Gas Evaporation Method Research Articles

Environmental gas sensing studies using flower-like MoS2 hybrid structure

Molybdenum disulfide (MoS2) is one of the most potent transition metal dichalcogenide (TMDc) material for gas sensing applications due to its various advantageous properties. It exhibits modest electron mobilities, reduced dimensionality, and favorable mechanical properties. The deposition of metal nanoparticles on nanostructured MoS2 leads to the modification in their sensing properties. By keeping in view, present work reports the fabrication of stable MoS2 nanoflowers (MNF) and their hybrids (Au-MoS2 nanoflowers). The hydrothermal approach was used to synthesize MNF nanostructures and in order to form the hybrid Au-MoS2 nanoflower (AuMNF) Au nanoparticle were deposited over MNF by an inert gas evaporation method. X-ray Diffraction and micro–Raman spectroscopy were used to study MNF and AuMNF hybrid structures. XRD found MoS2 1 T-2H mixed-phase. The peak shift and broadening in E1g, J3, and E3g modes for AuMNF hybrids was observed compared to MNF. The flower-like morphology of the pristine and hybrid nanostructures was confirmed via the Scanning electron microscopy (SEM) technique and transmission electron microscopy (TEM). Furthermore, the fabricated samples MNF and AuMNF hybrids were investigated for environmental gas sensing. According to the results of the gas sensing tests, the AuMNF hybrid provides the best sensing response. The gas sensing measurements revealed that the best sensing response is found from the AuMNF hybrid. This hybrid shows a response of 21.2 % in the presence of CO, which is 5.5 times higher than the response of pure MoS2. These findings contribute to a better interpretation of how the resistance of MoS2 nanostructures reacts towards CO gas exposure. These findings contribute to a better interpretation of how the resistance of MoS2 nanostructures reacts towards CO gas exposure.

The Role of Nitrogen Dopants in ZnO Nanoparticle-Based Light Emitting Diodes.

In this work, nitrogen-doped ZnO nanoparticles were synthesized in various conditions by the gas evaporation method with DC arc plasma. Nitrogen concentrations of 6.38 × 1018 cm−3 to 2.6 × 1019 cm−3 were obtained at a chamber pressure of 150 torr, using arc currents of 20 A to 70 A. The intensities of local vibrational modes at 275 cm−1 and 581 cm−1 in the Raman spectra of ZnO nanoparticles showed a dependency on the nitrogen concentration in the ZnO nanoparticles. The ratios of donor–acceptor pair and exciton emissions in the photoluminescence spectra of nitrogen-doped ZnO nanoparticles, and the electroluminescence of light-emitting diodes based on these nanoparticles, were nearly proportional to the Raman peak’s intensity at 275 cm−1. The results indicated that the nitrogen dopants in the ZnO nanoparticles were acting as an acceptor.

Effects of Ambience on Thermal-Diffusion Type Ga-doping Process for ZnO Nanoparticles

Various annealing atmospheres were employed during our unique thermal-diffusion type Ga-doping process to investigate the surface, structural, optical, and electrical properties of Ga-doped zinc oxide (ZnO) nanoparticle (NP) layers. ZnO NPs were synthesized using an arc-discharge-mediated gas evaporation method, followed by Ga-doping under open-air, N2, O2, wet, and dry air atmospheric conditions at 800 °C to obtain the low resistive spray-coated NP layers. The I–V results revealed that the Ga-doped ZnO NP layer successfully reduced the sheet resistance in the open air (8.0 × 102 Ω/sq) and wet air atmosphere (8.8 × 102 Ω/sq) compared with un-doped ZnO (4.6 × 106 Ω/sq). Humidity plays a key role in the successful improvement of sheet resistance during Ga-doping. X-ray diffraction patterns demonstrated hexagonal wurtzite structures with increased crystallite sizes of 103 nm and 88 nm after doping in open air and wet air atmospheres, respectively. The red-shift of UV intensity indicates successful Ga-doping, and the atmospheric effects were confirmed through the analysis of the defect spectrum. Improved electrical conductivity was also confirmed using the thin-film-transistor-based structure. The current controllability by applying the gate electric-field was also confirmed, indicating the possibility of transistor channel application using the obtained ZnO NP layers.

Interfacial interaction of plasmonic nanoparticles (Ag, Au) decorated floweret TiO2 nanorod hybrids for enhanced visible light driven photocatalytic activity

One dimensional TiO2 nanorods (TONRs) hybrids have enormous potential for photocatalytic applications. Integrating TONRs with plasmonic Nanoparticles (PNPs) to form hybrid structures enhances its photocatalytic activity by local surface plasmonic resonance (LSPR) effect. The Present work reports PNPs decorated TONRs for visible light driven photocatalytic activity. PNPs of silver (Ag) and gold (Au) with different sizes are decorated over TONRs to form PNP-TONRs hybrids. The size of Ag and Au PNPs are engineered by using inert gas evaporation method at different vapour pressures. The microRaman studies of hybrids reveal the enhanced Eg mode due to SERS effect. The decoration of Au PNPs with small size PNPs on TONRs have been found efficacious to alter Schottky effect and plasmonic activity. PNPs-TONRs hybrids are further explored for photocatalytic activity. The overall photocatalytic activity of small sized Au based hybrids is better than Ag based hybrids owing to their better Schottky effect and plasmonic activity.

Hydrogen storage properties of Mg–Nb@C nanocomposite: Effects of Nb nanocatalyst and carbon nanoconfinement

The Mg–Nb@C nanocomposite has been synthesized by a reactive gas evaporation method to simultaneously achieve carbon nanoconfinement and add Nb nanocatalyst. The size of Mg particles is range from 14 to 26 nm with average size of 20 nm. The small Nb catalyst about 5 nm are decorated in Mg particles, and the proportion of Nb is about 8 wt%. The amorphous carbon layer with thickness of 2 nm is coated on the surface of Mg–Nb nanocomposite. The nanocomposite can absorb 6.4 wt% H2 and desorb 6.3 wt% H2 in 5 min at 673 K. At 573 K, it can also uptake 5.8 wt% H2 in 10 min and release 4.8 wt% H2 in 60 min. The Ea for hydrogenation and dehydrogenation are reduced to 60.2 and 59.7 kJ mol−1, respectively. Carbon nanoconfinement and Nb nanocatalyst effectively improve the hydrogen sorption kinetic of Mg.

TiCX-decorated Mg nanoparticles confined in carbon shell: Preparation and catalytic mechanism for hydrogen storage

To enhance the hydrogen storage properties of Mg/MgH2, we confine TiCX-decorated Mg nanoparticles (NPs) in 2–3 nm carbon shells through a reactive gas evaporation method. By adjusting the evaporation rate of Mg and Ti, the average particle size of Mg-TiCX@C nanocomposite is controlled below 50 nm, and the content of TiCX is adjusted between 4 and 25 wt%. Among these samples, the Mg88(TiC0.6)12@C nanocomposite with high loading percentage of 88% displays the best hydrogen storage performance. It quickly absorbs 5.5 wt% H2 within 25 min at 523 K and desorbs 4.5 wt% H2 within 60 min at 573 K. The hydrogen storage capacity and kinetics remain stable after ten hydrogenation/dehydrogenation cycles at 523/573 K. The enhanced hydrogen storage kinetics of the nanocomposite is attributed to the synergistic effects of the carbon confinement nanostructure and the catalysis of the nonstoichiometric TiCX decorated on Mg NPs.

COMPARISON OF THE IN VITRO CYTOTOXICITIES OF NITROGEN DOPED (p-TYPE) AND n-TYPE ZINC OXIDE NANOPARTICLES

The use of NPs in the health care field is increasing. Before their biological application, investigating the toxicities of both n-type ZnO nanoparticles (NPs) and nitrogen-doped (“p-type”) NPs is important. Using L929 cells, the cell viability, oxidative stress, apoptosis induction, inflammatory responses, and cellular uptake were assayed 24[Formula: see text]h after the addition of n-type ZnO NPs and nitrogen-doped NPs (which act as p-type) (25[Formula: see text][Formula: see text]g/mL). The ZnO NPs were fabricated using a gas evaporation method. Increased H2O2 generation and decreased levels of glutathione were more evident in with n-type than in those treated with nitrogen-doped (“p-type”) ZnO NPs. Caspase-3/-7 activity was higher in cells treated with n-type ZnO NPs than in those treated with nitrogen-doped (“p-type”) NPs. Elevated levels of TNF-[Formula: see text] and IL-1[Formula: see text] were observed in cell culture supernatants: IL-1[Formula: see text] levels were higher in n-type ZnO NPs than nitrogen-doped (“p-type”) NPs. The cellular Zn uptake of n-type ZnO NPs was higher than nitrogen-doped (“p-type”) NPs. These findings show that n-type ZnO NPs have higher cytotoxicity than nitrogen-doped (“p-type”) ZnO NPs. This may be due to a reductive effect of n-type ZnO NPs that induces higher free radical production, reactive oxygen species (ROS) generation, and cellular uptake of this type of ZnO NPs.

27p-YC-10 ガス中蒸発法による有機化合物微粒子ペリレンの生成

27p-YC-10 ガス中蒸発法による有機化合物微粒子ペリレンの生成

A-few-second synthesis of silicon nanoparticles by gas-evaporation and their self-supporting electrodes based on carbon nanotube matrix for lithium secondary battery anodes

Rapid gas-evaporation method is proposed and developed, which yields Si nanoparticles (SiNPs) in a few seconds at high yields of 20%–60% from inexpensive and safe bulk Si. Such rapid process is realized by heating the Si source to a temperature ≥2000 °C, much higher than the melting point of Si (1414 °C). The size of SiNPs is controlled at tens to hundreds nanometers simply by the Ar gas pressure during the evaporation process. Self-supporting films are fabricated simply by co-dispersion and filtration of the SiNPs and carbon nanotubes (CNTs) without using binders nor metal foils. The half-cell tests showed the improved performances of the SiNP-CNT composite films as anode when coated with graphitic carbon layer. Their performances are evaluated with various SiNP sizes and Si/CNT ratios systematically. The SiNP-CNT film with a Si/CNT mass ratio of 4 realizes the balanced film-based capacities of 618 mAh/gfilm, 230 mAh/cm3, and 0.644 mAh/cm2 with a moderate Si-based performance of 863 mAh/gSi at the 100th cycle.

Hydrogen Storage of Pd/Mg composite Nanoparticles Fabricated by Gas Evaporation Method

Hydrogen Storage of Pd/Mg composite Nanoparticles Fabricated by Gas Evaporation Method

P-Channel and n-Channel Thin-Film-Transistor Operation on Sprayed ZnO Nanoparticle Layers

Both n-channel and p-channel thin-film transistors have been realized on ZnO nanoparticle (NP) layers sprayed onto quartz substrates. In this study, nitrogen-doped ZnO-NPs were synthesized using an arc-discharge-mediated gas-evaporation method that was recently developed. Sprayed NP layers were characterized by scanning electron microscopy and Hall effect measurements. It was confirmed that p-type behaving NP layers can be obtained using ZnO-NPs synthesized with lower chamber pressure, whereas n-type conductivity can be obtained with higher chamber pressure. pn-junction diodes were also tested, resulting in clear rectifying characteristics. The possibility of particle-process-based ZnO-NP electronics was confirmed.

Hydrogen storage property of materials composed of Mg nanoparticles and Ni nanoparticles fabricated by gas evaporation method

We have fabricated the materials composed of the Mg and the Ni nanoparticles and clarified the hydrogen storage property by using TEM, XPS and QCM. The Mg and the Ni nanoparticles have been fabricated by gas evaporation method and been mixed. The diameters of the Mg and the Ni nanoparticles have been estimated as 20.0 ± 8.4 and 4.7 ± 2.0 nm, respectively. And the Mg and the Ni nanoparticles as prepared sample possess almost clean surface. This sample can absorb the hydrogen under atmospheric pressure at 30 °C before completely oxidized. However, the hydrogen storage ability of this sample has been lost by the adsorption of residual gases even under vacuum condition in several hours after the end of fabrication. Due to the Mg oxide shell on the surface of the Mg nanoparticles is formed by the residual gases, the hydrogenation of the Mg nanoparticles are hindered.

Magnetic order of Au nanoparticle with clean surface

Au nanoparticles, which are kept in vacuum after the preparation by gas evaporation method, show ferromagnetism even in 1.7nm in diameter. The intrinsic magnetism is examined by detecting the disappearance of spontaneous magnetization in Au bulk prepared by heating the nanoparticles without exposure to the air. The temperature dependence of spontaneous magnetization is not monotonic and the increase in magnetization is observed after Au nanoparticles are exposed to the air. The magnetic behavior can be interpreted by the ferrimagnetic-like core–shell structure with shell thickness of 0.16±0.01nm and magnetic moment of (1.5±0.1)×10−2μB/Au atom, respectively.

Hydrogen storage of binary nanoparticles composed of Mg and Pd

The hydrogen storage property of the binary nanoparticles composed of Mg and Pd has been investigated by the QCM technique without the exposure to the air. The two types of nanoparticles have been fabricated by the gas evaporation method with the He gas. The one is the nanoparticles composed of the both Mg and Pd atoms (Mg–Pd NPs) and the other one is the composite of the Mg and Pd nanoparticles (Mg NPs-Pd NPs). Both the Mg–Pd NPs and the Mg NPs-Pd NPs can absorb the hydrogen under the room temperature and 1 atm of H2 gas. However, the desorptions of the hydrogen have not been observed about the both samples. We have also studied the chemical state of the NPs by XPS and XAFS. The XAFS analyses have revealed that the MgH2 in the NPs can not be dehydrogenated at the room temperature even if the catalytic effect of the Pd.

XAFS and XPS study of hydro‐/dehydrogenation reaction of Mg–Pd nanoparticles

The nanoparticles composed of Mg and Pd atoms (Mg–Pd NPs) have been fabricated by the gas evaporation method, and the variation of the chemical state during hydro‐/dehydrogenations has been investigated by X‐ray photoelectron spectroscopy (XPS) and in‐situ X‐ray absorption fine structure (XAFS) analyses. Both XPS and XAFS spectra have indicated that the Mg–Pd NPs contain the chemical state of the metallic Pd and Mg–Pd alloy phases. The Mg–Pd alloy phase has been identified as MgPd and Mg6Pd by the Pd K‐edge EXAFS analysis. The hydrogen release of the Mg–Pd NPs has not been observed after first hydrogenation due to the migration of Mg toward the surface of the Mg–Pd NPs during the hydrogen storage. This irreversible migration has led the inhibition of the hydrogen diffusion into the surface from the inside of the Mg–Pd NPs. Copyright © 2014 John Wiley & Sons, Ltd.

Powder metallurgy on its way to nanocrystalline structures

Metallic and ceramic dense nanocrystalline (nc–)materials with average grain sizes of about 5 to 100 nm may be produced by means of powder technology at relatively low temperatures. This is achieved by using nano–dispersed, i.e. highly sinter–active starting powders. It is the extremely high grain–/phase–boundary area that determines the unusual properties of the resultant PM–components. The various suitable PM–methods for the production of pure as well as composite nc–materials are shortly reviewed including the sol–gel–process, mechanical alloying and the inert gas evaporation method. Some of the fascinating potentials of PM–fabricated nc–materials due to their peculiar magnetic, electronic and mechanical behaviour are elucidated.

Hydrogen storage property of Ni nanoparticles fabricated by the gas evaporation method

We have fabricated the Ni nanoparticles with a clean surface by the gas evaporation method and clarified the hydrogen storage property by using atomic force microscope (AFM), X‐ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM) measurements. The diameter has been estimated as 4.0 ± 1.5 nm by AFM observation. The Ni nanoparticles possess a clean surface, because the surface chemical state has been confirmed as mainly metallic state by XPS. The hydrogen storage property has been investigated by QCM from the vacuum to the atmospheric pressure of the hydrogen at 300 K. The plateau pressure of the Ni nanoparticles and a maximum hydrogen storage capacity are about 7 Torr and H/Ni = 0.56, respectively. And the hydrogen release from the Ni nanoparticles has not been observed by QCM. The hydrogen adsorption/desorption reaction have also been observed as the plateau like pressure by QCM. These results indicate that (i) the plateau pressure of Ni is decreased by the nanosizing of the material, (ii) the large specific surface area of the Ni nanoparticles makes it possible to observe the adsorption/desorption reaction and (iii) the Ni hydride is stable under the vacuum condition. The chemical shift of Ni 2p3/2 has not been observed in the XPS spectrum between before and after exposure to the hydrogen. This result implies that there is no strong chemical bonding between Ni and hydrogen or the hydrogen in the lateral surface has been released. Copyright © 2014 John Wiley & Sons, Ltd.

Interface structure of niobium carbide-encapsulating carbon nanocapsules studied by high-resolution transmission electron microscopy.

Carbon nanocapsules (CNCs) encapsulating niobium carbide (NbC) crystals with a sodium chloride structure were synthesized via a gas-evaporation method by arc-discharge heating. CNCs were observed by high-resolution transmission electron microscopy, and the atomic configurations at the graphene/NbC interfaces were investigated. The NbC crystals within the nanospaces of CNCs were truncated by the {100}, {110}, and (111} facets and were coated with several graphene layers. It was found that the interlayer spacings for the graphene{0001}/NbC{100} and graphene{0001}/NbC{110} interfaces were 0.33 +/- 0.05 nm, whereas those for the graphene{0001}/{111}NbC interfaces were 0.28 +/- 0.05 nm.

The atomic configuration of graphene/vanadium carbide interfaces in vanadium carbide-encapsulating carbon nanocapsules.

Carbon nanocapsules (CNCs) encapsulating vanadium carbide (VC) nanocrystals with a NaCI structure were synthesized by a gas-evaporation method using arc-discharge heating. The CNCs were observed by high-resolution transmission electron microscopy. The VC nanocrystals within the nanospaces of CNCs were truncated by low-index facets and were coated with several graphene layers, forming graphene/VC interfaces. The atomic configuration and interlayer spacings at the interfaces were found.

Suitability of GaP nanoparticles as a surface-assisted laser desorption/ionization mass spectroscopy inorganic matrix and their soft ionization ability

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) using GaP nanoparticles (NPs) prepared by a gas evaporation method was investigated on poly(ethylene glycol)s (PEGs). The mass spectra of PEG and survival yield measurements suggested that larger GaP NPs have a quite high soft ionization ability.