^III aqua complexes are retained on amino‐acid residues through stabilizing hydrogen bonds even at low pH (≈2). These metal–protein interactions including hydrogen bonds may promote native metal accumulation reactions and also may be useful in the preparation of new inorganic materials that incorporate proteins.     

Fourier transform infrared spectroscopy study of the effect of pH on anion and cation adsorption onto poly(acrylo‐amidino diethylenediamine)

The role of hydrogen bonding in the chemistry of transition‐metal complexes remains a topic of intense scientific and technological interest. Poly(acrylo‐amidino diethylenediamine) was synthesized to study the effects of hydrogen bonding on complexes at different pHs. The polymer was synthesized through the coupling of diethylene triamine with polyacrylonitrile fiber in the presence of AlCl₃ · 6H₂O addition. The adsorption capacity of this polymer was 11.4 mequiv/g. The ions used for the adsorption test were CrO, PO, Cu²⁺, Ni²⁺, Fe²⁺, and Ag⁺. All experiments were confirmed with Fourier transform infrared. In the study of anion adsorption, at low pHs, only ionic bonds existed, whereas at high pHs, no bonds existed. However, in the middle pH region, both ionic bonds and hydrogen bonds formed between poly(acrylo‐amidino diethylenediamine) and the chromate ion or phosphate ion. When poly(acrylo‐amidino diethylenediamine) and metal ions (Cu²⁺, Ni²⁺, Fe²⁺, and Ag⁺) formed complexes, a hydrogen‐bonding effect was not observed with Fourier transform infrared. The quantity of metal ions adsorbed onto poly(acrylo‐amidino diethylenediamine) followed the order Ag⁺ > Cu²⁺ > Fe²⁺ > Ni²⁺. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2010–2018, 2004     

Supramolecular Structures with the 2‐Propyl‐4,5‐dicarboxy‐1H‐imidazole Ligand: Hydrothermal Synthesis,Structures, and Photoluminescence

Self‐assembly of the rigid organic ligand 2‐propyl‐4,5‐dicarboxy‐1H‐imidazole ( L ) with different metal ions (Zn²⁺, Ni²⁺, Cu²⁺, Cd²⁺) led to four new complexes, namely, [M( L )(phen)] [M = Zn ( 1 ); Ni ( 2 ); Cd ( 3 )] and [Cu( L )( 4 )] (phen = 1,10‐phenanthroline). Their structures were determined by single‐crystal X‐ray diffraction analyses, and they were further characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. Whereas compounds 1 , 2 , and 3 are discrete units, hydrogen‐bonding interactions play a vital role in these complexes. Compounds 1 and 2 form one‐dimensional (1D) and two‐dimensional (2D) structures through hydrogen‐bondinginteractions with helical character. In 1 , the hydrogen bonds (O–H ··· O) alternately bridge the M^II cations of the discrete units to form a one‐dimensional (1D) infinite helical chain. Complex 2 forms a 2D helical layer through parallel hydrogen bonds (N/O–H ··· O/N) between two adjacent helical chains. In 3 , the hydrogen bonds (N–H ··· O) connect adjacent discrete units into a ten‐membered ring with extension into a one‐dimensional double‐chain supramolecular structure. Complex 4 is a two‐dimensional gridlike (4,4) topological layer which is extended to a 3D network by hydrogen bonding. The solid‐state fluorescence spectrum of complex 3 was determined.     

Self‐Assembled Cyclic Structures from Copper(II) Peptoids

Metal–ligand coordination is a key interaction in the self‐assembly of both biopolymers and synthetic oligomers. Although the binding of metal ions to synthetic proteins and peptides is known to yield high‐order structures, the self‐assembly of peptidomimetic molecules upon metal binding is still challenging. Herein we explore the self‐assembly of three peptoid trimers bearing a bipyridine ligand at their C‐terminus, a benzyl group at their N‐terminus, and a polar group (N‐ethyl‐R) in the middle position (R=OH, OCH₃, or NH₂) upon Cu²⁺ coordination. X‐ray diffraction analysis revealed unique, highly symmetric, dinuclear cyclic structure or aqua‐bridged dinuclear double‐stranded peptoid helicates, formed by the self‐assembly of two peptoid molecules with two Cu²⁺ ions. Only the macrocycle with the highest number of intermolecular hydrogen bonds is stable in solution, while the other two disassemble to their corresponding monometallic complexes.     

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.     

Tough and self‐recoverable hydrogels crosslinked by triblock copolymer micelles and Fe3+ coordination

Tough hydrogels have great potentials in soft robotics, artificial muscles, tissue replacement, and so on. Here we introduce novel tough hydrogels crosslinked by triblock copolymer (F127DA) micelles and metal coordination. The gels showed outstanding tensile strength (∼1–11 MPa), toughness (∼4–32 MJ m⁻³), and excellent self‐recovery properties (∼56.8–87.2% toughness recovery in 9 min at room temperature). The mechanical and self‐recovery properties could be manipulated by varying contents of micelles and/or COO⁻ groups. Dynamic mechanical analysis of the hydrogels revealed apparent activation energy and relaxations for both physical interactions. In situ small‐angle X‐ray scattering measurements on hydrogels upon stretching revealed micelle deformations. XPS measurements on hydrogels before and after stretching revealed significant changes in the binding energy of Fe³⁺ ions in the gels, suggesting the rupture of coordination bonds. The experimental results strongly suggest a synergistic effect from the micelle‐crosslinking and Fe³⁺–COO⁻ coordination on the strength, toughness, and self‐recovery of the hydrogels. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 865–876     

Cellulose/chitosan composites prepared in ethylene diamine/potassium thiocyanate for adsorption of heavy metal ions

Cellulose/chitosan composites were successfully prepared in a new and basic-based solvent system, ethylene diamine/potassium thiocyanate (EDA/KSCN), by dissolving cellulose and chitosan in 70/30 (w/w) EDA/KSCN at ?19 °C, and then coagulating in methanol. Wide angle X-ray diffraction studies revealed that the EDA/KSCN solvent system is capable of disrupting the hydrogen bonds in both cellulose and chitosan and increase the amorphous regions. Stability tests proved that the composites are stable in acidic aqueous solution due to the hydrogen bonds formed between cellulose and chitosan. This is the first time to dissolve chitosan in a basic-based solvent system and prepare cellulose/chitosan composites in a straightforward way. The adsorption of heavy metal ions (Cu²⁺, Cd²⁺, and Pb²⁺) onto the cellulose/chitosan composites was investigated. The adsorption capacity is highly dependent on pH and the maximum metal uptake was obtained at pH 5.0. Increasing initial metal concentration enhanced the diffusion of metal ions to the composite surface and therefore the metal removal efficiency. Higher percentage of chitosan in the composites also led to higher metal adsorption. The results indicated that the prepared cellulose/chitosan (1:1) composite can adsorb 0.53 mmol/g Cu²⁺, 0.28 mmol/g Cd²⁺ and 0.16 mmol/g Pb²⁺ ions at pH 5.0. The Freundlich model and the pseudo-second-order model were in good agreement with the adsorption isotherms and kinetics, respectively. X-ray photoelectron spectroscopy studies indicated that the binding of heavy metal ions is attributed to the nitrogen atoms of amino groups in chitosan. The composites can be reused for metal removal.     

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.     

Ionic Dependence of Gelatin Hydrogel Architecture Explored Using Small and Very Small Angle Neutron Scattering Technique

The hierarchical structure of gelatin hydrogels mimics a natural extracellular matrix and provides an optimized microenvironment for the growth of 3D structured tissue analogs. In the presence of metal ions, gelatin hydrogels exhibit various mechanical properties that are correlated with the molecular interactions and the hierarchical structure. The structure and structural response of gelatin hydrogels to variation of gelatin concentration, pH, or addition of metal ions are explored by small and very small angle neutron scattering over broad length scales. The measurements of the hydrogels reveal the existence of a two‐level structure of colloid‐like large clusters and a 3D cage‐like gel network. In the presence of Fe³⁺ ions the hydrogels show a highly dense and stiff network, while Ca²⁺ ions have an opposite effect. The results provide important structural insight for improvement of the design of gelatin based hydrogels and are therefore suitable for various applications.     

4‐(3‐Azaniumylpropyl)morpholin‐4‐ium chloride hydrogen oxalate: an unusual example of a dication with different counter‐anions

The mixed organic–inorganic title salt, C₇H₁₈N₂O²⁺·C₂HO₄⁻·Cl⁻, forms an assembly of ionic components which are stabilized through a series of hydrogen bonds and charge‐assisted intermolecular interactions. The title assembly crystallizes in the monoclinic C2/c space group with Z = 8. The asymmetric unit consists of a 4‐(3‐azaniumylpropyl)morpholin‐4‐ium dication, a hydrogen oxalate counter‐anion and an inorganic chloride counter‐anion. The organic cations and anions are connected through a network of N—H...O, O—H...O and C—H...O hydrogen bonds, forming several intermolecular rings that can be described by the graph‐set notations R₃³(13), R₂¹(5), R₁²(5), R₂¹(6), R₂³(6), R₂²(8) and R₃³(9). The 4‐(3‐azaniumylpropyl)morpholin‐4‐ium dications are interconnected through N—H...O hydrogen bonds, forming C(9) chains that run diagonally along the ab face. Furthermore, the hydrogen oxalate anions are interconnected via O—H...O hydrogen bonds, forming head‐to‐tail C(5) chains along the crystallographic b axis. The two types of chains are linked through additional N—H...O and O—H...O hydrogen bonds, and the hydrogen oxalate chains are sandwiched by the 4‐(3‐azaniumylpropyl)morpholin‐4‐ium chains, forming organic layers that are separated by the chloride anions. Finally, the layered three‐dimensional structure is stabilized via intermolecular N—H...Cl and C—H...Cl interactions.     

Coordination‐driven self‐assembly of Cp*Rh‐based rectangles in novel families of hetero‐bimetallic metal–organic frameworks

The crystal and molecular structures of a series of structurally related 1,2,3‐triazole‐4,5‐dicarboxylate (LHtzdc = 1,2,3‐triazole‐4,5‐dicarboxylate) ligands for second metal ions were established via single‐crystal X‐ray structural analysis. [Cu (en)]²⁺ (en = ethylenediamine) was selected as a second metal ion, the two spare sites of the O atom from LHtzdc are coordinated to a single [Cu (en)]²⁺, and the [Cu (en)]²⁺ metal centres act as two outer pockets, which is an effective and innovative method of controlling the assembly of heterometallic cages.     

Adsorption Properties of Hydrated Cr3+ Ions on Schiff‐base Covalent Organic Frameworks: A DFT Study

Considering the superior physiochemical property, increasing efforts have been devoted to exploiting the covalent organic frameworks (COFs) materials on the environmental remediation of heavy metal ions. Water pollution caused by Cr³⁺ metal ions is of special concern for scientists and engineers. Notwithstanding all the former efforts made, it is surprising that very little is known about the interaction mechanisms between the hydrated Cr³⁺ metal ions and COF materials. In present context, density functional theory (DFT) method is used to elucidate geometric and electronic properties with the purpose of putting into theoretical perspective the application values and interaction mechanisms for COF materials on Cr³⁺ capture. The results showed that all the five selected Schiff‐base COFs materials displayed good adsorption performance on Cr³⁺ removal while the phenazine‐linked and imine‐COFs possessed the most favorable adsorption capacity due to the optimal chemical units and frameworks. The hydration effect was found to play a two‐side role in the adsorption process and interaction mechanisms, involving coordination, hydrogen bonds, as well as weak non‐covalent interactions, have been illuminated to explain the observed different adsorption behaviors. This study provides a general guidance for the design and selection of efficient COF materials as high‐capacity Cr³⁺ adsorbents.     

L‐lysine and EDTA polymer mimics as resins for the quantitative and reversible removal of heavy metal ion water pollutants

Traditional precipitation methods for inorganic micropollutant removal from waters are increasingly being replaced by sorption methods based on both natural and synthetic materials. In this context, two novel effective heavy metal ions absorbers are presented. These resins, LYMA and LMT85, were crosslinked poly(amidoamine)s carrying amine and carboxyl groups in their repeating units. In particular, the LYMA‐repeating unit contains one carboxyl and two amine groups and is a mimic of L ‐lysine, whereas LMT85 contains two amine and five carboxyl groups and is a mimic of EDTA. Both resins were prepared at moderate cost by simple eco‐friendly procedures. The heavy metal ion set adopted as benchmark was Cu²⁺, Cd²⁺, Pb²⁺, Zn²⁺, Ni²⁺, and Co²⁺. LYMA proved selective for Cu²⁺ and Ni²⁺, the other ions tested being negligibly absorbed, whereas LMT85 proved capable of rapidly and quantitatively absorbing all the ions tested either singly or in mixed solution. The absorption process was reversible, and the resins were easily regenerated by acidification. The absorption of several metal ions imparted intense coloring to the resins, a feature possibly exploitable for analytical purposes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Copper and Nickel Removal from Aqueous Solutions Using New Chelating Poly[Acrylamide/N‐vinyl pyrrolidone/3‐(2‐hydroxyethyl carbamoyl)acrylic acid] Hydrogels

New poly[Acrylamide/N‐vinyl pyrrolidone/3‐(2‐hydroxyethyl carbamoyl)acrylic acid], poly [AAm/NVP/HECA], chelating hydrogels with different composition of HECA monomer have been prepared via free radical solution polymerization using N,N‐methylene bisacrylamide as a crosslinker. The hydrogels obtained were loaded with metal ions and characterized by FT‐IR spectroscopy, Scanning Electron Microscope (SEM) and Thermogravimatric analysis (TGA). The removal of Cu²⁺ and Ni²⁺ from aqueous solutions by the hydrogel was examined by a batch equilibrium method. The influence of treatment time, pH, initial concentration of the metal ions and HECA content in the feed compositions on the amount of adsorbed metal ions was studied. Swelling of the hydrogel was also carried out in distilled water and metal ion solutions. The removal of the metal ions followed the following order: Ni²⁺>Cu²⁺. The amount of metal ions removed increased with increasing HECA content in the feed composition, treatment time, pH of the medium and initial concentration of metal ions. The desorption of metal ions were carried out using 1 N HCl and 0.5 N H₂SO₄. The poly[AAm/NVP/HECA] hydrogels could be used many times without significantly decreasing their adsorption capacity.     

Detection of Trace Heavy Metal Ions Using Carbon Nanotube‐ Modified Electrodes

A sensitive voltammetric method for detection of trace heavy metal ions using chemically modified carbon nanotubes (CNTs) electrode surfaces is described. The CNTs were covalently modified with cysteine prior to casting on electrode surfaces. Cysteine is an amino acid with high affinities towards some heavy metals. In this assay, heavy metals ions accumulated on the cysteine‐modified CNT electrode surfaces prior to being subjected to differential pulse anodic stripping voltammetry analysis. The resulting peak currents were linearly related to the concentrations of the metal ions. The method was optimized with respect to accumulation time, reduction time and reduction potential. The detection limits were found to be 1 ppb and 15 ppb for Pb²⁺ and Cu²⁺ respectively. The technique was used for the detection of Pb²⁺ and Cu²⁺ in spiked lake water. The average recoveries of Pb²⁺ and Cu²⁺ were 96.2% and 94.5% with relative standard deviations of 8.43% and 7.53% respectively. The potential for simultaneous detection of heavy metal ions by the modified CNTs was also demonstrated.     

Competitive heavy metal removal by poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid‐co‐itaconic acid)

The competitive removal of Pb²⁺, Cu²⁺, and Cd²⁺ ions from aqueous solutions by the copolymer of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and itaconic acid (IA), P(AMPS‐co‐IA), was investigated. Homopolymer of AMPS (PAMPS) was also used to remove these ions from their aqueous solution. In the preparation of AMPS–IA copolymer, the molar percentages of AMPS and IA were 80 and 20, respectively. In order to observe the changes in the structures of polymers due to metal adsorption, FTIR spectra by attenuated total reflectancetechnique and scanning electron microscopy (SEM) pictures of the polymers were taken both before and after adsorption experiments. Total metal ion removal capacities of PAMPS and P(AMPS‐co‐IA) were 1.685 and 1.722 mmol Me²⁺/g_polymer, respectively. Experimental data were evaluated to determine the kinetic characteristics of the adsorption process. Competitive adsorption of Pb²⁺, Cu²⁺, and Cd²⁺ ions onto both PAMPS and P(AMPS‐co‐IA) was found to fit pseudo‐second‐order type kinetics. In addition, the removal orders in the competitive adsorption of these metal ions onto PAMPS and P(AMPS‐co‐IA) were found to be Cd²⁺ > Pb²⁺ > Cu²⁺ and Pb²⁺ > Cd²⁺ > Cu²⁺, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

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.