scholarly journals Peculiarities of Synthesis and Properties of Lignin–Silica Nanocomposites Prepared by Sol-Gel Method

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 950 ◽  
Author(s):  
Tetyana Budnyak ◽  
Selda Aminzadeh ◽  
Ievgen Pylypchuk ◽  
Anastasia Riazanova ◽  
Valentin Tertykh ◽  
...  
Keyword(s):  
Hybrid Materials ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
2D Nmr ◽  
Physicochemical Characteristics ◽  
Size Exclusion ◽  
Silica Network ◽  
Silica Nanocomposites ◽  
Air Atmosphere ◽  
Exclusion Chromatography

The development of advanced hybrid materials based on polymers from biorenewable sources and mineral nanoparticles is currently of high importance. In this paper, we applied softwood kraft lignins for the synthesis of lignin/SiO2 nanostructured composites. We described the peculiarities of composites formation in the sol-gel process through the incorporation of the lignin into a silica network during the hydrolysis of tetraethoxysilane (TEOS). The initial activation of lignins was achieved by means of a Mannich reaction with 3-aminopropyltriethoxysilane (APTES). In the study, we present a detailed investigation of the physicochemical characteristics of initial kraft lignins and modified lignins on each step of the synthesis. Thus, 2D-NMR, 31P-NMR, size-exclusion chromatography (SEC) and dynamic light scattering (DLS) were applied to analyze the characteristics of pristine lignins and lignins in dioxan:water solutions. X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) were used to confirm the formation of the lignin–silica network and characterize the surface and bulk structures of the obtained hybrids. Termogravimetric analysis (TGA) in nitrogen and air atmosphere were applied to a detailed investigation of the thermal properties of pristine lignins and lignins on each step of modification. SEM confirmed the nanostructure of the obtained composites. As was demonstrated, the activation of lignin is crucial for the sol-gel formation of a silica network in order to create novel hybrid materials from lignins and alkoxysilanes (e.g., TEOS). It was concluded that the structure of the lignin had an impact on its reactivity during the activation reaction, and consequently affected the properties of the final hybrid materials.

Pd/SiO2 Organic-Inorganic Hybrid Materials by Sol-Gel Method: Preparation and Thermal Stability under H2 Atmosphere

2015 ◽  
Vol 1118 ◽  
pp. 20-27
Author(s):  
Jing Yang ◽  
Bao Song Li ◽  
Xiang Huo ◽  
Hao Xu ◽  
Hai Yun Hou
Keyword(s):  
Thermal Stability ◽  
Calcination Temperature ◽  
Hybrid Materials ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Inorganic Hybrid ◽  
X Ray ◽  
Good Thermal Stability ◽  
Pd Doping

Pd/SiO2 organic-inorganic hybrid materials were prepared by adding PdCl2 into methyl-modified silica sol. The Pd/SiO2 hybrid materials were characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of calcination temperature and Pd-doping on the phase transition of Pd element and the thermal stability of CH3 group in the Pd/SiO2 organic-inorganic hybrid materials were investigated. The results showed that the reduced metallic Pd0 exhibits good thermal stability under H2 atmosphere in the calcination process. Pd element in noncalcined Pd/SiO2 materials exists in PdCl2 form, calcination at 200 °C in a H2 atmosphere produces some metallic Pd0 and calcinations at 350 °C results in the complete transformation of Pd2+ to metallic Pd0. With the increase of calcination temperature, the Pd0 particle sizes increase and the hydrophobic Si−CH3 bands decrease in intensity. As the calcination temperature is greater than or equal to 350 °C, the loading of metallic Pd0 nearly has no influence on the chemical structure but, with the increase of Pd content, the formed Pd0 particle size increases. To keep the hydrophobicity of Pd/SiO2 membrane materials, the optimal calcination temperature is about 350 °C under H2 atmosphere.

scholarly journals Modeling the Properties of Curcumin Derivatives in Relation to the Architecture of the Siloxane Host Matrices

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 267
Author(s):  
Florentina Monica Raduly ◽  
Valentin Rădiţoiu ◽  
Alina Rădiţoiu ◽  
Adriana Nicoleta Frone ◽  
Cristian Andi Nicolae ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Optical Properties ◽  
Hybrid Materials ◽  
Sol Gel ◽  
Alcoholic Solution ◽  
Silica Network ◽  
Bioactive Coatings ◽  
Curcumin Derivatives ◽  
Optical Films ◽  
Host Matrices

Research in the field of natural dyes has constantly focused on methods of conditioning curcumin and diversifying their fields of use. In this study, hybrid materials were obtained from modified silica structures, as host matrices, in which curcumin dyes were embedded. The influence of the silica network structure on the optical properties and the antimicrobial activity of the hybrid materials was monitored. By modifying the ratio between phenyltriethoxysilane:diphenyldimethoxysilane (PTES:DPDMES), it was possible to evaluate the influence the organosilane network modifiers had on the morphostructural characteristics of nanocomposites. The nanosols were obtained by the sol–gel method, in acid catalysis. The nanocomposites obtained were deposited as films on a glass support and showed a transmittance value (T measured at 550 nm) of around 90% and reflectance of about 11%, comparable to the properties of the uncovered support. For the coatings deposited on PET (polyethylene terephthalate) films, these properties remained at average values of T550 = 85% and R550 = 11% without significantly modifying the optical properties of the support. The sequestration of the dye in silica networks reduced the antimicrobial activity of the nanocomposites obtained, by comparison to native dyes. Tests performed on Candida albicans fungi showed good results for the two curcumin derivatives embedded in silica networks (11–18 mm) by using the spot inoculation method; in comparison, the alcoholic dye solution has a spot diameter of 20–23 mm. In addition, hybrids with the CA derivative were the most effective (halo diameter of 17–18 mm) in inhibiting the growth of Gram-positive bacteria, compared to the curcumin derivative in alcoholic solution (halo diameter of 21 mm). The results of the study showed that the presence of 20–40% by weight DPDMES in the composition of nanosols is the optimal range for obtaining hybrid films that host curcumin derivatives, with potential uses in the field of optical films or bioactive coatings.

Arsenic Removal via Cellulose-Based Organic/Inorganic Hybrid Materials from Drinking Water

2012 ◽  
Vol 730-732 ◽  
pp. 563-568
Author(s):  
Catarina Martins ◽  
Rui F. Duarte ◽  
Maria C.F. Magalhães ◽  
Dmitry Evtuguin
Keyword(s):  
Aqueous Solutions ◽  
Hybrid Materials ◽  
Arsenic Removal ◽  
Sol Gel ◽  
Arsenic Concentration ◽  
Cellulose Fiber ◽  
Silica Network ◽  
Bleached Pulp ◽  
Removal Of Arsenic

Cellulose/silica derived hybrids materials (CSH), functionalized with aluminium, calcium, and propylammonium ions, were tested for their possible use in the removal of arsenic from aqueous solutions with controlled compositions to levels lower than 10 μg As/L. CSH were synthesized by sol-gel method using bleached pulp, as source of cellulose fiber, and tetraethoxysilane (TEOS) as main silica precursor. The silica network, made in situ, contained various anchored cations such as propylammonium (CSH-PA), aluminium (CSH-Al) and, calcium (CSH-Ca). Thin films or mesoparticles of silica were deposited on cellulose fibers as shown by SEM and XRD. These hybrid materials were immersed in controlled ionic strength aqueous solutions with arsenic concentrations lower than 0.2 mg As/L. The best performance was shown by CSH-PA that was able to remove a maximum of 20 % of the total arsenic concentration.

Extraction products from var. ‘Soranovskii’

2015 ◽  
Vol 69 (11) ◽  
Author(s):  
Sergey G. Il’yasov ◽  
Viktor A. Cherkashin ◽  
Gennady V. Sakovich ◽  
Dmitri A. Parkhomenko
Keyword(s):  
Analytical Techniques ◽  
2D Nmr ◽  
Size Exclusion ◽  
Gas Chromatography Mass Spectrometry ◽  
Polar Solvents ◽  
Chemical Structures ◽  
Organosolv Lignin ◽  
Lignocellulosic Feedstock ◽  
Exclusion Chromatography ◽  
Thermobaric Conditions

AbstractThe chemical structures of Miscanthus var. ‘Soranovskii’ lignin fractions released via extraction of lignin from the lignocellulosic feedstock using moderately heated acetone under atmospheric pressure, without acidic and alkaline catalysts, were studied. A blend of Miscanthus stems and leaves was pretreated with water under thermobaric conditions. The acetone organosolv process subsequently afforded a substance related to a lignin-like matter-acetone organosolv Miscanthus lignin (AOML). Non-destructive analytical techniques such as FTIR spectroscopy, gas chromatography-mass spectrometry, size-exclusion chromatography, and 2D NMR were used. The IR and NMR spectroscopies revealed the AOML structure to comprise all the three major types of phenylpropane units: guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H). The resultant acetone-organosolv lignin exhibits good solubility in polar solvents, moderate solubility in aromatic chemicals, and is insoluble in non-polar solvents, exhibiting the physicochemical properties of a thermoplastic polymer with a softening point of 67.0°C (onset 33.0°C, endset 81.5°C).

scholarly journals Enzyme Catalyzed Copolymerization of Lignosulfonates for Hydrophobic Coatings

2021 ◽  
Vol 9 ◽  
Author(s):  
Sebastian A. Mayr ◽  
Nikolaus Schwaiger ◽  
Hedda K. Weber ◽  
Janez Kovač ◽  
Georg M. Guebitz ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Value Added ◽  
Coupling Reaction ◽  
Size Exclusion ◽  
Water Contact ◽  
Hydrophobic Coatings ◽  
Swelling Capacity ◽  
Exclusion Chromatography ◽  
Insoluble Polymers

Enzymatic polymerization of lignin can generate a variety of value-added products concomitantly replacing fossil-based resources. In line with this approach, a laccase from the thermophilic fungus Myceliophthora thermophila (MtL) was used to couple a hydrophobicity enhancing fluorophenol (FP) molecule, namely 4-[4-(trifluoromethyl)phenoxy]phenol (4,4-F3MPP), as a model substrate onto lignosulfonate (LS). During the coupling reaction changes in fluorescence, phenol content, viscosity and molecular weight (size exclusion chromatography; SEC) were monitored. The effects of enzymatic coupling of FP onto LS on hydrophobicity were investigated by the means of water contact angle (WCA) measurement and determination of swelling capacity. Full polymerization of LS resulting in the production of water-insoluble polymers was achieved at a pH of 7 and 33°C. Incorporation of 2% (w/v) of FP led to an increase in WCA by 59.2% while the swelling capacity showed a decrease by 216.8%. Further, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis indicated successful covalent coupling of the FP molecule onto LS by an emerging peak at 1,320 cm–1 in the FTIR spectrum and the evidence of Fluor in the XPS spectrum. This study shows the ability of laccase to mediate the tailoring of LS properties to produce functional polymers.

scholarly journals Synthesis of Polysilsesquioxanes with Double-Decker Silsesquioxane Repeating Units

2016 ◽  
Vol 8 (2) ◽  
pp. 217-227 ◽  
Author(s):  
M. A. Hoque ◽  
Y. Kawakami
Keyword(s):  
Thermal Properties ◽  
Size Exclusion Chromatography ◽  
1H Nmr ◽  
Nitrogen Atmosphere ◽  
Size Exclusion ◽  
29Si Nmr ◽  
Air Atmosphere ◽  
Double Decker ◽  
Average Residual ◽  
Exclusion Chromatography

Polysilsesquioxanes were synthesized with end functional double-decker silsesquioxanes (DDSQ) and the polymers were characterized with 1H NMR, 29Si NMR and size exclusion chromatography (SEC). Polysilsesquioxane containing iso-butyl end capped DDSQ showed better solubility compared to that of methyl end capped DDSQ. Thermal properties investigated with TGA showed that the polymers exhibited exceptionally high stabilities in the range of 470-530°C even in both nitrogen and air atmosphere. The average residual weights of the polymers at 760°C were around 80% in the nitrogen atmosphere.

scholarly journals Characterization of the Hydrolysis Kinetics of Fucosylated Glycosaminoglycan in Mild Acid and Structures of the Resulting Oligosaccharides

Marine Drugs ◽  
2020 ◽  
Vol 18 (6) ◽  
pp. 286 ◽  
Author(s):  
Xixi Liu ◽  
Zhexian Zhang ◽  
Hui Mao ◽  
Pin Wang ◽  
Zhichuang Zuo ◽  
...  
Keyword(s):  
Acid Hydrolysis ◽  
2D Nmr ◽  
Size Exclusion ◽  
Structure Characteristic ◽  
Degree Of Hydrolysis ◽  
2D Nmr Spectroscopy ◽  
Molecular Weights ◽  
Kinetic Rate Constants ◽  
Exclusion Chromatography ◽  
Mild Acid

Mild acid hydrolysis is a common method for the structure analysis of fucosylated glycosaminoglycan (FG). In this work, the effects of acid hydrolysis on the structure of FG from S. variegatus (SvFG) and the reaction characteristic were systemically studied. The degree of defucosylation (DF) and molecular weights (Mw) of partial fucosylated glycosaminoglycans (pFs) were monitored by 1H NMR and size-exclusion chromatography, respectively. The kinetic plots of DF, degree of desulfation (DS) from fucose branches, and degree of hydrolysis (DH) of the backbone are exponentially increased with time, indicating that acid hydrolysis of SvFG followed a first-order kinetics. The kinetic rate constants kDF, kDS, and kDH were determined to be 0.0223 h-1, 0.0041 h-1, and 0.0005 h-1, respectively. The structure of the released sulfated fucose branches (FucS) from SvFG and HfFG (FG from H. fuscopunctata) was characterized by 1D/2D NMR spectroscopy, suggesting the presence of six types of fucose: α/β Fuc2S4S, Fuc3S4S, Fuc3S, Fuc4S, Fuc2S, and Fuc. The Fuc3S4S was more susceptible to acid than Fuc2S4S, and that the sulfate ester in position of O-2 and O-3 than in O-4 of fucose. The structure characteristic of pF18 indicated the cleavage of backbone glycosidic bonds. The APTT prolonged activity reduced with the decrease of the DF and Mw of the pFs, and became insignificant when its DF was 87% with Mw of 3.5 kDa.

scholarly journals Microstructure and Thermomechanical Properties of Polyimide-Silica Nanocomposites

2006 ◽  
Vol 2006 ◽  
pp. 1-9 ◽  
Author(s):  
A. Al Arbash ◽  
Z. Ahmad ◽  
F. Al-Sagheer ◽  
A. A. M. Ali
Keyword(s):  
Sol Gel ◽  
Thermomechanical Properties ◽  
Silica Content ◽  
Hydroxyl Groups ◽  
Thermal Coefficient ◽  
Silica Network ◽  
Interphase Interaction ◽  
Silica Nanocomposites ◽  
Sol Gel Process ◽  
Alkoxy Groups

Novel polyimide-silica nanocomposites with interphase chemical bonding have been prepared using the sol-gel process. The morphology, thermal and mechanical properties were studied as a function of silica content and compared with the similar composites having no interphase interaction. The polyimide precursors, polyamic acids (PAAs) with or without pendant hydroxyl groups were prepared from the reaction of pyromellitic dianhydride with a mixture of oxydianiline and 1,3 phenylenediamine or 2,4-diminophenol in dimethylacetamide. The PAA with pendant hydroxyl groups was reacted with isocyanatopropyltriethoxysilane to produce alkoxy groups on the chain. The reinforcement of PAA matrices with or without alkoxy groups on the chain was carried out by mixing appropriate amount of tetraethoxysilane (TEOS) and carrying out its hydrolysis and condensation in a sol-gel process. Thin hybrid films were imidized by successive heating up to 300C∘. The presence of alkoxy groups on the polymer chain and their cocondensation with TEOS developed the silica network which was interconnected chemically with the polyimide matrix. SEM studies show a drastic decrease in the silica particle size in the chemically bonded system. Higher thermal stability and mechanical strength, improved transparency, and low values of thermal coefficient of expansion were observed in case of chemically bonded composites.

scholarly journals Photocatalytic and Electrocatalytic Properties of NGr-ZnO Hybrid Materials

Nanomaterials ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1473 ◽  
Author(s):  
Florina Pogacean ◽  
Maria Ştefan ◽  
Dana Toloman ◽  
Adriana Popa ◽  
Cristian Leostean ◽  
...  
Keyword(s):  
Hybrid Materials ◽  
Zno Nanoparticles ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Band Alignment ◽  
Ros Generation ◽  
X Ray ◽  
Electrocatalytic Properties ◽  
Graphene Sample ◽  
Doped Graphene

N-doped graphene-ZnO hybrid materials with different N-doped graphene:ZnO wt% ratios (1:10; 1:20; 1:30) were prepared by a simple and inexpensive sol-gel method. The materials denoted NGr-ZnO-1 (1:10), NGr-ZnO-2 (1:20), and NGr-ZnO-3 (1:30) were investigated with advanced techniques and their morpho-structural, photocatalytic, and electrocatalytic properties were reported. Hence, pure N-doped graphene sample contains flakes with the size ranging from hundreds of nanometers to micrometers. In the case of all NGr-ZnO hybrid materials, the flakes appear heavily decorated with ZnO nanoparticles, having a cauliflower-like morphology. The X-ray powder diffraction (XRD) investigation of N-doped graphene sample revealed that it was formed by a mixture of graphene oxide, few-and multi-layer graphene. After the ZnO nanoparticles were attached to graphene, major diffraction peaks corresponding to crystalline planes of ZnO were seen. The qualitative and quantitative compositions of the samples were further evidenced by X-ray photoelectron spectroscopy (XPS). In addition, UV photoelectron spectroscopy (UPS) spectra allowed the determination of the ionization energy and valence band maxima. The energy band alignment of the hybrid materials was established by combining UV–Vis with UPS results. A high photocatalytic activity of NGr-ZnO samples against rhodamine B solution was observed. The associated reactive oxygen species (ROS) generation was monitored by electron paramagnetic resonance (EPR)-spin trapping technique. In accordance with bands alignment and identification of radical species, the photocatalytic mechanism was elucidated.

scholarly journals Structure of a Rhamnogalacturonan Fragment from Apple Pectin: Implications for Pectin Architecture

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Xiangmei Wu ◽  
Andrew Mort
Keyword(s):  
Galacturonic Acid ◽  
2D Nmr ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Size Exclusion ◽  
Direct Connection ◽  
Apple Pectin ◽  
Nmr Spectrometry ◽  
Exclusion Chromatography ◽  
Rhamnogalacturonan Hydrolase

A commercial apple pectin was sequentially digested with the cloned enzymes endopolygalacturonase, galactanase, arabinofuranosidase, xylogalacturonase, and rhamnogalacturonan hydrolase. The rhamnogalacturonan hydrolase-generated oligosaccharides were separated by ultrafiltration, anion exchange, and size-exclusion chromatography. Fractions from the ion exchange chromatography were pooled, lyophilized, and screened by MALDI-TOF MS. An oligosaccharide (RGP14P3) was identified and its structure, α-D-GalpA-(1→2)-α-L-Rhap-(1→4)-α-D-GalpA-(1→2)-α-L-Rhap-(1→4)-α-D-GalpA, determined by 1D and 2D NMR spectrometry. This oligosaccharide probably represents a direct connection between homogalacturonan and rhamnogalacturonan in pectin. Alternatively, it could indicate that the nonreducing end of rhamnogalacturonan starts with a galacturonic acid residue.

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