Single precursor-based luminescent nitrogen-doped carbon dots and their application for iron (III) sensing

Iron III (Fe³⁺) sensing is of great importance for monitoring its levels in different environmental and biological systems since its levels are tightly associated with many environmental concerns and serious diseases. Compared to the ordinary Fe³⁺ detection methods involving the sophisticated and expensive instruments, the use of fluorescent materials with short response time and low cost attracts much attention. Amongst a variety of fluorescent materials, a nitrogen-doped carbon dot (N-CD) is emerging as promising luminescent materials for biosensing due to their superior photoluminescent properties, good water solubility, and biocompatibility. Herein, N-CD prepared via a green and cost-effective one-pot hydrothermal method using a new single precursor N-(2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA) as both the carbon and nitrogen sources is reported. The blue fluorescent emission of N-CDs is quenched by the addition of Fe³⁺, and the quenching intensity is concentration dependent in the wide range (0.76–400 μM) with a detection limit of 0.16 μM. The quantum yield for the as prepared N-CDs is 14.17%. The N-CDs also show a high selectivity for Fe³⁺ chelation amongst a range of biological metal ions. The fluorescent quenching is attributed to the formation of the coordinate covalent bonds between the Fe³⁺ and N-CDs, and the mechanism is proved to be a static type on the basis of the photoluminescence lifetime and the temperature-dependent fluorescent intensity change. Our eco-friendly and simple strategy will benefit the application of CDs in various fields.     

The Displacement of Sr from Organic Chelates by Hydroxide, Carbonate, and Calcium in Concentrated Electrolytes

The effects of calcium, hydroxide, and carbonate on the displacement of Sr from four organic chelates: ethylenedinitrilotetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid (HEDTA) nitrilotriacetic acid (NTA), and iminidiacetic acid (IDA) was studied in solutions with high base and carbonate concentration. Comparison of solutions with and without added chelators allowed the speciation changes in solution to be directly determined. Increases in both carbonate and calcium concentration were effective in displacing Sr from the chelators even under high carbonate concentration. Increases in hydroxide were ineffective in removal of Sr from the chelators, even at base concentrations as high as 6M. Under certain specific conditions, most notably when both CaCO₃(s) and SrCO₃(s) are present in solution, chemical equilibrium constraints result in cancelation of activity coefficient changes for aqueous Sr and Ca organic chelate complexes. Under such conditions the predicted ratios of chelated Ca and Sr become independent of the ionic media and predictive relations using known equilibrium constants give very good representations of the experimental data. These results indicate that manipulation of metal ion displacement reactions during chemical processing of Sr–chelate solutions can result in the displacement of Sr from organic chelators. The implications of such strategies in processing high level waste supernatants stored at Department of Energy (DOE) sites is discussed.     

HEDTA-H_3Cit体系阳离子交换色层法分离镱和镥的研究

用N-羟乙基乙二胺-N,N′,N′-三乙酸(HEDTA)-柠檬酸(H3Cit)体系作淋洗剂,阳离子交换色层法分离Yb,Lu。通过红外光谱分析和电位滴定法确定Yb-HEDTA-H3Cit三元配合物的形成;研究室温条件下HEDTA-H3Cit体系淋洗剂对Yb,Lu分离的效果,通过ICP-AES测定洗脱液中稀土离子的浓度,绘制淋洗曲线,根据曲线中交叉区洗脱液体积占含稀土离子总洗脱液体积的比例衡量分离效果。结果表明,用HEDTA-H3Cit体系淋洗剂分离Yb,Lu,当HEDTA与H3Cit摩尔比为1∶1时,比HEDTA淋洗剂具有更好的分离效果和更短的淋洗周期。     

希土-HEDTA-蛋氨酸三元配合物研究

用pH电位法测定了希土与N-羟乙基乙二胺三乙酸(HEDTA)、蛋氨酸(Met)三元配合物在25℃和0.15mol/L(NaCl)离子强度下的稳定常数。以荧光光谱法研究了TbCl_3、Tb-Met、Tb-HEDTA以及Tb-HEDTA-Met体系,Tb~(3+)的三元配合物发射被两个配体同时敏化的Tb~(3+)特征荧光。讨论了三元体系中的配位作用以及能量传递特点。     

Hydrazinium metal(II) and metal(III) ethylenediamine tetraacetate hydrates

Hydrazinium metal ethylenediaminetetraacetate complexes of molecular formula (N₂H₅)₂[Mg(edta)·H₂O], (N₂H₅)₃[Mn(edta)··H₂O](NO₃)·H₂O, N₂H₅[Fe(edta)·H₂O], N₂H₅[Cu(Hedta)·H₂O] and N₂H₅[Cd(Hedta)·H₂O]·H₂O have been synthesized and characterized by elemental and chemical analysis, conductivity and magnetic measurements and spectroscopic techniques. The thermal behaviour of these complexes has been studied by thermogravimetry and differential thermal analysis. The data set provided by the simultaneous TG-DTA curves of the complexes shows the occurrence of three or four consecutive steps such as dehydration, ligand pyrolysis and formation of metal oxides. X-ray powder diffraction patterns of copper and cadmium complexes show that they are not isomorphous. These studies suggest seven coordination for Mg,Mn, Fe complexes and six coordination for Cu and Cd derivatives.     

An Aqueous Thermodynamic Model for the Complexation of Sodium and Strontium with Organic Chelators Valid to High Ionic Strength. II. N-(2-Hydroxyethyl)ethylenedinitrilotriacetic Acid (HEDTA)

This is the second paper in a two part series on the development of aqueous thermodynamic models for the complexation of Na⁺ and Sr²⁺ with organic chelators. In this paper, the development of an aqueous thermodynamic model describing the effects of ionic strength, carbonate concentration, and temperature on the complexation of Sr²⁺ by HEDTA under basic conditions is presented. The thermodynamic model describing the Na⁺ interactions with the HEDTA^3–chelate relies solely on the use of Pitzer ion-interaction parameters. The exclusive use of Pitzer ion-interaction parameters differs significantly from our previous model for EDTA, which required the introduction of a NaEDTA^3– ion pair. Estimation of the Pitzer ion-interaction parameters for HEDTA^3– and SrHEDTA^– with Na⁺ allows the extrapolation of a standard-state equilibrium constant for the SrHEDTA^– species, which is one order of magnitude greater than the 0.1 M reference state value available in the literature. The overall model is developed from data available in the literature on apparent equilibrium constants for HEDTA protonation, the solubility of salts in concentrated HEDTA solutions, and from new data on the solubility of SrCO₃(c) obtained as part of this study. The predictions of the final thermodynamic model for the Na-Sr-OH-CO₃-NO₃-HEDTA-H₂O system are tested by application to chemical systems containing competing metal ions (i.e., Ca²⁺).     

EDTA-HEDTA复配络合铁体系脱H2S性能研究

配制了一种EDTA-HEDTA复配络合铁脱硫液,配方溶液组成为n(EDTA)∶n(HEDTA)∶n(Fe3+)∶n(Fe2+)=1.2∶6∶5∶1,pH=8.5。研究了进气H2S含量、温度与稳定剂对配方溶液脱硫性能和稳定性的影响。结果表明,配方溶液对H2S质量浓度35%以内的气体有良好吸收效果,脱硫率可达98%以上;随着温度升高,配方溶液脱硫率几乎不变,但穿透时间呈降低趋势;添加稳定剂Na2S2O3或苯甲酸钠可减缓络合剂的降解。硫容测试表明,配方溶液硫容为2.0g/L,具有良好的脱硫潜力。     

Configuration Reversion of the Metal Chelates of N-hydroxyethyl Ethylenediaminetriacetic Acid——Dynamic NMR Study

The intramolecular acetate rearrangement of the aminocarboxylate metal chelates with the hexdentate-coordinate has been investigated by dynamic NMR in recent years. However, the intramolecular processes of the metal quinquedentate chelates have not been studied up to now. Here is reported the configurational reversion