Chelating Interaction Research Articles

Efficient immobilization of toxic heavy metals in multi-contaminated agricultural soils by amino-functionalized hydrochar: Performance, plant responses and immobilization mechanisms

A novel amino-functionalized hydrochar material (referred to NH2–HCs) was prepared and used as the soil amendment to immobilize multi-contaminated soils for the first time. The results showed that the application of NH2–HCs significantly improved (P < 0.05) soil properties (i.e., pH value, cation exchange capacity and organic content). By introduction of NH2–HCs, the contaminated soil showed the highest value of 96.2%, 52.2% and 15.5% reductions in Cu, Pb and Cd bioavailable concentrations and the leaching toxicity of Cu, Pb and Cd were remarkably reduced by 98.1%, 31.3% and 30.4%, respectively. Most of exchangeable Cu, Pb and Cd reduced were transformed into its less available forms of oxidizable and residual fractions. Potential ecological risk assessment indicated that the element Cd accounted for the most of total risks in NH2–HCs amended soils. The mechanism study indicated that surface complexation, chemical chelating and cation-pi interaction of NH2–HCs played a vital role in the immobilization of heavy metals. Pot experiments further verified that the application of NH2–HCs significantly improved plant growth and reduced metal accumulations. The present study offered a novel approach to prepare amino-functionalized hydrochars with great potential as the green and alternative amendments for efficiently immobilizing heavy metals in multi-contaminated soil.

A derivative of mesoporous oxygen reduction reaction electrocatalysts from citric acid and dicyandiamide

It remains urgent to make continuous efforts on well-designed and highly active non-precious metal (NPM) electrocatalysts for the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), thus helping greatly reduce the fuel cell cost. Due to an unsatisfied stability caused by Fenton reaction for Fe-based materials, Co-based materials bear much more expectations as one type of NPM electrocatalysts to be applied in the ORR. Here we report a novel strategy to synthesize a series of mesoporous nitrogen-doped carbon-supported cobalt electrocatalysts (Co-DCD-CA), which takes full advantage of electrostatic interaction between carboxyl in citric acid (CA) and amidogen in dicyandiamide (DCD) as well as chelating interaction between citric acid and cobalt cation. When CA is employed as carbon source, the optimal derivative of the Co-DCD-2-CA-900 electrocatalyst exhibits a higher ORR activity with a half-wave potential at 0.75 V, which is 60 mV higher than that prepared using Ketjenblack EC 300 J (Co-DCD-2-EC-900) as the carbon support. Besides, the effects of pyrolysis temperature as well as DCD to CA ratio on the ORR activity are detailedly investigated.

A novel heat-treated humic acid/MgAl-layered double hydroxide composite for efficient removal of cadmium: Fabrication, performance and mechanisms

Heat-treated humic acid/MgAl-layered double hydroxide composite (HA/MgAl-LDH) was fabricated through a coprecipitation method and used as an adsorbent for the removal of Cd in aqueous solution. The composite was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) technique and X-ray photoelectron spectroscopy (XPS). These results indicated that the composite (HA/MgAl-LDH) had a rough surface, a large specific surface area and many functional groups. A series of experiments were conducted to ascertain the adsorption performance of HA/MgAl-LDH, including the additive amount of HA/MgAl-LDH, pH and ionic strength. The adsorption dynamics of HA/MgAl-LDH followed a pseudo-second-order model, suggesting that the process of Cd removal was chemical adsorption. Adsorption isotherms followed the Langmuir model of monolayer adsorption, and the maximum theoretical adsorption capacity calculated for Cd was 155.28 mg/g. Moreover, the adsorption mechanism of Cd was investigated by characterization and batch experimental analysis. Cd was absorbed on the surface of HA/MgAl-LDH by surface complexation and chelating interactions, and surface complexation was the main route of Cd removal. In addition, HA/MgAl-LDH has excellent treatment efficiency in actual wastewater. In short, HA/MgAl-LDH is a promising material for the removal of Cd from aqueous media because of its low cost, high efficiency, and easy operation.

Fabrication of Zr(IV) Modified Gold Electrode via Layer-by-Layer Self-Assembly for Methyl Parathion

A facile way was developed to fabricate Zr(IV) cation modified gold electrode for high-performance electrochemical sensing of methyl parathion (MP) via layer-by-layer self-assembly. The electrode was prepared by sequentially absorbing 11-mercaptoundecyl-phosphoric acid (MDPA) and Zr(IV) cation on gold electrode through strong chelating interactions between gold and -SH as well as Zr(IV) cation and phosphoric groups of MDPA. Fourier transform infrared spectrophotometry, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and cyclic voltammetry were employed for the characterization of morphologies and electrochemical properties. The sensor was used to determine MP by square wave voltammetry. The cathodic peak current (at + 0.25 V vs saturated calomel electrode) increases linearly in the range of 1.0 − 180.0 ng ml−1 under optimized conditions. And the detection limit is low to 0.22 ng ml−1 (based on a signal-to-noise ratio of 3). The electrode is successfully used to detect MP in the real water sample with recoveries of 98.97%–102.4% and RSDs of 0.21%–1.99% (n = 3) at three spiked levels. The proposed method provides one simple way to prepare Zr(IV) cation modified electrode for the fast determination of MP. The reliability and accuracy of the method is validated by independent assays with HPLC.

Two-Dimensional Titanium Carbides (Ti3C2Tx) Functionalized by Poly(m-phenylenediamine) for Efficient Adsorption and Reduction of Hexavalent Chromium.

Titanium carbides (MXenes) are promising multifunctional materials. However, the negative surface charge and layer-by-layer restacking of MXenes severely restrict their application in the field of anionic pollutants, including in hexavalent chromium (Cr(VI)). Herein, Ti3C2Tx MXenes was functionalized through in situ polymerization and intercalation of poly(m-phenylenediamine) (PmPD), then Ti3C2Tx/PmPD composites were obtained. Delightedly, Ti3C2Tx/PmPD composites exhibited positive surface charge, expanded interlayer spacing, and enhanced hydrophobicity. Furthermore, the specific surface area of Ti3C2Tx/PmPD composite was five and 23 times that of Ti3C2Tx and PmPD, respectively. These advantages endowed Ti3C2Tx/PmPD composite with an excellent adsorption capacity of Cr(VI) (540.47 mg g−1), which was superior to PmPD (384.73 mg g−1), Ti3C2Tx MXene (137.45 mg g−1), and the reported MXene-based adsorbents. The Cr(VI) removal mechanism mainly involved electrostatic adsorption, reduction, and chelation interaction. This study developed a simple functionalization strategy, which would greatly explore the potential of MXenes in the field of anionic pollutants.

A composite consisting of a deep eutectic solvent and dispersed magnetic metal-organic framework (type UiO-66-NH2) for solid-phase extraction of RNA.

A cactus-shaped magnetic composite was prepared for solid-phase extraction of RNA. It is composed of the metal organic framework UiO-66-NH2 that was modified with Fe3O4 nanoparticles. The composite was then dispersed in a lactic acid-based deep eutectic solvent (DES, Fe3O4-COOH@UiO-66-NH2@DES). The structures of the sorbents were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry, vibrating sample magnetometry and thermogravimetric analysis. The extraction performance of sorbents was optimized and the maximum extraction capacity reached 246mg·g-1. Extraction is shown to mainly rely on chelation interaction, electrostatic interaction, hydrophobic interaction and hydrogen bonding interaction. The sorbent can selectively extract RNA over DNA, bovine hemoglobin and amino acids. Regeneration studies indicated that the sorbent can be re-used (after regenreation with DES) several times without obvious change of the extraction capacity. The successful extraction of RNA from yeast testified the practical application of the sorbent. Graphical abstractSchematic representation of the fabrication Fe3O4-COOH@UiO-66-NH2@DES, and itsapplication in the magnetic solid phase extraction of RNA.

In Situ Defect Passivation with Silica Oligomer for Enhanced Performance and Stability of Perovskite Solar Cells

AbstractPerovskite solar cells (PVSCs) have achieved excellent power conversion efficiency (PCE) but still suffer from instability issues. Defect passivation is an important route to simultaneously increase the efficiency and stability of PVSCs. Here, a strategy of incorporating silica oligomer in perovskite films for surface and grain boundary defect passivation is reported. Silica oligomer passivation agent (PA) is in situ formed through hydrolysis and condensation reaction of tetraethyl orthosilicate additive in perovskite precursor. The passivation mechanism is elucidated by density functional theory calculation, revealing stable chelating interaction and hydrogen bond interaction between PA and perovskite. Spectroscopic and electrical characterizations demonstrate that silica oligomer can enlarge grain sizes, prolong carrier lifetime, enhance charge carrier dynamics, and reduce trap state densities in perovskite films. Planar PVSCs with passivation achieve a highly improved PCE of 19.64% with a stabilized efficiency of 18.81%. More importantly, unencapsulated perovskite devices with passivation retain nearly 90% of original efficiency after 1000 h storage under ambient condition and sustained 87% of initial performance after high‐temperature (120 °C) thermal accelerated aging, showing highly enhanced moisture and thermal stability. Therefore, the present study provides a pathway to the future design and optimization of PVSCs with higher efficiency and greater stability.

Europium(III) functionalized 3D covalent organic framework for quinones adsorption and sensing investigation

Chemical functionalization is essential for tuning the physical-chemical characters and broadening the potential applications of covalent organic frameworks (COFs). Based on the multistep postsynthetic modification strategy, Eu (III)-functionalized 3D COF (Eu-3D-COF) was prepared by grafting of Eu (III) onto the carboxyl-funtionalized 3D-COF (COOH-3D-COF). With micropores dominated microspheres structure, Eu-3D-COF exhibited superior adsorption affinity to multi-rings contained quinones based on the π-π interaction, coordination and hydrogen-bonding interactions, especially to 9,10-phenanthrenequinone (PQ) whose adjacent carbonyl oxygens resulting preferable synergistic chelation interaction with Eu(III) was responsible for the maximum adsorption capacity, which was confirmed by instrumental characterizations. The adsorptivity of Eu-3D-COF was apparently improved in comparison with COOH-3D-COF. More importantly, grafting of Eu(III) turned on the fluorescence of the COF, making Eu-3D-COF also a superior chemosensor for sensing application. Its fluorescent can be selectively quenched by quinones, especially by PQ based on the PQ-Eu and PQ-COF interactions co-dominated energy transfer. Therefore, both as an adsorbent and a chemosensor, the multi-functional COF was explored for quinones adsorption and sensing detection investigation in detail. Eu-3D-COF has promising application potentials for hazardous quinones adsorption and sensing detection, which also opens new perspectives for inorganic-organic 3D-COF construction and multi-functional applications.

Adsorptive recovery of Au(III) from aqueous solution using crosslinked polyethyleneimine resins.

Resin adsorption is considered as a promising method to recover gold ions from wastewater, but further reduction reaction is required to convert gold ions into particles. In this study, a crosslinked polyethyleneimine resin (CPEIR) was developed via a suspension polymerization of polyethyleneimine (PEI) and ethylene glycol diglycidyl ether (EGDE) for gold recovery. The Au(III) adsorption capacities of CPEIR were significantly impacted by solution pH and initial Au(III) concentrations but unaffected by co-existing metal ions. Compared with commercial anion-exchange resin IRA400, the CPEIR exhibited higher sorption amount and selectivity for Au(III) due to its high density of amine and hydroxyl groups on the surfaces. The adsorption isotherm of Au(III) on CPEIR was well described by the Langmuir equation, and the maximum uptake amount of Au(III) was high up to 943.5 mg/g, much higher than the reported sorbents. The adsorption kinetic data on the CPEIR were fitted well by the Pseudo-second-order equation, and the intraparticle diffusion was found to be the rate-controlling process of Au(III) adsorption. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis confirmed that Au(III) ions were adsorbed on the CPEIR via electrostatic attraction and chelating interaction, and subsequently the partial loaded Au(III) ions were reduced to elemental gold whereas the hydroxyl groups of CPEIR were oxidized to carbonyl groups.

Adsorption of direct yellow brown D3G from aqueous solution using loaded modified low-cost lignite: Performance and mechanism

ABSTRACT Low-cost lignite-based, copper-containing adsorbents (Cu-raw) were developed through a simple ultrasonic impregnation protocol for enhanced adsorption of direct yellow brown D3G (DYB) from aqueous solutions while treating copper-containing wastewater. The adsorbent was characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersion spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption isotherms and kinetics were studied, and the factors that affect the adsorption, such as adsorbent dosage and solution pH, were investigated. The results showed that DYB adsorption was highly pH dependent and the isotherm of adsorption could be well described by the Langmuir-Freundlich model and the maximum DYB adsorption capacity was estimated to be 369 mg/g at 25°C. The electrostatic and chelating interactions were the main interfacial interaction mechanism, and the synergetic removal performance of lignite toward cationic metal ions and anionic dye was shown. The kinetic data were well fitted to the pseudo-second-order equation, indicating that chemical sorption was the rate-limiting step. The findings reported in this work highlight the potential of using lignite as an effective low-cost adsorbent for the removal of organic pollutants from wastewater.

A facile solvent-free and one-step route to prepare amino-phosphonic acid functionalized hollow mesoporous silica nanospheres for efficient Gd(III) removal

Abstract Gadolinium is known to be a most widely used but toxic rare-earth element, and Gd(III) ions exist in aqueous media will bring about serious damage to the ecosystem. However, few work on the application of adsorption strategy with enough high Gd(III) uptake is reported. Since the hollow mesoporous silica nanospheres (HMSNs) and amino-phosphonic acid (APA) compounds have shown inherent advantage for being used as effective adsorbent and chelating ligand in toxic metals adsorption due to their remarkable properties. Herein, we follow the cleaner production philosophy, proposing for the first time to modify the HMSNs nanomaterial with APA group by reacting phosphorous acid with cyano-functionalized hollow mesoporous SiO2 (CFHMSNs) via one-step reaction under solvent-free conditions, and apply to remove Gd(III) form wastewater. The obtained materials are characterized by a variety of techniques. Characterization results show that the APA-functionalized material (AFHMSNs) has ordered mesoporous structure, high stability and large surface area (825.3 m2/g). The maximum uptake of Gd(III) for AFHMSNs (387.3 mg/g) is much higher than those of the reported adsorbents because of the high surface area, and multifunctional chelating interactions of the adsorbent with Gd(III) ions. Gd(III) adsorption onto AFHMSNs can be well described by the Langmuir isotherm and pseudo second order kinetics model. The adsorption is chemical complexation mechanism which is proposed based on FTIR and XPS analysis. It is found for the first time that the adsorption of Gd(III) onto AFHMSNs slightly enhanced with the coexistence of Al3+ in the relatively lower concentrations, which may be due to the synergistic effect of pseudo-boehmite. This work provides a favorable strategy to design and synthesis of hollow mesoporous nanomaterial with superior adsorption performances and potential for the cleanup of toxic metals from wastewater.

Foamed urea-formaldehyde microspheres for removal of heavy metals from aqueous solutions

A simple foaming method was applied to fabricate urea formaldehyde (UF) microspheres with cross-linked porous structures for environmental remediation of heavy metals. The specific surface area and average pore radius of the resultant foamed UF microspheres were 11–29 m2/g and 11–25 nm, respectively, which increased with the increasing molar ratio of formaldehyde to urea. All the foamed UF microspheres showed good removal of heavy metals ions (Pb(II), Cu(II), and Cd(II)) in both single- and mixed-metal solutions. Further investigations of Pb(II) adsorption on a selected UF microspheres showed fast kinetics and relatively high adsorption capacity (21.5 mg/g), which can be attributed to the mesoporous structure and abundance of oxygen surface functional groups of the microspheres. Both experimental and model results showed that chelation or complexation interactions between Pb(II) and the surface functional groups were responsible to the strong adsorption of the heavy metal ions on the microspheres. Hydrochloric acid (0.05 M) successfully desorbed Pb(II) from the post-adsorption microspheres for multiple times and the regenerated microspheres showed high Pb(II) removal rates (>96%) in five adsorption-desorption cycles. With many promising advantages, foamed UF microspheres show great potential as a wastewater treatment agent for heavy metal removal.

Pyrazole–Isoindoline-1,3-dione Hybrid: A Promising Scaffold for 4-Hydroxyphenylpyruvate Dioxygenase Inhibitors

The discovery of 4-hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) inhibitors has been an active area of research due to their great potential as herbicides for weed control. Starting from the binding mode of known inhibitors of HPPD, a series of HPPD inhibitors with new molecular scaffolds were designed and synthesized by hybridizing 2-benzoylethen-1-ol and isoindoline-1,3-dione fragments. The results of the in vitro tests indicated that the newly synthesized compounds showed good HPPD inhibitory activity with IC50 values against the recombinant Arabidopsis thaliana HPPD (AtHPPD) ranging from 0.0039 μM to over 1 μM. Most promisingly, compound 4ae, 2-benzyl-5-(5-hydroxy-1,3-dimethyl-1H-pyrazole-4- carbonyl)isoindoline-1,3-dione, showed the highest AtHPPD inhibitory activity with a Ki value of 3.92 nM, making it approximately 10 times more potent than pyrasulfotole (Ki = 44 nM) and slightly more potent than mesotrione (Ki = 4.56 nM). In addition, the cocrystal structure of the AtHPPD-4ae complex was successfully resolved at a resolution of 1.8 Å. The X-ray diffraction analysis indicated that the two carbonyl groups of 2-benzoylethen-1-ol formed a bidentate chelating interaction with the metal ion, while the isoindoline-1,3-dione moiety formed pronounced π-π stacking interactions with Phe381 and Phe424. Moreover, water-mediated hydrogen bonding interactions were observed between Asn282 and the nitrogen atoms of the pyrazole ring of 4ae. The above results showed that the pyrazole-isoindoline-1,3-dione hybrid is a promising scaffold for developing HPPD inhibitors.

A chemical approach for ultrafast synthesis of SAPO-n molecular sieves

Silicoaluminophosphate (SAPO-n) molecular sieves are important microporous materials for chemical processes like MTO. Classical synthesis route for SAPO-n, i.e. hydrothermal method, generally requires dozens of hours (>24 h). In this work, we reported a chemical approach to significantly reduce required crystallization time to 40–120 min by adding citric acid (CA) in synthesis gel. The time consumed with the proposed process is comparable with that by special heating intensification method while it is simpler, cheaper, and greener than latter. The ultrafast crystallization was attributed to the non-classical nucleation theory inspired by kinetic analysis, in which chelation interaction between CA and Al3+ favored metastable phase generation evidenced by XRD and 27Al NMR. Other chelate agents (tartaric acid, ethylenediaminetetraacetic acid) with multi carbonic group also showed promising interaction. Moreover, the superior crystallization promotion effect could be applicable in the synthesis of other SAPO-n molecular sieves like SAPO-11, which indicates its great potentials in the future. With further optimization by structure promoter, the obtained SAPO-34 demonstrated sub-micron particle size, high ratio isolated Q0 state Si specie, and hierarchical structure, characterized by the SEM, XPS, 29Si NMR, TEM, and N2-isotherms. The promoted physiochemical properties favored superior performance during MTO test. This work opens up a new perspective to synthesize SAPO-n molecular sieves by a simple chemical approach in a highly efficient and environment friendly manner.

The Impact of pH on Catalytically Critical Protein Conformational Changes: The Case of the Urease, a Nickel Enzyme.

Urease uses a cluster of two NiII ions to activate a water molecule for urea hydrolysis. The key to this unsurpassed enzyme is a change in the conformation of a flexible structural motif, the mobile flap, which must be able to move from an open to a closed conformation to stabilize the chelating interaction of urea with the NiII cluster. This conformational change brings the imidazole side chain functionality of a critical histidine residue, αHis323, in close proximity to the site that holds the transition state structure of the reaction, facilitating its evolution to the products. Herein, we describe the influence of the solution pH in modulating the conformation of the mobile flap. High-resolution crystal structures of urease inhibited in the presence of N-(n-butyl)phosphoric triamide (NBPTO) at pH 6.5 and pH 7.5 are described and compared to the analogous structure obtained at pH 7.0. The kinetics of urease in the absence and presence of NBPTO are investigated by a calorimetric assay in the pH 6.0-8.0 range. The results indicate that pH modulates the protonation state of αHis323, which was revealed to have pKa =6.6, and consequently the conformation of the mobile flap. Two additional residues (αAsp224 and αArg339) are shown to be key factors for the conformational change. The role of pH in modulating the catalysis of urea hydrolysis is clarified through the molecular and structural details of the interplay between protein conformation and solution acidity in the paradigmatic case of a metalloenzyme.

Plasmonic Au–Ag Janus Nanoparticle Engineered Ratiometric Surface-Enhanced Raman Scattering Aptasensor for Ochratoxin A Detection

Ochratoxin A (OTA), a toxic mycotoxin, poses severe risks to environment and human health. Herein, we develop a ratiometric surface-enhanced Raman scattering (SERS) aptasensor based on internal standard (IS) methods for the sensitive and reproducible quantitative detection of OTA. Au-Ag Janus nanoparticles (NPs) are successfully synthesized under the guidance of 2-mercaptobenzoimidazole-5-carboxylic acid (MBIA), which possesses intrinsic Raman signals, thus no additional modification with a Raman reporter on NPs is required. In addition, Au-Ag Janus NPs exhibit amplified and stable SERS activity. MXenes nanosheets generate a unique and stable Raman signal, making them an ideal IS for quantitative Raman analysis. In principle, Au-Ag Janus NPs are assembled with MXenes nanosheets depending on hydrogen bond and the chelation interaction between MXenes nanosheets and OTA aptamers. In the presence of OTA, Au-Ag Janus NPs are dissociated from MXenes nanosheets due to the formation of aptamer/OTA complex, leading to the attenuation of Raman signal of Au-Ag Janus NPs, and meanwhile, the signal of MXenes nanosheets remain constant. Quantitatively, upon correction by the IS Raman signals, sensitive and quantitative detection can be achieved with the limit of detection (LOD) of 1.28 pM for OTA. Our results suggest that this ratiometric SERS aptasensor is a powerful tool which shows great promise for applications in complex systems.

Simultaneous adsorption of lanthanum and yttrium from aqueous solution by durian rind biosorbent

This paper presents the adsorption capacity of a biosorbent derived from the inner part of durian (Durio zibethinus) rinds, which are a low-cost and abundant agro-waste material. The durian rind sorbent has been successfully utilized to remove lanthanum (La) and yttrium (Y) ions from their binary aqueous solution. The effects of several adsorption parameters including contact time, pH, concentrations of La and Y, and temperature on the removal of La and Y ions were investigated. The adsorption isotherm and kinetics of the metal ions were also evaluated in detail. Both La and Y ions were efficiently adsorbed by the biosorbent with optimum adsorption capacity as high as 71 mg La and 35 mg Y per gram biosorbent, respectively. The simultaneous adsorption of La and Y ions follows Langmuir isotherm model, due to the favorable chelation and strong chemical interactions between the functional groups on the surface of the biosorbent and the metal ions. The addition of oxygen content after adsorption offers an interpretation that the rare-earth metal ions are chelated and incorporated most probably in the form of metal oxides. With such high adsorption capacity of La and Y ions, the durian rind sorbent could potentially be used to treat contaminated wastewater containing La and Y metal ions, as well as for separating and extracting rare-earth metal ions from crude minerals.

Designing an "Off-On" Fluorescence Sensor Based on Cluster-Based CaII-Metal-Organic Frameworks for Detection of l-Cysteine in Biological Fluids.

Recently, luminescent metal-organic framework (MOF) materials have attracted considerable attention in fluorescence sensing. In this essay, we prepared a new cluster-based CaII-MOFs {[Ca1.5(μ8-HL1)(DMF)2]·DMF}n (1) with good water dispersibility, excellent photoluminescence properties (FL quantum yield of 20.37%) and great fluorescence stability. Further, it was employed to design as an "off-on" fluorescence sensor for sensitive detection of l-cysteine. This proposed strategy was that fluorescence of CaII-MOFs 1 was quenched for providing a low fluorescence background by the introduction of Pb2+ forming the CaII-MOFs 1/Pb2+ hybrid system. The quenching effect could be ascribed to the static quenching mechanism because of the formation of ground-state complexes and coordination interactions between the free carboxyl of H4L1 ligands of CaII-MOFs 1 and Pb2+. Then, with the addition of l-cysteine into the CaII-MOFs 1/Pb2+ hybrid system, the fluorescence signal was immediately restored. This result was because the Pb2+ was gradually released from the hybrid system by chelation interactions between the -SH groups of l-cysteine and Pb2+. This method received a relative wide linear range varying from 0.05 to 40 μM and a low detection limit of 15 nM for detection of l-cysteine. This proposed strategy was also successfully applied to detect l-cysteine in human serum samples with satisfactory recoveries from 95.9 to 101.5%.

Augmenting the adsorption parameters of palladium onto pyromellitic acid-functionalized nanosilicas from aqueous solution

Many industrial wastewaters contain large amounts of palladium and the recovery of palladium from wastewater has great significance. Here, a new adsorbent (PMA-SNP) was synthesized by modifying nano-silica with pyromellitic anhydride to selectively adsorb Pd(II) in wastewater. Fourier transform infrared spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller equation, X-ray photoelectron spectroscopy and transmission electron microscopy were employed to characterize the adsorbent. At 25 °C, the adsorbent has the higher adsorption rate in the pH range of 2 to 5. The adsorption equilibrium is reached in 480 min and the maximum adsorption capacity is 53.61 mg/g. The adsorption kinetics and isotherms accord with pseudo-second-order and Langmuir models, respectively. The results show that the adsorption process is monolayer adsorption and the rate-limiting step is chemical adsorption. After five cycles, the removal rate of Pd(II) by PMA-SNP decreased slightly from 71.18% to 66.11% with good reusability. The thermodynamic data revealed that the adsorption was a spontaneous exothermic process. PMA-SNP can selectively adsorb palladium from wastewater containing various coexisting ions. Adsorption mechanism is based on the electrostatic and chelation interaction between Pd(II) ion and the O and N atoms. It can be concluded that PMA-SNP is an effective and promising adsorbent for the recovery of palladium from wastewater.

Metal Ion-Chelated Tannic Acid Coating for Hemostatic Dressing.

Tannic acid (TA), a high-molecular-weight polyphenol, is used as a hemostasis spray and unguent for trauma wound remedy in traditional medical treatment. However, the use of tannic acid on a large-area wound would lead to absorption poisoning. In this work, a TA coating was assembled on a quartz/silicon slide, or medical gauze, via chelation interaction between TA and Fe3+ ions and for further use as a hemostasis dressing. Protein adsorption on the TA coating was further investigated by fluorescence signal, ellipsometry analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The adsorbed bovine serum albumin (BSA), immunoglobulin G (IgG) and fibrinogen (Fgn) on the TA coating was in the manner of monolayer saturation adsorption, and fibrinogen showed the largest adsorption. Furthermore, we found the slight hemolysis of the TA coating caused by the lysed red blood cells and adsorption of protein, especially the clotting-related fibrinogen, resulted in excellent hemostasis performance of the TA coating in the blood clotting of an animal wound. Thus, this economic, environmentally friendly, flexible TA coating has potential in medical applications as a means of preparing novel hemostasis materials.