Spherical Cellulose Nanocrystals Research Articles

Bio-based Pickering emulsifier from mangosteen residues-derived sodium caseinate grafted spherical cellulose nanocrystals: Stability, rheological properties and microstructure studies

This study focuses on the preparation of mangosteen rind-derived nanocellulose via green ascorbic acid hydrolysis. Subsequently, milk protein-grafted nanocellulose particles were developed as a renewable Pickering emulsifier for water-oil stabilization. The stabilizing efficiency of modified nanocellulose (NC-S) at different caseinate (milk protein) concentrations (1.5, 3.0, and 4.0 % w/v) was tested in a water-in-oil emulsion (W/O ratio of 40:60). At a concentration 3.0 % w/v of caseinate (3.0NC-S), the emulsion exhibited a stronger network of adsorption between water, Pickering emulsifier, and oil. This resulted in reduced oil droplet flocculation, increased stability over a longer period, and favorable emulsifying properties, as depicted in the creaming index profile, oil droplet distribution, and rheology analysis. Since 3.0NC-S demonstrated the best colloidal stability, further focus will be placed on its microstructural properties, comparing them with those of mangosteen rind (MG), cellulose, and nanocellulose (NC-L). The XRD profile indicated that both NC-L and NC-S possessed a cellulose nanocrystal structure characterized as type I beta with a high crystallinity index above 60 %. Morphology investigation shown that the NC-L present in the spherical shape of particles with nanosized ranging at diameters of 11.27 ± 0.50 nm and length 11.76 ± 0.46 nm, while modified NC-S showed increase sized at 14.26 ± 4.60 nm and length 14.96 ± 4.94 nm. The increment of particle sizes from NC-L to NC-S indicated 2.82 × 10−15 mg/m2 of surface protein coverage by caseinate functional groups.

A new facile and efficient strategy for high-yield preparation of spherical cellulose nanocrystals via enzymolysis-mechanical synergy

A new facile and efficient strategy for high-yield preparation of spherical cellulose nanocrystals via enzymolysis-mechanical synergy

Liquid-crystalline assembly of spherical cellulose nanocrystals

Rod-shaped cellulose nanocrystals (CNCs), also called cellulose nanorods (CNRs), possess anisotropic properties that allow for their self-organization into chiral nematic liquid crystals. Interestingly, spherical cellulose nanocrystals (cellulose nanospheres, CNSs) have also been shown to form a chiral liquid-crystalline phase in recent years. Herein, to understand how the similar assembly takes places as particle dimension changes, the organization features of CNSs were investigated. Results of this study demonstrate that above a critical concentration in suspension, CNSs organize into a liquid-crystal phase consisting of periodically parallel-aligned layer structures. This structure persists after suspension drying. In comparison with CNRs, the alignment of CNSs exhibits a shorter layer distance, lower order degree, and weaker long-range orientation. To explain the early stages of tactoid formation, a “caterpillar-like” model was proposed, which was captured by freezing the CNS suspension in an intermediate aggregation state. This structure serves as the fundamental unit for further liquid-crystal assembly.

Construction of spherical cellulose nanocrystals synergized with graphene oxide to stabilize Pickering emulsions

In this study, we prepared spherical cellulose nanocrystals (S-CNCs) and stabilized n-hexadecane Pickering emulsions in conjunction with graphene oxide (GO), exploring the interaction between S-CNCs and GO in the emulsions. Both S-CNCs and GO are amphiphilic and synergistically stabilize Pickering emulsions by adhering to the surface of oil droplets and within the emulsion space through hydrogen bonding. GO's two-dimensional sheets assemble into a 3D network structure, further improving the stability of Pickering emulsions. Consequently, the stability of Pickering emulsions can be adjusted by altering the S-CNCs/GO ratio, modifying the spatial distribution relationship of stabilizers in the emulsions. At an S-CNCs concentration of 1 g/L and a GO concentration of 3 g/L, the Pickering emulsion demonstrated excellent stability and exhibited no delamination after 31 days of storage. Thus, the S-CNCs/GO combination serves as an effective Pickering emulsion stabilizer, utilizing the synergistic effect between the two components.

Preparation of spherical nanocellulose from Gai bamboo and mechanical properties of chitosan/nanocellulose composite

AbstractIn this study, spherical cellulose nanocrystals have been extracted from Gai bamboo (Bambusa blumeana) fibers by sulfuric acid hydrolysis methods. The removal of amorphous components, lignin, and hemicellulose in raw bamboo fiber and the incorporation of sulfate groups were explored via the changes of bond's vibration in Fourier‐infrared spectra and the decrease of onset temperature of thermogravimetric diagram. The results from transmission electron microscopy and X‐ray diffraction revealed that the nanocellulose has a spherical shape with a diameter of 2 to 10 nm and the crystallization index of 70.30% and crystallization degree of 0.77. The improvement of thermal and mechanical properties of the chitosan films loaded with spherical nanocellulose were evaluated. Interestingly, the tensile strength, modulus, and elongation at break for chitosan film loaded with spherical nanocellulose were all increased. The highest value achieved with chitosan film containing nanocellulose of 2 phr. The increase values of tensile strength, modulus and elongation at break were of 63%, 207 MPa, and 30%, respectively. In addition, the moisture absorption of the chitosan film was decreased to 20% indicating that the barrier properties have improved. These improvements illustrated the advancement of nano sized of spherical nanocellulose and the chemical compatibility between nanocellulose and chitosan that resulted in well‐dispersion of nanocellulose in chitosan matrix, developed high performance bionanocomposite.

Preparation of Spherical Cellulose Nanocrystals from Microcrystalline Cellulose by Mixed Acid Hydrolysis with Different Pretreatment Routes

Spherical cellulose nanocrystal (CNC), as a high value cellulose derivative, shows an excellent application potential in biomedicine, food packaging, energy storage, and many other fields due to its special structure. CNC is usually prepared by the mixed acid hydrolysis method from numerous cellulose raw materials. However, the pretreatment route in preparing spherical CNC from cellulose fiber is still used when choosing microcrystalline cellulose (MCC) as the raw material, which is not rigorous and economical. In this work, pretreatment effects on the properties of spherical CNC produced from MCC by mixed acid hydrolysis were systematically studied. Firstly, the necessity of the swelling process in pretreatment was examined. Secondly, the form effects of pretreated MCC (slurry or powder form) before acid hydrolysis in the preparation of spherical CNC were carefully investigated. The results show that the swelling process is not indispensable. Furthermore, the form of pretreated MCC also has a certain influence on the morphology, crystallinity, and thermal stability of spherical CNC. Thus, spherical CNC with different properties can be economically prepared from MCC by selecting different pretreatment routes through mixed acid hydrolysis.

Non-catalyzed formic acid-based process for preparing thermally stable spherical cellulose nanocrystals from mango seed husk

Non-catalyzed formic acid-based process for preparing thermally stable spherical cellulose nanocrystals from mango seed husk

Preparation and separation of pure spherical cellulose nanocrystals from microcrystalline cellulose by complex enzymatic hydrolysis

Spherical cellulose nanocrystals (CNCs), as a new and high value cellulose derivative, shows excellent application potential in many fields due to its special structure. The accurate and effective separation of pure spherical CNCs lays foundation for its further application. In this work, spherical CNCs were prepared by enzymatic hydrolysis of microcrystalline cellulose (MCC) with complex enzymes. In order to determine the optimal separation conditions of pure spherical CNCs, turbidity and Zeta potential were used to analyze the influence of pH on system stability, and the size and morphology of samples were characterized by DLS, AFM and SEM. The results showed that spherical CNCs with particle size of 24–76 nm can be separated from large particles with the help of alkali (pH = 9) dispersion and centrifugation speed of 3000 rpm. After three acid (pH = 4) washes, pure spherical CNCs were extracted and reducing sugars and enzyme proteins were removed. Compared with MCC, spherical CNCs had lower crystallinity but stronger reactivity and higher heat transfer. DTG results showed that the maximum weight loss temperature of spherical CNCs prepared by enzymatic hydrolysis was 309 °C.

Pickering emulsions stabilized by spherical cellulose nanocrystals

Nano cellulose has attracted more attentions as promising stabilizer candidate for Pickering emulsions due to its renewable and biocompatible properties. In this work, spherical cellulose nanocrystals (S-CNCs) (diameter 30–60 nm) were prepared by mixed acid hydrolysis of mercerized microcrystalline cellulose under the treatment of ultrasonic. We characterized the Pickering emulsions stabilized by various S-CNCs concentration in the aqueous phase and visualized their distribution in emulsions system. The diameter of emulsion droplets has no increase after 7 days storage. The emulsions present ultra-low viscosity even at a high S-CNCs concentration in the aqueous phase (5 g/L). Furthermore, noting that Pickering emulsions droplets stabilized by S-CNCs exhibited high stability even pH, ionic strengths, and temperatures changed in wide range. Thus, the S-CNCs acted as a new stabilizer for Pickering emulsion open opportunities for the development of biomedicine, cosmetics, and food applications.

Recycling Baby Diaper Waste into Cellulose and Nanocellulose

The present work reports the baby diaper wastes to recycle into cellulose and nanocellulose. Cellulose was extracted by chlorine-free approach, using acetic and nitric acids. Approximately 25.13 ± 1.02% w/w cellulose was extracted from the used baby diapers. FE-SEM and TEM analysed the morphology of extracted cellulose and nano cellulose. Different carbon atoms and functional groups of the extracted cellulose were identified by CP/MAS 13C NMR and FTIR spectroscopy respectively. Extracted cellulose exhibited a crystallinity of 65.16% as observed from the XRD analysis. A horizontal pattern of weight loss from 310 to 530 °C with an endothermal peak at 355 °C from DSC-TGA confirmed the presence of cellulose. Spherical cellulose nanocrystals (SCNCs) were produced using sulphuric acid hydrolysis with a size range of 50–190 nm. HPLC analysis of SCNCs confirmed the presence of only glucose and a minor fraction of cellobiose, indicating the high purity of the extracted cellulose.

Characterization of Cellulose Nanocrystals Derived from Umbrella Plant (Cyperus alternifolius Linn.)

Plant–based nanocrystals have gained wide research interest due to its application in nano–reinforcement. Hence, the study investigated the stems of umbrella plant as potentials source of cellulose fibers to synthesize cellulose nanocrystals (CNCs). The synthesis of CNCs were conducted using acid hydrolysis with 10 mL 64% w/w sulfuric acid for each gram of purified cellulose at 45°C for 30 min. The surface morphology, structural, physical and thermal properties of CNCs were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier Transform Infrared spectroscopy (FTIR), X–ray diffractometer (XRD), and simultaneous thermal analyzer, respectively. The result showed that the CNCs were mixture of rod–like shape and spherical morphology. The CNC rods were less than 20 nm width and 200–300 nm length when viewed under FESEM. However, the CNC rods were shorter when viewed under TEM and had a width less than 5 nm and length between 20–50 nm. The spherical CNCs that were seen only under TEM were less than 20 nm in diameter. The FTIR spectra showed that the CNCs were composed of crystalline cellulose I wherein the molecular structure of cellulose was preserved after the hydrolysis. The XRD patterns showed that the CNCs were highly crystalline with crystallinity index value of 94.48%. Lastly, the CNCs exhibited a three–stage thermal decomposition behavior.

Designing Highly Luminescent Cellulose Nanocrystals with Modulated Morphology for Multifunctional Bioimaging Materials.

Spherical cellulose nanocrystals (SCNs) and rod-shaped cellulose nanocrystals (RCNs) were extracted from different cellulose materials. The two shape forms of cellulose nanocrystals (CNs) were designed with a combination of isothiocyanate (FITC), and both the obtained FITC-SCNs and FITC-RCNs exhibited high fluorescence brightness. The surfaces of SCNs and RCNs were subjected to a secondary imino group by a Schiff reaction and then covalently bonded to the isothiocyanate group of FITC through a secondary imino group to obtain fluorescent cellulose nanocrystals (FITC-CNs). The absolute ζ-potential and dispersion stability of FITC-CNs (FITC-SCNs and FITC-RCNs) were improved, which also promoted the increase in the fluorescence quantum yield. FITC-RCNs had a fluorescence quantum yield of 30.7%, and FITC-SCNs had a morphological advantage (better dispersion, etc.), resulting in a higher fluorescence quantum yield of 35.9%. Cell cytotoxicity experiments demonstrated that the process of FITC-CNs entering mouse osteoblasts (MC3T3) did not destroy the cell membrane, showing good biocompatibility. On the other hand, FITC-CNs with good dispersibility can significantly enhance poly(vinyl alcohol) (PVA) and poly(lactic acid) (PLA); their mechanical properties were improved (the highest sample reached to 243%) and their fluorescent properties were imparted. This study provides a simple surface functionalization method to produce high-luminance fluorescent materials for bioimaging, multifunctional nanoenhancement/dispersion marking, and anticounterfeiting materials.

Isolation and characterization of cellulose nanocrystals from jackfruit peel

In the present work, sustainable nanomaterials, cellulose, and spherical cellulose nanocrystals (SCNCs) were isolated from the non-edible parts of jackfruit (Artocarpus heterophyllus). Of the three different methods tested, sodium chlorite treatment produced the highest yield of cellulose, 20.08 ± 0.05% w/w (dry weight). Peaks observed in CP/MAS 13C NMR spectrum and FTIR frequencies revealed the presence of α-cellulose and absence of other biomass fractions like hemicellulose and lignin. XRD analysis showed a high crystallinity of 83.42%. An appearance of a sharp endothermal peak at 323 °C in DSC and decomposition patterns between 310–420 °C of TGA confirms the presence of cellulose. Further, Sulphuric acid hydrolysis was employed to produce SCNCs and examined by TEM for the morphology and by HPLC for the presence of glucose.

Characterization and Cellular Internalization of Spherical Cellulose Nanocrystals (CNC) into Normal and Cancerous Fibroblasts.

The aim was to isolate cellulose nanocrystals (CNC) from commercialized oil palm empty fruit bunch cellulose nanofibre (CNF) through sulphuric acid hydrolysis and explore its safeness as a potential nanocarrier. Successful extraction of CNC was confirmed through a field emission scanning electron microscope (FESEM) and attenuated total reflection Fourier transmission infrared (ATR-FTIR) spectrometry analysis. For subsequent cellular uptake study, the spherical CNC was covalently tagged with fluorescein isothiocyanate (FITC), resulting in negative charged FITC-CNC nanospheres with a dispersity (Ð) of 0.371. MTT assay revealed low degree cytotoxicity for both CNC and FITC-CNC against C6 rat glioma and NIH3T3 normal fibroblasts up to 50 µg/mL. FITC conjugation had no contribution to the particle’s toxicity. Through confocal laser scanning microscope (CLSM), synthesized FITC-CNC manifested negligible cellular accumulation, indicating a poor non-selective adsorptive endocytosis into studied cells. Overall, an untargeted CNC-based nanosphere with less cytotoxicity that posed poor selectivity against normal and cancerous cells was successfully synthesized. It can be considered safe and suitable to be developed into targeted nanocarrier.

Effect of the geometry of cellulose nanocrystals on morphology and mechanical performance of dynamically vulcanized PLA/PU blend

Effects of the addition of single but geometrically different cellulose nanocrystals (CNCs) namely cylindrical CNCs (ultrasonic treated), spherical CNCs (chemically treated) and rod-like CNCs (commercial) on microstructural development and mechanical performance of the thermoplastic vulcanizates (TPVs) based on polylactic acid/polyurethane prepolymer (80/20) were studied. It was shown that a fraction of PLA molecules reacted with PU molecules during the dynamic crosslinking process. This was confirmed by the results of gel content measurements which showed an appreciable amount of additional gel content. This phenomenon together with the dynamic vulcanization process facilitated the development of a dual-continuous morphology in the TPV sample which was confirmed by the melt viscoelastic results and TEM micrographs. Interestingly, the addition of spherical CNCs to the TPV led to a remarkable enhancement in its toughness. A similar effect but to a lesser extent was observed in the TPV sample filled with cylindrical CNCs. These results could be explained in terms of a 3D percolated or interconnected network microstructure formed between finely dispersed CNCs localized in PLA and/or between CNCs and the PLA matrix. This fact was evidenced by observation of strong liquid–solid transition in the melt viscoelastic results, as well as TEM and AFM micrographs. On contrary to other counterparts, the rod-like CNCs had a weakening effect on toughness of the TPV which was attributed to their poor dispersion and/or formation of their aggregates which could act as stress concentrators. Moreover, DMTA results showed an almost similar reinforcing effect for the three CNCs on increasing the modulus of the TPV below Tg of the PU and partially compensated the PU reducing effect on modulus in the temperature range between the Tg of PU and PLA.

Preparation and mechanism analysis of morphology‐controlled cellulose nanocrystals via compound enzymatic hydrolysis of eucalyptus pulp

ABSTRACTFirst, making from eucalyptus cellulose fiber, the influences of different compound enzymolysis conditions on the morphology of cellulose nanocrystals (CNCs) were studied. Under the actions of the compound enzyme composed of cellulase and xylanase with the concentration ratio of 9:1, total enzyme concentrations of 10 and 500 U mL−1 and the hydrolysis time of 12 and 5 h, the rod‐like CNCs (length 600 nm, width 30 nm) and the spherical CNCs (40 nm) were obtained, respectively. Subsequently, the crystallinities, chemical structures, and thermal stabilities of the rod‐like and spherical CNCs revealed that, the CNCs structures were still similar to those of the eucalyptus cellulose fiber, the thermal decomposition temperatures of the rod‐like and spherical CNCs (345, 343 °C) were a little lower than that of the eucalyptus cellulose fiber (364 °C). Lastly, the control mechanism of CNC morphology by the compound enzymatic hydrolysis was also discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48407.

Characterization and Cellular Internalization of Spherical Cellulose Nanocrystals (CNC) into Normal and Cancerous Fibroblasts

Characterization and Cellular Internalization of Spherical Cellulose Nanocrystals (CNC) into Normal and Cancerous Fibroblasts

Preparation and characterization of spherical cellulose nanocrystals with high purity by the composite enzymolysis of pulp fibers

The spherical cellulose nanocrystals (CNCs) with high purity were prepared, the processes included composite enzymolysis of pulp fibers and the purification of product. The impurities in the crude product CNCs were analyzed with FTIR, coomassie brilliant blue-G250 and ionic chromatography. The pure CNCs were characterized with SEM, XRD, DLS and TGA. The results indicated that the crude CNCs was flocculated and washed twice with a dilute acid solution (pH = 2) to get pure spherical CNCs, the purity was approximate 99.99%. The obtained pure spherical CNCs had a narrow particle size distribution with diameter 15–40 nm. FTIR and XRD analyses proved that the crystal phase of the spherical CNCs did not change, but the crystallinity decreased slightly compared with pulp fibers. The thermal degradation showed that the spherical CNCs had better thermal stability than one from other methods, and the temperature of maximum weight loss rate (Tmax) was 329.2 °C.

Aminosilane-grafted spherical cellulose nanocrystal aerogel with high CO2 adsorption capacity.

In this study, the cellulose nanocrystals (CNC) obtained by acid hydrolysis of microcrystalline cellulose (MCC) are customized by suspension to obtain a spherical CNC hydrogel. The N-(2-aminoethyl) (3-amino-propyl) methyldimethoxyansile (AEAPMDS) preparation was grafted to spherical CNC hydrogel using a water phase heat treatment. Finally, aerogel samples were obtained by tert-butanol replacement and freeze-drying. The test results confirmed that the aminosilane was grafted on CNC. Electron micrographs and N2 sorption isotherms showed that the pores of the aerogel were partially blocked due to the introduction of AEAPMDS, and the specific surface area was decreased. Due to the presence of chemisorption, the amount of CO2 adsorbed at a pressure of 3bar by the modified aerogel (2.63mmol/g) was greatly improved compared with the unmodified aerogel (0.26mmol/g), and the adsorption results were fit well by the Langmuir model. Thus, our experiments provided the opportunity to develop a new CO2 absorbent material.

Green Templating of Ultraporous Cross-Linked Cellulose Nanocrystal Microparticles

Cellulose nanocrystals (CNCs) are rigid rodlike nanoparticles that are derived from natural cellulose. Their high surface area, mechanical strength, and noncytotoxicity have elicited interest in their use for various applications, including composite and construction materials, cosmetic, food, and biomedical products. However, few methods exist to control the morphology and dimensions of assembled CNC structures in the micrometer range. Here, we use water-in-oil droplet microfluidics to template uniform spherical CNC droplets in a nontoxic and sustainable manner. Subsequent evaporation of the water within the droplets promotes the chemical cross-linking of surface-modified CNCs, resulting in ultraporous and flexible micrometer-sized particles. Changing the size of the microfluidic channel or the concentration of the CNC suspension results in microparticles with tunable sizes. The microparticles swell in polar solvents, with larger swelling observed for microparticles fabricated from less-concentrated CNC ...