Fe3O4 Nanoparticles Grown on Cellulose/GO Hydrogels as Advanced Catalytic Materials for the Heterogeneous Fenton-like Reaction

Cellulose/graphene oxide (GO)/iron oxide (Fe3O4) composites were prepared by coprecipitating iron salts onto cellulose/GO hydrogels in a basic solution. X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared, and X-ray diffraction characterization showed that Fe3O4 was successfully coated on GO sheets and cellulose. Cellulose/GO/Fe3O4 composites showed excellent catalytic activity by maintaining almost 98% of the removal of acid orange 7 (AO7) and showed stability over 20 consecutive cycles. This performance is attributable to the synergistic effect of Fe3O4 and GO during the heterogeneous Fenton-like reaction. Especially, the cellulose/GO/Fe3O4 composites preserve their activity by keeping the ratio of Fe3+/Fe2+ at 2 even after 20 catalysis cycles, which is supported by XPS analysis

Aerogels based on reduced graphene oxide/cellulose composites: Preparation and vapour sensing abilities

This paper reports on the preparation of cellulose/reduced graphene oxide (rGO) aerogels for use as chemical vapour sensors. Cellulose/rGO composite aerogels were prepared by dissolving cellulose and dispersing graphene oxide (GO) in aqueous NaOH/urea solution, followed by an in-situ reduction of GO to reduced GO (rGO) and lyophilisation. The vapour sensing properties of cellulose/rGO composite aerogels were investigated by measuring the change in electrical resistance during cyclic exposure to vapours with varying solubility parameters, namely water, methanol, ethanol, acetone, toluene, tetrahydrofuran (THF), and chloroform. The increase in resistance of aerogels on exposure to vapours is in the range of 7 to 40% with methanol giving the highest response. The sensing signal increases almost linearly with the vapour concentration, as tested for methanol. The resistance changes are caused by the destruction of the conductive filler network due to a combination of swelling of the cellulose matrix and adsorption of vapour molecules on the filler surfaces. This combined mechanism leads to an increased sensing response with increasing conductive filler content. Overall, fast reaction, good reproducibility, high sensitivity, and good differentiation ability between different vapours characterize the detection behaviour of the aerogels. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Smart Cellulose Fibers Coated with Carbon Nanotube Networks

Smart multi-walled carbon nanotube (MWCNT)-coated cellulose fibers with a unique sensing ability were manufactured by a simple dip coating process. The formation of electrically-conducting MWCNT networks on cellulose mono- and multi-filament fiber surfaces was confirmed by electrical resistance measurements and visualized by scanning electron microscopy. The interaction between MWCNT networks and cellulose fiber was investigated by Raman spectroscopy. The piezoresistivity of these fibers for strain sensing was investigated. The MWCNT-coated cellulose fibers exhibited a unique linear strain-dependent electrical resistance change up to 18% strain, with good reversibility and repeatability. In addition, the sensing behavior of these fibers to volatile molecules (including vapors of methanol, ethanol, acetone, chloroform and tetrahydrofuran) was investigated. The results revealed a rapid response, high sensitivity and good reproducibility for these chemical vapors. Besides, they showed good selectivity to different vapors. It is suggested that the intrinsic physical and chemical features of cellulose fiber, well-formed MWCNT networks and favorable MWCNT-cellulose interaction caused the unique and excellent sensing ability of the MWCNT-coated cellulose fibers, which have the potential to be used as smart materials

Clickable Polymers Accessible through Nucleophilic Substitution on Polysaccharides: A Sophisticated Route to Functional Polymers

This review article is dedicated to special polysaccharide esters – the polysaccharide toluenesulfonic acid esters (tosylates) and polysaccharide carbonate esters. After describing the specifics of the synthesis, particular emphasis is placed on the use of polysaccharide tosylates and polysaccharide phenyl carbonates for subsequent modification by nucleophilic substitution (SN) reactions. For this purpose, the advantages and limitations of the respective derivatives are discussed with regard to their application in chemical modification with nucleophiles containing functional groups. A few functional polysaccharide derivatives and their properties are presented. Finally, reactive derivatives for click chemistry approaches are featured. These can be prepared starting from the reactive intermediate of either polysaccharide tosylate or polysaccharide phenyl carbonate

Smart Cellulose Fibers Coated with Carbon Nanotube Networks

Smart multi-walled carbon nanotube (MWCNT)-coated cellulose fibers with a unique sensing ability were manufactured by a simple dip coating process. The formation of electrically-conducting MWCNT networks on cellulose mono- and multi-filament fiber surfaces was confirmed by electrical resistance measurements and visualized by scanning electron microscopy. The interaction between MWCNT networks and cellulose fiber was investigated by Raman spectroscopy. The piezoresistivity of these fibers for strain sensing was investigated. The MWCNT-coated cellulose fibers exhibited a unique linear strain-dependent electrical resistance change up to 18% strain, with good reversibility and repeatability. In addition, the sensing behavior of these fibers to volatile molecules (including vapors of methanol, ethanol, acetone, chloroform and tetrahydrofuran) was investigated. The results revealed a rapid response, high sensitivity and good reproducibility for these chemical vapors. Besides, they showed good selectivity to different vapors. It is suggested that the intrinsic physical and chemical features of cellulose fiber, well-formed MWCNT networks and favorable MWCNT-cellulose interaction caused the unique and excellent sensing ability of the MWCNT-coated cellulose fibers, which have the potential to be used as smart materials

Functional Polymeric Materials Based on Cellulose

[No abstract available

Chemical Modification of Pectin and Polygalacturonic Acid: A Critical Review

Pectin, as a sustainable biopolymer with its two complementary functionalities (carboxyl and hydroxyl moieties) imparted in the α-1,4-galacturonic acid repeating unit, has gained increasing attention in the last few years. The interest in this ubiquitously occurring plant originating polysaccharide (PS) has shifted slowly from applications as a food additive to a broader range of potential applications in medicine, cosmetics, and other industries. Due to the increasing interest in alternatives for petrochemical materials, PSs as biomaterials have gained increasing attention in industrial processes in general. In the last decade, an increasing number of chemical transformations related to pectin have been published, and this is a prerequisite for the design of the structure and hence properties of novel biopolymer-based materials. This work aims to review the chemical modifications of pectin by covalent linkage of the last decade and analyze the materials obtained with these chemical methods critically

Aerogels Based on Reduced Graphene Oxide/Cellulose Composites: Preparation and Vapour Sensing Abilities

This paper reports on the preparation of cellulose/reduced graphene oxide (rGO) aerogels for use as chemical vapour sensors. Cellulose/rGO composite aerogels were prepared by dissolving cellulose and dispersing graphene oxide (GO) in aqueous NaOH/urea solution, followed by an in-situ reduction of GO to reduced GO (rGO) and lyophilisation. The vapour sensing properties of cellulose/rGO composite aerogels were investigated by measuring the change in electrical resistance during cyclic exposure to vapours with varying solubility parameters, namely water, methanol, ethanol, acetone, toluene, tetrahydrofuran (THF), and chloroform. The increase in resistance of aerogels on exposure to vapours is in the range of 7 to 40% with methanol giving the highest response. The sensing signal increases almost linearly with the vapour concentration, as tested for methanol. The resistance changes are caused by the destruction of the conductive filler network due to a combination of swelling of the cellulose matrix and adsorption of vapour molecules on the filler surfaces. This combined mechanism leads to an increased sensing response with increasing conductive filler content. Overall, fast reaction, good reproducibility, high sensitivity, and good differentiation ability between different vapours characterize the detection behaviour of the aerogels