Cellulose Nanocrystals Research Articles

When cellulose nanocrystals meet graphene oxide: Structurally enhanced aerogels for efficient solar steam generation and water purification

Pollution, population growth, and climate change are intensifying global freshwater shortages. Traditional methods of collecting freshwater, such as rainwater harvesting and sewage treatment, have high energy consumption, limiting their implementation in underdeveloped regions. On the other hand, solar-driven seawater evaporation offers a promising solution, purifying water using naturally abundant solar energy. Reduced graphene oxide (rGO) is considered as a strong candidate for this purpose due to its broad spectral absorption. However, its hydrophobicity hinders its direct use in solar steam generators. Here, we report the preparation of a series of cellulose nanocrystal (CNC)-rGO aerogels (CGAs) through a one-pot hydrothermal gelation process, followed by unidirectional freeze-drying. The introduction of CNCs enhances the hydrophilicity and structural stability of the resulting CGAs. The CGAs also feature uniform and unidirectional channels that promote efficient water transport, as confirmed by scanning electron microscopy (SEM) and X-ray microtomography (XMT). The CGAs have an optimized water evaporation rate of 1.80 kg m−2 h−1 under 1 sun irradiation, with 90 % solar-to-vapor energy efficiency. Moreover, durability and seawater desalination tests provide additional evidence for the practicality of CGAs in water purification. It is anticipated the implementation of CGAs will expedite the application of solar steam generators in practical scenarios.

The impact of cellulose nanocrystals on the properties of poly(2‐hydroxyethyl methacrylate)‐based contact lenses

AbstractContact lenses are widely used corrective devices for addressing vision impairments. In addition to their traditional role, these lenses are increasingly applied in personalized care, biosensing, and drug release, thus broadening their application as multifunctional devices. Nanoparticles are often used to introduce new functionalities to these materials. In this context, the role played by different nanoparticles requires attention to ensure that lens manufacture and patient comfort meet the desired criteria. This study investigates the properties of contact lenses prepared by incorporating cellulose nanocrystals into the poly(2‐hydroxyethyl methacrylate) matrix. Using photopolymerization reactions, polyHEMA‐based lenses and nanocomposites containing freeze‐dried and never‐dried nanoparticles were obtained. Fundamental properties of these lenses were evaluated to verify whether the nanoparticles could have a negative effect on the materials. Subsequently, the potential impact of these nanoparticles on the adsorption of model amino acids was investigated. Our findings reveal that the presence of cellulose nanocrystals modifies on lens thickness, light transmittance, mechanical properties, refractive index (RI), and the uptake of amino acids by the contact lenses. This could potentially affect patient comfort and modify the uptake and release of pharmaceutical ingredients by the material. Additionally, it could impact how these materials interact with biomolecules present in the lacrimal fluid.

Rapidly Gelled Lipoic Acid-Based Supramolecular Hydrogel for 3D Printing of Adhesive Bandage.

Developing a strongly adhesive, easily removable, and robust bandage is valuable in trauma emergencies. Poly(lipoic acid) (PLA)-based adhesives with good mechanical properties have been well-developed through a thermal ring-opening polymerization (ROP) method that is easiness. However, the additive manufacturing of PLA-based adhesives remains a challenge. Herein, α-lipoic acid (LA) and trometamol (Tris) are found to rapidly form a supramolecular hydrogel at room temperature with injectability and 3D printing potential. Meanwhile, the synthesized LA-grafted hyaluronic acid and cellulose nanocrystals are involved not only to optimize the extrusion of 3D printing but also to effectively promote fidelity and prevent the inverse closed-loop depolymerization of PLA in water. The hydrogel bandage exhibits strong adhesion to skin while it can be removed with no residue by water flushing, showing protection to neo-tissue during dressing replacement. The in vivo application of the hydrogel bandage significantly promoted wound healing by closing the wound, forming a physical barrier, and providing an anti-inflammatory effect, showing great potential in future clinical applications.

Monitoring the interfacial release rate of resveratrol in Pickering emulsions stabilized by cellulose nanocrystals through the control of the surface coverage

Pickering emulsions (PE) are emulsions stabilized by particles, rather than surfactants like conventional emulsions. This gives them numerous advantages, such as greater stability, reduced toxicity and a tighter drop size distribution. These are just some of the reasons why PEs are booming, particularly in the field of drug delivery. Controlling the release of the active ingredient is thought to depend on the coverage of the emulsion surface by the particles (C). This work first shows how to control C in the case of hexadecane-in-water emulsions stabilized by cellulose nanocrystals (CNCs). It decreases linearly with the salt (NaCl) concentration of the aqueous medium. When resveratrol (RSV), a hydrophobic model molecule, is incorporated into the hexadecane, with an uptake up to 98 ± 3 %, this dependence is lost in favour of a dependence, again linear with RSV concentration. By modelling the release of RSV incorporated into PE of different C, we have demonstrated that k1, the interfacial rate constant of RSV, is controlled by C. CNCs on the droplet surface slow down the release of encapsulated RSV, the higher the droplet surface coverage.

Fabrication of Nanocomposite Hydrogels Based on Cellulose Nanocrystals and Multi‐Walled Carbon Nanotubes for Human Motion Monitoring

AbstractIn this study, a flexible sensor is successfully fabricated using self‐healing nanocomposite hydrogels for monitoring human movement. The eco‐friendly cellulose nanocrystals (CNCs) are used as nano‐reinforcing materials, and the mechanical properties and self‐healing efficiency of the materials are improved. The self‐healing efficiency of hydrogels are realized by introducing a variety of reversible non‐covalent interactions such as hydrogen bonding, borax chelation, and metal coordination. Notably, the mechanical strength and self‐healing efficiency of these nanocomposite hydrogels can reach 2.8 MPa and 89.9%, respectively. Importantly, these self‐healing nanocomposite hydrogels have been widely used in wearable flexible sensors to achieve high sensitivity to large‐scale human movement. It is of great significance to design functional materials with good biocompatibility, sensitivity, and mechanical strength for wearable sensors.

Hierarchical Interfacial Construction by Grafting Cellulose Nanocrystals onto Carbon Fiber for Improving the Mechanical Performance of Epoxy Composites.

Carbon fiber-reinforced composites have been widely used in the aerospace industry because of their superior comprehensive performance, including high strength, low density, fatigue resistance, long service life, etc. The interface between the fiber reinforcement and the matrix is one of the key factors that determines the performance of the composites. The construction of covalent bonding connections between the components has proven to be an effective strategy for improving the interfacial bonding strength but always reduces the toughness. In this work, dual silane coupling agents are applied to covalently connect cellulose nanocrystals (CNCs) onto carbon fibers, constructing hierarchical interfacial connections between the fibers and the epoxy matrix and significantly improving the interfacial bonding strength. As a result, the tensile strength of the epoxy composites increased from 519 MPa to nearly 900 MPa, which provides a potential approach for significantly improving the mechanical performance of composites.

Bioinspired Bouligand-Structured Cellulose Nanocrystals/Poly(vinyl alcohol) Composite Hydrogel for Enhanced Impact Resistance.

Impact-protective materials are gaining importance because of the widespread occurrence of impact damage. Hydrogels have emerged as promising candidates owing to their lightweight and flexible nature. However, achieving soft impact-resistant hydrogels with exceptional stiffness, strength, and toughness remains a challenge. Inspired by the Bouligand structure found in the smasher dactyl club of stomatopods, we propose a straightforward multiscale hierarchical structural design strategy. This strategy integrates self-assembly and salting-out techniques to enhance the impact resistance of soft hydrogels. Rigid cellulose nanocrystals (CNCs) self-assemble into Bouligand-like structures within soft poly(vinyl alcohol) (PVA) matrix via supramolecular interactions. This rational structural design combines the CNC Bouligand structure with a cross-linked network of soft PVA crystalline domains, resulting in a composite hydrogel with impressive mechanical properties: high tensile fracture strength (30.2 MPa), elastic modulus (62.7 MPa), and fracture energy (75.6 kJ m-2), surpassing those of other tough hydrogels. Moreover, the multiscale hierarchical structure facilitates various energy dissipation mechanisms, including crack twisting, tortuous crack paths, and PVA chain orientation, resulting in notable force attenuation (80.4%) in the composite hydrogel. This biomimetic design strategy opens new avenues for developing soft and lightweight impact-resistant materials.

Examination of flow birefringence induced by the shear components along the optical axis using a parallel-plate-type rheometer

In this study, the concept of rheo-optics was applied to explore the flow birefringence induced by the stress components along the camera’s optical axis since it is often overlooked in the traditional theories of photoelastic flow measurement. A novel aspect of this research is that it involved conducting polarization measurements on simple shear flows, specifically from a perspective in which a shear-velocity gradient exists along the camera’s optical axis. A parallel-plate-type rheometer and a polarization camera are employed for these systematic measurements. The experimental findings for dilute aqueous cellulose nanocrystal suspensions demonstrate that the flow birefringence can be expressed as a power law based on the power of the second invariant of the deformation-rate tensor. This suggests that flow birefringence can be universally characterized by the coordinate-independent invariants and a pre-factor determined by the direction of polarization measurement. By adjusting the nonlinear term in the stress-optic law, its applicability could be expanded to include three-dimensional fluid stress fields in which the stress is distributed along the camera’s optical axis.

Cutting edge technology for wastewater treatment using smart nanomaterials: recent trends and futuristic advancements.

Water is a vital component of our existence. Many human activities, such as improper waste disposal from households, industries, hospitals, and synthetic processes, are major contributors to the contamination of water streams. It is the responsibility of every individual to safeguard water resources and reduce pollution. Among the various available wastewater treatment (WWT) methods, smart nanomaterials stand out for their effectiveness in pollutant removal through absorption and adsorption. This paper examines the application of valuable smart nanomaterials in treating wastewater. Various nanomaterials, including cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), nanoadsorbents, nanometals, nanofilters, nanocatalysts, carbon nanotubes (CNTs), nanosilver, nanotitanium dioxide, magnetic nanoparticles, nanozero-valent metallic nanoparticles, nanocomposites, nanofibers, and quantum dots, are identified as promising candidates for WWT. These smart nanomaterials efficiently eliminate toxic substances, microplastics, nanoplastics, and polythene particulates from wastewater. Additionally, the paper discusses comparative studies on the purification efficiency of nanoscience technology versus conventional methods.

Development of biochromic paper strips from cellulose nanocrystals and anthocyanin extract from pomegranate (Punica granatum L.) for colorimetric determination of urea

AbstractAn anthocyanin (ACN) spectroscopic probe was extracted and immobilized into a matrix of cellulose nanocrystals (CNC)/urease enzyme to create a colorimetric nanocomposite film sensor. The ACN@CNC composite is a disposable molecular biosensor that uses urease as a catalyst, ACN as a molecular probe, and CNC as a probe carrier with a high surface area. The ACN spectroscopic probe was isolated from the pomegranate peel (Punica granatum L.). A mordant was applied to fix ACN onto CNC by forming nanoparticles (6–14 nm) of mordant/ACN (M/ACN) complexation. CNC showed diameters in the range of 11–21 nm, and crystal lengths of 55–130 nm. Under acid/base conditions, the ACN probe solution in distilled water exhibited a reversible color change, as shown by the UV–Vis absorption spectra. In order to create a biocomposite film, CNC were reinforced with a sodium alginate biopolymer. Upon exposure to urea in an aqueous solution, the ACN@CNC film biosensor changes color from purple (598 nm) to white (432 nm). The detection limit of urea was determined at 25–450 ppm. Various methods were utilized to investigate the morphological properties of CNC and ACN@CNC films.

Bio‐Inspired Cellulose Composites With Multicolor Separation via Electro‐Thermal and Magneto‐Thermal Techniques for Multifunctional Applications

AbstractBiomimetic optical devices based on cellulose nanocrystals with tunable structural colors have received significant attention recently. However, the limited ability to control multicolor separation beyond simple single‐color modulation restricts its practical applications. Here, a diversified multicolor separation strategy for the cholesteric phase cellulose composite (CPCC) is presented. The CPCC is prepared by integrating a high‐concentration self‐assembled hydroxypropyl cellulose with a cross‐linked poly(acrylic acid‐acrylamide) (P(AA‐AM)) network. By adjusting the cross‐linking degree of P(AA‐AM) in CPCC, Thermally induced multicolor separation is achieved from a homochromatic state at room temperature to multicolor patterned display at elevated temperatures. Furthermore, by utilizing the electric heating effect of conductive carbon oil, the multicolor separation under low voltage is achieved, and based on this, pixelated electro‐thermochromic displays are developed. Additionally, magneto‐thermal multicolor separation induced by introducing FeNi3 nanoparticles is investigated with efficient magnetic induction heating ability into CPCC. The multicolor separation effect is further improved by pixelated distribution of FeNi3 nanoparticles and adjusting the concentration of FeNi3 in each pixel. Finally, thermochromism, electro‐thermochromic, and magneto‐thermochromic functionalities are integrated into the CPCC, achieving advanced multilevel information encryption. This multilevel approach of controlling multicolor separation significantly enhances the functionality of nanocellulose in various potential photonic applications.

Electrodeposited zinc cellulose nanocrystals composite coatings: Morphology, structure, corrosion resistance and electrodeposition process

Nanoparticles, particularly ceramic, have been widely investigated as beneficial additives in electrodeposited zinc coatings. However, exploiting cellulose-based nanocrystals derived from plant sources is attractive due to their cost-effectiveness and sustainability. In this work, we assessed the impact of various concentrations of cellulose nanocrystals, ranging from 0 to 8 v/v%, on the characteristics of zinc coatings obtained through electrodeposition. We investigated the morphology and structure of the zinc deposits using scanning electron microscopy (SEM), x-ray diffraction (XRD), and confocal microscopy (CM). Corrosion resistance was evaluated through mass loss measurements and electrochemical tests including DC (potentiodynamic polarization) and AC (electrochemical impedance spectroscopy) measurements. Increasing cellulose nanocrystal concentrations up to 7 v/v% notably enhanced the corrosion resistance in 0.5 M NaCl solution. In comparison to coatings with no cellulose addition, the 7 v/v% cellulose concentration resulted in: i) an increase in polarization resistance from 586 Ω cm2 to 1850 Ω cm2, ii) a decrease in corrosion current density from 3.21 × 10−5 A/cm2 to 0.76 × 10−5 A/cm2, and iii) a reduction of the corrosion rate from 0.15 mm/year to 0.08 mm/year assessed after 24-h immersion. Furthermore, the addition of this optimal concentration of nanocrystals enhanced current efficiency to approximately 95%, without compromising microhardness, which remained around 184 HV0.1. Additionally, the incorporation of cellulose nanocrystals resulted in a more compact coating with reduced roughness (Ra ∼0.69 μm). This work thus showcases the significant and beneficial impact of cellulose nanocrystals in producing enhanced electrodeposited zinc coatings.

Fabrication of cellulose nanocrystals-incorporated dense Janus membranes for enhanced desalination and oily saline wastewater treatment via membrane distillation

Conventional hydrophobic membranes used in membrane distillation (MD) face significant challenges, such as severe membrane fouling and wetting, when treating surfactant-containing oily wastewater. Current strategies to modify surfaces for anti-fouling and anti-wetting purposes are often complex and time consuming, potentially compromising the flux in MD. This study investigates the characteristics and performance of novel fabricated Janus membranes for the treatment of oily hypersaline wastewater in membrane distillation applications. Janus membranes, which have a dense polyamide layer containing cellulose nanocrystal nanoparticles, were synthesized using the reverse interfacial polymerization (R–IP) method on a polyvinylidene fluoride (PVDF) substrate. Characterization using scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) revealed that the modified Janus membranes exhibited an enhanced hydrophilicity and structural integrity due to the incorporation of cellulose nanocrystal nanoparticles. The fabricated membranes showed a dense surface layer without visible pores or cracks, with micron-scale patterned structures and widely distributed wrinkles, particularly at higher concentrations of cellulose nanocrystal nanoparticles. The desalination performance was evaluated in an air gap membrane distillation setup, where the modified Janus membranes demonstrated higher water vapor fluxes and stable salt rejection, even in the presence of surfactants. The wettability and fouling resistance of the Janus membranes were evaluated, with the PVDF-RIP0.5C membrane showing the highest hydrophilicity and underwater oleophobicity, thereby preventing oil adhesion and membrane fouling. These results underline the potential of Janus membranes with incorporated cellulose nanocrystal nanoparticles for efficient desalination and treatment of oily saline wastewater in the MD process.

Porous cellulose photonic film via controlled unidirectional interlayer freezing for rapid visual sensing

Structure color, arising from the interaction of light with regularly arranged sub-micrometer-sized structures, has spurred interest in sensor design. However, typical cellulose nanocrystal (CNC) photonic films derived from biomass, known for their sustainability and cost-effectiveness, often suffer from limited sensitivity and slow response times due to their dense structure. To address this challenge, we have utilized a unidirectional interlayer freezing-photopolymerization strategy to introduce porous structures into CNC photonic films without compromising their vibrant structural color. This method harnesses ice crystal-induced lamellar pores while preserving the periodic arrangement of CNCs. The underlying mechanism of ice kinetics and CNC assembly is established, highlighting the transition from non-iridescent aerogels to iridescent, porous photonic films. The resulting porous CNC photonic film exhibits apparent color response and rapid sensing capabilities in response to various solvent stimuli, outperforming its non-porous counterparts. We have validated the film as a portable vapor detector for rapid visualized alcohol detection. This approach provides promising developments in sustainable, highly responsive sensor technologies.

A molecular dynamics study of the effects of silane and cellulose nanocrystals at a glass fiber and epoxy interphase

A molecular dynamics study of the effects of silane and cellulose nanocrystals at a glass fiber and epoxy interphase

Creating ultra-strong and recyclable green plastics from marine-sourced alginate-chitosan nanowhisker nanocomposites for controlled release urea fertilizer

In response to the pressing environmental challenge posed by petroleum-derived plastics, the development of green plastics derived from all-biomass nanocomposites offers promising solutions. However, conventional nanocomposites often prioritize enhanced stiffness at the expense of flexibility. We introduce sodium alginate (SA)/chitosan nanowhisker (CSW) nanocomposites, derived entirely from marine-sourced all-biomass, to create ultra-strong and flexible green plastics. Through the synergistic interaction between SA and CSW, these nanocomposites demonstrate simultaneous stiffening and toughening, overcoming the traditional trade-off. Two key mechanisms contribute: geometric reinforcement from the needle-like structure of CSW and electrostatic reinforcement at the interface between oppositely charged CSW and SA. Compared to control SA, the SA/CSW nanocomposites exhibit remarkable enhancements in tensile modulus, strength, and stretchability, by 49%, 85%, and 55%, respectively (7.6 GPa, 223.3 MPa, 14.7%). Cellulose nanocrystals, serving as a control, only stiffen the nanocomposites, adhering to the typical trade-off. Biodegradability in compost can be tailored based on the type of nanofillers. Due to the water resistance of CSW, SA/CSW nanocomposites are proven effective for the controlled release of urea fertilizer in agricultural applications. With recyclability and superior mechanical properties, these marine-sourced green plastics offer a sustainable alternative to conventional plastics, promising significant impact in the eco-plastic industry.

Interplay of Circularly Polarized Light with Molecular and Structural Chirality: Chiral Lanthanide Complexes and Cellulose Nanocrystals

AbstractThe interaction of circularly polarized (CP) light with chiral matter at different scales opens several possibilities of light manipulation in photonic and electronic devices. Here it is shown that in a multilayer architecture, it is possible to take advantage of the polarization‐selective reflection of the nematic arrangement of cellulose nanocrystals and the strong intrinsic CP luminescence (CPL) of the various bands of chiral Eu complexes. In this way, both the intrinsic CPL and total emission of the complex are modified depending on the enantiomer applied and on the detection geometry. This concept may apply for polarization control in electronic and photonic devices and polarized optical cavities.

Extraction and Characterization of Cellulose Nanocrystals (CNCs) from Jute Fibers and Other By-products Towards a Circular Economy Approach

Extraction and Characterization of Cellulose Nanocrystals (CNCs) from Jute Fibers and Other By-products Towards a Circular Economy Approach

Nanoparticle Decorated Cellulose Nanocrystals (CNC) Composites for Energy, Catalysis, and Biomedical Applications

AbstractDecorating cellulose nanocrystals(CNC) with nanoparticles(NPs) allows to engineer novel CNC/NPs composites for advanced technologies and applications. NPs are well‐known for their unique and highly efficient properties. However, NPs present challenges and limitations due to their aggregation, non‐uniform growth, size distribution, and nanotoxicity. CNC surface overcomes most of these drawbacks by providing an attractive matrix/template to grow NPs of desirable morphology, distribution, and functionality. CNC has distinctive properties such as biodegradability, high surface area, low cost, good mechanical strength, surface functionality, and chiral nematic self‐assembly. CNC/NPs composites combine the unique properties of both CNC and NPs. This review highlights the unique characteristics of CNC, NPs, and their composites for energy, catalysis, and biomedical applications. First, different production methods for CNC with their effect on morphology, crystallinity index, and yield are presented. Both organic and inorganic NPs are used to decorate either a pristine or a functionalized CNC surface. In situ nucleation and growth methods are compared with the direct incorporation of pre‐formed NPs on the CNC surface. Applications of CNC/NPs composites are reviewed for energy storage material, conductive materials, catalysts, antibacterial agents, biosensors, and bioimaging. Finally, the current challenges and perspectives are presented for unleashing new possibilities in developing functional CNC‐NPs composites.

Insights into the effect of carboxylated cellulose nanocrystals on mechanical and barrier properties of gelatin films for flexible packaging applications

In this study, gelatin/carboxylated cellulose nanocrystal (cCNC) bionanocomposite films were developed as an eco-friendly alternative to non-biodegradable flexible plastic packaging. Cellulose nanocrystals were modified by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation (cCNC) to strategically interact with amino groups present in the gelatin macromolecular backbone. Gelatin/cCNC bionanocomposite films (0.5–6.0 wt% cCNC) obtained by solution casting were transparent to visible light while displayed high UV-blocking properties. The chemical compatibility between gelatin and cCNC was deepened by electrostatic COO−/NH3+ interactions, as detected by FTIR spectroscopy and morphologically indicated by scanning electron microscopy (SEM). Accordingly, Young's modulus and tensile strength of films were largely increased by 80 and 64 %, respectively, specifically near the cCNC percolation threshold (4 wt%), whereas the water vapor permeability (WVP) was reduced by 52 % at the optimum 6.0 wt% cCNC content in relation to the non-reinforced gelatin matrix (0.10 vs. 0.18 g H2O mm m−2 h−1 kPa−1). The oxygen transmission rates (OTR) of the gelatin/cCNC bionanocomposites were < 0.01 cm3 m-2 day−1, making them technically competitive to most promising biopolymers like polycaprolactone (PCL) and poly(lactic acid) (PLA). This study reveals how TEMPO-oxidized cellulose nanocrystals can broaden the performance of biodegradable gelatin films for use in packaging. The gelatin/cCNC bionanocomposites also represent an effective approach for designing newly sustainability-inspired flexible materials from the surface modification of nanocelluloses targeting specific interactions with protein structures.