Multi-Responsive Supercapacitors from Chiral Nematic Cellulose Nanocrystal-Based Activated Carbon Aerogels

Hierarchical Nanoporous Carbons with an Integrated Activation Using 3D Flower-Like ZnO Microspheres and KOH for Flexible EDL Capacitor with a High Operating Potential

Activated nanoporous carbons are widely used in various applications, where their efficiency is largely determined by their specific surface area and pore structure. Traditional KOH-assisted chemical activation methods primarily produce micropores, limiting the performance of these porous carbons in applications requiring a hierarchical arrangement of micro, meso, and macropores. This study introduces a novel integrated activation strategy using 3D flower-like microsphere (3DFM) ZnO and KOH to synthesize nanoporous carbons from Sesbania Grandiflora side shoots. The porous nanosheet tips and microsphere bulk of 3DFM-ZnO generate mesopores and macropores, while KOH induces microporosity, resulting in a hierarchical structure with an ultrahigh specific surface area of 4114 m2 g-1. The fabricated activated carbon electrodes with the combination of macro, meso, and micropores exhibit high specific capacitances of 672 F g-1 for the positive electrode and 756 F g-1 for the negative electrode. The performance of electrodes is optimized with the proper selection of electrolytic ions for positive and negative electrodes. A high operating potential window of 2.7 V is achieved in a symmetric device through charge-balanced mass loading. The fabricated flexible electric double-layer capacitor demonstrates a maximum specific energy of 128.2 W h kg-1 at a specific power of 1.35 kW kg-1.

Cellulose aerogel-based copper oxide/carbon composite for supercapacitor electrode

Carbon composite is one of the most competitive electrode materials for supercapacitor, and improving its energy density remains a significant challenge. The copper oxide/carbon composites with high specific surface area were prepared from the cellulose aerogel loaded with copper salts. The copper oxide/carbon composite electrode material, deriving from copper sulfate, reached a specific capacitance of 1001 F g-1 at 2 A g-1, with an energy density of 139.0 W h kg-1. After 500 cycles, the capacitance retention rate is 98.06%. An asymmetric supercapacitor was assembled using this material as positive electrode material, activated carbon as negative electrode material, and 3.0 M KOH as electrolyte. It exhibited good reversible capacity and low voltage drop loss within a voltage window of 0-1.2 V, and its specific capacitance and energy density achieved 125 F g-1 and 6.3 W h kg-1 at a current density of 0.1 A g-1, respectively.

Chiral Nematic Cellulose Nanocrystal Films for Enhanced Charge Separation and Quantum-Confined Stark Effect

Efficient charge separation is essential in various optoelectronic systems, yet it continues to pose substantial challenges. Building upon the recent evidence that chiral biomolecules can function as electron spin filters, this study aims to extend the application of chirality-driven charge separation from the molecular level to the mesoscale and supramolecular scale. Utilizing cellulose nanocrystals (CNCs) derived from cellulose, the most abundant biomaterial on Earth, this research leverages their self-assembly into chiral nematic structures and their dielectric properties. A device is introduced featuring a chiral nematic hybrid film composed of CNCs and quantum dots (QDs), decorated with iron oxide nanoparticles. Using the quantum-confined Stark effect (QCSE) to probe charge separation, we reveal significant sensitivity to the circular polarization of light and the chiral nematic structure of the film. This approach achieves effective, long-lasting charge separation, both locally and across length scales exceeding 1 μm, enabling potential applications such as self-assembled devices that combine photovoltaic cells with electric capacitance as well as optical electric-field hybrid biosensors.

Designing for Degradation: Transient Devices Enabled by (Nano)Cellulose

Transient technology involves materials and devices that undergo controlled degradation after a reliable operation period. This groundbreaking strategy offers significant advantages over conventional devices based on non-renewable materials by limiting environmental exposure to potentially hazardous components after disposal, and by increasing material circularity. As the most abundant naturally occurring polymer on Earth, cellulose is an attractive material for this purpose. Besides, (nano)celluloses are inherently biodegradable and have competitive mechanical, optical, thermal, and ionic conductivity properties that can be exploited to develop sustainable devices and avoid the end-of-life issues associated with conventional systems. Despite its potential, few efforts have been made to review current advances in cellulose-based transient technology. Therefore, this review catalogs the state-of-the-art developments in transient devices enabled by cellulosic materials. To provide a wide perspective, the various degradation mechanisms involved in cellulosic transient devices are introduced. The advanced capabilities of transient cellulosic systems in sensing, photonics, energy storage, electronics, and biomedicine are also highlighted. Current bottlenecks toward successful implementation are discussed, with material circularity and environmental impact metrics at the center. It is believed that this review will serve as a valuable resource for the proliferation of cellulose-based transient technology and its implementation into fully integrated, circular, and environmentally sustainable devices.

Polysaccharide Nanocrystals-Based Chiral Nematic Structures: From Self-Assembly Mechanisms, Regulation, to Applications

Chiral architectures, one of the key structural features of natural systems ranging from the nanoscale to macroscale, are an infinite source of inspiration for functional materials. Researchers have been, and still are, strongly pursuing the goal of constructing such structures with renewable and sustainable building blocks via simple and efficient strategies. With the merits of high sustainability, renewability, and the ability to self-assemble into chiral nematic structures in aqueous suspensions that can be preserved in the solid state, polysaccharide nanocrystals (PNs) including cellulose nanocrystals (CNCs) and chitin nanocrystals (ChNCs) offer opportunities to reach the target. We herein provide a comprehensive review that focuses on the development of CNCs and ChNCs for the use in advanced functional materials. First, the introduction of CNCs and ChNCs, and cellulose- and chitin-formed chiral nematic organizations in the natural world, are given. Then, the self-assembly process of such PNs and the factors influencing this process are comprehensively discussed. After that, we showcased the emerging applications of the self-assembled chiral nematic structures of CNCs and ChNCs. Finally, this review concludes with perspectives on the challenges and opportunities in this field.

Large-Scale Production and Integrated Application of Micro-Supercapacitors

Micro-supercapacitors, emerging as promising micro-energy storage devices, have attracted significant attention due to their unique features. This comprehensive review focuses on two key aspects: the scalable fabrication of MSCs and their diverse applications. The review begins by elucidating the energy storage mechanisms and guiding principles for designing high-performance devices. It subsequently explores recent advancements in scalable fabrication techniques for electrode materials and micro-nano fabrication technologies for micro-devices. The discussion encompasses critical application domains, including multifunctional MSCs, energy storage integration, integrated power generation, and integrated applications. Despite notable progress, there are still some challenges such as large-scale production of electrode material, well-controlled fabrication technology, and scalable integrated manufacture. The summary concludes by emphasizing the need for future research to enhance micro-supercapacitor performance, reduce production costs, achieve large-scale production, and explore synergies with other energy storage technologies. This collective effort aims to propel MSCs from laboratory innovation to market viability, providing robust energy storage solutions for MEMS and portable electronics.

Cellulose nanocrystals in the development of biodegradable materials: A review on CNC resources, modification, and their hybridization

The escalating demand for sustainable materials has propelled cellulose into the spotlight as a promising alternative to petroleum-based products. As the most abundant organic polymer on Earth, cellulose is ubiquitous, found in plants, bacteria, and even a unique marine animal-the tunicate. Cellulose polymers naturally give rise to microscale semi-crystalline fibers and nanoscale crystalline regions known as cellulose nanocrystals (CNCs). Exhibiting rod-like structures with widths spanning 3 to 50 nm and lengths ranging from 50 nm to several microns, CNC characteristics vary based on the cellulose source. The degree of crystallinity, crucial for CNC properties, fluctuates between 49 and 95 % depending on the source and synthesis method. CNCs, with their exceptional properties such as high aspect ratio, relatively low density (≈1.6 g cm-3), high axial elastic modulus (≈150 GPa), significant tensile strength, and birefringence, emerge as ideal candidates for biodegradable fillers in nanocomposites and functional materials. The percolation threshold, a mathematical concept defining long-range connectivity between filler and polymer, governs the effectiveness of reinforcement in nanocomposites. This threshold is intricately influenced by the aspect ratio and molecular interaction strength, impacting CNC performance in polymeric and pure nanocomposite materials. This comprehensive review explores diverse aspects of CNCs, encompassing their derivation from various sources, methods of modification (both physical and chemical), and hybridization with heterogeneous fillers. Special attention is devoted to the hybridization of CNCs derived from tunicates (TCNC) with those from wood (WCNC), leveraging the distinct advantages of each. The overarching objective is to demonstrate how this hybridization strategy mitigates the limitations of WCNC in composite materials, offering improved interaction and enhanced percolation. This, in turn, is anticipated to elevate the reinforcing effects and pave the way for the development of nanocomposites with tunable viscoelastic, physicochemical, and mechanical properties.

Hybrid Materials of Bio-Based Aerogels for Sustainable Packaging Solutions

This review explores the field of hybrid materials in the context of bio-based aerogels for the development of sustainable packaging solutions. Increasing global concern over environmental degradation and the growing demand for environmentally friendly alternatives to conventional packaging materials have led to a growing interest in the synthesis and application of bio-based aerogels. These aerogels, which are derived from renewable resources such as biopolymers and biomass, have unique properties such as a lightweight structure, excellent thermal insulation, and biodegradability. The manuscript addresses the innovative integration of bio-based aerogels with various other materials such as nanoparticles, polymers, and additives to improve their mechanical, barrier, and functional properties for packaging applications. It critically analyzes recent advances in hybridization strategies and highlights their impact on the overall performance and sustainability of packaging materials. In addition, the article identifies the key challenges and future prospects associated with the development and commercialization of hybrid bio-based aerogel packaging materials. The synthesis of this knowledge is intended to contribute to ongoing efforts to create environmentally friendly alternatives that address the current problems associated with conventional packaging while promoting a deeper understanding of the potential of hybrid materials for sustainable packaging solutions.