Advances in regenerated cellulosic aerogel from waste cotton textile for emerging multidimensional applications

Rapid development of society and the improvement of people's living standards have stimulated people's keen interest in fashion clothing. This trend has led to the acceleration of new product innovation and the shortening of the lifespan for cotton fabrics, which has resulting in the accumulation of waste cotton textiles. Although cotton fibers can be degraded naturally, direct disposal not only causes a serious resource waste, but also brings serious environmental problems. Hence, it is significant to explore a cleaner and greener waste textile treatment method in the context of green and sustainable development. To realize the high-value utilization of cellulose II aerogel derived from waste cotton products, great efforts have been made and considerable progress has been achieved in the past few decades. However, few reviews systematically summarize the research progress and future challenges of preparing high-value-added regenerated cellulose aerogels via dissolving cotton and other cellulose wastes. Therefore, this article reviews the regenerated cellulose aerogels obtained through solvent methods, summarizes their structure, preparation strategies and application, aimed to promote the development of the waste textile industry and contributed to the realization of carbon neutrality.

All-cellulose air filter composed with regenerated nanocellulose prepared through a facile method with shear-induced

High-speed shear system is usually used for the dispersion improvement of slurry, nanomaterials preparation, and even two-dimensional materials production. However, there is barely study that focused on the regenerated cellulose (RC) which was coagulated with shear induced. In this work, a new type of all-cellulose air filter was fabricated through high-speed shear in aqueous regeneration system using parenchyma cellulose from corn stalk. The obtained RC were aggregated by ribbon-like fine cellulose and nanocellulose sheets. The study exhibited the micro-structure of RC displayed excellent unidirectional alignment and a relatively high crystallinity. All-cellulose air filter which was produced via RC presented excellent filtration efficiency (PM_2.5 97.3 %, PM_10.0 97.7 %) with slightly pressure drop (19 Pa). Therefore, this work provides a facile method to obtain a novel RC with nanocellulose particles used for air filtration, which gives an effective strategy application in the conversion of all-cellulose materials from agricultural waste.

Eco-Friendly and Complete Recycling of Waste Bamboo-Based Disposable Paper Cups for Value-Added Transparent Cellulose-Based Films and Paper Plastic Composites

Disposable paper cups are widely used in daily life and most of them are landfilled or incinerated after use, resulting in a serious ecological hazard and significant waste of resources due to the usage of thin polyethylene (PE) as their inner coating. Hence, converting these common solid domestic wastes into high-value added materials is attractive and meaningful. In this study, transparent cellulose-based films were achieved from old bamboo-based disposable paper cups after pretreatment through using the room ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as solvent. The cellulose-based film with a dense texture demonstrated a relatively nice mechanical and UV-shielding performances, and its tensile strength was as high as 48 MPa, much higher than that of commercial polyethylene (PE, 12 MPa) film. Thus, the resultant cellulose-based film showed a great potential in the packaging field. Besides, the flexible paper plastic composites (PPC) were also fabricated from the rest thin PE coating with the stuck fibers, and it was found that PPC showed excellent mechanical property and hydrophobicity. Consequently, a feasible and eco-friendly process of recycling and reusing waste disposable paper cups was developed to achieve a complete utilization and valorization of waste disposable paper cups.

Fabrication and Characterization of Transparent and Uniform Cellulose/Polyethylene Composite Films from Used Disposable Paper Cups by the "One-Pot Method"

Disposable paper cups are usually composed of high-grade paper board and an inner polyethylene coatings and are extensively used in daily life. However, most disposable paper cups are only used for a short time and then incinerated or accumulated in landfill at the end of their service due to the difficulty in separating the components, leading to a serious threat to our ecosystem. Therefore, developing a facile and green method to recycle and reuse disposable paper cups is vital. By using ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as a solvent, transparent and homogenous cellulose/polyethylene composite films were successfully prepared from used bamboo-based disposable paper cups through the "one-pot method", without any pre-treatment. It was found that there was a transformation of cellulose I to II after the dissolution and regeneration processes, and the crystallinity degree of the regenerated cellulose-based materials decreased significantly, resulting in a change in thermal properties. Meanwhile, compared to traditional pure cellulose films, the composite films possessed good UV-shielding properties and hydrophobicity. Moreover, they also displayed good mechanical properties. Additionally, the size of the ground PE coatings displayed obvious effects on the structures and properties of the composite films, where the CPE100 (sieved with 100-200 mesh) possessed the most homogeneous texture and the highest tensile strength (82 Mpa), higher than that of commercial polyethylene film (9-12 MPa), showing superiority as packaging or wrapping materials. Consequently, the goals to fabricate uniform cellulose/polyethylene composite films and valorize the solid waste from disposable paper cups were simultaneously achieved by a facile and green "one-pot method".

Room temperature preparation of cellulose nanocrystals with high yield via a new ZnCl2 solvent system

Here, a facile method to fabricate cellulose nanocrystals (CNCs) with high yield from microcrystalline cellulose (MCC) at room temperature (RT) is achieved by using a new solvent system of zinc chloride (ZnCl₂) and a little amount of hydrochloric acid (HCl). Compared with sulphuric acid hydrolysis process, about one-fifth mole of acid is used for per gram of CNCs in our protocol. CNCs with rod-like morphology are regenerated with a maximum yield of 35.2% and high crystallinity of 73.8%. Moreover, with an additional 2 h of ball-milling, the yield of CNCs could significantly increase to 66.9% at RT. The possible formation mechanism for CNCs prepared by the solvent system of ZnCl₂/HCl is proposed. As the first example of isolation of CNCs with high yield at RT using ZnCl₂, this work provides a facile, energy-saving, and practical strategy for the preparation of cellulose nanomaterials.

Cellulose Amphiphilic Materials: Chemistry, Process and Applications

In the last decade, amphiphilic cellulose (AC) is emerging as attractive biomaterial for different therapeutic use, due to its unique chemical and physical properties. Using it as alternative to synthetic polymers, AC opens up new avenues to prepare new bio-sustainable materials with low impact in the cellular environment. Herein, most recent methods to synthesize and processing AC materials from different sources—i.e., cellulose nanofibers, bacterial cellulose, cellulose derivatives—will be discussed. By an accurate optimization of morphology and surface chemistry, it is possible to develop innovative amphiphilic platforms, promising for a wide range of biomedical applications, from drug delivery to molecular/particle adsorption.

Transparent cellulose/aramid nanofibers films with improved mechanical and ultraviolet shielding performance from waste cotton textiles by in-situ fabrication

Cellulose films with biodegradability and intrinsically antistatic property have many applications. However, conventional cellulose films show poor toughness and UV-shielding property, and the major sources are high-grade cotton linter or wood pulp. Herein, by using low-cost waste cotton textiles as the raw materials, we successfully fabricated transparent cellulose/aramid nanofibers (ANFs) films, in which in-situ retained ANFs had a diameter of 20-30 nm and a length of several micrometers. Because ANFs and cellulose chains formed strong hydrogen bonding interactions, the tensile strength and elongation of the resultant cellulose/ANFs film with 1.0 wt% ANFs could reach 54.4 MPa and 15.8%, respectively, increased by 63.4% and 154% compared to those of pure cellulose film (33.3 MPa and 6.2%). Meanwhile, the cellulose/ANFs films show excellent UV-shielding properties and irradiation stability. Hence, the novel cellulose/ANFs films with improved mechanical and UV-shielding performance were in-situ prepared leading to enhance the valorization of waste cotton textiles.

Transparent Cellulose-Based Films Prepared from Used Disposable Paper Cups via an Ionic Liquid

Paper cups are widely employed in daily life with many advantages, but most of the used paper cups are incinerated or landfilled, due to the great challenge of separating the thin inner polyethylene (PE) coating, causing the waste of energy and the pollution of our environment. Therefore, recycling and converting the used paper cups into high-value materials is meaningful and important. In this work, transparent cellulose-based films were successfully prepared from the used paper cups via 1-allyl-3-methylimidazolium chloride ionic liquid after simple pretreatment. Additionally, the difference in properties and structures of cellulose-based films regenerated in different coagulation baths (water or ethanol) was also explored. It was found that the cellulose-based film possessed good thermal property and displayed better hydrophobicity than the traditional pure cellulose film. Moreover, they also demonstrated good mechanical property and the tensile strength of cellulose-based film regenerated in water can reach 31.5 Mpa, higher than those of cellulose-based film regenerated in ethanol (25.5 Mpa) and non-degradable polyethylene film (9-12 MPa), indicating their great potential as the packaging materials. Consequently, valorization of the low cost used paper cups and preparation of high-valve cellulose-based films were realized simultaneously by a facile and green process.

Cellulose-Based Films with Ultraviolet Shielding Performance Prepared Directly from Waste Corrugated Pulp

As the most important paper packaging materials, corrugated cartons with a tremendous amount of production demonstrate several advantages and have been widely used in daily life. However, waste corrugated cartons (WCCs) are usually recycled and reused to produce new corrugated cartons, and their properties are decreased dramatically after several cycles. Therefore, recycling and converting WCCs into cellulose-based film with high value is attractive and significant. Herein, without any pretreatment, the waste old corrugated cartons were directly dissolved in ionic liquid 1-allyl-3-methylimidazolium chloride, and semitransparent cellulose-based films were successfully fabricated. It was indicated that cellulose-based films displayed better UV-shielding property and hydrophobicity than traditional cellulose films. Interestingly, the cellulose-based films regenerated from deionized water displayed higher tensile strength, elongation at break, and toughness. Their tensile strength could reach 23.16 MPa, exhibiting enormous superiority as wrapping and packaging materials to replace the petrochemical polyethylene membrane (8.95 MPa). Consequently, these renewable, biodegradable, and high-valued cellulose-based films were successfully fabricated to simultaneously realize the valorization of old corrugated cartons and supplement the petrochemical plastics.

A novel method to prepare chemical fibers by plasticizing cotton with 1-allyl-3-methylimidazolium chloride

In this study, we developed a novel method to prepare chemical fibers by plasticizing cotton with 1-allyl-3-methylimidazolium chloride (AMIMCl) under high temperature and pressure. Cotton was homogeneously mixed with AMIMCl by kneading in a certain mass proportion. It would be a sheet after hot-pressing and this process could be repeated several times. The morphologies of chemical fibers showed that cotton was successfully plasticized by AMIMCl with the crystallinity of the chemical fibers increased by about 15%. Differential scanning calorimetry (DSC) showed that the glass transition temperature (T_g) occurred in chemical fibers and we could further verify cotton was plasticized by AMIMCl. This simple and green method will be helpful to modify and broaden the application field of cotton.

Direct Visualization of Crystalline Domains in Carboxylated Nanocellulose Fibers

Direct visualization of soft organic molecules like cellulose is extremely challenging under a high-energy electron beam. Herein, we adopt two ionization damage extenuation strategies to visualize the lattice arrangements of the β-(1→4)-d-glucan chains in carboxylated nanocellulose fibers (C-NCFs) having cellulose II crystalline phase using high-resolution transmission electron microscopy. Direct imaging of individual nanocellulose fibrils with high-resolution and least damage under high-energy electron beam is achieved by employing reduced graphene oxide, a conducting material with high electron transmittance and Ag⁺ ions, with high electron density, eliminating the use of sample-specific, toxic staining agents, or other advanced add-on techniques. Furthermore, the imaging of cellulose lattices in a C-NCF/TiO₂ nanohybrid system is accomplished in the presence of Ag⁺ ions in a medium revealing the mode of association of C-NCFs in the system, which validates the feasibility of the presented strategy. The methods adopted here can provide further understanding of the fine structures of carboxylated nanocellulose fibrils for studying their structure-property relationship for various applications.

Electron microscopy using ionic liquids for life and materials sciences

An ionic liquid (IL) is a salt consisting of only cations and anions, which exists in the liquid state at room temperature. Interestingly ILs combine various favorable physicochemical properties, such as negligible vapor pressure, flame resistance, relatively high ionic conductivity, wide electrochemical window, etc. To take advantage of two specific features of ILs, viz. their nonvolatile and antistatic nature, in 2006, Kuwabata, Torimoto et al. reported a milestone study led to current IL-based electron microscopy techniques. Thereafter, several IL-based electron microscopy techniques have been proposed for life science and materials science applications, e.g. pretreatment of hydrous and/or non-electron conductive specimens and in situ/operando observation of chemical reactions occurring in ILs. In this review, the fundamental approaches for making full use of these techniques and their impact on science and technology are introduced.

Isolation and characterization of microcrystalline cellulose from date seeds (Phoenix dactylifera L.)

This article reports the isolation and characterization of microcrystalline cellulose from date seeds of the date palm tree. The raw ground date seeds (RG-DS) are composed of cellulose matrix wrapped by lignin and hemicellulose as amorphous components. Cellulose was isolated from RG-DS through the following sequence: dewaxing, delignification/(bleaching) and acid hydrolysis. FTIR and Raman analysis for the bleached date seeds (B-DS) revealed the successful removal of the amorphous components from the polymer matrix. The X-ray diffractogram of the obtained (B-DS) exhibited the characteristic peaks of native cellulose (type I), with a crystallinity index (CrI = 62%). An additional acid hydrolysis step was used to convert native cellulose into microcrystalline cellulose (MCC-DS) with higher crystallinity (CrI = 70%). SEM analysis showed that the obtained microcrystals exhibit agglomerated and irregular elongated or semi-spherical shaped morphology. TEM analysis confirmed the semicrystalline nature of the MCC-DS. Thermal analysis showed enhanced thermal stability of MCC-DS. The current study shows the feasibility of using date seeds as a low-price source for obtaining MCC which is envisaged for applications in pharmaceutical and food industries as well as for preparing bionanocomposites with enhanced thermal properties.

Preparation and Performance of Different Modified Ramie Fabrics Reinforced Anionic Polyamide-6 Composites

Anionic polyamide-6 (APA-6) composites are prepared by the VARIM process using different modified ramie fabrics to study the structure and properties of different composites. This study can not only evaluate the optimal modification method for the ramie fabrics, but also further explore the interface interaction mechanism between ramie fabrics and APA-6. In this article, the ramie fabrics are modified by a pretreatment, coupling agent and alkali modification. Different modification methods have different effects on the structure, surface properties and mechanical properties of ramie fabrics, which will further affect the impregnation process, interfacial and mechanical properties of the composites. Through the performance analysis of different modified ramie fabrics reinforced APA-6 composites, the conversion, crystallinity and molecular weight of these composites are at a high level, which indicate that the polymerization of these composites is well controlled. The coupling agent modified ramie fabrics composites and the pretreated ramie fabrics composites have higher flexural modulus, tensile strength and dynamic mechanical properties. Alkali-modified ramie fabrics composites have slightly lower mechanical properties, which however have the highest interlaminar shear strength and outperformed interface properties of the composites.

Nanoscale electromechanical properties of template-assisted hierarchical self-assembled cellulose nanofibers

Cellulose, a major constituent of our natural environment and a structured biodegradable biopolymer, has been shown to exhibit shear piezoelectricity with potential applications in energy harvesters, biomedical sensors, electro-active displays and actuators. In this regard, a high-aspect ratio nanofiber geometry is particularly attractive as flexing or bending will likely produce a larger piezoelectric response as compared to axial deformation in this material. Here we report self-assembled cellulose nanofibers (SA-CNFs) fabricated using a template-wetting process, whereby parent cellulose nanocrystals (CNCs) introduced into a nanoporous template assemble to form rod-like cellulose clusters, which then assemble into SA-CNFs. Annealed SA-CNFs were found to exhibit an anisotropic shear piezoelectric response as directly measured using non-destructive piezo-response force microscopy (ND-PFM). We interpret these results in light of the distinct hierarchical structure in our template-grown SA-CNFs as revealed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM).

Towards a molecular understanding of cellulose dissolution in ionic liquids: anion/cation effect, synergistic mechanism and physicochemical aspects

Cellulose is one of the most abundant bio-renewable materials on the earth and its conversion to biofuels provides an appealing way to satisfy the increasing global energy demand. However, before carrying out the process of enzymolysis to glucose or polysaccharides, cellulose needs to be pretreated to overcome its recalcitrance. In recent years, a variety of ionic liquids (ILs) have been found to be effective solvents for cellulose, providing a new, feasible pretreatment strategy. A lot of experimental and computational studies have been carried out to investigate the dissolution mechanism. However, many details are not fully understood, which highlights the necessity to overview the current knowledge of cellulose dissolution and identify the research trend in the future. This perspective summarizes the mechanistic studies and microscopic insights of cellulose dissolution in ILs. Recent investigations of the synergistic effect of cations/anions and the distinctive structural changes of cellulose microfibril in ILs are also reviewed. Besides, understanding the factors controlling the dissolution process, such as the structure of anions/cations, viscosity of ILs, pretreatment temperature, heating rate, etc., has been discussed from a structural and physicochemical viewpoint. At the end, the existing problems are discussed and future prospects are given. We hope this article would be helpful for deeper understanding of the cellulose dissolution process in ILs and the rational design of more efficient and recyclable ILs.

Acidic ionic liquid based UiO-67 type MOFs: a stable and efficient heterogeneous catalyst for esterification

Acidic ionic liquid groups were introduced into the frameworks successfully and the resulting materials showed excellent activity.

Through a Window, Brightly: A Review of Selected Nanofabricated Thin-Film Platforms for Spectroscopy, Imaging, and Detection

We present a review of the use of selected nanofabricated thin films to deliver a host of capabilities and insights spanning bioanalytical and biophysical chemistry, materials science, and fundamental molecular-level research. We discuss approaches where thin films have been vital, enabling experimental studies using a variety of optical spectroscopies across the visible and infrared spectral range, electron microscopies, and related techniques such as electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and single molecule sensing. We anchor this broad discussion by highlighting two particularly exciting exemplars: a thin-walled nanofluidic sample cell concept that has advanced the discovery horizons of ultrafast spectroscopy and of electron microscopy investigations of in-liquid samples; and a unique class of thin-film-based nanofluidic devices, designed around a nanopore, with expansive prospects for single molecule sensing. Free-standing, low-stress silicon nitride membranes are a canonical structural element for these applications, and we elucidate the fabrication and resulting features-including mechanical stability, optical properties, X-ray and electron scattering properties, and chemical nature-of this material in this format. We also outline design and performance principles and include a discussion of underlying material preparations and properties suitable for understanding the use of alternative thin-film materials such as graphene.

Silicon Nitride Thin Films for Nanofluidic Device Fabrication

Silicon nitride is a ubiquitous and well-established nanofabrication material with a host of favourable properties for creating nanofluidic devices with a range of compelling designs that offer extraordinary discovery potential. Nanochannels formed between two thin silicon nitride windows can open up vistas for exploration by freeing transmission electron microscopy to interrogate static structures and structural dynamics in liquid-based samples. Nanopores present a strikingly different architecture—nanofluidic channels through a silicon nitride membrane—and are one of the most promising tools to emerge in biophysics and bioanalysis, offering outstanding capabilities for single molecule sensing. The constrained environments in such nanofluidic devices make surface chemistry a vital design and performance consideration. Silicon nitride has a rich and complex surface chemistry that, while too often formidable, can be tamed with new, robust surface functionalization approaches. We will explore how a simple structural element—a ∼100 nm-thick silicon nitride window—can be used to fabricate devices to wrest unprecedented insights from the nanoscale world. We will detail the intricacies of native silicon nitride surface chemistry, present surface chemical modification routes that leverage the richness of available surface moieties, and examine the effect of engineered chemical surface functionality on nanofluidic device character and performance.

Cellulose amorphization by swelling in ionic liquid/water mixtures: a combined macroscopic and second-harmonic microscopy study

Amorphization of cellulose by swelling in ionic liquid (IL)/water mixtures at room temperature is a suitable alternative to the dissolution-precipitation pretreatment known to facilitate enzymatic digestion. When soaking microcrystalline cellulose in the IL 1-ethyl-3-methylimidazolium acetate containing 20 wt % water, the crystallinity of the cellulose sample is strongly reduced. As less than 4 % of the cellulose dissolves in this mixture, this swelling method makes a precipitation step and subsequent energy-intensive IL purification redundant. Second-harmonic generation (SHG) microscopy is used as a structure-sensitive technique for in situ monitoring of the changes in cellulose crystallinity. Combined optical and SHG observations confirm that in the pure IL complete dissolution takes place, while swelling without dissolution in the optimal IL/water mixture yields a solid cellulose with a significantly reduced crystallinity in a single step.

Effect of cellulose solubility on the thermal and mechanical properties of regenerated cellulose/graphene nanocomposites based on ionic liquid 1-allyl-3-methylimidazoliun chloride

A small amount of IRGO sheets can largely decelerate the dissolution of cellulose in AmimCl, and the mechanical properties of the regenerated cellulose/graphene nanocomposites materials can be tuned by the dissolution time.

Polarization transfer solid-state NMR: a new method for studying cellulose dissolution

Detailed molecular-level information on dissolved and solid cellulose in aqueous dissolution media with ionic liquids by polarization transfer solid-state NMR.