Daihong Huh

Fabrication of a transparent conducting Ni-nanomesh-embedded film using template-assisted Ni electrodeposition and hot transfer process

In the present work, we developed a new method for fabricating Ni nanomeshes for transparent conducting electrodes using template-assisted Ni electrodeposition and a hot transfer process. By employing the direct printing of hydrogen silsesquioxane (HSQ), the microscale HSQ template was successfully transferred onto a stainless steel substrate. The Ni nanomesh was fabricated using selective Ni electrodeposition and a hot transfer process on a polycarbonate (PC) film. The Ni-nanomesh-embedded PC film exhibited approximately 77% of the transmittance of the PC film and a sheet resistance of 2–10 Ω sq−1. In addition, the transmittance and sheet resistance of the Ni-nanomesh-embedded PC film were not significantly degraded after 20000 cycles of bending tests.

Metal–Organic Framework-Templated PdO-Co3O4 Nanocubes Functionalized by SWCNTs: Improved NO2 Reaction Kinetics on Flexible Heating Film

Detection and control of air quality are major concerns in recent years for environmental monitoring and healthcare. In this work, we developed an integrated sensor architecture comprised of nanostructured composite sensing layers and a flexible heating substrate for portable and real-time detection of nitrogen dioxide (NO2). As sensing layers, PdO-infiltrated Co3O4 hollow nanocubes (PdO-Co3O4 HNCs) were prepared by calcination of Pd-embedded Co-based metal-organic framework polyhedron particles. Single-walled carbon nanotubes (SWCNTs) were functionalized with PdO-Co3O4 HNCs to control conductivity of sensing layers. As a flexible heating substrate, the Ni mesh electrode covered with a 40 nm thick Au layer (i.e., Ni(core)/Au(shell) mesh) was embedded in a colorless polyimide (cPI) film. As a result, SWCNT-functionalized PdO-Co3O4 HNCs sensor exhibited improved NO2 detection property at 100 °C, with high sensitivity (S) of 44.11% at 20 ppm and a low detection limit of 1 ppm. The accelerated reaction and recovery kinetics toward NO2 of SWCNT-functionalized PdO-Co3O4 HNCs were achieved by generating heat on the Ni(core)/Au(shell) mesh-embedded cPI substrate. The SWCNT-functionalized porous metal oxide sensing layers integrated on the mechanically stable Ni(core)/Au(shell) mesh heating substrate can be envisioned as an essential sensing platform for realization of low-temperature operation wearable chemical sensor.

Direct patterning process for tungsten trioxide nano-to-micro structures

ABSTRACT Compared to conventional and complex processes, including deposition, photolithography, and plasma-etching processes, WO3 nano-to-micro structures were successfully fabricated using direct imprinting process using WO3 nanoparticle-dispersed resin and consecutive annealing on any substrates in a simpler and more cost-effective manner. WO3 nanoparticle dispersed resins with various concentrations were evaluated for direct imprinting of WO3. The pattern fidelity and the surface morphology of imprinted WO3 nano-to-micro structures were characterized with field emission SEM. X-ray diffractionpattern was used to investigate the effect of annealing process on crystallinity of WO3 nano-to-micro structures. The crystal structure of imprinted WO3 was transformed from a hexagonal phase into a monoclinic phase by annealing. Optical transmittance of WO3 structures were also investigated using UV-vis spectroscopy. It was confirmed that diffused transmittance of WO3 structures could be increased up to 70% at 550 nm of wavelength without noticeable reduction of total transmittance, which is potentially applicable in the field of optoelectronic devices. Photo-electrochemical cells made of imprinted WO3 structure were properly operated.

Spontaneous Registration of Sub-10 nm Features Based on Subzero Celsius Spin-Casting of Self-Assembling Building Blocks Directed by Chemically Encoded Surfaces

For low-cost and facile fabrication of innovative nanoscale devices with outstanding functionality and performance, it is critical to develop more practical patterning solutions that are applicable to a wide range of materials and feature sizes while minimizing detrimental effects by processing conditions. In this study, we report that area-selective sub-10 nm pattern formation can be realized by temperature-controlled spin-casting of block copolymers (BCPs) combined with submicron-scale-patterned chemical surfaces. Compared to conventional room-temperature spin-casting, the low temperature ( e.g., -5 °C) casting of the BCP solution on the patterned self-assembled monolayer achieved substantially improved area selectivity and uniformity, which can be explained by optimized solvent evaporation kinetics during the last stage of film formation. Moreover, the application of cold spin-casting can also provide high-yield in situ patterning of light-emitting CdSe/ZnS quantum dot thin films, indicating that this temperature-optimized spin-casting strategy would be highly effective for tailored patterning of diverse organic and hybrid materials in solution phase.