Two-dimensional (2D) molybdenum disulphide (MoS2) atomic layers have a strong potential to be used as 2D electronic sensor components. However, intrinsic synthesis challenges have made this task difficult. In addition, the detection mechanisms for gas molecules are not fully understood. Here, we report a high-performance gas sensor constructed using atomic-layered MoS2 synthesised by chemical vapour deposition (CVD). A highly sensitive and selective gas sensor based on the CVD-synthesised MoS2 was developed. In situ photoluminescence characterisation revealed the charge transfer mechanism between the gas molecules and MoS2, which was validated by theoretical calculations. First-principles density functional theory calculations indicated that NO2 and NH3 molecules have negative adsorption energies (i.e., the adsorption processes are exothermic). Thus, NO2 and NH3 molecules are likely to adsorb onto the surface of the MoS2. The in situ PL characterisation of the changes in the peaks corresponding to charged trions and neutral excitons via gas adsorption processes was used to elucidate the mechanisms of charge transfer between the MoS2 and the gas molecules.

The establishment of covalent junctions between carbon nanotubes (CNTs) and the modification of their straight tubular morphology are two strategies needed to successfully synthesize nanotube-based three-dimensional (3D) frameworks exhibiting superior material properties. Engineering such 3D structures in scalable synthetic processes still remains a challenge. This work pioneers the bulk synthesis of 3D macroscale nanotube elastic solids directly via a boron-doping strategy during chemical vapour deposition, which influences the formation of atomic-scale “elbow” junctions and nanotube covalent interconnections. Detailed elemental analysis revealed that the “elbow” junctions are preferred sites for excess boron atoms, indicating the role of boron and curvature in the junction formation mechanism, in agreement with our first principle theoretical calculations. Exploiting this material’s ultra-light weight, super-hydrophobicity, high porosity, thermal stability, and mechanical flexibility, the strongly oleophilic sponge-like solids are demonstrated as unique reusable sorbent scaffolds able to efficiently remove oil from contaminated seawater even after repeated use.

We report the production of a two-dimensional (2D) heterostructured gas sensor. The gas-sensing characteristics of exfoliated molybdenum disulfide (MoS2) connected to interdigitated metal electrodes were investigated. The MoS2 flake-based sensor detected a NO2 concentration as low as 1.2 ppm and exhibited excellent gas-sensing stability. Instead of metal electrodes, patterned graphene was used for charge collection in the MoS2-based sensing devices. An equation based on variable resistance terms was used to describe the sensing mechanism of the graphene/MoS2 device. Furthermore, the gas response characteristics of the heterostructured device on a flexible substrate were retained without serious performance degradation, even under mechanical deformation. This novel sensing structure based on a 2D heterostructure promises to provide a simple route to an essential sensing platform for wearable electronics.

Here we construct mechanically flexible and optically transparent thin film solid state supercapacitors by assembling nano-engineered carbon electrodes, prepared in porous templates, with morphology of interconnected arrays of complex shapes and porosity. The highly textured graphitic films act as electrode and current collector and integrated with solid polymer electrolyte, function as thin film supercapacitors. The nanostructured electrode morphology and the conformal electrolyte packaging provide enough energy and power density for the devices in addition to excellent mechanical flexibility and optical transparency, making it a unique design in various power delivery applications.

Graphene was grown directly on porous nickel films, followed by the growth of controlled lengths of vertical carbon nanotube (CNT) forests that seamlessly emanate from the graphene surface. The metal-graphene-CNT structure is used to directly fabricate field-emitter devices and double-layer capacitors. The three-dimensional nanostructured hybrid materials, with better interfacial contacts and volume utilization, can stimulate the development of several energy-efficient technologies.

Two-dimensional (2D) molybdenum disulfide (MoS2) atomic layers have a strong potential to be adopted for 2D electronic components due to extraordinary and novel properties not available in their bulk foams. Unique properties of the MoS2, including quasi-2D crystallinity, ultrahigh surface-to-volume, and a high absorption coefficient, have enabled high-performance sensor applications. However, implementation of only a single-functional sensor presents a limitation for various advanced multifunctional sensor applications within a single device. Here, we demonstrate the charge-transfer-based sensitive (detection of 120 ppb of NO2) and selective gas-sensing capability of the chemical vapor deposition synthesized MoS2 and good photosensing characteristics, including moderate photoresponsivity (∼71 mA/W), reliable photoresponse, and rapid photoswitching (<500 ms). A bifunctional sensor within a single MoS2 device to detect photons and gas molecules in sequence is finally demonstrated, paving a way toward a versatile sensing platform for a futuristic multifunctional sensor.

Gold and silver nanoparticles and nanostructures exhibit plasmon resonances that result in strong scattering and absorption of light, as well as enhanced optical fi elds near the metal surface. The resonant fi eld enhancement dramatically enhances the weak Raman scattering signals from molecules near the metal surface. [ 1 ] This effect, called surface enhanced Raman scattering (SERS), has been widely pursued as a molecular sensing technology over the past decade. [ 2 , 3 ] SERS is non-destructive, suffi ciently sensitive for single molecule detection, and provides inherent molecular specifi city since it yields molecular vibrational spectra. While fi eld enhancement occurs over an entire nanostructure surface, SERS signals are strongest from small gaps between nanoparticles referred to as "hot spots" where the fi eld enhancement is maximal. [ 4 , 5 ] Most SERS work to date has focused on detection with substrates that are designed to maximize the density, sensitivity, and reproducibility of hot spots in order to give the strongest possible SERS signal. Many substrates have been developed which refl ect the variety of nanofabrication, synthesis, and assembly strategies that have emerged over the past decade. These include semiconducting nanowires, [ 6 ] aggregated colloids, [ 7 , 8 ] colloidal lithography, [ 9 , 10 ] soft lithography, [ 11 , 12 ] e-beam lithography, [ 13 ] and colloidal assembly. [ 14 , 15 ] Most of the substrates consist of nanostructured gold or silver on a fl at substrate. Some reports describe substrates with increased surface roughness to increase the number of hot spots, including aligned carbon nanotube substrates that support silver nanoparticles. [ 16 ] These substrates were found to provide highly sensitive detection. However, optical scattering and light collection occur in a three dimensional focal volume. Therefore, to maximize the quantity of scattered light generated and detected, SERS substrates should contain hot spots in a large three dimensional volume that is matched to the optics of the SERS instrumentation. Three dimensional substrates have been fabricated and tested based on porous silicon, microfabricated silicon, and porous gold. [17][18][19][20] These have indeed improved the detection limit for small molecules like trinitrotoluene (TNT). Therefore, it is desirable to create densely packed metal nanostructures with nanogaps to form plentiful hot spots for better SERS performance. [21][22][23] In the present study, we describe the fabrication of a structurally tunable 3D SERS substrate based on vertically aligned CNTs. Vertically aligned CNTs provide a new paradigm to realize three dimensional SERS substrates with high nanoparticle density. The vertically aligned CNTs were synthesized on a SiO 2 substrate by water-assisted chemical vapor deposition (CVD). The resulting vertically aligned CNTs were several millimeters long and were composed of a mixture of double-and triple-walled nanotubes. [ 24 , 25 ] A gold fi lm (50 nm thickness) was deposited on top of the CN...

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.