With increasing environmental and ecological concerns due to the use of petroleum-based chemicals and products, the synthesis of fine chemicals and functional materials from natural resources is of great public value. Nanocellulose may prove to be one of the most promising green materials of modern times due to its intrinsic properties, renewability, and abundance. In this review, we present nanocellulose-based materials from sourcing, synthesis, and surface modification of nanocellulose, to materials formation and applications. Nanocellulose can be sourced from biomass, plants, or bacteria, relying on fairly simple, scalable, and efficient isolation techniques. Mechanical, chemical, and enzymatic treatments, or a combination of these, can be used to extract nanocellulose from natural sources. The properties of nanocellulose are dependent on the source, the isolation technique, and potential subsequent surface transformations. Nanocellulose surface modification techniques are typically used to introduce e...

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Nanocellulose, a Versatile Green Platform: From Biosources to Materials and Their Applications

Nanocellulose, a tiny fiber with huge applications

Ionic liquid with acidic properties is an important branch in the wide ionic liquid field and the aim of this article is to cover all aspects of these acidic ionic liquids, especially focusing on the developments in the last four years. The structural diversity and synthesis of acidic ionic liquids are discussed in the introduction sections of this review. In addition, an unambiguous classification system for various types of acidic ionic liquids is presented in the introduction. The physical properties including acidity, thermo-physical properties, ionic conductivity, spectroscopy, and computational studies on acidic ionic liquids are covered in the next sections. The final section provides a comprehensive review on applications of acidic ionic liquids in a wide array of fields including catalysis, CO2 fixation, ionogel, electrolyte, fuel-cell, membrane, biomass processing, biodiesel synthesis, desulfurization of gasoline/diesel, metal processing, and metal electrodeposition.

Acidic Ionic Liquids.

Lightweight conductive porous graphene/thermoplastic polyurethane (TPU) foams with ultrahigh compressibility were successfully fabricated by using the thermal induced phase separation (TISP) technique. The density and porosity of the foams were calculated to be about 0.11 g cm−3 and 90% owing to the porous structure. Compared with pure TPU foams, the addition of graphene could effectively increase the thickness of the cell wall and hinder the formation of small holes, leading to a robust porous structure with excellent compression property. Meanwhile, the cell walls with small holes and a dendritic structure were observed due to the flexibility of graphene, endowing the foam with special positive piezoresistive behaviors and peculiar response patterns with a deflection point during the cyclic compression. This could effectively enhance the identifiability of external compression strain when used as piezoresistive sensors. In addition, larger compression sensitivity was achieved at a higher compression rate. Due to high porosity and good elasticity of TPU, the conductive foams demonstrated good compressibility and stable piezoresistive sensing signals at a strain of up to 90%. During the cyclic piezoresistive sensing test under different compression strains, the conductive foam exhibited good recoverability and reproducibility after the stabilization of cyclic loading. All these suggest that the fabricated conductive foam possesses great potential to be used as lightweight, flexible, highly sensitive, and stable piezoresistive sensors.

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Lightweight conductive graphene/thermoplastic polyurethane foams with ultrahigh compressibility for piezoresistive sensing

The rapid development of wearable smart devices has contributed to the enormous demands for smart flexible strain sensors. However, to date, the poor stretchability and sensitivity of conventional metals or inorganic semiconductor-based strain sensors have restricted their application in this field to some extent, and hence many efforts have been devoted to find suitable candidates to overcome these limitations. Recently, novel resistive-type electrically conductive polymer composites (ECPCs)-based strain sensors have attracted attention based on their merits of light weight, flexibility, stretchability, and easy processing, thus showing great potential applications in the fields of human movement detection, artificial muscles, human–machine interfaces, soft robotic skin, etc. For ECPCs-based strain sensors, the conductive filler type and the phase morphology design have important influences on the sensing property. Meanwhile, to achieve a successful application toward wearable devices, several imperative features, including a self-healing capability, superhydrophobicity, and good light transmission, need to be considered. The aim of the present review is to critically review the progress of ECPCs-based strain sensors and to foresee their future development.

Electrically conductive polymer composites for smart flexible strain sensors: a critical review

Deposition of precious metal catalysts onto the surface of various supporting materials to enhance the stability and catalytic activity is highly desired. Although extensive studies have been focused on the supported metal catalysts, their preparations are mainly based on the use of reducing agents which are not environmentally benign. Herein, we report a one-pot and green synthesis of gold nanoparticles (Au NPs) deposited on cellulose nanocrystals (CNs) under hydrothermal conditions using CNs as a reducing agent and stabilizing template. Our experimental results showed that the abundant electron-rich hydroxyl groups on the surface of CNs played a key role in the reduction and immobilization of Au NPs. The obtained nanohybrid catalyst exhibited much better catalytic activity and stability than the unsupported Au NPs and other Au-containing catalysts for the reduction of 4-nitrophenol. These findings pave the way for the green synthesis of bio-supported nanohybrid catalysts and can spur advancements in nanocellulose-based nanohybrids for their application in sensors, antibacterial materials and electronic devices.

Green synthesis and formation mechanism of cellulose nanocrystal-supported gold nanoparticles with enhanced catalytic performance

We report a one step and environment-friendly synthesis of cellulose nanocrystal (CN)-supported palladium nanoparticles (Pd NPs) without employing any other reductants, capping or dispersing agents. CNs played a dual role as a supporting matrix and a reductant and they were used to obtain stable dispersions of Pd NPs. The obtained hybrid material exhibited much higher activities than the unsupported and other polymer-supported Pd NPs in the catalyzed reduction of methylene blue and 4-nitrophenol. The approach presented in this paper promotes the use of renewable natural resources to prepare a variety of hybrid inorganic–organic materials for the purpose of catalysis, sensors, and other potential applications.

A novel reagentless approach for synthesizing cellulose nanocrystal-supported palladium nanoparticles with enhanced catalytic performance

Cellulose nanowhisker modulated 3D hierarchical conductive structure of carbon black/natural rubber nanocomposites for liquid and strain sensing application

Cellulose aerogel has attracted considerable attention due to its high surface area and the added advantages of being cost-effective and environmentally benign. It has been applied as supporting material for noble metal nanoparticle catalysts to prevent their agglomeration. In this paper, we have demonstrated a facile method to prepare polyaniline (PANI)-decorated cellulose aerogel via a dissolve/regeneration route using ionic liquid as solvent. Cellulose aerogel acted as a supporting material for PANI nanoparticles to prevent their agglomeration as confirmed by scanning electron microscopy. The strong interfacial interaction between PANI and cellulose aerogel was verified by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal gravimetric analysis and X-ray diffraction. PANI-cellulose aerogel exhibited excellent photocatalytic activity towards the degradation of methylene blue. The degradation efficiency reached 95% after 2 h. The approach promotes the use of renewable natural resources to prepare a variety of nanofibrillated cellulose-supported nanocomposites for catalysis, sensors, and other potential applications.

Guiping Yuan

Papers

Green synthesis and formation mechanism of cellulose nanocrystal-supported gold nanoparticles with enhanced catalytic performance

A novel reagentless approach for synthesizing cellulose nanocrystal-supported palladium nanoparticles with enhanced catalytic performance

Cellulose nanowhisker modulated 3D hierarchical conductive structure of carbon black/natural rubber nanocomposites for liquid and strain sensing application

Polyaniline-decorated cellulose aerogel nanocomposite with strong interfacial adhesion and enhanced photocatalytic activity

Water-soluble cellulose acetate from waste cotton fabrics and the aqueous processing of all-cellulose composites.