Hirotaka Koga

Ultrastrong, transparent, conductive and printable nanocomposites were successfully prepared by mixing single-walled carbon nanotubes (CNTs) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) with abundant sodium carboxyl groups on the crystalline nanocellulose surfaces. The surface-anionic cellulose nanofibrils had reinforcing and nanodispersing effects on the CNTs both in water used as the dispersed medium and in the dried composite film, providing highly

We demonstrate the fabrication of highly transparent conductive networks on a cellulose nanofiber paper, called cellulose nanopaper. Uniform coating of the conductive nanomaterials, such as silver nanowires (AgNWs) and carbon nanotubes, is achieved by simple filtration of their aqueous dispersions through the cellulose nanopaper, which acts as both filter and transparent flexible substrate. The as-prepared AgNW networks on the nanopaper offer sheet resistance of 12 Ω sq.−1 with optical transpare

A high-dielectric-constant and flexible cellulose nanopaper composite is prepared by mixing a small amount of silver nanowires with cellulose nanofibers. The nanopaper antenna is downsized by about a half when using the nanopaper substrate. The nanopaper antenna has potential in wearable wireless communication devices.

Amino groups were successfully introduced to cellulose paper using a silane coupling technique, through the condensation reaction between Si–OH of the organofunctional silane coupling agent and C–OH of cellulose. The as-prepared paper material, denoted amine-modified paper, had excellent handling convenience and some degree of hydrophobicity, indicating that the silane coupling treatment enhances the physical strength and the hydrophobicity of cellulose paper. In the batch process of the Knoeven

A green and scalable strategy for fabrication of a reduced graphene oxide (rGO)/cellulose paper supercapacitor electrode is demonstrated by a combination of well-established papermaking and millisecond-timescale flash reduction.

With the increasing use of microwaves, the functional design of carbon-based microwave absorbers has gained attention toward overcoming severe electromagnetic pollution, owing to the lightweight and broadband absorption properties of these absorbers. The key functions for realizing strong microwave absorption include good impedance matching to the impedance of free air, moderate conductive loss, and high polarization loss. However, it remains challenging to incorporate these complex functions in

Progress toward the concept of "a trillion sensor universe" requires sensor devices to become more abundant, ubiquitous, and be potentially disposable. Here, we report a paper-based disposable molecular sensor device constructed from a nanowire sensor based on common zinc oxide (ZnO), a wood-derived biodegradable cellulose nanofiber paper substrate, and a low-cost graphite electrode. The ZnO nanowire/cellulose nanofiber composite structure is embedded in the surface of the cellulose nanofiber pa

Topological loading of monovalent copper ions (Cu(I)) onto the crystal surfaces of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs), which have a large number of sodium (Na) carboxylate groups on their surfaces, was achieved through ion exchange between Na and Cu species. The Cu-loaded TOCNs were fabricated into aerogels by a freeze-dry treatment. The as-prepared Cu–TOCN aerogel demonstrated an excellent catalytic efficiency for the azide–alkyne Huisgen [3 + 2]

The increasing use of microwaves in wireless communications has caused severe electromagnetic pollution. As the frequency range for wireless communication is expanding, it is highly desirable to develop a microwave absorber that can smartly and reversibly tune its absorption and transmission properties on demand to transmit required frequencies and absorb unwanted frequencies. Herein, an absorption-frequency-tunable and absorption/transmission-switchable microwave absorber is developed based on

Semiconducting nanomaterials with 3D network structures exhibit various fascinating properties such as electrical conduction, high permeability, and large surface areas, which are beneficial for adsorption, separation, and sensing applications. However, research on these materials is substantially restricted by the limited trans-scalability of their structural design and tunability of electrical conductivity. To overcome this challenge, a pyrolyzed cellulose nanofiber paper (CNP) semiconductor w

Abundant and renewable all-cellulose-derived humidity sensors are fabricated via direct laser writing of patterned electrodes onto TEMPO-oxidized cellulose fiber paper, offering versatile applicability for the “trillion sensor” era.

We discuss the successful use of chemically-modified cellulose paper as a microstructured catalytic reactor for the production of useful chemicals. The chemical modification of cellulose paper was achieved using a silane-coupling technique. Amine-modified paper was directly used as a base catalyst for the Knoevenagel condensation reaction. Methacrylate-modified paper was used for the immobilization of lipase and then in nonaqueous transesterification processes. These catalytic paper materials of

Continuous-flow nanocatalysis based on metal nanoparticle catalyst-anchored flow reactors has recently provided an excellent platform for effective chemical manufacturing. However, there has been limited progress in porous structure design and recycling systems for metal nanoparticle-anchored flow reactors to create more efficient and sustainable catalytic processes. In this study, traditional paper is used for a highly efficient, recyclable, and even renewable flow reactor by tailoring the ultr