The
facile and rapid microwave-assisted method has been demonstrated
to be effective in synthesizing manganese fluoride (MnF2) nanoparticles in binary mixtures of ethylene glycol and imidazolium-based
ionic liquid containing fluorine, within a minute, without any surfactant
and stabilizer. The effect of volume ratio of an ionic liquid in the
binary mixtures with ethylene glycol and the length of the alkyl chain
of imidazolium on the morphologies and crystalline structures of MnF2 was investigated. Two types of crystalline phases MnF2, P42/mnm rutile
and P4̅2m space group, were
synthesized depending on the volume ratio of EMIM BF4.
The morphologies of rutile MnF2 clearly varied depending
on what kind of ionic liquid was used in the synthesis. MnF2 nanoparticles and spherical nanoclusters assembled by nanospheres
were synthesized when the used ionic liquid was OMIM BF4 and EMIM BF4, respectively. Clear room temperature photoluminescence
(PL) spectra of MnF2 nanoparticles were observed at ambient
pressure. The change of PL spectra depending on the crystalline phase
was also observed. In this study, we report that the microwave-assisted
method using ethylene glycol–ionic liquid binary mixtures is
proper for synthesizing high-quality MnF2 nanoparticles
with controllable crystalline phase and morphology.
In this study, we investigated the possibility of using Zn-doped ITO film as an alternative material for conventional SiO2 waveguides used in optical communication. The Zn-doped ITO films were deposited on quartz substrates using a combinatorial sputtering system, which yielded composition spread Zn-In-Sn-O (ZITO) films by co-sputtering two targets of ITO and ZnO. The Zn-doped ITO films deposited at room temperature exhibited an amorphous phase in the Zn content [Zn/(Zn+In+Sn)] range of 39-54 at%. The Zn-doped ITO films deposited at low oxygen partial pressure showed resistivity below 10(-3) ohms cm and optical transmittance of approximately 85% at 550 nm. The refractive index calculated by the Swanepoel method was found to be dependent on the Zn content in the Zn-doped ITO films. The calculated bending loss from the refractive index indicated that Zn-doped ITO could be utilized as a new waveguide material for various optical devices, such as optical splitters, wavelength division multiplexers (WDMs), optical modulators, and optical switches.
Over the last few decades electrochemical CO2 reduction has attracted attention as a promising technology for greenhouse gas reduction. The Carbon monoxide product from CO2 reduction is of interest as a component of syngas for methanol synthesis. Silver is a reactive electrocatalyst toward carbon dioxide reduction to Carbon monoxide among single metals (Au, Zn etc.). In order to carry out CO2 reduction reaction effectively, it is require to nano-sized electro catalyst for wide active area. However, there is aggregation issue of nano-sized particle in liquid phase reduction method from metal precursor. It can be solved simply using of ionic liquid as a solvent and capping agent to suppress aggregation of nano-particle. In addition, Microwave-assisted fabrication has much potential due to their distinctive characteristics such as rapid heating ability, efficient and uniform internal heating, and relatively short process time.
Here we describe its use as a single electrocatalyst made in Microwave method with Ionic liquid for reduction of CO2 to CO. We have simply synthesized Ag nanoparticles with an ultra-fine size (~20nm) by microwave irradiation process using Ag precursors dissolve in Ionic liquid. Silver carbonate (Ag2CO3, purchased from Sigma Aldrich) as a precursor was dissolved in Ionic liquid, Butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4-, purchased from C-TRI). The 5mL mixture solutions with a concentration of 10, 20 and 30mM were prepared by stirring under atmosphere at room temperature. Each mixture solution was heated by microwave irradiation system (CEM Co.,Ltd Discover) at the power of 10~30W within just 10min.
Characterization of synthesized silver nanoparticles was analyzed by Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) to confirm the morphology, chemical state, and crystal structure of the samples. XRD analysis showed (111), (200), (220), (311), and (222) diffractions of Ag metal with a face-centered cubic structure, confirming that the silver nanoparticles could be synthesized. TEM images showed that the nanoparticles have ultra-fine sized silver, less than 20nm without aggregation. Based on CO2 reduction reaction (CO2RR) response, the elctrocatalystic performance of synthesized silver was evaluated. In order to compare the performance, the same mass of commercial Ag and carbon black were used in three electrode system with 0.5M KHCO3 aqueous solution saturated with CO2. The catalytic potential reduced 0.374eV compared to carbon black.
In order to confirm the efficiency of Solar-driven electrochemical carbon dioxide reduction, synthsized silver nano catalyst of 9mg/cm2 was loaded at the cathode(6.25cm2) in electrochemical reactor which is a closed two-component separated by anion exchange membrane (Sustainion® X37-50, Dioxide Materials). The anode was IrOx (purchased from Dioxide materials) sprayed on Carbon paper (9cm2). A Si solar cell of series connection solar panels supplied electric power to electrochemical reactor. We achieved the Faradaic Efficiency of 92% to Carbon monoxide conversion by synthesized silver catalyst. We obtained 8.81% to Power conversion efficiency employing series connected Si photovoltaics for CO2 conversion to CO.
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