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Akira Isogai - One of the best experts on this subject based on the ideXlab platform.

  • dual functions of tempo oxidized Cellulose Nanofibers in oil in water emulsions a pickering emulsifier and a unique dispersion stabilizer
    Langmuir, 2019
    Co-Authors: Shuji Fujisawa, Tsuguyuki Saito, Kenichi Yamane, Katsushi Kuroda, Akira Isogai
    Abstract:

    The emulsifying and dispersing mechanisms of oil-in-water emulsions stabilized by 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized Cellulose Nanofibers (CNFs) have been investigated. The emulsi...

  • Development of completely dispersed Cellulose Nanofibers.
    Proceedings of the Japan Academy. Series B Physical and biological sciences, 2018
    Co-Authors: Akira Isogai
    Abstract:

    : Plant Cellulose fibers of width and length ∼0.03 mm and ∼3 mm, respectively, can be completely converted to individual Cellulose Nanofibers of width and length ∼3 nm and ∼1 µm, respectively, by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation under aqueous conditions and subsequent gentle mechanical disintegration of the oxidized Cellulose in water. The obtained TEMPO-oxidized Cellulose Nanofibers (TOCNs) are new bio-based, crystalline nanomaterials with applications in the high-tech and commodity product industries. Sodium carboxylate groups, which are densely, regularly, and position-selectively present on the crystalline TOCN surfaces, can be efficiently ion-exchanged with other metal and alkylammonium carboxylate groups in water to control the biodegradable/stable and hydrophilic/hydrophobic properties of the TOCNs. TOCNs are therefore promising nanomaterials that can be prepared from the abundant wood biomass resources present in Japan. Increased production and use of TOCNs would stimulate a new material stream from forestry to industries, helping to establish a sustainable society based on wood biomass resources.

  • chemical modification of Cellulose Nanofibers for the production of highly thermal resistant and optically transparent nanopaper for paper devices
    ACS Applied Materials & Interfaces, 2015
    Co-Authors: Hitomi Yagyu, Tsuguyuki Saito, Hirotaka Koga, Akira Isogai, Masaya Nogi
    Abstract:

    Optically transparent Cellulose nanopaper is one of the best candidate substrates for flexible electronics. Some types of Cellulose nanopaper are made of mechanically or chemically modified Cellulose Nanofibers. Among these, nanopapers produced from chemically modified Cellulose Nanofibers are the most promising substrate because of their lower power consumption during fabrication and higher optical transparency (lower haze). However, because their thermal durability is as low as plastics, paper devices using chemically modified nanopaper often do not have sufficiently high performance. In this study, by decreasing the carboxylate content in the Cellulose Nanofibers, the thermal durability of chemically modified nanopaper was drastically improved while maintaining high optical transparency, low coefficient of thermal expansion, and low power consumption during fabrication. As a result, light-emitting diode lights illuminated on the chemically modified nanopaper via highly conductive lines, which were obta...

  • Chemical Modification of Cellulose Nanofibers for the Production of Highly Thermal Resistant and Optically Transparent Nanopaper for Paper Devices
    ACS Applied Materials and Interfaces, 2015
    Co-Authors: Hitomi Yagyu, Tsuguyuki Saito, Hirotaka Koga, Akira Isogai, Masaya Nogi
    Abstract:

    Optically transparent Cellulose nanopaper is one of the best candidate substrates for flexible electronics. Some types of Cellulose nanopaper are made of mechanically or chemically modified Cellulose Nanofibers. Among these, nanopapers produced from chemically modified Cellulose Nanofibers are the most promising substrate because of their lower power consumption during fabrication and higher optical transparency (lower haze). However, because their thermal durability is as low as plastics, paper devices using chemically modified nanopaper often do not have sufficiently high performance. In this study, by decreasing the carboxylate content in the Cellulose Nanofibers, the thermal durability of chemically modified nanopaper was drastically improved while maintaining high optical transparency, low coefficient of thermal expansion, and low power consumption during fabrication. As a result, light-emitting diode lights illuminated on the chemically modified nanopaper via highly conductive lines, which were obtained by printing silver nanoparticle inks and high-temperature heating.

  • viscoelastic evaluation of average length of Cellulose Nanofibers prepared by tempo mediated oxidation
    Biomacromolecules, 2011
    Co-Authors: Daisuke Ishii, Tsuguyuki Saito, Akira Isogai
    Abstract:

    Dynamic viscoelasticity measurements were performed for aqueous dispersions of Cellulose Nanofibers prepared by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and subsequent mechanical disintegration in water. The frequency dependence of the storage and loss moduli of 0.02% (w/v) dispersions of TEMPO-oxidized Cellulose Nanofibers in water showed terminal relaxation behavior at relatively lower angular frequencies. This strongly suggests that each Cellulose nanofiber in the dispersion behaves as a semiflexible rod-like macromolecular chain or colloidal particle. Furthermore, a clear boundary was observed between the terminal relaxation and rubbery plateau regions. The longest viscoelastic relaxation time, τ, was estimated from the angular frequency, corresponding to the boundary point, and the average length of the Cellulose Nanofibers, L, was estimated using the equation τ = πηsL3/[18kBT ln(L/d)]. The equation gave a value of L = 2.2 μm, which was in good agreement with TEM observ...

Tsuguyuki Saito - One of the best experts on this subject based on the ideXlab platform.

  • Local Crystallinity in Twisted Cellulose Nanofibers
    2020
    Co-Authors: Tom Willhammar, Kazuho Daicho, Duncan Johnstone, Kayoko Kobayashi, Paul A. Midgley, Lennart Bergström, Tsuguyuki Saito
    Abstract:

    Cellulose is crystallized by plants and other organisms into fibrous nanocrystals. The mechanical properties of these Nanofibers and the formation of helical superstructures with energy dissipating and adaptive optical properties depend on the ordering of polysaccharide chains within these nanocrystals, which is typically measured in bulk average. Direct measurement of the local polysaccharide chain arrangement has been elusive. In this study, we use the emerging technique of scanning electron diffraction to probe the packing of polysaccharide chains across Cellulose Nanofibers and to reveal local ordering of the chains in twisting sections of the Nanofibers. We then use atomic force microscopy to shed light on the size dependence of the inherent driving force for Cellulose nanofiber twisting. The direct measurement of crystalline twisted regions in Cellulose Nanofibers has important implications for understanding single Cellulose fibril properties that influence the interactions between Cellulose nanocrystals in dense assemblies. This understanding may enable Cellulose extraction and separation processes to be tailored and optimized.<br>

  • dual functions of tempo oxidized Cellulose Nanofibers in oil in water emulsions a pickering emulsifier and a unique dispersion stabilizer
    Langmuir, 2019
    Co-Authors: Shuji Fujisawa, Tsuguyuki Saito, Kenichi Yamane, Katsushi Kuroda, Akira Isogai
    Abstract:

    The emulsifying and dispersing mechanisms of oil-in-water emulsions stabilized by 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized Cellulose Nanofibers (CNFs) have been investigated. The emulsi...

  • chemical modification of Cellulose Nanofibers for the production of highly thermal resistant and optically transparent nanopaper for paper devices
    ACS Applied Materials & Interfaces, 2015
    Co-Authors: Hitomi Yagyu, Tsuguyuki Saito, Hirotaka Koga, Akira Isogai, Masaya Nogi
    Abstract:

    Optically transparent Cellulose nanopaper is one of the best candidate substrates for flexible electronics. Some types of Cellulose nanopaper are made of mechanically or chemically modified Cellulose Nanofibers. Among these, nanopapers produced from chemically modified Cellulose Nanofibers are the most promising substrate because of their lower power consumption during fabrication and higher optical transparency (lower haze). However, because their thermal durability is as low as plastics, paper devices using chemically modified nanopaper often do not have sufficiently high performance. In this study, by decreasing the carboxylate content in the Cellulose Nanofibers, the thermal durability of chemically modified nanopaper was drastically improved while maintaining high optical transparency, low coefficient of thermal expansion, and low power consumption during fabrication. As a result, light-emitting diode lights illuminated on the chemically modified nanopaper via highly conductive lines, which were obta...

  • Chemical Modification of Cellulose Nanofibers for the Production of Highly Thermal Resistant and Optically Transparent Nanopaper for Paper Devices
    ACS Applied Materials and Interfaces, 2015
    Co-Authors: Hitomi Yagyu, Tsuguyuki Saito, Hirotaka Koga, Akira Isogai, Masaya Nogi
    Abstract:

    Optically transparent Cellulose nanopaper is one of the best candidate substrates for flexible electronics. Some types of Cellulose nanopaper are made of mechanically or chemically modified Cellulose Nanofibers. Among these, nanopapers produced from chemically modified Cellulose Nanofibers are the most promising substrate because of their lower power consumption during fabrication and higher optical transparency (lower haze). However, because their thermal durability is as low as plastics, paper devices using chemically modified nanopaper often do not have sufficiently high performance. In this study, by decreasing the carboxylate content in the Cellulose Nanofibers, the thermal durability of chemically modified nanopaper was drastically improved while maintaining high optical transparency, low coefficient of thermal expansion, and low power consumption during fabrication. As a result, light-emitting diode lights illuminated on the chemically modified nanopaper via highly conductive lines, which were obtained by printing silver nanoparticle inks and high-temperature heating.

  • viscoelastic evaluation of average length of Cellulose Nanofibers prepared by tempo mediated oxidation
    Biomacromolecules, 2011
    Co-Authors: Daisuke Ishii, Tsuguyuki Saito, Akira Isogai
    Abstract:

    Dynamic viscoelasticity measurements were performed for aqueous dispersions of Cellulose Nanofibers prepared by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and subsequent mechanical disintegration in water. The frequency dependence of the storage and loss moduli of 0.02% (w/v) dispersions of TEMPO-oxidized Cellulose Nanofibers in water showed terminal relaxation behavior at relatively lower angular frequencies. This strongly suggests that each Cellulose nanofiber in the dispersion behaves as a semiflexible rod-like macromolecular chain or colloidal particle. Furthermore, a clear boundary was observed between the terminal relaxation and rubbery plateau regions. The longest viscoelastic relaxation time, τ, was estimated from the angular frequency, corresponding to the boundary point, and the average length of the Cellulose Nanofibers, L, was estimated using the equation τ = πηsL3/[18kBT ln(L/d)]. The equation gave a value of L = 2.2 μm, which was in good agreement with TEM observ...

Kristiina Oksman - One of the best experts on this subject based on the ideXlab platform.

Zeeshan Khatri - One of the best experts on this subject based on the ideXlab platform.

  • Ionic cross-linking of Cellulose Nanofibers: an approach to enhance mechanical stability for dynamic adsorption
    Environmental Science and Pollution Research, 2019
    Co-Authors: Muhammad Muqeet, Rasool Bux Mahar, Zeeshan Khatri, Umair Ahmed Qureshi, Farooq Ahmed
    Abstract:

    Herein, we attempt to improve the mechanical stability of anionic functionalized Cellulose Nanofibers (a-CNF) having 1.25 mmol of carboxymethyl groups per gram of Cellulose Nanofibers (CNF). The a-CNF and cross-linked a-CNF (z_a-CNF) then used for water desalination in the continuous mode using a tubular adsorption column. It is worth mentioning that the z_a-CNF possess 40% degree of cross-linking provided better mechanical stability as the tensile strength improved from 3.2 to 5.2 MPa over a-CNF. The IR spectroscopy was used to confirm the success of chemical modifications. Upon ionic cross-linking, the BET surface area reduced from 13.53 to 7.54 m^2·g^−1 corresponds to a-CNF and z_a-CNF, respectively. Moreover, this research was extended to determine the dynamic adsorption capacities for a-CNF and z_a-CNF, which were found to be 21 and 10 mg·g^−1 respectively at a flow rate of 5-mL·min^−1 explained by Thomas model.

  • Screen-printed electrospun Cellulose Nanofibers using reactive dyes
    Cellulose, 2017
    Co-Authors: Zeeshan Khatri, Muzamil Khatri, Farooq Ahmed, Awais Khatri, Umair Ahmed Qureshi
    Abstract:

    Recently, great deal of attention has been paid to dyeing of Nanofibers. Herein, the printing of Nanofibers has been reported for the very first time. We chose electrospun Cellulose Nanofibers (ECNF) and printed with three different classes of reactive dyes by flat screen-printing method. The various printing parameters were investigated such as steaming time, dye build-up property, color penetration. Results revealed that the Nanofibers after printing showed good color yield and obtained 92% dye fixation within 7 min of steaming time. Irrespective to dye class, the color build-up property on ECNF showed a linear relationship with increasing dye concentration and demonstrated overall good dye color fastness properties. SEM images showed smooth morphology of ECNF after reactive printing. This technique opens a new door to produce colored patterns and designs on to nanofiber webs that can be utilized for aesthetic as well as functional purposes.

  • Ultrasonic dyeing of Cellulose Nanofibers
    Ultrasonics Sonochemistry, 2016
    Co-Authors: Muzamil Khatri, Abdul Wahab Jatoi, Rasool Bux Mahar, Farooq Ahmed, Zeeshan Khatri, Ick Soo Kim
    Abstract:

    Textile dyeing assisted by ultrasonic energy has attained a greater interest in recent years. We report ultrasonic dyeing of Nanofibers for the very first time. We chose Cellulose Nanofibers and dyed with two reactive dyes, CI reactive black 5 and CI reactive red 195. The Cellulose Nanofibers were prepared by electrospinning of Cellulose acetate (CA) followed by deacetylation. The FTIR results confirmed complete conversion of CA into Cellulose Nanofibers. Dyeing parameters optimized were dyeing temperature, dyeing time and dye concentrations for each class of the dye used. Results revealed that the ultrasonic dyeing produced higher color yield (K/S values) than the conventional dyeing. The color fastness test results depicted good dye fixation. SEM analysis evidenced that ultrasonic energy during dyeing do not affect surface morphology of Nanofibers. The results conclude successful dyeing of Cellulose Nanofibers using ultrasonic energy with better color yield and color fastness results than conventional dyeing.

  • Cold pad-batch dyeing of Cellulose Nanofibers with reactive dyes
    Cellulose, 2014
    Co-Authors: Zeeshan Khatri, Farooq Ahmed, Abdul Khaliq Jhatial, Muhammad Ishaque Abro, Gopiraman Mayakrishnan
    Abstract:

    The dyeability of electrospun Nanofibers for apparel application has recently gained substantial interest. Past work focused on batchwise and continuous dyeing methods, but they required a certain temperature for dye fixation. We report on the dyeing of Cellulose Nanofibers by the cold pad-batch method, which offers the most economical and convenient method of dyeing cellulosic Nanofibers with reactive dyes. Cellulose acetate (CA) Nanofibers were fabricated via electrospinning and then deacetylated to convert CA into Cellulose nanofiber. The Cellulose nanofiber webs were dyed with three different classes of reactive dyes. CI Reactive Black 5 obtained the highest color yield in comparison to CI Reactive Red 195 and CI Reactive Blue 19. The dye fixation for all dyes achieved between 80 and 85 %. Except color fastness to light, washing fastness of dyed Cellulose Nanofibers obtained very good to excellent results. To investigate the chemical structure and fiber morphology of the Cellulose Nanofibers, Fourier transform infrared spectroscopy and scanning electron microscopy were used respectively. Graphical Abstract

  • Dyeing and characterization of Cellulose Nanofibers to improve color yields by dual padding method
    Cellulose, 2013
    Co-Authors: Zeeshan Khatri, Abdul Wahab Jatoi, Rabia Almas Arain, Gopiraman Mayakrishnan
    Abstract:

    The study of functional and dyeing properties of the electrospun Nanofibers has recently gained substantial interest. However, the dyeing of Nanofibers still in transition phase and faces problem of lower color yield. Owing to the higher surface area of Cellulose Nanofibers, the color yield obtained is nearly four to five times lower than the conventional cotton fiber. The present work reports on dyeing of Cellulose Nanofibers with CI reactive black 5 dye via a simple and dual padding method to improve color yield and dye fixation. The color yields were determined by K/S values and color coordinates using spectrophotometer and the results were compered between single and dual padding methods. The dyed Cellulose Nanofibers were characterized by FTIR, WAXD and FE-SEM. X-ray diffraction studies revealed that the dyed Cellulose Nanofibers having Cellulose II form and show a better crystallinity than the undyed Cellulose Nanofibers. Graphical abstract  

Hayaka Fukuzumi - One of the best experts on this subject based on the ideXlab platform.

  • TEMPO-oxidized Cellulose Nanofibers
    Nanoscale, 2011
    Co-Authors: Akira Isogai, Tsuguyuki Saito, Hayaka Fukuzumi
    Abstract:

    Native wood Celluloses can be converted to individual Nanofibers 3-4 nm wide that are at least several microns in length, i.e. with aspect ratios>100, by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and successive mild disintegration in water. Preparation methods and fundamental characteristics of TEMPO-oxidized Cellulose Nanofibers (TOCN) are reviewed in this paper. Significant amounts of C6 carboxylate groups are selectively formed on each Cellulose microfibril surface by TEMPO-mediated oxidation without any changes to the original crystallinity (∼74%) or crystal width of wood Celluloses. Electrostatic repulsion and/or osmotic effects working between anionically-charged Cellulose microfibrils, the ζ-potentials of which are approximately -75 mV in water, cause the formation of completely individualized TOCN dispersed in water by gentle mechanical disintegration treatment of TEMPO-oxidized wood Cellulose fibers. Self-standing TOCN films are transparent and flexible, with high tensile strengths of 200-300 MPa and elastic moduli of 6-7 GPa. Moreover, TOCN-coated poly(lactic acid) films have extremely low oxygen permeability. The new Cellulose-based Nanofibers formed by size reduction process of native Cellulose fibers by TEMPO-mediated oxidation have potential application as environmentally friendly and new bio-based nanomaterials in high-tech fields.

  • Transparent and high gas barrier films of Cellulose Nanofibers prepared by TEMPO-mediated oxidation
    Biomacromolecules, 2009
    Co-Authors: Hayaka Fukuzumi, Yasuaki Kumamoto, Tsuguyuki Saito, Tadahisa Iwata, Akira Isogai
    Abstract:

    Softwood and hardwood Celluloses were oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. The TEMPO-oxidized Cellulose fibers were converted to transparent dispersions in water, which consisted of individual Nanofibers 3−4 nm in width. Films were then prepared from the TEMPO-oxidized Cellulose Nanofibers (TOCN) and characterized from various aspects. AFM images showed that the TOCN film surface consisted of randomly assembled Cellulose Nanofibers. The TOCN films prepared from softwood Cellulose were transparent and flexible and had extremely low coefficients of thermal expansion caused by high crystallinity of TOCN. Moreover, oxygen permeability of a polylactic acid (PLA) film drastically decreased to about 1/750 by forming a thin TOCN layer on the PLA film. Hydrophobization of the originally hydrophilic TOCN films was achieved by treatment with alkylketene dimer. These unique characteristics of the TOCN films are promising for potential applications in some high-tech mate...