Hierarchical architecture for flexible energy storage

Nematic to Cholesteric Transformation in the Cellulose Nanocrystal Droplet Phase

Nucleation, growth, and transformation of chirality in nanomaterial systems is a growing research topic with broad interest in tunable and configurable chiroptical materials. Similar to other one-dimensional nanomaterials, cellulose nanocrystals (CNCs), which are nanorods of naturally abundant biopolymer cellulose, display chiral or cholesteric liquid crystal (LC) phases in the form of tactoids. However, the nucleation and growth of the cholesteric CNC tactoids to equilibrium chiral structures and their morphological transformations are yet to be critically assessed. We noticed that the onset of liquid crystal formation in CNC suspensions is characterized by the nucleation of a nematic tactoid that grows in volume and spontaneously transforms into a cholesteric tactoid. The cholesteric tactoids merge with the neighboring tactoids to form bulk cholesteric mesophases with various configurational palettes. We applied scaling laws from the energy functional theory and found suitable agreement with the morphological transformation of the tactoid droplets monitored for their fine structure and orientation by quantitative polarized light imaging.

Chiral Liquid Crystalline Properties of Cellulose Nanocrystals: Fundamentals and Applications

By using an independent self-assembly process that is occasionally controlled by evaporation, cellulose nanocrystals (CNCs) may create films (pure or in conjunction with other materials) that have iridescent structural colors. The self-forming chiral nematic structures and environmental safety of a new class of photonic liquid crystals (LCs), referred to as CNCs and CNC-embedded materials, make them simple to make and treat. The structure of the matrix interacts with light to give structural coloring, as opposed to other dye pigments, which interact with light by adsorption and reflection. Understanding how CNC self-assembly constructs structures is vital in several fields, including physics, science, and engineering. To constructure this review, the colloidal characteristics of CNC particles and their behavior during the formation of liquid crystals and gelling were studied. Then, some of the recognized applications for these naturally occurring nanoparticles were summarized. Different factors were considered, including the CNC aspect ratio, surface chemistry, concentration, the amount of time needed to produce an anisotropic phase, and the addition of additional substances to the suspension medium. The effects of alignment and the drying process conditions on structural changes are also covered. The focus of this study however is on the optical properties of the films as well as the impact of the aforementioned factors on the final transparency, iridescent colors, and versus the overall response of these bioinspired photonic materials. Control of the examined factors was found to be necessary to produce reliable materials for optoelectronics, intelligent inks and papers, transparent flexible support for electronics, and decorative coatings and films.

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

Chirality has become an important research subject. The research areas associated with chirality are under substantial development. Meanwhile, graphene is a rapidly growing star material and has hard-wired into diverse disciplines. Rational combination of graphene and chirality undoubtedly creates unprecedented functional materials and may also lead to great findings. This hypothesis has been clearly justified by the sizable number of studies. Unfortunately, there has not been any previous review paper summarizing the scattered studies and advancements on this topic so far. This overview paper attempts to review the progress made in chiral materials developed from graphene and their derivatives, with the hope of providing a systemic knowledge about the construction of chiral graphenes and chiral applications thereof. Recently emerging directions, existing challenges, and future perspectives are also presented. It is hoped this paper will arouse more interest and promote further faster progress in these significant research areas.

Assembly of MnO/CNC/rGO fibers from colloidal liquid crystal for flexible supercapacitors via a continuous one-process method

Flexible supercapacitors based on fiber shaped electrodes exhibit great potential for practical applications in smart fabrics owing to their light weight, good flexibility, and excellent weaveability. Herein, manganosite/carbonized cellulose nanocrystal/reduced graphene oxide (MnO/CNC/rGO) ternary composite fibers were fabricated from liquid crystal spinning dopes through a continuous one-process method. The assembly of CNC and manganese oxide nanoparticles in GO aqueous dispersion not only prevents GO nanosheets from restacking, but also ensures a uniform intercalation of nanoparticles. After a chemical and thermal reduction, the carbonized CNC contributes for additional electrical double layer capacitance while the MnO for faradaic pseudocapacitance. A fiber supercapacitor was assembled by arranging two MnO/CNC/rGO ternary composite fibers coated with PVA/H₃PO₄ gel electrolyte in parallel and it exhibited an energy density of 0.14 mWh cm^-3 at 4 mW cm^-3 and the maximum power density of 40 mW cm^-3. The fiber supercapacitor also demonstrated a good cycling stability (retains 82% of its initial capacitance after 6000 cycles) and bending robustness. This assembly approach is facile and scalable. More importantly the homogeneous dispersion of the nanoparticles in the ternary composite fibers shows promise for the future spreading of wearable electronic products.

Improved Li-storage performance with PEDOT-decorated MnO2 nanoboxes

In this paper, MnO₂ nanoboxes coated with poly(3,4-ethylenedioxythiophene) film (denoted as MnO₂@PEDOT) are investigated as an anode material in lithium-ion batteries. The MnO₂ nanoboxes are developed through the surface chemical oxidation decomposition of MnCO₃ cubes and the subsequent removal of their remaining cores. PEDOT is coated on the surface of MnO₂ nanoboxes via in situ polymerization of 3,4-ethylenedioxythiophene. The charge-discharge tests demonstrate that this special configuration endows the resulting MnO₂@PEDOT with remarkable electrochemical performances, that is a reversible capacity of 628 mA h g^-1 after 850 cycles at a current density of 1000 mA g^-1 and a rate capacity of 367 mA h g^-1 at 3000 mA g^-1. The results indicate that the nanoboxes provide the paths for Li-ion diffusion, the reaction sites for Li-ion intercalation/deintercalation and the space to buffer the volume change during the charge-discharge process, while the conductive polymer ensures the structural stability and improves the electronic conductive property of MnO₂.