Cellulose Surface Research Articles

Superabsorbent cellulose-based hydrogels cross-liked with borax

Cellulose, the most abundant biopolymer on Earth, has been widely attracted owing to availability, intoxicity, and biodegradability. Environmentally friendly hydrogels were successfully prepared from water hyacinth-extracted cellulose using a dissolution approach with sodium hydroxide and urea, and sodium tetraborate decahydrate (borax) was used to generate cross-linking between hydroxyl groups of cellulose chains. The incorporation of borax could provide the superabsorbent feature into the cellulose hydrogels. The uncross-linked cellulose hydrogels had a swelling ratio of 325%, while the swelling ratio of the cross-linked hydrogels could achieve ~ 900%. With increasing borax concentrations, gel fraction of the cross-linked hydrogels increased considerably. Borax also formed char on cellulose surfaces and generated water with direct contact with flame, resulting in flame ignition and propagation delay. Moreover, the cross-linked cellulose-based hydrogels showed antibacterial activity for gram-positive bacteria (S. aureus). The superabsorbent cross-linked cellulose-based hydrogels prepared in this work could possibly be used for wound dressing, agricultural, and flame retardant coating applications.

Effect of High-Temperature Hydrothermal Treatment on the Cellulose Derived from the Buxus Plant.

Cellulose has attracted considerable attention as the most promising potential candidate raw material for the production of bio-based polymeric materials. In the last decade, significant progress has been made in the production of biopolymers based on different cellulose forms. In this study, cellulose was obtained in an innovative and environmentally friendly way, using boxwood powder. Crude cellulose was obtained by treating Buxus powder with an ethanol–acetic acid–water mixture. Refined cellulose was then obtained by treatment with an acidic sodium hypochlorite solution and alkaline hydrogen peroxide solution. The novel chemistry of cellulose prepared by this method promises to be not only green, but also highly desirable, because of its lower emissions and low cost. It is crucial for the future of the global polymer industry. The refined cellulose was subjected to a high-temperature hydrothermal treatment under two temperatures and time conditions, with temperature gradients of 120, 140, and 160 °C, and time gradients of 1, 2, and 3 h. The samples were subjected to infrared and thermogravimetric analyses. The cellulose undergoes dehydration and thermal degradation reactions during the heat treatment process, and the thermal stability of the residual is enhanced, compared with that of virgin cellulose. Between 120 and 140 °C, the hydroxyl and hypomethyl groups on the surface of cellulose are shed. Groups in the amorphous region of the polymer are the first to be shed. The dehydration reaction reduces the number of free hydroxyl groups on the surface of the cellulose molecules. The dehydration reaction was accelerated by an increase in temperature. Between 140 and 160 °C, the β-(1,4)-glycosidic bond begins to slowly break and some furans are generated. The structure of cellulose undergoes reorganization during thermal treatment. The thermal stability of the modified material is greater than that of untreated cellulose.

Latex-Based Paper Devices with Super Solvent Resistance for On-the-Spot Detection of Metanil Yellow in Food Samples

The following paper presents a construct for a paper-based device which utilizes latex as the hydrophobic material for the fabrication of its hydrophobic barrier, which was deposited onto the cellulose surface either by free-hand or stenciled drawing. This method demands the least amount of expertise and time from its use, enabling a simple and rapid fabrication experience. Several properties of the hydrophobic material were characterized, such as the hydro head and penetration rate, with the aim of assessing its robustness and stability. The presented hydrophobic barriers fabricated using this approach have a barrier width of 4 mm, a coating thickness of 208 µm, and a hydrophilic resolution of 446.5 µm. This fabrication modality boasts an excellent solvent resistance with regard to the hydrophobic barrier. These devices were employed for on-the-spot detection of Metanil Yellow, a banned food adulterant often used in curcumin and pigeon peas, within successful limits of detection (LOD) of 0.5% (w/w) and 0.25% (w/w), respectively. These results indicate the great potential this fabricated hydrophobic device has in numerous paper-based applications and other closely related domains, such as diagnostics and sensing, signalling its capacity to become commonplace in both industrial and domestic settings.

Efficient production of bacterial cellulose based composites using zein protein extracted from corn gluten meal.

Corn gluten meal (CGM) which is a byproduct of corn wet milling is mainly used in animal and poultry feed. Due to its high protein content in CGM, it has been utilized for the extraction of zein protein which is the main hydrophobic protein present in the corn. The extracted zein protein was used along with bacterial cellulose that is highly pure, biocompatible, biodegradable, and generally regarded as safe for the preparation of composites that have better surface properties and applications. SEM analysis of the synthesized composite showed layering, incorporation of zein protein onto the surface of bacterial cellulose. XRD results showed there were no significant changes in the peak intensity due to the surface modification of BC membranes composites in comparison to pristine BC and TGA showed the thermostable characteristic of bacterial cellulose and are more capable of withstanding high temperature. Maximum production of bacterial cellulose was observed when corn gluten meal and zein protein were used as a cheap nitrogen sources for the production of bacterial cellulose along with other medium components. An increase of approximately 4.0g/l of bacterial cellulose from 13.561g/l to 17.83g/l was observed when corn gluten meal and zein protein were used in the production medium. The prepared BC-based zein protein composites can be utilized for food packaging and storage applications.

A high-performance flexible triboelectric nanogenerator based on cellulose acetate nanofibers and micropatterned PDMS films as mechanical energy harvester and self-powered vibrational sensor

Triboelectric nanogenerators are emerging mechanical energy harvesting devices in the era of the Internet of Things (IoT) for powering small-scale electronic devices or functioning as state-of-the-art self-powered sensors. Furthermore, observing vibration patterns from different electronic gadgets helps in assessing the health of the gadgets and also allows to detect the downtime as well as faults pre-emptively. Here, a triboelectric nanogenerator based on electrospun cellulose acetate nanofibers and surface modified PDMS is fabricated for powering commercial sensors. In addition, the effect of surface patterning on PDMS film such as arrays of micropyramid and microdome structures on the output characteristics of TENG has been systematically investigated. The PDMS with micropyramidal arrays in combination with electrospun cellulose acetate nanofibers showed a massive enhancement (~180 times) in the power density of TENG, as compared to the flat PDMS film-based device. The fabricated facile and flexible TENG with micropyramidal surface modification on PDMS can generate an output voltage of 400 V, short circuit current of 3 mA/m2 and peak power density of 0.9 W/m2 respectively. In addition, with a little tweak in the structure, the same cellulose acetate nanofiber-PDMS based TENG is transformed into an active self-powered vibration sensor. Utilizing this, the vibration profile of an electric-sewing machine is mapped under various frequencies of operation. Additionally, anomalous vibrational behaviours from different electronic gadgets such as hard disks and computer fans, as a result of mechanical imbalances, are also detected using the self-powered triboelectric vibrational sensor.

Evaluation of Touch and Durability of Cotton Knit Fabrics Treated with Reactive Urethane-Silicone Softener

A new reactive urethane–silicone softener was developed to provide a soft touch to cotton knit fabrics with improved durability to washing and dimensional stability. The reactive urethane–silicone softener consisted of an amino silicone softener and a blocked isocyanate, which can crosslink and react with cellulose surfaces. The activated isocyanate from the blocked isocyanate reacted with the amino silicone softener by heat treatment at 150 °C for 30 min. The mechanical properties of the cotton knit fabrics treated with the urethane–silicone softener were evaluated using a Kawabata Evaluation System-Fabrics (KES-FB) system. The cotton knit fabrics treated with the urethane–silicone softener showed excellent elasticity, flexibility and shear recovery as well as excellent recovery against bending deformation, and soft and smooth surface characteristics with a small coefficient of friction that were maintained even after washing 20 times.

Molecular Insights into the Interfacial Properties of Cellulose Surfaces with Varying Types of Ionic Liquid Epoxies

Molecular Insights into the Interfacial Properties of Cellulose Surfaces with Varying Types of Ionic Liquid Epoxies

Dispersion characterizations and adhesion properties of epoxy composites reinforced by carboxymethyl cellulose surface treated carbon nanotubes

To improve the dispersion effectiveness of carbon nanotubes (CNTs) in epoxy and the adhesion of the resulted composites on steel substrates, this paper proposed to surface treat CNTs using carboxymethyl cellulose (CMC) in the epoxy-CNTs composite. The dispersion characterizations and adhesion properties of epoxy composites reinforced by CMC surface treated CNTs were then systematically investigated. CNTs with three different weight fractions (0.5%, 1%, and 2%) were surface treated by CMCs to improve their dispersion in epoxy-CNTs composites. It was found by Raman spectroscopy, particle size analysis, transmission and scanning electron microscopy that the CMC surface treatment was effective in reducing the size of CNT clusters to achieve a better dispersion of CNTs in such epoxy-based composite. The experimental results of contact angle and single lap joint tests indicated that better CNT dispersion resulted from the CMC surface treatment significantly improved the wettability and adhesion properties of the epoxy-CNTs composites.

Sono-synthesis of cellulose-TiO2 nanocomposite adsorbent for fast cleaning of anionic dyes containing wastewater

This work was devoted to synthesizing a composite of cellulose-TiO2 by the in-situ process using the sol-gel method and applied on representatives of acid dyes to determine the functionality regarding the adsorption of dyes from aqueous solution. The composite particle adsorbed 100% dyes within 3 min of the direct application. XRD, FTIR, SEM, and Zeta potential tests were conducted to investigate the effect of crystal, molecular structure, surface morphology, and surface charges on the absorption speed of cellulose-TiO2 composite particles. The experimental results revealed that the cellulose was partially hydrolyzed by concentrated hydrochloric acid and left some positive charge on the surface of cellulose during the synthesis of the composite structure. The test results demonstrated that nano TiO2 with a thin layer of cellulose covered the surface of undegraded cellulose particles. The structural changes in the composite made them beneficial to fast dye adsorption. The effect of initial dye concentration, composite dosage, and temperatures were also investigated to find the optimum condition for dye adsorption. The optimum condition was found at the initial concentration of 400 mg/l, dosage of 0.10 g, and temperature of 25 °C. The removal efficiency and maximum adsorption capacity at this condition were 100% and 40 mg/g, respectively. The adsorption data suggested that the data was well fitted with a pseudo-second-order model for adsorption kinetics and Langmuir model for adsorption isotherm. Thermodynamic analysis revealed that the adsorption process was physisorption, spontaneous, random, and endothermic. Overall, in this work, the developed cellulose-TiO2 nanocomposite might be an economical and efficient adsorbent to remove dyes from wastewater.

The influence of ionic liquid concentration on microcrystalline cellulose modification

Ethanolic ionic liquid (IL) solutions, containing different 1-n-butyl-3-methylimidazolium chloride (C4MImCl) concentrations were used to modify the surface of commercial microcrystalline cellulose (MCC). The chosen ratios were: 4, 8, 16, and 32 wt.% of IL, in relation to the MCC mass. These treatments with IL did not affect the MCC morphology. FTIR analysis showed the characteristic bands of C4MImCl when the IL concentration was higher than 4 wt.%. XRD diffractograms show that the crystals may have been disrupted for IL concentrations above 4 wt.%. 1H NMR confirmed the formation of strong hydrogen bonds between C4MImCl and MCC, especially for MCC treated with 4 wt.% of IL. The functionalization using IL, regardless of the content, showed two DTG peaks, without altering the MCC Arrhenius’ parameters and degradation mechanisms. 4 wt.% of C4MImCl proved to be suitable for the MCC surface modification, improving thermal stability without detrimental effects on MCC morphology.

Surface Modification of Decellularized Natural Cellulose Scaffolds with Organosilanes for Bone Tissue Regeneration.

The utility of plant tissues as scaffolding materials has been gaining significant interest in recent years owing to their unique material characteristics that are ideal for tissue regeneration. In this study, the degradation and biocompatibility of natural cellulosic scaffolds derived from Borassus flabellifer (Linn.) (BF) immature endosperm was improved by chemical oxidation and surface functionalization processes. Briefly, thus obtained cellulosic scaffolds were sequentially processed via a detergent exchange decellularization process followed by sodium periodate mediated oxidation and organosilane-based surface modification using amino (NH2)-terminated 3-aminopropyltriethoxysilane (APTES) and methyl (CH3)-terminated octadecyltrichlorosilane (OTS). Post oxidation and surface functionalization, the scaffolds showed improved physiochemical, morphological, and mechanical properties. Especially, the swelling capacity, total porosity, surface area, degradation kinetics, and mechanical behavior of scaffold were significantly higher in modified scaffold groups. The biocompatibility analysis demonstrated excellent cellular adhesion, proliferation and differentiation of osteoblasts with an evident upregulation of mineralization. Subcutaneous implantation of these scaffolds in a rat model demonstrated active angiogenesis, enhanced degradation, and excellent biocompatibility with concomitant deposition of a collagen matrix. Taken together, the native cellulosic scaffolds post chemical oxidation and surface functionalization can exclusively integrate the potential properties of native soft tissue with ameliorated in vitro and in vivo support in bone tissue engineering for nonloading bearing applications.

Growing of Artificial Lignin on Cellulose Ferulate Thin Films.

Thin films of cellulose ferulate were designed to study the formation of dehydrogenation polymers (DHPs) on anchor groups of the surface. Trimethylsilyl (TMS) cellulose ferulate with degree of substitution values of 0.35 (ferulate) and 2.53 (TMS) was synthesized by sophisticated polysaccharide chemistry applying the Mitsunobu reaction. The biopolymer derivative was spin-coated into thin films to yield ferulate moieties on a smooth cellulose surface. Dehydrogenative polymerization of coniferyl alcohol was performed in a Quartz crystal microbalance with a dissipation monitoring device in the presence of H2O2 and adsorbed horseradish peroxidase. The amount of DHP formed on the surface was found to be independent of the base layer thickness from 14 to 75 nm. Pyrolysis-GC-MS measurements of the DHP revealed β-O-4 and β-5 linkages. Mimicking lignification of plant cell walls on highly defined model films enables reproducible investigations of structure-property relationships.

In English

The properties of heteropoly acids and of their complexes with cationic surfactants at the trace level have been studied by ESR spectroscopy, UV-VIS spectrophotometry, NMR and FTIR spectroscopy, by the method of chemiluminescence analysis applied in aqueous solutions and on the cellulose surface. For elucidation of the mechanism of chemiluminescence reactions of heteropoly acids with luminol kinetic methods, diffuse reflectance spectroscopy and liquid chromatography have been applied. For the first time one-electron reduction of heteropoly acids by luminol was confirmed by registration of diffuse reflectance spectra of reduced heteropoly acids on cellulose surface. It has been suggested that the mechanism of heteropoly acids immobilization on cellulose includes combination of Coulomb and hydrophobic interactions. A scheme of heteropoly acids immobilization on the surface was proposed based on ion exchange processes on cellulose or diethylaminoethyl cellulose surface. It has been shown that ionic associates heteropoly acid – cationic surfactant react with an alkaline solution of luminol with light emission similarly to heteropoly acids themselves. For the first time, heterogeneous chemiluminescence, namely, the chemiluminescence of heteropoly acids immobilized on cellulose, with luminol, has been used for examining the composition of ionic associates heteropoly acid - cationic surfactant. By using Bjerrum’s method it has been found that in strongly acidic media (at pH 1.0) vanadomolybdophosphoric acid forms with cationic surfactant, namely, with dodecylpyridinium bromide, not tetra-substituted but triply substituted ionic associate. This result can be explained by the fact that the fourth proton in H4PVMo11O40 is weakly dissociated; it is more strongly bound to heteropoly anion and is localized on the oxygen atom of the Mo–O–Mo angular bond. Ionic associates of heteropoly acids were used as analytical forms for highly sensitive chemiluminescence determination of P, As, Si, Ge in waters of different types. Detection limits for P, As, Si, Ge are 0.02–0.07 µg/L. Due to the high sensitivity of the method, phosphorus was successfully determined in surface water and ultrapure water, arsenic – in river and mineral water, silicon – in ultrapure water and vapor condensate of electric power stations, germanium – in water of electronic industry.

Influence of Sugars, Sugar Alcohols and Their Combinations on Environmentally Significant Cellulase Production Under Liquid State Fermentation

To expand the range of soluble carbon sources for enzyme production by the microbial system, we investigated the ability of different sugars in cellulase production. Carbon sources play a vital role in cell metabolism and the synthesis of cellulase. Although the insoluble cellulosic materials are considered the most effective natural inducers for cellulase production by microorganisms in terms of both enzyme yield and productivity, their insolubility causes many problems and presents a major drawback that is partly responsible for the high cost of cellulase production. Mostly, the insolubility of sugar polymer leads to difficult and complex fermentation operations, including sterilization, cell biomass measurement, mixing and aeration of the fermentation broth, continuous feeding/sampling, and subsequent enzyme purification. Second, cellulase gets absorbed into the solid cellulose surface, leading to enzyme loss. The present paper gives a comparative view on the utility of pure sugars (lactose, CMC, sucrose, maltose, cellobiose, xylose, trehalose, arabinose) and sugar alcohols (sorbitol, mannitol) on cellulase production by various fungal strains. It also describes the blending effect of sugars as well as sugar alcohols on cellulase production by fungal strains.

Synthesis and defect characterization of hybrid ceria nanostructures as a possible novel therapeutic material towards COVID-19 mitigation

This study reports the synthesis of hybrid nanostructures composed of cerium dioxide and microcrystalline cellulose prepared by the microwave-assisted hydrothermal route under distinct temperature and pH values. Their structural, morphological and spectroscopic behaviors were investigated by X-Rays Diffraction, Field Emission Gun Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, and Fourier-Transform Infrared, Ultraviolet–Visible, Raman and Positron Annihilation Lifetime spectroscopies to evaluate the presence of structural defects and their correlation with the underlying mechanism regarding the biocide activity of the studied material. The samples showed mean crystallite sizes around 10 nm, characterizing the formation of quantum dots unevenly distributed along the cellulose surface with a certain agglomeration degree. The samples presented the characteristic Ce–O vibration close to 450 cm−1 and a second-order mode around 1050 cm−1, which is indicative of distribution of localized energetic levels originated from defective species, essential in the scavenging of reactive oxygen species. Positron spectroscopic studies showed first and second lifetime components ranging between 202–223 ps and 360–373 ps, respectively, revealing the presence of two distinct defective oxygen species, in addition to an increment in the concentration of Ce3+-oxygen vacancy associates as a function of temperature. Therefore, we have successfully synthesized hybrid nanoceria structures with potential multifunctional therapeutic properties to be further evaluated against the COVID-19.

Xylan adsorption on cellulose: Preferred alignment and local surface immobilizing effect

Interaction between xylan and cellulose microfibrils is required to maintain the integrity of secondary cell walls. However, the mechanisms governing their assembly and the effects on cellulose surface polymers are not fully clear. Here, molecular dynamics simulations are used to study xylan adsorption onto hydrated cellulose fibrils. Based on multiple spontaneous adsorption simulations it is shown that an antiparallel orientation is thermodynamically preferred over a parallel one, and that adsorption is accompanied by the formation of regular but orientation-dependent hydrogen bond patterns. Furthermore, xylan adsorption restricts the local dynamics of the adjacent glucose residues in the surface layer to a level of the crystalline core, which is manifested as a three-fold increase in their 13C NMR T1 relaxation time. These results suggest that xylan forms a rigid and ordered layer around the cellulose fibril that functions as a transition phase to more flexible and disordered polysaccharide and lignin domains.

Carbohydrate-aromatic interface and molecular architecture of lignocellulose

Plant cell walls constitute the majority of lignocellulosic biomass and serve as a renewable resource of biomaterials and biofuel. Extensive interactions between polysaccharides and the aromatic polymer lignin make lignocellulose recalcitrant to enzymatic hydrolysis, but this polymer network remains poorly understood. Here we interrogate the nanoscale assembly of lignocellulosic components in plant stems using solid-state nuclear magnetic resonance and dynamic nuclear polarization approaches. We show that the extent of glycan-aromatic association increases sequentially across grasses, hardwoods, and softwoods. Lignin principally packs with the xylan in a non-flat conformation via non-covalent interactions and partially binds the junction of flat-ribbon xylan and cellulose surface as a secondary site. All molecules are homogeneously mixed in softwoods; this unique feature enables water retention even around the hydrophobic aromatics. These findings unveil the principles of polymer interactions underlying the heterogeneous architecture of lignocellulose, which may guide the rational design of more digestible plants and more efficient biomass-conversion pathways.

Hydrothermal carbonization of cellulose in aqueous phase of bio-oil: The significant impacts on properties of hydrochar

Aqueous phase of bio-oil (APBO) is a major fraction of bio-oil deriving from pyrolysis of biomass. APBO mostly contains water, carboxylic acids and different kinds of organics, which can afford a potential reactive medium for hydrothermal carbonization (HTC) of biomass. In this study, the HTC of cellulose in APBO was conducted, aiming to probe the effects of the APBO organics on the properties of the hydrochar. The results showed that the organics such as sugars, sugar-derivatives and phenolics in APBO could adsorb on the surface of cellulose and suppress the hydrolysis at lower temperature (i.e. 180 °C), while they could cross-polymerize with cellulose derivatives at higher temperatures (i.e. 220 or 260 °C). Compared with the hydrochar obtained in water, the APBO remarkably enhanced hydrochar yield by 11.3% and resulted in the abundant formation of aliphatic structures, making the hydrochar carbon and hydrogen-rich but with a lower thermal stability. In addition, the involvement of the APBO organics within the cross-polymerization interfered with the nucleation of the sugars/furans and inhibited the formation of the spheres with a hydrophilic shell and a hydrophobic core, resulting in the formation of an irregularly shaped hydrochar. Such a process also made the hydrochar rather hydrophobic, while the combustion performance was highly improved, exhibiting a lower ignition temperature (170 °C in APBO vs 306 °C in water).

Surface tailoring of cellulose aerogel-like structures with ultrathin coatings using molecular layer-by-layer assembly

Cellulose nanofibril-based aerogels have promising applicability in various fields; however, developing an efficient technique to functionalize and tune their surface properties is challenging. In this study, physically and covalently crosslinked cellulose nanofibril-based aerogel-like structures were prepared and modified by a molecular layer-by-layer (m-LBL) deposition method. Following three m-LBL depositions, an ultrathin polyamide layer was formed throughout the aerogel and its structure and chemical composition was studied in detail. Analysis of model cellulose surfaces showed that the thickness of the deposited layer after three m-LBLs was approximately 1 nm. Although the deposited layer was extremely thin, it led to a 2.6-fold increase in the wet specific modulus, improved the acid-base resistance, and changed the aerogels from hydrophilic to hydrophobic making them suitable materials for oil absorption with the absorption capacity of 16–36 g/g. Thus, demonstrating m-LBL assembly is a powerful technique for tailoring surface properties and functionality of cellulose substrates.

Strong Bacterial Cellulose-Based Films with Natural Laminar Alignment for Highly Sensitive Humidity Sensors.

Humidity sensors have been widely used for humidity monitoring in industry and agriculture fields. However, the rigid structure, nondegradability, and large dimension of traditional humidity sensors significantly restrict their applications in wearable fields. In this study, a flexible, strong, and eco-friendly bacterial cellulose-based humidity sensor (BPS) was fabricated using a two-step method, involving solvent evaporation-induced self-assembly and electrolyte permeation. Rapid evaporation of organic solvent induces the formation of nanopores of the bacterial cellulose (BC) surface and promotes structural densification. Furthermore, the successful embedding of potassium hydroxide into the sophisticated network of BC effectively enhanced the sensing performance of BPS. The BPS exhibits an excellent humidity sensing response of more than 103 within the relative humidity ranging from 36.4 to 93% and strong (66.4 MPa) and high flexibility properties owing to the ultrafine fiber network and abundant hydrophilic functional groups of BC. Besides being strong and thin, BPS is also highly flexible, biodegradable, and humidity-sensitive, making it a potential candidate in wearable electronics, human health monitoring, and noncontact switching.