Crystalline Cellulose Nanocrystals Research Articles

Nanoencapsulation of oregano essential oil using cellulose nanocrystals extracted from hazelnut shell to enhance shelf life of fruits: Case study: Pears

This study aimed to investigate the potential application of cellulose nanocrystals (CNCs) extracted from an agricultural waste for encapsulation of oregano essential oil (OEO) and subsequently their use for coating to improve the shelf life of pears as a model. By hydrolyzing hazelnut shell cellulose under the optimum conditions, high crystalline CNCs with a zeta potential of −67.8 ± 4.4 mV and a diameter of 157 ± 10 nm were produced. Different concentrations of OEO (10–50 % w/w) were incorporated into CNCs and characterized using FTIR, XRD, SEM and TEM. OEO containing 50 % CNC with the highest EE and LC was selected for coating. Pears were coated with gluten containing 0.5, 1.5 and 2 % encapsulated OEO (EOEO) and pure OEO and stored for 28 days. Physicochemical, microbial and sensory properties of the pears were examined. Microbial analysis showed that EOEO2% was more effective in controlling microbial growth than controls and pure OEO, and a 1.09 Log reduction in bacterial count was recorded on day 28 of storage when compared to control. It was concluded that CNCs produced from an agricultural waste and loaded on an essential oil could be used to extend the shelf life of pear and potentially other fruits.

Insights into thermal degradation kinetics and liquid crystalline behavior of cellulose nanocrystals from the waste of Cajanus cajan (pigeon pea)

Cellulose nanocrystals (CNCs) are essential for advancing nanotechnology and modern science. This work used the Cajanus cajan stem, an agricultural waste, as a lignocellulosic mass, which can serve as a supply of CNCs. After extraction from the Cajanus cajan stem, CNCs have been thoroughly characterized. FTIR (Infrared Spectroscopy) and ssNMR (solid-state Nuclear Magnetic Resonance) successfully validated eliminating additional components from the waste stem. The ssNMR and XRD (X-ray diffraction) were utilized to compare the crystallinity index. For structural analysis, the XRD of cellulose Iβ was simulated to compare with the extracted CNCs. Various mathematical models inferred thermal stability and its degradation kinetics to ensure its high-end applications. Surface analysis established the rod-like shape of the CNCs. Rheological measurements were performed to gauge the liquid crystalline properties of CNC. The anisotropic liquid crystalline CNCs' birefringence proves that the Cajanus cajan stem is a promising resource for making CNCs for cutting-edge applications.

Electrode-customized separator membranes based on self-assembled chiral nematic liquid crystalline cellulose nanocrystals as a natural material strategy for sustainable Li-metal batteries

Despite their enormous potential as a high-energy-density power source, practical applications of Li-metal batteries have been plagued mainly by poor electrochemical longevity. Here, we present an electrode-customized separator (EC separator) based on self-assembled chiral nematic liquid crystalline cellulose nanocrystal (LC–CNC) as a natural material strategy to simultaneously address the electrochemical reversibility issues of both Li-metal anodes and high-capacity cathodes in Li-metal full cells. The EC separator (thickness ∼ 10 μm) comprises a 3-glycidyloxypropyl trimethoxysilane (GPTMS)-modified LC–CNC layer on a polyethylene (PE) separator support layer. The LC–CNC layer enables facile/uniform Li+ flux toward Li-metal anodes owing to its ordered nanoporous channels and nanofluidic ion migration effect, thus improving Li plating/stripping cyclability. The GPTMS of the LC–CNC layer chelates heavy metal ions dissolved from high-capacity LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes, thereby enhancing structural stability of the cathodes. The resulting EC separator enables a Li-metal full cell to improve the volumetric energy density (1016 Wh Lcell−1), cycling retention (84% after 100 cycles vs. 0% for the pristine PE separator), and dimensional stability of the Li-metal anode under constrained cell conditions (thin Li-metal anode (20 μm)/high-capacity NCM811 cathode), which outperform those of previously reported synthetic material-based separators for Li-metal full cells.

Novel Lagenaria siceraria peel waste based cellulose nanocrystals: Isolation and rationalizing H-bonding interactions

Cellulose Nanocrystals (CNCs) play a vital role in modern science & nanotechnology evolution. In this study, non-wood, i.e., Lagenaria siceraria peels, a food-industry waste was used as a source of CNCs. CNCs were successfully isolated from Lagenaria siceraria peels, and detailed characterization has been performed. The Fourier Transform Infrared Spectroscopy (FTIR) was performed to confirm the successful removal of other components from the waste peel. It holds a crystallinity index of 83% examined by X-ray diffraction (XRD). The rod-like morphology is established by Transmission Electron Microscope (TEM), Field Emission Scanning Electron Microscope (FESEM), and Atomic Force Microscope (AFM). CNC acquired excellent thermal stability (>220 °C) established by Thermogravimetric analysis (TGA). The zeta potential value of − 28.77 mV leads to the stability of the suspension. The birefringence of the anisotropic liquid crystalline CNCs proves that Lagenaria siceraria peels as an invaluable source for the production of CNCs for photonic and other advanced applications.

Electric Field‐Driven Control of Cholesteric Cellulose Nanocrystal Orientation and Morphology

AbstractA new insight into the control of the helix axis direction and pitch of an aqueous suspension of cellulose nanocrystal‐derived lyotropic liquid crystals by electric field strength and frequency is presented. At low frequency, liquid crystalline cellulose nanocrystals exhibit anomalous negative birefringence, with the helix axis lying parallel to the electric field, followed by a helix pitch decrease upon increasing the field strength. In contrast, they initially show a positive birefringence at high frequency, with the helix axis perpendicular to the electric field and increasing helix pitch with increasing field strength. When the electric field strength is further increased, the helix axis rotates orthogonally to align parallel to the electric field, producing negative birefringence. Such electric field‐induced manipulation of liquid crystalline cellulose nanocrystal helix axis orientation and pitch can set the stage for various fascinating soft matter nanotechnology applications.

Adsorption of biopolymers onto nanocelluloses for the fabrication of hollow microcapsules

AbstractIn this work, we studied the multilayer adsorption of cellulose nanocrystals and cellulose nanofibers with other polysaccharides such as xyloglucan and chitosan. We showed that the specific interactions between these biopolymers can be exploited to prepare three-dimensional functional materials. Quartz crystal microbalance studies showed that both biopolymers were adsorbed irreversibly on the nanocellulose surfaces. In aqueous media, the maximum amount of adsorbed polymer was higher for the smaller and more crystalline cellulose nanocrystals, compared to cellulose nanofibers. For both nanocelluloses employed, the amount of xyloglucan of the first bilayer was larger than the amount of chitosan adsorbed. Ellipsometry showed that both xyloglucan and chitosan were adsorbed on nanocellulose surfaces. However, at the second layer no mass change was detected by quartz crystal microbalance when xyloglucan was added, while for addition of successive layers of chitosan a decrease of frequency was detected. The water uptake of multilayers was higher for cellulose nanocrystals than for nanofibers, which was ascribed the presence of voids in the nanocrystal layer. Finally, we demonstrated that multilayer adsorption of these biopolymers can be performed on calcium carbonate sacrificial templates, which can then be removed to yield hollow polysaccharide microcapsules.

Enzymatically produced cellulose nanocrystals as reinforcement for waterborne polyurethane and its applications

Waterborne polyurethanes (WBPUs) have been proposed as ecofriendly elastomers with several applications in coatings and adhesives. WBPU’s physicochemical properties can be enhanced by the addition of cellulose nanocrystals (CNCs). The way CNCs are isolated has a strong effect on their properties and can determine their role as reinforcement. In this work, CNCs produced using ancestral endoglucanase (EnCNCs) were used as reinforcement for WBPU and compared with CNC produced by sulfuric acid hydrolysis (AcCNC). The enzymatic method produced highly thermostable and crystalline CNCs. The addition of small contents of EnCNCs improved the thermomechanical stability and mechanical properties of WBPUs, even better than commercial AcCNCs. Besides, WBPU reinforced by adding EnCNCs was studied as a coating for paper materials, increasing its abrasion resistance and as electrospun nanocomposite mats where EnCNCs helped maintaining the morphology of the fibers.

Nanocellulose: Recent Fundamental Advances and Emerging Biological and Biomimicking Applications.

In the effort toward sustainable advanced functional materials, nanocelluloses have attracted extensive recent attention. Nanocelluloses range from rod-like highly crystalline cellulose nanocrystals to longer and more entangled cellulose nanofibers, earlier denoted also as microfibrillated celluloses and bacterial cellulose. In recent years, they have spurred research toward a wide range of applications, ranging from nanocomposites, viscosity modifiers, films, barrier layers, fibers, structural color, gels, aerogels and foams, and energy applications, until filtering membranes, to name a few. Still, nanocelluloses continue to show surprisingly high challenges to master their interactions and tailorability to allow well-controlled assemblies for functional materials. Rather than trying to review the already extensive nanocellulose literature at large, here selected aspects of the recent progress are the focus. Water interactions, which are central for processing for the functional properties, are discussed first. Then advanced hybrid gels toward (multi)stimuli responses, shape-memory materials, self-healing, adhesion and gluing, biological scaffolding, and forensic applications are discussed. Finally, composite fibers are discussed, as well as nanocellulose as a strategy for improvement of photosynthesis-based chemicals production. In summary, selected perspectives toward new directions for sustainable high-tech functional materials science based on nanocelluloses are described.

PH-Responsive Gamma-Irradiated Poly(Acrylic Acid)-Cellulose-Nanocrystal-Reinforced Hydrogels.

A pH-sensitive poly(acrylic acid) composite hydrogel was successfully synthesized via gamma irradiation and reinforced with cellulosic materials of different sizes. Cellulose was extracted from rice husks via alkali and bleaching treatment, and an acid hydrolysis treatment was performed to extract cellulose nanocrystals (CNCs). Morphological observation of cellulose and CNCs using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed diameters of 22–123 μm and 5–16 nm, respectively. The swelling properties of the fabricated poly(acrylic acid)/cellulosic hydrogels were found to respond to changes in pH, and CNC-reinforced hydrogels performed better than cellulose-reinforced hydrogels. The highly crystalline CNC provided a greater storage modulus, hence acting as a better reinforcing material for poly(acrylic acid)-based hydrogels. SEM showed that hydrogels reinforced with the CNC nanofillers contained a homogeneous pore distribution and produced better interfacial interactions than those reinforced with the cellulose microfillers, thus performing better as hydrogels. These findings demonstrate that gamma-irradiated poly(acrylic acid) hydrogels reinforced with CNCs exhibit a better stimuli response toward pH than poly(acrylic acid) hydrogels reinforced with cellulose.

Electro-responsive Liquid Crystalline Nanocelluloses with Reversible Switching.

Liquid crystalline cellulose nanocrystals (CNCs) which can change their structural and optical properties in an electric field could be a new choice for advanced optoelectronic devices. Unfortunately, the exploration of its performance in an electric field is underdeveloped. Hence, we reveal some interesting dielectric coupling activities of liquid crystalline CNC in an electric field. The CNC tactoid is shown to orient its helix axis normal to the electric field direction. Then, as a function of the electric field strength and frequency, the tactoid can be stretched along with a pitch increase, with a deformation mechanism significantly differing at varied frequencies, and finally untwists the helix axis to form a nematic structure upon increasing the electric field strength. Moreover, a straightforward method to visualize the electric field is demonstrated, by combining the CNC uniform lying helix textures with polarized optical microscopy. We envision these understandings could facilitate the development of liquid crystalline CNC in the design of electro-optical devices.

Green method for preparation of cellulose nanocrystals using deep eutectic solvent

An environment-friendly method for obtaining cellulose nanocrystals (CNC) using deep eutectic solvents (DES) was developed. Formation of highly crystalline CNC with average particle dimensions 20 × 100 × 700 nm was confirmed with SEM and AFM. Molecular dynamics simulations demonstrated that the hydrogen bond interactions of the cellulose hydroxyl groups with the urea C=O group and with the chloride ions were the key factors of the destruction of MCC particles in the process of solvation. The type of cellulose crystal structure (Iβ) and the high degree of crystallinity (about 80% according to Segal method) were preserved during treatment with DES. The ability of the prepared CNC to act as a reinforcing filler was tested by introduction of them into the chitosan-based films plasticized with DES. It was found that addition of 2 wt% of CNC led to an increase in the strength of the films from 11.4 up to 20.4 MPa with a simultaneous increase in the elongation at break.

Highly carboxylated and crystalline cellulose nanocrystals from jute fiber by facile ammonium persulfate oxidation

This report describes the synthesis of highly carboxylated cellulose nanocrystals (CNCs) from jute fiber by facile oxidation with ammonium persulfate (APS). The oxidation time effects on microstructure, surface chemistry, crystal structure, and thermal properties were investigated. Crystal-like morphology was obtained with 5.2 nm average particle diameter and 300–500 nm length, depending on the oxidation time. The degree of oxidation (DO) was found to be 0.27: the highest among APS-oxidized CNCs. The carboxylic group amount of 1550 mmol kg−1 was achieved for 16 h oxidation treatment, resulting in high surface charge with the absolute zeta potential value of 40 mV. The DO value was well correlated with the peak intensity of carbonyl group ascertained from FT-IR studies: 0.12 + 0.38(I1730/I1060). As-prepared CNCs showed improved dispersibility in organic solvents up to 15 h. The APS oxidized CNCs showed good thermal stability: the onset decomposition temperature was 240 °C. Using X-ray diffraction method the crystalline index was ascertained as more than 67%. Surface modification of APS-oxidized cellulose nanofibers (CNFs) was confirmed using FT-IR and XPS. Modified CNFs were dispersed in organic solvents such as toluene and THF. Jute is a good candidate material for obtaining highly pure and crystalline CNCs through APS oxidation, exhibiting great potential as a functional material for use in diverse fields.

Influence of precursor size in the hydrothermal synthesis of cellulose-based carbon nanodots and its application towards solar cell sensitization

Abstract The utilization of the abundant yet environmentally polluting green algae as renewable source for new materials is highly desirable. This study presents the utilization of raw cellulose (RC) and cellulose nanocrystals (CNC) extracted from the green algae Cladophora rupestris as precursors for carbon nanodots (CNDs) and its potential use as photosensitizer in solar cell. The results of the hydrothermal treatment of the celluloses afforded spherical CNDs with average dimension of 5.79 ± 1.60 nm (TEM) and having crystalline property (d-spacing of 0.253 ± 0.050 nm) indicating graphitic nature. The size distribution and the ease of the CND formation have been shown to be influenced by the size and morphology of the cellulose precursor. The nanometer-sized crystalline CNCs afforded higher CND yield (54.6 ± 2.71%) compared to the micrometer-sized amorphous RC (37.2 ± 2.76% CND yield). However the size polydispersity of the latter was observed to be narrower at 10.0 ± 3.74 nm (AFM) compared to the former (76.9 ± 73.1 nm; AFM) attributed to clustering or aggregation aided by the presence of hydrophilic functional groups. Indeed, the FT-IR and TOF-SIMs analyses of the CNDs confirmed the presence of hydroxyls, oxides, and carbonyl functional groups that can facilitate the clustering. The CNDs exhibit photoluminescence upon UV irradiation and optical characterization using UV–Vis and Fluorescence Spectroscopy supported the structural and functional group analysis of carbon nanodots. Fabrication of the CND-sensitized solar cell showed the potential of CNDs as photosensitizer albeit in lower yield compared to the positive control.

Hydrochloric Acid Hydrolysis of Pulps from Oil Palm Empty Fruit Bunches to Produce Cellulose Nanocrystals

Cellulose nanocrystals (CNCs) were successfully isolated by hydrochloric acid hydrolysis followed by ultrasonic homogenization of oil palm empty fruit bunches (OPEFB), which are a major form of agricultural waste in Southeast Asia. Currently sulfuric acid is mainly used in CNC preparation to achieve high dispersibility; however, we demonstrated that CNC suspensions prepared from OPEFB by hydrochloric acid hydrolysis remained stable without any sedimentation over 6 months. The obtained CNCs were fully characterized by elemental analysis, electron microscopic observation, X-ray diffraction measurement, and thermal analysis. The OPEFB-derived CNCs exhibited higher aspect ratios of 23–29 and higher thermal stability of 347–359 °C as maximum degradation temperature, as compared with those of woody CNCs prepared by sulfuric acid hydrolysis (15 and 311 °C, respectively). Although as-prepared CNCs showed comparable morphological and physicochemical properties to those prepared from oil palm biomass by other methods including sulfuric acid hydrolysis, use of hydrochloric acid and ultrasonication for hydrolysis of OPEFB was effective to yield crystalline CNCs with long-term nanodispersibility showing clear birefringence.

Crystallization and Thermal Degradation of Green Nanocomposites Based on Lignin Coated Cellulose Nanocrystals and Poly(Lactic Acid)

Cellulose is almost inexhaustible source of raw material comprising at least one-third of all biomass matter. Through deconstruction of cellulose hierarchical structure can be extracted highly crystalline cellulose nanocrystals (CNC) with impressive properties. However, the main barrier in the processing of the nanocomposites based on CNC is their inhomogeneous dispersion and distribution in the non-polar polymer matrix. In this paper is this problem addressed by use of novel hydrophobic lignin coated CNC as a biobased nucleation agents in poly (lactic acid) (PLA) nanocomposites. These green nanocomposites based on natural plant derived substances have enormous potential to replace materials originated from non-renewable resources and show promise of providing degradation back into the environment when they are no longer needed. Resulted composites prepared by twin screw extrusion and injection moulding were characterized by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The addition of L-CNC (1, 2 and 3 wt. %) into PLA increased melt crystallization enthalpy and decreases the cold crystallization enthalpy. The degree of crystallinity (cc) increased from 5.6 % (virgin PLA) to 8.5 % (PLA/1-L-CNC), 10.3 % (PLA/2-L-CNC) and 10.7 % (PLA/3-L-CNC). The wide range of degradation temperatures of lignin coating has been observed starting at 100 °C.

Characteristics of unique HBr-hydrolyzed cellulose nanocrystals from freshwater green algae (Cladophora rupestris) and its reinforcement in starch-based film

Cellulose nanocrystals (CNCs) are promising materials that are readily extracted from plants and other cellulose-containing organisms. In this study, CNCs were isolated from freshwater green algae (Cladophora rupestris) thriving in a volcanic lake, using hydrobromic acid (HBr) hydrolysis. Morphological and structural studies revealed highly crystalline CNCs (94.0% crystallinity index) with preferred orientation to [100] lattice plane as shown by XRD measurements and have an average diameter of 20.0 (±4.4)nm as shown by TEM. Thermal studies showed increased temperature for thermal decomposition of CNCs (381.6°C), which is a result of HBr hydrolysis for CNCs isolation. The isolated CNCs were reinforced into starch based biocomposites via solution casting and evaporation method. Mechanical strength was improved as high as 78% upon addition of 1% cellulose nanocrystals in the films. The produced films are promising materials for their high mechanical strength, biodegradability and availability of raw materials.

Cellulose nanocrystal cationic derivative induces NLRP3 inflammasome-dependent IL-1β secretion associated with mitochondrial ROS production

Crystalline cellulose nanocrystals (CNCs) have emerged as novel materials for a wide variety of important applications such as nanofillers, nanocomposites, surface coatings, regenerative medicine and potential drug delivery. CNCs have a needle-like structure with sizes in the range of 100–200nm long and 5–20nm wide and a mean aspect ratio 10–100. Despite the great potential applicability of CNCs, very little is known about their potential immunogenicity. Needle-like materials have been known to evoke an immune response in particular to activate the (NOD-like receptor, pyrin domain-containing 3)-inflammasome/IL-1β (Interleukin 1β) pathway. In this study we evaluated the capacity of unmodified CNC and its cationic derivatives CNC-AEM (aminoethylmethacrylate)1, CNC-AEM2, CNC-AEMA(aminoethylmethacrylamide)1 and CNC-AEMA2 to stimulate NLRP3-inflammasome/IL-1β pathway and enhance the production of mitochondrial reactive oxygen species (ROS). Mouse macrophage cell line (J774A.1) was stimulated for 24h with 50µg/mL with unmodified CNC and its cationic derivatives. Alternatively, J774A1 or PBMCs (peripheral blood mononuclear cells) were stimulated with CNC-AEMA2 in presence or absence of LPS (lipopolysaccharide). IL-1β secretion was analyzed by ELISA, mitochondrial function by JC-1 staining and ATP content. Intracellular and mitochondrial reactive oxygen species (ROS) were assessed by DCF-DA (2′,7′-dichlorodihydrofluorescein diacetate) and MitoSOX, respectively. Mitochondrial ROS and extracellular ATP were significantly increased in cells treated with CNC-AEMA2, which correlates with the strongest effects on IL-1β secretion in non-primed cells. CNC-AEMA2 also induced IL-1βsecretion in LPS-primed and non-primed PBMCs. Our data suggest that the increases in mitochondrial ROS and ATP release induced by CNC-AEMA2 may be associated with its capability to evoke immune response. We demonstrate the first evidence that newly synthesized cationic cellulose nanocrystal derivative, CNC-AEMA2, has immunogenic properties, which may lead to the development of a potential non-toxic and safe nanomaterial to be used as a novel adjuvant for vaccines.

Aligned bioinspired cellulose nanocrystal-based nanocomposites with synergetic mechanical properties and improved hygromechanical performance.

Natural high-performance materials inspire the pursuit of ordered hard/soft nanocomposite structures at high fractions of reinforcements and with balanced supramolecular interactions. Such biomimetic design principles remain difficult to realize for bulk nanocomposites. Herein, we establish an effective drawing procedure that induces a high orientation of crystalline cellulose nanocrystals (CNCs) in a matrix of carboxymethylcellulose (CMC) at high level of reinforcements (50 vol %). We show such alignment in rather thick bulk films and report synergetic improvement with a simultaneous increase of stiffness, strength, and work-to-fracture as a function of the degree of alignment. Scanning electron microscopy and two-dimensional X-ray diffraction quantify the alignment of the cylindrical nanoparticles and link it to the extent of drawing and improvements in mechanical properties. We further show that the decline in mechanical properties of such waterborne all biobased nanocomposites at high relative humidity can be balanced using supramolecular modulation of the ionic interactions by exchanging the monovalent Na(+) counterion, present in CMC and CNC with di- or trivalent Cu(2+) and Fe(3+). This contribution demonstrates the importance of aligning one-dimensional reinforcements to achieve synergetic improvement in mechanical properties in sustainable bioinspired nanocomposites and suggests pathways to prepare water-stable materials based on a waterborne processing route.