Wearable gas sensors are essential for real-time monitoring of personal exposure, yet achieving high sensitivity at room temperature while maintaining mechanical compliance remains a significant challenge. Here, we report a hierarchical graphene nanowall (GNW) nanomesh that integrates material-specific transport characteristics with a three-dimensional (3D) porous architecture for enhanced gas-sensing performance. The GNW nanomesh is realized by directly growing vertically oriented graphene nanowalls on a flexible polymer nanomesh using a low-temperature plasma-enhanced chemical vapor deposition process enabled by a thermally robust parylene-coated polyimide substrate. The resulting 3D-on-3D architecture provides high accessibility of active sites and mechanically compliant pathways suitable for wearable applications. Compared to planar GNWs, the hierarchical nanomesh exhibits a sixfold enhancement in sensitivity and faster response under room-temperature operation. Particle-based simulations suggest that confined geometries within GNWs promote localized molecular trajectories and increased collision events, consistent with the observed performance enhancement. Integration into a wearable smart mask further demonstrates stable real-time detection of NO2 over extended operation. This work highlights that combining intrinsic material transport characteristics with hierarchical nanoarchitectural design offers an effective strategy for advancing wearable gas sensing beyond conventional surface-area-driven approaches.

Carbon nanowalls (CNWs), which have high mobility, high surface area and high porosity, generally have high potential as gas sensing materials, but poor gas detection performance has been reported due to low response and recovery. To enhance the sensing performance of a chemiresistive gas sensor based on CNWs, a metallic catalyst and micro heating system have been used. Ag NPs were decorated onto CNWs patterned for fabrication of a gas sensor platform with microheater. Diverse characteristics of functionalized CNWs by Ag NPs were investigated via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. Ag NPs or clusters were optically observed among a significant number of pores on the surface of CNWs, resulting in change in pore size. Also, a certain evidence of Ag NPs was demonstrated by surface-enhanced Raman scattering (SERS), causing a positive and negative shift in the Raman band of CNWs. In terms of gas-sensing perfor-mance, a greater amount of Ag NPs showed highly improved sensing signal for NH3 and NO2 gas from 25 to 100 ppm compared to pristine conditions. The microheater also improved the poor recovery rate of CNWs. Consequently, the combined gas sensing platform with metallic catalyst and microheating system showed significantly enhanced gas sensing performance.(c) 2022 Published by Elsevier B.V.

Carbon nano wall (CNW) characterized by a large specific surface area were used, and graphite slurry was applied through a casting process to improve durability. To improve adhesion between the current collector (copper foil) and CNWs, a titanium nitride (TiN) layer was deposited using the RF magnetron sputtering method. CNWs were then grown by injecting methane (CH4) and hydrogen (H2) using a microwave plasma enhanced chemical vapor deposition (PECVD) system. The casting process was performed by making the height of the graphite slurry uniform. Afterwards, heat treatment process was performed at 70℃, 75℃, and 80℃ on a hot plate to improve durability. Field emission scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to confirm the presence of CNWs in the casting process. A Raman spectroscopy was used to analyze the structural properties of anode materials. The improvement in the durability of the anode material was confirmed by analyzing the electrochemical properties. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were performed to characterize the lithium-ion battery. The cyclic voltammetry (CV) of the graphite slurry was measured at 20 cycles, which increased by about 8 cycles compared to other temperatures. As a result of electrochemical impedance spectroscopy, the Rct value was 25 Ohm at 75℃ heat treatment, which was about 4 times smaller than other temperatures.

Surface-enhanced Raman scattering (SERS) is a highly sensitive technique for detecting DNA, proteins, and single molecules. The design of SERS substrates plays a crucial role, with the density of hotspots being a key factor in enhancing Raman spectra. In this study, we employed carbon nanowall (CNW) as the nanostructure and embedded plasmonic nanoparticles (PNPs) to increase hotspot density, resulting in robust Raman signals. To enhance the CNW's performance, we functionalized it via oxygen plasma and embedded silver nanoparticles (Ag NPs). The authors evaluated the substrate using rhodamine 6G (R6G) as a model target molecule, ranging in concentration from 10-6 M to 10-10 M for a 4 min exposure. Our analysis confirmed a proportional increase in Raman signal intensity with an increase in concentration. The CNW's large specific surface area and graphene domains provide dense hotspots and high charge mobility, respectively, contributing to both the electromagnetic mechanism (EM) and the chemical mechanism (CM) of SERS.

The fabrication of high-capacity, binder-free Li–ion battery anodes using a simple and efficient manufacturing process was reported in this research. The anode material for lithium–ion batteries utilized is a combination of two-dimensional (2D) carbon nanowalls (CNWs) and Cu nanoparticles (improved rate performance and capacity retention) or Si (high capacity) nanoparticles. A methane (CH4) and hydrogen (H2) gas mixture was employed to synthesize CNWs on copper foil through microwave plasma-enhanced chemical vapor deposition (PECVD). The Cu or Si nanoparticles were then deposited on the CNW surface using an RF magnetron sputtering equipment with four-inch targets. To analyze the electrochemical performance of the LIBs, CR2032 coin-type cells were fabricated using anode materials based on CNWs and other components. It was confirmed that the Cu−CNW demonstrates improved rate performance, increased specific capacity, and capacity retention compared with traditional anodes. Additionally, CNW combined with Si nanoparticles has enhanced the capacity of LIB and minimized volume changes during LIB operation.

Carbon is a material with interesting properties which exists in large quantities on Earth, so many studies involving carbon have been conducted. In particular, nano-sized carbon allotropes, referred to as carbon nanomaterials, comprise the subject of various studies currently underway. The electrical, chemical, physical properties of carbon nanowalls (CNWs) are modified by parameters such as surface density, height and thickness. These characteristics have significant effects on CNWs and can be adjusted as a growth interlayer. It was confirmed that the molybdenum disulfide (MoS2) interlayer synthesized in this paper by radio frequency (RF) magnetron sputtering altered the morphological characteristics of the CNWs, including its shaped edge, pores diameter and density. We provide interesting results through FE-SEM, EDS and Raman analysis in this paper. Based on the Raman analysis, both the D-peak of carbon and the ID/IG ratio decreased. Through this study, the effect of MoS2 on the morphological characteristics of CNWs was confirmed.

Recently, as air pollution and particulate matter worsen, the importance of a platform that can monitor the air environment is emerging. Especially, among air pollutants, nitrogen dioxide (NO2) is a toxic gas that can not only generate secondary particulate matter, but can also derive numerous toxic gases. To detect such NO2 gas at low concentration, we fabricated a GNWs/NiO-WO3/GNWs heterostructure-based gas sensor using microwave plasma-enhanced chemical vapor deposition (MPECVD) and sputter, and we confirmed the NO2 detection characteristics between 10 and 50 ppm at room temperature. The morphology and carbon lattice characteristics of the sensing layer were investigated using field emission scanning electron microscopy (FESEM) and Raman spectroscopy. In the gas detection measurement, the resistance negative change according to the NO2 gas concentration was recorded. Moreover, it reacted even at low concentrations such as 5–7 ppm, and showed excellent recovery characteristics of more than 98%. Furthermore, it also showed a change in which the reactivity decreased with respect to humidity of 33% and 66%.

In this study, the characteristics of functional films were investigated according to the number of coatings and their heat treatment times. The functional coating films were deposited on glass substrates made of the same material as the cover glass of photovoltaic (PV) modules. Each film was coated once by brushing with a special silica-based solution, and each heat treatment was done using a hot-air fan for 2 min at 300 °C. The substrates were coated once, twice, and thrice, respectively, and were annealed once, twice, and thrice by drying and cooling alternately. The specimens were then analyzed for their anti-pollution properties, contact angles, light transmittance, and mechanical properties. The anti-pollution function was confirmed through a self-cleaning test, while the contact angle and light transmittance were examined using special equipment. Mechanical properties, including hardness and adhesion, were confirmed using the standard hardness testing method (ASTM D3363) such as those using an H-9H, F, HB, or B-6B pencil (Mitsubishi, Japan) and a standard adhesion testing method (ASTM D3359). It was confirmed that the film coated once yielded a very low contact angle of 8.9° and very good anti-pollution properties. Its adhesion and strength also showed high values of 5B and 9H, respectively.