Ethylenediaminetetraacetic Acid Complex Research Articles

Enhancement of antibacterial activity by a copper(II) and zinc(II) in chelation with ethylenediaminetetra-acetic acid and urea complex

Enhancement of antibacterial activity by a copper(II) and zinc(II) in chelation with ethylenediaminetetra-acetic acid and urea complex

From the Free Ligand to the Transition Metal Complex: FeEDTA- Formation Seen at Ligand K-Edges.

Chelating agents are an integral part of transition metal complex chemistry with broad biological and industrial relevance. The hexadentate chelating agent ethylenediaminetetraacetic acid (EDTA) has the capability to bind to metal ions at its two nitrogen and four of its carboxylate oxygen sites. We use resonant inelastic X-ray scattering at the 1s absorption edge of the aforementioned elements in EDTA and the iron(III)-EDTA complex to investigate the impact of the metal–ligand bond formation on the electronic structure of EDTA. Frontier orbital distortions, occupation changes, and energy shifts through metal–ligand bond formation are probed through distinct spectroscopic signatures.

Effect of EDTA Complexation on the Kinetics and Thermodynamics of Uranium Redox Reactions Catalyzed by Pyrite: A Combined Electrochemical and Quantum-Mechanical Approach

Ethylenediaminetetraacetic acid (EDTA), a strong complexing agent, is a common constituent of liquid nuclear waste streams. The interaction of EDTA or other organic or inorganic ligands with uranyl enhances the mobilization of uranium and therefore significantly influences the disposal and remediation of uranium waste. Although numerous studies have focused on the effect of EDTA on the mobilization of environmental uranium, including the adsorption and redox reactions of uranium on mineral surfaces, few studies have differentiated the reaction-controlling steps (diffusion, adsorption, and chemical reaction/electron transfer) occurring at heterogeneous interfaces to assess the effect of EDTA complexation on each of these processes. Here, a combination of in situ electrochemical methods and quantum-mechanical calculations was used to study the effect of EDTA complexation on the kinetics and thermodynamics of redox reactions of uranium at the pyrite-solution interface. Experiments indicate a potential shift of U(VI)/U(V) on the pyrite surface of ∼0.04 V due to surface adsorption and −0.21 V due to EDTA complexation, with similar results from the calculations. The oxidation of the U(IV) reaction is more sensitive to EDTA complexation in solution than that of U(V). Disproportionation, affecting 2/3 of the intermediate pentavalent state, is the rate-limiting step of the overall redox cycle of uranyl. The charge transfer was controlled by diffusion and adsorption processes. EDTA can promote the delivery of free uranyl from the bulk solution to the pyrite–water interface where the reaction takes place, making the electron-transfer process less diffusion-limited. Adsorption of uranyl onto pyrite surfaces in the gradient electric field is multimolecular layer adsorption, through which electron transfer can occur.

Intense removal of Ni (Ⅱ) chelated by EDTA from wastewater via Fe3+ replacement–chelating precipitation

Efficient removal of Ni (Ⅱ) chelated by ethylenediaminetetraacetic acid (EDTA) from wastewater remains an important but challenging environmental problem. Therefore, a novel strategy of Fe3+ replacement–chelating precipitation was proposed to remove Ni (Ⅱ) chelated by EDTA from simulated Ni-EDTA wastewater and real electroless nickel plating wastewater. The strategy was proved to be thermodynamically feasible by DFT calculation. Regardless of the simulated Ni-EDTA wastewater or the real electroless nickel plating wastewater, the residual nickel in the wastewater was less than 0.1 mg/L that satisfied the discharge standard after being treated under optimal conditions using this strategy. Moreover, the strong acidity and Fe3+ could increase the proportion of free Ni2+ in Ni-EDTA wastewater, thereby enhancing the Ni removal efficiency. Additionally, the total amount of EDTA in wastewater was basically unchanged, since the structure of EDTA was not destroyed by this strategy, while its chemical form changed from Ni-EDTA complex to Fe3+-EDTA complex. Furthermore, the mechanism was systematically studied by electronic structure analysis, solution chemistry, UV-Vis spectral, FT-IR spectral and X-ray photoelectron spectroscopy. At last, this strategy is a promising approach and it can provide a reference for the treatment of other similar heavy metal wastewater.

Separation of lithium, nickel, manganese, and cobalt from waste lithium-ion batteries using electrodialysis

With the expansion of lithium-ion battery market and the awareness of environmental protection, the development of green and sustainable technologies to recycle waste lithium-ion batteries has become urgent. Electrodialysis is an emerging green process to recover valuable metals from postconsumer lithium-ion batteries. This study focuses on the separation and recovery of lithium, nickel, manganese, and cobalt from LiNi0.33Mn0.33Co0.33O2 chemistry of lithium-ion batteries using electrodialysis. Prior to the electrodialysis experiment, complexation of ethylenediaminetetraacetic acid (EDTA) with four different metals is assessed using ultraviolet-visible spectroscopy. Using the developed three-stage electrodialysis process, 99.3% of nickel is separated in stage 1 and 87.3% of cobalt is then separated in stage 2 using electrodialysis coupled with EDTA. About 99% of lithium is sequentially separated from manganese in stage 3 using electrodialysis with a monovalent cation-exchange membrane. After the electrodialysis experiment, nickel and cobalt are decomplexed from EDTA at pH below 0.5 and all four metals are recovered with high purity of >99%. Electrodialysis offers a new route to recycle lithium-ion batteries with twofold benefits of providing a secondary source for strategic materials and reducing the number of lithium-ion batteries that are landfilled after they reach their end of life.

Quantitative extraction of chromium VI and III from tanned leather: a comparative study of pretreatment methods

In this study, seven pretreatment methods for chromium speciation in tanned leather were evaluated: acidic mineralization, ethylenediaminetetraacetic acid (EDTA) extraction, diethylenetriaminepentaacetic acid (DTPA) extraction, alkaline extraction (NH4OH), ammonium nitrate extraction (NH4NO3), water extraction, and phosphate buffer extraction. Acidic mineralization permitted the decomposition of the organic matter and ensured the complete digestion of leathers, giving access to the total content of chromium in each sample using inductively coupled plasma-atomic emission spectrometry (ICP-AES). From all the extractant media tested, EDTA proved to be the most efficient, allowing the extraction of Cr(VI) and Cr(III) as a Cr(III)-EDTA complex, quantitatively. Method validation is presented for EDTA extraction and direct mineralization. For the EDTA extraction, method detection limit (MDL) and method quantification limit (MQL) for total Cr in leather were 3.4 ppb and 11.2 ppb (µg of total Cr per L of extraction solution), respectively. Due to the lack of leather certified reference materials (CRMs) for Cr(VI), accuracy was evaluated by spiking leather samples with a Cr(VI) solution. The spike recovery of EDTA microwave assisted extraction ranged from 91.0 to 108.6%. Interday precision was also evaluated and all variation coefficients were below 5%, for both mineralization and EDTA extraction. This article provides an efficient procedure to extract quantitatively chromium from leather, while maintaining the speciation, which can be further followed by ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS).

Development of an Immunoassay for the Detection of Copper Residues in Pork Tissues.

The presence of high concentrations of copper (Cu) residues in pork is highly concerning and therefore, this study was designed to develop a high-throughput immunoassay for the detection of such residues in edible pork tissues. The Cu content in the pork samples after digestion with HNO3 and H2O2 was measured using a monoclonal antibody (mAb) against a Cu (II)–ethylenediaminetetraacetic acid (EDTA) complex. The resulting solution was neutralized using NaOH at pH 7 and the free metal ions in the solution were chelated with EDTA for the immunoassay detection. An indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) method was developed for Cu ion analysis. The half maximal inhibitory concentration of the mAb against Cu (II)–EDTA was 5.36 ng/mL, the linear detection range varied between 1.30 and 27.0 ng/mL, the limit of detection (LOD) was 0.43 μg/kg, and the limit of quantification (LOQ) was 1.42 μg/kg. The performances of the immunoassay were evaluated using fortified pig serum, liver, and pork samples and had a recovery rate of 94.53–102.24%. Importantly, the proposed immunoassay was compared with inductively coupled plasma mass spectroscopy (ICP-MS) to measure its performance. The detection correlation coefficients of the three types of samples (serum, pork, and liver) were 0.967, 0.976, and 0.983, respectively. Thirty pork samples and six pig liver samples were collected from local markets and Cu was detected with the proposed ic-ELISA. The Cu content was found to be 37.31~85.36 μg/kg in pork samples and 1.04–1.9 mg/kg in liver samples. Furthermore, we detected the Cu content in pigs with feed supplemented with tribasic copper chloride (TBCC) and copper sulfate (CS) (60, 110, and 210 mg/kg in feed). There was no significant difference in Cu accumulation in pork tissues between the TBCC and CS groups, while a remarkable Cu accumulation was found for the CS group in liver at 210 mg/kg, representing more than a two-fold higher level than seen in the TBCC group. Therefore, the proposed immunoassay was found to be robust and sensitive for the detection of Cu, providing a cost effective and practical tool for its detection in food and other complicated samples.

Fragmentation behavior of EDTA complexes under different activation conditions.

Ethylenediaminetetraacetic acid (EDTA) is an aminopolycarboxylic acid and complexation agent that is able to bind a large variety of metals. The formation of highly stable metal-EDTA complexes is generally very quick. This has led to the use of EDTA in a variety of applications, including food, medical, and household applications. In the current study, we have investigated the fragmentation behavior of EDTA and various metal complexes under collision-induced dissociation (CID), infrared-multiphoton dissociation (IRMPD), and higher-energy collisional dissociation (HCD) activation conditions. Both, positive and negative mode electrospray ionization (ESI) were applied. The metals used to complex with EDTA ranged from alkaline earth metals, such as sodium and cesium, via calcium, nickel, zinc, aluminum, copper, iron, and indium to yttrium and several lanthanides. Furthermore, the protonated and deprotonated species of EDTA, as well as disodium and trisodium species, have been subjected to fragmentation. The results show that characteristic fragmentations were obtained for EDTA and the metal complexes under the investigated conditions. The use of an ion cyclotron resonance (ICR) and an Orbitrap mass spectrometer, as high resolution-accurate mass instruments, allowed the assignment of elemental compositions undoubtedly for the vast majority of fragments. Certain trends were observed that trend correlated with the size of the metal and the location within the periodic table.

Solution structure of a europium-nicotianamine complex supports that phytosiderophores bind lanthanides.

We report the solution structure of a europium-nicotianamine complex predicted from ab initio molecular dynamics simulations with density functional theory. Emission and excitation spectroscopy show that the Eu3+ coordination environment changes in the presence of nicotianamine, suggesting complex formation, such as what is seen for the Eu3+-nicotianamine complex structure predicted from computation. We modeled Eu3+-ligand complexes with explicit water molecules in periodic boxes, effectively simulating the solution phase. Our simulations consider possible chemical events (e.g. coordination bond formation, protonation state changes, charge transfers), as well as ligand flexibility and solvent rearrangements. Our computational approach correctly predicts the solution structure of a Eu3+-ethylenediaminetetraacetic acid complex within 0.05 Å of experimentally measured values, backing the fidelity of the predicted solution structure of the Eu3+-nicotianamine complex. Emission and excitation spectroscopy measurements were also performed on the well-known Eu3+-ethylenediaminetetraacetic acid complex to validate our experimental methods. The electronic structure of the Eu3+-nicotianamine complex is analyzed to describe the complexes in greater detail. Nicotianamine is a metabolic precursor of, and structurally very similar to, phytosiderophores, which are responsible for the uptake of metals in plants. Although knowledge that nicotianamine binds europium does not determine how plants uptake rare earths from the environment, it strongly supports that phytosiderophores bind lanthanides.

Cu(II)-EDTA removal by a two-step Fe(0) electrocoagulation in near natural water: Sequent transformation and oxidation of EDTA complexes

The widely usage of ethylenediaminetetraacetic acid (EDTA) arises environmental concerns on toxic metal mobilization, and challenges the conventional processes in water treatment. In the study Cu(II)-EDTA in near natural water was efficiently removed during a two-step electrocoagulation using Fe(0) anode (Fe-EC), including a transformation to Fe(III)-EDTA induced mainly by structural Fe(II) in anoxic Fe-EC and further degradation in oxic Fe-EC. The degradation of Fe(III)-EDTA was mostly attributed to an oxygen activation mechanism that involving O2− and hydroxyl radical (OH) generation, as validated by the quenching experiments and electron spin resonance. Furthermore, O2− generated during Fe(II) oxidation took a dominant role on Fe(III)/Fe(II)-EDTA transformation instead of electrochemical reduction. Six intermediates during the Fe(III)-EDTA degradation were identified by LC-Q-TOF, indicating a pathway of stepwise breakage of NC bonds. The results revealed in this work is helpful to understand the contribution and fate of EDTA during Fe-EC treatment of metal-EDTA polluted water.

Selective leaching of lead from lead smelter residues using EDTA.

Ethylenediaminetetraacetic acid (EDTA) has been widely used as an effective reagent for removal of lead from soil because of its high lead extraction efficiency caused by the high thermodynamic stability of the Pb(ii)–EDTA complex. In this study, EDTA was used as a lixiviant for recovery of lead from residues (matte and slag) of secondary lead smelter plants. The residues were composed mainly of iron (34–66 wt%) and lead (7–11 wt%). Leaching parameters (EDTA concentration, pH, temperature, liquid-to-solid ratio and leaching time) were optimized. The optimum leaching efficiency was achieved when leached for 1 h at room temperature using 0.05 mol L−1 EDTA at a liquid-to-solid ratio of 5 mL g−1. At such conditions, 72 to 80% of lead and less than 1% of iron were leached from both matte and slag. The high selectivity towards lead with minimal co-dissolution of iron is a major advantage since it reduces the chemical consumption and simplifies the downstream processes. Although the stability constants of the complexes Fe(iii)–EDTA, Fe(ii)–EDTA and Pb–EDTA are all large (log KS 25.1, 14.33 and 18.04, respectively), the leaching of iron was most likely limited by its presence in insoluble phases such as iron oxides, sulfides and silicates in the residues. 100% leaching of lead was achieved by a multi-step leaching process where the leaching residues were contacted three times by a fresh EDTA solution. To recover EDTA, first iron was precipitated as iron hydroxide by raising the pH of pregnant leach solution (PLS) above 12.6 using sodium hydroxide, followed by precipitation of lead as lead sulfide by adding ammonium sulfide. The recovered EDTA was successfully reused two times for leaching without significant changes in leaching yields.

Enhanced cathodic catalytic activity of an N-doped micropore structure obtained through the six-coordinate bond of an EDTA-Ce composite for the oxygen reduction reaction

The development of catalytic materials to increase the efficiency of the oxygen reduction reaction (ORR), which effects an important role in next generation energy storage and conversion systems, is essential but challenging. Electrocatalysts for ORR in alkaline solution, including Ce/N-doped micropore carbon materials (CNMCs), are prepared as nonprecious-metal catalysts from an ethylenediaminetetraacetic acid (EDTA) and cerium (III) nitrate hexahydrate complex. The material obtained via a simple manual synthesis method has a microporous and octahedral structure as a result of six-coordinate bonds between EDTA and Ce metals. The CNMC materials have high surface areas, which advantageous for electrochemical catalysts. Furthermore, the micropore structure positively affects the ORR by allowing three phases (solid/catalyst–liquid/electrolyte–gas/oxygen) to coexist in a wide range. Ultimately, a new cathodic catalyst based on EDTA, which has not been reported thus far, is obtained after the optimal Ce content is determined. The electrocatalytic performance of CNMCs toward the ORR is characterized using a rotating disk electrode (RDE) technique. The RDE results obtained with the CNMCs reveal an onset-potential and half-wave potential similar to those of a Pt/C catalyst. In addition, the CNMCs exhibit good long-term stability and excellent durability. Therefore, these materials may be alternative cathode electrocatalysts in commercial use.

Effects of substrate temperature on morphology of erbia films deposited by flame spraying using metal–ethylenediaminetetraacetic acid complex

The effects of the substrate temperature on the morphology of erbia films synthesized from a metal–ethylenediaminetetraacetic acid complex using flame spraying were evaluated. To begin with, we focused on the effect of substrate preheating on the thermal conductivity of the substrates. The morphology of the Er2O3 splats formed on various substrates (S50C and SUS304) preheated/precooled to different temperatures was investigated. The types of splats formed depended on the substrate used and its preheating/precooling temperature. The ratio of the disc-like splats on S50C (29–68%) and SUS304 (36–86%) increased with an increase in the preheating temperature between 0 and 100 °C. The wettabilities of different substrates (S50C, SUS304, Al–Mg alloy, and quartz) were also evaluated. Fourier transform infrared spectroscopy and thermogravimetry/differential thermal analysis measurements reveled that, ideally, deposition should be performed when no surface-adsorbed water is present on the substrate surface. Thus, it can be concluded that substrate preheating aids the deposition of erbia films synthesized from a metal–EDTA complex through flame spraying and that preheating is especially effective in the case of S50C substrates.

Decomposition of Nickel(Ⅱ)−Ethylenediaminetetraacetic acid by Fenton−Like reaction over oxygen vacancies-based Cu−Doped Fe3O4@γ−Al2O3 catalyst: A synergy of oxidation and adsorption

Nickel (Ⅱ)−ethylenediaminetetraacetic acid (Ni−EDTA) complexes are widely present in electroplating effluents. Owing to its chemical stability, Ni−EDTA is hardly removed in traditional Fenton/Fenton-like processes with conventional iron (Fe)−based catalyst. In this study, oxygen vacancies were introduced into our highly efficient and novel Fe3O4@γ−Al2O3 catalysts using Cu doping for Ni−EDTA decomposition in Fenton−like system. Without noble−metal cocatalyst, the introduction of oxygen vacancies in Cu−doped Fe3O4@γ−Al2O3 catalysts exhibit excellent Fenton−like activity even in neutral or alkaline conditions. Experimental results revealed that, without the aid of extra energy, Ni−EDTA complexes could be effectively decomposed over oxygen vacancies−based catalyst. Electron paramagnetic resonance (EPR), X−ray photoelectron spectroscopy (XPS), oxygen temperature−programmed desorption (O2−TPD), and hydrogen temperature−programmed reduction (H2−TPR) were used to get a deep insight into the decomposition mechanism. Additionally, by employing the Al−containing support, stable layered double−hydroxide phases of NiAl could be formed, indicating that a synergy of oxidation and adsorption could simultaneously take place, which led to the recovery of released Ni2+ ions and also reduction in secondary pollution. To investigate the decomposition process of Ni−EDTA over oxygen vacancies−based catalyst, liquid chromatography−quadrupole/electrostatic field orbitrap high resolution mass spectrometry (LC−MS/MS) was employed to identify the generated intermediates, and thus, a plausible decomposition pathway was successfully conceived.

Formation of Cobalt-BTA Complexes and Their Removal from Various Surfaces Relevant to Cobalt Interconnect Applications

The use of benzotriazole (BTA) during Co film planarization leads to the undesirable formation of insoluble Co-BTA complexes, which can be observed as organic residues on various surfaces after polishing. Here, we investigated the formation of Co-BTA complexes at different pH values and their adsorption and removal from Co, TiN, SiN, and SiO2 film surfaces relevant to Co interconnect applications. The stability constant, log Keq, of Co2+-BTA complex was determined from its spectroscopic properties and log Keq was found to lie between 2.7 and 3.9 in the pH range of 6 ∼ 12, much smaller than that of Co3+-ethylenediaminetetraacetic acid (EDTA) complexes (log Keq = 36.0). Using this data, and recognizing that potassium persulfate (K2S2O8) and EDTA can lead to oxidation and ligand exchange of Co2+-BTA complexes, respectively, we were able to remove Co-BTA complexes adsorbed on all films by exposing them to aqueous solutions of 50 mM EDTA, 1.5 wt% K2S2O8, and 1 mM sodium dodecylbenzenesulfonate (SDBS) at pH 12. SDBS was helpful in lowering ΔEcorr to about 10 mV for the Co/TiN couple as well as the corrosion currents of Co film.

Facile synthesis of monodispersed copper oxalate flaky particles in the presence of EDTA

Monodispersed copper oxalate particles with flaky morphology were prepared via a simple one-pot synthesis method. Scanning electron microscope (SEM), X-ray diffraction (XRD), and fourier transform infrared (FTIR) spectra were used to characterize particle morphology, size, phase composition, and functional groups. It was found that the presence of ethylenediaminetetraacetic acid (EDTA) and the solution pH value had strong influence on the morphological and size evolution of the precipitated particles. On the basis of controlled release of copper ions from a Cu2+–EDTA complex and Weimarn’s law, a strategy for the controlled synthesis of monodispersed copper oxalate particles was designed by referring to the basic mode of the Stober method. The inherent nature of crystallization to form the flaky solid in the early stage of precipitation as well as the driving force of the long-lasting low supersaturation in the growth stage was proposed to explain the size and morphological evolution of the copper oxalate precipitates. Thermodynamic equilibrium concentrations of copper(II) species in the Cu(II)–EDTA–oxalate–H2O solution system were calculated to help explain the possible formation mechanism of copper oxalate precipitates.

A Study on influence of organic ligands on migration of heavy metals through compacted clayey soil

This paper presents the feasibility study on utilization of locally available clayey soil as Compacted Clay Liner based on its contaminant migration capacity under the presence of organic chemical EDTA (Ethylene Diamine Tetra acetic Acid) which is abundantly released into the environment. Lead, Nickel, cadmium and chromium ions was selected as contaminants and its migration properties are assessed by conducting column studies with a single and multiple heavy metal solution with the EDTA. From the experimental investigations, it is revealed that with the presence of EDTA, the contaminant breakthrough time get reduced due to soluble metal – EDTA complex formation. At pH 2, interaction with multi metal, the mobility was increased and the order of mobility was observed as Cr > Cd > Ni > Pb. With the presence of EDTA in multi metal system at pH 2, the order of the mobility was Cr > Ni > Cd > Pb and at pH 7 the mobility of heavy metals were increased the order was Cr > NI > Pb > Cd. This study reveals that locally available clayey soil is capable of retaining heavy metals and it may be used as a compacted clay liner, where organic chemical like (EDTA) ingression is present.

Controlled Synthesis of Cu and Cu₂O NPs and Incorporation of Octahedral Cu₂O NPs in Cellulose II Films.

In this study, Cu and Cu2O nanoparticles (NPs) were synthesized through chemical reduction of soluble copper-chelating ligand complexes using formaldehyde as a reducing agent. The influence of various chelating ligands, such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and a surface-active derivative of DTPA (C12-DTPA), as well as surfactants (i.e., hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium chloride (DoTAC), sodium dodecyl sulfate (SDS), and dimethyldodecylamine-N-oxide (DDAO)), on morphology and the composition of produced NPs was investigated. In the absence of surfactants, spherical copper particles with polycrystalline structure could be obtained. X-ray diffraction (XRD) analysis revealed that, in the presence of EDTA, the synthesized NPs are mainly composed of Cu with a crystallite size on the order of 35 nm, while with DTPA and C12-DTPA, Cu2O is also present in the NPs as a minority phase. The addition of ionic surfactants to the copper–EDTA complex solution before reduction resulted in smaller spherical particles, mainly composed of Cu. However, when DDAO was added, pure Cu2O nano-octahedrons were formed, as verified by high-resolution scanning electron microscopy (HR-SEM) and XRD. Furthermore, a hybrid material could be successfully prepared by mixing the octahedral Cu2O NPs with cellulose dissolved in a LiOH/urea solvent system, followed by spin-coating on silica wafers. It is expected that this simple and scalable route to prepare hybrid materials could be applied to a variety of possible applications.

Molecularly imprinted sensor based on Russian Matryoshka structured molecules for enhanced specific identification and double amplification in ultra-trace Tb3+ determination

The selective and sensitive detection of rare earth elements is thought to be difficult because the concentration of those elements in the sample is commonly at a low level and they normally have severe mutual interference which is caused by homologous chemical properties. In this study, a novel molecularly imprinted polymer (MIP) sensor was fabricated for highly sensitive and selective determination of ultra-trace Tb3+. The Tb3+-ethylenediaminetetraacetic acid complex (Tb-EDTA) as the template molecule was incorporated into mono-6-mercapto-β-cyclodextrin (mono-6-SH-β-CD) to form a Russian Matryoshka (RM)-structured molecule (CD/Tb-EDTA). Titanium isopropoxide was utilized in vapor sol–gel polymerization to construct MIP membrane. Moreover, the selectivity of the RM MIP sensor was remarkably enhanced by the “triple-selectivity” recognition of EDTA-to-Tb3+, β-CD-to-(Tb-EDTA), and 3D cavity-to-(CD/Tb-EDTA), while the sensitivity of the MIP sensor was significantly improved by ECL signal enhancement based on double amplification, in other words, the electrochemiluminescence resonance energy transfer (ECL-RET) between the ECL donor of CD/Tb-EDTA and the ECL acceptor of Ru(bpy)32+, and the ECL enhancement by the co-reactant of CD/Tb-EDTA on Ru(bpy)3Cl2. When the imprinted cavities were occupied by Tb-EDTA during rebinding, the host-guest inclusion structured complex was formed and the ECL intensities produced by the Ru(bpy)3Cl2 ECL system increased with increasing concentration of Tb-EDTA. The proposed sensor was used for quantitative analysis of Tb3+ with concentrations ranging from 8.00 × 10–13 mol/L to 4.00 × 10–9 mol/L and successfully applied to detect Tb3+ in seawater samples. The detection limit of the sensor was found to be 3.90 × 10–13 mol/L (DL = 3δb/K), which is lower than previously reported values. Thus, the fabricated sensor is feasible for practical applications.

Synthesis of SrFe12O19 magnetic nanoparticles by EDTA complex method

A modified polyacrylamide gel route was used to prepare SrFe12O19 magnetic nanoparticles; ethylenediaminetetraacetic acid (EDTA) was used as a carboxyl chelating agent. The phase purity, morphology and magnetic properties of as-prepared samples were analyzed via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometery (VSM). XRD analysis indicates that high-purity SrFe12O19 magnetic nanoparticles can be synthesized at 700°C in air. The characteristic peaks of as-prepared sample at 210, 283, 321, 340, 381, 411, 432, 475, 532, 618, 686, and 726 cm–1 were observed in Raman spectra. SEM and TEM show that the synthesized SrFe12O19 magnetic nanoparticles are uniform with the mean particle size of ~60 nm. VSM measurement shows that the maximum magnetic energy product (BH)max of sample prepared using EDTA as a chelating agent is higher than that of sample prepared using citric acid as a chelating agent.