Effect Of Immobilization Method Research Articles

Effect of Immobilization Methods on the Production of Polyethylene-cellulose Biocomposites via Ethylene Polymerization with Metallocene/MAO Catalyst

Polyethylene-cellulose biocomposites were synthesized here via the ethylene polymerization with metallocene as a catalyst along with methylaluminoxane (MAO) as a cocatalyst. The immobilization method in which the catalyst or cocatalyst is fixed onto the catalytic filler (cellulose) can be classified into 3 methods according to the active components fixed onto the filler surface: 1) only metallocene catalyst (Cellulose/Zr), 2) only MAO cocatalyst (Cellulose/MAO) and 3) mixture of metallocene and MAO (Cellulose/(Zr+MAO)). It was found that the different immobilization methods or different fillers altered the properties of the obtained composites and also the catalytic activity of the polymerization systems. It was found that Cellulose/MAO provided the highest catalytic activity among all fillers due to a crown-alumoxane complex, which caused the heterogeneous system with this filler behaved similarly to the homogeneous system. The different fillers also produced the biocomposites with some different properties such as crystallinity which Cellulose/Zr provided the highest crystallinity compared with other fillers as observed by a thermal gravimetric analysis-differential scanning calorimetry (TGA-DSC). Nevertheless, the main crystal structure indicated to the typical polyethylene was still observed for all obtained biocomposites with different fillers as observed by an X-ray diffractometer (XRD). Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Effect of immobilization method and particle size on heavy metal ion recovery of thermoresponsive polymer/magnetic particle composites

To examine the effect of the immobilization method and particle size on the Cu(II) recovery performance of the thermoresponsive polymer, poly(NIPAM-co-AA), and on its immobilization onto magnetic support, we compare the "grafting to" and the "in situ" methods, and use two different supports, such as magnetite nanoparticles and ferrite particles with primary particle sizes of approximately 21 nm and 12 μm, respectively. The results show that although the magnetite nanoparticle forms aggregates and the surface area of the primary particle cannot be fully utilized for immobilization; the immobilized copolymer amounts on the magnetite nanoparticles are about 10–42 times higher than that on the ferrite particle. For Cu(II) adsorption, poly(NIPAM-co-AA) immobilized on the magnetite nanoparticles show adsorption amounts approximately 13–20 times higher than that on the ferrite particle. The effect of the immobilization method is also examined by comparing the "grafting to" and the "in situ" methods. Between the two methods, the "in situ" method shows a higher immobilized copolymer amount and better Cu(II) adsorption property. These results show that a combination of the "in situ" method, as the immobilization method, and magnetite nanoparticle, as support, can be a very effective approach to synthesize the thermoresponsive adsorbent of poly(NIPAM-co-AA) immobilized on magnetic particles.

Effect of immobilization methods and the pore structure on CO2 separation performance in silica-supported ionic liquids

The CO2 separation performance in ionic liquids modified porous silica gels prepared by the impregnation and grafting methods were investigated. The effects of impregnation amount and pore size distribution of adsorbents with different types of ionic liquids on the CO2/N2 selectivity and water vapour adsorption and diffusion coefficient were analyzed in detail. The porous structures were characterized by CO2 adsorption isotherms at 0 °C. Adsorption behavior of CO2 (at 25, 40 and 60 °C) and N2 (at 40 °C) was measured using a gravimetric method. Compared with the impregnated samples, the grafting of ILs on the support surface only causes a weak loss of microporosity, leading to a slight decrease in CO2 adsorption capacity, and has much better recycling. CO2/N2 selectivity and water resistance are however enhanced, especially samples with the longer chain on imidazolium cation. A conventional homogeneous surface diffusion model for ILs grafted silica was used to estimate the diffusivities and good agreement between experimental values and fitting curves were obtained. For ILs modified silica prepared with impregnation method, the CO2 diffusivity constants include diffusion coefficients in ionic liquid phase and silica phase simultaneously. The diffusion coefficients are at a level of 10−7-10−9 m2 s−1 and about two or three orders of magnitude higher than that of neat ILs. The grafted silica exhibits diffusivities faster than those of the impregnated silica, indicating that more ionic liquids accessed into inner pore is unfavorable for CO2 diffusion.

Engineering and Characterization of Peptides and Proteins at Surfaces and Interfaces: A Case Study in Surface-Sensitive Vibrational Spectroscopy.

Understanding molecular structures of interfacial peptides and proteins impacts many research fields by guiding the advancement of biocompatible materials, new and improved marine antifouling coatings, ultrasensitive and highly specific biosensors and biochips, therapies for diseases related to protein amyloid formation, and knowledge on mechanisms for various membrane proteins and their interactions with ligands. Developing methods for measuring such unique systems, as well as elucidating the structure and function relationship of such biomolecules, has been the goal of our lab at the University of Michigan. We have made substantial progress to develop sum frequency generation (SFG) vibrational spectroscopy into a powerful technique to study interfacial peptides and proteins, which lays a foundation to obtain unique and valuable insights when using SFG to probe various biologically relevant systems at the solid/liquid interface in situ in real time. One highlighting feature of this Account is the demonstration of the power of combining SFG with other techniques and methods such as ATR-FTIR, surface engineering, MD simulation, liquid crystal sensing, and isotope labeling in order to study peptides and proteins at interfaces. It is necessary to emphasize that SFG plays a major role in these studies, while other techniques and methods are supplemental. The central role of SFG is to provide critical information on interfacial peptide and protein structure (e.g., conformation and orientation) in order to elucidate how surface engineering (e.g., to vary the structure) can ultimately affect surface function (e.g., to optimize the activity). This Account focuses on the most significant recent progress in research on interfacial peptides and proteins carried out by our group including (1) the development of SFG analysis methods to determine orientations of regular as well as disrupted secondary structures, and the successful demonstration and application of an isotope labeling method with SFG to probe the detailed local structure and microenvironment of peptides at buried interfaces, (2) systematic research on cell membrane associated peptides and proteins including antimicrobial peptides, cell penetrating peptides, G proteins, and other membrane proteins, discussing the factors that influence interfacial peptide and protein structures such as lipid charge, membrane fluidity, and biomolecule solution concentration, and (3) in-depth discussion on solid surface immobilized antimicrobial peptides and enzymes. The effects of immobilization method, substrate surface, immobilization site on the peptide or protein, and surrounding environment are presented. Several examples leading to high impact new research are also briefly introduced: The orientation change of alamethicin detected while varying the model cell membrane potential demonstrates the feasibility to apply SFG to study ion channel protein gating mechanisms. The elucidation of peptide secondary structures at liquid crystal interfaces shows promising results that liquid crystal can detect and recognize different peptides and proteins. The method of retaining the native structure of surface immobilized peptides or proteins in air demonstrates the feasibility to protect and preserve such structures via the use of hydromimetic functionalities when there is no bulk water. We hope that readers in many different disciplines will benefit from the research progress reported in this Account on SFG studies of interfacial structure-function relationships of peptides and proteins and apply this powerful technique to study interfacial biomolecules in the future.

Effect of Immobilization Method in the Electrocatalytic Properties of Alcohol-Dehydrogenase Enzyme

Alcohol dehydrogenase enzyme (ADH) from Saccharomyces cerevisiae is immobilized on glassy carbon surface by two methods: physical adsorption and covalent-bonding in order to compare the electrocatalytic properties as a function of the immobilization method. Physical adsorption was carried out by deposition of a mixture composed with nicotinamide-adenine dinucleotide (NAD) as coenzyme, Nafion® (5 wt%) as a binder and ADH onto a graphite surface. Physical adsorption was carried out by deposition of a mixture composed with nicotinamide-adenine dinucleotide (NAD) as coenzyme, Nafion® (5 wt%) as a binder and ADH onto a graphite surface. The covalent-bonding immobilization consisted of a polyaniline film (previously synthesized by cyclic voltammetry on graphite surface) which naturally bonds with NAD and tetra-butylammonium bromide (TBAB) in the presence of ADH. Cyclic voltammetry was used to evaluate the redox behavior and confirm the presence of ADH. Furthermore, the electrocatalytic activity of both bio-electrode arrays was evaluated in terms of the ethanol oxidation reaction showing excellent performance. These interesting bio-electrode arrays offer potential possibilities of application as electrocatysts in direct ethanol biofuel cells.

Immobilization of Cobalt Phthalocyanine and Tetrasulfophthalocyanine onto MCM-41 and MCM-48: Effect of Immobilization Method on Catalytic Activity

Cobalt tetrasulfophthalocyanine (CoPcS) was chemically anchored to amine-modified MCM-41 and MCM-48 surface. These mesoporous silica were prepared by hydrothermal procedure. Physical mixtures of CoPc in MCM-41 and in MCM-48 were also prepared for comparison purposes. The four prepared catalysts, 10 wt.% CoPcS/NH2-MCM-41, 10 wt.% CoPcS/NH2-MCM-48, 10 wt.% CoPc/MCM-41 and 10 wt.% CoPc/MCM-48, were characterized by X-ray diffractometry (XRD), diffuse reflectance UV-Vis spectroscopy and BET specific surface analysis. The catalytic activity of the immobilized catalysts was tested in the aerobic epoxidation of cyclohexene. CoPcS/NH2-MCM-41 and CoPcS/NH2-MCM-48 showed relatively high epoxide selectivity but low conversion of cyclohexene compared to CoPc/MCM-41 and CoPc/MCM-48. No leaching of metallophthalocyanine from the catalysts immobilized by chemical bonding into the reaction medium was observed and these catalysts could be reused four times.

Parameters Affecting the Performance of Immobilized Enzyme

Enzyme immobilization has been investigated to improve lipase properties over the past few decades. Different methods and various carriers have been employed to immobilize enzyme. However, the application of enzymatic technology in large scale is rarely seen during the industrial process. The main obstacles are a high cost of the immobilization and the poor performance of immobilized lipase. This review focuses on the current status of enzyme immobilization, which aims to summarize the latest research on the parameters affecting the performance of immobilized enzyme. Particularly, the effect of immobilization methods, immobilization carriers, and enzyme loading has been discussed.

In situ product removal of ketoses by immobilized 3-amino phenyl boronic acid: effect of immobilization method on pH profile.

The use of polymeric derivatives of phenylboronic acid (PBA) as an effective means for specific in situ product removal of ketoses from aldose-containing reaction mixtures, strongly depends on the retention of selective binding of ketoses exhibited by soluble PBA and 3-amino PBA, by their polymeric, water insoluble analogs. In this communication we demonstrate that immobilization chemistry has a strong effect on ketose preferred binding by polymeric PBA derivatives. Our results indicate that for the preparation of an effective and more specific adsorbent, 3-amino PBA should be coupled to the polymeric carrier via alkylamino chemistry and not via the commonly employed amido derivative. Immobilized alkylamino-PBA exhibited selective fructose and xylulose binding throughout glucose and xylose isomerization processes at the pH range of 7.0-8.0.