Polar‐Functionalized,Crosslinkable, Self‐Healing,and Photoresponsive Polyolefins

The nonpolar nature of polyolefins is one of their biggest limitations. Now, an efficient route to generate polar‐functionalized, crosslinkable, self‐healing, photoresponsive polyolefins with thermoplastic, elastomeric, and thermosetting properties is reported. Tunable amounts of carboxylic acid and a cyclic comonomer are installed onto polyolefins by palladium‐catalyzed terpolymerization reactions. The incorporated carboxylic acid unit can alter the surface properties of polyolefins. The subsequently introduced Fe³⁺/citric acid combination induces dynamic crosslinking and enables self‐healing. Under UV light irradiation, citric acid reduces Fe³⁺ to Fe²⁺ and decreases the crosslinking density. The Fe²⁺ moiety can be easily oxidized back to Fe³⁺, making the process reversible at the expense of citric acid. The incorporated cyclic comonomer modulates the crystallinity of polyolefins, provides elastic properties, and installs carbon–carbon double bonds for sulfur‐induced vulcanization.     

Synthesis of Fluorescent Carbon Dots and Their Application in Ascorbic Acid Detection

Water-soluble fluorescent carbon dots (CDs) were synthesized by a hydrothermal method using citric acid as the carbon source and ethylenediamine as the nitrogen source. The repeated and scale-up synthetic experiments were carried out to explore the feasibility of macroscopic preparation of CDs. The CDs/Fe³⁺ composite was prepared by the interaction of the CDs solution and Fe³⁺ solution. The optical properties, pH dependence and stability behavior of CDs or the CDs/Fe³⁺ composite were studied by ultraviolet spectroscopy and fluorescence spectroscopy. Following the principles of fluorescence quenching after the addition of Fe³⁺ and then the fluorescence recovery after the addition of asorbic acid, the fluorescence intensity of the carbon dots was measured at λex = 360 nm, λem = 460 nm. The content of ascorbic acid was calculated by quantitative analysis of the changing fluorescence intensity. The CDs/Fe³⁺ composite was applied to the determination of different active molecules, and it was found that the composite had specific recognition of ascorbic acid and showed an excellent linear relationship in 5.0–350.0 μmol·L⁻¹. Moreover, the detection limit was 3.11 μmol·L⁻¹. Satisfactory results were achieved when the method was applied to the ascorbic acid determination in jujube fruit. The fluorescent carbon dots composites prepared in this study may have broad application prospects in a rapid, sensitive and trace determination of ascorbic acid content during food processing.     

锰(Ⅲ)离子与羧酸或α-羟基羧酸体系引发丙烯酰胺聚合

 锰(Ⅲ)离子可以引发烯类单体自由基聚合。羧酸,α-羟基羧酸对丙烯酰胺聚合有促进作用,其活性顺序为羟基多元羧酸(柠檬酸)>羟基羧酸(乳酸)>羧酸(正丁酸)。测定了在较高酸性([H⁺]=3.0M)的硫酸水溶液中,单独Mn³⁺,Nn³⁺-乙醇酸,Mn³⁺-乳酸引发丙烯酰胺聚合的活化能与动力学方程。     

Electrocatalytic behaviour of citric acid at a cobalt phthalocyanine-modified screen-printed carbon electrode and its application in pharmaceutical and food analysis

Cobalt phthalocyanine-modified screen-printed carbon electrodes (CoPC-SPCEs) have been investigated as disposable sensors for the measurement of citric acid. The analyte was found to undergo an electrocatalytic oxidation process involving the Co²⁺/Co³⁺ redox couple. Calibration plots were found to be linear in the range 2 mM to 2.0 M; replicate determinations of a 5.2 mM citric acid (n = 4) solution gave a coefficient of variation of 1.43%. Additions of metal ions, such as Ag⁺, Pb²⁺, Cu²⁺, Fe³⁺ and Ca²⁺, were found not to interfere. The effects of hesperidin, cysteine, ethylenediaminetetraacetic acid (EDTA), ascorbic, formic, malic, malonic, tartaric, oxalic and trichloroacetic acids on the determination of citric acid were examined and, under the conditions employed, only oxalic acid and EDTA were found to give any significant interference. The sensors were evaluated by carrying out citric acid determinations on spiked and unspiked samples of an acid citrate dextrose (ACD) formulation, lime flesh and juice. For lime juice, recoveries were calculated to be 96.8% (% CV = 2.7%) for a sample fortified with 5% citric acid and for ACD 99.4% (%CV = 2.6%) when fortified at 2.30% citric acid. Further studies showed the possibility of determining citric acid concentrations in lime juice and fruit directly, without the need for an added electrolyte. These performance characteristics indicate that reliable data may be obtained for citric acid measurements in such samples. To our knowledge, this is the first report on the electrocatalytic oxidation of citric acid and its application using a CoPC-SPCE.     

Separation and indirect ultraviolet detection of ferrous and trivalent iron ions by using ionic liquids in ion chromatography

A method of simultaneous separation and indirect ultraviolet detection of different valence iron ions Fe²⁺ and Fe³⁺ by using ionic liquids as mobile phase additives and ultraviolet absorption reagents on a cation exchange column functionalized with carboxylic acid group was developed. The effects of ionic liquids, organic acids, detection wavelength, etc. on separation and detection of Fe²⁺ and Fe³⁺ were investigated and the mechanism was discussed. The pyridinium and imidazolium ionic liquids were not only ultraviolet absorption reagents of indirect ultraviolet detection but also effective components for separating Fe²⁺ and Fe³⁺. The separation and detection of Fe²⁺ and Fe³⁺ can be achieved using 0.5 mmol/L pyridinium ionic liquid?1.2 mmol/L methanesulfonic acid as the mobile phase. The determination of Fe²⁺ and Fe³⁺ had a good linear relationship in the concentration range of 1?100 mg/L. The limits of detection of Fe²⁺ and Fe³⁺ were 0.12 and 0.09 mg/L, respectively. This method was applied to the actual sample detection in the field of medical analysis. The spiked recoveries were between 97.3 and 99.5%, and the relative standard deviations were less than 0.6%. The method is simple, accurate, and reliable, and is an analytical method with universal and practical value.     

A Shear-Thinning,Self-Healing,Dual-Cross Linked Hydrogel Based on Gelatin/Vanillin/Fe3+/AGP-AgNPs: Synthesis,Antibacterial, and Wound-Healing Assessment

A shear-thinning and self-healing hydrogel based on a gelatin biopolymer is synthesized using vanillin and Fe³⁺ as dual crosslinking agents. Rheological studies indicate the formation of a strong gel found to be injectable and exhibit rapid self-healing (within 10 min). The hydrogels also exhibited a high degree of swelling, suggesting potential as wound dressings since the absorption of large amounts of wound exudate, and optimum moisture levels, lead to accelerated wound healing. Andrographolide, an anti-inflammatory natural product is used to fabricate silver nanoparticles, which are characterized and composited with the fabricated hydrogels to imbue them with anti-microbial activity. The nanoparticle/hydrogel composites exhibit activity against Escherichia coli, Staphylococcus aureus, and Burkholderia pseudomallei, the pathogen that causes melioidosis, a serious but neglected disease affecting southeast Asia and northern Australia. Finally, the nanoparticle/hydrogel composites are shown to enhance wound closure in animal models compared to the hydrogel alone, confirming that these hydrogel composites hold great potential in the biomedical field.     

Mussel-mimicking sulfobetaine-based copolymer with metal tunable gelation,self-healing and antibacterial capability

In the present study, the sulfobetaine-based copolymer bearing a dopamine functionality showed gel formation adjusted by the application of metal salts for gelation and various values of pH. Normally, the liquid-like solution of the sulfobetaine-based copolymer and metal cross-linkers is transformed to a gel-like state upon increasing the pH values in the presence of Fe³⁺ and Ti³⁺. Metal-induced coordination is reversible by means of the application of EDTA as a chelating agent. In the case of Ag⁺ ions, the gel is formed through a redox process accompanied with the oxidative coupling of the dopamine moieties and Ag⁰ particle formation. Mussel-mimicking and metal-dependent viscoelastic properties were observed for Fe³⁺, Ti³⁺, and Ag⁺ cross-linking agents, with additionally enhanced self-healing behavior in comparison with the covalently cross-linked IO₄⁻ analogues. Antibacterial properties can be achieved both in solution and on the surface using the proper concentration of Ag⁺ ions used for gelation; thus, a tunable amount of the Ag⁰ particles are formed in the hydrogel. The cytotoxicity was elucidated by the both MTT assay on the NIH/3T3 fibroblast cell line and direct contact method using human dermal fibroblast cell (F121) and shows the non-toxic character of the synthesized copolymer.     

Kationenaustausch an komplexbildender Cellulose mit α (β)-Alanin-N,N-diessigsäure-Ankergruppen

The efficiency of a complex forming cellulose ion-exchanger with α(β)-alanin-N,N-diacetic acid anchor groups, containing still weakly acid carboxylic groups, is compared with that of a modified carboxyethylcellulose with the same type of the anchoring carboxylic functional groups and its specific behaviour in column chromatography was followed by binary mixtures of the cations CrO ₄ ^2? , Fe³⁺, Cu²⁺, Ni²⁺, Pb²⁺, Co²⁺, Cd²⁺, Mn²⁺, Ca²⁺, Mg²⁺.     

Interference from Trace Copper in Electrochemical Investigations Employing Carboxylic Acid Terminated Thiol Modified Gold Electrodes

Unexpectedly, electrochemistry at variable chain length carboxylic acid terminated alkylthiol self‐assembled monolayers (SAMs) on gold electrodes gives rise to a Faradaic process in buffered aqueous electrolyte solution. In particular, the three‐carbon chain length, 3‐mercaptopropionic acid (MPA), exhibits a chemically reversible process with a mid‐point potential of 175 mV vs. Ag/AgCl under conditions of cyclic voltammetry. This process is associated with the presence of trace (parts per billion) amounts of copper(II) ions present in the chemical reagents used to prepare the aqueous electrolyte and also from the gold electrode itself. The carboxylic acid moiety on the SAM concentrates Cu²⁺ ions by coordination and this surface confined layer is then reduced. Methods to minimize the interference of Cu²⁺ ions at carboxylic acid terminated SAM are discussed and caution with respect to the interpretation of protein electrochemistry is recommended when using carboxylic acid functionalized SAMs to provide biocompatible electrochemical transduction surfaces, unless a metal free environment can be obtained.     

Comportement électrochimique du ferrocène,du pérylène et du tétracène dans une électrode à pâte de carbone à liant électrolytique dans les mélanges eau–acide phosphorique

The carbon dough electrode with incorporated electrolyte has been used to analyse the electrochemical behaviour of ferrocene, tetracene and perylene in phosphoric acid media 0.1 to 14.8 M. The cyclic voltammetry results obtained for ferrocene with the carbon dough electrode corroborate with polarographic data. Voltamperometric study of the aromatic hydrocarbon oxidation Ar such that of perylene and tetracene on the carbon dough electrode has allowed to establish the normal potential of the corresponding oxido-reducing systems. The existence of the four oxidation states: Ar, Ar⁺, ArH⁺ and Ar²⁺ at different concentrations of phosphoric acid is specified. The results of this study can be used to establish correlations between some of concentrated solution properties of different acids.     

Flexible,high sensitive and radiation-resistant pressure-sensing hydrogel

Excellent radiation resistance is a prerequisite for pressure-sensitive hydrogels to be used in high-energy radiation environments. In this work, tannic acid-modified boron nitride nanosheet（BNNS-TA） is first prepared as the radiation-resistant additive by a facile one-step ball milling of hexagonal boron nitride and tannic acid. Then, polyacrylamide（PAAm）-based pressure-sensitive hydrogel doped with BNNS-TA and Fe³⁺ions is fabricated. The ternary BNNS-TA/Fe³⁺/PAAm hydrogel...     

Catechol-Functionalized Polyolefins

The incorporation of comonomers during ethylene polymerization can efficiently modulate important material properties of the polyolefins. Utilizing bioresourced comonomers for the generation of high-performance polyolefin materials is attractive from a sustainability point of view. In this contribution, bioresourced eugenol and related comonomers were incorporated into polyolefins through palladium-catalyzed copolymerization and terpolymerization reactions. Importantly, high-molecular-weight catechol-functionalized polyolefins can be generated. The introduction of different metal ions induces efficient interactions with the incorporated catechol groups, leading to enhanced mechanical properties and self-healing properties. Moreover, the catechol functionality can greatly improve other properties such as surface properties, adhesion properties, and compatibilizing properties. The catechol-functionalized polyolefin was demonstrated as a versatile platform polymer for accessing various materials with dramatically different properties.     

Preparation,electrochemical behavior and variable temperature magnetic properties of transition metal complexes containing 2-phenyl-4,5-di-(2-pyridyl)imidazole

We report the synthesis of three new complexes featuring first row transition metal ions (Mn²⁺, Fe²⁺, or V³⁺) and a 2-pyridyl-substituted imidazole ligand. We investigate the electronic and magnetic properties of the complexes via electronic spectroscopy, cyclic voltammetry, superconducting quantum interference device magnetometry and density functional theory calculations. Complexes with Fe²⁺ or V³⁺ are redox active, and we observe spin crossover from the variable temperature magnetic susceptibility data for the complex with Fe²⁺. We intend to use these complexes as precursors to bimetallic mixed-valent materials.     

Enhanced Viscosity of Poly(acrylamide) Solution in the Presence of Chromium Citrate Triggered by Release of CO2

Partially hydrolyzed polyacrylamide (HPAM) has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr³⁺ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr³⁺ so that the crosslinking between HPAM and Cr³⁺ can be prevented completely. Due to the decomposition of the bicarbonate (HCO₃^-) embedded in solution, CO₂ released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr³⁺ increased accordingly. When the complexation of Cr³⁺ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased significantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate (KH₂PO₄), the release of CO₂ was very slow and the condition was highly controlled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr³⁺ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery.     

Preparation and characterization of copper chloride supported on citric acid‐modified magnetite nanoparticles (Cu2+‐CA@Fe3O4) and evaluation of its catalytic activity in the reduction of nitroarene compounds

A new, powerful and recyclable copper catalyst were prepared by heterogenization of copper chloride using of Fe₃O₄ nano particles modified with citric acid as a linker. This system can catalyze reduction of nitroaren compound to aniline derivatives in the presence of Sodium borohydride as a reduction agent in moderate to good yields. In addition, easy separation and recoverable with an external permanent magnet is the dominant properties of this catalyst (Cu²⁺‐CA@Fe₃O₄).     

Aqueous Phase Sensing of Fe3+ and Ascorbic Acid by a Metal–Organic Framework and Its Implication in the Construction of Multiple Logic Gates

A new Hf^IV‐based metal‐organic framework with UiO‐66 topology was synthesized via a one‐step solvothermal method by using 3‐methyl‐4‐phenylthieno[2,3‐b]thiophene‐2,5‐dicarboxylic acid (H₂MPTDC) as a ligand. The MOF material showed a high stability in a broad pH range (from pH 2 to pH 12) in an aqueous medium. The presence of hydrophobic methyl and phenyl substituents in the carboxylic acid ligand and strong Hf?O bond play crucial roles in its stability. The new MOF material was systematically characterized by various techniques such as XRPD, N₂ sorption, thermogravimetric analyses and FT‐IR spectroscopy. The photophysical properties of the MOF material were also examined by steady‐state and time‐resolved fluorescence studies. It was observed that the blue fluorescence of the MOF material was selectively quenched in the presence of Fe³⁺ ion in pure aqueous medium. A mechanistic study disclosed that quenching occurs via a strong inner filter effect (IFE) arising from Fe³⁺ ion in aqueous medium. Interestingly, the fluorescence of the MOF material can be recovered by elimination of the IFE of Fe³⁺ ion via reduction of Fe³⁺ ion by ascorbic acid (AA). Based on the fluorescence recovery by AA, a MOF based on‐off‐on probe was developed for the sensing of Fe³⁺ ion and AA in aqueous medium. Inspired by this reversible sensing event, we demonstrate basic (NOT, OR, YES, INHIBIT and IMP) and higher integrated logic operations utilizing this fluorescent MOF. This MOF‐based logic systems could be potentially used for next‐generation logic‐gate based analytical applications as well as for the detection and discrimination of targeted molecules in various complex domains.     

Microwave-assisted synthesis of colorimetric and fluorometric dual-functional hybrid carbon nanodots for Fe3+ detection and bioimaging

Carbon nanodots (CDs) based fluorescent nanoprobes have recently drawn much attention in chemo-/bio-sensing and bioimaging. However, it is still challenging to integrate the colorimetric and fluorometric dual readouts into a single CD. Herein, novel hybrid CDs (HCDs) are prepared by a simple microwave-assisted reaction of citric acid (CA), branched polyethyleneimine (BPEI) and potassium thiocyanate (KSCN). As-prepared HCDs show extraordinary properties, including excitation-dependent emission, satisfactory fluorescence quantum yield (46.8%), excellent biocompatibility and optical stability. Significantly, the fluorescence intensity at 450 nm exhibits linear correlation over the Fe³⁺ concentration from 1 μmol/L to 150 μmol/L with a detection limit (LOD) of 52 nmol/L. Meanwhile, the solution color changes from colorless to orange, and the absorbance at 460 nm increased linearly with Fe³⁺ concentration ranging from 0.02 mmol/L to 5 mmol/L (LOD: 3.4 μmol/L). All the evidence illustrates that the HCDs can be conditioned for specific Fe³⁺ sensing with colorimetric and fluorometric dual readouts, which has also been verified with paper-based microchips. The possible mechanism is attributed to the specific interactions between surface functional groups on the HCDs and Fe³⁺. Additionally, the HCDs are successfully applied in sensing Fe³⁺ in wastewater and living cells, demonstrating its potential applications in future environment monitoring and disease diagnosis.     

Poly(2-acrylamido glycolic acid-co-acryloyl morpholine) and poly(2-acrylamido glycolic acid-co-acrylamide): Synthesis, characterization, and retention properties for environmentally impacting metal ions

Poly(2-acrylamido glycolic acid-co-acrylamide), P(AGA-co-AAm), and poly(2-acrylamido glycolic acid-co-4-acryloylmorpholine), P(AGA-co-AMo), were synthesized by radical polymerization. The water-soluble polymers containing tertiary amine, amide, hydroxyl, and carboxylic acid groups were investigated as polychelatogen, in view of their metal ion binding properties by using the liquid-phase polymer-based retention technique under different experimental conditions. The retention properties for the following metal ions were investigated: Ag⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Al²⁺, Cr³⁺ and Fe³⁺. P(AGA-co-AMo) showed a selective retention for tri-valent cation Al³⁺ at pH 3, but no retention at higher pH. P(AGA-co-AAm) showed the highest metal ion retention capability, specially at pH 5 and pH 7 with values close to 100% to di-valent cations.     

Synthesis and application of fluorescent N,S co-doped carbon dots based on on-off-on quenching mode for the collaboration detection of iron ions and ascorbic acid

Nitrogen and sulfur co-doped carbon dots (NS-CDs) were synthesized by one-step solvothermal method using oleic acid as the medium, ʟ-cystine and citric acid monohydrate as precursors. Based on the “on-off-on” fluorescence quenching mode, a novel method was established for determination of both Fe³⁺ and ascorbic acid. The synthesized NS-CDs can be employed as fluorescence chemical sensors for the direct determination of free iron in the aqueous phase and indirect determination of the ascorbic acid contents of vitamin C tablets with linear ranges of 0–10 μM (n = 3) and 0–30 μM (n = 3), and detection limits of 36.6 and 102.5 nM, respectively. These results demonstrate that the proposed method exhibits good selectivity and linearity.     

Preparation and characterization of high-rate and long-cycle LiFePO4/C nanocomposite as cathode material for lithium-ion battery

Olivine LiFePO₄/C nanocomposite cathode materials with small-sized particles and a unique electrochemical performance were successfully prepared by a simple solid-state reaction using oxalic acid and citric acid as the chelating reagent and carbon source. The structure and electrochemical properties of the samples were investigated. The results show that LiFePO₄/C nanocomposite with oxalic acid (oxalic acid: Fe²⁺= 0.75:1) and a small quantity of citric acid are single phase and deliver initial discharge capacity of 122.1 mAh/g at 1 C with little capacity loss up to 500 cycles at room temperature. The rate capability and cyclability are also outstanding at elevated temperature. When charged/discharged at 60 °C, this materials present excellent initial discharge capacity of 148.8 mAh/g at 1 C, 128.6 mAh/g at 5 C, and 115.0 mAh/g at 10 C, respectively. The extraordinarily high performance of LiFePO₄/C cathode materials can be exploited suitably for practical lithium-ion batteries.