High Metal Ion Concentrations Research Articles

Combined experimental and DFT study on the adsorption of Co(II) and Zn(II) from fuel ethanol by Schiff base decorated magnetic Fe3O4 composites

Schiff base decorated magnetic composites (Fe3O4@SiO2-HO-S and Fe3O4@SiO2-HE-S) were synthesized via homogeneous and heterogeneous method, respectively. The adsorption property for Co(II) and Zn(II) from ethanol was investigated systematically by considering the effects of contact time, temperature, initial metal ion concentration, and coexisting metal ion. Result shows that the magnetic composites exhibit better adsorption performance toward Co(II) and Zn(II) as compared with Fe(III), Cd(II), and Cu(II). The adsorption of Co(II) and Zn(II) can reach equilibrium at about 175 and 200 min, respectively. Adsorption kinetic can be well fitted by pseudo-second-order model and is controlled by film diffusion process. Adsorption isotherm indicates that the adsorption favors high initial metal ion concentration and temperature. The adsorption isotherm suggests the adsorption proceeds by monolayer behavior and chemical mechanism. Thermodynamic parameters demonstrate that the adsorption is exothermic, spontaneous, and entropy increased process. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation demonstrate the participation of nitrogen and oxygen atoms during the adsorption, and nitrogen atoms play the dominant role for the adsorption. Regeneration indicates Fe3O4@SiO2-HE-S and Fe3O4@SiO2-HO-S can be reused as promising adsorbents for the removal of metal ion from ethanol.

Binding of tetracycline to its aptamer determined by 2D-correlated Mn2+ hyperfine spectroscopy.

The tetracycline-binding RNA aptamer (TC-aptamer) binds its cognate ligand the antibiotic tetracycline (TC) via a Mg2+ or Mn2+ ion with high affinity at high divalent metal ion concentrations (KD=800pM, ⩾10 mM). These concentrations lie above the physiological divalent metal ion concentration of ca. 1 mM and it is known from literature, that the binding affinity decreases upon decreasing the divalent metal ion concentration. This work uses a Mn2+ concentration of 1 mM and 1D-hyperfine experiments reveal two pronounced 31P couplings from the RNA besides the 13C signal of 13C-labeled TC. From these 1D-hyperfine data alone, however, no conclusions can be drawn on the binding of TC. Either TC may bind via Mn2+ to the aptamer or TC may form a free Mn-TC complex and some Mn2+ also binds to the aptamer. In this work, we show using 2D-correlated hyperfine spectroscopy at Q-band frequencies (34 GHz), that the 13C and 31P signals can be correlated; thus arising from a single species. We use THYCOS (triple hyperfine correlation spectroscopy) and 2D ELDOR-detected NMR (2D electron electron double resonance detected NMR) for this purpose showing that they are suitable techniques to correlate two different nuclear spin species (13C and 31P) on two different molecules (RNA and TC) to the same electron spin (Mn2+). Out of the two observed 31P-hyperfine couplings, only one shows a clear correlation to 13C. Although THYCOS and 2D EDNMR yield identical results, 2D EDNMR is far more sensitive. THYCOS spectra needed a time factor of ×20 in comparison to 2D EDNMR to achieve a comparable signal-to-noise.

Role of phytocystatin in combating metal ion induced conformational alterations in glutathione reductase.

Glutathione reductase (GR) is a flavoprotein that catalyses the reduction of oxidized glutathione (GSSG) to reduced glutathione (2GSH) in the presence of coenzyme NADPH. The importance of glutathione stems from the fact that it serves an important role in various metabolic processes. Plants growing in highly polluted areas are exposed to higher concentration of metal ions; thereby feeling abiotic stress and affecting various regulatory enzyme activities. In this study, effect of metal ions has been studied on GR. Phytocystatins show an increased expression in abiotic stress conditions. Here in, the effect of cystatin isolated from yellow mustard seeds (YMP) on heavy metals induced conformational changes in GR was investigated making use of GR activity assay, UV-absorption spectroscopy, fluorescence spectroscopy, FTIR, CD, ITC and SEM analysis. The results obtained clearly reveals that metal ions like Cu2+ and Zn+2 induces concentration dependent conformational changes in GR; YMP restores these alterations in way decreasing the effective concentration of metal ions.

Insights into the single and binary adsorption of copper(II) and nickel(II) on hexagonal boron nitride: Performance and mechanistic studies

A series of hexagonal boron nitrides (h-BNs) was developed using a facile method involving pyrolysis of urea and boric acid mixture at different temperatures. The as-prepared h-BNs were characterized using XRD, FESEM, FTIR, BET and XPS and the results indicated that the as-prepared h-BNs consist of microparticle structures with BET specific surface area between 12–18 m2 g−1. The h-BN prepared at 750°C (BN-750) displayed excellent adsorption capacities for both Cu(II) and Ni(II) (up to 200 and 95 mg g−1, respectively) compared to those prepared at other temperatures. At higher metal ion concentrations (>250 mg L−1), multilayer adsorption was observed. The equilibrium adsorption modelling study indicated that the adsorption process was best fitted to the Langmuir (R2>0.97) and Sips (R2>0.98) isotherm models. The binary adsorption of Cu(II) and Ni(II) was also investigated and the results revealed that the BN-750 has higher adsorption affinity for Cu(II) compared to Ni(II). Detailed analyses of the spent adsorbent using XPS and FTIR indicated that the oxygen functional groups of BN-750 played an important role in facilitating the electrostatic attraction and complexation of heavy metal during adsorption process. Furthermore, the results confirmed that Cu(II) and Ni(II) occupied the same active sites on BN-750. The results of this study revealed insights into the adsorption mechanism of Cu(II) and Ni(II) on BN-750 and demonstrated that the as-prepared h-BN is a promising adsorbent for efficient heavy metal removal in aqueous system.

A novel method for preparing microcrystalline cellulose from bleached chemical pulp using transition metal ions enhanced high temperature liquid water process

A novel method for preparing microcrystalline cellulose (MCC) from bleached chemical pulp based on the transition metal ion-enhanced high temperature liquid water (HTLW) process was established in this study. Transition metal ions (Fe3+, Cu2+ or Cr3+) were used to enhance the depolymerization effect of HTLW treatment on fibers. Hemicelluloses are selectively removed, resulting in an increase in the α-cellulose content; cellulose undergoes hydrolytic degradation, causing a significant decrease in the average degree of polymerization (DP). SEM images indicated that the as-prepared MCC had granular or rod-like shape. The repose angle results showed a desirable fluidity of obtained MCC. The copper number results showed an increase in the reducing end groups of the obtained MCC. The XRD analysis indicated that the cellulose crystallite exhibited negligible changes, and the crystallization index (CI) increased. However, a very high concentration of transition metal ions lowered the CI. The transition metal ion-enhanced HTLW treatment provides an acid free method for preparing MCC.

Metal ion concentrations after metal-on-metal hip arthroplasty are not correlated with habitual physical activity levels.

Metal-on-metal (MoM) hip arthroplasties have shown high clinical failure rates with many patients at risk for a revision and under surveillance for high metal ion concentrations. Implant wear releasing such ions is assumed to be a function of use, i.e. the patient's physical activity. This study aimed to assess whether habitual physical activity levels of MoM patients are correlated with metal ion concentrations and are higher in patients with high (at risk) than in patients with low (safe) metal ion concentrations. A cohort study was conducted of patients with any type of MoM hip prosthesis. Metal ion concentrations were determined using ICP-MS. Habitual physical activity of subjects was measured in daily living using an acceleration-based activity monitor. Outcome consisted of quantitative and qualitative activity parameters. In total, 62 patients were included. Mean age at surgery was 60.8 ± 9.3 years and follow-up was 6.3 ± 1.4 years. Cobalt concentrations were highly elevated overall (112.4 ± 137.9 nmol/L) and significantly more in bilateral (184.8 ± 106.5 nmol/L) than in unilateral cases (87.8 ± 139.4 nmol/L). No correlations were found between physical activity parameters and metal ion concentrations. Subgroup analysis of patients with low versus high cobalt concentration showed no significant differences in habitual physical activity. No correlation was found between physical activity levels and metal ion concentrations. Implant use by normal habitual activities of daily living seems not to influence metal ion concentrations.

Adsorption property and mechanism of PAMAM dendrimer/silica gel hybrids for Fe(III) and Ag(I) from N,N‑dimethylformamide

A series of amine-terminated polyamidoamine (PAMAM) dendrimer/silica gel hybrids (SiO2-G1.0, SiO2-G2.0 and SiO2-G3.0) were synthesized and used for the adsorption of Fe(III) and Ag(I) from N,N‑dimethylformamide. The effects of time, temperature, initial metal ion concentration, and adsorbent dosage on the adsorption were determined. Results show that the adsorption capacity for both Fe(III) and Ag(I) followed the order of SiO2-G2.0 > SiO2-G1.0 > SiO2-G3.0. Adsorption kinetic shows that the adsorption process follows the pseudo-second-order kinetic model and is controlled by film diffusion process. Isotherm adsorption indicates the adsorption favors high temperature and metal ion concentration. The isotherm adsorption can be fitted well by Langmuir model and carries out by monolayer adsorption behavior. The calculated mean free energy E suggests the adsorption proceeds by chemical mechanism. The removal rate increases and adsorption capacity decreases with the increase of adsorbent dosage. DFT calculation demonstrates the formation of tetra- and penta-dentate chelates with the involvement of primary amine N, secondary amine N, carbonyl O atoms dominate the coordination of G1.0 with Ag(I).

(Invited) Electrodeposition of Equiatomic Fe-Ni Films

Current permanent magnets such as NdFeB contain a significant fraction of rare earths (Dy, Nd), resulting in an increasing cost and higher supply risk. Potential low cost substitutes include the L10 tetragonal structure of equiatomic Mn-Al and the L10 equiatomic Fe-Ni. While the former exhibits a relatively low energy product (~ 110 kJ/m3), the latter material may approach the energy product of Nd-Fe-B. We have grown equiatomic Fe-Ni films by electrodeposition at both very low and very high growth rate, in order to understand the influence of the driving force for growth on the morphology and the defectivity of the films. A citrate/glycinate electrolyte with low metal ion concentration exhibited after annealing at 300 C a coercivity of 1000 Oe, which cannot be ascribed only to internal stresses. A sulfate based electrolyte with high metal ion concentration, suitable to achieve high growth rates, presents a large defect density. The talk will cover the synthesis and characterization of the materials, with emphasis on the crystal structure and the correlation between microstructure, phase and magnetic properties.

Ultra-stable L-proline protected copper nanoclusters and their solvent effect

Water-soluble and ultra-stable L-proline-protected copper nanoclusters (Cu NCs) are reported, which overcome the bottleneck that Cu NCs are easily oxidized. The average size of Cu NCs is found to be 1.88 ± 0.17 nm. The as-prepared Cu NCs exhibit an excellent stability over the physiologically relevant pH range, long storage time, high ionic strength, high concentration of hydrogen peroxide and various common metal ions. The fluorescence intensity of Cu NCs maintains no change after 5 months stored in the refrigerator. Interestingly, the Cu NCs show a pH-dependent fluorescence behavior between 9 and 13, and the reversible process can be repeated for 8 consecutive cycles with the excellent reversibility of the fluorescence intensity. Moreover, the as-prepared Cu NCs display the solvent-dependent properties in the dimethyl sulfoxide and ethylenediamine, where the emission color turn to be green and yellow from blue, respectively. This unique fluorescence property of Cu NCs will make them serve as good probes in analytical applications.

Efficient detection and adsorption of cadmium(II) ions using innovative nano-composite materials

In this study, a ligand was anchored with mesoporous silica, named as nano-composite materials, was applied in the detection and adsorption of cadmium (Cd(II)) ions from wastewater samples. The effects of solution pH, color optimization, limit of detection, contact time, initial concentration, ion selectivity and regeneration were systematically performed in the case of detection and adsorption operations. The solution pH was played an important factor both in the case of detection and adsorption, and the optimum pH were selected at 5.50 based on the high absorbance and adsorption ability. Upon addition of Cd(II) ions, the nano-composite materials was provided an excellent color, which was observed by the naked-eye. The detection limit was calculated to be 0.33 µg/L, which was lower than the permissible limit. Therefore, the Cd(II) ions was detected without using any sophisticated instruments. The equilibrium isotherm has been analyzed using Langmuir isotherm models, and the maximum adsorption capacity was 148.32 mg/g. The results clarified that the nano-composite material had the higher selectivity towards Cd(II) ions even in the presence of high concentration of divers metal ions. The material was reused in several cycles after elution operation with a suitable eluent of 0.25 M HCl. The nano-composite materials exhibited an excellent reusability because of its remarkable mechanical strength and highly efficient elution/regeneration operations ability. In the static treatment process, after seven cycles, Cd(II) ions was adsorbed efficiently and holding over 93% adsorption efficiency. The developed ligand functionalized nano-composite materials is quite simple and rapid with excellent repeatability for Cd(II) ions capturing and has a great potential for potential scale up for field application in real wastewater samples.

Modeling the interaction and toxicity of Cu-Cd mixture to wheat roots affected by humic acids, in terms of cell membrane surface characteristics

Responses of wheat (Triticum aestivum L.) seedling roots to the mixtures of copper (Cu), cadmium (Cd) and humic acids (HA) were investigated using the solution culture experiments, focusing on the interaction patterns between multiple metals and their influences on root proton release. A concentration-addition multiplication (CA) model was introduced into the modeling analysis. In comparison with metal ion activities in bulk-phase solutions, the incorporation of ion activities at the root cell membrane surfaces (CMs) (denoted as {Cu2+}0 and {Cd2+}0) into the CA model could significantly improve their correlation with RRE (relative root elongation) from 0.819 to 0.927. Modeling analysis indicated that the co-existence of {Cu2+}0 significantly enhanced the rhizotoxicity of {Cd2+}0, while no significant effect of {Cd2+}0 on the {Cu2+}0 rhizotoxicity. 10 mg/L HA stimulated the root elongation even under metal stress. Although high concentration of metal ions inhibited the root proton release rate (ΔH+), both the low concentration of metal ions and HA treatments increased the values of ΔH+. In HA-Cu-Cd mixtures, actions of metal ions on ΔH+ values were varied intricately among treatments but well modeled by the CA model. We concluded from the CA models that the electrostatic effect is vitally important for explaining the effect of {Cu2+}0 on the rhizotoxicity of {Cd2+}0, while it plays no unique role in understanding the influence of {Cd2+}0 on the rhizotoxicity of {Cu2+}0. Thus our study provide a novel way for modeling multiple metals behaviors in the environment and understanding the mechanisms of ion interactions.

Impact of a commercial glyphosate formulation on adsorption of Cd(II) and Pb(II) ions on paddy soil

Use of glyphosate as a weedicide on rice cultivation has been a controversial issue in Sri Lanka, due to the hypothesis that the metal complexes of commercial glyphosate is one of the causative factors of Chronic Kidney Disease of unknown aetiology (CKDu) prevalent in some parts of Sri Lanka. The effect of commercial glyphosate on the adsorption and desorption of Cd(II) and Pb(II) ions on selective paddy soil studied using batch experiments, over a wide concentration range, indicates that the Langmuir adsorption isotherm model is obeyed at low initial metal ion concentrations while the Freundlich adsorption isotherm model obeys at high metal ion concentrations in the presence and absence of glyphosate. For all cases, adsorption of both Cd(II) and Pb(II) ions obeys pseudo second order kinetics, suggesting that initial adsorption is a chemisorption process. In the presence of glyphosate formulation, the extent of adsorption of Cd(II) and Pb(II) ions on soil is decreased, while their desorption is increased at high concentrations of glyphosate. Low concentrations of glyphosate formulation do not significantly affect the desorption of metal ions from soil. Reduction of adsorption leads to enhance the concentration of Cd(II) and Pb(II) ions in the aqueous phase when in contact with soil.

Heterologous expression of Oenococcus oeni sHSP20 confers temperature stress tolerance in Escherichia coli.

Small heat shock proteins (sHSPs) are heat shock proteins sized 12-43kDa that can protect proteins from denaturation, particularly under high temperature; sHSPs thus increase the heat tolerance capability of an organisms enabling survival in adverse climates. sHSP20 is overexpressed in Oenococcus oeni in response to low temperatures. However, we found that overexpression of sHSP20 in Escherichia coli BL21 increased the microbial survival ratio at 50°C by almost 2h. Adding sHSP20 to the glutamate dehydrogenase solution significantly increased the stability of the enzyme at high temperature (especially at 60-70°C), low pH values (especially below 6.0), and high concentration of metal ions of Ga2+, Zn2+, Mn2+, and Fe3+. Notably, the coexpression of sHSP20 significantly enhanced soluble expression of laccase from Phomopsis sp. XP-8 (CCTCCM209291) in E. coli without codon optimization, as well as the activity and heat stability of the expressed enzyme. In addition to the chaperone activity of sHSP20 in the gene containing host in vivo and the enzyme heat stability in vitro, our study indicated the capability of coexpression of sHSP20 to increase the efficiency of prokaryotic expression of fungal genes and the activity of expressed enzymes. Graphical abstract ᅟ.

Adaptive Strategies of Bacillus thuringiensis Isolated from Acid Mine Drainage Site in Sabah, Malaysia

The adaptive process in bacteria is driven by specific genetic elements which regulate phenotypic characteristics such as tolerance to high metal ion concentrations and the secretion of protective biofilms. Extreme environments such as those associated with heavy metal pollution and extremes of acidity offer opportunities to study the adaptive mechanisms of microorganisms. This study focused on the genome analysis of Bacillus thuringiensis (Bt MCMY1), a gram positive rod shaped bacterium isolated from an acid mine drainage site in Sabah, Malaysia by using a combination of Single Molecule Real Time DNA Sequencing, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The genome size of Bt MCMY1 was determined to be 5,458,152 bases which was encoded on a single chromosome. Analysis of the genome revealed genes associated with resistance to Copper, Mercury, Arsenic, Cobalt, Zinc, Cadmium and Aluminum. Evidence from SEM and FTIR indicated that the bacterial colonies form distinct films which bear the signature of polyhydroxyalkanoates (PHA) and this finding was supported by the genome data indicating the presence of a genetic pathway associated with the biosynthesis of PHAs. This is the first report of a Bacillus sp. isolated from an acid mine drainage site in Sabah, Malaysia and the genome sequence will provide insights into the manner in which B. thuringiensis adapts to acid mine drainage.

Microorganism and Agricultural Based Biosorbents Towards Removal of Cadmium from Waste-Water: An Overview.

Non-degradable and persistent nature of Cadmium (Cd) poses high toxicity to human, plants and animals. Several industrial processes generated wastes are the main anthropogenic pathway through which Cd enters into the environment. Although, World Health Organization (WHO) has set the limit of Cd in drinking water is 0.005 mg L-1, the industrial activities release much higher concentrations of metal ions to the water stream than the prescribed limits, which leads to the increasing health hazards and environmental pollution. To address this issue, one of the major applicable solutions is the treatment or purification of contaminated water and effluents. The implantation of wastewater treatment systems aims to minimize environmental impacts, but ultimately generates waste materials, such as sewage sludge, which must be properly recycled. In this review, we focus on the research efforts being made towards the removal of Cd (II) from waste waters using biological means with a special emphasis on the microorganism and agricultural based biosorbents. Mechanistic pathway towards removal of Cd (II) ions from the wastewater, efficiency of the adsorbents and the factors affecting the process have been studied with specific examples. Also the recent patents related to this area have been taken into considerations to understand applicability of microorganism and agricultural based biosorbents. This overview presents various scientific reports towards low-cost microorganism and agricultural based biosorbents for efficient removal of Cd (II) by producing less toxic waste and the future perspective of the process.

Applicability of alkaline precipitation for the recovery of EDDS spent solution

This paper presents an innovative procedure for the recovery of SS-ethylenediamine-N,N′-disuccinic acid (EDDS) solution used for soil washing processes. The procedure is derived from that applied for the recovery of ethylenediamine-tetraacetic acid (EDTA), modifying and optimizing the choice of the chemical agents used for the protonation of the chelant, the exchange of the metals, and the final precipitation of the unwanted compounds.To select the reagents and test the proposed approach, an experimental study was conducted on real EDDS spent solutions, obtained washing a Cu and Zn real contaminated soil. According to the results obtained, the precipitation ranges from 30% to more than 90% for both Cu and Zn, depending on the adopted reagent sequence, and on the molar ratio between the salt and the chelant contained in the spent solution. Data were in agreement with chemical equilibrium predicted in ideal conditions. The recovered solutions had a reduced ability to remove the contaminants when applied in a new soil washing cycle (15% less for Cu and 30% less for Zn) because of the high concentration of alkaline metal ions required for the precipitation. At the same time, they were more biodegradable compared to non-treated solutions, confirming that EDDS-metal chelates may represent a threat for biological wastewater processes.

Optimization of conditions for polycyclic aromatic hydrocarbons (PAHs) degradation by Pseudomonas stutzeri P2 isolated from Chirimiri coal mines

Abstract A potent phenanthrene and pyrene degrading bacterial strain P2 was isolated from soil sample collected from the Chirimiri coal mines in central India. As determined through atomic absorption spectroscopy, a high concentration of heavy metal ions like lead, mercury and arsenic were found in the soil sample. The bacterial strain P2 was identified as Pseudomonas stutzeri through a polyphasic approach. The degradation conditions for phenanthrene and pyrene biodegradation was optimized through Taguchi orthogonal array. At optimized conditions, the strain could degrade 98% and 92.6% of phenanthrene and pyrene at a concentration of 1000 mg l−1 and 500 mg l−1 in 7 and 10 days, respectively. The pH of the medium dropped during degradation studies suggesting the accumulation of acidic metabolites during biodegradation by the isolated strain. The gas chromatography–mass spectrometry analysis of phenanthrene and pyrene degradation products showed the presence of pthalic acid derivatives. PCR amplification of dioxygenase genes produced fragments of 350 bp, 867 bp and 350 bp in length for PAH-RHD, catechol 2, 3-dioxygenase and catechol 1, 2-dioxygenase, respectively suggesting the representative of Pseudomonas as the significant PAHs degrader. The bacterial strain was found to be biosurfactant producing, and the role of biosurfactant in PAHs degradation was also determined by higher emulsification index and reduced surface tension of the medium. Significantly, the Pseudomonas strain could tolerate heavy metals and utilize a range of mono and polyaromatic as the sole source of carbon. Hence, this strain has a remarkable potential for application in bioremediation of hydrocarbon contaminated sites.

Effect of pH values on extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

The effect of pH values on the extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans was comparatively investigated in different phases of bacterial growth during chalcopyrite bioleaching. The results indicate that the extracellular protein is always more than the extracellular polysaccharide secreted by attached cells on the chalcopyrite, on the contrary, and is always less than the extracellular polysaccharide secreted by free cells in the solution at bacterial adaptive phase, logarithmic phase and stationary phase whenever pH value is at 1.0, 1.5, 2.0 or 2.5; free cells are mainly through the secretion of extracellular polysaccharide rather than the extracellular protein to fight against disadvantageous solution environment, such as high concentration of metal ions and unsuitable pH solution; both amounts of polysaccharide and protein secreted by attached cells are mainly positively related to the solution acidity rather than the total concentration of soluble metal ions. The experimental results imply that bacteria are mainly through secreting more extracellular polysaccharide to fight against disadvantageous environment and the extracellular protein perhaps plays an important role in oxidation–reduction reactions in the bioleaching system.

Distribution of Trace Elements in Groundwater around Beris Lalang Landfill Bachok, Kelantan, Malaysia

The present study was conducted in the vicinity of Beris Lalang landfill, part of state Kelantan, Malaysia to determine the distribution of trace elements concentration in groundwater. A total of eleven groundwater samples and two surface water samples were analyzed for lead (Pb), manganese (Mn), copper (Cu), zinc (Zn), iron (Fe), chromium (Cr) and aluminium (Al) using Atomic Absorption Spectrophotometer (AAS). These probe elements were further categorized as toxic metals (i.e. Pb), transition metals (i.e. Mn), metallic elements (i.e. Cu, Fe, Zn, Cr), and non-metallic elements (i.e. Al). This study shows that few groundwater samples have marginally high concentration of Mn, Pb, Fe and Cr as per W.H.O. standard for potable water. The high concentration of metal ions in groundwater is likely due to untreated effluents from landfill site, municipal wastewater, fertilizers and other activities. To help identifying the contamination sources, the study recommends that regular monitoring of the groundwater quality should be undertaken both temporally and spatially that can contribute in public health and as well agricultural uses.

Highly selective and sensitive fluorescent sensor: Thiacalix[4]arene-1-naphthalene carboxylate for Zn2+ ions

Thiacalix[4]arene based fluorescent sensor bearing two naphthoyl groups, thiacalix-1-naphthalene carboxylate (TCNC) has been synthesized and characterized by 1H NMR, 13C NMR, FTIR, ESI-MS spectroscopic techniques. The interaction behavior of TCNC with various metal ions like Fe3+, Hg2+, Co2+, Ni2+, Cu2+, Cd2+, Pb2+, Mg2+, K+, Na+, and Zn2+ was studied by UV-visible and emission spectrophotometry. It was observed that TCNC recognizes Zn2+ ions with high selectivity and sensitivity. The enhancement of fluorescence intensity due to presence of Zn2+ ions was not perturbed in the presence of high concentration of other associated metal ions. The 1:1 stoichiometry of TCNC:Zn2+ complex was confirmed by job's plot, ESI-MS study and 1H NMR titration. The binding constant and quantum yield were also calculated by using spectrofluorimetric titration data. Linear detection range of zinc ions was found to be 1 nM–740 nM. Furthermore, molecular docking study was performed to evaluate the binding affinity and possible interactions between TCNC and Zn2+ depicting that TCNC interact with Zn2+ via weak intramolecular forces. In addition to that molecular dynamics has also been performed to evaluate the conformational changes and it's structural stability in the particular environment.