scholarly journals A nanofluidic ion regulation membrane with aligned cellulose nanofibers

2019 ◽  
Vol 5 (2) ◽  
pp. eaau4238 ◽  
Author(s):  
Tian Li ◽  
Sylvia Xin Li ◽  
Weiqing Kong ◽  
Chaoji Chen ◽  
Emily Hitz ◽  
...  
Keyword(s):  
Surface Charge ◽  
Structural Engineering ◽  
Cellulose Nanofibers ◽  
Ion Regulation ◽  
One Dimensional ◽  
Environmentally Responsible ◽  
Massive Scale ◽  
Stable Performance ◽  
Transport Region ◽  
20 Nm

The advancement of nanofluidic applications will require the identification of materials with high-conductivity nanoscale channels that can be readily obtained at massive scale. Inspired by the transpiration in mesostructured trees, we report a nanofluidic membrane consisting of densely packed cellulose nanofibers directly derived from wood. Numerous nanochannels are produced among an expansive array of one-dimensional cellulose nanofibers. The abundant functional groups of cellulose enable facile tuning of the surface charge density via chemical modification. The nanofiber-nanofiber spacing can also be tuned from ~2 to ~20 nm by structural engineering. The surface-charge-governed ionic transport region shows a high ionic conductivity plateau of ~2 mS cm−1 (up to 10 mM). The nanofluidic membrane also exhibits excellent mechanical flexibility, demonstrating stable performance even when the membrane is folded 150°. Combining the inherent advantages of cellulose, this novel class of membrane offers an environmentally responsible strategy for flexible and printable nanofluidic applications.

On the theory of electrohydrodynamically driven capillary jets

1997 ◽  
Vol 335 ◽  
pp. 165-188 ◽  
Author(s):  
ALFONSO M. GAÑÁN-CALVO
Keyword(s):  
Surface Charge ◽  
Electric Fields ◽  
Gas Flow ◽  
Wave Speed ◽  
Propagation Speed ◽  
Field Equations ◽  
Steady Regime ◽  
One Dimensional ◽  
Relaxation Effects ◽  
Capillary Jets

Electrohydrodynamically (EHD) driven capillary jets are analysed in this work in the parametrical limit of negligible charge relaxation effects, i.e. when the electric relaxation time of the liquid is small compared to the hydrodynamic times. This regime can be found in the electrospraying of liquids when Taylor's charged capillary jets are formed in a steady regime. A quasi-one-dimensional EHD model comprising temporal balance equations of mass, momentum, charge, the capillary balance across the surface, and the inner and outer electric fields equations is presented. The steady forms of the temporal equations take into account surface charge convection as well as Ohmic bulk conduction, inner and outer electric field equations, momentum and pressure balances. Other existing models are also compared. The propagation speed of surface disturbances is obtained using classical techniques. It is shown here that, in contrast with previous models, surface charge convection provokes a difference between the upstream and the downstream wave speed values, the upstream wave speed, to some extent, being delayed. Subcritical, supercritical and convectively unstable regions are then identified. The supercritical nature of the microjets emitted from Taylor's cones is highlighted, and the point where the jet switches from a stable to a convectively unstable regime (i.e. where the propagation speed of perturbations become zero) is identified. The electric current carried by those jets is an eigenvalue of the problem, almost independent of the boundary conditions downstream, in an analogous way to the gas flow in convergent–divergent nozzles exiting into very low pressure. The EHD model is applied to an experiment and the relevant physical quantities of the phenomenon are obtained. The EHD hypotheses of the model are then checked and confirmed within the limits of the one-dimensional assumptions.

scholarly journals Critical flow and dissipation in a quasi–one-dimensional superfluid

2015 ◽  
Vol 1 (4) ◽  
pp. e1400222 ◽  
Author(s):  
Pierre-François Duc ◽  
Michel Savard ◽  
Matei Petrescu ◽  
Bernd Rosenow ◽  
Adrian Del Maestro ◽  
...  
Keyword(s):  
Power Law ◽  
Capillary Flow ◽  
Three Dimensional ◽  
Universality Class ◽  
Superfluid State ◽  
One Dimensional ◽  
Flow Experiment ◽  
20 Nm ◽  
Bulk Behavior ◽  
Superfluid Velocity

In one of the most celebrated examples of the theory of universal critical phenomena, the phase transition to the superfluid state of 4He belongs to the same three-dimensional (3D) O(2) universality class as the onset of ferromagnetism in a lattice of classical spins with XY symmetry. Below the transition, the superfluid density ρs and superfluid velocity vs increase as a power law of temperature described by a universal critical exponent that is constrained to be identical by scale invariance. As the dimensionality is reduced toward 1D, it is expected that enhanced thermal and quantum fluctuations preclude long-range order, thereby inhibiting superfluidity. We have measured the flow rate of liquid helium and deduced its superfluid velocity in a capillary flow experiment occurring in single 30-nm-long nanopores with radii ranging down from 20 to 3 nm. As the pore size is reduced toward the 1D limit, we observe the following: (i) a suppression of the pressure dependence of the superfluid velocity; (ii) a temperature dependence of vs that surprisingly can be well-fitted by a power law with a single exponent over a broad range of temperatures; and (iii) decreasing critical velocities as a function of decreasing radius for channel sizes below R ≃ 20 nm, in stark contrast with what is observed in micrometer-sized channels. We interpret these deviations from bulk behavior as signaling the crossover to a quasi-1D state, whereby the size of a critical topological defect is cut off by the channel radius.

scholarly journals Hybrid Monolith of Graphene/TEMPO-Oxidized Cellulose Nanofiber as Mechanically Robust, Highly Functional, and Recyclable Adsorbent of Methylene Blue Dye

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Asif Hussain ◽  
Jiebing Li ◽  
Jun Wang ◽  
Fei Xue ◽  
Yundan Chen ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Specific Surface ◽  
Charge Density ◽  
Surface Charge ◽  
Surface Area ◽  
Specific Surface Area ◽  
Surface Charge Density ◽  
Cellulose Nanofibers ◽  
Maximum Adsorption Capacity ◽  
Assembly Method

Herein we demonstrate first report on fabrication, characterization, and adsorptive appraisal of graphene/cellulose nanofibers (GO/CNFs) monolith for methylene blue (MB) dye. Series of hybrid monolith (GO/CNFs) were assembled via urea assisted self-assembly method. Hybrid materials were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction patterns, Raman spectroscopy, elemental analysis, thermogravimetric curve analysis, specific surface area, surface charge density measurement, and compressional mechanical analysis. It was proposed that strong chemical interaction (mainly hydrogen bonding) was responsible for the formation of hybrid assembly. GO/CNFs monolith showed mechanically robust architecture with tunable pore structure and surface properties. GO/CNFs adsorbent could completely remove trace to moderate concentrations of MB dye and follow pseudo-second-order kinetics model. Adsorption isotherm behaviors were found in the following order: Langmuir isotherm > Freundlich isotherm > Temkin isotherm model. Maximum adsorption capacity of 227.27 mg g−1 was achieved which is much higher than reported graphene based monoliths and magnetic adsorbent. Incorporation of nanocellulose follows exponential relationship with dye uptake capacities. High surface charge density and specific surface area were main dye adsorptive mechanism. Regeneration and recycling efficiency was achieved up to four consecutive cycles with cost-effective recollection and zero recontamination of treated water.

scholarly journals Scalable Preparation of Cellulose Nanofibers from Office Waste Paper by an Environment-Friendly Method

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3119
Author(s):  
Deyuan Huang ◽  
Haoqun Hong ◽  
Weilong Huang ◽  
Haiyan Zhang ◽  
Xiaobin Hong
Keyword(s):  
Electron Microscopy ◽  
Light Transmission ◽  
Alkali Treatment ◽  
Cellulose Nanofibers ◽  
Waste Paper ◽  
Narrow Particle Size Distribution ◽  
Cellulose Content ◽  
Tempo Oxidation ◽  
20 Nm ◽  
Bleaching Treatment

Waste paper is often underutilized as a low-value recyclable resource and can be a potential source of cellulose nanofibers (CNFs) due to its rich cellulose content. Three different processes, low acid treatment, alkali treatment and bleaching treatment, were used to pretreat the waste paper in order to investigate the effect of different pretreatments on the prepared CNFs, and CNFs obtained from bleached pulp boards were used as control. All sample fibers were successfully prepared into CNFs by 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) oxidation. It was quite obvious that the bleached CNFs samples showed dense fibrous structures on a scanning electron microscopy (SEM), while needle-like fibers with width less than 20 nm were observed on a transmission electron microscopy (TEM). Meanwhile, the bleaching treatment resulted in a 13.5% increase in crystallinity and a higher TEMPO yield (e.g., BCNF, 60.88%), but a decrease in thermal stability. All pretreated CNFs samples showed narrow particle size distribution, good dispersion stability (zeta potential less than −29.58 mV), good light transmission (higher than 86.5%) and low haze parameters (lower than 3.92%). This provides a good process option and pathway for scalable production of CNFs from waste papers.

scholarly journals Growth of width-controlled nanowires MnO2 from mesoporous carbon and investigation of their properties

2006 ◽  
Vol 21 (11) ◽  
pp. 2847-2854 ◽  
Author(s):  
Shenmin Zhu ◽  
Xiaolin Wang ◽  
Wei Huang ◽  
Deyue Yan ◽  
Honghua Wang ◽  
...  
Keyword(s):  
Mesoporous Carbon ◽  
Magnetic Transition ◽  
Reaction System ◽  
Ferromagnetic State ◽  
Ultrasonic Waves ◽  
Controlled Synthesis ◽  
One Dimensional ◽  
System A ◽  
20 Nm ◽  
Resultant Material

One-dimensional α-MnO2 nanowires with a controlled width of 10–20 nm have been developed by means of ultrasonic waves from mesoporous carbon using KMnO4 as the precursor. The formation mechanism has been proposed based on the results. A peak around 100 K was detected in the temperature-dependence of magnetization curve, indicating the ferromagnetic state in nanocomposite mesoporous carbon-MnO2, which is in agreement with the transition temperature found from the magnetization versus applied magnetic field curve. The magnetization versus temperature curve of the obtained MnO2 nanowires showed a magnetic transition at about 50 K, illustrating that a parasitic ferromagnetic component is composed on the antiferromagnetic structure of MnO2. The advantage of the method reported here is that phase-controlled synthesis of α-MnO2 nanowires was implemented regardless of pH, temperature, and types of ions in the reaction system. A major advantage of this approach is the efficient, fast, and reproducible control of width and the facile strategy to synthesize nanowires MnO2, in addition to the high purity of the resultant material.

Strong Aqueous Gels of Cellulose Nanofibers and Nanowhiskers Isolated from Softwood Flour

TAPPI Journal ◽  
2011 ◽  
Vol 10 (2) ◽  
pp. 7-14 ◽  
Author(s):  
GUAN GONG ◽  
AJI P. MATHEW ◽  
KRISTIINA OKSMAN
Keyword(s):  
Acid Hydrolysis ◽  
Aqueous Suspension ◽  
Cellulose Nanofibers ◽  
Low Frequency ◽  
Aqueous Gels ◽  
Frequency Independent ◽  
Solids Content ◽  
Mechanical Fibrillation ◽  
20 Nm ◽  
Long Fibers

Two nanocelluloses (cellulose nanofibers [CNF] and nanowhiskers [CNW]) were extracted from softwood flour using chemical refining followed either by mechanical fibrillation or acid hydrolysis. The CNF slurry formed an opaque gel that exhibited highly coiled and entangled long fibers with widths between 10 and 20 nm when studied using atomic force microscopy (AFM). The aqueous suspension of the CNW formed a transparent gel with unique morphology of rigid and uniform, whiskerlike structures with widths as low as 1.5–3 nm and lengths in micrometer levels. The viscoelastic properties of these hydrogels with solids content of 0.2 wt% were measured using dynamic rheology experiments. The elastic modulus (G') and viscous modulus (G'') were frequency independent in the low-frequency region. Furthermore, G' was almost 10-fold higher than G'', showing a typical elastic gel behavior. The lower crystallinity obtained from X-ray analysis indicated that the unique structure of CNW from wood could be attributed to the native cellulose being partly dissolved and regenerated during acid hydrolysis.

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