Bio-inspired colorimetric detection of Hg<Superscript>2+</Superscript> and Pb<Superscript>2+</Superscript> heavy metal ions using Au nanoparticles

Heavy metal ions are highly toxic species which can cause long-term damage to biological systems. These species are known to disrupt biological events at the cellular level, cause significant oxidative damage, and are carcinogens. The production of simple, in-field detection methods that are highly sensitive for these cations is highly desirable in response to global pollution. In that regard, bio-inspired colorimetric sensing systems have been developed to detect Hg²⁺ and Pb²⁺, and other cations, down to nmol L⁻¹ concentrations. The benefits of these systems, which are reviewed herein, include cost-effective production, facile usage, and a visual color change for the detection method. Such advantages are significant positive steps for heavy metal ion detection, especially in regions where sophisticated laboratory studies are prohibited. Figure Biological-based colorimetric detection of heavy metal cations. The materials on the left are independent Au nanoparticles in solution, functionalized with heavy metal binding biomolecules, which, upon metal addition, aggregate to evolve a detectable solution color change.

Thermodynamics of resolvation of Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>, Cd<Superscript>2+</Superscript>, and Cu<Superscript>2+</Superscript> ions in aqueous-ethanol mixtures on the basis of volta potential difference method

The volta potential difference method at 298.15 K was used to determine the real primary medium effect for magnesium, calcium, cadmium, and copper ions, and also the real Gibbs transfer energy of these ions from water into a mixed water ethanol (EtOH) solution. The surface potential value at the nonaqueous solution/gas phase interface $ \Delta \chi _{H_2 O}^{EtOH} $ \Delta \chi _{H_2 O}^{EtOH} was obtained. With account for this value, chemical thermodynamic characteristics of the studied ions in the water-ethanol solvent were calculated and the effect of composition and nature of the mixed solvent on the values obtained was analyzed. The dependence of variation in the thermodynamic characteristics of cation resolvation was established on their crystallographic radius that corresponds to the following sequence: Ca²⁺ < Cd²⁺ < Cu²⁺ < Mg²⁺.     

Effect of temperature on the sorption behavior of sodium potassium fluorophlogopite with respect to the heavy metal ions Cd<Superscript>2+</Superscript>, Hg<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript>

The effect of temperature on the sorption behavior of a synthesized gel structurally close to the fluorine mica mineral, sodium potassium fluorophologopite, was studied for the heavy metal ions Cd²⁺, Hg²⁺, and Pb²⁺. The synthesized gel was characterized by X-ray powder pattern, energy dispersive spectrometry, infrared spectroscopy, and thermogravimetric analysis and was found to have the composition Na_0.5K_0.5Mg(AlSi₃O₁₀)F₂·6H₂O. The effect of temperature on sorption was studied with respect to varying concentrations of metal ions. The overall sorption capacity of the synthesized gel was found to depend on the number of ion active groups per unit weight of the material. The data were expressed in terms of distribution coefficients (K _d). Sorption data followed Freundlich adsorption isotherms. Studies showed that sorption decreased as the concentration of metal ions increased and increased as the temperature grew, which was evidence that the process was endothermic. The text was submitted by the authors in English.     

The standard thermodynamic characteristics of resolvation of the K<Superscript>+</Superscript>, Ca<Superscript>2+</Superscript>, Cd<Superscript>2+</Superscript>, and Br<Superscript>−</Superscript> ions in water-acetone mixtures

The standard real and chemical thermodynamic characteristics of transfer of the K⁺, Ca²⁺, Cd²⁺, and Br^? ions from water into water-acetone solvents of various compositions were analyzed to study the rules governing the solvation of these ions in mixed solvents and its special features. All calculations were performed within the framework of the vertical jet method at 298.15 K. The energy of resolvation as a function of ion charges and crystallographic radii was found to increase in the series K⁺ < Ca²⁺ < Cd²⁺ < Al³⁺     

Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

Thermal behavior of Cd<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> phenyl-vinyl-phosphonates under non-isothermal condition

The thermal behavior of Cd²⁺ and Co²⁺ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation of the organic radical with formation of the pyrophosphoric anion. The kinetic analysis of the TG non-isothermal data was performed by the isoconversional methods suggested by Friedman and Flynn, Wall and Ozawa, as well as by the non-parametric (Sempere-Nomen) method. All processes put in evidence in TG curves exhibit strong changes of the activation energy values with the conversion degree, which mean that these processes are complex ones. Assuming that each of these processes consists in two steps, the application of non-parametric method leads to average values of the activation energy close to the average values of this parameter obtained by isoconversional methods.     

Colorimetric detection of Fe3+ ions using pyrophosphate functionalized gold nanoparticles

A sensitive, selective colorimetric Fe(3+) detection method has been developed by using pyrophosphate functionalized gold nanoparticles (P(2)O(7)(4-)-AuNPs). Gold nanoparticles were prepared by reducing HAuCl(4) with sodium borohydride, in the presence of Na(4)P(2)O(7). IR spectra suggested that pyrophosphates were capped on the surface of the gold nanoparticles. Aggregation of P(2)O(7)(4-)-AuNPs was induced immediately in the presence of Fe(3+) ions, yielding a color change from pink to violet. This Fe(3+)-induced aggregation of P(2)O(7)(4-)-AuNPs was monitored using first the naked eye and then UV-vis spectroscopy with a detection limit of 5.6 μM. The P(2)O(7)(4-)-AuNPs bound by Fe(3+) showed excellent selectivity compared to other metal ions (Ca(2+), Cd(2+), Co(2+), Fe(2+), Hg(2+), K(+), Mg(2+), Mn(2+), Na(+), Ni(2+), Pb(2+), and Zn(2+)). The best detection of Fe(3+) was achieved in a pH range from 3 to 9. In addition, the P(2)O(7)(4-)-AuNPs were also used to detect Fe(3+) in lake water samples, with low interference.     

A new perylene diimide-based colorimetric and fluorescent sensor for selective detection of Cu<Superscript>2+</Superscript> cation

A new perylene diimide (PDI) ligand (1) functionalized with a dipicolylethylenediamine (DPEN) moiety was synthesized and first used as a colorimetric and fluorometric dual-channel sensor to specifically detect the presence of Cu²⁺ over a wide range of other cations. The solution of 1 (10 μmol/L) upon addition of Cu²⁺ displayed distinguishing pink color compared with other cations including K⁺, Ni²⁺, Ca²⁺, Mn²⁺, Na⁺, Sr²⁺, Zn²⁺, Co²⁺, Cd²⁺, Mg²⁺, Cr³⁺, Ag⁺, and Ba²⁺, indicating the sensitivity and selectivity of 1 to Cu²⁺. Thus, the advantage of this assay is that naked-eye detection of Cu²⁺ becomes possible. Moreover, among these metal ions investigated, only Cu²⁺ quenched more than half fluorescent intensity of 1. The ESI-TOF spectrum of a mixture of 1 and CuCl₂ in combination of the fluorescence titration spectra of 1 (10 μmol/L) upon addition of various amounts of Cu²⁺ revealed the formation of a 2:1 metal-ligand complex through the metal coordination interaction. Supported by the National Natural Science Foundation of China (Grant Nos. 20872101 & 20772086)     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Radiation-Chemical Reduction of Cd<Superscript>2+</Superscript> Ions in Aqueous Solution

Formation of the metal is observed under irradiation of methanol-containing aqueous solutions of cadmium salts with accelerated electrons. The process of precipitation of the metal and its properties was examined. The radiation-chemical yield is (1.7 ± 0.2) × 10^–2 g kGy. The efficiency of the radiation-induced reduction of a number of other metals in aqueous media: copper, lead, and thallium, was substantiated. The method may be promising for obtaining deposits of pure and amorphous metals from aqueous solutions of their salts and for purification of aqueous effluents containing these toxic metals.     

Coupled thermogravimetric-IR techniques and kinetic analysis by non-isothermal decomposition of Cd<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> vinyl-phosphonates

The thermal behavior of Cd²⁺ and Co²⁺ vinyl-phosphonates was studied using two different experimental strategies: the coupled TG–EGA (FTIR) technique by decomposition in nitrogen, respectively, air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. The both compounds exhibited a good thermal stability: in nitrogen, only an endothermic dehydration step was observed. In air the Cd²⁺ salt presents the same dehydration step whereas by the Co²⁺ salt two simultaneous processes take place dehydration, respectively, thermooxidative destruction of the vinyl group. The kinetic analysis of the TG data was performed with the Flynn–Wall–Ozawa, Friedman’s, and modified non-parametric kinetic methods. By means of the coupled techniques, some spectroscopic arguments on the reaction mechanism were obtained. The values of the activation energy by the three methods are in good agreement and support the two different suggested mechanism.     

Extraction of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, and Co<Superscript>2+</Superscript> ions from aqueous solutions with calcium and magnesium phosphates

The efficiency of calcium and magnesium phosphates of different compositions in the extraction of Cu²⁺, Zn², and Co²⁺ ions from aqueous solutions was studied.     

Selective extraction of Fe<Superscript>3+</Superscript> ions from Fe<Superscript>3+</Superscript>-Zn<Superscript>2+</Superscript> mixture with phosphate sorbents

The absorption of Fe³⁺ ions from Fe³⁺-Zn²⁺ mixture with zinc and calcium phosphates was studied.     

Optical and thermoluminescence properties of a NaCl single crystal doped with Cd<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript> and exposed to gamma-rays

The thermoluminescense (TL) behavior of solid solutions of cadmium and manganese doped single crystals under γ-irradiation is reported. Various compositions of single crystals of NaCl doped with Cd²⁺ and Mn²⁺ have been irradiated with ionizing radiation. The increase in the glow curve was followed as a function of the F-centers produced by the dose. The analysis shows the potential use of these materials as dosimeters.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Extraction of Ba<Superscript>2+</Superscript>, Pb<Superscript>2+</Superscript> and Cd<Superscript>2+</Superscript> into nitrobenzene by using strontium dicarbollylcobaltate in the presence of tetramethyl <Emphasis Type="Italic">p-tert</Emphasis>-butylcalix[4]arene tetraketone

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq)+SrL²⁺(nb)⇔ML²⁺(nb)+Sr²⁺(aq) taking place in the two-phase water-nitrobenzene system (M²⁺ = Ba²⁺, Pb²⁺, Cd²⁺; L = tetramethyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the ML²⁺ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Ba²⁺<Cd²⁺<Pb²⁺.     

Complex formation of maleic acid with the Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> in aqueous solution

The process of complex formation of maleic acid (H₂L) with the ions Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ was studied by potentiometric titration in a wide range of concentration ratios at 298 K and I = 0.1 mol/l (NaNO₃). The moieties ZnL, CoL, NiL, NiL ₂ ^2? , CuL, and CuL ₂ ^2? were detected and their stability constants were determined.     

Two novel coordination polymers: Synthesis,structure, luminescent properties,and selective sensing of Cu<Superscript>2+</Superscript> and Mn<Superscript>2+</Superscript> ions

Two novel coordination polymers, namely {[Co(Ttac)_0.5(1,4-Bib)(H₂O)] · H₂O}_n (I) and {[La(HTtac)₂(2H₂O)] · H₂O}n (II) (H4Ttac = 4,5-di(3'-carboxylphenyl)-phthalic acid, 1,4-Bib = 1,4-bis(1-imidazoly) benzene), have been designed and successfully prepared via hydrothermal process, and characterized by elemental analyses, IR spectroscopy, and single crystal X-ray diffraction (CIF files CCDC nos. 1039298 (I), 1039300 (II)). Structural analysis reveals that the H₄Ttac ligands adopt different coordination modes in the as-synthesized I and II, and thus give rise to the targeted coordination polymers with different configurations. It is worth mentioning that, coordination polymer I is assembled from low-dimensional structures into three-dimensional (3D) via π···π stacking interactions, while three-dimensional coordination polymer II is formed by covalent bonds. Luminescent properties of coordination polymer II have been studied at ambient temperature. Significantly, luminescent measurement indicates that coordination polymer II may be acted as potential luminescent recognition sensors towards Cu²⁺ and Mn²⁺ ions.     

Sorption of Cd<Superscript>2+</Superscript> with the product formed by alkali treatment of boron production wastes

Experiments on sorption of Cd²⁺ ions from aqueous CdCl₂ solutions with calcium hydrosilicate prepared from borogypsum (boron production waste) showed that this cheap sorbent can be used for effi cient sorption of Cd²⁺ ions in a wide range of solid: liquid ratios.