Rapid in-situ growth of enzyme-mimicking Pd nanoparticles on TEMPO-oxidized nanocellulose for the efficient detection of ascorbic acid.

Rapid, efficient and green method of Pd nanoparticles (PdNPs) synthesis on TEMPO-oxidized cellulose nanofibril (TCNF) is demonstrated here. The nanohybrid (PdNPs/TCNF) exhibited peroxidase and oxidase-like activities evident by the oxidation of three chromogenic substrates. Enzyme kinetic studies using 3,3',5,5'-Tetramethylbenzidine (TMB) oxidation uncovered the excellent kinetic parameters (low Km and high Vmax) and good specific activities of 215 U/g and 107 U/g for peroxidase and oxidase-like activities, respectively. A colorimetric assay for ascorbic acid (AA) detection is proposed based on its ability to reduce oxidized TMB to its colorless form. However, presence of nanozyme caused re-oxidation of TMB to its blue colored form within few minutes resulting in time limitation and inaccurate detection. Thanks to the film forming nature of TCNF; this limitation was overcome by employing PdNPs/TCNF film strips that can be easily removed before AA addition. The assay allowed AA detection in the linear range of 0.25-10 µM with a detection limit of 0.039 µM. The results of AA detection in commercial beverages and vitamin C tablets are matching with the specified values. Further the nanozyme exhibited high tolerance to pH (2-10) and temperature (up to 80 °C) and good recyclability for five cycles.

Effective fabrication of cellulose nanofibrils supported Pd nanoparticles as a novel nanozyme with peroxidase and oxidase-like activities for efficient dye degradation.

Nanozyme-based dye degradation methods are promising for the remediation of water pollution. Though Pd nanoparticles (PdNPs) are known to act as nanozymes, their dye degradation capability has not been investigated. Low nanozyme activities, easy aggregation, difficulties in recovery and reuse are the major challenges in achieving this. For the first time, cellulose nanofibrils-supported PdNPs (PdNPs/PCNF) as a novel nanozyme with good peroxidase and oxidase-mimicking activities and easy recyclability is explored for dye degradation. An efficient and rapid method of PdNPs/PCNF preparation was demonstrated by adjusting the pH and microwave irradiation. Enzyme kinetic studies revealed good kinetic parameters and specific activities of 415 and 277 U/g for peroxidase and oxidase, respectively. PdNPs/PCNF offered 99.64% degradation of methylene blue within 12 min (0.468 min-1) with 0.4 M H2O2 at pH 5.0. Mechanistic studies revealed the involvement of hydroxyl and superoxide radicals. Owing to the network-like structure of PCNF, films and foams were prepared, their dye degradation potentials were compared, and recyclability was tested. Successful degradation of mixed dye solutions and spiked real water samples was achieved and a continuous flow method was demonstrated using a foam-packed column.

Preparation and Characterization of Polybutylene Succinate Reinforced with Pure Cellulose Nanofibril and Lignocellulose Nanofibril Using Two-Step Process.

This study reports the preparation of a polybutylene succinate (PBS) film reinforced with pure cellulose nanofibril (PCNF) and lignocellulose nanofibril (LCNF) by a two-step process that consists of solvent dispersion and twin-screw extrusion. Compared to the conventional one-step process, this method offered improved mechanical properties. The addition of 5% CNF increased the tensile properties up to 18.8%. Further, the effect of the lignin content was also studied by using LCNF as a reinforcement. The LCNF was prepared with and without a deep eutectic solvent (DES) pretreatment to gain LCNF with a lignin content that varied between 5, 19, and 30%. The mechanical properties results show that a 5% addition of LCNF to the PBS matrix increased its tensile strength and elastic modulus. Further, the morphological and thermal properties of the composites were also studied in detail.

Wet-Spun Composite Filaments from Lignocellulose Nanofibrils/Alginate and Their Physico-Mechanical Properties.

Lignocellulose nanofibrils (LCNFs) with different lignin contents were prepared using choline chloride (ChCl)/lactic acid (LA), deep eutectic solvent (DES) pretreatment, and subsequent mechanical defibrillation. The LCNFs had a diameter of 15.3-18.2 nm, which was similar to the diameter of commercial pure cellulose nanofibrils (PCNFs). The LCNFs and PCNFs were wet-spun in CaCl2 solution for filament fabrication. The addition of sodium alginate (AL) significantly improved the wet-spinnability of the LCNFs. As the AL content increased, the average diameter of the composite filaments increased, and the orientation index decreased. The increase in AL content improved the wet-spinnability of CNFs but deteriorated the tensile properties. The increase in the spinning rate resulted in an increase in the orientation index, which improved the tensile strength and elastic modulus.

Preparation and Characterization of Cellulose Acetate Film Reinforced with Cellulose Nanofibril.

In this study, cellulose acetate (CA)/cellulose nanofibril (CNF) film was prepared via solvent casting. CNF was used as reinforcement to increase tensile properties of CA film. CNF ratio was varied into 3, 5, and 10 phr (parts per hundred rubbers). Triacetin (TA) and triethyl citrate (TC) were used as two different eco-friendly plasticizers. Two different types of solvent, which are acetone and N-methyl-2-pyrrolidone (NMP), were also used. CA/CNF film was prepared by mixing CA and CNF in acetone or NMP with 10% concentration and stirred for 24 h. Then, the solution was cast in a polytetrafluoroethylene (PTFE) dish followed by solvent evaporation for 12 h at room temperature for acetone and 24 h at 80 °C in an oven dryer for NMP. The effect of solvent type, plasticizers type, and CNF amount on film properties was studied. Good dispersion in NMP was evident from the morphological study of fractured surface and visible light transmittance. The results showed that CNF has a better dispersion in NMP which leads to a significant increase in tensile strength and elastic modulus up to 38% and 65%, respectively, compared with those of neat CA. CNF addition up to 5 phr loading increased the mechanical properties of the film composites.

Esterification of Lignin Isolated by Deep Eutectic Solvent Using Fatty Acid Chloride, and Its Composite Film with Poly(lactic acid).

In this study, the effect of lignin esterification with fatty acid chloride on the properties of lignin and lignin/poly(lactic acid) (PLA) composites was investigated. Lignocellulose (Pinus densiflora S. et Z.) was treated using a deep eutectic solvent (DES) with choline chloride (ChCl)/lactic acid (LA). From the DES-soluble fraction, DES-lignin (DL) was isolated by a regeneration process. Lignin esterification was conducted with palmitoyl chloride (PC). As the PC loading increased for DL esterification, the Mw of esterified DL (EDL) was increased, and the glass transition temperature (Tg) was decreased. In DL or EDL/PLA composite films, it was observed that EDL/PLA had cleaner and smoother morphological characteristics than DL/PLA. The addition of DL or EDL in a PLA matrix resulted in a deterioration of tensile properties as compared with neat PLA. The EDL/PLA composite film had a higher tensile strength and elastic modulus than the DL/PLA composite film. DL esterification decreased water absorption with lower water diffusion coefficients. The effect of lignin esterification on improving the compatibility of lignin and PLA was demonstrated. These results are expected to contribute to the development of high-strength lignin composites.

Preparation and Properties of Wet-Spun Microcomposite Filaments from Various CNFs and Alginate.

We aimed to improve the mechanical properties of alginate fibers by reinforcing with various cellulose nanofibrils (CNFs). Pure cellulose nanofibril (PCNF), lignocellulose nanofibril (LCNF) obtained via deep eutectic solvent (DES) pretreatment, and TEMPO-oxidized lignocellulose nanofibril (TOLCNF) were employed. Sodium alginate (AL) was mixed with PCNF, LCNF, and TOLCNF with a CNF content of 5-30%. To fabricate microcomposite filaments, the suspensions were wet-spun in calcium chloride (CaCl2) solution through a microfluidic channel. Average diameters of the microcomposite filaments were in the range of 40.2-73.7 µm, which increased with increasing CNF content and spinning rate. The tensile strength and elastic modulus improved as the CNF content increased to 10%, but the addition of 30% CNF deteriorated the tensile properties. The tensile strength and elastic modulus were in the order of LCNF/AL > PCNF/AL > TOLCNF/AL > AL. An increase in the spinning rate improved the tensile properties.

Rapid synchronous synthesis of Ag nanoparticles and Ag nanoparticles/holocellulose nanofibrils: Hg(II) detection and dye discoloration.

A novel microwave-assisted green method that synchronously synthesizes silver nanoparticles (AgNPs) and AgNPs decorated holocellulose nanofibrils (AgNPs/HCNF) within a minute and without using a reducing agent is reported. As obtained nanomaterials were well characterized using various analytical techniques. AgNPs applied as a colorimetric probe for the selective recognition of Hg(II) (linear range 10-200 µg L-1, detection limit 1.16 µg L-1). The probe was able to quantify Hg(II) in spiked tap, bore, and lake water samples and paper strips were developed to facilitate the onsite detection. Furthermore, freeze-drying of the AgNPs/HCNF nanocomposite produced aerogel that served as an excellent catalyst for the reduction of Congo red and methylene blue. The aerogel was easily recovered and reused without a decrease in activity or deterioration of its structure for five cycles. These results indicate the great potential of the AgNPs/HCNF aerogel for waste water treatment and catalytic applications.

Preparation and Characteristics of Wet-Spun Filament Made of Cellulose Nanofibrils with Different Chemical Compositions.

In this study, wet-spun filaments were prepared using lignocellulose nanofibril (LCNF), with 6.0% and 13.0% of hemicellulose and lignin, respectively, holocellulose nanofibril (HCNF), with 37% hemicellulose, and nearly purified-cellulose nanofibril (NP-CNF) through wet-disk milling followed by high-pressure homogenization. The diameter was observed to increase in the order of NP-CNF ≤ HCNF < LCNF. The removal of lignin improved the defibrillation efficiency, thus increasing the specific surface area and filtration time. All samples showed the typical X-ray diffraction pattern of cellulose I. The orientation of CNFs in the wet-spun filaments was observed to increase at a low concentration of CNF suspensions and high spinning rate. The increase in the CNF orientation improved the tensile strength and elastic modulus of the wet-spun filaments. The tensile strength of the wet-spun filaments decreased in the order of HCNF > NP-CNF > LCNF.

Adsorption Characteristics of Ag Nanoparticles on Cellulose Nanofibrils with Different Chemical Compositions.

The adsorption characteristics of silver nanoparticles (AgNPs) on cellulose nanofibrils (CNFs) were investigated herein with different chemical compositions. Pure cellulose nanofibers (PCNFs), lignocellulose nanofibers (LCNFs) with different lignin contents (LCNF-20% and LCNF-31%), and holocellulose nanofibers (HCNFs) with hemicellulose were used in this study. Furthermore, CNFs and silver nitrate were mixed and reacted at different temperatures, and NaBH4 was used as the reducing agent. First, the effect of temperature on the adsorption of AgNPs on PCNF was studied. At an optimal temperature (45 °C), the effect of the chemical composition of CNF was studied. The overall properties were analyzed using UV-vis spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The AgNPs were found to be spherical under all conditions with average diameter of 5.3 nm (PCNF), 5.6 nm (HCNF), 6.3 nm (LCNF-20%) and 6.6 nm (LCNF-31%). The amount of AgNPs adsorbed on the CNF was observed to vary, based on the chemical composition of the CNF. The adsorption amount of AgNPs was observed to increase in the order of LCNF-20% > PCNF > LCNF-31% > HCNF. The results indicated that phenolic hydroxyl groups present in LCNF significantly affected the adsorption of AgNPs.

Effect of Lignin Plasticization on Physico-Mechanical Properties of Lignin/Poly(Lactic Acid) Composites.

Kraft lignin (KL) or plasticized KL (PKL)/poly(lactic acid) (PLA) composites, containing different lignin contents and with and without the coupling agent, were prepared in this study using twin-screw extrusion at 180 °C. Furthermore, ε-caprolactone and polymeric diphenylmethane diisocyanate (pMDI) were used as a plasticizer of KL and a coupling agent to improve interfacial adhesion, respectively. It was found that lignin plasticization improved lignin dispersibility in the PLA matrix and increased the melt flow index due to decrease in melt viscosity. The tensile strength of KL or PKL/PLA composites was found to decrease as the content of KL and PKL increased in the absence of pMDI, and increased due to pMDI addition. The existence of KL and PKL in the composites decreased the thermal degradation rate against the temperature and increased char residue. Furthermore, the diffusion coefficient of water in the composites was also found to decrease due to KL or PKL addition.

Influence of Lignin and Polymeric Diphenylmethane Diisocyante Addition on the Properties of Poly(butylene succinate)/Wood Flour Composite.

Poly(butylene succinate) (PBS)/wood flour (WF) composites with different WF content were prepared by twin-screw extrusion at 160 °C. With increasing WF content, the tensile strength of the PBS/WF composite without polymeric diphenylmethane diisocyante (pMDI) decreased, while that of the composite with pMDI increased. The addition of kraft lignin (KL) deteriorated the tensile properties of the composites both with and without pMDI. The melt flow index (MFI) decreased with increasing WF content, but increased with increasing KL content. The addition of pMDI caused an increase in the melt viscosity of the PBS/WF and PBS/WF/KL composites, resulting in a decrease in the MFI. The composites had lower thermal stability than neat PBS. The exotherms of the PBS/WF (50/50) composite appeared at a higher temperature than that of the neat PBS, but the PBS/WF/KL (50/50/20) composites had similar exotherms as the neat PBS. The addition of KL caused a decrease in the crystallization rate of PBS.

Effects of pH on Nanofibrillation of TEMPO-Oxidized Paper Mulberry Bast Fibers.

TEMPO oxidation was conducted as a pretreatment to achieve efficient nanofibrillation of long paper mulberry bast fibers (PMBFs). The pH dependency of nanofibrillation efficiency and the characteristics of the resulting cellulose nanofibrils (CNFs) were investigated. As the pH increased, the negative value of the zeta potential of TEMPO-oxidized fibers increased. The increase in electrostatic repulsion at pH values of greater than 9 prevented the entanglement of long PMBFs, which was a drawback for defibrillation at acidic pH. With increasing pH, the CNF production yield was increased. The crystallinity index of TEMPO-oxidized CNFs from PMBFs was 83.5%, which was higher than that of TEMPO-oxidized CNFs from softwood fibers in the same conditions. The tensile strength of nanopaper from TEMPO-oxidized PMBF CNFs was 110.18 MPa, which was approximately 30% higher than that (84.19 MPa) of the TEMPO-oxidized CNFs from softwood fibers.

Chlamydomonas angulosa (Green Alga) and Nostoc commune (Blue-Green Alga) Microalgae-Cellulose Composite Aerogel Beads: Manufacture, Physicochemical Characterization, and Cd (II) Adsorption.

This study presents composite aerogel beads prepared by mixing dissolved cellulose with Chlamydomonas angulosa and Nostoc commune cells, respectively, at 0.1, 0.3, and 0.5% (w/w). The manufactured composites (termed regenerated cellulose (RC)), with C. angulosa (RCCA-(1, 3, and 5)), and with N. commune (RCNC-(1, 3, and 5)) were analyzed. Both RCCA-5 and RCNC-5 showed the high specific surface area to be about 261.3 and 332.8 m²·g-1. In the microstructure analysis, network structures were observed in the cross-sections of RC, RCCA-5, and RCNC-5. The pyrolysis temperature of the RCCA-5 and RCNC-5 composite aerogel beads was rapidly increased about 250 °C during the mixing of cellulose with C. angulosa and N. commune. The chemical analysis of RC, RCCA-5, and RCNC-5 showed peaks corresponding to various functional groups, such as amide, carboxyl, and hydroxyl groups from protein, lipid, and carbohydrate. RCNC-5 at pH 6 demonstrated highest Cd2+ removal rate about 90.3%, 82.1%, and 63.1% at 10, 25, and 50 ppm Cd2+, respectively. At pH 6, Cd2+ adsorption rates per unit weight of the RCNC-5 were about 0.9025, 2.0514, and 3.1547 mg/g at 10, 25, and 50 ppm, respectively. The peaks assigned to the amide, carboxyl, and hydroxyl groups in RCCA-5, RCNC-5, and RC were shifted or disappeared immediately after adsorption of Cd2+. The specific surface area, total pore volume, and mean pore diameter of composites was decreased due to adsorption of Cd2+ on the developed materials. As can be seen in the X-ray powder diffraction (XRD) spectrum, significant changes in the molecular structure of the composite aerogel beads were not observed even after adsorption of Cd2+.

Cellulose⁻Chitosan Antibacterial Composite Films Prepared from LiBr Solution.

Cellulose and chitosan solutions were prepared in 60% LiBr and mixed with a different weight ratio. The washing and drying of the prepared cellulose⁻chitosan composite films were performed under identical conditions. The color of the liquefied mixtures and films was initially transparent but changed from colorless to brownish yellow depending on the ratio of chitosan in the solution. The cross section observed in the SEM results indicated that the film developed with a higher ratio of chitosan was more robust and possessed greater antibacterial properties. FT-IR analysis of the films showed that hydrogen bonds between cellulose and chitosan in composite films were successfully achieved and retained excellent mechanical properties. The proper ratio of chitosan in the cellulose solution can increase the tensile strength and improve the elongation of the films; however, the E-modulus property was consistently reduced. The antibacterial activity and mechanical properties of the films were greatly improved as the amount of chitosan in the film increased.

Structure and thermal behavior of a cellulose I-ethylenediamine complex.

We prepared highly crystalline samples of a cellulose I-ethylenediamine (EDA) complex by immersing oriented films of algal (Cladophora) cellulose microcrystals in EDA at room temperature for a few days. The unit-cell parameters were determined to be a = 0.455, b = 1.133, and c = 1.037 nm (fiber repeat) and gamma = 94.02 degrees. The space group was P2(1). On the basis of unit cell, density, and thermogravimetry analyses, the asymmetric unit is composed of one anhydrous glucose residue and one EDA molecule. The chemical and thermal stabilities of the cellulose I-EDA complex were also investigated by the use of X-ray diffraction. When the cellulose I-EDA complex was immersed in methanol or water at room temperature, cellulose III I or I beta was obtained, respectively. However, immersion in a nonpolar solvent such as toluene did not affect the crystal structure of the complex. The cellulose I-EDA complex was stable up to a temperature of approximately 130 degrees C, whereas the boiling point of EDA is 117 degrees C. This thermal stability of the complex is probably caused by intermolecular hydrogen bonds between EDA molecules and cellulose. When heated above 150 degrees C, the cellulose I-EDA complex decomposed into cellulose I beta.

The antioxidant and cytotoxic activities of Sonchus oleraceus L. extracts.

This study investigated in vitro antioxidant activity of Sonchus oleraceus L. by extraction solvent, which were examined by reducing power, hydroxyl radical-scavenging activity(HRSA) and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assays. 70% MeOH extract had the greatest reducing power while EtOH extract had the greatest HRSA. The antioxidant activity of S. oleraceus extracts was concentration dependent and its IC(50) values ranged from 47.1 to 210.5 microg/ml and IC(50) of 70% MeOH, boiling water and 70% EtOH extracts were 47.1, 52.7 and 56.5 microg/ml, respectively. 70% MeOH extract of S. oleraceus contained the greatest amount of both phenolic and flavonoid contents. The extracts tested had greater nitrite scavenging effects at lower pH conditions. The cytotoxic activity showed that EtOH extract had the best activity against the growth of stomach cancer cell. These results suggest that S. oleraceus extract could be used as a potential source of natural antioxidants.