Fast light-switchable polymeric carbon nitride membranes for tunable gas separation

Switchable gas separation membranes are intriguing systems for regulating the transport properties of gases. However, existing stimuli-responsive gas separation membranes suffer from either very slow response times or require high energy input for switching to occur. Accordingly, herein, we introduced light-switchable polymeric carbon nitride (pCN) gas separation membranes with fast response times prepared from melamine precursor through in-situ formation and deposition of pCN onto a porous support using chemical vapor deposition. Our systematic analysis revealed that the gas transport behavior upon light irradiation is fully governed by the polarizability of the permeating gas and its interaction with the charged pCN surface, and can be easily tuned either by controlling the power of the light and/or the duration of irradiation. We also demonstrated that gases with higher polarizabilities such as CO2 can be separated from gases with lower polarizability like H2 and He effectively with more than 22% increase in the gas/CO2 selectivity upon light irradiation. The membranes also exhibited fast response times (<1 s) and can be turned “on” and “off” using a single light source at 550 nm

Kullanılmış kayganlaştırıcı yağların manyetik nanoparçacıklar ve kostik soda kullanılarak geri kazanılması

Cataloged from PDF version of article.Thesis (M.S.): Bilkent University, Department of Materials Science and Nanotechnology, İhsan Doğramacı Bilkent University, 2017.Includes bibliographical references (leaves 1-8).Oils are one of the mostly used lubricants in industry. Chemical oxidation, however, causes depletion of additive materials i.e. antioxidants in lubricants and their usage life time shortens. This causes varnish and sludge problems and leaves behind tons of used oil that loses its functionality. It is reported that more than 600 tons of lubricating oil can be reclaimed from 1000 tons of used oil. One of the reclamation methods is caustic extraction, and has been known for more than 3 decades. Although caustic extraction has a very high potential because of its economic considerations, this method is not fully understood due to lack of research. We have revealed that opposite to the common belief, oxidized oils (used oils) have ester groups in contrary to carboxylic acids. Magnetic nanoparticles (Fe3O4) can be used as a catalyst for hydrolysis of various esters. We have investigated the effect and mechanism of caustic extraction in combination with magnetic iron oxide nanoparticles. Using sodium hydroxide, breaks ester bonds by forming carboxylate salts and alcohols. These carboxylate salts are transferred into water and can be removed by water. Formed alcohol groups can be trapped by drying agents like MgSO4. Further purification of reclaimed oils can be achieved using hexane or similar low molecular weight and inexpensive solvents. According to our results, properties of recovered base oils mostly compete with petroleum based and ester-based synthetic base oil properties.by Timur Ashirov.M.S

A Three‐Dimensional Porous Organic Semiconductor Based on Fully sp 2 ‐Hybridized Graphitic Polymer

Dimensionality plays an important role in the charge transport properties of organic semiconductors. Although three-dimensional semiconductors, such as Si, are common in inorganic materials, imparting electrical conductivity to covalent three-dimensional organic polymers is challenging. Now, the synthesis of a three-dimensional π-conjugated porous organic polymer (3D p-POP) using catalyst-free Diels–Alder cycloaddition polymerization followed by acid-promoted aromatization is presented. With a surface area of 801 m2 g−1, full conjugation throughout the carbon backbone, and an electrical conductivity of 6(2)×10−4 S cm−1 upon treatment with I2 vapor, the 3D p-POP is the first member of a new class of permanently porous 3D organic semiconductors.U.S. Department of Energy, Office of Basic Energy Sciences (Grant DESC0018235)National Science Foundation (Award 1122374

A Three-Dimensional Porous Organic Semiconductor Based on Fully sp² -Hybridized Graphitic Polymer

Dimensionality plays an important role in the charge transport properties of organic semiconductors. Although three‐dimensional semiconductors, such as Si, are common in inorganic materials, imparting electrical conductivity to covalent three‐ dimensional organic polymers is challenging. Now, the synthesis of a three‐ dimensional π‐conjugated porous organic polymer (3D p‐POP) using catalyst‐free Diels–Alder cycloaddition polymerization followed by acid‐promoted aromatization is presented. With a surface area of 801 m2 g−1, full conjugation throughout the carbon backbone, and an electrical conductivity of 6(2)×10−4 S cm−1 upon treatment with I2 vapor, the 3D p‐POP is the first member of a new class of permanently porous 3D organic semiconductors

Fourier transform plasmon resonance spectrometer using nanoslit-nanowire pair

In this paper, we present a nanoscale Fourier transform spectrometer using a plasmonic interferometer consisting of a tilt subwavelength slit-nanowire pair on a metallic surface fabricated by the focused ion beam microfabrication technique. The incident broadband light strongly couples with the surface plasmons on the gold surface, and thus, surface plasmon polaritons (SPPs) are generated. The launched SPPs interfere with the incident light and generate high contrast interference fringes in the nanoslit. The transmitted SPPs through the metal nanoslit can decouple into free space and are collected by an objective in the far field. The spectroscopic information of the incidence light is obtained by fast Fourier transform of the fringe pattern of the SPPs. In our design, there is no need for a bulky dispersive spectrometer or dispersive optical elements. The dimension of the spectrometer is around 200 mu m length. Our design is based on inherent coherence of the SPP waves propagating through the subwavelength metal nanoslit structures etched into an opaque gold film

Porous polyisothiocyanurates for selective palladium recovery and heterogeneous catalysis

Palladium is an indispensable metal due to its wide range of industrial applications. Pd refining, however, is an extremely energy-intensive process with a serious environmental impact. Thus, the selective recovery of Pd from secondary sources is rather important. In this direction, solid sorbents are promising candidates owing to their reusability. Here, we report the synthesis of porous polyisothiocyanurates through the trimerization of 1,4-phenyldiisothiocyanate under ionothermal conditions, named covalent isothiocyanurate frameworks (CITCFs), bearing in situ generated thiourea moieties as binding sites for Pd. High surface area of CICTFs, 1,589 m2 g−1, along with the presence of abundant sulfur atoms within a hierarchically porous network, enabled an exceptional Pd(II) uptake capacity of 909 mg g−1, fast adsorption kinetics, stable uptake over a wide pH range, and selective Pd(II) recovery from wastewater conditions. Moreover, the reduction of recovered Pd(II) within the polymer network led to highly efficient heterogeneous catalysis for the Suzuki-Miyaura cross-coupling reaction.ISSN:2451-9294ISSN:2451-930

Fluorinated ether electrolyte with controlled solvation structure for high voltage lithium metal batteries

The development of lithium-metal batteries is limited by the low thermodynamic and/or low voltage stability of conventional electrolytes. Here, the authors combined the high voltage stability of fluorinated ethers with high Li+ solvation ability of ethers in a single molecule and realized highly stable lithium-metal batteries. The development of new solvents is imperative in lithium metal batteries due to the incompatibility of conventional carbonate and narrow electrochemical windows of ether-based electrolytes. Whereas the fluorinated ethers showed improved electrochemical stabilities, they can hardly solvate lithium ions. Thus, the challenge in electrolyte chemistry is to combine the high voltage stability of fluorinated ethers with high lithium ion solvation ability of ethers in a single molecule. Herein, we report a new solvent, 2,2-dimethoxy-4-(trifluoromethyl)-1,3-dioxolane (DTDL), combining a cyclic fluorinated ether with a linear ether segment to simultaneously achieve high voltage stability and tune lithium ion solvation ability and structure. High oxidation stability up to 5.5 V, large lithium ion transference number of 0.75 and stable Coulombic efficiency of 99.2% after 500 cycles proved the potential of DTDL in high-voltage lithium metal batteries. Furthermore, 20 mu m thick lithium paired LiNi0.8Co0.1Mn0.1O2 full cell incorporating 2 M LiFSI-DTDL electrolyte retained 84% of the original capacity after 200 cycles at 0.5 C.Y