A new rhodamine-based single molecule multianalyte (Cu, Hg) sensor and its application in the biological system

A new single molecule multianalyte sensor, vanillic aldehyde rhodamine 6G hydrazone has been designed for the selective detection of Cu²⁺ and Hg²⁺ ions. UV/Vis spectroscopy indicates that the sensor is a good chromogenic chemosensor for Cu²⁺ in 1:99 (v/v) ethanol-water media. Whereas, other ions, such as Li⁺, Na⁺, Mg²⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Ag⁺, Cd²⁺, Ba²⁺, Hg²⁺ and Pb²⁺ failed to generate a distinct response. Fluorescence spectral data reveals that the sensor is an excellent fluorescent chemosensor for Hg²⁺ in aqueous ethanol solution and with no fluorescent response toward other ions. The spectroscopic behavior of the sensor in living cells indicated that it can be used for the detection of Cu²⁺ and Hg²⁺ in environmental and biological systems. Mechanisms for the high selectivity of the sensor to Cu²⁺ and Hg²⁺ are discussed.     

2-Mercaptoimidazole Covalently Bonded to a Silica Gel Surface for the Selective Separation of Mercury(II) from an Aqueous Solution

Abstract

Silica gel with a specific surface area of 365 m²·g^?1 and an average pore diameter of 60 Å was chemically modified with 2-mercaptoimidazole. The degree of functionalization of the covalently attached molecule, (≡SiO)₃(CH₂)₃—MI, where MI is the 2-mercaptoimidazole bound to the silica surface by a propyl group, was 0.58 mmol·g^?1. In individual metal adsorption experiments from aqueous solutions by the batch procedure, the affinity order was Hg^II « Cd^II > Cu^II ～ Zn^II ～ Pb^II > Mn^II at solution pHs between 4 and 7. Due to the high affinity by the sulfur atom, Hg^II is strongly bound to the functional groups. When solution containing a mixture of Hg^II, Cd^II, Cu^II, Zn^II, Pb^II, and Mn^II ions was passed through a column packed with the adsorbent, Hg^II was the only one whose adsorption and elution was not affected by the presence of other ions.     

Adsorption properties of Pb2+ on thermal-activated serpentine

ABSTRACT

Adsorption properties of nature and thermal-activated serpentines to Pb²⁺ in aqueous solution were investigated. The results showed that Freundlich isotherm and pseudo-second-order kinetics model were suitable to describe the adsorption process of Pb²⁺ on serpentines. The thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous. The serpentine activated at 700°C exhibited maximum adsorption capacity to Pb²⁺. Based on the XRD and XPS characterization, it could be found that the structure of serpentine did not change significantly during the adsorption process, and Pb²⁺ was adsorbed on the serpentine surface as the precipitation of Pb(OH)Cl and Pb(OH)₂.     

Highly luminescent near-infrared emitting gold nanoclusters with further natural etching : photoluminescence and Hg2+ detection

ABSTRACT: Highly luminescent near-infrared (NIR) emitting gold nanoclusters (Au NCs) protected by glutathione (GSH) with ultra-small size were prepared at high temperature following with a further natural etching at room temperature (RT). The optical and surface properties of Au NCs were monitored by ultraviolet and visible (UV-vis), photoluminescence (PL) spectra, high-resolution transmission electron microscopy (HRTEM), and electro spray ionization mass spectrometry (EIS-MS). The diameter of the etched Au NCs was reduced to ~1.35 nm with 30% PL quantum yield (QY). Interestingly, the PL of Au NCs was decreased obviously by addition of Hg2+ and increased by addition of Pb2+ at certain concentration. Our preliminary results illustrated that the highly luminescent NIR-emitting Au NCs would be an alternative probe for the detection of heavy metal ions in water and environmental monitoring.     

硫酸改性甘草废渣生物吸附剂对Pb~(2+)离子的吸附

以甘草废渣为原料,经硫酸处理得到了改性甘草废渣生物吸附剂,并将其用于对水溶液中重金属离子Pb2+的吸附。通过扫描电镜、红外光谱、比表面积和表面官能团的测定等方法对改性前后甘草废渣进行了表征。采用静态吸附实验,考察了Pb2+初始浓度、吸附时间、溶液p H值及投入量对吸附剂吸附性能的影响。经硫酸改性后,甘草废渣表面结构发生了变化,表面活性基团的数目增加。在p H=5.5,对浓度为1 mmol·L-1的含Pb2+离子溶液,经90 min吸附后,吸附率达97.43%。等温吸附符合Langmuir模式,根据Langmuir方程计算,25℃时饱和吸附量为1.12 mmol·L-1,高于改性前(0.8 mmol·L·-1)。甘草废渣吸附剂对Pb2+离子的吸附符合二级动力学方程。解吸再生实验表明改性后的甘草废渣吸附剂可以再生重复使用5次以上,是性能良好的重金属离子吸附剂。     

测试——聚乙烯亚胺改性磁性膨润土对Pb2+和Cu2+的吸附性能(测试稿件)

在磁性膨润土(MBent)表面接枝聚乙烯亚胺(PEI)制备了聚乙烯亚胺改性磁性膨润土(PEI/KH560/MBent),采用FTIR、VSM、XRD、TGA、EA、SEM和EDS对其进行了表征,考察了其对水溶液中Pb_²⁺和Cu_²⁺的吸附性能。结果表明,聚乙烯亚胺已成功接枝于磁性膨润土表面,并有效提高其对Pb_²⁺和Cu_²⁺吸附量；溶液初始pH对吸附量影响较大,随着pH的增大,吸附量增加。在pH=5,溶液初始质量浓度为300 mg/L,PEI/KH560/MBent对Pb_²⁺和Cu_²⁺吸附量分别为96.21和61.08 mg/g；吸附过程符合准二级动力学模型,吸附行为符合Langmuir吸附等温模型。热力学研究表明,吸附为自发吸热过程。经过5次循环利用后,其吸附容量仍保持初始的60%以上,表明PEI/KH560/MBent具有一定的重复利用性。     

Thiacalixarenes with Sulfur Functionalities at Lower Rim: Heavy Metal Ion Binding in Solution and 2D-Confined Space

Sulfur-containing groups preorganized on macrocyclic scaffolds are well suited for liquid-phase complexation of soft metal ions; however, their binding potential was not extensively studied at the air–water interface, and the effect of thioether topology on metal ion binding mechanisms under various conditions was not considered. Herein, we report the interface receptor characteristics of topologically varied thiacalixarene thioethers (linear bis-(methylthio)ethoxy derivative L², O₂S₂-thiacrown-ether L³, and O₂S₂-bridged thiacalixtube L⁴). The study was conducted in bulk liquid phase and Langmuir monolayers. For all compounds, the highest liquid-phase extraction selectivity was revealed for Ag⁺ and Hg²⁺ ions vs. other soft metal ions. In thioether L² and thiacalixtube L⁴, metal ion binding was evidenced by a blue shift of the band at 303 nm (for Ag⁺ species) and the appearance of ligand-to-metal charge transfer bands at 330–340 nm (for Hg²⁺ species). Theoretical calculations for thioether L² and its Ag and Hg complexes are consistent with experimental data of UV/Vis, nuclear magnetic resonance (NMR) spectroscopy, and single-crystal X-ray diffractometry of Ag–thioether L² complexes and Hg–thiacalixtube L⁴ complex for the case of coordination around the metal center involving two alkyl sulfide groups (Hg²⁺) or sulfur atoms on the lower rim and bridging unit (Ag⁺). In thiacrown L³, Ag and Hg binding by alkyl sulfide groups was suggested from changes in NMR spectra upon the addition of corresponding salts. In spite of the low ability of the thioethers to form stable Langmuir monolayers on deionized water, one might argue that the monolayers significantly expand in the presence of Hg salts in the water subphase. Hg²⁺ ion uptake by the Langmuir–Blodgett (LB) films of ligand L³ was proved by X-ray photoelectron spectroscopy (XPS). Together, these results demonstrate the potential of sulfide groups on the calixarene platform as receptor unit towards Hg²⁺ ions, which could be useful in the development of Hg²⁺-selective water purification systems or thin-film sensor devices.     

Synthesis,crystal structures and studies on Hg2+ sensing by the diazo derivatives of sulfathiazole and sulfamethoxazole

Diazocoupling of sulfathiazole and sulfamethoxazole with 2,4-pentanedione led to the syntheses of compounds R1 and R2. These were fully characterized by single crystal X-ray diffraction studies in conjunction with UV–visible, IR, ¹H NMR, and mass spectral studies. Both the compounds were further screened for their possible use in metal ion recognition. Interestingly, compound R1 showed a selective naked-eye response for Hg²⁺, while R2 did not give a color change for any metal ions. These results can be understood in terms of a solvent-assisted low-energy absorption band in R1 that disappeared upon interaction with Hg²⁺. This absorption band was not observed in the case of compound R2 that consequently failed to show any naked-eye color change in the presence of metal ions.     

Study on Efficient Adsorption Mechanism of Pb2+ by Magnetic Coconut Biochar

Lead ion (Pb²⁺) in wastewater cannot be biodegraded and destroyed. It can easily be enriched in living organisms, which causes serious harm to the environment and human health. Among the existing treatment technologies, adsorption is a green and efficient way to treat heavy metal contamination. Novel KMnO₄-treated magnetic biochar (KFBC) was successfully synthesized by the addition of Fe(NO₃)₃ and KMnO₄ treatment during carbonization following Pb²⁺ adsorption. SEM-EDS, XPS, and ICP-OES were used to evaluate the KFBC and magnetic biochar (FBC) on the surface morphology, surface chemistry characteristics, surface functional groups, and Pb²⁺ adsorption behavior. The effects of pH on the Pb²⁺ solution, initial concentration of Pb²⁺, adsorption time, and influencing ions on the adsorption amount of Pb²⁺ were examined, and the adsorption mechanisms of FBC and KFBC on Pb²⁺ were investigated. The results showed that pH had a strong influence on the adsorption of KFBC and the optimum adsorption pH was 5. The saturation adsorption capacity fitted by the model was 170.668 mg/g. The successful loading of manganese oxides and the enhanced oxygen functional groups, as evidenced by XPS and FTIR data, improved KFBC for heavy metal adsorption. Mineral precipitation, functional group complexation, and π-electron interactions were the primary adsorption processes.     

Adsorption of Cu2+ Cations from Aqueous Solution by S-doped TiO2

S-doped TiO₂ as a novel adsorbent for Cu²⁺ cations removal from aqueous solutions was synthesized by simple sol-gel process. Removal of Cu²⁺ cations from aqueous solutions was investigated with particular reference to the effects of initial Cu²⁺ cations concentration, pH-value, adsorbent dosage, and temperature on adsorption. It was found that the maximum adsorption capacity was 96.35 mg g^?1 at 328 K. The adsorption equilibrium isotherms and the kinetic data were well described by the Langmuir and pseudo-second-order kinetic models, respectively. The high uptake capability of S-doped TiO₂ makes it a potentially attractive adsorbent for the removal of heavy metal pollutants from aqueous solution.     

Selective Separation of Nickel (II) and Cobalt (II) from Waste Water by Using Continuous Cross-Flow Micellar Enhanced Ultrafiltration with Addition of Chelating Agent

The performance of continuous cross-flow micellar enhanced ultrafiltration (MEUF) is evaluated for the selective separation of nickel (Ni²⁺) and cobalt (Co²⁺) from the aqueous stream using anionic surfactant sodiumdodecyl sulfate (SDS) and the mixture of the anionic and nonionic surfactant (SDS+TritonX-100) with the addition of iminodiacetic acid (IDA) as a chelating agent. Operating parameters like operating time (upto 100 min), cross flow rate (100–175 mL/min.), pH of the feed solution (3-6 Cheryan , M. ( 1998 ) Process Design in Ultrafiltration and Microfiltration Handbook ; Technomic Publishing Co. Inc : USA . Scamehorn , J.F. ; Ellington , R.T. ; Christian , S.D. ; Penny , B.W. ; Dunn , R.O. ; Bhat , S.N. ( 1986 ) Removal of multivalent metal cations from water using micellar-enhanced ultrafiltration . AIChE Symp. Ser. , 82 ( 250 ): 48 – 58 . Baek , K. ; Yang , J.W. ( 2004 ) Cross flow micellar-enhanced ultrafiltration for removal of nitrate and chromate: competitive binding . J. Hazard. Mater. , B108 : 119 – 123 . Yurlova , L. ; Kryvoruchko , A. ; Kornilovich , B. ( 2002 ) Removal of Ni (II) ions from waste- water by micellar-enhanced ultrafiltration . Desal. , 144 : 255 – 260 . ), molar concentration ratio of the chelating agent to metals (C/M ratio, 0.5–2.5), and molar concentration ratio of the surfactant to metals (S/M ratio, 5–9) were studied to investigate the effectiveness of the process on selective separation. For the single surfactant system at all empirically selected parameters, 92% Ni²⁺ in the permeate and 94% Co²⁺ in the retentate was achieved whereas for the mixed surfactant system 93% Ni²⁺ in permeate and 84% Co²⁺ in retentate was achieved. Flux variation for single and mixed surfactant system was studied. Flux observed for the single surfactant system was 36 L/m².h and for the mixed surfactant system was 31.5 L/m².h. Flux measurement also indicates insignificant fouling of the membrane.     

Synthesis of Artificial Membrane of Copolymer (Acrylic Acid/Butyl Acrylate) PAA-PBA for the Design of Polymersomes

Polymersomes are synthetic vesicles that imitate biological membrane functions. The purpose of this work is to develop an artificial copolymer (acrylic acid/butyl acrylate) PAA-PBA membrane by random synthesis. A factorial design 2^k was applied to determine the conditions for this reaction. The Fourier transform infrared spectrometer indicated that the polymerization reaction was complete without a –C=C-absorption peak. The Gordon-Taylor equation showed that the hydrophilic part of the PAA-PBA composition is 20–40% and the hydrophobic part 60–80%. The authors selected the copolymers with low molecular weight, within the range of 3134.49 ± 994.21 g/mol and a polydispersity of 1.40.     

Siting of Co2+ Ions in Cobalt-Modified High-Silica Zeolites Probed by Low-Temperature Molecular Hydrogen Adsorption

Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy was used to characterize the effects of introducing cobalt into the zeolites ZSM-5 and mordenite. Aqueous impregnation of the hydrogen form of the zeolite and subsequent in vacuo treatment at temperatures up to 920 K results in partial exchange of protons in bridging hydroxyl groups by Co²⁺ cations. These changes are evidenced by a decrease in intensity of the bands at 3606-3609 cm^-1 characteristic of Brønsted acid sites. DRIFT spectra of hydrogen adsorbed at 77 K also confirm the exchange of protons for Co²⁺ cations, as evidenced by a decrease in the intensity of the band at 4106 cm^-1 for H₂ adsorbed on protons. By contrast, the bands at 3905, 3965, and 4010 cm^-1 for H₂ adsorbed on the Co²⁺ cations increase in intensity. With increasing Si/Al ratio at a constant Co loading of 1 wt% the intensity of the band at 3905 cm^-1 for H-ZSM-5 strongly increases in intensity relative to the other bands. This feature is attributed to Co²⁺ cations interacting with two adjacent cation-exchange sites located in a 10-membered ring. It is hypothesized that the Lewis acidity of Co²⁺ cations in such environments is higher than that of Co²⁺ cations associated with oxygen atoms in individual five- or six-membered rings containing two Al atoms, because the Co²⁺ cation can interact with only two of the four basic oxygen anions located in the ring. It is proposed that Co²⁺ cations in the latter type of sites are identified by the bands at 3965 cm^-1 and 4010 cm^-1 for adsorbed H₂.     

A Green Method to Fabricate Polyethyleneimine-Alginate Multilayer Coatings Modified Polyurethane Foam for Cu2+ Adsorption from Aqueous Solution

In this study, flexible polyurethane foam (FPUF) was modified with bio-based coatings composed of polyethylenimine (PEI) and alginate (ALG), fabricated by layer-by-layer (LbL) self-assembly. LbL self-assembled coatings modified FPUFs were studied for their potentials for removing Cu²⁺ ions from aqueous solutions by using batch adsorption technique, as a function of assembled bilayers number, pH value, carrier amount and adsorption time. The maximum adsorption capacity of the modified FPUF was shown to be 54 mg/g for Cu²⁺. Results suggested that the LbL self-assembly could potentially be a promising cost-effective technique for fabricating advanced adsorbent materials for removing pollutants from wastewater.     

Selective chromogenic and fluorogenic signalling of Hg ions using a fluorescein-coumarin conjugate

A novel, Hg²⁺-selective chemosensor was prepared via Mannich reaction of dichlorofluorescein with piperazinyl-coumarin moiety. The dichlorofluorescein–coumarin derivative exhibited well-defined Hg²⁺-selective chromogenic behavior, indicated by a green to pink colour change in solution, as well as fluorogenic signalling. Significant changes in fluorescence of the dichlorofluorescein subunit were analyzed in reference to the rather constant coumarin emission as an internal standard yielding Hg²⁺ selectivity. The Hg²⁺ selectivity of the chemosensor was not appreciably affected by the presence of common coexisting alkali, alkaline earth, and transition metal ions. The detection limit of the dichlorofluorescein–coumarin conjugate for the determination of Hg²⁺ ions was 4.3 × 10⁻⁶ mol L⁻¹ and the conjugate dye could be used as a chemosensor for the analysis of Hg²⁺ ions in aqueous environments.     

Spectroscopic and Thermodynamic Analysis of Cd2+ Ion Sorption Kinetics by Manganese Dioxide in the Presence of Oxyanions

The present study reports the effect of contact time, nature of electrolyte, and temperature on the sorption kinetics of Cd²⁺ by manganese dioxide, which is the most active oxide in soils and sediments. The sorption kinetics of Cd²⁺ by manganese dioxide is evaluated at pH 6 in different electrolytes in the temperatures range 293-323 K. The solid samples are equilibrated in 0.45 mmol.L^?1 Cd²⁺ and different electrolytes at pH 6. The results indicate that sorption of Cd²⁺ increases with time and temperature and the system attains equilibrium within 60 min in KNO₃ as the electrolyte. However, in the presence of 0.001 M KH2PO₄ sorption of Cd²⁺ increases and the time for equilibrium shifts to 90 min. The data second-order kinetics model and the calculated rate constant k and initial sorption rate h increases with increasing temperature phosphate treatment. Among the calculated thermodynamic activation parameters the positive values of ΔH^? and ΔG^? show the sorption process to be endothermic and nonspontaneous, while the ΔS^? being negative indicates a decrease in randomness of the system during sorption process at the solid-liquid interface. The free energy of activation decreases from 15.95 kJ.mol^?1 in nitrate to 8.76 kJ.mol^?1 in phosphate. These observations suggest that the rate controlling step in Cd²⁺ sorption is diffusionally controlled, a fact that has been proved by application of Fick’s law.     

Toward Facile Preparation and Design of Mulberry-Shaped Poly(2-methylaniline)-Ce2(WO4)3@CNT Nanocomposite and Its Application for Electrochemical Cd2+ Ion Detection for Environment Remediation

Novel hybrid material was prepared by adding slurries of poly(N-methylaniline) and cerium tungstate [Ce₂(WO₄)₃] into a conical flask contained dispersed carbon nanotubes. It was characterized by scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Electrical conductivity of poly(N-methylaniline)-Ce₂(WO₄)₃@carbon nanotube samples was determined using four-probe method. The thin layer of poly(N-methylaniline)-Ce₂(WO₄)₃@carbon nanotube was fabricated onto glassy carbon electrode for a selective Cd²⁺ ion sensor. The calibration plot is linear (r²?=?0.9917) over the large Cd²⁺ concentration ranges (1.0?nM–1.0?mM). The sensitivity, detection limit is ～5.138?µA?µM^?1?cm^?2 and ～0.11?nM (signal-to-noise ratio, at a SNR of 3), respectively.     

Functionalized magnetic core-shell Fe3O4@SiO2 nanoparticles as selectivity-enhanced chemosensor for Hg(II)

A colorimetric and ‘‘turn-on” fluorescent chemosensor Rho-Fe₃O₄@SiO₂ for Hg²⁺ in which N-(rhodamine-6G)lactam-ethylenediamine (Rho-en) is conjugated with the magnetic core-shell Fe₃O₄@SiO₂ NPs has been strategically designed and synthesized. The final product was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and UV-visible absorption and fluorescence emission. Fluorescence and UV-visible spectra results showed that the resultant multifunctional nanoparticles Rho-Fe₃O₄@SiO₂ exhibited selective ‘turn-on’ type fluorescent enhancements and distinct color changes with Hg²⁺. The selectivity of the Rho-Fe₃O₄@SiO₂ for Hg(II) ion is better than that of the Rho-en in the same conditions. In addition, the presence of magnetic Fe₃O₄ nanoparticles in the sensor Rho-Fe₃O₄@SiO₂ NPs would also facilitate the magnetic separation of the Hg(II)-Rho-Fe₃O₄@SiO₂ from the solution.     

A Novel Highly Copper(ll)-selective Chelating Ion Exchanger Based on Poly(Glycidyl Methacrylate-coethylene Dimethacrylate) Beads Modified with Aspartic Acid Derivative

Abstract

Anchoring the hydroxyaspartic acid onto poly(glycidyl methacrylate-co-ethylene dimethacrylate) (poly(GMA-co-EDMA)) beads or epoxysuccinic acid onto ammoniummodified poly(GMA-co-EDMA) beads resulted in a novel chelating resin, which contained up to 0.37 mmol of the ligand per gram of resin. Batch extraction experiments showed a very high selectivity for Cu²⁺ over Zn²⁺ and Cd²⁺ ions in buffered solutions under competitive conditions.     

Equilibrium,kinetic, and thermodynamic studies of the Ca2+ and Mg2+ ions removal from water by Duolite C206A

The uptake of Ca²⁺ and Mg²⁺ ions from synthetic aqueous solutions by Duolite C206A was studied in static-batch mode. Results revealed that there is no need of pH adjustment. The equilibrium is reached after 30 min with 0.5 g of resin at 25°C. Equilibrium data were well fitted by Langmuir isotherm model. Maximum uptake capacities Q_max were about 23.04 mg Mg²⁺/g and 64.10 mg Ca²⁺/g. The pseudo-second-order model was found as the best to explain the ions exchange kinetics effectively. The uptake of Ca²⁺ and Mg²⁺ ions by Duolite C206A is exothermic and the process is spontaneous.