Presence Of Amine Functional Groups Research Articles

Highly selective CO2 uptake in Calix[4]arene compounds immobilized on silica gel

Macrocyclic calix[4]arene molecules were immobilized onto silica surface and shown to be highly selective hybrid adsorbents for CO2 capture application. These hybrid adsorbents were prepared by immobilization of various calix[4]arene molecules, with differing upper rim functional groups: tert-butyl, amine, and calix[4]arene, onto surface of silica gel through 2,4-toluene diisocyanate (TDI) linker. Synthesized hybrid materials were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, nitrogen adsorption–desorption measurements, scanning electron microscopy and elemental analysis. Single component adsorption of pure gas CO2, CH4 and N2 were measured experimentally at three different temperature and pressure up to 30 bar using the volumetric method. Among all the materials, amino functionalized calix[4]arene, with calixarene loading of (~0.21 mmol g−1), exhibited improved CO2 uptake as well as exceptionally high ideal adsorption selectivity (CO2:N2 = 443) and (CO2:CH4 = 148) at 25 °C and 1 bar, mainly due to the presence of amine functional groups. Moreover, for investigating the affinity between CO2 and adsorption sites, isosteric heat of adsorption were calculated by Clausius–Clapeyron equation. Results of systematic experimental investigation in this report may pave the way toward later studies on these promising highly potential hybrid adsorbents in CO2 adsorption field area, according to their unique properties and designable structure.

SYNTHESIS AND PROPERTIES OF ION EXCHANGERS DERIVED FROM NON-WOOD CELLULOSE

A rational scheme for the processing of large-scale agro-industrial waste – walnut shells Juglans Regia L. and apricot kernels Prunus Armeniaca L. was proposed. At first stage, the raw material was delignificated using liquid ammonia to remove hemicelluloses and lignin. Isolated non-wood pulp is chemically modifying to increase sorption and ion exchange properties. For the synthesis of anion exchangers, cellulose was aminated using pyridine or trimethylamine after preliminary treatment consequentially with formalin and C2H5OH in HCl medium. As a result, we obtained high and weakly-basic ion exchangers with nitrogen content of 10.3–11.5% and high exchange capacity towards various classes of inorganic anions. For synthesis of cation exchangers, cellulose was treated with solution consisting of 20% H3PO4, 40% CO(NH2)2, and 40% H2O. Consequently, we obtained phosphorus-containing high-acidic cation exchangers with exchange capacity towards heavy metal of 5.5–8.6 mmol∙cm–3. Both types of ion exchangers have a high capacity towards uranium: anion exchanger – 4.25 mmol∙cm–3 and cation exchanger – 4.94 mmol∙cm–3, respectively. Average total yield of ion exchangers related to weight of air-dry feedstock was 90%. Synthesized ion exchangers characterized by IR spectroscopy. Presence of amine functional groups –NH2 in aminated cellulose and phosphate ester groups –OPO(OH)2 in phosphorylated cellulose was established. Specific surface area and total static exchange capacity of synthesized ion exchangers were established. An environmentally friendly method for the disposal of spent solutions from the synthesis of cation exchangers was proposed. It allows getting a liquid complex fertilizer containing 17% N and 13.9% P2O5. Usage of this fertilizer for grain crops feeding increases plants length by 40–75%, as well as overall biomass increase by 20–30%.

Covalent modification of reduced graphene oxide with piperazine as a novel nanoadsorbent for removal of H2S gas

In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly efficient nanoadsorbent for H2S gas removal. Temperature optimization within the range of 30–90 °C was set which significantly improved the adsorption capacity of the nanoadsorbent. The operational conditions including the initial concentration of H2S (60,000 ppm) with CH4 (15 vol%), H2O (10 vol%), O2 (3 vol%) and the rest by helium gas and gas hour space velocity (GHSV) 4000–6000 h−1 were examined on adsorption capacity. The results of the removal of H2S after 180 min by RGO-N-(piperazine), reduced graphene oxide (RGO), and graphene oxide (GO) were reported as 99.71, 99.18, and 99.38, respectively. Also, the output concentration of H2S after 180 min by RGO-N-(piperazine), RGO, and GO was found to be 170, 488, and 369 ppm, respectively. Both chemisorption and physisorption are suggested as mechanism in which the chemisorption is based on an acid–base reaction between H2S and amine, epoxy, hydroxyl functional groups on the surface of RGO-N-(piperazine), GO, and RGO. The piperazine augmentation of removal percentage can be attributed to the presence of amine functional groups in the case of RGO-N-(piperazine) versus RGO and GO. Finally, analyses of the equilibrium models used to describe the experimental data showed that the three-parameter isotherm equations Toth and Sips provided slightly better fits compared to the three-parameter isotherms.

Molecular weight distribution characterization of reactive higher ethyleneamines using size-exclusion chromatography with conventional calibration

Ethyleneamines have been produced and commercialized for decades in the chemical industry for a diverse range of applications. The presence of amine functional groups provides them opportunity to adsorb onto surfaces which can make them a very challenging sample matrix to analyze using separation techniques. In the present report, a new aqueous SEC-RI method, which enables MWD characterization of higher ethyleneamines, is described. The sample preparation was based on the dilute-and-shoot methodology. A surface-modified SEC column with positively charged groups attached to the stationary phase was used. The mobile phase composition (salt concentration, pH) was optimized to suppress interaction between the ethyleneamines and the packing material. Very symmetrical peak shapes were achieved for low MW monodisperse ethyleneamines despite their high primary amine content. MWD calculations were conducted using conventional narrow standard calibration with partial linear extrapolation of the calibration curve. The narrow standards were of the same chemistry as the samples of interest. Consequently, the standard components display a consistent behaviour towards the column packing as the sample components which makes the present method more robust and the interpretation of the quantitative results more convenient. Effect on the measured MW averages and MW distribution due to various experimental parameters (e.g., system variability, mobile phase preparation, sample concentration) were investigated showing good repeatability (RSD < 2%) for Mn, Mw, and Mz.

Interfacial polymerization of facilitated transport polyamide membrane prepared from PIP and IPC for gas separation applications

A facilitated transport polyamide (PA) membrane was developed for gas separation by interfacial polymerization reaction of piperazine (PIP) and isophthaloyl chloride (IPC) supported on polysulfone (PSF) membrane previously prepared by dry/wet phase inversion method. The properties of the prepared membranes were characterized by SEM, FT-IR, TGA, and XRD. SEM images showed that a defect-free PSF, and rough PA membranes were fabricated, while the FT-IR spectra confirmed the formation of PA layer on top of the PSF support. The separation performance of the thin film PA and PSF membranes was evaluated using four gasses (CO2, CH4, N2, and O2). Compared to the PSF membrane, the PA membrane demonstrated an increased selectivity of CO2/CH4 and CO2/N2 by 178%, 169%, respectively. This improvement was attributed to the presence of amine functional groups, which acted as a fixed carrier to facilitate the transport of CO2 gas across the membrane. However, building the PA layer on top of PSF support reduced the membrane permeance of CO2 from 2.41 to 2.12 GPU as a result of the increased mass transfer resistance. Furthermore, the effect of operating temperature and pressure on the separation performance of the membranes was investigated.

Study of the performance of amino-functionalized ordered mesoporous carbon in the transesterification of soybean oil

In this study, the synthesis of the amino-functionalized mesoporous carbon resulted from organic–inorganic self-assembly reaction of triblock copolymer P123, sucrose and silica was carried out. The mesoporous carbons with desirable textural properties such as BET surface area of 956 m2/g, average pore diameter of 4.7 nm and pore volume of 1.07 cm3/g were obtained. Their surface was modified and functionalized with amine groups. Also, small angle powder X-ray diffraction (XRD) confirmed the hexagonal order of porous structure and Fourier transform infrared (FT-IR) analysis of catalyst indicated presence of amine functional groups onto the surface. FESEM and TEM imaging for the purpose of morphological and structural order analysis have been carried out. The performance of the prepared catalysts was evaluated in the production of biodiesel through transesterification of soybean oil with methanol. Gas chromatography (GC) analysis of biodiesel samples demonstrated that at the temperature of 64 °C, methanol to oil molar ratio of 24:1 and 2 wt% of catalyst loading (based on oil used), about 91% of triglycerides were converted to methyl esters (biodiesel) after 6 h.

Hydrogel nanocomposite based on chitosan-g-acrylic acid and modified nanosilica with high adsorption capacity for heavy metal ion removal

In this study, a novel hybrid hydrogel based on chitosan, acrylic acid and amine-functionalized nanosilica was prepared and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. This hydrogel nanocomposite was used for removal of Co2+, Cu2+, Pb2+ and Zn2+ ions from aqueous solution. The metal ion adsorption was measured by inductively coupled plasma mass spectrometry. The adsorption behavior showed that the presence of modified nanosilica enhanced the porosity of the hydrogel network and affected its adsorption capacity in response to different parameters such as nanosilica content, metal ion concentration, adsorbent content, pH value and contact time. The morphology study showed that the nanosilica which was functionalized by 3-aminopropyl triethoxysilane increased the porosity of the hydrogel and created extensive network domains which can permeate water. The nanosilica may act as a physical cross-linker. The adsorption behavior of nanocomposite hydrogel showed that its high porous structure and the presence of amine functional groups on the nanosilica surface enhanced its adsorption capacity. On the other hand, the nanocomposite did not show any selectivity for removal of Co2+, Cu2+, Pb2+ and Zn2+ ions from aqueous solution due to the specific interaction between nanocomposite and these metal ions.

Preparation, characterization and properties of amine-functionalized silicon carbide/polyimide composite films

High performance amino-functionalized silicon carbide/polyimide (m-SiC/PI) composite films were prepared using a straightforward polycondensation, and the nanoparticles (NP) obtained were modified using 3-aminopropyl-trimethoxysilane. The presence of amine functional groups made dispersions of m-SiC NP in dimethylacetamide more homogeneous and uniform. Their structures and stabilities were investigated using X-ray diffraction, scanning electron microscopy and zeta-potential analysis. The thermal stability and the tensile strength of the m-SiC/PI composite films improved with increasing m-SiC NP content, for example the inclusion of 3 wt% m-SiC NP increased the tensile strength and Young's modulus by 41.1% and 40.1%, respectively. The morphology of the cross-section revealed that breakage within these composite films was the result of ductile fracture, whereas for pure PI film it was caused by brittle fracture.

Fabrication and Characterization of Magnetoplasmonic Liposome Carriers

Phospholipid liposome encapsulating gold-coated superparamagnetic iron oxide nanostructures is developed. Gold nanoshells were fabricated by a multistep procedure through electroless plating of Au on the surface of the gold decorated superparamagnetic iron oxide nanoparticles (SPIONs). They were then stabilized using polyvinyl pyrolidone (PVP) with the molecular weight of 25 kDa, followed by their encapsulation within hydrophilic core of liposomes, composed of egg yolk phosphatidylcholine (EPC) : cholesterol (CHOL) with a molar ratio of 2:1and an efficiency of 94%. Surface chemistry, hydrodynamic size and electrokinetic potential, morphology and optical properties of magnetoplasmonic liposomes (MPLs) were studied by FT-IR, DLS, TEM and UV-Vis spectroscopy, respectively. FT-IR results showed the presence of amine functional groups on the surface of SPIONs as well as coordination of the nitrogen and oxygen atoms of PVP to the Au atoms at the surface of gold nanoshells. The effect of surface coating on the stability of nanostructures was discussed. The obtained results show that the fabricated hybrid nanostructures are potentially useful for delivery of plasmonic nanoparticles to cells and can be used as exogenous absorber in laser thermal therapy.

Reversible Self-Assembling of Comb-Like Functionalized Dextran Surfactant Polymers as an SPR-Sensing Surfaces

Novel surface plasmon resonance (SPR) sensing surfaces were developed from the perspective of reversible self-assembling of the mixed dextran surfactant polymers onto SPR gold chips. Two comb-like dextran surfactant polymers, which are different in their dextran molecular weight (MW) distribution and the presence of amine functional groups, and their characterization were synthesized. These structurally well-defined surfactant polymers include a bimodal amine dextran surfactant polymer and a monomodal dextran surfactant polymer. The bimodal one consists of poly (vinyl amine) (PVAm) backbone with amine functionalized high MW dextran, non-functionalized low MW dextran and hydrophobic hexyl pendant groups. Allyl high MW dextran aldonic acid and low MW dextran aldonic acid chains with various ratios were sequentially attached to PVAm. The unreacted amine groups on the backbone were further grafted with hexanoic acid and the allyl groups on the high MW dextran were finally converted to amine. The monomodal surfactant polymer, PVAm with non-functionalized low MW dextran and hexyl branches, was synthesized and characterized using similar procedures, except with the absence of allyl high MW dextran aldonic acid and the amine functionalization. The molecular compositions of the surfactant polymers were determined by FTIR and 1H-NMR. Surface active properties at the air-water interface were determined using tensiometer. Reduction in water contact angles was observed on the surfactant treated surfaces. Reversible self-assembling of the synthesized surfactant polymers on SPR gold chip surface was monitored using SPR analysis. Reproducibility of the mixed surfactant assembling process was preliminarily confirmed by a consistent increase in reflectivity change, while no detectable changes in the reflectivity under a 1-h buffer flow indicated stability of the absorbed surfactant layer. Moreover, a simple, quick flow of a basis regeneration solution completely removed the adsorbed surfactant from the surface. Our preliminary investigation also exhibited that the regenerated SPR gold chip was effectively reusable.

Morphology-controlled magnetite nanoclusters via polyethyleneimine-mediated solvothermal process

Abstract A facile one-pot synthesis of polyethyleneimine (PEI)-functionalized magnetic nanoclusters (MNPs) through the solvothermal method was reported for various applications. The morphology of the MNPs can be systematically tuned from loose flower-like to porous nanoclusters by controlling the pH of the PEI stabilizer. At low pH, the intense electrostatic repulsion according to the large amount of protonated amine groups of PEI would play a key role on self-assembly process to generate the loose nanostructure. Due to the presence of amine functional groups on the surface, these nanoclusters provide high degree of dispersibility in water and abundant anchoring groups for further attachment of biomolecules. Magnetization study of the MNPs indicated that they had saturated magnetization upto 80 emu g−1.

Functionalized metal organic framework-polyimide mixed matrix membranes for CO2/CH4 separation

Abstract This work describes the preparation, characterization and CO 2 /CH 4 gas separation properties of mixed matrix membranes (MMMs) made from five different as-synthesised metal organic frameworks (MOFs): UiO-66 (Zr-BDC), NH 2 -UiO-66 (Zr-ABDC), UiO-67 (Zr-BPDC), MOF-199 (Cu-BTC), and NH 2 -MOF-199 (containing 25% ABDC and 75% BTC mixed-linker) fillers and as-synthesized 6FDA–ODA polyimide as the polymeric matrix in order to investigate the ligand functionalization effect (–NH 2 ) on MOF's adsorption properties and on the CO 2 /CH 4 gas separation performance of the MMMs. The as-synthesized MOFs were carefully characterized by XRD, SEM, ATR-FTIR, and N 2 adsorption at 77 K. MMMs were also characterized using ATR-FTIR, and SEM and CO 2 /CH 4 pure and mixed gas separation measurements were carried out. Incorporation of the fillers in the MMMs resulted in an increase in perm-selectivity except for the UiO-67 filler. The presence of amine-functional groups in as-synthesized MOFs increased both the ideal selectivity and CO 2 permeability. On the other hand, MMM made with UiO-66 increased significantly the CO 2 permeability compared to the neat 6FDA–ODA membrane without any loss in ideal selectivity. Using mixed-linker NH 2 -MOF-199 enhanced the perm-selectivity of the MMM maybe because of the presence of some whisker-like roughness on their crystal surface as observed in SEM.

A novel study of antibacterial activity of copper iodide nanoparticle mediated by DNA and membrane damage

In this article potential activity of nanoparticles (NPs) of copper iodide (CuI) as an antibacterial agent has been presented. The nano particles are synthesized by co-precipitation method with an average size of 8nm as determined by Transmission Electron Microscope (TEM). The average charge of the NPs is −21.5mV at pH 7 as obtained by zeta potential measurement and purity is determined by XRD. These NPs are able to kill both gram positive and gram negative bacteria. Among the bacteria tested, DH5α is more sensitive but Bacillus subtilis is more resistant to NPs of CuI. Consequently, the MIC and MBC values of DH5α is least (0.066mg/ml and 0.083mg/ml respectively) and B. subtilis is highest (0.15mg/ml and 0.18mg/ml respectively) among the tested bacterial strains. From our studies it is inferred that CuI NPs produce reactive oxygen species (ROS) in both gram negative and gram positive bacteria and it also causes ROS mediated DNA damage for the suppression of transcription as revealed by reporter gene assay. Probably ROS is formed on the surface of NPs of CuI in presence of amine functional groups of various biological molecules. Furthermore they induce membrane damage as determined by atomic force microscopy (AFM). Thus production of ROS and membrane damage are major mechanisms of the bactericidal activity of these NPs of CuI.

Investigating the interfacial interaction of different aminosilane treated nano silicas with a polyurethane coating

In this work different nano silica particles varying in aminosilane functionalities were dispersed into a polyurethane clear coating (PU). The optical clarity of the resulting films as well as the mechanical integrities were studied utilizing haze transmission and dynamic mechanical analysis respectively. In addition, the curing behavior of films was investigated using differential scanning calorimetry. It was found that particle dispersibility directly depended on the amount of grafted silane at the surface of nano silicas. Also the presence of amine functional groups on silica particles resulted in a systematic improvement of Tg and therefore in enhanced mechanical performance. These were attributed to an increased interfacial interaction and formation of some urea linkages in the hard segment of the polyurethane matrix. The DSC analyses also showed that the heat of reaction of particle loaded samples were all lower than that of the blank PU due to the facilitated interaction of amino groups at the silica surface with isocyanate cross-linker.

Tensile mechanical behavior and fracture toughness of MWCNT and DWCNT modified vinyl-ester/polyester hybrid nanocomposites produced by 3-roll milling

This study aims to investigate the tensile mechanical behavior and fracture toughness of vinyl-ester/polyester hybrid nanocomposites containing various types of nanofillers, including multi- and double-walled carbon nanotubes with and without amine functional groups (MWCNTs, DWCNTs, MWCNT-NH 2 and DWCNT-NH 2). To prepare the resin suspensions, very low contents (0.05, 0.1 and 0.3 wt.%) of carbon nanotubes (CNTs) were dispersed within a specially synthesized styrene-free polyester resin, conducting 3-roll milling technique. The collected resin stuff was subsequently blended with vinyl-ester via mechanical stirring to achieve final suspensions prior to polymerization. Nanocomposites containing MWCNTs and MWCNT-NH 2 were found to exhibit higher tensile strength and modulus as well as larger fracture toughness and fracture energy compared to neat hybrid polymer. However, incorporation of similar contents of DWCNTs and DWCNT-NH 2 into the hybrid resin did not reflect the same improvement in the corresponding mechanical properties. Furthermore, experimentally measured elastic moduli of the nanocomposites containing DWCNTs, DWCNT-NH 2, MWCNTs and MWCNT-NH 2 were fitted to Halphin–Tsai model. Regardless of amine functional groups or content of carbon nanotubes, MWCNT modified nanocomposites exhibited better agreement between the predicted and the measured elastic moduli values compared to nanocomposites with DWCNTs. Furthermore, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to reveal dispersion state of the carbon nanotubes within the hybrid polymer and to examine the CNT induced failure modes that occurred under mechanical loading, respectively. Based on the experimental findings obtained, it was emphasized that the types of CNTs and presence of amine functional groups on the surface of CNTs affects substantially the chemical interactions at the interface, thus tuning the ultimate mechanical performance of the resulting nanocomposites.

Moisture Absorption Analysis of Interfacial Fracture Test Specimens Composed of No-Flow Underfill Materials

In a previous study, we found that moisture preconditioning strongly influenced the interfacial fracture toughness of the underfill/solder mask interface, decreasing the interfacial adhesion by approximately one-half for both classifications of underfill/solder mask interfaces after 725 h of exposure at 85°C/85%RH. To better understand the rate and mechanisms for moisture transport through the interfacial fracture test specimens, a diffusion analysis was implemented based on traditional, analytical solutions of Fick’s second law of diffusion. Test specimens were constructed to experimentally determine the diffusion coefficient for each underfill. Since both underfill encapsulants proved to exhibit non-Fickian behavior at 85°C/85%RH, the application of the analytical Fickian solution for the test specimens was limited to the associated JEDEC criteria of 168 hours for 85°C/85%RH. A finite element analysis was performed to illustrate the moisture concentration in the interfacial fracture test specimens for initial times of exposure to the humid environment. The results of this study demonstrate that the presence of amine functional groups considerably retard moisture penetration through underfill encapsulants.