Here, we design and develop high-power electric double-layer capacitors (EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructured electrodes. 3-D hybrid nanostructured electrodes consisting of vertically aligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs) were synthesized by a combination of anodization and chemical vapor deposition techniques. A 3-D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device.

Here, we report that Nb doping of two-dimensional (2D) MoSe layered nanomaterials is a promising approach to improve their gas sensing performance. In this study, Nb atoms were incorporated into a 2D MoSe host matrix, and the Nb doping concentration could be precisely controlled by varying the number of NbO deposition cycles in the plasma enhanced atomic layer deposition process. At relatively low Nb dopant concentrations, MoSe showed enhanced device durability as well as NO gas response, attributed to its small grains and stabilized grain boundaries. Meanwhile, an increase in the Nb doping concentration deteriorated the NO gas response. This might be attributed to a considerable increase in the number of metallic NbSe regions, which do not respond to gas molecules. This novel method of doping 2D transition metal dichalcogenide-based nanomaterials with metal atoms is a promising approach to improve the performance such as stability and gas response of 2D gas sensors.

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We present the fabrication and characterization of nanoscale electrical interconnect test structures constructed from aligned single-wall carbon nanotubes using a template-based fluidic assembly process. This CMOS-friendly process enables the formation of highly aligned parallel nanotube interconnect structures on SiO(2)/Si substrates of widths and lengths that are limited only by lithographical limits and, hence, can be easily integrated onto existing Si-based platforms. These structures can withstand current densities of approximately 10(7) A.cm(-2), comparable or better than copper at similar dimensions. Both the nanotube alignment and failure current density improve with decreasing structure width. In addition, we present a novel Pt nanocluster decoration method that drastically decreases the resistivity of the test structures. Ab initio density functional theory calculations indicate that the increase in conductivity of the nanotubes is caused by an increase in conduction channels close to their Fermi levels due to the platinum nanocluster decoration, with a possible conversion of the semiconducting single-wall carbon nanotubes into metallic ones. These results reflect a huge step toward the proposed replacement of copper-based interconnects with carbon nanotubes at gigascale integration levels.

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Here we report the highly effective detection of hydrogen sulfide (H2S) gas by redox reactions based on single-walled carbon nanotubes (SWCNTs) functionalized with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as a catalyst and we also discuss the important role of water vapor in the electrical conductivity of SWCNTs during the sensing of H2S molecules. To explore the H2S sensing mechanism, we investigate the adsorption properties of H2S on carbon nanotubes (CNTs) and the effects of the TEMPO functionalization using first-principles density functional theory (DFT) and we summarize current changes of devices resulting from the redox reactions in the presence of H2S. The semiconducting-SWCNT (s-SWCNT) device functionalized with TEMPO shows a very high sensitivity of 420% at 60% humidity, which is 17 times higher than a bare s-SWCNT device under dry conditions. Our results offer promising prospects for personal safety and real-time monitoring of H2S gases with the highest sensitivity and low power consumption and potentially at a low cost.

Single-walled carbon nanotube (SWCNT) network architectures combined with flexible mediums (especially polymers) are strong candidates for functional flexible devices and composite structures requiring the combination of unique electronic, optical, and/or mechanical properties of SWCNTs and polymer materials. However, to build functional flexible devices with SWCNTs, it is required to have abilities to assemble and incorporate SWCNTs in desired locations, orientations, and dimensions on/inside polymer substrates. Here, we present unique two- and three-dimensional SWCNT network-polymer hybrid architectures by combining unprecedented control over growth, assembly, and transfer processes of SWCNTs. Several SWCNT architectures have been built on polymer materials ranging from two-dimensional suspended SWCNT microlines on PDMS microchannels to three-dimensional "PDMS-vertically aligned SWCNTs-PDMS" sandwich structures. Also a combined lateral SWCNT microline and vertically aligned SWCNT flexible device was demonstrated with good electrical conductivity and low junction resistance. The results reported here open the pathway for the development of SWCNT-based functional systems in various flexible device applications.

The excitonic behavior in two-dimensional (2D) heterostructures of transition metal dichalcogenide atomic layers has attracted much attention. Here, we report, for the first time, the ultrafast behavior of charge carriers in heterostructure of metal (NbSe2) and semiconductor (WSe2) atomic layers via ultrafast spectroscopy. We observe a blue-shift of the excited-state absorption peak in time-resolved absorption spectra with time delays in both the as-grown semiconducting WSe2 and the metal–semiconductor heterostructure. However, the heterostructure shows a clear difference in the peak position and relaxation time of its electrons. This result indicates higher excited energy states in WSe2 in the presence of the NbSe2 metallic layer contact and implies the existence of interlayer electron quenching from WSe2 to NbSe2 layers. The heterostructure shows a shorter time scale in the peak rise time compared to bare WSe2, due to interfacial defects between WSe2 and NbSe2 layers. The results offer a better understanding of the optoelectronic properties of 2D heterostructure interfaces.