[en] Highly stable, luminescent, and printable/paintable supramolecular egg white hydrogel-based surface enhanced Raman scattering (SERS) matrix is created by an in situ synthesis of gold clusters inside a luminescent egg white hydrogel (Au-Gel). The synthesis of stable luminescent egg-white-based hydrogel, where the hydrogel can act as a three dimensional (3D) matrix, using a simple cross-linking chemistry, has promising application in the biomedical field including in 3D cell culturing. Furthermore, this functional hydrogel is demonstrated for micromolar-level detection of Rhodamine 6G using the SERS technique, where Au-Gel is painted over a flexible cellulose pad. (paper)

[en] Two-dimensional (2D) tungsten diselenide (WSe${}_2$)-based porous three-dimensional (3D) architecture is fabricated utilizing highly porous 3D alumina structures. The architecture is produced by combining a sol–gel process for fabricating porous 3D alumina and chemical vapor deposition (CVD) for the formation of WSe${}_2$. The gas-sensing performance of the porous 3D structure overcomes the limitations displayed by the gas response of a 2D WSe${}_2$-based gas sensor. This 2D nanomaterials-based porous 3D architecture is a promising approach for improving the gas response of sensing devices. (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

[en] Molybdenum disulfide (MoS${}_2$) is a promising alternative to graphite anodes in battery materials. Therefore, it is critical to scrutinize their structural stability and charge storage capacity during battery operation. Herein, freestanding electrodes consisting of MoS${}_2$-incorporated carbon nanotube aerogels are fabricated using a simple yet scalable hydrothermal method, as used in lithium-ion batteries. The outer nitrogen-doped graphitic carbon (NGr) layers support efficient charge transport, even under a substantial compressive environment, and improve the structural integrity, showing significant improvements in battery performance, such as a high rate capacity of 820 mAh g${}^{-<!--\; ???\; -->1}$ at the current density of 5 A g${}^{-<!--\; ???\; -->1}$ and 94% capacity retention after 170 cycles (1170 mAh g${}^{-<!--\; ???\; -->1}$ at 1 A g${}^{-<!--\; ???\; -->1}$ after 170 cycles), even in the absence of polymer binders and conductive additives. The resulting NGr/MoS${}_2$/single-walled carbon nanotubes freestanding electrodes have great potential to increase the volumetric and gravimetric energy density of batteries. (© 2024 Wiley‐VCH GmbH)

[en] Si-based optical devices would benefit significantly from large scalable and economic illumination sources. Although we previously demonstrated Si-based homoepitaxial light-emitting diodes (LEDs) with large scalability and highly efficient opto-electrical characteristics, the origin of their high quantum efficiency has not been explored. Here, we reveal the origin of the significantly improved quantum efficiency of InGaN/GaN blue LEDs on Si-based freestanding GaN. In power-dependent photoluminescence measurements, the redshifts and blueshifts with increasing injection power indicate a reduced internal electric field of the devices. Furthermore, time-resolved photoluminescence curves for the Si-based homoepitaxial InGaN/GaN LEDs exhibit much larger decay components, suggesting a reduced piezoelectric polarization field, strong quantum confinement effect, and improved material quality of the LEDs. A relatively improved external quantum efficiency of the diodes also confirms the reduced dislocation density and internal electric field in the homoepitaxial device. These findings clearly support that the suppressed structural defects and piezoelectric polarization field are responsible for the remarkable quantum efficiency of the InGaN/GaN blue LEDs on Si-based freestanding GaN. (paper)

[en] In an effort to combine group III–V semiconductors with carbon nanotubes, a simple solution-based technique for gallium functionalization of nitrogen-doped multi-wall carbon nanotubes has been developed. With an aqueous solution of a gallium salt (GaI₃), it was possible to form covalent bonds between the Ga³⁺ ion and the nitrogen atoms of the doped carbon nanotubes to form a gallium nitride–carbon nanotube hybrid at room temperature. This functionalization was evaluated by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy (paper)

[en] Scalable sub-micrometer molybdenum disulfide (${\mathrm{M}\mathrm{o}\mathrm{S}}_2$) flake films with highly uniform coverage were created using a systematic approach. An electrohydrodynamic (EHD) printing process realized a remarkably uniform distribution of exfoliated ${\mathrm{M}\mathrm{o}\mathrm{S}}_2$ flakes on desired substrates. In combination with a fast evaporating dispersion medium and an optimal choice of operating parameters, the EHD printing can produce a film rapidly on a substrate without excessive agglomeration or cluster formation, which can be problems in previously reported liquid-based continuous film methods. The printing of exfoliated ${\mathrm{M}\mathrm{o}\mathrm{S}}_2$ flakes enabled the fabrication of a gas sensor with high performance and reproducibility for ${\mathrm{N}\mathrm{O}}_2$ and ${\mathrm{N}\mathrm{H}}_3$. (paper)

[en] Al-based composites incorporating multilayered graphene sheets were developed via a facile approach. The multilayered graphene sheets were fabricated from the expanded graphite via a simple mechanical exfoliation process. The facile extrusion molding process with Al powder and graphene sheets exfoliated from expended graphite afforded Al-based graphene composite rods. These composites showed enhanced thermal conductivity compared to the pristine Al rods. Moreover, the Al-based multilayered graphene sheet composites exhibited lower interfacial contact resistance between graphene-based electrodes than the pristine Al. With increasing degrees of dispersion, the number of exposed graphene sheets increases, thereby significantly decreasing the interfacial contact resistance between the composite and external graphite electrode. (paper)