International Journal of Polymer Science

International Journal of Polymer Science / 2019 / Article
Special Issue

Syntheses and Biomedical Applications of Functional Polymers

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Review Article | Open Access

Volume 2019 |Article ID 1767028 | 10 pages | https://doi.org/10.1155/2019/1767028

Preparation and Applications of the Cellulose Nanocrystal

Academic Editor: Jianxun Ding
Received23 May 2019
Revised12 Sep 2019
Accepted08 Oct 2019
Published16 Nov 2019

Abstract

Cellulose widely existed in plants and bacteria, which takes important effect on the synthesis of macromolecule polymer material. Because of its great material properties, the cellulose nanocrystal (CNC) showed its necessary prospect in various industrial applications. As a renewable future material, the preparation methods of the CNC were reviewed in this paper. Meanwhile, the important applications of CNC in the field of composites, barrier film, electronics, and energy consumption were also mentioned with brief introductions. The summarized preparations and considerable applications provided operable ideas and methods for the future high-end and eco-friendly functional composites. Suggestions for potential applications were also discussed.

1. Introduction

Cellulose is a macromolecular polysaccharide composed of glucose. It is also the most diverse and widespread group of polysaccharides in nature. As a kind of natural crystalline macromolecular compound, the cellulose nanocrystal (CNC) widely exists in the plant fibers and the capsular polysaccharide of bacteria [1] and possesses a series of characteristics of high crystallization, high strength, large specific surface, low density, biocompatibility, and biodegradability. Therefore, it is usually utilized in the field of construction, foodstuff, electronics, pharmacy, barrier industry, et al. [26].

The main methods for preparing CNC at present are the mechanical process, the chemical process of hydrolysis, the biological process of hydrolysis, and the combined method of the above processes. All the above methods mentioned have their own advantages and disadvantages and also different effects on their applications [7, 8]. This paper presents a summary of the research progress of preparations, modifications, and applications of CNC in all aspects.

2. Methods for CNC Preparations

The plant fibers are usually employed in preparing the CNC for its low price and abundance, whose common size is 0.5~3.0 mm for length and 20~40 μm for diameter [9]. Meanwhile, the size of any one dimensionality of cellulose locating in 100 nm is called the CNC [10]. Therefore, the methods for obtaining the CNC are the processes of decreasing the size of natural cellulose, which includes the process of mechanical, the chemical hydrolysis, the biological hydrolysis, and the combined methods.

2.1. Preparation of CNC via the Mechanical Process

The mechanical process is a physical method for getting the CNC and consists of four ways: homogenization under high pressure, microfluidization, fine grinding, and freezing smashing [11].

2.1.1. Homogenization under High Pressure

Homogenization is a one-step process to make a stable suspension by smashing the solid to form ultrafine particles in the solution [12]. Homogenization under high pressure was usually used to produce the microcrystalline cellulose (MCC), where the process of the homogenization under high pressure usually occurred in the homogeneous valve [13]. The raw material was extruded to the adjustable gap between the rod and the seat of the valve (usually ) by the outside force to accelerate the solution speed to 200~300 m/s. While leaving the gap, the inner press of the mixed solution fell instantaneously [14]. According to Bernoulli’s theory [15], the great change of inner press would create an inner shearing force to produce lots of positive holes and the turbulence, which would break the fibers into ultrafine particles.

The method of homogenization under high pressure was first improved in 1980s [16]. Turbak et al. [17] employed the wood fibers to produce the MCC with this method and obtained the stable MCC gel with high viscosity. And then, a series of studies reported its application for the MCC preparation with varieties of raw materials. Khiari [18] utilized chemistry-treated residue of the Badam to produce cellulose nanofibril (CNF) gel at 600 bars for 10 times, and the resulting CNF was one with a diameter of 3~18 nm. Meanwhile, they also indicated that the parameters of production would be the best by holding the reaction temperature at 70~80°C, and the homogenization under high pressure could be applied in the continuous industry production.

Although the method of the homogenization under high pressure possessed several advantages, its development was also limited by its obvious disadvantages. As an energy-intensive process, the homogenization under high pressure utilizes lots of energy, which meant that its energy waste was huge. Meanwhile, its efficiency was unstable because the valve was easily jammed by the long plant fibers. All the above problems prevented its improvement.

2.1.2. Microfluidization

The microfluidization is called microfluidization under high pressure [19], one of the methods for preparing nanomaterials, and its technological process is shown in Figure 1 [20]. The raw slurry was firstly injected and pressurized to about 4000 bars by the fluid pump. It was then forced into a Y-form interactive vessel, where two squirts of liquid with the speed of 1000 m/s met head-on. This impaction would create a huge shear force as well as the void effect, which results in the manufacture of the nanoparticle. Furthermore, the slurry goes through the assistant vessel with several inner zigzags, which results in more impaction occurring with the cavity walls and consequently smashing the nanoparticles further to obtain more homogeneous CNC.

Li and Liu [21] employed the high-pressure jet machine to prepare the NFC at 103.4 MPa for 12 times with a diameter of 80 μm of its inner cavity. They indicated that the jet machine with small-bores in its main cavity could improve the relative water content of the prepared MCC. The test result showed that the relative water content of MCC was 1105% prepared by the machine with a diameter of 75 nm of its inner cavity for 10 times. Meanwhile, the MCC size decreased with the homogeneous times increasing and reached 100~200 nm after 5-time microfluidization, when the diameter of the main cavity was 100 nm. Compared to the homogenization under high pressure, the microfluidization had the disadvantage that the cavity was easily jammed by long fibers, and its energy consumption was high. It is not easily applicable in the industry.

2.1.3. Fine Grinding

The method of fine grinding was a novel physical way in preparing the MCC, which was realized by the fine grinder and a commercial grinder as shown in Figure 2. It was obvious that the core components consisted of two discs, the inner and the external, where both discs were covered with grooves with different parameters. The initial step of the process for the MCC preparation was firstly to pour the raw slurry into the gap between two discs, while the external disc remained stationary and the inner disc kept rotating. The relative rotation of the two discs produced the force of crush, shearing, friction, grinding, and tearing to divide the fibers as well as decrease their sizes to obtain the MCC. By controlling the grinding parameters, the MCC with varieties of size levels ended up with low energy consumption; meanwhile, the grinder was easy to clean and maintain. But it was incredibly inefficient, and little application was reported. Li and Liu [21] used the pretreated fibers of the coniferous tree to prepare the MCC by grinding the slurry for 15 times, and the diameter of the obtained MCC was 10~40 nm.

2.1.4. Freezing Smashing

The freezing smashing technique was used in smashing the frozen cellulose fiber with mechanical force to divide the cellulose fibers and produce the CNC. Liquid nitrogen was usually employed as the freezing medium to freeze the cellulose slurry, which could transfer the fibers from toughness to brittleness under low temperature and subsequently increase its internal stress. The powerful impaction from the mechanical smashing easily broke the structure of the frozen fibers hence dividing it to nanosize [22]. However, its cost was too high while it was also too low to be promoted.

2.2. Preparation of Chemical Process

Although all the above mechanical processes were employed in preparing the CNC, they were not widely applied due to their great energy consumption. Therefore, the chemical process was focused on treating the natural cellulose. As a kind of polysaccharide, the cellulose is made from the glucose molecules, which are connected by the β-1,4-glucosidic bond with each other [23]. Thus, the process of partially breaking glucosidic bonds is the key way to obtaining the CNC, and the chemical hydrolysis offers a case for realizing it [24].

2.2.1. Process of Alkali Hydrolysis

As a kind of natural polymer, the cellulose had the supramolecular structure which made it difficult to be hydrolyzed. However, the alkali had the ability to swell the cellulose as well as break its inner hydrogen bonds [25]. Therefore, the alkali was employed to hydrolyze the cellulose.

Research showed that the crystal form of natural cellulose was transferred from I-form to II-form after treatment with 9 wt% NaOH [26]. Zhang et al. [27] obtained the II-form spherical CNC by treating the cellulose with 5 M NaOH at 80°C and acid solution, successively. Tang et al. [28] used NaClO solution to hydrolyze the microcrystalline cellulose (MCC) to obtain spherical CNC with the diameter of 20~40 nm, and its crystalline was 79.71%. Hagman et al. [29] dissolved the MCC with 2 M NaOH solution and found that the MCC was hydrolyzed to new chains with a lower crystalline degree and kept stable in the solution. Xie et al. [30] investigated the effects of the parameters of the alkali hydrolysis on the microstructure of the CNC. They showed that the productivity of II-form CNC was 54.50% with an average diameter of 156.9 nm, and its parameter was handling the cellulose with 5 M NaOH solution at 60°C for 2 hours. Although several studies have reported the application of alkali in hydrolyzing cellulose, the alkali was mainly employed in pretreating the cellulose to dissolve the lignin and pectin.

2.2.2. Process of Acid Hydrolysis

The microstructure of the cellulose fiber consisted of discontinuous regions of crystalline cellulose and amorphous cellulose, where the unconfined amorphous region was between two inerratic crystalline regions, and the fiber was made from the repetition of the above structures. Therefore, researches were aimed at how to remove the amorphous regions quickly and keeping the crystalline regions as well.

Liu et al. [31] prepared the CNC from reed pulp with 55 wt% sulfuric acid, using sodium m-nitrobenzene sulfonate (SMS) as the cocatalyst. It was indicated that the optimum parameters for the CNC preparation were the reaction at 50°C for 5 hours accompanied with 10 wt% SMS. Compared to the method with two catalysts, sodium dodecyl benzene sulfonate (SDBS) and cupric sulfate simultaneously, the CNC obtained from this process was smaller and more homogeneous, with much higher yield. Wu et al. [32] indicated that the ultrasound-assisted sulfuric acid method could be applied for the preparation of CNC, and its parameters were about 10 nm for diameter and 200~400 nm for length with a crystallinity of 63.3%. Meanwhile, the thermal insulation foam made of the CNC with the freezing-drying method expressed its perfect thermal insulation performance under normal condition.

You et al. [33] used the ultrasonic-assisted method to hydrolyze the MCC with carbon-based phosphotungstic acid as the catalyst. The obtained CNC was rod-like and I-form with a length of 146~862 nm and a diameter of 12~79 nm, whose crystallinity was 76.1%. Sun et al. [34] hydrolyzed the cotton fibers with 63.9% sulfur acid at 50°C and tested its microstructure, solubility in alkali solution, molecular weight, and other characteristics. It was found that the hydrolysis time of 45~55 min was the optimum time range when the CNC yield was 32.2~41.7%, and the 18% NaOH solution was a perfect indicator for the CNC preparation. The process of acid hydrolysis is widely applied all over the world, but the terrible wastes are unavoidable, wasted solution of acid, alkali, water, and residua. And the novel ways for obtaining the CNC have drawn the attentions all the time.

2.2.3. Process of TEMPO Hydrolysis

The TEMPO is a series of reagents used to oxidize the alcohol and ether, including 2,2,6,6-tetramethylepiperridin-1-oxyl and its ramifications with the structure of 1-oxyl, an oxygen radical. Research showed that the function of the TEMPO was its oxidation effect on the alcoholic hydroxyl group [9]. As an efficient and pollution-free reagent, the TEMPO was employed to produce the CNC, and its common reaction system consisted of the TEMPO, the NaBr, and the NaClO [35].

2.2.3.1. Development of TEMPO Reaction System. Research indicated that the process of the TEMPO oxidation of the cellulose was a process where the C6-formyl group was transformed to the C6-carboxyl group [36]. As the main oxidation reagent, the NaClO firstly transformed the NaBr into NaBrO, and the produced NaBrO would oxide the TEMPO to be a nitrosonium. Nitrosonium underwent oxidation to transform the alcoholic hydroxyl group and produced an aldehyde or carboxylic acid, where its mechanism was displayed in Figure 3 [37].

However, further study showed that the basicity of alkalinity had great effect on the degree of dissociation of the CNC, which might have led to the decrement of the mechanical properties of the CNC, as the strength and flexibility of the nanofibers [38]. Therefore, the present researches of the reaction systems were mainly focused on the adjustment and controlling of the reaction system [39].

Saito et al. [37] replaced the NaBr in the reaction system of the TEMPO/NaBr/NaClO with the NaClO2 and found the phenomena that the aldehyde groups teemed in the produced CNC surface obtained from the reaction system of the TEMPO/NaBr/NaClO, and it did not occur in the TEMPO/NaClO/NaClO2 system. This mechanism is shown in Figure 3. Meanwhile, the size of the CNC made from the above reaction system was long for 2 μm and wide for 5 nm; the degree of polymerization was 900, with an optimum reaction pH of 6.8.

Although the system of the TEMPO/NaClO/NaClO2 displayed its advantages, its disadvantages were also unavoidable, such as its terrible reaction rate and relatively low content of the carboxyl in the CNC. Attentions were drawn to improve the efficiency of the TEMPO/NaClO/NaClO2 system [40]. Iwamoto et al. [41] employed ten kinds of systems consisting of TEMPO ramification, NaBr, NaClO, and NaClO2 to compare their efficiencies in preparing the CNC. It resulted that the 4-acetamido-TEMPO and the 4-methoxy-TEMPO showed their optimum catalytic efficiencies; however, the 4-hydroxyl-TEMPO and 4-oxygen-TEMPO showed the worst efficiencies. In addition, the ultrasonic assistance was usually used in the chemical reaction. Mishra et al. [42] utilized the system of the TEMPO to hydrolyze the cellulose with the ultrasonic assistance, and the productivity of the CNC was raised by about 10%, when the content of the carboxyl was raised by 10~15%. According to the above investigations, it was obvious that the preparations with the system of TEMPO were a pollution-free and efficient way to produce the CNC, which also sketched the contours of its development prospect of the assistance-TEMPO methods.

2.2.3.2. Effect of Treatment on the Dispersion of the CNC. The preparation of the CNC was affected by a series of factors that involved the reaction conditions, the carboxyl content, the homogenization treatment, and other circumstances [4345], in which the carboxyl content of the CNC controlled the dispersity of the cellulose fiber in water as well as the productivity of the CNC [46].

Hirota et al. [47] indicated that the oxide cellulose fiber obtained with different methods possessed a similar carboxyl concentration of 1.8~2.2 mmol/g on the fiber, which was the maximum content in the undissolved cellulose fibers. On the other hand, low content of the carboxyl in the CNC was against its decentralization in the water. Saito et al. [48] found that the system’s viscosity increased quickly with 2~4% solid content; however, the phenomena did not occur while the content was below 1%. In addition, research showed that the CNC solution possessed much more carboxyls and displayed relatively lower viscosity, because of the electrostatic repulsive force among the carboxyls [49, 50]. Okita et al. [43] reported that the TEMPO-CNC dissolved not only in water but also in several organic solvents, and the CNC could also be obtained in the organic solvent just with extremely high energy consumption. The morphology of CNC obtained by four methods is shown in Figure 4 [51].

2.3. Preparation of Biological Fermentation

Usually, the process of chemical hydrolysis is low-cost and convenient for preparing the CNC, but its pollution is terrible since it leaves lots of wasted solutions of acid or alkali, which is difficult to handle and harmful to the environment. Therefore, the noncomplicated, efficient, and pollution-free method for preparing the CNC is focused on in recent years. As a perfect solution, the biological process rises in response to the proper time and conditions, which mainly involves the biological hydrolysis.

The CNC was firstly obtained from some specific bacterial cellulose (BC) in 1886 [52], which was so called bacterial nanocellulose (BNC). Several bacteria were discovered and employed in obtaining the BNC, including the Acetobacter, Azotobacter, Achromobacter, and Aerobacter [53]. In fact, the BC was better than plant cellulose in terms of its higher purity, crystallinity (over 60%), degree of polymerization (between 2000 and 6000), and tensile strength [54, 55]. Therefore, the BC was a perfect resource for the BNC.

Usually, the BNC was extruded through the bacterium cell pores in the form of ribbons. These ribbons started at specific points on the cell surface and became thicker as they built a composite ribbon. Finally, the cellulose nanofibers were with a 2~4 nm diameter and several 100 μm length [51, 56]. However, each bacterium BNC had its own merits according to the difference in the bacterium type as well as its cultured conditions. For instance, the Acetobacter BNC was with an α-crystalline structure and its fiber showed a rectangular section with a parameter in . A list of CNC with different characterizations is shown in Table 1 [57].


TypeLength (μm)Width (nm)Height (nm)Cross-sectionCrystallinitya (%)Iβ (%)

Acetobacter>130-506-10Rectangular633-27
Acetobacterb>16-106-10Square53
Cellulose IIFilamentCylindrical27-43

Although the characterizations of the component ratio of amorphous and crystalline regions and size of the microcellulose are according to the kinds of bacteria, the ways of dividing them from each other by removing the amorphous zones are common, and the cellulase acts as a pair of scissors to do it. Usually, the scissors consisted of several cellulases, 1,4-β-D-glucan glucanohydrolase, 1,4-β-D-glucan cellobiohydrolase, β-1,4-glucosidase, etc. [58]. Because of the heterogeneous catalytic reaction of the cellulase, no cellulase possessed the ability to efficiently catalyze the BC hydrolysis individually, and the biological process was always focused on increasing the hydrolyzed efficiency with the combined actions of kinds of cellulases.

BNCs obtained by catalyzing the pulp with Trichoderma viride G were with great globular characterizations (2.5~10 nm) with optimum conditions of pH 4.8 and temperature of 45°C for 2 h [59]. It was indicated that the BNC produced by Acetobacter xylinum was with a great thermostability (≤330°C) and swelling resistance, while the producing efficiency raised by controlling the fermentation temperature and rotation speeds [60]. On the other hand, researches on the BNC production by sugar derivatives were also focused on long ago, with results showing that the productivity obtained from arabitol and mannitol was 6.2 and 3.8 times, respectively, more than that from the glucose [61]. The MCC obtained from the Cladophora showed an average length of 350 nm with a degree of polymerization of 690 for β-glucan chain [59]. More and more attentions were drawn for its economic efficiency and irreplaceable sustainability.

2.4. Preparation via the Combined Method

In general, all the above solutions could be applied for CNC preparation, but there exists lots of problems that limit the development of those technologies, such as the energy-extensive consumption of the mechanical process, the heavy pollution of the chemical process, and the underactivity of the biological process on raw plant fibers. Therefore, the combination of several methods is an irresistible trend of the CNC preparation. And the normal combinations are between the process of machinery and chemistry or biology.

By combining chemical pretreatment and mechanical methods, Alemdar and Sain obtained the MFC with a 10~80 nm in diameter and several microns in length [62]. Meanwhile, the MFC from the preoxidized pulp were with average diameters of 5.51 nm by rotation and 4.7 nm by ultrasound [63].

3. Applications of CNC

Owing to lots of perfect properties of strength, light transmission, gas barrier, et al., the applications of the CNC were focused on the optical film, electronics, composite materials, and other fields [6468].

3.1. CNC Reinforcement Composites

As a prepossessing field, the development of nanocomposites was drawing more and more attentions since the properties of CNC included high strength, low density, great biodegradation, green renewability, crystallinity, porosity, and interphase effects [69].

As a nanofiber from the natural resources, the CNC possessed a mean strength within the ranges of 1.6~3 GPa, which was comparable with those of commercially available multiwalled carbon nanotubes [70]. Therefore, it was available for the reinforcement of the composites with CNC.

It was shown that the CNC-reinforced Polyvinyl Alcohol (PVA) fibrils possessed a tensile modulus of 57 GPa far greater than those of PVA fibrils as well as its storage modulus [71], which was because of uniform dispersion of CNC in the PVA and their hydrogen bonding. Another research employed the use of CNC to modify polyethylene oxide (PEO) and showed that and of the 20%-CNC/PEO composites improved 2 and 2.5 times comparing to the pure PEO, respectively, [72].

Li et al. [73] obtained the nanocomposites by combining the CNC with the polymerization of phenol, and their thermal stability was much better than the polyphenols. Wang et al. [74] prepared a CNC/soy protein thermoplastics and found that and of the composite changed from 0.53 to 1.02 GPa and from 16.7 to 31.2 MPa, respectively, by adding 20% CNC. However, it changed from 0.60 to 1.82 GPa and from 20.2 to 59.3 MPa, respectively, with 30% CNC [75].

3.2. Barrier Films

Because of its waterproof and barrier functions, the CNC-modified composites have attracted interest in the applications of barrier films with potential utilizations in filtration and packaging [76]. The investigations were mainly focused on how to prevent water vapor and oxygen from permeation into the envelope.

It was shown that the water vapor permeability decreased with the CNC addition in the envelope. Choi and Simonsen [77] indicated that the CNC composite film possessed great water vapor preventions with a permeability decrease to 11% in thermal treatments. Chinga-Carrasco and Syverud [78] proved that the oxygen permeating speed was 3.0 cm3·(m2·24h·0.1 MPa)-1 with a 50% relative humidity level by testing the CNC film. The great barrier property was proven by Fukuzumi et al. [79] that the average pore size of CNC film was about 0.47 nm close to the kinetic diameter of oxygen, and this structure would prevent oxygen from approaching into the envelope.

Meanwhile, applications of CNC in the oxygen permeability of composite film were also investigated. Petersson and Oksman [80] found that the oxygen permeability of the polylactic acid (PLA) was increased by over 3 times compared to pure PLA with 5 wt% MCC addition. In contrast, other researches showed that the oxygen permeability of CNC/PLA film was significantly lowered to 1 mL·m-2·day-1·Pa-1 with a film structure of a 0.4 mm TEMPO-NFC film on top of a 25 mm thick PLA film (746 mL·m-2·day-1·Pa-1) [81]. It was interesting that the properties went in the opposite directions with different film structures. Because the barrier properties of envelopes were connected to factors that influence the tortuous path of the diffusion species though the film, the difference between the two studies mentioned above might be affected by several factors, such as orientation, concentration, reinforcement shape, crystallinity, porosity, and interphase effects.

Similarly, it was demonstrated that neat CNC films possessed a relatively low oxygen permeability of 17 mL·m-2·day-1 with a thickness of 20~30 mm [82]. However, it was below 10~20 mL·m-2·day-1 of the oxygen transmission rate of the atmosphere packaging with this CNC modification [83]. This property demonstrated the potential of neat and/or modified CNC films for oxygen barrier applications.

3.3. Biomaterials

CNC has been widely used in biomedical scaffolds, strain sensor, oil/water separation, drug excipient, wound dressings, and other biological materials for its biodegradability, high biocompatibility, and nontoxicity [84, 85].

Zhang et al. [86] developed an optical probe for the selective and quantitative detection of Cu2+ using surface-modified fluorescent CNC. The external surface of fluorescent CNC was modified by the mild EDTAD esterification and amidation with 7-amino-4-methylcumarin, which caused the topological distribution of fluorescent moieties and other functional groups. It is possible that the fluorescent CNC can be widely used for bioimaging and metal ion detection in the coming years. Recently, the CNC-based composite using 3D printing technology has attracted extensive attention in the medical field. Sultan and Mathew [87] prepared porous and 3D printable scaffolds from the hydrogel ink of sodium alginate and gelatin reinforced with CNC. CNC provided nice structural orientation, rheological properties, and mechanical properties during the 3D printing process. The biobased scaffolds with pore size from 80 to 2125 μm and nanoscale pore wall roughness were considered suitable for cell interactions and guided cell growth during tissue regeneration. Though many researches about biocompatibility, long-term toxicology, and security between CNC-based composite and human bodies remain in the exploration stage, lots of results indicate a promising future.

3.4. Other Applications

As a promising material for energy application, the flexible energy storage device was made by using the MWNT nanowire arrays of CNC [88]. The typical structure was based on a single sheet of conductive cellulose paper (separator) made from room temperature ionic liquid and CNC (electrode). Zhu et al. [89] proved that the CNC nanopapers could be applied as the matrix for light-emitting diode (LED) and also found that LED with CNC matrix are highly transparent in the visible and near-infrared wavelength regions. Meanwhile, the CNC matrix was all flexible enough to be compatible with roll-to-roll processing.

Niu et al. [90] employed the CNC for preparation of the multilayer membrane electrode for the supercapacitor. It indicated that the prepared composite film exhibited great flexibility and elastic resilience for the application prospect. Gao et al. [91] manufactured a conductive paper with a self-assembly of the CNC and reduced graphene oxide (RGO). It indicated that the composite paper possessed an excellent mechanical property, and its transmittance and sheet surface resistance could be designed by controlling the number of layer-by-layer (LbL) assembly. For example, the paper with a 20 LbL shows a sheet resistance of ∼2.5 kΩ and a transmittance of 76% (at 550 nm). It revealed a greater prospect in the field of information-transfer than conventional paper.

4. Conclusions

The preparation methods and applications of the CNC were summarized in this paper, and the scarcity of resources urged us to find some renewable resources to effectively contrast this phenomenon. CNC in the form of microfiber or nanofiber had unique properties including high elastic modulus, dimensional stability, outstanding reinforcement potential, and transparency. As a natural resource, efficient obtainment and smart application were still drawing the attentions on environmentally friendly utilization all the time. Since CNC research is still at its booming stage, industrial commercialization has not been arrived at yet. There exists a huge market of CNC, and indications show that the world market of CNC would be 60 billion dollars in 2020. Therefore, a great prospect is displayed for its development. With proof-based investigations, there would be a real improvement in this field to reply all circumstances.

Conflicts of Interest

The authors declare that there is no conflict of interest regarding the publication of this paper.

Acknowledgments

This work is supported by the National Natural Science Foundation of China (Grant Nos. 51705113 and 51804169), the Natural Science Foundation of Jiangsu Province (Grant Nos. BK20191192 and BK20180715), and the Foundation of Science and Technology on Reactor Fuel and Materials Laboratory (No. 6142A0604031709).

References

  1. Y. Qing, R. Sabo, J. Y. Zhu, U. Agarwal, Z. Cai, and Y. Wu, “A comparative study of cellulose nanofibrils disintegrated via multiple processing approaches,” Carbohydrate Polymers, vol. 97, no. 1, pp. 226–234, 2013. View at: Publisher Site | Google Scholar
  2. J. Han, K. Lu, Y. Yue et al., “Nanocellulose-templated assembly of polyaniline in natural rubber-based hybrid elastomers toward flexible electronic conductors,” Industrial Crops and Products, vol. 128, pp. 94–107, 2019. View at: Publisher Site | Google Scholar
  3. Q. Ding, X. Xu, Y. Yue et al., “Nanocellulose-mediated electroconductive self-healing hydrogels with high strength, plasticity, viscoelasticity, stretchability, and biocompatibility toward multifunctional applications,” ACS Applied Materials & Interfaces, vol. 10, no. 33, pp. 27987–28002, 2018. View at: Publisher Site | Google Scholar
  4. S. Zhou, G. Zhou, S. Jiang, P. Fan, and H. Hou, “Flexible and refractory tantalum carbide-carbon electrospun nanofibers with high modulus and electric conductivity,” Materials Letters, vol. 200, pp. 97–100, 2017. View at: Publisher Site | Google Scholar
  5. S. Gao, G. Tang, D. Hua et al., “Stimuli-responsive bio-based polymeric systems and their applications,” Journal of Materials Chemistry B, vol. 7, no. 5, pp. 709–729, 2019. View at: Publisher Site | Google Scholar
  6. J. Sun, Y. Zhao, Z. Yang et al., “Highly stretchable and ultrathin nanopaper composites for epidermal strain sensors,” Nanotechnology, vol. 29, no. 35, p. 355304, 2018. View at: Publisher Site | Google Scholar
  7. X. Cao, B. Ding, J. Yu, and S. S. al-Deyab, “Cellulose nanowhiskers extracted from TEMPO-oxidized jute fibers,” Carbohydrate Polymers, vol. 90, no. 2, pp. 1075–1080, 2012. View at: Publisher Site | Google Scholar
  8. Q. Wu, X. Li, S. Fu, Q. Li, and S. Wang, “Estimation of aspect ratio of cellulose nanocrystals by viscosity measurement: influence of surface charge density and NaCl concentration,” Cellulose, vol. 24, no. 8, pp. 3255–3264, 2017. View at: Publisher Site | Google Scholar
  9. T. Saito and A. Isogai, “Tempo-mediated oxidation of native cellulose. The effect of oxidation conditions on chemical and crystal structures of the water-insoluble fractions,” Biomacromolecules, vol. 5, no. 5, pp. 1983–1989, 2004. View at: Publisher Site | Google Scholar
  10. G. Chinga-Carrasco, Y. Yu, and O. Diserud, “Quantitative electron microscopy of cellulose nanofibril structures fromEucalyptusandPinus radiataKraft pulp fibers,” Microscopy and Microanalysis, vol. 17, no. 4, pp. 563–571, 2011. View at: Publisher Site | Google Scholar
  11. L. Geng, B. Chen, X. Peng, and T. Kuang, “Strength and modulus improvement of wet-spun cellulose I filaments by sequential physical and chemical cross-linking,” Materials & Design, vol. 136, pp. 45–53, 2017. View at: Publisher Site | Google Scholar
  12. J. Han, Y. Yue, Q. Wu et al., “Effects of nanocellulose on the structure and properties of poly(vinyl alcohol)-borax hybrid foams,” Cellulose, vol. 24, no. 10, pp. 4433–4448, 2017. View at: Publisher Site | Google Scholar
  13. Z. Zhang, “The theoretical analysis and discussion of high pressure homogenizing,” Packaging and Food Machinery, vol. 1, 2001. View at: Google Scholar
  14. H. U. Yun and J. G. Liu, “Overview on preparation and research projects of nanocellulose,” China Pulp & Paper Industry, vol. 6, pp. 33–36, 2013. View at: Google Scholar
  15. S. Armstrong and P. Dario, “Elliptic regularity and quantitative homogenization on percolation clusters,” Communications on Pure and Applied Mathematics, vol. 71, no. 9, pp. 1717–1849, 2018. View at: Publisher Site | Google Scholar
  16. F. W. Herrick, R. L. Casebier, J. K. Hamilton, and K. R. Sandberg, “Microfibrillated cellulose: morphology and accessibility,” in Journal of Applied Polymer Science: Applied Polymer Symposium, vol. 37, pp. 797–813, ITT Rayonier Inc., Shelton, WA, 1983. View at: Google Scholar
  17. A. F. Turbak, F. W. Snyder, and K. R. Sandberg, “Microfibrillated cellulose, a new cellulose product: properties, uses, and commercial potential,” in Journal of Applied Polymer Science: Applied Polymer Symposium, vol. 37, pp. 815–827, ITT Rayonier Inc., Shelton, WA, USA, 1983. View at: Google Scholar
  18. R. Khiari, “Valorization of agricultural residues for cellulose nanofibrils production and their use in nanocomposite manufacturing,” International Journal of Polymer Science, vol. 2017, 10 pages, 2017. View at: Publisher Site | Google Scholar
  19. F. Villalobos-Castillejos, V. G. Granillo-Guerrero, D. E. Leyva-Daniel et al., “Fabrication of nanoemulsions by microfluidization,” in Nanoemulsions, pp. 207–232, Elsevier, 2018. View at: Publisher Site | Google Scholar
  20. S. Song, J. Guo, X. Chen et al., “Progress in application of high pressure microfluidization in preparation of nanomedicines,” Chinese Journal of New Drugs, vol. 22, pp. 2388–2391, 2013. View at: Google Scholar
  21. J. LI and Z.-m. LIU, “Preparation and Hydrophobic Modification of Phyllostachys heterocycla cv. Pubescens NFC/SiO_2 Aerogel,” Journal of Cellulose Science and Technology, vol. 1, p. 8, 2016. View at: Google Scholar
  22. J. Ma, F. Yu, and J. N. Wang, “Preparation of water-dispersible single-walled carbon nanotubes by freeze-smashing and application as a catalyst support for fuel cells,” Journal of Materials Chemistry, vol. 20, no. 27, pp. 5742–5747, 2010. View at: Publisher Site | Google Scholar
  23. O. Shoseyov, A. Heyman, S. Lapidot, S. Meirovitch, Y. Nevo, and A. Rivkin, Method for production of cellulose nano crystals from cellulose-containing waste materials, Yissum Research Development Company Of The Hebrew University Of Jerusalem Ltd., 2012.
  24. K. Löbmann and A. J. Svagan, “Cellulose nanofibers as excipient for the delivery of poorly soluble drugs,” International Journal of Pharmaceutics, vol. 533, no. 1, pp. 285–297, 2017. View at: Publisher Site | Google Scholar
  25. D. Hua, Z. Liu, F. Wang et al., “pH responsive polyurethane (core) and cellulose acetate phthalate (shell) electrospun fibers for intravaginal drug delivery,” Carbohydrate Polymers, vol. 151, pp. 1240–1244, 2016. View at: Publisher Site | Google Scholar
  26. J. Wu, X. Li, J. Ye, L. Zhu, Y. Dou, and J. Hong, “The effects of alkali pretreatment on the properties of cellulose from hempen pulp,” Journal of Nanjing Forestry University, vol. 34, no. 5, pp. 96–100, 2010. View at: Google Scholar
  27. J. Zhang, T. J. Elder, Y. Pu, and A. J. Ragauskas, “Facile synthesis of spherical cellulose nanoparticles,” Carbohydrate Polymers, vol. 69, no. 3, pp. 607–611, 2007. View at: Publisher Site | Google Scholar
  28. L. R. Tang, B. Huang, D. S. Dai, W. Ou, and X. R. Chen, “Preparation and spectrum properties of cellulose nanoparticles,” Guang pu xue yu guang pu fen xi = Guang pu, vol. 30, no. 7, pp. 1876–1879, 2010. View at: Google Scholar
  29. J. Hagman, L. Gentile, C. M. Jessen, M. Behrens, K. E. Bergqvist, and U. Olsson, “On the dissolution state of cellulose in cold alkali solutions,” Cellulose, vol. 24, no. 5, pp. 2003–2015, 2017. View at: Publisher Site | Google Scholar
  30. C. Xie, Z. M. Liu, W. U. Peng, G. Z. Fang, and X. Zhao, “Optimization of preparation technology of alkali pretreated reed pulp nano-cellulose,” Chemistry & Industry of Forest Products, vol. 33, pp. 32–36, 2013. View at: Google Scholar
  31. Z. M. Liu, C. Xie, W. U. Peng, and L. Y. Liu, “Preparation of reed pulp nanocrystalline cellulose by sulfuric acid hydrolysis with sodium m-nitrobenzene sulfonate as cocatalyst,” Biomass Chemical Engineering, vol. 5, pp. 1–6, 2012. View at: Google Scholar
  32. Q. Wu, S. Chen, and Y. Chen, “Preparation and characterization of nanocellulose crystals from Luffa sponge,” Journal of Northwest A & F University-Natural Science Edition, vol. 42, pp. 229–234, 2014. View at: Google Scholar
  33. H. You, C. Zeng, Q. Lu, L. Tang, G. Wu, and B. Huang, “Preparation and characterization of nanocrystalline cellulose catalyzed by carbon-based phosphotungstic acid,” Journal of Southwest Forestry University, vol. 34, pp. 100–103, 2014. View at: Google Scholar
  34. B. Sun, M. Zhang, Q. Hou, R. Liu, T. Wu, and C. Si, “Further characterization of cellulose nanocrystal (CNC) preparation from sulfuric acid hydrolysis of cotton fibers,” Cellulose, vol. 23, no. 1, pp. 439–450, 2016. View at: Publisher Site | Google Scholar
  35. T. Saito, I. Shibata, A. Isogai, N. Suguri, and N. Sumikawa, “Distribution of carboxylate groups introduced into cotton linters by the TEMPO-mediated oxidation,” Carbohydrate Polymers, vol. 61, no. 4, pp. 414–419, 2005. View at: Publisher Site | Google Scholar
  36. T. Saito and A. Isogai, “Introduction of aldehyde groups on surfaces of native cellulose fibers by TEMPO-mediated oxidation,” Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 289, no. 1-3, pp. 219–225, 2006. View at: Publisher Site | Google Scholar
  37. T. Saito, M. Hirota, N. Tamura et al., “Individualization of nano-sized plant cellulose fibrils by direct surface carboxylation using TEMPO catalyst under neutral conditions,” Biomacromolecules, vol. 10, no. 7, pp. 1992–1996, 2009. View at: Publisher Site | Google Scholar
  38. A. E. J. de Nooy, A. C. Besemer, H. van Bekkum, J. A. P. P. van Dijk, and J. A. M. Smit, “Tempo-mediated oxidation of pullulan and influence of ionic strength and linear charge density on the dimensions of the obtained polyelectrolyte chains,” Macromolecules, vol. 29, no. 20, pp. 6541–6547, 1996. View at: Publisher Site | Google Scholar
  39. I. Shibata and A. Isogai, “Depolymerization of cellouronic acid during TEMPO-mediated oxidation,” Cellulose, vol. 10, no. 2, pp. 151–158, 2003. View at: Publisher Site | Google Scholar
  40. T. Saito, M. Hirota, N. Tamura, and A. Isogai, “Oxidation of bleached wood pulp by TEMPO/NaClO/NaClO2 system: effect of the oxidation conditions on carboxylate content and degree of polymerization,” Journal of Wood Science, vol. 56, no. 3, pp. 227–232, 2010. View at: Publisher Site | Google Scholar
  41. S. Iwamoto, W. Kai, T. Isogai, T. Saito, A. Isogai, and T. Iwata, “Comparison study of tempo-analogous compounds on oxidation efficiency of wood cellulose for preparation of cellulose nanofibrils,” Polymer Degradation and Stability, vol. 95, no. 8, pp. 1394–1398, 2010. View at: Publisher Site | Google Scholar
  42. S. P. Mishra, J. Thirree, A. S. Manent, B. Chabot, and C. Daneault, “Ultrasound-catalyzed TEMPO-mediated oxidation of native cellulose for the production of nanocellulose: effect of process variables,” BioResources, vol. 6, no. 1, pp. 121–143, 2011. View at: Google Scholar
  43. Y. Okita, S. Fujisawa, T. Saito, and A. Isogai, “TEMPO-oxidized cellulose nanofibrils dispersed in organic solvents,” Biomacromolecules, vol. 12, no. 2, pp. 518–522, 2011. View at: Publisher Site | Google Scholar
  44. W. Ma, Z. Guo, J. Zhao et al., “Polyimide/cellulose acetate core/shell electrospun fibrous membranes for oil- water separation,” Separation and Purification Technology, vol. 177, pp. 71–85, 2017. View at: Publisher Site | Google Scholar
  45. A. A. Moud, M. Arjmand, J. Liu, Y. Yang, A. Sanati-Nezhad, and S. H. Hejazi, “Cellulose nanocrystal structure in the presence of salts,” Cellulose, 2019. View at: Publisher Site | Google Scholar
  46. A. Rattaz, S. P. Mishra, B. Chabot, and C. Daneault, “Cellulose nanofibres by sonocatalysed-TEMPO-oxidation,” Cellulose, vol. 18, no. 3, pp. 585–593, 2011. View at: Publisher Site | Google Scholar
  47. M. Hirota, N. Tamura, T. Saito, and A. Isogai, “Cellulose II nanoelements prepared from fully mercerized, partially mercerized and regenerated celluloses by 4-acetamido-TEMPO/NaClO/NaClO2 oxidation,” Cellulose, vol. 19, no. 2, pp. 435–442, 2012. View at: Publisher Site | Google Scholar
  48. T. Saito, Y. Nishiyama, J.-L. Putaux, M. Vignon, and A. Isogai, “Homogeneous suspensions of individualized microfibrils from TEMPO-catalyzed oxidation of native cellulose,” Biomacromolecules, vol. 7, no. 6, pp. 1687–1691, 2006. View at: Publisher Site | Google Scholar
  49. I. Besbes, S. Alila, and S. Boufi, “Nanofibrillated cellulose from TEMPO-oxidized eucalyptus fibres: effect of the carboxyl content,” Carbohydrate Polymers, vol. 84, no. 3, pp. 975–983, 2011. View at: Publisher Site | Google Scholar
  50. A. Huang, X. Peng, L. Geng et al., “Electrospun poly (butylene succinate)/cellulose nanocrystals bio-nanocomposite scaffolds for tissue engineering: Preparation, characterization and _invitro evaluation,” Polymer Testing, vol. 71, pp. 101–109, 2018. View at: Publisher Site | Google Scholar
  51. Y. Habibi, “Key advances in the chemical modification of nanocelluloses,” Chemical Society Reviews, vol. 43, no. 5, pp. 1519–1542, 2014. View at: Publisher Site | Google Scholar
  52. A. J. Brown, “XLIII.—On an acetic ferment which forms cellulose,” Journal of the Chemical Society, Transactions, vol. 49, no. 0, pp. 432–439, 1886. View at: Publisher Site | Google Scholar
  53. Z. Shi, G. O. Phillips, and G. Yang, “Nanocellulose electroconductive composites,” Nanoscale, vol. 5, no. 8, pp. 3194–3201, 2013. View at: Publisher Site | Google Scholar
  54. S. Bae, Y. Sugano, and M. Shoda, “Improvement of bacterial cellulose production by addition of agar in a jar fermentor,” Journal of Bioscience and Bioengineering, vol. 97, no. 1, pp. 33–38, 2004. View at: Publisher Site | Google Scholar
  55. S. Bae and M. Shoda, “Statistical optimization of culture conditions for bacterial cellulose production using Box-Behnken design,” Biotechnology and Bioengineering, vol. 90, no. 1, pp. 20–28, 2005. View at: Publisher Site | Google Scholar
  56. C. J. Grande, F. G. Torres, C. M. Gomez, O. P. Troncoso, J. Canet-Ferrer, and J. Martínez-Pastor, “Development of self-assembled bacterial cellulose-starch nanocomposites,” Materials Science and Engineering: C, vol. 29, no. 4, pp. 1098–1104, 2009. View at: Publisher Site | Google Scholar
  57. R. J. Moon, A. Martini, J. Nairn, J. Simonsen, and J. Youngblood, “Cellulose nanomaterials review: structure, properties and nanocomposites,” Chemical Society Reviews, vol. 40, no. 7, pp. 3941–3994, 2011. View at: Publisher Site | Google Scholar
  58. B. Kunasundari, S. Naresh, and N. Z. C. Zakaria, “Isolation and characterization of cellulase producing bacteria from tropical mangrove soil,” in Proceedings of the 2017 International Conference on Biomedical Engineering and Bioinformatics, pp. 34–37, Bangkok, Thailand, September 14 - 16, 2017. View at: Publisher Site | Google Scholar
  59. K. K. Kar, S. Rana, and J. Pandey, Handbook of Polymer Nanocomposites Processing, Performance and Application, Springer, Berlin/Heidelberg, Germany, 2015.
  60. M. F. A. K. Tua, “Effects of agitation conditions on bacterial cellulose production by Acetobacter xylinum 0416 in fermentation of matured coconut water medium,” Malaysian Journal of Analytical Sciences, vol. 21, pp. 261–266, 2017. View at: Google Scholar
  61. R. Jonas and L. F. Farah, “Production and application of microbial cellulose,” Polymer Degradation and Stability, vol. 59, no. 1-3, pp. 101–106, 1998. View at: Publisher Site | Google Scholar
  62. A. Alemdar and M. Sain, “Isolation and characterization of nanofibers from agricultural residues - Wheat straw and soy hulls,” Bioresource Technology, vol. 99, no. 6, pp. 1664–1671, 2008. View at: Publisher Site | Google Scholar
  63. S. P. Mishra, A.-S. Manent, B. Chabot, and C. Daneault, “Production of nanocellulose from native cellulose–various options utilizing ultrasound,” BioResources, vol. 7, no. 1, pp. 0422–0436, 2011. View at: Google Scholar
  64. Q. Zhu, Y. Jin, G. Sun, K. Yan, and D. Wang, “AQC functionalized CNCs/PVA-co-PE composite nanofibrous membrane with flower-like microstructures for photo-induced multi-functional protective clothing,” Cellulose, vol. 25, no. 8, pp. 4819–4830, 2018. View at: Publisher Site | Google Scholar
  65. P. Daraei, N. Ghaemi, and H. Sadeghi Ghari, “An ultra-antifouling polyethersulfone membrane embedded with cellulose nanocrystals for improved dye and salt removal from water,” Cellulose, vol. 24, no. 2, pp. 915–929, 2017. View at: Publisher Site | Google Scholar
  66. H.-Y. Mi, X. Jing, J. Peng, M. R. Salick, X.-F. Peng, and L.-S. Turng, “Poly(ε-caprolactone) (PCL)/cellulose nano-crystal (CNC) nanocomposites and foams,” Cellulose, vol. 21, no. 4, pp. 2727–2741, 2014. View at: Publisher Site | Google Scholar
  67. J. Sun, J. Zhuang, J. Shi et al., “Highly elastic and ultrathin nanopaper-based nanocomposites with superior electric and thermal characteristics,” Journal of Materials Science, vol. 54, no. 11, pp. 8436–8449, 2019. View at: Publisher Site | Google Scholar
  68. J. Sun, H. Li, Y. Huang et al., “Simple and affordable way to achieve polymeric superhydrophobic surfaces with biomimetic hierarchical roughness,” ACS Omega, vol. 4, no. 2, pp. 2750–2757, 2019. View at: Publisher Site | Google Scholar
  69. I. Siró and D. Plackett, “Microfibrillated cellulose and new nanocomposite materials: a review,” Cellulose, vol. 17, no. 3, pp. 459–494, 2010. View at: Publisher Site | Google Scholar
  70. T. Saito, R. Kuramae, J. Wohlert, L. A. Berglund, and A. Isogai, “An ultrastrong nanofibrillar biomaterial: the strength of single cellulose nanofibrils revealed via sonication-induced fragmentation,” Biomacromolecules, vol. 14, no. 1, pp. 248–253, 2012. View at: Publisher Site | Google Scholar
  71. R. Endo, T. Saito, and A. Isogai, “TEMPO-oxidized cellulose nanofibril/poly(vinyl alcohol) composite drawn fibers,” Polymer, vol. 54, no. 2, pp. 935–941, 2013. View at: Publisher Site | Google Scholar
  72. C. Zhou, R. Chu, R. Wu, and Q. Wu, “Electrospun polyethylene oxide/cellulose nanocrystal composite nanofibrous mats with homogeneous and heterogeneous microstructures,” Biomacromolecules, vol. 12, no. 7, pp. 2617–2625, 2011. View at: Publisher Site | Google Scholar
  73. Z. Li, S. Renneckar, and J. R. Barone, “Nanocomposites prepared by in situ enzymatic polymerization of phenol with tempo-oxidized nanocellulose,” Cellulose, vol. 17, no. 1, pp. 57–68, 2010. View at: Publisher Site | Google Scholar
  74. Y. Wang, X. Cao, and L. Zhang, “Effects of cellulose whiskers on properties of soy protein thermoplastics,” Macromolecular Bioscience, vol. 6, no. 7, pp. 524–531, 2006. View at: Publisher Site | Google Scholar
  75. X. Huang and A. Netravali, “Biodegradable green composites made using bamboo micro/nano-fibrils and chemically modified soy protein resin,” Composites Science and Technology, vol. 69, no. 7-8, pp. 1009–1015, 2009. View at: Publisher Site | Google Scholar
  76. G. Siqueira, J. Bras, and A. Dufresne, “Cellulosic bionanocomposites: a review of preparation, properties and applications,” Polymers, vol. 2, no. 4, pp. 728–765, 2010. View at: Publisher Site | Google Scholar
  77. Y. Choi and J. Simonsen, “Cellulose nanocrystal-filled carboxymethyl cellulose nanocomposites,” Journal of Nanoscience and Nanotechnology, vol. 6, no. 3, pp. 633–639, 2006. View at: Publisher Site | Google Scholar
  78. G. Chinga-Carrasco and K. Syverud, “On the structure and oxygen transmission rate of biodegradable cellulose nanobarriers,” Nanoscale Research Letters, vol. 7, no. 1, 2012. View at: Publisher Site | Google Scholar
  79. H. Fukuzumi, T. Saito, S. Iwamoto et al., “Pore size determination of TEMPO-oxidized cellulose nanofibril films by positron annihilation lifetime spectroscopy,” Biomacromolecules, vol. 12, no. 11, pp. 4057–4062, 2011. View at: Publisher Site | Google Scholar
  80. L. Petersson and K. Oksman, “Biopolymer based nanocomposites: comparing layered silicates and microcrystalline cellulose as nanoreinforcement,” Composites Science and Technology, vol. 66, no. 13, pp. 2187–2196, 2006. View at: Publisher Site | Google Scholar
  81. H. Fukuzumi, T. Saito, T. Iwata, Y. Kumamoto, and A. Isogai, “Transparent and high gas barrier films of cellulose nanofibers prepared by TEMPO-mediated oxidation,” Biomacromolecules, vol. 10, no. 1, pp. 162–165, 2009. View at: Publisher Site | Google Scholar
  82. K. Syverud and P. Stenius, “Strength and barrier properties of MFC films,” Cellulose, vol. 16, no. 1, pp. 75–85, 2009. View at: Publisher Site | Google Scholar
  83. G. Rampinelli, L. Di Landro, and T. Fujii, “Characterization of biomaterials based on microfibrillated cellulose with different modifications,” Journal of Reinforced Plastics and Composites, vol. 29, no. 12, pp. 1793–1803, 2010. View at: Publisher Site | Google Scholar
  84. Q. Li, H. Liu, S. Zhang et al., “Superhydrophobic electrically conductive paper for ultrasensitive strain sensor with excellent anticorrosion and self-cleaning property,” ACS Applied Materials & Interfaces, vol. 11, no. 24, pp. 21904–21914, 2019. View at: Publisher Site | Google Scholar
  85. X. Wang, Y. Pan, X. Liu et al., “Facile fabrication of superhydrophobic and eco-friendly poly(lactic acid) foam for oil–water separation via skin peeling,” ACS Applied Materials & Interfaces, vol. 11, no. 15, pp. 14362–14367, 2019. View at: Publisher Site | Google Scholar
  86. Y.-J. Zhang, X.-Z. Ma, L. Gan, T. Xia, J. Shen, and J. Huang, “Fabrication of fluorescent cellulose nanocrystal via controllable chemical modification towards selective and quantitative detection of cu (II) ion,” Cellulose, vol. 25, no. 10, pp. 5831–5842, 2018. View at: Publisher Site | Google Scholar
  87. S. Sultan and A. P. Mathew, “3D printed scaffolds with gradient porosity based on a cellulose nanocrystal hydrogel,” Nanoscale, vol. 10, no. 9, pp. 4421–4431, 2018. View at: Publisher Site | Google Scholar
  88. V. L. Pushparaj, M. M. Shaijumon, A. Kumar et al., “Flexible energy storage devices based on nanocomposite paper,” Proceedings of the National Academy of Sciences, vol. 104, no. 34, pp. 13574–13577, 2007. View at: Publisher Site | Google Scholar
  89. H. Zhu, Z. Xiao, D. Liu et al., “Biodegradable transparent substrates for flexible organic-light-emitting diodes,” Energy & Environmental Science, vol. 6, no. 7, pp. 2105–2111, 2013. View at: Publisher Site | Google Scholar
  90. Q. Niu, K. Gao, and Z. Shao, “Cellulose nanofiber/single-walled carbon nanotube hybrid non-woven macrofiber mats as novel wearable supercapacitors with excellent stability, tailorability and reliability,” Nanoscale, vol. 6, no. 8, pp. 4083–4088, 2014. View at: Publisher Site | Google Scholar
  91. K. Gao, Z. Shao, X. Wu et al., “Cellulose nanofibers/reduced graphene oxide flexible transparent conductive paper,” Carbohydrate Polymers, vol. 97, no. 1, pp. 243–251, 2013. View at: Publisher Site | Google Scholar

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