Sulfated choline ionic liquid-catalyzed acetamide synthesis by grindstone method

Sulfated choline ionic liquid (SCIL) has been found to be an efficient solid acid IL catalyst for the protection of amine groups with acetic anhydride under solvent-free grindstone conditions. The attractive features of this new catalytic methodology include its sustainability, facile work-up procedure, economic viability, and biodegradability. The SCIL catalyst was characterized using infrared spectroscopy, wide-angle X-ray scattering analysis, and scanning electron microscopy with energy dispersive X-ray spectroscopy. The catalyst could be reused six times without significant loss in activity. Furthermore, no chromatographic separations were needed to obtain the desired products.     

Preparation of silica/perfluoroalkyl methacrylate polymer inorganic/organic particles in supercritical carbon dioxide

Silica/perfluoroalkyl methacrylate polymer (PHDFDMA) particles were prepared using various types of silica by polymerization in supercritical carbon dioxide. There are three steps in the fabrication of inorganic/organic hybrid composites: silane treatment, polymerization, and soxhlet extraction. After these steps, we observed the morphology of silica/PHDFDMA particles using field emission scanning electron microscope and transmission electron microscope. From these analyses, we can confirm that the silica/PHDFDMA core/shell particles were obtained when we used Ludox and silica gel as a silica template. On the other hand, core/shell particles were not formed when using fused silica and precipitated silica. In addition, to confirm the amount of polymer on silica, we performed an analysis using thermogravimetric analysis and electron probe micro-analyzer. In this case, PHDFDMA was approximately 20 wt.% on the silica gel and 40 wt.% on the Ludox, respectively. When using fused silica and precipitated silica as a template, amount of PHDFDMA on silica was maximum 5 wt.% and over 40 wt.%, respectively. From these results, to obtain enough PHDFDMA encapsulated silica particle, colloidal silica, Ludox is the best template in four different types of silica.     

Closed-packed lattice model for polymer solution systems considering the chain length dependence effect: Correlating LLE,VLE, and gel swelling behaviors using identical interaction energy parameters

We propose a new Helmholtz energy of mixing equation following the original Flory–Huggins (F–H) closed-packed lattice model. Also, to overcome F–H mean-field approximation, we introduce new universal constants to consider chain length dependence of polymer in solvent and consider specific interactions to describe strongly interacting polymer systems. Our proposed model successfully describes liquid–liquid equilibria (LLE) for binary polymer–solvent systems using identical interaction parameters which do not depend on the polymer molecular weight. We also describe vapor–liquid equilibria (VLE) for polymer/solvent systems and swelling equilibria of thermosensitive hydrogel systems using the same energy parameters obtained from LLE calculations.     

Thermal stability of sol–gel derived methacrylate oligosiloxane-based hybrids for LED encapsulants

Methacrylate oligosiloxane-based hybrid materials (methacrylate hybrimers) were fabricated by curing the methacrylate oligosiloxane resins synthesized by sol–gel condensation reaction of 3-(trimethoxysilyl)propyl methacrylate (MPTS) and diphenylsilanediol (DPSD) for the LED encapsulant application. The fabricated hybrimers are optically transparent and have a high refractive index up to 1.565 depending on the precursor composition. The lower DPSD content hybrimer, which is the more polymerized and heated in a vacuum to remove the non-polymerized methacrylate groups, produces higher optical transmittance and thermal stability. This behavior is interpreted by thermal degradation of methacylate groups in the hybrimers.     

Highly Selective and Low Damage Etching of GaAs/AlGaAs Heterostructure using Cl2/O2 Neutral Beam

Highly selective and low damage etching of the GaAs cap layer on AlGaAs is essential in fabricating GaAs/AlGaAs high electron mobility transistors. The GaAs on AlGaAs was etched using a low energy Cl₂/O₂ neutral beam and the Schottky device characteristics fabricated on the exposed AlGaAs were compared with those fabricated after the etching using wet etching and a Cl₂/O₂ ion beam. Using a low energy Cl₂/O₂ ion beam or a Cl₂/O₂ neutral beam, highly selective etching of the GaAs cap layer to AlGaAs similar to wet etching could be achieved through the formation of Al₂O₃ on the exposed AlGaAs during the etching. When the electrical characteristics of the Schottky devices were compared, the devices fabricated after the etching using the neutral beam showed the best electrical characteristics such as electrical stability, low leakage current, higher barrier height, etc. by showing low damage to the exposed AlGaAs surface.     

Electrospinning fabrication and characterization of poly(vinyl alcohol)/montmorillonite/silver hybrid nanofibers for antibacterial applications

Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT)/silver (Ag) nanoparticles have been electrospun for fabricating PVA/MMT/Ag nanofiber in aqueous solutions. Since PVA is a water-soluble and biocompatible polymer, it is one of the best materials for preparation of antibacterial nanofiber. MMT has been used as an inorganic filler to enhance properties of homopolymeric nanofiber. The PVA/MMT/Ag nanofiber diameter increases with increasing contents of MMT clay and Ag nanoparticles. In preservation test, the PVA/MMT/Ag nanofiber confirms an excellent antibacterial performance, elucidating for practical uses as a new preservative. Moreover, the PVA/MMT/Ag nanofiber shows improved thermal properties.     

Li-ion batteries from LiFePO4 cathode and anatase/graphene composite anode for stationary energy storage

Li-ion batteries made from LiFePO₄ cathode and anatase TiO₂/graphene composite anode were investigated for potential application in stationary energy storage. Fine-structured LiFePO₄ was synthesized by a novel molten surfactant approach whereas anatase TiO₂/graphene nanocomposite was prepared via self-assembly method. The full cell that operated at 1.6 V demonstrated negligible fade even after more than 700 cycles at measured 1 C rate. While with relative lower energy density than traditional Li-ion chemistries interested for vehicle applications, the Li-ion batteries based on LiFePO₄/TiO₂ combination potentially offers long life and low cost, along with safety, all which are critical to the stationary applications.     

Effect of heat treatment on ZrO2-embedded electrospun carbon fibers used for efficient electromagnetic interference shielding

ZrO₂-embedded carbon fibers were prepared for use as an electromagnetic interference (EMI) shielding material by electrospinning and heat treatment methods. Structural changes were observed in the ZrO₂ and in the carbon structures by XRD and Raman spectroscopy, respectively. During heat treatment, XRD analysis results revealed a transition from a monoclinic structure to a tetragonal structure in ZrO₂ and a graphitization in the structural formation of carbon fibers was observed by Raman spectroscopy. It was observed that these structural changes in the ZrO₂ and the carbon fibers improved the real and imaginary permittivities by a factor of more than 3.5. The EMI shielding efficiency (SE) improved along with the permittivity with higher treatment temperatures and greater amounts of embedded ZrO₂; the highest average EMI SE achieved was 31.79 dB in 800-8500 MHz. The heat treatment played an important role in the improvements in the permittivity and in the EMI SE because of the heat-induced structural changes of the ZrO₂-embedded electrospun carbon fibers. We suggest that the EMI shielding of the fibers is primarily due to the absorption of electromagnetic waves, which prevents secondary EMI by reflection of electromagnetic waves.     

Experimental realization of an approximate partial transpose for photonic two-qubit systems

We report the first experimental realization of an approximate partial transpose for photonic two-qubit systems. The proposed scheme is based on the local operation on single copies of quantum states and classical communication, and therefore can be easily applied for other quantum information tasks within current technologies. Direct detection of entanglement, i.e., without performing quantum state tomography, using the partial transpose operation, is also demonstrated.