The importance of monitoring the condition of skin is increasing as its relevance to health is becoming more well understood. Inappropriate humidity levels can cause atopic dermatitis or hair loss. However, conventional film substrates used in electronic skin monitoring devices cause accumulation of sweat or gas between the device and biological tissue, leading to negative effects in long-term humidity measurements. Thus, real-time measurements of skin humidity over long periods are difficult using conventional film devices. Here, a breathable nanomesh humidity sensor that can monitor skin humidity for a long time is developed by using biocompatible materials such as gold, poly(vinyl alcohol), and Parylene C. The sensor presents excellent gas and sweat permeability and precisely detects the humidity level of an object for a long time. This study demonstrates the successful real-time detection of the humidity level from human skin and also detects the relative humidity of a plant surface over a prolonged period. This sensor is expected to have wide applicability for cultivating delicate plants as well as to reveal correlations between skin humidity and disease for biomedical applications.
In
MoS2–carbon composite catalysts for hydrogen
evolution reaction (HER), the carbon materials generally act as supports
to enhance the catalytic activity of MoS2 nanosheets. The
carbon support provides a large surface area for increasing the MoS2 edge site density, and its physical structure can affect
the electron transport rate in the composite catalysts. However, despite
the importance of the carbon materials, direct observation of the
effects of the physical properties of the carbon supports on the HER
activity of MoS2–carbon composite catalysts has
been hardly reported. In this work, we conduct an experimental model
study to find the fundamental and important understanding of the correlation
between the structural characteristics of carbon supports and the
HER performance of MoS2–carbon composite catalysts
using surface-modified graphitic carbon shell (GCS)-encapsulated SiO2 nanowires (GCS@SiO2 NWs) as support materials
for MoS2 nanosheets. The surface defect density and the
electrical resistance of GCS@SiO2 NWs are systematically
modulated by control of H2 gas flow rates during the carbon
shell growth on the SiO2 NWs. From in-depth characterization
of the model catalysts, it is confirmed that the intrinsic catalytic
activity of MoS2–carbon composites for the HER is
improved linearly with the conductance of the carbon supports regardless
of the MoS2 edge site density. However, in the HER polarization
curve, the apparent current density increases in proportion to the
product of the number of MoS2 edge sites and the conductance
of GCS@SiO2 NWs.
We report on the development of Ni-shielded ZnO nanorod (NR) structures and the impact of the Ni layer on the ZnO NR properties. We developed nickel-capped zinc oxide nanorod (ZnO/Ni NR) structures by e-beam evaporation of Ni and the subsequent annealing of the ZnO/Ni core/shell nanostructures. The core/shell NRs annealed at 400 °C showed superior crystalline and emission properties. More interestingly, with the increase of annealing temperature, the crystallinity of the Ni shells over the ZnO NRs gradually changed from polycrystalline to single crystalline. The presence of the Ni layer as a polycrystalline shell completely hindered the light emission and transmission of the ZnO NR cores. Further, the band gap of ZnO NRs continuously decreased with the increase of annealing temperature.
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