The effect of pore structure of zeolite on the adsorption of VOCs and their desorption properties by microwave heating

Mordenite and X- or Y-type faujasite were used to remove volatile organic compounds (VOCs) by adsorption at 25 °C. A microwave heating desorption system was applied for pollutant adsorbent regeneration. Studies were focused on the relationship between the adsorption and/or desorption behavior of selected VOCs (benzene, toluene, o-, m-, p-xylene, methanol, ethanol, iso-propanol, and methylethylketone: MEK) and the physicochemical properties of the zeolites (i.e. acidity, Si/Al ratio, crystal structure, pore structure, surface area, and pore volume) in this work. It was shown that the adsorption behavior of mordenite zeolites with low surface area depended on its crystal structure, while the faujasite zeolites with large surface area depended on the mesopore volume. Faujasite zeolites showed the greatest adsorption capacity for the selected VOCs. It was also shown that the mesopore volume with ink-bottle pores was advantageous for adsorption and, contrarily, the mesopore volume with cylindrical mesopores was advantageous for VOC desorption and zeolite regeneration. High efficiency desorption of VOCs was obtained using microwave heating. The highest microwave heating desorption efficiency was obtained with molecular sieve 13X due to the cylindrical pore structure.Keywords: Adsorption, Desorption, Volatile organic compounds (VOCs), Microwave heating, Zeolit

Bimetallic Pt–Au Nanocatalysts on ZnO/Al₂O₃/Monolith for Air Pollution Control

The catalytic activity of a monolithic catalyst with nanosized Pt and Au particles on ZnO/Al₂O₃ (Pt-Au/ZnO/Al₂O₃/M) prepared by a wash-coat method was examined, specifically for toluene oxidation. FE-SEM image showed clearly the formation of a ZnO/Al₂O₃ layer on the monolith. Nanosized Pt-Au particles on ZnO/Al₂O₃/M with different sizes could be found in the Pt-Au/ZnO/Al₂O₃/M catalyst. The conversion of toluene decreased with increasing toluene concentration and was also largely affected by the feed flow rate The Pt-Au/ZnO/Al₂O₃/M catalysts prepared in this work have almost the same activity (molecules of toluene per second) compared with a powder Pt-Au/ZnO/Al₂O₃ catalyst with the same loadings of Pt and Au components; thus this catalyst could be used in controlling air pollution with very low concentrations and high flow rate.Keywords: Wash-coat, ZnO/Al₂O₃, Monolithic Catalyst, Nanosized Pt-Au Particle, Toluene Oxidatio

A study on utilization of stainless steel wire cloth as a catalyst support

In this work, stainless steel wire cloth (SSWC) for metallic support was thermally treated to increase the adhesive strength of Al₂O₃ by improving superficial roughness. After coating Al₂O₃ on SSWC, Pt particles as a catalytic component were deposited on the Al₂O₃/SSWC. These supports and catalysts were characterized by N₂ gas adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS), and scanning transmission electron microscopy (STEM). The catalytic performance was tested in the ethylene oxidation. The effect of space velocity (GHSV = 2000–8000 h⁻¹) at different temperatures (190 °C and 210 °C) and reproducibility were investigated. The superficial roughness of SSWC was markedly increased by thermal oxidation at 800 °C for 12 h, and good adherence of Al₂O₃ to the SSWC was observed. The obtained Pt/Al₂O₃/SSWC800 catalyst showed excellent catalytic activity in the ethylene oxidation and showed a good reproducibility and stability even after repeated use.Keywords: Ethylene oxidation, SEM, Metallic support, Thermal treatmen

Origin of multi-level switching and telegraphic noise in organic nanocomposite memory devices.

The origin of negative differential resistance (NDR) and its derivative intermediate resistive states (IRSs) of nanocomposite memory systems have not been clearly analyzed for the past decade. To address this issue, we investigate the current fluctuations of organic nanocomposite memory devices with NDR and the IRSs under various temperature conditions. The 1/f noise scaling behaviors at various temperature conditions in the IRSs and telegraphic noise in NDR indicate the localized current pathways in the organic nanocomposite layers for each IRS. The clearly observed telegraphic noise with a long characteristic time in NDR at low temperature indicates that the localized current pathways for the IRSs are attributed to trapping/de-trapping at the deep trap levels in NDR. This study will be useful for the development and tuning of multi-bit storable organic nanocomposite memory device systems

Suppressing Diffusion-Mediated Exciton Annihilation in 2D Semiconductors Using the Dielectric Environment

Atomically thin semiconductors such as monolayer MoS2 and WS2 exhibit nonlinear exciton-exciton annihilation at notably low excitation densities (below ~10 excitons/um2 in MoS2). Here, we show that the density threshold at which annihilation occurs can be tuned by changing the underlying substrate. When the supporting substrate is changed from SiO2 to Al2O3 or SrTiO3, the rate constant for second-order exciton-exciton annihilation, k_XX [cm2/s], is reduced by one or two orders of magnitude, respectively. Using transient photoluminescence microscopy, we measure the effective room-temperature exciton diffusion coefficient in chemical-treated MoS2 to be D = 0.06 +/- 0.01 cm2/s, corresponding to a diffusion length of LD = 350 nm for an exciton lifetime of {\tau} = 20 ns, which is independent of the substrate. These results, together with numerical simulations, suggest that the effective exciton-exciton annihilation radius monotonically decreases with increasing refractive index of the underlying substrate. Exciton-exciton annihilation limits the overall efficiency of 2D semiconductor devices operating at high exciton densities; the ability to tune these interactions via the dielectric environment is an important step toward more efficient optoelectronic technologies featuring atomically thin materials

Simulated microgravity with floating environment promotes migration of non-small cell lung cancers

A migration of cancer is one of the most important factors affecting cancer therapy. Particularly, a cancer migration study in a microgravity environment has gained attention as a tool for developing cancer therapy. In this study, we evaluated the proliferation and migration of two types (adenocarcinoma A549, squamous cell carcinoma H1703) of non-small cell lung cancers (NSCLC) in a floating environment with microgravity. When we measured proliferation of two NSCLCs in the microgravity (MG) and ground-gravity (CONT), although initial cell adhesion in MG was low, a normalized proliferation rate of A549 in MG was higher than that in CONT. Wound healing results of A549 and H1703 showed rapid recovery in MG; particularly, the migration rate of A549 was faster than that of H1703 both the normal and low proliferating conditions. Gene expression results showed that the microgravity accelerated the migration of NSCLC. Both A549 and H1703 in MG highly expressed the migration-related genes MMP-2, MMP-9, TIMP-1, and TIMP-2 compared to CONT at 24 h. Furthermore, analysis of MMP-2 protein synthesis revealed weaker metastatic performance of H1703 than that of A549. Therefore, the simulated microgravity based cancer culture environment will be a potential for migration and metastasis studies of lung cancers

Visible-light-sensitive nanoscale Au-ZnO photocatalysts

The role of gold nanoparticles supported on ZnO in photocatalytic activity for dye degradation was investigated. To do this, gold nanoparticles supported on ZnO (Au-ZnO) were prepared using a simple co-precipitation method. The prepared nanocatalyst was characterized by high resolution transmission electron microscopy, X-ray diffraction, temperature programmed reduction, X-ray photoelectron spectroscopy, ultraviolet-visible absorption, and photoluminescence. The photocatalytic activity of Au-ZnO was examined by the degradation of methylene blue in aqueous solution using a light source that has more than 95 % (i.e. energy) of emitted photons between 400 and 800 nm. Highly enhanced photocatalytic degradation of methylene blue in air at room temperature was observed from these Au-ZnO nanocatalysts with gold particle size ranging from 2-7 nm, with an average size of 3.8 nm. The observed rate constant for MB degradation on Au-ZnO was 0.0118 min⁻¹, compared to 0.0007 min⁻¹ for pure ZnO. Furthermore, the charge transfer pathway for degradation of methylene blue in the Au-ZnO is suggested.Keywords: Au/ZnO photocatalyst, Gold nanoparticle, Visible-light photocatalyst, Methylene blue degradation, Electron transfer pathwa

Microwave Spin Control of a Tin-Vacancy Qubit in Diamond

The negatively charged tin-vacancy (SnV-) center in diamond is a promising solid-state qubit for applications in quantum networking due to its high quantum efficiency, strong zero phonon emission, and reduced sensitivity to electrical noise. The SnV- has a large spin-orbit coupling, which allows for long spin lifetimes at elevated temperatures, but unfortunately suppresses the magnetic dipole transitions desired for quantum control. Here, by use of a naturally strained center, we overcome this limitation and achieve high-fidelity microwave spin control. We demonstrate a pi-pulse fidelity of up to 99.51+/0.03%$ and a Hahn-echo coherence time of T2echo = 170.0+/-2.8 microseconds, both the highest yet reported for SnV- platform. This performance comes without compromise to optical stability, and is demonstrated at 1.7 Kelvin where ample cooling power is available to mitigate drive induced heating. These results pave the way for SnV- spins to be used as a building block for future quantum technologies