Oxidized Cellulose Nanofibrils Research Articles

Polyethylenimine functionalized graphene oxide and cellulose nanofibril composite hydrogels: Synthesis, characterization and water pollutants adsorption

A stable 2,2,6,6-tetramethylpiperidine-1-yl)oxyl (TEMPO)-oxidized cellulose nanofibril (TCNF)/graphene oxide (GO)/polyethylenimine (PEI) composite hydrogel was synthesized by self-assembly instead of chemical crosslinking. Their chemical, morphology, surface, and mechanical properties were characterized and adsorption behavior for methyl blue (–) was systematically investigated in terms of the optimal GO content, pH effect, kinetics, and isotherm models. Additionally, to assess the adsorption capability of the TCNF/GO/PEI hydrogel for various contaminants, its effectiveness was also tested for methylene blue (+), Cu (II), and soybean oils. The maximum adsorption capability for the methyl blue (−) dyes increased from 3125 to 3962 mg/g when 13.3 % of GO was added. The adsorption capability for Cu (II) and soybean oils rose from 205.3 to 218.5 and 2.1 to 7.2 mg/g, respectively. The adsorption capability of optimized TCNF/GO/PEI hydrogel for a variety of contaminants was improved overall based on the increase of surface area, electrostatic interactions, and hydrophobic domains. Moreover, adding GO did not impact the adsorption mechanism but increased the external diffusion rate in the intraparticle diffusion model. This work provides a self-assembling route to TCNF/GO/PEI hydrogels with great potential for the removal of multiple water pollutants.

Eco-friendly and novel tannin-based wood adhesive enhanced with cellulose nanofibrils grafted by hyperbranched polyamides

Tannin-based adhesives, as a natural biobased adhesive, have the potential to expand their application in wood industry as substitutes for traditional adhesives. In this study, cellulose nanofibrils and hyperbranched polyamides (HBPA) were studied to address the challenges associated with the low crosslinking degree and poor water resistance characteristics of condensed tannin-based wood adhesives. The modification strategy focuses on grafting oxidized cellulose nanofibrils with hyperbranched polyamides through the Schiff base reaction. Comprehensive analyses, including FTIR, XPS, XRD, and TG, confirm the successful binding of oxidized cellulose nanofibrils with hyperbranched polyamides, demonstrating their potential to enhance the properties of tannin adhesives. Furthermore, the investigation about bonding strength, and water resistance of tannin adhesives reveal significant improvements in the mechanical and water resistance properties through this modification strategy. In particular, the maximum wet shear strength is 0.7 MPa, meeting the requirements for Class II plywood. This study provides valuable insights into improving the performance of tannin adhesives, offering promising implications for broader applications and contributing to eco-friendly practices in the wood industry.

In-situ growing Eu-MOF on TEMPO-oxidized cellulose nanofibers to form fluorescent films for Fe3+ detection

Metal-organic frameworks (MOFs) are porous hybrid materials made of metal and organic linkers. Combining MOFs with polymers enhances their performance and addresses the issue of low stability. In this study, a uniform nanoscale Eu(III)-based metal-organic framework (Eu-MOF) was synthesized and grown in situ on TEMPO(2,2,6,6-tetramethylpiperidinyl-1-oxide)-oxidized cellulose nanofibrils (TOCNF), resulting in the formation of Eu-MOF@TOCNF fluorescence films through vacuum filtration. These films exhibited favorable mechanical properties, high transmittance, and stable fluorescence characteristics within the pH range of 3–11. The film produced the characteristic emission peak of Eu3+, recognized the selective quenching of Fe3+ within 0–100μM, and displayed an inverse relationship between fluorescence intensity at 616 nm and Fe3+ concentration. This approach holds significant promise for Fe3+ detection in solutions and offers a novel strategy for developing highly efficient optical sensors based on fluorescence specificity.

Surface charge manipulation for improved humidity sensing of TEMPO-oxidized cellulose nanofibrils

Cellulose-based humidity sensors have attracted great research interest due to their hydrophilicity, biodegradability, and low cost. However, they still suffer from relatively low humidity sensitivity. Due to the presence of negatively charged carboxylate groups, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (CNF) exhibits enhanced hydrophilicity and ion conductivity, which is considered a promising candidate for humidity sensing. In this work, we developed a facile strategy to improve the humidity sensitivity of CNF films by regulating their surface charge density. With the increase in surface charge density, both water uptake and charge carrier densities of the CNF films can be improved, enabling a humidity sensitivity of up to 44.5 % (%RH)−1, higher than that of most polymer-based humidity sensors reported in the literature. Meanwhile, the sensor also showed good linearity (R2 = 0.998) over the 15–75 % RH at 1 kHz. With these features, the CNF film was further demonstrated for applications in noncontact sensing, such as human respiration, moisture on fingertips, and water leakage, indicating the great potential of CNF film in humidity monitoring.

An anti-freezing and anti-drying nanocellulose hydrogel for human motion detection

Flexible sensors based on biological hydrogels have gained significant attention in the fields of wearable devices, human-computer interaction robots, and medical monitoring. Nanocellulose, a natural polymer material, offers advantages such as low cost, abundant reserves, green environmental protection, and renewability. However, the high water content of the nanocellulose-based flexible sensor limits its application at low temperatures, making it difficult for the nanocellulose-based hydrogel electronic skin to function properly. To enhance the hydrogel's anti-freezing and anti-drying properties, we introduced glycerol (GL) into the in-situ grown polypyrrole (PPy) hydrogel of 2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized cellulose nanofibril (TOCN) and obtained the organic hydrogel TOCN/PPy/GL. The prepared TOCN/PPy/GL organic hydrogel maintains excellent electrical conductivity, mechanical properties, and strain sensing capabilities (strain sensitivity GF=2.41 at −45 ℃, response time 100 ms, recovery time 200 ms). The TOCN/PPy/GL organic hydrogel electronic skin also exhibited exceptional anti-drying property, with a volume retention of 66.75% after 24 h at 100 ℃, which is six times higher than the volume retention of TOCN/PPy hydrogel without GL under the same conditions.

Injectable, rapid self-healing, antioxidant and antibacterial nanocellulose-tannin hydrogels formed via metal-ligand coordination for drug delivery and wound dressing

Nanocellulose-based hydrogels have attracted increasingly attention due to their biocompatibility, biodegradability, and hydrophilic properties. In this work, we proposed a simple route to fabricate composite hydrogels using TEMPO oxidized cellulose nanofibrils (TOCNF) and tannin through metal-ligand coordination. Calcium ions were utilized to rapidly cross-link the carboxyl groups on TOCNF and the tannins' catechol moieties via metal-ligand bonding, resulting in the formation of TOCNF-Ca2+-T composite hydrogels. The incorporation of tannins endowed the hydrogel with high antioxidant and antibacterial properties. The rheological analysis revealed that the addition of tannin led to an improved gel strength of the composite hydrogel. The hydrogel was injectable and could autonomously self-healed in 1 min without any trigger. Tetracycline hydrochloride (TH) was successfully loaded into the composite hydrogels, achieving a maximum encapsulation rate of 97.32%. TOCNF-Ca2+-40%T demonstrated a cumulative drug release of 36% at pH 1.3 and 86% at pH 7.4, indicating its pH-responsive nature. These hydrogels, derived from plant sources, exhibited high antibacterial and antioxidant properties, as well as biocompatibility, rapid self-healing, and injectability, which open up new possibilities for applications in wound dressing and drug delivery.

Low-temperature strain-sensitive sensor based on cellulose-based ionic conductive hydrogels with moldable and self-healing properties

Bioelectronics based on high-performance conductive ionic hydrogels, which can create novel technological interfaces with the human body, have attracted significant interest from both academia and industry. However, it is still a challenge to fabricate hydrogel sensor with integration of good mechanical properties, fast self-healing ability and flexible strain sensitivity below 0 °C. In this paper, we present a moldable, self-healing and adhesive cellulose-based ionic conductive hydrogel with strain-sensitivity, which was prepared by forming dual-crosslinked networks using poly(vinyl alcohol) (PVA) with borax, calcium chloride (CaCl2), zinc chloride (ZnCl2) and 2,2,6,6-tetramethylpiperidine-1-oxyl oxidized cellulose nanofibril (TCNF). The hydrogel exhibited fast self-healing within 10 s, moderate modulus of 5.13 kPa, high elongation rate of 1500 % and excellent adhesion behavior on various substrates. Due to multiple hydrogen bonding and the presence of CaCl2 and ZnCl2, the hydrogel presented a reduced freezing point as low as −41.1 °C, which enabled its application as a low-temperature strain sensor. The proposed hydrogel provides a simple and facile method for fabricating multi-functional hydrogels that can be used as suitable strain sensors for applications such as wearable electronic sensor, soft robotics and electronic skins in a wide temperature range.

Characterization and Antifungal Activity of Lemongrass Essential Oil-Loaded Nanoemulsion Stabilized by Carboxylated Cellulose Nanofibrils and Surfactant.

Nanocellulose is an emerging green, biodegradable and biocompatible nanomaterial with negligible toxicities. In this study, a carboxylated nanocellulose (i.e., 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TEMPO-CNF)) was prepared from corn stover and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA). Corn stover-derived TEMPO-CNF was explored as an emulsion co-stabilizer together with Tween 80 for lemongrass essential oil-loaded emulsions. Droplet size, phase behavior and thermodynamic stability of oil-in-water emulsions stabilized by Tween 80 and TEMPO-CNF were investigated. The optimal nanoemulsion stabilized by this binary stabilizer could achieve a mean particle size of 19 nm, and it did not form any phase separation against centrifugal forces, freeze-thaw cycles and at least 30 days of room temperature storage. The nanoencapsulated essential oil had better inhibition activity against the mycelial growth of Aspergillus flavus than pure essential oil. Results from this study demonstrate the potential of using agricultural byproduct-derived nanomaterial as nanoemulsion stabilizers for essential oils with good emulsion thermodynamic stability as well as enhanced antifungal activities.

Layer-by-layer assembly induced strong, hydrophobic and anti-bacterial TEMPO oxidized cellulose nanofibrils films for highly efficient UV-shielding and oil-water separation

Anti-ultraviolet material with cost-effectiveness, environmental friendliness, and multifunction is urgently needed to address the serious problem of ultraviolet radiation. However, traditional anti-ultraviolet products based on plastics are unsustainable and harmful to the environment. Herein, the cellulose films with a sandwich structure using a surface assembly technique were reported. Natural L-phenylalanine was grafted onto cellulose nanofibrils via amidation to enhance their UV-shielding property. To address the hydrophilic nature and limited mechanical strength of cellulose films, we employed octadecyltrichlorosilane and 4ARM-PEG-NH2 for hydrophobic coating and mechanical reinforcement, respectively. In addition to providing complete UV resistance in the wavelength range of 200–320 nm, sample OPT5 exhibited significantly improved tensile stress, Young's modulus, and toughness, measuring 174.09 MPa, 71.11 MPa, and 295.33 MJ/m3, respectively. Furthermore, due to the presence of antibacterial amine groups, the modified film demonstrated a satisfactory inhibitory effect on the growth of Escherichia coli and Bacillus subtilis. Compared to natural cellulose films, the hydrophobically modified material achieved a contact angle of up to 121.1°, which enabled efficient separation of oil-water mixtures with a maximum separation efficiency of 93.87 %. In summary, the proposed TOCNF-based UV-shielding film with multifunctionality holds great potential for replacing petrochemical-derived plastics and serving as an applicable and sustainable membrane material.

Electrochemically synthesized graphene/TEMPO-oxidized cellulose nanofibrils hydrogels: Highly conductive green inks for 3D printing of robust structured EMI shielding aerogels

We report on the design and synthesis of bio-based, electrically conductive green inks for direct ink writing (DIW) of lightweight electronics and electromagnetic interference (EMI) shields. The inks incorporate fibrillated cellulose and electrochemically synthesized graphene oxide (EGO), with no production and/or consumption of hazardous chemicals. The cellulosic component, TOCNF ((2,2,6,6-tetrame-thylpiperidin-1-yl) oxidanyl (TEMPO)-oxidized cellulose nanofibrils), improves the colloidal dispersion and the rheological properties of EGO-based inks for high-resolution 3D printing via DIW. The printing fidelity and shape retention significantly rely on the EGO/TOCNF loading and ratio in the precursor hydrogel inks. Aerogels result from freeze drying, allowing the production of 3D ultra-lightweight materials with prescribed macro-scale design featuring excellent stability and ease of handling. It is shown that the nano- and micro-scale design of the aerogels can be readily tuned by the solid content and EGO/TOCNF ratio in the inks. This multi-scale materials design provides a unique opportunity to control the mechanical and electrical properties of the printed structures. For instance, aerogels with compression modulus in the range of 250–1096 kPa are obtained based on the composition of the inks. For the optimized ink, an excellent EMI shielding effectiveness, as high as 55.6 dB, is achieved.

Fluoride ion adsorption isotherms, kinetics, and thermodynamics on iron(III) oxyhydroxide powders containing cellulose nanofibrils

The adsorption isotherms, kinetics, and thermodynamics of fluoride ions (F−) on FeOOH powders in water were investigated to obtain fundamental information on FeOOH powders, which are used as F− adsorbents in drinking and industrial water, and industrial wastewater. FeOOH powders were prepared as precipitates by mixing aqueous FeCl3 and NaOH solutions (1:3 mol/mol) in the presence of 2,2,6,6,-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibrils (TOCNs), carboxymethylcellulose (CMC), or TEMPO-oxidized cellulose (TOC) fibers (without nanofibrillation), and subsequent drying and pulverizing. The FeOOH:TOCN, FeOOH:CMC, and FeOOH:TOC dry mass ratios were controlled at 87:13. The amount of F− adsorbed by the FeOOH/TOCN powder per FeOOH mass was higher than those adsorbed by FeOOH, FeOOH/CMC, or FeOOH/TOC. The F− adsorption isotherms on the FeOOH-containing powders showed higher correlation coefficients with the Langmuir model than with the Freundlich model. This indicates that F− adsorbed on FeOOH initially formed a monolayer, predominantly via physical adsorption. Pseudo-second-order kinetics fitted well to the time-dependent F− adsorption behaviors on the FeOOH-containing powders. Thermodynamic analysis of F− adsorption on the FeOOH-containing powders showed that the ΔG values were negative, which indicates that F− adsorption on the FeOOH-containing powders proceeded spontaneously in water. The negative ΔG value for FeOOH/TOCN was higher than those for FeOOH, FeOOH/CMC, and FeOOH/TOC at the same temperature. This shows that the FeOOH/TOCN powder can be used as an excellent and efficient F− adsorbent in water.Graphical abstract

3-D Printable Flexible Hydrogel-Based Sensors With Gradient Porous Structure

Hydrogel-based flexible pressure sensors have been intensively studied to detect human physiological activities. Here, a kind of hydrogel with excellent 3-D printability has been developed. The gelation method based on the freeze-thaw cycles of polyvinyl alcohol (PVA) and the addition of (TEMPO)-oxidized cellulose nanofibrils (TOCNF) as rheological modifier rendered the printed hydrogel patterns great morphological fidelity. In addition, the conductivity of the hydrogels is as high as 3.8 S/m with the promotion of TOCNF. Also, the prepared hydrogels have gratifying mechanical properties under the salting-out effect (tensile and compressive stresses increased by 527% and 460%, respectively). The printed hydrogels with porous structure were applied to the electrode and dielectric layer of capacitance sensors (the dielectric layer was wrapped with ultrathin polyethylene (PE) film). The porous structure effectively improved the sensitivity of the pressure sensors (from 0.023 and 0.182 to 0.045 and 0.689 kPa <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1}$ </tex-math></inline-formula> ) when used as electrode and dielectric layer, respectively), while the gradient porous structure further broadened the linearity range of high sensitivity (electrode, from 2.92 to 15.35 kPa; dielectric layer, from 11.21 to 39.51 kPa). The results indicated that gradient porous structure is a simple and effective strategy to enhance both the sensitivity and linearity range of hydrogel-based sensors. The hydrogel-based sensors with printed structure have stable and sensitive capacitance and resistance response, and can also be used for motion monitoring of body parts, such as finger and arm.

Oxidized cellulose nanofibrils-based surimi gel enhancing additives: Interactions, performance and mechanisms

Surimi-based products with preferred textural properties and high nutritional value are fashionable throughout the market. Enhancing surimi gel characteristics is of key importance for enabling the following processing and warranting the end-product quality, but challenging due to the lack of energy- and performance-efficient processes and the elusive mechanisms underpinned such enhancements. Focusing on enhancing surimi gel properties by introducing sustainable additives, we successfully explore functionalized cellulose nanofibrils as a textural enhancer in surimi gels and establish a new model to expound the interaction mechanisms. Firstly, TEMPO-mediated oxidation prior to homogenization harvests functionalized cellulose nanofibrils with unique fibrillary shape, uniform nano-size, high surface hydrophilicity and activated -COO - groups, highly suited for the additive use in surimi gels (Monto et al., 2021). Secondly, the innovative application of oxidized cellulose nanofibrils at a remarkably low concentrations (0.1 g/100 g surimi) greatly improve the whiteness, microstructure, water holding capacity, gel strength and thermal stability of the surimi gels, through a synergistic effect of matrix-reinforcing, water binding and entrapping, covalent interactions (disulfide bonds, amide bonds), non-covalent interactions (hydrogen bonds, ionic bonds) and favorable protein conformational changes within the network. Next, a new mechanism model toward the high-performance surimi gels is concluded to better elucidate the interactions between oxidized cellulose nanofibrils and myosin molecules. We expect that this work can provide guidelines on designing novel and high-quality cellulose-additive foods and understanding the roles of food additives in meat gel systems, for advancing the applications of new additives and gelation mechanisms in the food industry. • A low cellulose nanofibrils (TCN) addition (0.1%) greatly improves surimi gel properties. • Deliberately activated COO − groups at TCN surface facilitates cellulose-myosin interactions. • Improved water holding capacity due to surface hydrophicility, water binding and entrapping. • Enhanced gel strength due to newly introduced ionic bonds, hydrogen bonds and physical entanglement. • A new mechanism model illustrating cellulose-protein interactions is established.

Zwitterionic chitin nanocrystals mediated composite and self-assembly with cellulose nanofibrils

Zwitterionic dispersed chitin nanocrystals and TEMPO oxidized cellulose nanofibrils can be well mixed and self-assembled to be hydrogels/membranes. Active carboxyl groups ensure the well mixing of zwitterionic chitin nanocrystals and cellulose nanofibrils under neutral and alkaline condition. Electrostatic attraction between amino groups in chitin nanocrystals and carboxyl groups in chitin nanocrystals and cellulose nanofibrils further endows self-assemble property of composite suspensions. Simple standing for 12 h at room temperature is found enough for preparing self-assembled composite hydrogels. By 1-(3-dimethy-laminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxy succinimide (EDC/NHS) mediated chemical crosslinking, the storage modulus of composite hydrogel can achieve almost 8 times higher than self-assembled hydrogel. Well dispersed composite suspensions also can be transformed to be membranes via filtration treatment. The strain increases almost 2.3 times higher with similar tensile strength for cellulose nanofibril rich samples, and chitin nanocrystals mainly contributes to the enhancement in strain of composite membranes.

Understanding viscoelastic behavior of hybrid nanocellulose film based on rheological and electrostatic observation in blended suspension

The effects of TEMPO-mediated oxidized cellulose nanofibril (TOCN) on the viscoelastic behavior and phase of cellulose nanocrystal (CNC) in suspension and film were investigated using polarized optical microscopy, rotational rheometry, and dynamic mechanical analysis. The sodium cation from TOCN changed the electrostatic state of CNC by screening the CNC surface charge. The volume inflation of TOCN locally increased the CNC concentration in the suspension. In turn, the CNC–CNC interactions increased the viscosity and the yield stress. Based on the experimental observation, the changing mechanisms of electrostatic state and particular interaction in the TOCN/CNC suspensions were suggested. In the hybrid film, the time dependency of complex moduli was changed owing to the different networking between CNCs and TOCNs. The CNC–CNC contacts easily collapsed by strain, while the TOCN–TOCN entanglements were slowly altered. This study provides a fundamental understanding of CNC behavior for optimizing processes and composite properties.

Cocultivation of White-Rot Fungi and Microalgae in the Presence of Nanocellulose.

ABSTRACTCocultivation of fungi and algae can result in a mutualistic or antagonistic interaction depending on the species involved and the cultivation conditions. In this study, we investigated the growth behavior and enzymatic activity of two filamentous white-rot fungi (Trametes versicolor and Trametes pubescens) and two freshwater algae (Chlorella vulgaris and Scenedesmus vacuolatus) cocultured in the presence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidized cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC). The growth of fungi and algae was studied in liquid, agar medium, and 3D-printed nanocellulose hydrogels. The results showed that cocultures grew faster under nutrient-rich conditions than in nutrient-depleted conditions. Key cellulose-degrading enzymes, including endoglucanase and laccase activities, were higher in liquid cocultures of T. versicolor and S. vacuolatus in the presence of cellulose compared to single cultures of fungi or algae. Although similar results were observed for cocultures of T. pubescens and C. vulgaris, laccase production diminished over time in these cultures. Fungi and algae were capable of growth in 3D-printed cellulose hydrogels. These results showed that cellulase enzyme production could be enhanced by cocultivating white-rot fungi with freshwater algae under nutrient-rich conditions with TEMPO-CNF and CNC. Additionally, the growth of white-rot fungi and freshwater algae in printed cellulose hydrogels demonstrates the potential use of fungi and algae in hydrogel systems for biotechnological applications, including biofuel production and bio-based fuel cell components.IMPORTANCE Depending on the conditions used to grow fungi and algae in the lab, they can interact in a mutually beneficial or negative way. These interactions could stimulate the organisms to produce enzymes in response to the interaction. We studied how wood decay fungi and freshwater algae grew in the presence and absence of cellulose, one of the basic building blocks of wood. How fungi and algae grew in 3D-printed cellulose hydrogels was also tested. Our results showed that fungi and algae partners produced significantly larger amounts of enzymes that degraded cellulose when grown with cellulose than when grown alone. In addition, fungi and algae were shown to grow in dense nanocellulose hydrogels and could survive the shear conditions during gel structuring while 3D-printing. These cultures could potentially be applied in the biotech industry for applications like energy production from cellulose, biofuel production, and bioremediation of cellulose material.

Tuning the properties of pineapple peel cellulose nanofibrils by TEMPO-mediated oxidation and ball milling

In this study, the oxidized cellulose nanofibrils from pineapple peel (PP-TOCNF) were prepared by TEMPO-mediated oxidation followed by ball milling. The influence of oxidation degree on the structure and properties of PP-TOCNF were investigated, including Fourier transform infrared spectroscopy , X-ray diffraction, atomic force microscope (AFM), X-ray photoelectron spectroscopy and thermogravimetry, as well as the potential application in aerogels. The results suggested that TEMPO oxidation facilitated the dispersion of PP-TOCNF due to the strong electrostatic repulsion between –COO− groups. Regulating oxidation degree by varying NaClO concentration could effectively adjust the –COO− content (0.167–0.550 mmol/g), zeta potential (− 18 to − 34 mV) and rheological properties. The obtained PP-TOCNF showed a long fibrillar structure, whose average diameter and CrI values gradually decreased with the increase of oxidation degree. The PP-TOCNF-based aerogels exhibited a light weight, good porosity, water absorption, and mechanical properties, which also can be easily adjusted by oxidation degree of PP-TOCNF. Furthermore, TEMPO oxidation improved the stability and shape recovery ability of aerogels in water.Graphical abstract

One-step preparation of flexible nanocellulose-based composite hydrogel supercapacitors with high specific capacitance

Supercapacitors (SCs) have ultra-high specific capacitance far exceeding traditional capacitors, and have become an important direction in the field of capacitor research. However, SCs devices based on carbon materials usually require a high temperature environment for N-doping or compounding of pseudocapacitive materials, which greatly increases the manufacturing cost and the difficulty of industrialized production. Herein, we fabricated cellulose-based flexible hydrogel supercapacitors by Fe3+ facilitated one-step ternary composite of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCN)/sulfonated carbon nanotubes (SCNT)/polyaniline (PANI). The combination of these three substances could form a porous and flexible three-dimensional conductive hydrogel just at room temperature. By comparing the performance of supercapacitors prepared with different ratios of three substances, it was found that the best supercapacitors exhibited a high area specific capacitance of 1786 mF/cm2 at a current density of 1 mA/cm2 and excellent flexibility. Therefore, these composite hydrogels are promising for high-performance flexible solid-state supercapacitors.

Hydrangea-like nanocellulose microspheres with high dye adsorption and drug encapsulation prepared by emulsion method

Currently, microspheres with high adsorption capacity play a crucial role in dye adsorption and drug loading. In this study, 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCN) could be used to form nanocellulose microspheres by the emulsion method. The prepared hydrangea-like nanocellulose microspheres presented a stable three-dimensional network porous structure and exhibited excellent adsorption properties. The TOCN microspheres had a high adsorption capacity for methylene blue (MB) and methyl orange (MO) with the optimal adsorption capacity of 412.1 mg g−1 and 286.5 mg g−1 under neutral conditions, respectively. The TOCN microspheres displayed excellent adsorption selectivity on MB/MO mixed dyes, which could be used to selectively adsorb MB. Besides, the encapsulation rate of the positively charged drug doxorubicin hydrochloride (DOX) was as high as 93 %, and the drug loading capacity was as high as 34.5 %. Overall, our prepared nanocellulose microspheres had great potential for application in dye adsorption and drug delivery systems.

Facile synthesis of nanocellulose-based Cu2O/Ag heterostructure as a surface-enhanced Raman scattering substrate for trace dye detection.

Semiconductor metal-oxide/metal heterostructures with synergetic properties have potential applications in photocatalysis and optical sensors. Here, Cu2O sub-micro cubes were synthesized under environmentally benign conditions using 2, 2, 6, 6-tetramethylpyperdine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils as a reducing and stabilizing agent. Then the surface of the Cu2O cubes was decorated with silver nanoparticles (AgNPs) by a substitution reaction. The Cu2O/Ag heterostructures within the cellulose nanofibrils (CNFs) network were employed as a promising surface-enhanced Raman scattering (SERS) assay for efficient sensing of methylene blue (MB), reaching a maximum enhancement factor (EF) of 4.0×104. Their SERS intensities depended on the coverage density of AgNPs and the wavelength of the excitation laser. The excellent SERS performance may result from the charge transfer between Ag and Cu2O molecules and the strong electromagnetic field at the interface. The CNF-Cu2O/Ag substrates were capable of detecting MB dye down to 10-8M level with a relative standard deviation of 10-15%, demonstrating great sensitivity and reproducibility.