Chemical Modification Process Research Articles

Analysis of the Nucleation Activity of Wood Fillers for Green Polymer Composites

In this work, the surface of pine wood used as a filler in polypropylene/wood composites was successfully modified by the mercerization process. It is a very significant process because it removes low-molecular components, which improves interactions between the filler and matrix and leads to a better dispersion of the filler in the matrix. Unfortunately chemical treatment may affect nucleation of the lignocellulosic filler. On the basis of XRD results, the transformation of native cellulose I to cellulose II was observed. In the present study, the effect of the mercerisation of pine wood on the nucleation ability of polypropylene was investigated by means of polarising microscopy. The results showed that the chemical modification of pine wood had a significant effect on nucleation activity in polymer composites. This effect is explained by differences in the chemical compositions of wood fibres. The content of simple sugars obtained from the methanolysis and acidic hydrolysis of cellulose and hemicellulose was determined through gas chromatography investigations. It was found for the first time that the formation of transcrystalline structures is possible for composites with a high content of glucose derived from cellulose. It is also worth emphasising that the chemical modification process can lead to cellulose depolymerisation processes and the formation of degradation products with a lower molecular weight. Knowledge of the phenomena taking place in the interphase boundary polymer/ filler is very important because it permits optimisation of the processing, leading to products of target properties.

Preparation and Characterization of Biomass-Derived Advanced Carbon Materials for Lithium-Ion Battery Applications

In this study, carbon-based advanced materials for lithium-ion battery applications were prepared by using soybean waste-based biomass material, through a straightforward process of heat treatment followed by chemical modification processes. Various types of carbon-based advanced materials were developed. Physicochemical characteristics and electrochemical performance of the resultant materials were characterized systematically. Scanning electron microscopy observation revealed that the activated carbon and graphene exhibits wrinkles structures and porous morphology. Electrochemical impedance spectroscopy (EIS) revealed that both activated carbon and graphene-based material exhibited a good conductivity. For instance, the graphene-based material exhibited equivalent series resistance value of 25.9 Ω as measured by EIS. The graphene-based material also exhibited good reversibility and cyclic performance. Eventually, it would be anticipated that the utilization of soybean waste-based biomass material, which is conforming to the principles of green materials, could revolutionize the development of advanced material for high-performance energy storage applications, especially for lithium-ion batteries application.

Fire resistant polyphenols based on chemical modification of bio-derived tannic acid

Utilization of renewable materials for the development of safer and nontoxic flame retardants has been of interest from environmental safety and sustainability perspective. Tannic acid (TA) is an abundantly available bio-based polyphenol that exhibits good intumescence and char forming characteristics upon being subjected to heat. Intumescence and char formation are important prerequisites for certain types of effective flame retardant (FR) additives. However, the potential for utilizing TA as an FR has been limited by its poor thermal stability. A single step chemical modification process that overcomes the limitations of TA while allowing the utilization of its beneficial properties is reported here. TA was crosslinked using interfacial polycondensation with terephthaloyl chloride to yield tannic acid terephthalate (TAT). The complex structure of TAT necessitated the synthesis of several model compounds based on methyl gallate (MG) to facilitate the complete structural characterization of TAT using FTIR and 1H NMR. TAT is thermally stable up to 230 °C (less than 3% weight loss) and shows 30% higher char yield and extremely low heat release capacity (<80 J/g-K) as compared to that for TA. Detailed thermal degradation studies combined with gas phase spectroscopy using thermogravimetric analysis - Fourier-transform infrared spectroscopy (TGA-FTIR) and pyrolysis - gas chromatography - mass spectrometry (Py-GC-MS) provide an understanding of the degradation process. Crosslinked phenolic species enhance char formation in the condensed phase and allow for utilization of these compounds as flame retardant coatings for polymers such as Nylon 66. TAT coating on Nylon 66 fabric significantly impedes flame propagation in the fabric, resulting in quick self-extinguishing behavior and reduced char length in vertical flame tests. Morphological characterization, thermo-oxidation studies and microscale combustion calorimetry (MCC) (at high heating rates) of TAT-coated fabric reveal the beneficial effects of char formation and its direct impact on flame retardancy.

One-pot Synthesis and Surface Modification of Fe3O4 Nanoparticles Using Polyvinyl Alcohol by Coprecipitation and Ultrasonication Methods

Among the various substances developed through nanoparticles, iron oxide (Fe3O4) nanoparticle is one of the substances that have been widely used in various fields such as industry, agriculture, biotechnology and biomedicine. The synthesis of Fe3O4 nanoparticle can be carried out by two methods, consist of chemical and mechanical synthesis methods. Coprecipitation is one of the most commonly used methods for chemical synthesis. Fe3O4 compounds are easily oxidized because they are amphoteric. To avoid the continuous oxidation process, chemical modification process should be carried out with the addition of a solution of polyvinyl alcohol (PVA). In this study, PVA-coated Fe3O4 nanoparticles were synthesized by in-situ coprecipitation and ultrasonication methods through direct mixing (one-pot synthesis) of the iron (II) chloride tetrahydrate (FeCl2.4H2O), iron (III) chloride hexahydrate (FeCl3.6H2O), and PVA under alkaline condition. The effects of addition amount of NH3solution (by adjusting its flow rate using automated syringe pump) and PVA concentration were gently studied. Interaction of PVA with Fe3O4 nanoparticle was identified by infrared spectroscopy whereas lattice parameters and crystallite sizes of the synthesized Fe3O4 nanoparticles and PVA-coated Fe3O4 nanoparticles were assessed by X-ray diffraction (XRD).

A novel fabrication method of carbon electrodes using 3D printing and chemical modification process.

Three-dimensional (3D) printing is an emerging technique in the field of biomedical engineering and electronics. This paper presents a novel biofabrication method of implantable carbon electrodes with several advantages including fast prototyping, patient-specific and miniaturization without expensive cleanroom. The method combines stereolithography in additive manufacturing and chemical modification processes to fabricate electrically conductive carbon electrodes. The stereolithography allows the structures to be 3D printed with very fine resolution and desired shapes. The resin is then chemically modified to carbon using pyrolysis to enhance electrochemical performance. The electrochemical characteristics of 3D printing carbon electrodes are assessed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The specific capacitance of 3D printing carbon electrodes is much higher than the same sized platinum (Pt) electrode. In-vivo electromyography (EMG) recording, 3D printing carbon electrodes exhibit much higher signal-to-noise ratio (40.63 ± 7.73) than Pt electrodes (14.26 ± 6.83). The proposed biofabrication method is envisioned to enable 3D printing in many emerging applications in biomedical engineering and electronics.

Hydrophilic and positively charged polyethylenimine-functionalized mesoporous magnetic clusters for highly efficient removal of Pb(II) and Cr(VI) from wastewater

We develop mesoporous magnetic clusters (MMCs) functionalized with hydrophilic branched polyethylenimine (b-PEI), later called b-MG, and MMCs functionalized with positively charged b-PEI (p-MG). These materials efficiently remove Pb(II) and Cr(VI) from wastewater. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and nitrogen adsorption–desorption analysis results clearly indicate that hydrophilic b-PEI and positively charged b-PEI are successfully attached to the MMC surfaces. Wide-angle X-ray diffraction, high-resolution transmission electron microscopy, and field-emission scanning electron microscopy analyses confirm that the crystal structures and morphologies of the MMCs are maintained well even when wet chemical modification processes are used to introduce hydrophilic b-PEI and positively charged b-PEI to the MMC surfaces. Langmuir and Sips isotherm models are applied to describe Pb(II) adsorption behavior of the b-MG and Cr(VI) adsorption behavior of the p-MG. The isotherm models indicate that the maximum adsorption capacities of b-MG and p-MG, respectively, are 216.3 and 334.1 mg g−1, respectively. These are higher than have previously been found for other adsorbents. In reusability tests, using magnetic separation and controlling the pH, the Pb(II) recovery efficiency of the b-MG is 95.6% and the Cr(VI) recovery efficiency of the p-MG is 68.0% even after the third cycle.

Chemical modification of citrus pectin: Structural, physical and rheologial implications

The present study aimed to investigate the physical, structural and rheological modifications caused by the chemical modification process of citrus pectin. Therefore, three commercial citrus pectins with different degree of esterification were chemically modified by sequential alkali and acidic hydrolytic process to produce modified citrus pectins (MCP) with special properties. The molar mass (Mw), degree of esterification (DE), monosaccharide composition, 13C NMR spectra, homogeneity, morphology (SEM) and rheological behavior of both native and modified citrus pectins (MCP) were investigated. The chemical modification reduced the acid uronic content (up to 28.3%) and molar mass (up to 29.98%), however, showed little influence on the degree of esterification of native pectins. Modified citrus pectins presented higher amounts of neutral monosaccharides, mainly galactose, arabinose and rhamnose, typical of the Ramnogalacturonana-I (RG-I) region. Rheological tests indicated that the native and modified citrus pectins presented pseudoplastic behavior, however, the MCP samples were less viscous, compared to the native ones. Modified samples presented better dissolution in water and less strong gels, with good stability during oscillatory shearing at 25°C. This study aims to better understand the implications that chemical modifications may impose on the structure of citrus pectins.

Chemical Modification of Waste Cotton Linters for Oil Spill Cleanup Application

The possibility of use of waste cotton linters as oil sorbents by chemical modification such as acetylation and cyanoethylation was studied. The acetylation process was carried out in presence of acetic anhydride using either H2SO4 or HClO4 as catalyst. The acetylation treatment time was 30, 60 and 120 min and treatment temperature was room temperature, 50 and 70 °C. For cyanoethylation, the waste cotton linters were pre-treated with 2, 5 and 10% NaOH. The treatment temperature for cyanoethylation was room temperature, 50 and 70 °C and treatment time was 30, 60 and 120 min. Both the chemical modification processes were optimized on the basis of oil absorption capacity of the chemically modified cotton fibre with the help of MATLAB software. The modified samples were tested for its oleophilicity in terms of oil absorption capacity, oil retention capacity, oil recovery capacity, reusability of sample and water uptake and buoyancy as oil sorbent. Chemically modified fibres were characterized by Fourier transform infra red spectrophotometer, scanning electron microscope and degree of substitutions.

Cationization of lignocellulose as a means to enhance paper strength properties

Chemical modification by attaching functional groups to lignocellulosic pulp fibers might be a strategy for improving the pulp, and thereby, paper properties. Several studies have described positive effects on paper strength properties for handsheets prepared from cationic-modified pulp or pulp fractions. This study addressed whether these effects are related to the cationic groups, e.g., by increasing electrostatic attraction and thus paper strength, or rather side effects of the chemical modification process, e.g., fiber flexibilization. To eliminate or at least minimize these side effects, only the fines fraction, which was already highly flexible, was cationized. While the addition of cationized fines affected various pulp and paper properties, most notably drainage time, no difference in strength properties was observed when comparing the addition of cationic or unmodified fines to different pulps or fractions thereof.

Nanofiber-structured hydrogel yarns with pH-response capacity and cardiomyocyte-drivability for bio-microactuator application.

A mechanically robust polyacrylonitrile-based nanofibrous hydrogel yarn is fabricated by using a modified electrospinning setup in combination with chemical modification processes. The as-prepared hydrogel yarn possesses a uniaxially aligned nanofiber microarchitecture and supports a rapid, pH-dependent expansion/contraction response within a few seconds. Embryonic cardiomyocytes-seeded hydrogel yarn improves the sarcomere organization and mimics the cardiomyocyte bundles in the native myocardium, which sustains spontaneous cardiomyocyte pumping behaviors. The nanofibrous hydrogel yarn has several advantages over traditional bulk hydrogel scaffolds in terms of robust biomechanics, anisotropic aligned architecture, and superior pH response behaviors. Our nanofibrous hydrogel yarn holds the potential to be developed into novel linear and biological microactuators for various biomedical applications.

Ultra-sensitive aptasensor based on a GQD nanocomposite for detection of hepatitis C virus core antigen

In the present study, by using the aptamer proximity binding assay strategy, a novel electrochemical aptasensor is described for ultrasensitive detection of hepatitis C virus (HCV) core antigen. The immobilization surface is prepared by the modification of a glassy carbon electrode (GCE) with a graphene quantum dots (GQD). GQD were introduced as a novel and suitable substrate for aptamers through π-π stacking interactions, the richness of hydrophilic edges as well as hydrophobic plane in GQD which enhances the aptamer absorption on the electrode surface. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were performed at each stage of the chemical modification process to confirm the resulting surface changes. EIS technique was used as an efficient alternative detection system for HCV core antigen measurement with detection limit 3.3 pg mL−1 and two linear concentration range 10–70 pg mL−1 and 70–400 pg mL−1. Moreover, the fabricated aptasensor could accurately detect HCV core antigen concentration in human serum samples. Such an aptasensor opens a rapid, selective and sensitive route for HCV core antigen detection and provides a promising strategy for potential applications in clinical diagnostics.

Precisely controlled two-step synthesis of cellulose-graft-poly(l-lactide) copolymers: Effects of graft chain length on thermal behavior

This study presented a method to polymerize to cellulose-graft-poly (l-lactide) (cellulose-g-PLLA) copolymers as chemical modification process to overcome disadvantage of melt processing of pristine cellulose due to the strong intermolecular hydrogen bonds. In order to maximize the chain length at the end of cellulose, we designed a precisely controlled polymerization based on a two-step synthesis; 1) short-chain copolymerization of cellulose in an ionic liquid, 2) further graft polymerization in N,N-dimethylformamide and the bulk phase. Accordingly, we could synthesize a copolymer in high yield, with the number of substitutions per glucose unit (DSPLLA) being close to the theoretical maximum value of 3 and the number of lactyl repeating units introduced per glucose unit (MSPLLA) of 212, at a high yield. While the glass transition temperature (Tg) of the copolymer was greatly decreased owing to dissociation of the hydrogen bonds of cellulose and plasticizing effects at a low PLLA content (MSPLLA = 11.2), the Tg gradually increased to attain a value close to that of pure PLLA as the content increased.The cellulose-g-PLLA with low molecular weight was amorphous phase, but the crystallinity started to show from the sample with MSPLLA of 42.0 and WPLLA = 95.0%. As the molecular weight contents of PLLA were increased, the cellulose-g-PLLA of the melting point and the heat of fusion was increased. The cellulose-g-PLLA of the strong inter- and intramolecular hydrogen bonds between the hydroxyl groups was found to affect PLLA crystallinity.

Characterization of VOC emission profile of different wood species during moisture cycles

This study addresses the characterization of volatile organic compounds (VOCs) emitted by samples of 13 different wood species, belonging to both softwoods and hardwoods groups, regularly measured at different intervals of time, after the first measurement on green wood. The same wood specimens were subjected to several cycles of water desorption and adsorption, assuming that moisture variation might play a role in both the formation and emission of VOCs. Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-TOF-MS) was used as a tool to characterize the emission of VOCs. Coupled with a multivariate class-modelling approach, this tool was able to discriminate between groups (softwood and hardwood) and in some cases between different species. However, results showed that the discriminant capacity of VOCs emission to separate species and families rapidly decreases after the first cycles of moisture variation in wood. The green wood was characterized by a richness of volatile compounds, whereas, after only the first dry cycle, wood emitted a more restricted group of compounds. We hypothesized that most of these VOCs might have originated from structural changes and degradation processes that involve the main polymers (particularly hemicellulose) constituting the cell wall of wooden cells. The results obtained are in agreement with the physical and chemical modification processes that characterize wood ageing.

Improved Solid-Phase Synthesis of Phosphorylated Cellulose Microsphere Adsorbents for Highly Effective Pb2+ Removal from Water: Batch and Fixed-Bed Column Performance and Adsorption Mechanism

A highly effective adsorbent with phosphate groups bound to cellulose microspheres was designed by an improved solid-phase modification method to adsorb lead ions from water by a batch and fixed-bed column method. The phosphorylated cellulose microsphere adsorbents were prepared through esterification by which phosphate groups were introduced to the interface of regenerated cellulose microspheres which were previously prepared through a sol–gel transition process from a simple cellulose solution. Their morphological, structural, and physicochemical properties were characterized by SEM, FTIR, XRD, and DSC, etc. Furthermore, EDX and XPS were used to confirm the chemical modification process and to investigate their phosphate adsorption mechanism. In the batch adsorption experiments, the equilibrium time and adsorption capacity were determined by both equilibrium and kinetic adsorption experiments, which were also conducted to investigate the adsorption mechanism. In the dynamic adsorption experiments, multi...

Synthesis of in-situ formable hydrogels with collagen and hyaluronan through facile Michael addition

To mimic the natural extracellular matrix (ECM) and to facilitate tissue regeneration, in-situ formable collagen/hyaluronan composite hydrogels were prepared by a facile approach via Michael addition reaction, with maleilated collagen (Col-MA) and thiol derivatized hyaluronan (HA-SH). The hydrogels were denoted as CHG-1, CHG-2, CHG-3 and CHG-4 by vinyl/free thiol molar ratio (f) of 1:1, 1:2, 1:3 and 1:4, respectively. Results showed that with decrease of the f values, the gelation time decreased from 43s to 15s, Young's modulus increased from 1671.65Pa to 9105.86Pa, and the swelling ratio increased from 1.5 to 12.7. SEM images of the air-dried samples revealed that the chemical modification process did not denature the collagen, and the interwoven collagen fibrils were indeed observed. Cell culture confirmed that the CHG facilitated the growth and proliferation of MC3T3-E1. Cells displayed spreading morphology and formed nearly aligned cell layers with the extension of culture time. Therefore, it is suggested that CHG can be used as injectable materials for tissue regeneration.

Facile Method for Fluorescent Labeling of Starch Nanocrystal

Fluorescently labeled starch nanocrystal (FL-SNC) was synthesized using a simple, low-cost, and scalable two-step chemical modification process. Reactive amino groups were introduced onto the SNC surface through silanization with 3-aminopropyl triethoxysilane (APTES), and fluorescein isothiocyanate (FITC) groups were covalently attached through thiourea. Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, solid-state cross-polarization magic-angle spinning 13C NMR, UV–visible absorbance spectrophotometry, and fluorescence emission spectroscopy confirmed the successful introduction of the fluorescent groups. Transmission electron microscopy and X-ray diffraction data indicated that the dispersibility of FL-SNC was significantly improved, and the original crystallinity and morphology were retained. Compared with a mixture of uncoupled FITC and SNC, covalently connected FL-SNC displayed a more obvious fluorescence intensity and higher photostability. Furthermore, FL-SNC was biocompatib...

Robust superhydrophobic carbon fiber sponge used for efficient oil/corrosive solution mixtures separation

Great challenges are still remained for the oil/water separation in highly acidic, alkaline, and salty environment. Low-cost, eco-friendly and being useful in harsh corrosive environment materials with special wettability are urgently desired to deal with severe environmental and ecological problems arisen from oil spills and organic leakages. Herein, we present a superhydrophobic carbon fiber (CF) sponge with excellent anti-corrosion property and without any chemical modification process was obtained, which can used for efficient oil/corrosive solution mixtures separation. Furthermore, The CF sponge not only can directly and rapidly adsorb oils from water surface, but also can being a superhydrophobic membrane to realize on-demand oil/water separation in highly acidic, alkaline, salty environment by gravity. By virtue of facile and cost-efficient and excellent adsorption/filtration performance in oils/corrosive solutions separation, the unique CF sponge holds great promise of oil spills cleanup and oil/water separation in real harsh environments.

Improved adhesion of Ag NPs to the polyethylene terephthalate surface via atmospheric plasma treatment and surface functionalization

Ag nanoparticles (NPs) have been widely applied, as important antibacterial materials, on textile and polymer surfaces. However, their adhesion to nonreactive polymer surfaces is generally too weak for many applications. Here, we propose a two-step process, atmospheric plasma treatment followed by a surface chemical modification process, which enhances their adhesion to polyethylene terephthalate (PET) surfaces. We found that, compared to either plasma treatments or surface chemical functionalizations, alone, this combination greatly enhanced their adhesion. The plasma treatment resulted in an increase of active sites (OH, CHO and COOH) at the PET surface, permitting increased bonding to 3-aminopropyltriethoxysilane (APTES), whose NH2 groups were then able to form a bonding complex with the Ag NPs.

Vpliv nanotehnološkega postopka kemijske modifikacije na protimikrobno aktivnost in biorazgradljivost tekstilnih vlaken

Vpliv nanotehnološkega postopka kemijske modifikacije na protimikrobno aktivnost in biorazgradljivost tekstilnih vlaken

Increased 5-hydroxymethylcytosine and Ten-eleven Translocation Protein Expression in Ultraviolet B-irradiated HaCaT Cells.

Background:DNA hydroxymethylation refers to a chemical modification process in which 5-methylcytosine (5mC) is catalyzed to 5- hydroxymethylcytosine (5hmC) by ten-eleven translocation (TET) family proteins. Recent studies have revealed that aberrant TETs expression or 5hmC level may play important roles in the occurrence and development of various pathological and physiological processes including cancer and aging. This study aimed to explore the relation between aberrant DNA hydroxymethylation with skin photoaging and to investigate the levels of TETs, 5mC, and 5hmC expression 24 h after 40 mJ/cm2 and 80 mJ/cm2 doses of ultraviolet B (UVB) irradiation to HaCaT cells.Methods:To explore whether aberrant DNA hydroxymethylation is also related to skin photoaging, 40 mJ/cm2 and 80 mJ/cm2 doses of UVB were chosen to treat keratinocytes (HaCaT cells). After 24 h of UVB irradiation, 5mC and 5hmC levels were determined by immunohistochemistry (IHC) and immunofluorescence (IF), and at the same time, the expression levels of matrix metalloproteinase 1 (MMP-1) and TETs were assessed by reverse transcription-polymerase chain reaction or Western blot analysis.Results:After 40 mJ/cm2 and 80 mJ/cm2 doses of UVB exposure, both IHC and IF results showed that 5hmC levels increased significantly, while the 5mC levels did not exhibit significant changes in HaCaT cells, compared with HaCat cells without UVB exposure. Moreover, compared with HaCat cells without UVB exposure, the levels of TET1, TET2, and TET3 mRNA and protein expression were significantly upregulated (mRNA: P = 0.0022 and 0.0043 for TET1; all P < 0.0001 for TET2; all P = 0.0006 for TET3; protein: P = 0.0012 and 0.0006 for TET1; all P = 0.0022 for TET2; and all P = 0.0002 for TET3), and the levels of MMP-1 mRNA expression increased dose dependently in 40 mJ/cm2 and 80 mJ/cm2 UVB-irradiated groups.Conclusion:UVB radiation could cause increased 5hmC and TET expression, which might become a novel biomarker in UVB-related skin aging.