Ultrasonic effect on the photocatalytic degradation of Rhodamine 6G (Rh6G) dye by cotton fabrics loaded with TiO 2 Abstract The effect of sonication on the photodegradation of Rhodamine 6G (Rh6G, a fluorone dye) using woven cotton fabrics decorated with TiO2 nanoparticles (NPs) has been investigated. TiO2 NPs were synthesized in situ by sol–gel method in the presence of cotton textile and then hydrothermally treated. TiO2-loaded fabrics were treated ultrasonically to test adhesion to- and properties of the NPs on the fabrics. We demonstrate good adhesion and a good stability of the NPs of TiO2. Moreover, sonication substantially improved the distribution on the surfaces and hence enhanced the fabrics catalytic activity. Either under UV or simulated sunlight, ultrasonicated fabrics were found to have a high photocatalytic activity towards Rh6G, used as a model dye. SEM, XPS, UV–Vis and FTIR spectroscopy, as well as ground state diffuse reflectance and laser induced luminescence were used to characterize fabrics/TiO2 samples in terms of topography, surface composition, influence of hydrothermal treatment on photocatalytic activity, stability of TiO2 NPs, electro-optical properties of the modified fabrics, as well as the effect of ultrasonication on the photodegradation of Rh6G. This work paves the way to a larger scale improvement of the photocatalytic performances of TiO2-loaded cotton fabrics by post-sonication. Graphic abstract

Synthesis of nanocrystalline cellulose via ammonium persulfate-assisted swelling followed by oxidation and their chiral self-assembly Abstract A single-step ammonium persulfate (APS)-assisted swelling, followed by oxidation, can prepare nanocrystalline cellulose (NCC) from cotton linters. The APS-swelling is the critical step in the process, and the effects of swelling time, temperature and solid–liquid ratios were thoroughly investigated. The optimal conditions for NCC preparation were a swelling time of 3.0 h, a swelling temperature of 25 °C, and a solid–liquid ratio of 1:50. Upon heating at 60 °C, the persulfate enters the amorphous region of the cellulose and produces active SO4·− and H2O2, which effectively attack the two-phase structure of cellulose and oxidize the –OH group at the C-6 position. The swelling temperature of 25 °C plays a crucial role in breaking the hydrogen bonds between the molecular chains of cellulose. It permits the preparation of NCC with a high yield and crystallinity index. The crystalline structure of cellulose Iβ did not change after APS swelling and oxidation. The atomic force microscopic analysis confirmed the formation of spindle-shaped particles with a helical structure. Upon natural evaporation of the NCC suspension, brittle films were obtained, which exhibited a left-hand layered structure and high iridescence with a fingerprint-texture. These materials can be applied as strength additives and chiral templates. Graphic abstract

Synthesis of cellulose–silica nanocomposites by in situ biomineralization during fermentation Abstract Bacteria cellulose (BC) generated by Acetobacter xylinum is made up of three-dimensional network of ribbon-shaped nanofibers and serves as a promising matrix for composite materials. Lately different types of nanoparticles have been adopted to modify BC via chemical reactions or physical adsorption, which usually require two steps or more and could not modify BC homogeneously. In this study we provide a one-step in situ biomineralization method during microbial fermentation to produce BC–silica nanocomposites with control over silica content. By statically culturing Acetobacter xylinum in the medium containing various amounts of sodium silicate, the slightly acidic culture environment due to consumption of glucose during fermentation could transfer sodium silicate to amorphous silica deposition that is evenly distributed on BC. The BC–silica nanocomposites obtained by this method possess superior mechanical properties such as high tensile strength and Young’s modulus, which are potential candidates for future biomedical applications. With the analysis of elemental abundance and chemical structures, we propose the synthetic mechanism of in situ production of BC–silica nanocomposites. This method is an efficient, controllable and environmental-friendly method to synthesize BC–silica nanocomposites, which also provides insights to other BC-inorganic hybrid composites and microbial modifications by microbial synthetic systems. Graphic abstract

Cellulose nanocrystal dye as reinforcement matrix of lipstick for inhibiting color migration Abstract Lipstick is a kind of popular cosmetic, which can give the lip a beautiful color and improve its appearance. The problem is that dye molecules would be in contact with the skin, whereas the lipstick made with dyed CNCs (CNC-lipstick) would reduce the contact. Herein, we demonstrated that the deficiency of color migration can be overcome by using the cellulose nanocrystal (CNC) dye to replace conventional dye in the lipstick substrates. The lipstick containing CNC dye (CNC-lipstick) could effectively inhibit the color migration and was easily erased as compared to ordinary lipsticks. The color change on the scoured skin was as high as ΔE* = 30.4 after using red ordinary dye-lipstick for 8 h, and red residue was clearly observed in the texture of the skin. Further cleaned with makeup remover, the color change on the scoured skin was ΔE* = 6.4. Notably, the color change of CNC-lipstick was ΔE* < 5, and only a small amount of red residue could be observed in the texture of the skin. The reduction of color migration from the lipstick to the skin was probably due to the fact that the dye absorbed by the CNC, which slowed down the diffusion rate of dye molecules. Our work paves the way for using CNC dye for inhibiting color migration in the lipstick application. Graphic abstract Cellulose nanocrystals were applied to prepare the color easy-cleaned lipstick.

A versatile TOCN/CGG self-assembling hydrogel for integrated wastewater treatment Abstract Water pollution caused by industrial discharges is a severe threat to our society. Thus, efficient and sustainable materials that can provide potential effective solutions are in high demand. The present work reports the development of a versatile strategy based on TEMPO-oxidized cellulose nanofibers (TOCN)/cationic guar gum (CGG) self-assembling hydrogels to remedy wastewater containing oil, heavy metal ions or organic dyes. The TOCN/CGG hydrogel-coated filter papers, prepared via a layer-by-layer deposition process, show a high oil/water separation efficiency (around 99%), with the coating amount of being as low as 0.032 g m−2 (dry mass). Through gravitational force only, the water flux can be as high as 443 L m−2 h−1. The as-prepared oil/water separation materials exhibited good recyclability. The monolithic TOCN/CGG hydrogel can also efficiently remove copper ions (Cu2+) and dyes (i.e. thioflavin T and methyl orange), based on an adsorption mechanism. The adsorption amount of Cu2+ can be as high as 498.5 mg g−1, while that of thioflavin T and methyl orange can be 430.2 mg g−1 and 134.3 mg g−1, respectively. The mass transfer driving force and the number of active binding sites are the two main factors affecting the adsorption process. This all-polysaccharide hydrogel system may be a promising potential for wastewater remedy, due to its facile/“green” preparation process and high performance, as well as the abundance and environmental-friendliness of its raw materials. Graphic abstract

Collagen/cellulose nanofiber hydrogel scaffold: physical, mechanical and cell biocompatibility properties Abstract Collagen hydrogel applications in tissue engineering are limited due to its weak physical and mechanical properties, e.g. loss of water, destruction in the biological medium, weak mechanical properties, and handling difficulty. To improve the physical and mechanical properties of collagen hydrogel, cellulose nanofibers (CNF) were introduced to the collagen hydrogel. Up to 8% CNF, by total dry weight, was added to cold collagen acidic solution and the solution underwent gel formation by increasing pH and temperature to 7.4 and 37 °C, respectively. The gelation time was decreased when CNF was added to the collagen solution. The scanning electron microscopy images of collagen/CNF nanocomposites illustrated porous morphology with larger pore and denser nanofibrous structure than pure collagen. More water retention ability of collagen/CNF hydrogels along with lower hydrolytic degradation rate indicated higher stability of CNF composite hydrogels than pure collagen hydrogel. Mechanical testing demonstrated enhancement in both compression strength and fracture strain when CNF was added to the collagen hydrogel. The presence of free CNF and possible interactions between collagen and CNF was demonstrated by thermogravimetric and Fourier-transform infrared analysis. While the stability and mechanical properties of collagen hydrogel was enhanced by adding CNF, the MTT assay revealed the same cell viability for collagen/CNF scaffold as collagen. Furthermore, the live-dead assay demonstrated excellent capability of CNF nanocomposite for cell 3D culturing. Graphic abstract

Birefringence-based orientation mapping of cellulose nanofibrils in thin films Abstract Determination of nanofibril orientation is crucial for predicting the properties of films and membranes made from cellulose nanofibrils (CNF) because of their inherent anisotropic nature. A novel method is proposed based on image analysis of the polarized light micrographs to quantify and map nanofibril orientation in the film structure. Thin films (average 30 µm in thickness) of CNF were produced using a filtration method and were wet-stretched to two extension levels. Randomly-oriented films were also produced as the control without applying stretch. Samples were imaged at − 45°, 0° and + 45° between crossed polarizers using a polarized light microscope. A BOI was developed based on the interference color changes between the two angles (+ 45° and − 45°). The proposed BOI values range between − 1 and + 1 differentiating orientation in perpendicular directions. The index was shown to work successfully for mapping of the fibril orientation in CNF films. Statistical analysis of the tensile test results confirmed significant difference between tensile modulus of CNF films produced using different stretch ratios. This difference was also supported by the good agreement between the tensile properties of the films, the BOI and directionality results obtained from the surface analysis of scanning electron micrographs. The method was validated by applying to single pulp fibers with known orientation as well as un-stretched and stretched polyvinyl chloride films and oriented cellulose nanocrystals. The advantages of the proposed method over other conventional methods used for orientation analysis are discussed.

Green approach for the activation and functionalization of jute fibers through ball milling Abstract As well known, cellulose fibers, defibrillated/activated in different degrees or even chemically modified, can be employed as additives in matrixes of different nature with the aim of modulating some properties such as the mechanical resistance, rheological behavior or hydrophobicity of the product. Consequently, there is an increasing interest in the incorporation of these materials in a wide variety of products, being necessary the development of green methodologies for their chemical modification. The objective of this work is the use of the ball milling technology as tool for the activation and chemical modification of cellulose fibers, specifically of cellulosic material from jute. The traditional method used to date for the NCO-functionalization of cellulose fibers requires a solvent as reaction medium, the action of a catalyst and a previous stage of mercerization to boost the reactivity of the fibers. Accordingly to the former, jute fibers were NCO-functionalized, on one side, evading previous mercerization and, on other side, applying two different alkali-based activation pre-treatments that lead to materials with different crystallinity index. In addition to this, and after having optimized milling conditions, both activation and NCO-functionalization were successfully carried out in a planetary ball mill avoiding solvent, catalyst and previous alkalization. Cellulose fibers esterification was successfully implemented over already ball milled cellulosic material, showing that activation and chemical modification do not need to be performed at the same time. Fourier transform infrared spectroscopy provided the follow-up of each reaction and the impact of ball milling on the fibers was analyzed by hydrodynamic diameter measurements. Thus, it is demonstrated that ball milling can be proposed as an efficient and environmentally friendly methodology for the activation and/or functionalization of cellulose fibers. Graphic abstract

High-strength, tough, and self-healing hydrogel based on carboxymethyl cellulose Abstract Hydrogels are the focus of extensive research due to their potential applications in various fields including tissue engineering, drug delivery, soft actuators, and sensors, etc. However, insufficient functionality and weak mechanical properties limit their practical applications. Herein, we developed a simple approach to fabricate strong, tough and self-healable hydrogels by introducing sodium carboxymethyl cellulose (CMC) into poly (acrylic acid) (PAA)–Fe3+ hydrogels as well as by simply soaking the gels in sodium chloride (NaCl) solution. During the deformation process, the synergetic interactions of –COO−/Fe3+ physically ionic networks as well as PAA covalent networks can homogeneously distribute stress, and more importantly, high degree of network densities, and chain entanglements introduced by soaking treatment could act as “sacrificial bonds” to dissipate energy effectively. As a result, the resulting optimal PAA/CMC1.0–Fe3+–S samples with water content of approximately 37.7 wt% possessed remarkable mechanical properties, with elastic modulus of 0.41 MPa, fracture tensile stress of 4.42 MPa, superior to that of PAA–Fe3+ and PAA/CMC1.0–Fe3+ hydrogels. Additionally, the noncovalent ionic interactions of PAA/CMC1.0–Fe3+ hydrogels serve as dynamic but stable associations, leading to effective self-healing efficiency (over 85%) after damage, with recovered fracture stress of 3.75 MPa as well as an elongation at break of about 750%. We expect this facile strategy may enrich the avenue in exploration of high-strength, tough and self-healing cellulosic hydrogels. Graphic abstract

Silicone quaternary ammonium salt based nanocomposite: a long-acting antibacterial cotton fabric finishing agent with good softness and air permeability Abstract A silicone quaternary ammonium salt based nanocomposite was synthesized and the chemical structure and stability of the nanocomposite were investigated. The results showed that the OQAS/(Ag/ZnO) nanocomposite had prepared successfully. The cotton fabrics were treated with different concentration of OQAS/(Ag/ZnO) nanocomposite and its antibacterial, durability, softness, hydrophilicity, and air permeability were also be examined using diverse characterization techniques. The antibacterial rate of treated cotton can reach to over 90%. After 10 cycles washing, antibacterial rate retain over 85% for both E. coli and S. aureus, because the chemical bond had formed between nanocomposite and cotton from the FT-IR result. In addition, a model bacterium, E. coli was used to evaluate the antibacterial mechanism and kinetics of nanocomposite. The hydrophilicity, air permeability and softness of the treated cotton fabrics were also had an improvement to some extent.