Cellulose Nanofiber Film Research Articles

Robust Metal Oxide Adhesion Layers for Cellulose Nanofiber-Based QCM Sensors.

Here, we demonstrate the significant role of robust metal oxide adhesion layers on the cellulose nanofiber (CNF)-based quartz crystal microbalance (QCM) humidity sensor characteristics including sensitivity and stability. In this study, we deposited various metal oxide films (NiO, TiO2, ZnO, and WO3) onto QCM Au electrodes as adhesion layers before drop-casting CNF dispersion water. These metal oxide adhesion layers significantly enhanced the stability of CNF films on QCM sensors even in a high-humidity environment where a conventional adhesion layer (polyethylenimine) for CNF could not maintain stable adhesion. There was a significant difference between different metal oxide layers in the QCM data for humidity sensing. We found a negative correlation between the QCM sensitivity and the water wettability of metal oxide surfaces. Morphology analysis of the deposited CNF films revealed that the center-concentrated CNF microstructures on the metal oxide adhesion layers rigorously explained the observed negative correlation between the sensitivity and the wettability of metal oxide surfaces. This trend was further confirmed by gradually changing the hydrophobicity of the NiO adhesion surfaces. Thus, the proposed strategy using robust metal oxide adhesion layers will be a foundation for further development of various CNF-based QCM gas sensors.

Development of stopped-flow hyper-CEST NMR method on recirculating hyperpolarization system as applied to void space analysis in polymers.

129Xe NMR spectroscopy of polymers can provide important information on void spaces, sometimes called free volume, in polymers. Unfortunately, the spectroscopy's low sensitivity has limited its widespread use in both academic and industrial research. In order to overcome such a difficult situation, hyper-CEST method which employs hyperpolarization and CEST techniques, is examined after the introduction of recirculation and subtraction modes. Alongside the incorporated stopped-flow technique, these modes were very efficient in detecting very weak hidden signals from cellulose nanofiber (CNF) and silk fibroin (SF) films and in discussing the void space in these polymers. From the analysis of detailed saturation frequency dependence in the increment of 100Hz, the chemical shifts of hidden peaks were successfully determined to give reasonable values for the size of void space in CNF and SF. Application on thermoplastic polyurethane film also supported our method of analysis. The subtraction mode was very efficient in judging the presence or absence of any peak at a fixed saturation frequency. These facts support that the mode will surely be useful in the future exploratory study of very weak hidden signals.

Functionalized cellulose nanofiber films as potential substitutes for Japanese paper

Japanese papers (JPs) are among the most common materials used for the restoration of historical papers. However, they have low transparency and may structure the paper surface. To overcome the limitations of JPs, in the present work, films of cellulose nanofibers with and without lignin (LCNFs and CNFs, respectively) were explored. For this, chemically different LCNFs (carboxylated by TEMPO-mediated oxidation using variable oxidant amount and sulfated with deep eutectic solvent) and two reference CNFs were produced from Eucalyptus kraft pulps. Lignin hindered slightly the introduction of carboxyl groups into the cellulose structure, but did not affect the incorporation of sulfate groups. (L)CNFs gave films with better mechanical properties than those determined for three types of JP (tensile strength of 79–142 MPa (±11) vs 3.5–13.0 MPa (±0.4) and Young's modulus of 4900–5900 MPa (±300) vs 200–1800 MPa (±70)). Additionally, the (L)CNF films exhibited lower water vapor transmission rates (132–312 g.m−2.day−1) compared to the JPs (685–719 g.m−2.day−1), and a higher transparency (up to 89% and ≤82% for JPs). Besides thermal stability, all properties studied favored (L)CNF films over JPs, indicating their strong potential for restoration/conservation applications. This systematic comparison between the properties of (L)CNF films and JPs has never been conducted before.

Dual regulation of thermal conductivity and mechanical performance of nano cellulose-based composite via mimicking plant cell wall structure

Combining thermal conductive fillers and flexible polymers is an agile approach to fabricating composites with heat-conducting performance. However, the thermal conductivity of the composites is hard to reach an equal level to the functional fillers. The mainspring is that the thermally conductive pathways within the composite could not be well-constructed due to the air-induced interface thermal resistance. Herein, inspired by the plant cell wall structure, polyvinyl alcohol (PVA) with abundant hydroxyl groups was adopted as a binder for boosting the thermally conductive pathways construction between cellulose nanofiber (CNF) and alkalized hexagonal boron nitride (BN-OH), also for strengthening the mechanical performance of the composite. The results showed that the tensile strength and through-plane thermal conductivity of the composite were high up to 91.0 MPa and 2.2 W m−1 K−1 at 40 wt% PVA content, exhibiting 121 % and 450 % enhancements compared to pure CNF film (41.2 MPa and 0.4 W m−1 K−1). Moreover, the composite also presented high thermal stability (decomposition temperature of onset was 218 °C) and good hydrophobicity properties. Overall, this study innovatively proposes an idea for enhancing the thermal conductivity and improving the mechanical properties of the composite, which is indispensable for developing thermal management materials for next-generation electronics.

Development of a cellulose nanofiber composite film containing CuO/ZnO nanoparticles and its human norovirus inactivation properties in clams

Human norovirus (HuNoV) threatens human health worldwide, highlighting the critical need for antiviral materials. In this study, copper and zinc nanoparticles (NPs) as inorganic antiviral materials and a cellulose nanofiber (CNF) were selected to construct a hybrid inorganic-organic composite film (CuO/ZnO NPs-CNF) against MS2 and murine norovirus 1 (MNV-1) (surrogates for HuNoV) viruses. Selected NPs concentrations (50 µM of CuO NPs and 5 mM of ZnO NPs) showed non-toxicity (89.88 % of cell viability) through the MTT assay. Upon the development and characterization of the CuO/ZnO NPs-CNF film, high compatibility between CuO/ZnO NPs and CNF was identified, along with consistent thickness, low moisture content, and water solubility. A synergistic antiviral effect was exhibited in vitro and on the film against MS2 and MNV-1 in the mentioned co-treated inorganic matrix within 1 h. The antiviral stability of the film was also maintained at various temperatures (−18 °C, 5 °C, and 25 °C) and humidities (20–30 %, 50–60 %, and 70–80 %). When a synergistic antiviral effect was exhibited on the CuO/ZnO NPs-CNF film against both MS2 and MNV-1, mechanisms analysis by SDS-PAGE and RT-qPCR revealed that there were damages to both capsid protein and RdRP. The application of CuO/ZnO NPs-CNF film on clams resulted in a significant decrease in the survival rate of MS2 by up to 65.67 % and MNV-1 by up to 78.62 % when treated at low temperatures compared to the CNF film. Taken together, these results suggest that the CuO/ZnO NPs-CNF film could be used as potential anti-HuNoV agent in the food industry.

Biomass-derived epoxy resin and its application for high-performance natural fiber composites

The development of bio-based materials with superior comprehensive properties from biomass resources remains a significant challenge, providing an alternative to conventional petroleum-based materials. This study explores the lignin-derived vanillyl alcohol epoxy (VAE) resin-containing mono and di (m&d) epoxy structure as an adhesive to develop environment-friendly natural fiber-reinforced composites to reduce the carbon footprint. The synthesized m&dVAE containing mono and di-epoxidized (m&d) aromatic rings, when cured with 4, 4´-diaminodiphenyl methane (DDM) hardener, exhibits higher record tensile strength ∼124.0 ± 8.43 MPa and tensile modulus ∼2.88 ± 0.35 GPa compared to a commercial petroleum-based epoxy, diglycidyl ether bisphenol A (DGEBA) thermoset. Additionally, it demonstrated higher adhesion shear strength (∼19.16 ± 0.58 MPa) with cellulose nanofibers film than DGEBA. Moreover, fabricated green composite possesses excellent flexural strength of ∼203.72 ± 2.08 MPa and stiffness of ∼11.58 ± 0.38 GPa than the petroleum-based thermoset composite. The composite’s fracture surface morphology shows that the resin and fibers have good interfacial adhesion. Notably, the sustainable composite showed good hydrophobicity and an excellent heat-resistant index of 144.4°C. The m&dVAE resin can be an alternative to petroleum-based resins as an adhesive, and its environment-friendly sustainable composite could be a promising candidate to replace synthetic materials for high-performance structural applications.

Cellulose Nanofiber-Based Nanocomposite Films with Efficient Electromagnetic Interference Shielding and Fire-Resistant Performance.

Cellulose nanofiber (CNF) has been widely used as a flexible and lightweight polymer matrix for electromagnetic shielding and thermally conductive composite films because of its excellent mechanical strength, environmental performance, and low cost. However, the lack of flame retardancy seriously hinders its further application. Herein, renewable and biomass-sourced l-arginine (AR) was used to surface-modify ammonium polyphosphate (APP) and an environmentally friendly biobased flame retardant was synthesized by the coordination of zinc sulfate heptahydrate (ZnSO4·7H2O), which was named AAZ. AAZ was deposited on the surface of CNF by electrostatic adsorption and Zn2+ complexation. The biobased compatibilizer Triton X-100 was employed to assist the exfoliation of graphene nanoplatelets (GNPs) and their dispersion in the CNF matrix. Due to the formation of a dense lamellar layer resembling a shell structure, the CNF/GNPs composite films with a tensile strength of 52 MPa were obtained via vacuum-assisted filtration. Because the phosphorus-containing group produces a protective layer of PxOy compound and promotes the formation of a carbon layer by CNF and the combustion releases ammonia gas, the fire-resistant performance of the composite films was greatly improved. Compared with the pure CNF film, the composite film exhibits 33% reduction in PHRR value and 40% reduction in THR. In addition, the CNF/GNPs composite film with 20 wt % GNPs possessed high conductivity (2079.2 S/m) and electromagnetic interference (EMI) shielding effectiveness (37 dB). The ultrathin CNF/GNPs composite films have excellent potential for use as efficient flame retardant and EMI shielding materials.

Multifunctional pectin and lignin-containing cellulose nanofiber films with improved UV resistance and mechanical properties

This study aimed to study the real-time interaction of apple pectin and LCNF using Quartz crystal microbalance with dissipation monitoring (QCM-D) to understand the compositional factors that influence their film formation and assess the impact of varying polymer ratios (0–100%) on the UV resistance, hydrophobicity, and mechanical properties of resulting composite films. Results revealed that apple pectin forms partially irreversible interaction with LCNF, evidenced by a frequency change of 14.9 Hz after the final rinsing stage. This finding was supported by FTIR of the composite films, demonstrated by a shift of the broader –OH stretching vibration at 3325 cm−1 to 3302 cm−1 due to the formation of strong hydrogen bonding. LCNF-based films (LCNF >50%) were less soluble in water compared to pectin-based films (pectin >50%) due to less permeable structure and hydrophobic lignin which interferes in hydrogen bonding with water. Pectin-based films displayed high transparency (%Transmittance >89% at 650 nm) and lower hydrophobicity. Due to the presence of lignin chromophores, the UV shielding property was the highest for LCNF-based films as it almost completely shielded the UV spectrum (%T ∼0 at 320 nm). The reinforcement provided by LCNF significantly enhanced the mechanical properties of the films. Consequently, this study offers valuable insights into the real-time interaction dynamics between apple pectin and LCNF, facilitating the development of biocomposite films with versatile properties that hold significant promise for a wide range of applications.

A robust, eco-friendly, and biodegradable cellulose nanofiber composite film for highly effective formaldehyde removal at room temperature

Formaldehyde (HCHO) poses a significant threat as a common indoor air pollutant, leading to various health issues. However, effectively addressing HCHO removal at room temperature remains a considerable challenge. This paper presents the preparation of a robust, eco-friendly, and biodegradable composite cellulose nanofiber film, incorporating CeO2-Ag@MnO2 catalysts and TEMPO-oxidized cellulose nanofiber (TOCNF), for high-efficiency HCHO removal at room temperature. A CeO2-Ag@MnO2 ternary catalyst with a core–shell structure was constructed to enhance the catalytic oxidation activity and stability. This structure increased the number of active sites on the catalyst surface and enhanced the interfacial synergistic effect of Ce-Ag-Mn. The TOCNF physically adsorbed HCHO in the composite film, while the catalyst oxidized it to CO2 and water. The composite films, particularly those with 20 wt% CeO2-Ag@MnO2 catalyst, exhibited high HCHO removal rates of 91.2 % at 20 °C and 99.6 % at 60 °C. Furthermore, the TOCNF/20 CAM composite films demonstrated excellent mechanical properties and degradability. This composite film offers an efficient and eco-friendly solution for the catalytic oxidation of HCHO at room temperature.

Development of smart colorimetric indicators for tracking kimchi freshness by loading aronia extract in agar, κ-carrageenan, and cellulose nanofiber films

Color indicator films incorporating aronia extract powder (AEP) and biopolymers like agar, carrageenan, and cellulose nanofiber (CNF) were developed to monitor kimchi freshness. AEP-containing films showed strong UV-barrier properties, and reduced light transmittance by 99.12 % for agar, 98.86 % for carrageenan, and 98.67 % for CNF-based films. All AEP-films exhibited high sensitivity to pH changes and vapor exposure to ammonia and acetic acid. Color change notably influenced by the polymer type, particularly evident with ammonia vapor exposure, especially in the AEP/carrageenan film. The chemical structure and thermal stability of the biopolymers remained unchanged after AEP-addition. Tensile strength increased by 24.2 % for AEP/CNF but decreased by 19.4 % for AEP/agar and 24.3 % for AEP/carrageenan films. AEP-containing films displayed strong antioxidant activity, with 99 % free radical scavenging in ABTS and ~ 80 % in DPPH assays. Alkalized AEP-indicator films were more effective in detecting color changes during kimchi packaging tests. Among the labels, alkalized AEP/agar film showed the most obvious color change from green-gray (fresh kimchi, pH 5.5, acidity 0.48 %) to pale brown (optimal fermentation, pH 4.6, acidity 0.70 %), and pale violet-brown (over-fermented, pH 3.80, acidity 1.35 %). Alkalized AEP-indicator films offer promising real-time detection of packed fermented foods like kimchi.

Novel cellulose-based films with highly efficient photothermal performance for sustainable solar evaporation and solar-thermal power generation

Solar-driven interfacial evaporation has received substantial attention in a variety of applications, including water purification, seawater desalination, and energy production. However, creating a straightforward, adaptable, and scalable method for correctly integrating hybrid solar-thermal systems continues to be a challenging task. Herein, we propose an economical, scalable, and environmentally friendly approach for achieving synergistic coupling of interfacial solar energy conversion for evaporation and low-grade thermal energy conversion to electricity by incorporating zinc oxide (ZnO) nanoparticle-modified MXene (ZNM- MXene) into cellulose nanofiber (CNF) films. The vacuum filtering approach produces CNF@ZNM-MXene composite films with enhanced photothermal conversion efficiency, capillary hydrophilicity, and thermal localization. Because of its rapid water transport capability, excellent sunlight absorption, and efficient solar-thermal conversion under 1 kW m−2 irradiance, the CNF@ZNM-MXene solar evaporator's evaporation rate reaches 1.27 kg m−2 h−1, and the solar-vapor conversion efficiency is as high as 82.15%, outperforming most previously reported solar evaporators. Moreover, when compared to a standalone thermoelectric (TE) module, the output power of the solar thermal conversion system coupled with a CNF@ZNM-MXene composite films and a TE module is boosted by 15.32 times. This work offers a practical and effective method for simultaneously capturing solar energy and desalinating saltwater.

Cellulose Nanofiber Films with Gold Nanoparticles Electrostatically Adsorbed for Facile Surface-Enhanced Raman Scattering Detection.

Cellulose nanofiber (CNF) holds great promise in applications such as surface-enhanced Raman scattering (SERS), catalysis, esthesia, and detection. This study aimed to build novel CNF-based SERS substrates through a facile synthetic method. Citrate-reduced gold nanoparticles (AuNPs) were adsorbed on the cationized CNF surface due to electrostatic interactions, and uniform AuNPs@(2,3-epoxypropyl trimethylammonium chloride)EPTMAC@CNF flexible SERS substrates were prepared by a simple vacuum-assisted filtration method. The probe molecule methylene blue was chosen to assess the performance of the CNF-based SERS substrate with a sensitivity up to 10-9 M, superior signal reproducibility (relative standard deviation (RSD) = 4.67%), and storage stability (more than 30 days). Tensile strength tests indicated that the CNF-based films had good mechanical properties. In addition, CNF-based substrates can easily capture and visually identify microplastics in water. These results demonstrate the potential application of the flexible, self-assembled AuNPs@EPTMAC@CNF flexible SERS substrate for prompt and sensitive detection of trace substances.

Effects of coffee bean types on the characteristics of carbon dots and their use for manufacturing cellulose nanofibers-based films for active packaging of meat

CDs (carbon dots) were made through a hydrothermal process using three different types of coffee grounds (raw, roasted, and spent), and their physicochemical and optical properties were thoroughly studied. CNF (cellulose nanofibers)-based active packaging films were made and characterized by incorporating the CDs. The introduction of CDs improved the tensile strength of the CNF-based films by 26.1% and provided excellent UV-blocking ability by blocking 98.8% of UV-B and 87.4% of UV-A without sacrificing the film’s transparency. The CD-loaded CNF films showed strong antioxidant properties with ABTS radical and DPPH radical removal rates of 98.2% and 78.8%, respectively. Additionally, these films showed effective antimicrobial potential and significantly reduced the progress of E. coli and L. monocytogenes after 12 h of exposure. Packaging tests were performed at 4 °C for 21 days, which depicted that minced pork packaged with the CD-added CNF films preserves the quality of packaged meat in terms of appearance, pH, total viable colonies, and TBARS (thiobarbituric acid reactive substances). It is expected that manufacturing functional fillers (CDs) using waste resources generated in the food industry and developing active packaging films using them will not only extend the shelf life of packaged foods but also help in resource recycling and solving environmental problems.

Self-powered wearable human-computer interaction system based on kapok cellulose nanofibers

As wearable devices in the fields of medical health, human–computer interaction, and motion detection continue to diversify in their materials and forms, they show vast application potential. Cellulose materials are emerging as prominent materials for fabricating flexible wearable electronic devices because of their favorable skin compatibility, cost-effectiveness, and abundance. However, there is little research on the use of kapok cellulose in wearable electronics. This study addresses this knowledge gap by exploring the high-yield production and waste recycling potential of kapok cellulose. To overcome the limitations of conventional cellulose films, such as poor flexibility, high haze, and limited light transmittance, a kapok cellulose nanofiber film (KCNF) with a transparency of > 90 % and a tensile strain of > 20 % is prepared. The use of the KCNF as a friction electric material in the triboelectric nanogenerator (TENG) improves its electrical output performance by 228 % and permits its comfortable long-term attachment to the skin for self-powered tactile sensing applications, including game control, text input, and smart medical devices. This study demonstrates that the exploration of KCNF materials expands the options available for developing wearable electronic devices with numerous potential applications.

A tough, reversible and highly sensitive humidity actuator based on cellulose nanofiber films by intercalation modulated plasticization

Cellulose nanofiber was an ideal candidate for humidity actuators based on its wide availability, biocompatibility and excellent hydrophilicity. However, conventional cellulose nanofiber-based actuators faced challenges like poor water resistance, flexibility, and sensitivity. Herein, water-resistant, flexible, and highly sensitive cross-linked cellulose nanofibers (CCNF) single-layer humidity actuators with remarkable reversible humidity responsiveness were prepared by combining the green click chemistry modification and intercalation modulated plasticization (IMP). The incorporation of phenyl ring and the crosslinked network structure in CCNF films contributed to its improved water resistance and mechanical properties (with a stress increased from 85.9 ± 3.1 MPa to 141.2 ± 21.5 MPa). SEM analysis confirmed enhanced interlaminar sliding properties facilitated by IMP. This resulted in increased flexibility and toughness of CCNF films, with a strain of 11.5 % and toughness of 9.9 MJ/m3. These improvements efficiently enhanced humidity sensitivity for cellulose nanofiber, with a 4.8-fold increase in bending curvature and a response time of only 3.4 ± 0.1 s. Finally, the good humidity sensitivity of modified CNF can be easily imparted to carbon nanotubes (CNTs) via simple self-assembly method, thus leading to a high-performance humidity-responsive actuator. The click chemistry modification and IMP offer a new avenue to fabricate tough, reversible and highly sensitive humidity actuator based on cellulose nanofiber.

High-performance flexible triboelectric nanogenerator based on micropatterned allicin-grafted cellulose film

Developing high-performance cellulose-based flexible triboelectric nanogenerators (TENGs) remains challenging due to the weak surface polarity of cellulose. In this work, allicin-grafted cellulose nanofiber films (Alc-CNF) containing square micropatterns on the surface are fabricated, and their successful application for bio-based TENGs with enhanced triboelectric output performance is demonstrated. Allicin was chemically grafted onto the CNFs through the utilization of 'thio-ene' click chemistry. Square micropatterns with different gaps (40, 50, 60 μm) between patterns were created on the CNF film using lithography, then casting Alc-CNF suspension and drying in cleanroom conditions. The Alc-CNF TENG, having a 50 μm gap between the patterns, showed an output power of 87 μW (387 mW/m2), 260 times larger than the pure CNF TENG and 35 times larger than the no-patterned Alc-CNF TENG. The performance is related to the higher surface polarity, electron-donating tendency, and surface roughness of the Alc-CNF film.

Adaptive plasticity of auxetic kirigami hydrogel fabricated from anisotropic swelling of cellulose nanofiber film

ABSTRACT Hydrogels are flexible materials that typically accommodate elongation with positive Poisson’s ratios. Auxetic property, i.e. the negative Poisson’s ratio, of elastic materials can be macroscopically implemented by the structural design of the continuum. We realize it without mold for hydrogel made of cellulose nanofibers (CNFs). The complex structural design of auxetic Kirigami is first implemented on the dry CNF film, i.e. so-called nanopaper, by laser processing, and the CNF hydrogel is formed by dipping the film in liquid water. The CNF films show anisotropic swelling where drastic volumetric change mainly originates from increase in the thickness. This anisotropy makes the design and fabrication of the emergent Kirigami hydrogel straightforward. We characterize the flexibility of this mechanical metamaterial made of hydrogel by cyclic tensile loading starting from the initial end-to-end distance of dry sample. The tensile load at the maximum strain decreases with the increasing number of cycles. Furthermore, the necessary work up to the maximum strain even decreases to the negative value, while the work of restoration to the original end-to-end distance increases from the negative value to the positive. The equilibrium strain where the force changes the sign increases to reach a plateau. This plastic deformation due to the cyclic loading can be regarded as the adaptive response without fracture to the applied dynamic loading input.

In situ Synthesis of Single Layered Metal-Organic Frameworks via Inkjet Printing on a Cellulose Nanofiber Film.

The inkjet printing is a simple method to develop pattern-controlled 2D metal-organic frameworks (MOFs) due to its cost-effectiveness and ease of operation. Despite the sophisticated structures of MOF crystals, the MOF surfaces are easily contaminated by the adsorption of an ink solution, and the printing nozzle can be clogged by the aggregates of MOFs during printing. Unlike the mixture inks of MOFs and a carrier medium, the surface-specific patterning by in situ synthesis provides the film surface with the controlled patterns of an MOF single layer having different morphologies of MOFs without changing the ink cartridges. It enables facile printing due to the low viscosity of inks and escapes the risk of nozzle clogging because MOFs are synthesized at the printed patterns on the substrates. The ion-exchanged cellulose nanofiber (CNF) films form strong coordination with metal ions enhancing the stability of the MOFs on the film surface. It also demonstrates the controlled coverage of the MOFs by the printing pass number and the carboxylate content of CNF and the tunable adsorption of the guest molecules for different loading capacities of the printed patterns.

Flexible cellulose nanofibers/MXene composite films for UV-shielding packaging

Cellulose nanofibers (CNF) based films are promising packaging materials, but the lack of special functions (especially UV-shielding property) usually restrict their further applications. In this work, MXene was incorporated into the CNF film by a direct solvent volatilization induced film forming method to study its UV-shielding property for the first time, which avoided the using of a vacuum filtration equipment. The composite films containing glycerin could be folded repeatedly without breaking, showing good flexibility. The structure and properties of MXene/CNF composite films (CMF) were characterized systematically. The results showed that MXene distributed uniformly in the CNF film matrix and there was strong hydrogen bonding interaction between CNF and MXene. The tensile strength and Young's modulus of the composite films could reach 117.5 MPa and 2.23 GPa, which was 54.1 % and 59.2 % higher than those of pure CNF film, respectively. With the increase of MXene content, both the UVA and UVB shielding percentages increased significantly from 17.2 % and 25.5 % to 100.0 %, showing excellent UV-shielding property. Moreover, CMF exhibited a low oxygen permeability (OP) value of 0.39 cc μm d−1 m−2 kPa−1, a low water vapor permeability (WVP) value of 5.13 × 10−11 g−1s−1Pa−1 and a high antibacterial rate against E. coli (94.1 % at 24 h), showing potential application in the packaging field.

A honeycomb-inspired carboxymethyl chitosan-covalently link NH2-black phosphorene biobased cellulose green nanocomposites with tremendously enhancement fire safety and thermal conductivity

Biobased carboxymethyl chitosan-modified black phosphorene (BP-CMC) was prepared through an amidation reaction between amino group functionalized black phosphorene (NH2-BP) and CMC. Density functional theory (DTF) express that the adsorption energy between urea and phosphene is −6.28 eV, indicating a strong interaction. The resulting BP-CMC was further applied to reinforce the mechanical, flame-retardant and thermal conductivity performance of honeycomb cellulose nanofiber (CNF) film via vacuum filtration. Cone calorimetry test (CCT) result exhibits that the introduction of 30 wt% BP-CMC significantly promoted the fire safety of CNF. For instance, a 98.41% reduction in smoke production rate (SPR), 92.00 % decline in CO release and a 61.31% decrease in heat release rate (HRR) were observed compared to neat CNF. Furthermore, Thermogravimetric infrared (TG-IR) indicates a significant decrease in the release of flammable gases. Raman spectra verify that the incorporation of 30 wt% BP-CMC improves the graphitization degree of residual chars, thus limiting the transfer of heat and oxygen. The improvement in fire safety is attributed to the formation of an intumescent flame-retardant system, which is rich in carbon source (CMC), acid source (BP) and gas source (amino). Simultaneously, the introduction of 30 wt% BP-CMC into CNF leads to considerable enhancement in thermal conductivity (up to 17.49 %), thermal diffusion (utmost to 43.45 %) and heat capacity (increased by 19.23 %). Moreover, the 30 wt % addition of BP-CMC into CNF possesses excellent mechanical properties with the improvement of toughness (increased by 143.50 %) and tensile strength (increased by 140.90 %). This strategy not only provides a new strategy for functionalizing BP but also upgrades the application potential of BP nanosheets in the fire safety of polymer composite films.