Ultrathin Cellulose Research Articles

Ultrathin separator with efficient ion transport and superior stability prepared from cotton cellulose for advanced supercapacitors

The thickness of separators has a great influence on electrochemical performance and battery safety. However, the solution for the inevitable trade-off between separators thickness and their performance still remains a great challenge. Herein, we report novel strategy for manufacturing ultrathin cellulose membrane as separator for high-performance supercapacitors (SCs) via a low-cost and scalable solution-phase inversion technique. The ultrathin cellulose separator with a thickness of 15 µm possessed excellent physical performances, including higher tensile strength (74.5 MPa) and porosity (66.7%), ensuring safety during assembly and operation of the device. Simultaneously benefiting from the substantial polar hydroxyl groups (–OH) and inter- and intra-molecular hydrogen bonds in the cellulose structure, cellulose separator directly realized better electrolyte affinity, thermal stability, and chemical stability in contrast with commercial separators. The ultrathin construction of the separator shortened ion transport pathways, reduced the internal resistance and increased the ion conductivity, which would facilitate fast ion transport for the practical application of separator. Our methods provided a much-needed strategy for fabrication of ultrathin separators and might promote the development of portable energy storage devices.

An ultrathin nanocellulosic ion redistributor for long-life zinc anode

<p>Metallic zinc (Zn) has garnered extensive research interest as a promising anode candidate for aqueous zinc batteries (AZBs) owing to its high theoretical capacity and low redox potential. However, its practical application is severely plagued by the issue of uncontrolled Zn dendritic growth and short lifetime mainly as a result of nonuniform Zn-ion (Zn<sup>2+</sup>) flux distribution across the Zn anode/electrolyte interface. Herein, we propose a feasible and efficient strategy to homogenize the ion flux by building an ultrathin cellulose nanofiber (U-CNF, thickness of less than 1 ��m) ion redistributor from waste biomass, which shows remarkable talent in addressing the dendrite formation issue without compromising the low-cost and environmentally friendly nature of AZBs. With this interfacial design, exceptional long-cycle-life (over 2500 h at 1 mA cm<sup>?2</sup>), excellent rate capability (low voltage hysteresis of 238 mV at 40 mA cm<sup>?2</sup>), and high reversibility (average Coulombic efficiency of 99.14% over 850 cycles) of Zn plating/stripping performance are synchronously realized. Furthermore, the long-term cyclability and reliability of practical Zn||MnO<sub>2</sub> batteries are also demonstrated with the incorporation of the U-CNF ion redistributor. Considering the simplicity and effectiveness, this proof-of-concept study may imply a promising physical route toward dendrite-free Zn anode for AZBs.</p>

Humidity Response of Cellulose Thin Films.

Cellulose–water interactions are crucial to understand biological processes as well as to develop tailor made cellulose-based products. However, the main challenge to study these interactions is the diversity of natural cellulose fibers and alterations in their supramolecular structure. Here, we study the humidity response of different, well-defined, ultrathin cellulose films as a function of industrially relevant treatments using different techniques. As treatments, drying at elevated temperature, swelling, and swelling followed by drying at elevated temperatures were chosen. The cellulose films were prepared by spin coating a soluble cellulose derivative, trimethylsilyl cellulose, onto solid substrates followed by conversion to cellulose by HCl vapor. For the highest investigated humidity levels (97%), the layer thickness increased by ca. 40% corresponding to the incorporation of 3.6 molecules of water per anhydroglucose unit (AGU), independent of the cellulose source used. The aforementioned treatments affected this ratio significantly with drying being the most notable procedure (2.0 and 2.6 molecules per AGU). The alterations were investigated in real time with X-ray reflectivity and quartz crystal microbalance with dissipation, equipped with a humidity module to obtain information about changes in the thickness, roughness, and electron density of the films and qualitatively confirmed using grazing incidence small angle X-ray scattering measurements using synchrotron irradiation.

Atomization of Microfibrillated Cellulose and Its Incorporation into Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Reactive Extrusion

The present study focuses on the preparation and characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films that were reinforced with cellulose microstructures to obtain new green composite materials for sustainable food packaging applications. The atomization of suspensions of microfibrillated cellulose (MFC) successfully allowed the formation of ultrathin cellulose structures of nearly 3 µm that were, thereafter, melt-mixed at 2.5, 5, and 10 wt % with PHBV and subsequently processed into films by thermo-compression. The most optimal results were attained for the intermediate MFC content of 5 wt %, however, the cellulose microstructures showed a low interfacial adhesion with the biopolyester matrix. Thus, two reactive compatibilizers were explored in order to improve the properties of the green composites, namely the multi-functional epoxy-based styrene-acrylic oligomer (ESAO) and the combination of triglycidyl isocyanurate (TGIC) with dicumyl peroxide (DCP). The chemical, optical, morphological, thermal, mechanical, and barrier properties against water and aroma vapors and oxygen were analyzed in order to determine the potential application of these green composite films in food packaging. The results showed that the incorporation of MFC yielded contact transparent films, whereas the reactive extrusion with TGIC and DCP led to green composites with enhanced thermal stability, mechanical strength and ductility, and barrier performance to aroma vapor and oxygen. In particular, this compatibilized green composite film was thermally stable up to ~280 °C, whereas it showed an elastic modulus (E) of above 3 GPa and a deformation at break (ɛb) of 1.4%. Moreover, compared with neat PHBV, its barrier performance to limonene vapor and oxygen was nearly improved by nine and two times, respectively.

Evaluating the refractive index, thickness and porosity of ultrathin cellulose nanocrystal films with different polymorphs by SPR technique

It is of crucial importance to know the quality of ultrathin films deposited on surface plasmon resonance (SPR) sensors prior to adsorption experiments. In this study, the optical properties of ultrathin cellulose nanocrystal films with various polymorphs (cellulose I, cellulose II and the hybrid of cellulose I/II), which deposited on gold surface of SPR sensors, were determined by a two-medium SPR technique and the influences of the second medium were assessed as well. The measured refractive index for ultrathin cellulose nanocrystal films with polymorphs of cellulose I, I/II and II was 1.453, 1.462 and 1.464, respectively, with a low margin of error about 0.2%. The porosity of according CNC films on SPR sensors was assessed to be 20.8%, 19.0%, and 18.5%. The measured film thickness for all deposited cellulose nanocrystal films was in the range of 25–35 nm, with a margin of error about 5%, accorded well with that examined by quartz crystal microbalance. The results showed that SPR surveys combined with Winspall analysis allow for simultaneous determination of the thickness, refractive index and the derived porosity, and provide a facile in situ quality control for the modified SPR sensors prior to adsorption experiments.

Development of titanium dioxide incorporated ultrathin cellulose acetate membrane for enhanced forward osmosis performance

Development of titanium dioxide incorporated ultrathin cellulose acetate membrane for enhanced forward osmosis performance

Композитные мембраны с поверхностным слоем из ацетата целлюлозы для водоочистки и водоподготовки

Microporous composite membranes containing from one to three ultrathin layers were obtained by multistage immersion of a paper base in a solution of cellulose acetate in acetone. The physicochemical properties of membranes have been studied and the parameters of membrane separation of heavy metal ions from tap water have been determined. An increase in the particle size and a decrease in the absolute value of the ζ-potential with an increase in the concentration of cellulose acetate in acetone were revealed. It was found that the porosity of the membranes increased from 47 % to 51 % depending on the number of ultrathin cellulose acetate layers on the substrate surface. A decrease in the moisture absorption of composite membranes and an increase in the contact angle of wetting with distilled water from 30.0° to 68.8°, depending on the number of ultrathin layers, were noted. Microscopic examination of the membrane surface showed that the ultrathin layer consists of many pores with sizes less than 1 micron. The absorption bands in the IR spectra of cellulose acetate and the surface of the composite microporous cellulose acetate (MAC) membrane are identical. The retention capacity of MAC composite membranes, determined by iron ions from an iron (III) chloride solution, ranged from 47.5 to 97.4 % depending on the number of cellulose acetate layers on the substrate surface with a specific productivity of 27.9 to 7399 dm3/(m2·h) and a pressure of 0.35 MPa. A high selectivity of a microporous membrane of three layers of cellulose acetate (MAC3) with respect to heavy metal ions contained in tap water was established: Cr3+ (96 %) > Cu2+ (92 %) > Fe3+ (90 %) > Mn2+ (45 %).

Nanocellulose-MXene Biomimetic Aerogels with Orientation-Tunable Electromagnetic Interference Shielding Performance.

Designing lightweight nanostructured aerogels for high‐performance electromagnetic interference (EMI) shielding is crucial yet challenging. Ultrathin cellulose nanofibrils (CNFs) are employed for assisting in building ultralow‐density, robust, and highly flexible transition metal carbides and nitrides (MXenes) aerogels with oriented biomimetic cell walls. A significant influence of the angles between oriented cell walls and the incident EM wave electric field direction on the EMI shielding performance is revealed, providing an intriguing microstructure design strategy. MXene “bricks” bonded by CNF “mortars” of the nacre‐like cell walls induce high mechanical strength, electrical conductivity, and interfacial polarization, yielding the resultant MXene/CNF aerogels an ultrahigh EMI shielding performance. The EMI shielding effectiveness (SE) of the aerogels reaches 74.6 or 35.5 dB at a density of merely 8.0 or 1.5 mg cm–3, respectively. The normalized surface specific SE is up to 189 400 dB cm2 g–1, significantly exceeding that of other EMI shielding materials reported so far.

Ultrathin Cellulose Voronoi-Nanonet Membranes Enable High-Flux and Energy-Saving Water Purification.

Creating a desirable porous membrane with high-flux and energy-saving properties for the purification of water containing submicron-sized contaminants, especially pathogenic microbes, is of great significance, yet a great challenge. Herein, we demonstrate a facile methodology to construct an innovative membrane with continuous cellulose Voronoi-nanonet structures via nonsolvent-induced phase separation. This approach enables cellulose Voronoi nanonets to tightly weld with electrospun nanofibrous substrates by controlling the solvent-nonsolvent mutual diffusion process. The resultant membranes exhibit integrated properties of small pore size (0.23 μm), high porosity (90.7%), good interconnectivity, and ultrathin thickness (∼600 nm, 2 orders of magnitude thinner than the conventional microfiltration membrane). As a result, the prepared membranes can effectively intercept submicron particles (∼0.3 μm) with robust rejection efficiency (>99.80%) and ultrahigh permeation flux (maximum of 8834 L m-2 h-1) under an extremely low driving pressure (≤20 kPa). More importantly, prominent bacterial rejection efficiency with a log reduction value (LRV) of 8.0 (overcoming the previous limitation of LRV <7) and outstanding antifouling function are also achieved for the membranes. The successful fabrication of such a versatile membrane may provide new insights into the development of next-generation high-performance separation materials for various applications.

Alignment Effect on the Piezoelectric Properties of Ultrathin Cellulose Nanofiber Films.

This study aims at evaluating the piezoelectric property of an ultrathin cellulose nanofiber (CNF) film in a thickness direction. Cellulose is known to have piezoelectric properties. However, its measurement is not easy. By making an ultrathin CNF film and eliminating space charges, the pure piezoelectric property of CNF is intended to be measured. A 600 nm thick ultrathin CNF film was prepared using a microfabrication process. The effect of alignment methods on the piezoelectric property of the ultrathin CNF film in the thickness direction was investigated with the three alignment methods: corona poling, electrical in-plane alignment, and high magnetic field (HiMA) alignment. Piezoresponse force microscopy (PFM) was utilized to analyze the piezoelectric property. By applying AC voltages using PFM, the vertical displacement on the ultrathin CNF film surface was recorded and converted into the piezoelectric coefficient, d33. The aligned ultrathin CNF films show different piezoelectric coefficients. The corona-poled ultrathin CNF film shows the largest piezoelectric coefficient among the three alignment methods. Water contact angle measurement proves that the piezoelectric constant in the thickness direction is associated with hydroxyl groups in cellulose chains appearing on the surface of the ultrathin CNF films.

Ultra-light cellulose nanofibril membrane for lithium-ion batteries

The development of portable devices and wearable devices leads to the pursuit of lighter and thinner lithium-ion batteries. However, this goal is limited by the battery components, of which the separator is an important part. Here, ultra-light and ultra-thin cellulose nanofibril membranes are prepared using a facile ethanol-soaked process. The weight and thickness of the obtained separators are only half those of conventional polyolefin membranes (Celgard2325), and much smaller than other novel membranes. Equally important, the separators not only have excellent physical properties, but the prepared batteries also have better electrochemical performance than the commercial Celgard2325. This study indicates the alluring prospect of applying cellulose nanofibril membranes into ultra-light-thin lithium-ion batteries.

An Optically Responsive Soft Etalon Based on Ultrathin Cellulose Hydrogels

AbstractStimuli‐responsive optical etalons are an exciting class of next‐generation sensors because they are scalable, cost‐effective and offer tunability of their optical response across the entire UV–vis–NIR wavelength range. In this study, double‐network cellulose hydrogels are used as a soft, responsive medium and are incorporated into Fabry–Pérot optical etalons. The thin cellulose hydrogel layer can be solution processed. The hygroscopic hydrogel undergoes both refractive index and thickness changes in response to changes in humidity. This leads to strong changes in reflection due to optical interference within the metal–insulator–metal (MIM) cavity. The response can be optimized by adjusting the chemical crosslinker ratio. These flexible MIM structures provide a robust platform for optically based chemical sensors.

Versatile Utilizations of Cellulose Nanofibers for High-Performance Silicon Anode in Lithium-Ion Batteries

Silicon is the most anticipated anode material in lithium-ion batteries due to its natural abundancy, low insertion voltage (<0.4 V vs. Li/Li+) and high specific capacity (<3579 mAh g-1). However, huge volume change (~ 300 %) during cycling which causes poor cycling stability and its insulating nature prohibit the practical use. In this research, cellulose nanofibers were utilized in various ways to enhance the performance of silicon nanoparticle anodes. As carbon sources, the ultrathin (~ 1.55 nm) cellulose nanofibers can provide an extensive conductive network to improve both the cycling stability and rate performance by mitigating the volume expansion of silicon and providing the efficient electron path. Furthermore, by using thicker (~ 30 nm) cellulose nanofibers as carbon sources, a porous conductive network can be achieved, which can provide both the efficient electron path and ion diffusion path. In addition, the void space generated by cellulose nanofibers became a buffer space which enhanced the cycling stability. Finally, as a binder additive, cellulose nanofiber can enhance the performance of carboxymethyl cellulose binder. It can act as both a filler and a binder to be utilized in an electrode composite, unlike the traditional reinforcing fillers. Therefore, the versatile, cheap and abundant cellulose nanofibers show great potential in lithium-ion batteries.

Modification of electrospun, ultra-thin cellulose fibres by means of polycarboxylic acid–based cross-linking agents

Ultra-thin fibre assemblies consisting of cellulose were prepared by means of the electrospinning procedure. In this study, cellulose acetate (CA) was dissolved in dimethylacetamide/acetone (2:1 v/v) and electrospun using a high voltage of 10 and 15 kV and a tip to collector distance of 15 cm. The CA fibre mats were deacetylated and chemically modified by means of a 1,2,3,4-butanetetracarboxylic acid (BTCA)/sodium hypophosphite and a BTCA/(3-aminopropyl)triethoxysilane (APTES) solution. After a thermal treatment at 180°C, Fourier Transform infrared/attenuated reflection spectra of the cross-linked fibre mats confirmed the formation of an ester linkage and an imide moiety, respectively. X-ray diffraction spectra made evident the presence of cellulose II. Thermogravimetric analysis indicated a significant increase in the thermal stability of the chemically modified mats. The water vapour transmission is increased for BTCA/APTES fibre mats.

Enhancement of separation performance of asymmetric cellulose acetate membrane for produced water treatment using response surface methodology

Produced water is the wastewater generated from the process of exploration in oil and gas production, which needs special treatment. A membrane with cellulose acetate is widely used for produced water treatment, but further developments and improvements are still required. Therefore, it is important to determine the factors of separation efficiency of an ultrathin cellulose acetate membrane by assessing the influence of the composition of the dope solution. The response surface methodology was employed to determine the optimal conditions for this application. The investigations were conducted by varying the cellulose acetate polymer concentration at 18-20 wt.%, polyethylene glycol 4000 at 2-3 wt.% and nonsolvent addition at 3-5 wt.%. The evaluation of membrane performance for the produced water treatment was performed in a dead-end filtration cell with permeate water flux and rejection parameters for turbidity, total dissolved solids, Ca2+, Mg2+ and sulfides of produced water upstream and downstream of the membrane. The optimal composition of the dope solution was: 19 wt.% of cellulose acetate, 3 wt.% of polyethylene glycol, and 5.67 wt.% of non-solvent.

Sustainable Route for Molecularly Thin Cellulose Nanoribbons and Derived Nitrogen-Doped Carbon Electrocatalysts

Ultrathin cellulose nanoribbons were extracted from earth-abundant biomass using 2,2,6,6-tetramethylpiperidine-1-oxyl-catalyzed (TEMPO-catalyzed) oxidation and sonication processes. By two TEMPO-oxide systems with different processing times, TEM and AFM observations indicate the obtained cellulose nanoribbons (Cel-NRs) with dimensions of 400–800 nm in length, 1.72–2.54 nm in width, and 0.78–2.67 nm in thickness. The dimension data indicate that the Cel-NRs from the TEMPO/NaBr/NaClO system are much shorter but contain more cellulose chains than those from the TEMPO/NaClO/NaClO2 system. Moreover, these abundant biomass nanoribbons were fabricated from direct pyrolysis with NH3 activation. The obtained highly active nitrogen-doped carbon nanoribbons (N-CNRs) and metal-free oxygen reduction reaction (ORR) electrocatalysts show superb ORR activity (half-wave potential of 0.71 and 0.73 V versus reversible hydrogen electrode) and high selectivity (electron-transfer number of 3.26 and 3.74 at 0.8 V), comparable c...

Deposition of Ultrathin Cellulose Nanofibers Films As Bio-Implant Corrosion Coatings

The wide use of magnesium and magnesium-based alloys for bio-implant materials has so far been restricted due to the rapid corrosion rate of such materials under in-vivo conditions 1,2. Cellulose based coatings have previously been examined as coatings for magnesium materials although the use of TEMPO-oxidised nano-fibrillated cellulose (CNF-TEMPO) coatings has yet to be explored 3,4. The work outlines details of an investigation in to the effect that deposition method has on the coating characteristics. Three different methods were used to deposit CNF-TEMPO coatings including adsorption, spin coating and anodic electrophoretic deposition. The coatings were subsequent analysed using atomic force microscopy (AFM), ellipsometry and quartz crystal microbalance (QCM) to determine differences in nanotopographic surface roughness and hydrophilicity in particular. The ability of the EPD technique to deposit films from relative dilute solutions (0.01 to 0.1 wt-%) was demonstrated. Finally, samples of magnesium were coated and the corrosion properties of the ultrathin films were determined using a number of electrochemical techniques including linear sweep voltammetry, polarization and free corrosion measurements. Overall, the results show that CNF-TEMPO coatings produced using the EPD method offer a potential starting point for the next generation of biobased coatings for implant materials.

Extensively interconnected silicon nanoparticles via carbon network derived from ultrathin cellulose nanofibers as high performance lithium ion battery anodes

Silicon is a good alternative to conventional graphite anode but it has bad cycling and rate performance. To overcome these severe problems, extensively interconnected silicon nanoparticles using carbon network derived from ultrathin cellulose nanofibers were synthesized. Ultrathin cellulose nanofibers, an abundant and sustainable material, entangle each silicon nanoparticle and become extensively interconnected carbon network after pyrolysis. This wide range interconnection provides an efficient electron path by decreasing the likelihood that electrons experience contact resistivity and also suppresses the volume expansion of silicon during lithiation. In addition, Ultrathin cellulose nanofibers are carboxylated and therefore adhesive to silicon nanoparticles through hydrogen bonding. This property makes ultrathin cellulose the perfect carbon source when making silicon composites. As a consequence, it exhibits 808 mAh g−1 of the reversible capacity after 500 cycles at high current density of 2 A g−1 with a coulombic efficiency of 99.8%. Even at high current density of 8 A g−1, it shows a high reversible discharge capacity of 464 mAh g−1. Moreover, extensively interconnected carbon network prevents the formation of a brittle electrode with a water-based binder. Therefore, this remarkable material has a huge potential for LIBs applications.

Charge‐ and Size‐Selective Molecular Separation using Ultrathin Cellulose Membranes

AbstractInvited for this month′s cover are Klaus‐V. Peinemann and his co‐workers at the King Abdullah University of Science and Technology (KAUST). The image shows the separation performance of a 10 nm thin cellulose membrane. The Communication itself is available at 10.1002/cssc.201600791.

Charge- and Size-Selective Molecular Separation using Ultrathin Cellulose Membranes.

To date, it is still a challenge to prepare high-flux and highselectivity microporous membranes thinner than 20 nm without introducing defects. In this work, we report for the first time the application of cellulose membranes for selective separation of small molecules. A freestanding cellulose membrane as thin as 10 nm has been prepared through regeneration of trimethylsilyl cellulose (TMSC). The freestanding membrane can be transferred to any desired substrate and shows a normalized flux as high as 700 L m-2 h-1 bar-1 when supported by a porous alumina disc. According to filtration experiments, the membrane exhibits precise size-sieving performances with an estimated pore size between 1.5-3.5 nm depending on the regeneration period and initial TMSC concentration. A perfect discrimination of anionic molecules over neutral species is demonstrated. Moreover, the membrane demonstrates high reproducibility, high scale-up potential, and excellent stability over two months.