High Density Of Carboxyl Groups Research Articles

Ultrathin PEI-functionalized carboxyl covalent organic framework membranes for efficient CO2/N2 separation

Covalent organic frameworks (COF) are deemed as disruptive membrane materials owing to their versatile functionalities, high stability and ordered nanochannels. However, the size mismatch between the COF intrinsic pore and gas molecules becomes a grand challenge when using COF membrane for carbon capture. Herein, we propose a new type of polymer-functionalized COF laminar membranes through grafting CO2-phlic polyethyleneimine (PEI) polymer onto carboxylic acid COF (cCOF) laminar membranes. The cCOF nanosheets with high density of carboxyl groups are prepared via modified single phase solution method and then assembled to fabricate membranes. Further, the cCOF membranes are functionalized with PEI using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-Hydroxysuccinimide (EDC/NHS) coupling chemistry. The introduction of abundant amino groups from PEI afford the affinity of membranes toward CO2. Meanwhile, the graft of the PEI polymers reduces the defects or pinholes on the membrane surface. As a result, the PEI functionalized cCOF membranes exhibit a high CO2 permeance of 1004 GPU and a CO2/N2 selectivity of 33.7, which reach the carbon capture target performance and show great prospect for treating real flue gas. Our approach of functionalizing cCOF membranes with tailored functionalities may inspire the design of molecule-selective COF membranes.

In Situ Synthesis of CuO/Cu2O Nanoparticle-Coating Nanoporous Alumina Membranes with Photocatalytic Activity under Visible Light Radiation

We report the synthesis and characterization of CuO/Cu2O film supported on nanoporous alumina membranes (NAMs) and the photocatalytic properties in the removal of the organic pollutant methyl orange (MO). For this purpose, transparent nanostructured membranes were fabricated and sequentially modified with APTS ((3-aminopropyl)-trimethoxysilane) and EDTAD (ethylenediaminetetraacetic dianhydride) to form a highly functionalized surface with high density of carboxyl groups, which easily complex with copper cations. The Cu2+-modified membranes were annealed in a chemical vapor deposition (CVD) furnace to form a well-ordered nanostructured coating of CuO/Cu2O with photocatalytic properties. These modifications were followed by characterization with FT-IR and UV–visible spectra, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS). Finally, the photocatalytic performance of the NAM-CuO/Cu2O nanostructured membranes was tested in the aqueous removal of MO dye as a model reaction system. Our results revealed 50% photocatalytic removal of MO under continuous light irradiation for 2 h. The procedure presented in this work provides an adequate approach for the fabrication of nanostructured devices with photocatalytic properties for the degradation of organic compounds.

A Copper-Organic Framework with Carboxylate Groups for Efficient C2-C3 Hydrocarbons Capture

Increasing the ligand size could enlarge the pore volume of MOFs, which could further increase the gas adsorption capacity. Inspired by this, we synthesized a porous 3D metalorganic framework [Cu2(L1)·(H2O)2] ·2H2O·3DMF·(CH3)2NH2] (NEM-5) with a high density of carboxylate groups and CuII sites, which exhibited large uptakes for C2H2 (65 cm3 g-1), C2H4 (48 cm3 g-1), C2H6 (64.7 cm3 g-1), C3H6 (68 cm3 g-1), and C3H8 (63.4 cm3 g-1) at room temperature. Compared with MOF 1, NEM-5 has a similar topology and larger pore volume, but the gas adsorption capacities are significantly reduced, which might be attributed to the large pore size and low framework density of NEM-5.

One-step synthesis of gold nanoparticles for catalysis and SERS applications using selectively dicarboxylated cellulose and hyaluronate

Properties and applications of gold nanoparticles (AuNPs) depend on their characteristics which are intrinsically connected to the reducing and capping agents used in their synthesis. Although polysaccharides are commonly used for Au salt reduction, the control over the result is often limited. Here, the selectively dicarboxylated cellulose (DCC) and hyaluronate (DCH) with adjustable composition and molecular weight are used for the first time as reducing and capping agents for AuNPs preparation in an environmental friendly one-step synthesis. Mechanism of reduction and structure-function relationships between the composition of oxidized polysaccharides and properties of formed AuNPs are elucidated and the variances in the macromolecular architecture of dicarboxypolysaccharides are applied to guide the growth of AuNPs. While the homogenous structure and high density of carboxyl groups of fully-oxidized DCC induced isotropic growth of small and uniform AuNPs with good catalytic performance (d = ~20 nm, TOF = 7.3 min−1, k = 1.47 min−1), the lower stabilizing potential and slower reduction rates of the DCH induced the anisotropic growth of larger polyhedral ~50 nm nanoparticles, which increased the Surface-Enhanced Raman Scattering efficacy (9× stronger Raman signals on average compared to AuDCC). The use of dicarboxypolysaccharides with adjustable composition and properties thus introduced a new degree of freedom for the preparation of AuNPs with desired properties.

Improving the Adsorption Performance of Loofah Sponge towards Methylene Blue by Coating Ca2+ Crosslinked Sodium Alginate Layers on Its Fiber Surface

In this study, natural polymer sodium alginate (SA) was covered with high active carboxyl groups on the loofah sponge (LS) fiber surface to improve the adsorption ability of LS. The SA was covered on the LS fiber surface (LS@SA) through simple soaking in SA solution and then in situ hardening in Ca2+ solution. The influence of SA consistency on the SA loading ratio was estimated. The obtained LS@SA adsorbents were employed to absorb methylene blue (MB) from the water. The effects of various experimental parameters on the adsorption capacity of the LS@SA adsorbents were studied using a batch adsorption technique. Results indicated that the SA was successfully covered on the LS fiber surface and the SA loading rate increased with increasing SA concentration. The SA layer covering the LS fiber surface provided the LS@SA adsorbents with higher adsorption capacity towards MB than the original LS due to the high density of carboxyl groups on the SA molecular chain. In the adsorption process, the LS@SA adsorbents were pH dependent. The results also indicate that the LS@SA adsorbents have better reusability.

Modifying alginate beads using polycarboxyl component for enhanced metal ions removal

Designing desirable adsorbent for highly efficient removal of heavy metal ions is of practical significance, given the cost-effectiveness, environmental benign, natural abundance and easy-handling collection features. Herein, a bead-like adsorbent with high adsorption capacity was prepared by modifying alginate beads using polyacrylate with high density of carboxyl groups. The developed alginate/polyacrylate beads were collaboratively characterized by FT-IR, TGA, SEM, XPS, etc., and various adsorption conditions were tested including the pH of the solution, contact time and the initial concentration. The experimental data were fitted well by the Freundlich isotherm model, and the maximum adsorption capacity was obtained from the Langmuir model was 611.0 mg/g, and adsorption process followed the Pseudo-second-order kinetic model. The adsorption mechanisms conformed to multi-layer adsorption, and mainly dominated by chemical interactions. The bead-like adsorbent exhibited excellent reusability after eight sequential cycles and displayed higher adsorption capacity towards lead ions. This type of adsorbent might possess promising role in treating heavy metals from water by virtue of degradable, cost-effective component and high adsorption efficiency.

Green acid-free hydrolysis of wasted pomelo peel to produce carboxylated cellulose nanofibers with super absorption/flocculation ability for environmental remediation materials

Carboxylated nanocellulose hold great application potential and research value in environmental remediation owing to its eco-friendly nature, high specific surface area, high density of functional groups and abundant reserves properties. In present work, a new type of cellulose nanofibers (CNF) with high aspect ratio and high density of carboxyl groups were prepared by directly thermo-oxidizing natural wasted pomelo peel with H2O2. The effects of reaction time on the content of carboxyl groups, morphology, and thermal stability of CNF were investigated. It is found that pomelo-CNF (POCNF) with larger aspect ratio of 169 and carboxyl group contents of 1.711 ± 0.173 mmol/g was fabricated by reacting at 60 °C for 6 h. Furthermore, the high density of carboxyl groups of POCNF allowed it to graft functional polyetherimide (PEI) on the surface of nanocellulose, and the resulting PNOCNF-PEI showed excellent adsorption performance to pollutants, such as malachite green (MG) and Cu(II), with adsorption capacity of 530 mg/g to MG and 74.2 mg/g to Cu(II). Moreover, the adsorbent showed excellent reusability. Besides, the possible adsorption kinetics/mechanism of nanocelluloses to various pollutants has been provided. The simple preparation process and excellent properties of POCNF made it become a viable candidate as environmental remediation material.

Conducting polyaniline/poly (acrylic acid)/phytic acid multifunctional binders for Si anodes in lithium ion batteries

The poor cycling stability is a tricky problem in the silicon-based lithium-ion batteries. Herein, we fabricate a three-dimension polyaniline/poly (acrylic acid)/phytic acid compound binder for the silicon anodes. In this binder, polyaniline-doped and gelated by phytic acid functions as a continuous electrically conductive network structure for the silicon anodes. Meanwhile, a high density of carboxyl groups provided by poly (acrylic acid) enhance the stability of the silicon electrodes by supplying strong binding ability with current collectors and silicon particles. Using this multifunctional binder in silicon anode, we succeed in manufacturing very long cycle life of larger than 1000 cycles at a current density of 4.2 A g−1.

A Robust Route to Co2(OH)2CO3 Ultrathin Nanosheets with Superior Lithium Storage Capability Templated by Aspartic Acid‐Functionalized Graphene Oxide

AbstractTwo‐dimensional (2D) nanomaterials are widely recognized as an important class of functional materials possessing superior electrochemical reaction kinetics. Herein, an L‐aspartic acid (AA)‐modified graphene oxide (GO) templating strategy is developed to in situ yield ultrathin (i.e., ≈5 nm) cobalt carbonate hydroxide (Co2(OH)2CO3) nanosheets as advanced anode materials of lithium ion batteries. Notably, the covalent tethering of AA on the GO surface renders a high density of carboxyl groups that impart effective loading of Co‐containing precursors and subsequent growth into Co2(OH)2CO3 nanosheets bridging adjacent GO layers. The lasagna‐like Co2(OH)2CO3‐GO nanocomposites exhibit an ultrahigh lithium storage capacity of 1770 mAh g−1 after 500 cycles at 100 mA g−1. It is noteworthy that the cycled Co2(OH)2CO3 phase separates into homogeneously dispersed Co(OH)2 and CoCO3 phases with two different charge plateaus at ≈1.2 and 2.0 V, respectively, which effectively inhibit large‐scale homophase coarsening of Co, Li2CO3, and LiOH. The much shortened Li+/e− transfer distance enabled by individual ultrathin Co2(OH)2CO3 nanosheet together with robust layer‐by‐layer assembled nanostructure of Co2(OH)2CO3‐GO confers the superior electrochemical reactivity and mechanical stability. As such, the amino acid‐modified GO templating strategy may represent a simple yet robust means of crafting a variety of 2D nanostructured composites of interest for energy storage applications.

Effect of neighboring groups on the pH responsive adsorption/desorption behaviors of carboxylate functionalized hollow polymer particles

ABSTRACTIn this article, a serial of bi‐functionalized hollow polymer particles (BF‐HPPs), containing both carboxylate and different amide/amine groups [HPP‐NH2, HPP‐ethylenediamine (EDA), and HPP‐diethylenetriamine (DETA)], were specially designed and synthesized to investigate the effect of neighboring amino groups on their adsorption/desorption behavior. Due to the high density of carboxylate groups, these BF‐HPPs can serve as efficient adsorbents for selective removal of positively charged methylene blue (b‐MB). With increasing chain length of the neighboring amino groups, the maximum adsorption capacities (qmax) at pH 7 decrease dramatically from 606.1 mg g−1 for HPP‐NH2, to 404.9 mg g−1 for HPP‐EDA, and 332.2 mg g−1 for HPP‐DETA, due to increasing steric hindrance. Significantly, the equilibrium adsorption can be achieved within 15 min for HPP‐EDA and HPP‐DETA, while it takes more than 720 min for HPP‐NH2. Moreover, the qmax of HPP‐DETA exhibits remarkable pH‐sensitive property, which decreases sharply to 32.7 mg g−1 at pH 3 due to strong electrostatic repulsion between positively charged ammonium groups and b‐MB molecules. Accordingly, the desorption efficiency of HPP‐DETA reached up to 94% after one desorption step, which is much higher than that of HPP‐EDA (78%) and HPP‐NH2 (60%). The absorbed b‐MB can be facilely desorbed and the adsorption capacity of the regenerated HPP‐DETA keeps above 95% after five consecutive adsorption–desorption cycles. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1404–1413

Surface-Modified Cellulose Nanofibers-graft-poly(lactic acid)s Made by Ring-Opening Polymerization of l-Lactide

Highly crystalline cellulose nanofibers with a high density of carboxylate groups only on the surfaces were prepared from both softwood and non-wood cellulose pulp. The preparation method used 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of native cellulose fibrils in an aqueous TEMPO/NaBr/NaClO system and subsequent postoxidation with NaClO2 in acetate buffer (pH 4.8). The TEMPO-oxidized cellulose nanofibers (TOCNs) possessed a carboxylate content of 1.7 mmol g−1 and a crystallinity of 67–69% with a crystallite size of ∼3 nm. The TOCNs were used to produce highly crystalline TOCN-graft-poly(lactic acid) (PLA) nanocomposites via ring-opening polymerization of l-lactide in a polar aprotic solvent. Effects of the reaction temperature and the molar ratio of l-lactide to carboxylate surface groups, on the efficiency of surface grafting were investigated to potentially improve the crystallinity and thermal properties of the nanocomposites. The crystallinity of TOCN-g-PLA products was 59–66% greater than the crystallinity of neat PLA.

A Carboxyl-Terminated Dendrimer Enables Osteolytic Lesion Targeting and Photothermal Ablation of Malignant Bone Tumors.

Malignant bone tumor accompanied by tumor-associated osteolysis remains a challenging task in clinical practice. Nanomedicines engineered with bone-targeting ligands, such as alendronate and pamidronate, are developed for targeted delivery of therapeutic agents to bone tumors. However, these targeting strategies usually show relatively poor selectivity toward the healthy skeletons and the osteolytic lesions because of the high binding affinity of bisphosphonates with all the bone tissues. Here, we reported a carboxyl-terminated dendrimer as the candidate to preferentially deliver therapeutic nanoparticles to the osteolytic lesions in a malignant bone tumor model. The high density of carboxyl groups on dendrimer surface endow the polymer with natural bone-binding capability. The dendrimer encapsulated with platinum nanoparticle predominantly accumulates at the osteolytic lesions around bone tumors rather than at healthy bone tissues in vivo. The therapeutic experiments reveal that the dendrimer-mediated photothermal therapy efficiently suppresses bone tumors and osteolysis, and the anionic polymer exhibits minimal cytotoxicity and hematologic toxicity. The results suggest that the carboxyl-terminated dendrimer is a promising candidate for selective delivery of therapeutics to the osteolytic lesions and photothermal treatment of malignant bone tumors.

One-Step Synthesis of Quadrilateral-Shaped Silver Nanoplates with Lamellar Structures Tuned by Amylopectin Derivatives.

Polymers or small molecules with functional groups were always employed to synthesize two-dimensional (2D) silver nanostructures, but the polysaccharides and derivatives have rarely been used for their preparation, let alone of uniform quadrilateral shapes. Herein, amylopectin derivatives containing concentrated carboxyl groups were first used for the synthesis of uniform 2D quadrilateral silver nanoplates (QAgNPs) with lamellar structure. As a native hyperbranched polysaccharide, amylopectin was esterified with 10-undecenoyl chloride and then modified via thiol–ene click chemistry to introduce high amount and high density of carboxyl groups. Then, QAgNPs were synthesized via UV photoreduction in the presence of the resultant amylopectin 11-((3-carboxyl)ethylthio)undecanoate (APUE3-MPA) in water–tetrahydrofuran binary system. QAgNPs showed novel uniform quadrilateral shapes with lamellar structure, as verified by their wide-angle X-ray scattering patterns. The average interlayer distance was around 1.3 nm, whereas the average edge lengths of QAgNPs varied between 0.29 ± 0.07 and 1.09 ± 0.25 μm. The concentration of APUE3-MPA and the amount of water in the reaction system strongly affected the shapes of QAgNPs. Thus, the reaction system and the arrangement of numerous carboxyl groups were the key factors for the formation of lamellar-structured QAgNPs.

Room Temperature Magnesite Precipitation

Magnesite (MgCO3) is one of the most stable sinks for carbon dioxide (CO2) and is therefore of great interest for long-term carbon storage. Although magnesite is the thermodynamically stable form of magnesium carbonate, the kinetic inhibition of low-temperature precipitation has hindered the development of carbon sequestration strategies that can be economically conducted under ambient temperature. Here, we document the precipitation of magnesite from waters (magnesite saturation index = 1.45) in batch reactors at room temperature with the aid of carboxylated polystyrene microspheres over the course of 70 days. Microspheres provide surfaces with a high density of carboxyl groups that act to bind and dehydrate Mg2+ ions in solution, thereby minimizing the kinetic barrier and facilitating magnesite formation. Magnesite crystals are observed on sphere surfaces and their organic matrixes. Mineral identification was confirmed by X-ray diffraction and selected area electron diffraction of a thin section obtaine...

Plasma micro-nanotextured polymeric micromixer for DNA purification with high efficiency and dynamic range

We present a polymeric microfluidic chip capable of purifying DNA through solid phase extraction. It is designed to be used as a module of an integrated Lab-on-chip platform for pathogen detection, but it can also be used as a stand-alone device. The microfluidic channels are oxygen plasma micro-nanotextured, i.e. randomly roughened in the micro-nano scale, a process creating high surface area as well as high density of carboxyl groups (COOH). The COOH groups together with a buffer that contains polyethylene glycol (PEG), NaCl and ethanol are able to bind DNA on the microchannel surface. The chip design incorporates a mixer so that sample and buffer can be efficiently mixed on chip under continuous flow. DNA is subsequently eluted in water. The chip is able to isolate DNA with high recovery efficiency (96± 11%) in an extremely large dynamic range of prepurified Salmonella DNA as well as from Salmonella cell lysates that correspond to a range of 5 to 1.9 × 108 cells (0.263 fg to 2 × 500 ng). The chip was evaluated via absorbance measurements, polymerase chain reaction (PCR), and gel electrophoresis.

The nano necklace made of single-walled carbon nanotubes and an azo-containing polymer: Island-like carboxyl distribution, bead-like morphology formation, and photophysical properties manipulation

The formation of a bead-shaped microstructure of poly{[3-octylthiophene-2,5-diyl]-[p-amino-azobenzylidenequinomethane]}bonded SWNT (PDTAABQ-SWNT) reveals the inhomogeneous distribution of reactive sites along a SWNT in a covalent functionalization. The bead-shaped microstructure arises from the twisting and entangling of polymer chains due to spatial confinement and geometrical restriction, as a result of dense functionalization into island-like small areas containing a high density of carboxyl groups on the SWNT sidewall. Accordingly a portion of (Ca. 24.14%) trans-azobenzene side groups of PDTAABQ are forced to isomerize to the cis form due to a steric effect arising from the overcrowded environment in the ‘bead’. The experimental findings are well-correlated with the molecular simulation, particularly for the physical realization of a bead-shaped microstructure and a trans-cis isomerization. The distortion in morphology due to the inhomogeneous distribution of reactive sites leads to a method for controlling the electronic structure and photophysical properties of SWNT. The transient optical properties of PDTAABQ-SWNT show a faster decaying component on a picosecond timescale but a very unusual slower decaying tail on a nanosecond timescale as compared to the timescale of the parent polymer (PDTADBQ). The severely distorted polymer chains with cis azobenezene side groups result in the reduction of the exciton mobility, leading to the longer fluorescence lifetime. This is confirmed by a similar ratio of the undepleted photoexcitons after 2.2 ns (Ca. 23.28%) and the ratio of the severely distorted polymers (Ca. 24.14%).

Preparation of large-area graphene oxide sheets with a high density of carboxyl groups using O2/H2 low-damage plasma

Abstract We have used low-damage O 2 plasma treatment (O 2 -LDPT), with chemically reactive radicals generated in an inductively coupled plasma system equipped with a complementary filter, to prepare large-area graphene oxide (GO) sheets. Raman spectroscopy and X-ray photoelectron spectroscopy demonstrated that oxidative functionalities were formed on the graphene surfaces. However, the carboxyl group, which is the most important functional group for biological applications, only occupied about 6.1% of the GO sheets formed using O 2 -LDPT. By adding H 2 during O 2 -LDPT, the compositional ratio of carboxyl group could be greatly increased to 10.8%. Optical emission spectroscopy revealed that this enhancement was achieved because of the presence of hydroxyl radicals in O 2 /H 2 -LDPT.

Mechanochemical Synthesis of a Carboxylated Carbon Catalyst and Its Application in Cellulose Hydrolysis

AbstractA carbon catalyst containing a high density of carboxyl groups was prepared by solvent‐free mechanochemical oxidation of activated carbon by using persulfate salts as the oxidant. The mechanochemical oxidation preferentially oxidized the carbon to introduce carboxyl groups without incorporation of sulfonated groups. The material exhibited hydrophilic behavior and was easily dispersed in water. Upon mix‐milling, the oxidized carbon showed good catalytic activity for the hydrolysis of cellulose, even at a low catalyst loading. Glucose was obtained in 85 % yield from mix‐milled cellulose in the presence of a trace amount of HCl after a reaction time of 20 min.

A Novel Electrochemical Immunosensor Incorporating a Pyrrole/4-(3-Pyrrolyl) Butyric Acid Conducting Polymer

A novel amperometric immunosensor was fabricated using an electropolymerized conducting polymer composite of pyrrole and 4-(3-pyrrolyl) butyric acid as the probe immobilization matrix. The biomolecule was immobilized via covalent bonding on the polymer surface with a high density of carboxyl groups. Instead of directly attaching the probe to the polymer surface, the streptavidin-biotin affinity complex was introduced to improve the bioactivity, orientation, and the amount of immobilized material. Polyvinyl alcohol was employed to improve the hydrophilicity of the polymer surface and further decrease the nonspecific protein adsorption. As a result, high sensitivity and specificity were achieved with a wide linear dynamic range. Using mouse immunoglobulin G as a model protein, the immunosensor exhibited a linear relationship between 7 ng/mL and 20 µg/mL with a limit of detection of 7 ng/mL.

Plasma Treated High-Density Polyethylene (HDPE) Medpor Implant Immobilized with rhBMP-2 for Improving the Bone Regeneration

We investigate the bone generation capacity of recombinant human bone morphogenetic protein-2 (rhBMP-2) immobilized Medpor surface through acrylic acid plasma-polymerization. Plasma-polymerization was carried out at a 20 W at an acrylic acid flow rate of 7 sccm for 5 min. The plasma-polymerized Medpor surface showed hydrophilic properties and possessed a high density of carboxyl groups. The rhBMP-2 was immobilized with covalently attached carboxyl groups using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. Carboxyl groups and rhBMP-2 immobilization on the Medpor surface were identified by Fourier transform infrared spectroscopy. The activity of Medpor with rhBMP-2 immobilized was examined using an alkaline phosphatase assay on MC3T3-E1 cultured Medpor. These results showed that the rhBMP-2 immobilized Medpor increased the level of MC3T3-E1 cell differentiation. These results demonstrated that plasma surface modification has the potential to immobilize rhBMP-2 on polymer implant such as Medpor and can be used for the binding of bioactive nanomolecules in bone tissue engineering.