Nanocellulose‐based polymer composites for energy applications—A review

A review on the enhancement of circular economy aspects focusing on nanocellulose composites

Researchers are now focusing on using the circular economy model to manufacture nanocellulose composites due to growing environmental issues related to waste management. The circular economy model offers a sustainable solution to the problem by optimizing resource efficiency and waste management by reducing waste, maintaining value over time, minimizing the use of primary resources, and creating closed loops for goods, components, and materials. With the use of the circular economy model, waste, such as industrial, agricultural, and textile waste, is used again to produce new products, which can solve waste management issues and improve resource efficiency. In order to encourage the use of circular economy ideas with a specific focus on nanocellulose composites, this review examines the concept of using circular economy, and explores ways to make nanocellulose composites from different types of waste, such as industrial, agricultural, and textile waste. Furthermore, this review investigates the application of nanocellulose composites across multiple industries. In addition, this review provides researchers useful insights of how circular economics can be applied to the development of nanocellulose composites, which have the goal of creating a flexible and environmentally friendly material that can address waste management issues and optimize resource efficiency.

Nanocellulose-stabilized nanocomposites for effective Hg(II) removal and detection: a comprehensive review

Mercury pollution, with India ranked as the world's second-largest emitter, poses a critical environmental and public health challenge and underscores the need for rigorous research and effective mitigation strategies. Nanocellulose is derived from cellulose, the most abundant natural polymer on earth, and stands out as an excellent choice for mercury ion remediation due to its remarkable adsorption capacity, which is attributed to its high specific surface area and abundant functional groups, enabling efficient Hg(II) ion removal from contaminated water sources. This review paper investigates the compelling potential of nanocellulose as a scavenging tool for Hg(II) ion contamination. The comprehensive examination encompasses the fundamental attributes of nanocellulose, its diverse fabrication techniques, and the innovative development methods of nanocellulose-based nanocomposites. The paper further delves into the mechanisms that underlie Hg removal using nanocellulose, as well as the integration of nanocellulose in Hg detection methodologies, and also acknowledges the substantial challenges that lie ahead. This review aims to pave the way for sustainable solutions in mitigating Hg contamination using nanocellulose-based nanocomposites to address the global context of this environmental concern.

Fillers and methods to improve the effective (out-plane) thermal conductivity of polymeric thermal interface materials - A review

The internet of things and growing demand for smaller and more advanced devices has created the problem of high heat production in electronic equipment, which greatly reduces the work performance and life of the electronic instruments. Thermal interface material (TIM) is placed in between heat generating micro-chip and the heat dissipater to conduct all the produced heat to the heat sink. The development of suitable TIM with excellent thermal conductivity (TC) in both in-plane and through-plane directions is a very important need at present. For efficient thermal management, polymer composites are potential candidates. But in general, their thermal conductivity is low compared to that of metals. The filler integration into the polymer matrix is one of the two approaches used to increase the thermal conductivity of polymer composites and is also easy to scale up for industrial production. Another way to achieve this is to change the structure of polymer chains, which fall out of the scope of this work. In this review, considering the first approach, the authors have summarized recent developments in many types of fillers with different scenarios by providing multiple cases with successful strategies to improve through-plane thermal conductivity (TPTC) (k⊥). For a better understanding of TC, a comprehensive background is presented. Several methods to improve the effective (out-plane) thermal conductivity of polymer composites and different theoretical models for the calculation of TC are also discussed. In the end, it is given a detailed conclusion that provides drawbacks of some fillers, multiple significant routes recommended by other researchers to build thermally conductive polymer composites, future aspects along with direction so that the researchers can get a guideline to design an effective polymer-based thermal interface material.

Advanced Functionalized Materials Based on Layer-by-Layer Assembled Natural Cellulose Nanofiber for Electrodes: A Review

The depletion of fossil fuel resources and its impact on the environment provide a compelling motivation for the development of sustainable energy sources to meet the increasing demand for energy. Accordingly, research and development of energy storage devices have emerged as a critical area of focus. The electrode materials are critical in the electrochemical performance of energy storage devices, such as energy storage capacity and cycle life. Cellulose nanofiber (CNF) represents an important substrate with potentials in the applications of green electrode materials due to their environmental sustainability and excellent compatibility. By utilizing the layer-by layer (LbL) process, well-defined nanoscale multilayer structure is prepared on a variety of substrates. In recent years, increasing attention has focused on electrode materials produced from LbL process on CNFs to yield electrodes with exceptional properties, such as high specific surface area, outstanding electrical conductivity, superior electrochemical activity, and exceptional mechanical stability. This review provides a comprehensive overview on the development of functional CNF via the LbL approach as electrode materials.

Exploring nanocellulose frontiers: A comprehensive review of its extraction, properties, and pioneering applications in the automotive and biomedical industries

Material is an inseparable entity for humans to serve different purposes. However, synthetic polymers represent a major category of anthropogenic pollutants with detrimental impacts on natural ecosystems. This escalating environmental issue is characterized by the accumulation of non-biodegradable plastic materials, which pose serious threats to the health of our planet's ecosystem. Cellulose is becoming a focal point for many researchers due to its high availability. It has been used to serve various purposes. Recent scientific advancements have unveiled innovative prospects for the utilization of nanocellulose within the area of advanced science. This comprehensive review investigates deeply into the field of nanocellulose, explaining the methodologies employed in separating nanocellulose from cellulose. It also explains upon two intricately examined applications that emphasize the pivotal role of nanocellulose in nanocomposites. The initial instance pertains to the automotive sector, encompassing cutting-edge applications in electric vehicle (EV) batteries, while the second exemplifies the use of nanocellulose in the field of biomedical applications like otorhinolaryngology, ophthalmology, and wound dressing. This review aims to provide comprehensive information starting from the definitions, identifying the sources of the nanocellulose and its extraction, and ending with the recent applications in the emerging field such as energy storage and biomedical applications.

Nanocellulose-based composite aerogels toward the environmental protection: Preparation, modification and applications

Nanocellulose aerogel has the advantages of porosity, low density and high specific surface area, which can effectively realize the adsorption and treatment of wastewater waste gas. The methods of preparing nanocellulose mainly include mechanical, chemical and biological methods. Nanocellulose is formed into nanocellulose aerogel after gelation, solvent replacement and drying processes. Based on the advantages of easy modification of nanocellulose aerogels, nanocellulose aerogels can be functionalized with conductive fillers, reinforcing fillers and other materials to give nanocellulose aerogels in electrical, mechanical and other properties. Through functionalization, the properties of nanocellulose composite aerogel such as hydrophobicity and adsorption are improved, and the aerogel is endowed with the ability of electrical conductivity and electromagnetic shielding. Through functionalization, the applicability and general applicability of nanocellulose composite aerogel in the field of environmental protection are improved. In this paper, the preparation and functional modification methods of nanocellulose aerogels are reviewed, and the application prospects of nanocellulose composite aerogels in common environmental protection fields such as dye adsorption, heavy metal ion adsorption, gas adsorption, electromagnetic shielding, and oil-water separation are specifically reviewed, and new solutions are proposed.

Current and Potential Applications of Green Membranes with Nanocellulose

Large-scale applications of nanotechnology have been extensively studied within the last decade. By exploiting certain advantageous properties of nanomaterials, multifunctional products can be manufactured that can contribute to the improvement of everyday life. In recent years, one such material has been nanocellulose. Nanocellulose (NC) is a naturally occurring nanomaterial and a high-performance additive extracted from plant fibers. This sustainable material is characterized by a unique combination of exceptional properties, including high tensile strength, biocompatibility, and electrical conductivity. In recent studies, these unique properties of nanocellulose have been analyzed and applied to processes related to membrane technology. This article provides a review of recent synthesis methods and characterization of nanocellulose-based membranes, followed by a study of their applications on a larger scale. The article reviews successful case studies of the incorporation of nanocellulose in different types of membrane materials, as well as their utilization in water purification, desalination, gas separations/gas barriers, and antimicrobial applications, in an effort to provide an enhanced comprehension of their capabilities in commercial products.

Perovskite-Nanocrystal-Doped Cellulose Nanocrystal Ligands for Electrospun Nanofibers with Excellent Stability

Because of their exceptional physical and thermal properties, cellulose nanocrystals (CNCs) are a highly promising bio-based material for reinforcing fillers. Studies have revealed that some functional groups from CNCs can be used as a capping ligand to coordinate with metal nanoparticles or semiconductor quantum dots during the fabrication of novel complex materials. Therefore, through CNCs ligand encapsulation and electrospinning, perovskite-NC-embedded nanofibers with exceptional optical and thermal stability are demonstrated. The results indicate that, after continuous irradiation or heat cycling, the relative photoluminescence (PL) emission intensity of the CNCs-capped perovskite-NC-embedded nanofibers is maintained at ≈90%. However, the relative PL emission intensity of both ligand-free and long-alkyl-ligand-doped perovskite-NC-embedded nanofibers decrease to almost 0%. These results are attributable to the formation of specific clusters of perovskite NCs along with the CNCs structure and thermal property improvement of polymers. CNCs-doped luminous complex materials offer a promising avenue for stability-demanding optoelectronic devices and other novel optical applications.

Understanding Nanocellulose-Water Interactions: Turning a Detriment into an Asset

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose-water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

Alkaline Degradation of Plant Fiber Reinforcements in Geopolymer: A Review

Plant fibers (PFs), such as hemp, Coir, and straw, are abundant in resources, low in price, light weight, biodegradable, have good adhesion to the matrix, and have a broad prospect as reinforcements. However, the degradation of PFs in the alkaline matrix is one of the main factors that affects the durability of these composites. PFs have good compatibility with cement and the geopolymer matrix. They can induce gel growth of cement-based materials and have a good toughening effect. The water absorption of the hollow structure of the PF can accelerate the degradation of the fiber on the one hand and serve as the inner curing fiber for the continuous hydration of the base material on the other. PF is easily deteriorated in the alkaline matrix, which has a negative effect on composites. The classification and properties of PFs, the bonding mechanism of the interface between PF reinforcements and the matrix, the water absorption of PF, and its compatibility with the matrix were summarized. The degradation of PFs in the alkaline matrix and solution, drying and wetting cycle conditions, and high-temperature conditions were reviewed. Finally, some paths to improve the alkaline degradation of PF reinforcement in the alkaline matrix were proposed.

Nanocellulose-Based Nanocomposites for Sustainable Applications: A Review

Nanocellulose has emerged in recent years as one of the most notable green materials available due to its numerous appealing factors, including its non-toxic nature, biodegradability, high aspect ratio, superior mechanical capabilities, remarkable optical properties, anisotropic shape, high mechanical strength, excellent biocompatibility and tailorable surface chemistry. It is proving to be a promising material in a range of applications pertinent to the material engineering to biomedical applications. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations. This review presents an overview of general concepts in nanocellulose-based nanocomposites for sustainable applications. Beginning with a brief introduction of cellulose, nanocellulose sources, structural characteristics and the extraction process for those new to the area, we go on to more in-depth content. Following that, the research on techniques used to modify the surface properties of nanocellulose by functionalizing surface hydroxyl groups to impart desirable hydrophilic-hydrophobic balance, as well as their characteristics and functionalization strategies, were explained. The usage of nanocellulose in nanocomposites in versatile fields, as well as novel and foreseen markets of nanocellulose products, are also discussed. Finally, the difficulties, challenges and prospects of materials based on nanocellulose are then discussed in the last section for readers searching for future high-end eco-friendly functional materials.

Bacteria cellulose framework-supported solid composite polymer electrolytes for ambient-temperature lithium metal batteries

Composite polymer electrolyte (CPE) films with high room temperature ionic conductivity are urgently needed for the practical application of high-safety solid-state batteries (SSBs). Here, a flexible polymer-polymer CPE thin film reinforced by a three-dimensional (3D) bacterial cellulose (BC) framework derived from natural BC hydrogel was prepared via thein situphoto-polymerization method. The BC film was utilized as the supporting matrix to ensure high flexibility and mechanical strength. The BC-CPE attained a high room temperature ionic conductivity of 1.3 × 10^-4S cm^-1. The Li∣BC-CPE∣Li symmetric cell manifested stable cycles of more than 1200 h. The LCO∣BC-CPE∣Li full cell attained an initial discharge specific capacity of 128.7 mAh g^-1with 82.6% discharge capacity retention after 150 cycles at 0.2 C under room temperature. The proposed polymer-polymer CPE configuration represents a promising route for manufacturing environmental SSBs, especially since cellulose biomaterials are abundant in nature.

A review of graphene derivative enhancers for perovskite solar cells

Due to the finite nature, health and environmental hazards currently associated with the use of fossil energy resources, there is a global drive to hasten the development and deployment of renewable energy technologies. One such area encompasses perovskite solar cells (PSCs) that have shown photoconversion efficiencies (PCE) comparable to silicon-based photovoltaics, but their commercialisation has been set back by short-term stability and toxicity issues, among others. A tremendous potential to overcome these drawbacks is presented by the emerging applications of graphene derivative-based materials in PSCs as substitutes or components, composites with other functional materials, and enhancers of charge transport, blocking action, exciton dissociation, substrate coverage, sensitisation and stabilisation. This review aims to illustrate how these highly capable carbon-based materials can advance PSCs by critically outlining and discussing their current applications and strategically identifying prospective research avenues. The reviewed works show that graphene derivatives have great potential in boosting the performance and stability of PSCs through morphological modifications and compositional engineering. This can drive the sustainability and commercial viability aspects of PSCs.

Mechanochemical Transformations of Biomass into Functional Materials

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Enhanced Hydrophobicity in Nanocellulose-Based Materials: Toward Green Wearable Devices

Nanocellulose is a promising material for fabricating green, biocompatible, flexible, and foldable devices. One of the main issues of using nanocellulose as a fundamental component for wearable electronics is the influence of environmental conditions on it. The water adsorption promotes the swelling of nanopaper substrates, which directly affects the devices' electrical properties prepared on/with it. Here, plant-based nanocellulose substrates, and ink composites deposited on them, are chemically modified using hexamethyldisilazane to enhance the system's hydrophobicity. After the treatment, the electrical properties of the devices exhibit stable operation under humidity levels around 95%. Such stability demonstrates that the hexamethyldisilazane modification substantially suppresses the water adsorption on fundamental device structures, namely, substrate plus conducting ink. These results attest to the robustness necessary to use nanocellulose as a key material in wearable devices such as electronic skins and tattoos and contribute to the worldwide efforts to create biodegradable devices engineered in a more deterministic fashion.

The intrinsic piezoelectric properties of materials - a review with a focus on biological materials

Piezoelectricity, a linear electromechanical coupling, is of great interest due to its extensive applications including energy harvesters, biomedical, sensors, and automobiles. A growing amount of research has been done to investigate the energy harvesting potential of this phenomenon. Traditional piezoelectric inorganics show high piezoelectric outputs but are often brittle, inflexible and may contain toxic compounds such as lead. On the other hand, biological piezoelectric materials are biodegradable, biocompatible, abundant, low in toxicity and are easy to fabricate. Thus, they are useful for many applications such as tissue engineering, biomedical and energy harvesting. This paper attempts to explain the basis of piezoelectricity in biological and non-biological materials and research involved in those materials as well as applications and limitations of each type of piezoelectric material.

Piezoelectricity, a linear electromechanical coupling, is of great interest due to its extensive applications including energy harvesters, biomedical, sensors, and automobiles.

3D-Printable Nanocellulose-Based Functional Materials: Fundamentals and Applications

Nanomaterials obtained from sustainable and natural sources have seen tremendous growth in recent times due to increasing interest in utilizing readily and widely available resources. Nanocellulose materials extracted from renewable biomasses hold great promise for increasing the sustainability of conventional materials in various applications owing to their biocompatibility, mechanical properties, ease of functionalization, and high abundance. Nanocellulose can be used to reinforce mechanical strength, impart antimicrobial activity, provide lighter, biodegradable, and more robust materials for packaging, and produce photochromic and electrochromic devices. While the fabrication and properties of nanocellulose are generally well established, their implementation in novel products and applications requires surface modification, assembly, and manufacturability to enable rapid tooling and scalable production. Additive manufacturing techniques such as 3D printing can improve functionality and enhance the ability to customize products while reducing fabrication time and wastage of materials. This review article provides an overview of nanocellulose as a sustainable material, covering the different properties, preparation methods, printability and strategies to functionalize nanocellulose into 3D-printed constructs. The applications of 3D-printed nanocellulose composites in food, environmental, and energy devices are outlined, and an overview of challenges and opportunities is provided.

Research Progress on Durability of Cellulose Fiber-Reinforced Cement-Based Composites

The performance of cellulose fiber-reinforced cement-based composites (CFCCs) depends not only on the characteristics of the cement matrix and fibers but also on the bonding property of the matrix and fibers. The durability of cement-based composites including various properties such as impermeability, frost resistance, and carbonization resistance has an important impact on the long-term service life of the matrix structure. The presence of a large number of hydroxyl groups on the molecular chain of cellulose can promote the formation of intra- and intermolecular hydrogen bonds of cellulose. This special structure imparts the cellulose high hydrophilicity, which leads the cement hydration C-S-H gel to adhere to the surface of cellulosic fibers (CFs) and induce its growth. The cavity of CFs has good water absorption and can be used as an internal curing fiber for the continuous hydration of cement-based composites. But CFs in the Portland cement matrix tend to deteriorate under strong alkali conditions. This paper presents a review of the research on the durability of CFCCs. The methods and paths to improve the durability of CFCCs are summarized and analyzed from the perspectives of the internal curing of CFs, the deterioration of the performance of CFs in the matrix, and the use of many types of supplementary cementitious materials. Finally, the development and engineering application of CFCCs have been prospected.

Preparation and characterization of nanofibrous cellulose as solid polymer electrolyte for lithium-ion battery applications

A novel bacterial cellulose (BC)-based nanofiber material has been utilized as an ionic template for the battery system solid polymer electrolyte (SPE). The effect of drying techniques such as oven and freeze-drying on the gel-like material indicate differences in both visual and porous structures. The morphological structure of BC after oven and freeze-drying observed by field-emission scanning electron microscopy indicates that a more compact porous structure is found in freeze-dried BC than oven-dried BC. After the BC-based nanofiber immersion process into lithium hexafluorophosphate solution (1.0 M), the porous structure becomes a host for Li-ions, demonstrated by significant interactions between Li-ions from the salt and the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O groups of freeze-dried BC as shown in the infrared spectra. X-ray diffraction analysis of freeze-dried BC after immersion in electrolyte solution shows a lower degree of crystallinity, thus allowing an increase in Li-ion movement. As a result, freeze-dried BC has a better ionic conductivity of 2.71 × 10⁻² S cm⁻¹ than oven-dried BC, 6.00 × 10⁻³ S cm⁻¹. Freeze-dried BC as SPE also shows a larger electrochemical stability window around 3.5 V, reversible oxidation/reduction peaks at 3.29/3.64 V, and an initial capacity of 18 mAHr g⁻¹ at 0.2C. The high tensile strength of the freeze-dried BC membrane of 334 MPa with thermal stability up to 250 °C indicates the potential usage of freeze-dried BC as flexible SPE to dampen ionic leakage transfer.

Nanofibrous cellulose as solid polymer electrolyte for lithium-ion battery applications.

Nanocellulose Production Using Ionic Liquids with Enzymatic Pretreatment

Nanocellulose has gained increasing attention during the past decade, which is related to its unique properties and wide application. In this paper, nanocellulose samples were produced via hydrolysis with ionic liquids (1-ethyl-3-methylimidazole acetate (EmimOAc) and 1-allyl-3-methylimidazolium chloride (AmimCl)) from microcrystalline celluloses (Avicel and Whatman) subjected to enzymatic pretreatment. The obtained material was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The results showed that the nanocellulose had a regular and spherical structure with diameters of 30-40 nm and exhibited lower crystallinity and thermal stability than the material obtained after hydrolysis with Trichoderma reesei enzymes. However, the enzyme-pretreated Avicel had a particle size of about 200 nm and a cellulose II structure. A two-step process involving enzyme pretreatment and hydrolysis with ionic liquids resulted in the production of nanocellulose. Moreover, the particle size of nanocellulose and its structure depend on the ionic liquid used.

Becoming Sustainable, The New Frontier in Soft Robotics

The advancement of technology has a profound and far-reaching impact on the society, now penetrating all areas of life. From cradle to grave, one is supported by and depends on a wide range of electronic and robotic appliances, with an ever more intimate integration of the digital and biological spheres. These advances, however, often come at the price of negatively impacting our ecosystem, with growing demands on energy, contributions to greenhouse gas emissions and environmental pollution-from production to improper disposal. Mitigating these adverse effects is among the grand challenges of the society and at the forefront of materials research. The currently emerging forms of soft, biologically inspired electronics and robotics have the unique potential of becoming not only like their natural antitypes in performance and capabilities, but also in terms of their ecological footprint. This review outlines the rise of sustainable materials in soft and bioinspired robotics, targeting all robotic components from actuators to energy storage and electronics. The state-of-the-art in biobased robotics spans flourishing fields and applications ranging from microbots operating in vivo to biohybrid machines and fully biodegradable yet resilient actuators. These first steps initiate the evolution of robotics and guide them into a sustainable future.

Recent Developments in Nanocellulose-Based Aerogels in Thermal Applications: A Review

Naturally derived nanocellulose (NC) is a renewable, biodegradable nanomaterial with high strength, low density, high surface area, and tunable surface chemistry, which allows its interaction with other polymers and nanomaterials in a controlled manner. In recent years, NC aerogel has gathered a lot of attention due to environmental concerns. This review presents recent developments of NC-based aerogels and their controlled interactions with other polymers and nanomaterials for thermal applications that include electronic devices, the apparel industry, superinsulating materials, and flame-retardant smart building materials. After going through the distinctive properties of NC aerogels, they are orderly categorized and discussed as thermally insulated, thermally conductive, and flame-retardant materials.

Recent advances in 3D printing of nanocellulose: structure, preparation, and application prospects

Emerging cellulose nanomaterials extracted from agricultural biomasses have recently received extensive attention due to diminishing fossil resources. To further reduce the carbon footprints and wastage of valuable resources, additive manufacturing techniques of new nanocellulosic materials have been developed. Studies on the preparation and characterization of 3D-printable functional nanocellulosic materials have facilitated a deeper understanding into their desirable attributes such as high surface area, biocompatibility, and ease of functionalization. In this critical review, we compare and highlight the different methods of extracting nanocellulose from biorenewable resources and the strategies for transforming the obtained nanocellulose into nanocomposites with high 3D printability. Optimistic technical applications of 3D-printed nanocellulose in biomedical, electronics, and environmental fields are finally described and evaluated for future perspectives.

Controlled Arrangement of Nanocellulose in Polymeric Matrix: From Reinforcement to Functionality

Nanocellulose, the most abundant crystalline polysaccharide nanomaterial on Earth, has been widely used for the reinforcement of polymeric materials owing to its high elastic modulus, low density, high aspect ratio, biocompatibility, and biodegradability. In this Perspective, we offer a brief overview of recent progress in the controllable arrangement of nanocellulose in polymeric matrices, including highly oriented structure, helical structure, and gradient structure. We then discuss the current nanotechnologies that enable the arrangement of nanocellulose in nanocomposite materials. Finally, we describe future opportunities, challenges, and research directions in this active research area.

Toward Biodegradable Electronics: Ionic Diodes Based on a Cellulose Nanocrystal-Agarose Hydrogel

Bioderived cellulose nanocrystals (CNCs) are used to create light, flexible, biocompatible, and biodegradable electronic devices. Herein, surface modification of cellulose nanocrystals was employed to fabricate cationic and anionic CNCs. Subsequently, we demonstrated rectification behavior from a fixed junction between two agarose hydrogels doped with cationic and anionic cellulose nanocrystals. The current rectification ratio reaches 70 reproducibly, which is significantly higher than that for analogous diodes generated with microfibrillated cellulose (∼15) and the first polyelectrolyte gel diode (∼40). The current-voltage characteristics of the CNC-hydrogel diode are influenced by concentration, gel thickness, scanning frequency, and applied voltage. The high surface area of CNC resulted in high charge density after surface modification, which in turn resulted in good rectification behavior from only small amounts of dopant material.

Cellulose Nanocrystals/Graphene Hybrids-A Promising New Class of Materials for Advanced Applications

With the growth of global fossil-based resource consumption and the environmental concern, there is an urgent need to develop sustainable and environmentally friendly materials, which exhibit promising properties and could maintain an acceptable level of performance to substitute the petroleum-based ones. As elite nanomaterials, cellulose nanocrystals (CNC) derived from natural renewable resources, exhibit excellent physicochemical properties, biodegradability and biocompatibility and have attracted tremendous interest nowadays. Their combination with other nanomaterials such as graphene-based materials (GNM) has been revealed to be useful and generated new hybrid materials with fascinating physicochemical characteristics and performances. In this context, the review presented herein describes the quickly growing field of a new emerging generation of CNC/GNM hybrids, with a focus on strategies for their preparation and most relevant achievements. These hybrids showed great promise in a wide range of applications such as separation, energy storage, electronic, optic, biomedical, catalysis and food packaging. Some basic concepts and general background on the preparation of CNC and GNM as well as their key features are provided ahead.

Nanocellulose: From Fundamentals to Advanced Applications

Over the past few years, nanocellulose (NC), cellulose in the form of nanostructures, has been proved to be one of the most prominent green materials of modern times. NC materials have gained growing interests owing to their attractive and excellent characteristics such as abundance, high aspect ratio, better mechanical properties, renewability, and biocompatibility. The abundant hydroxyl functional groups allow a wide range of functionalizations via chemical reactions, leading to developing various materials with tunable features. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations (particularly for the reports of the past 3 years). We start with a concise background of cellulose, its structural organization as well as the nomenclature of cellulose nanomaterials for beginners in this field. Then, different experimental procedures for the production of nanocelluloses, their properties, and functionalization approaches were elaborated. Furthermore, a number of recent and emerging uses of nanocellulose in nanocomposites, Pickering emulsifiers, wood adhesives, wastewater treatment, as well as in new evolving biomedical applications are presented. Finally, the challenges and opportunities of NC-based emerging materials are discussed.