Synthesis of Ethylene Carbonate by Urea Transesterification Using Zeolitic Imidazolate Framework Derived Fe-Doped ZnO Catalysts.

The development of environmentally friendly and efficient methods for the synthesis of ethylene carbonate (EC) is crucial for advancing carbon capture, utilization, and storage technologies. Herein, we present the synthesis of EC through the transesterification of urea with ethylene glycol (EG) using a zeolitic imidazolate framework (ZIF) derived Fe-doped ZnO catalyst (Fe;ZnO-ZIF). The Fe;ZnO-ZIF catalyst, prepared by incorporating Fe dopant atoms into a ZnO-ZIF template, demonstrates excellent catalytic activity, achieving high conversion of reactants and superior selectivity toward EC at 160 °C for 150 min under an applied vacuum (160 mmHg). Based on the thermogravimetric, X-ray spectroscopic, and temperature-programmed desorption analysis, the simultaneous presence of strong Lewis acidic and basic sites in Fe;ZnO-ZIF enables its excellent catalytic performance toward EC synthesis with high selectivity. Acidic sites activate the carbon center in urea, while basic sites facilitate the nucleophilic attack on urea by deprotonation of EG. This synergistic reaction pathway resulting from the interaction between the strong Lewis acidic and basic sites promotes nucleophilic attacks of EG on urea, leading to significantly higher conversion efficiency and selectivity, compared to the commercial benchmark ZnO. Although the establishment of a continuous reaction system which takes into account cyclability and stability of the catalysts is further required in the future, our research reported herein provides valuable insights into the design of synergistic, localized active sites for EC synthesis and contributes to the development of sustainable carbon utilization technologies for achievement of net-zero emissions.

Interdigitated Electrode Biosensor Based on Plasma-Deposited TiO2 Nanoparticles for Detecting DNA.

Bioelectrodes mediated by metal oxide nanoparticles have facilitated the development of new sensors in medical diagnosis. High-purity TiO2 nanoparticles (NPs) were synthesized through thermal plasma and deposited directly on an interdigitated electrode. The surface of the TiO2-deposited electrode was activated with (3-aminopropyl) triethoxysilane (APTES) followed by fixing the single-stranded probe deoxyribonucleic acid (DNA) to fabricate the DNA biosensor. The structural properties of the deposited TiO2 nanoparticles were analyzed using a transmission electron microscope (TEM), X-ray diffraction (XRD), and a dynamic light scattering (DLS) system. The chemical composition and structural properties of the TiO2 nanoparticle layer and the fixed layer were analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). E. coli O157:H7, a well-known pernicious pathogenic bacterial species, was detected as a target DNA of the prepared DNA biosensor, and the characteristics of DNA detection were determined by the current change using a picoammeter. The degree of binding between the probe DNA and the target DNA was converted into an electrical signal using the picoammeter method to quantitatively analyze the concentration of the target DNA. With the specificity experiment, it was confirmed that the biosensor was able to discriminate between nucleotides with mismatched, non-complementary, or complementary sequences.

Multimodal porous carbon derived from ionic liquids: correlation between pore sizes and ionic clusters.

In this proof of concept study on the synthesis of ionic liquid (IL)-derived multimodal porous carbon using ionic clusters of different sizes as porogens, the carbonization behaviors of binary IL mixtures of 1-ethyl-3-methylimidazolium dicyanamide (EMIM-dca) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-Tf2N) were systematically investigated to demonstrate the formation of multimodal porous carbons with hierarchical structures originating from the ionic cluster porogens. The multimodal porous structures of the resulting IL-derived porous carbons were characterized based on the quenched solid density functional theory, and the role of the ionic clusters as porogens is discussed. From the viewpoint of green and sustainable chemistry, the IL-based synthesis using ionic clusters as porogens is a simple, effective, and sustainable technique for synthesizing multimodal porous carbons with hierarchical structures. To the best of our knowledge, this is the first study demonstrating that a multimodal porous structure of IL-derived porous carbons could be systematically manipulated with the aid of ionic clusters of different sizes as porogens.

Selective removal of alkynes from diene mixtures using ether-functionalized Cu(i)-containing ionic liquids as extractants.

Cu(i)-Containing room temperature ionic liquids (Cu-EnA), prepared from CuCl and ether-functionalized ionic liquids (ILs) bearing a methanesulfonate anion (EnA, n = 1, 2 or 3), were thermally stable and highly effective for the removal of alkynes such as isopropenylacetylene (IPA) and 2-butyne (2-BT) contained in dienes like isoprene (2-methyl-1,3-butadiene). Cu-EnA were found to reversibly and selectively interact with IPA and 2-BT, thereby enabling the regeneration of Cu-EnA. Fast atom bombardment (FAB)-mass spectral and computational results imply that EnA consists of an ether-functionalized imidazolium cation and a methanesulfonate-coordinated Cu(i) anion such as [CuCl(CH3SO3)]- ([CuClA]-) or [Cu(CH3SO3)2]- ([CuA2]-). Computational studies demonstrate that the preferential extraction of IPA and 2-BT to isoprene by Cu-EnA originated from the difference in the strength of the hydrogen bonding and π-complexation.

Tailoring chemically converted graphenes using a water-soluble pyrene derivative with a zwitterionic arm for sensitive electrochemiluminescence-based analyses.

We report a method to tailor chemically converted graphenes (CCGs) using a water-soluble pyrene derivative (1) with a zwitterionic arm, and the feasibility of the tailored CCGs to sensitive electrochemiluminescence (ECL)-based analyses. The compound 1 serves the dual purpose of improving the dispersion of the CCGs in aqueous solutions and further tailoring the catalytic activity of the CCGs with dendrimer-encapsulated catalytic nanoparticles. As a model system, we conjugated dendrimer-encapsulated Pt nanoparticles to the 1-functionalized CCGs on indium tin oxide (ITO) electrodes. The resulting ITOs exhibited significantly increased ECL emission of the luminol/H2O2 ECL system; i.e. two orders-of-magnitude enhancement in the ECL compared to that obtained from bare ITOs, which allowed a ca. 154 times more sensitive ECL-based analysis of cholesterol using the modified ITOs compared with the use of bare ITOs.

Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals.

A novel ionic mixture of an imidazolium-based room-temperature ionic liquid containing ethylene-oxide-functionalized phosphite anions is fabricated, which, when doped with lithium salt, self-assembles into a smectic-ordered ionic liquid crystal through Coulombic interactions between the ion species. Interestingly, the smectic order in the ionic-liquid-crystal ionogel facilitates ionic transport.

CO2 absorption and desorption in an aqueous solution of heavily hindered alkanolamine: structural elucidation of CO2-containing species.

The pathways for the CO2 absorption and desorption in an aqueous solution of a heavily hindered alkanolamine, 2-(t-butylamino)ethanol (TBAE) were elucidated by X-ray crystallographic and (13)C NMR spectroscopic analysis. In the early stage of the CO2 absorption, the formation of carbonate species ([TBAEH]2CO3) was predominant, along with the generation of small amounts of zwitterionic species. With the progress of the absorption, the carbonate species was rapidly transformed into bicarbonate species ([TBAEH]HCO3), and the amounts of the zwitterionic species increased gradually. During desorption at elevated temperature in the absence of CO2, [TBAEH]HCO3 was found to transform into [TBAEH]2CO3, where CO3(2-) strongly interacts with two [TBAEH](+) via hydrogen bondings.

Electrochemical control of ion transport through a mesoporous carbon membrane.

We report a carbon-based, three-dimensional nanofluidic transport membrane that enables gated, or on/off, control of the transport of organic molecular species and metal ions using an applied electrical potential. In the absence of an applied potential, both cationic and anionic molecules freely diffuse across the membrane via a concentration gradient. However, when an electrochemical potential is applied, the transport of ions through the membrane is inhibited.

Nitrile-functionalized tertiary amines as highly efficient and reversible SO2 absorbents.

Three different types of nitrile-functionalized amines, including 3-(N,N-diethylamino)propionitrile (DEAPN), 3-(N,N-dibutylamino)propionitrile (DBAPN), and N-methyl-N,N-dipropionitrile amine (MADPN) were synthesized, and their SO2 absorption performances were evaluated and compared with those of hydroxy-functionalized amines such as N,N-diethyl-N-ethanol amine (DEEA), N,N-dibutyl-N-ethanol amine (DBEA), and N-methyl-N,N-diethanol amine (MDEA). Absorption-desorption cycle experiments clearly demonstrate that the nitrile-functionalized amines are more efficient than the hydroxy-functionalized amines in terms of absorption rate and regenerability. Computational calculations with DBEA and DBAPN revealed that DBEA bearing a hydroxyethyl group chemically interacts with SO2 through oxygen atom, forming an ionic compound with a covalently bound OSO2(-) group. On the contrary, DBAPN bearing a nitrile group physically interacts with SO2 through the nitrogen and the hydrogen atoms of the two methylene groups adjacent to the amino and nitrile functionalities.

Role of alkyl group in the aromatic extraction using pyridinium-based ionic liquids.

The performance of N-alkylpyridinium-based ionic liquids with a SCN anion (PyILs) was evaluated for the selective extraction of aromatics from aliphatic hydrocarbons. The aromatic extraction ability of PyILs was greatly enhanced by the presence of a methyl group on the pyridinium ring at the 3- or 4-position, whereas the solubility of the aromatics in the PyILs decreased with increasing the number of methyl groups on the benzene ring. The FT-IR studies revealed that the solubility of an aromatic compound in a PyIL is closely correlated with the degree of aromatic C-H bending frequency shift observed during the dissolution of the aromatic compound in the PyIL: the larger the shift, the higher the solubility. The computational calculations on the dispersion interactions between aromatics and PyILs demonstrated that the anion-aromatic interaction is much more important than the cation-aromatic interaction in determining the aromatic solubility in PyILs, and such anion-aromatic interaction can be enhanced by introducing a methyl group at the carbon atom of the pyridinium ring.

Boron and nitrogen-rich carbons from ionic liquid precursors with tailorable surface properties.

A novel strategy for tailoring the adsorption and structural properties of ionic liquid derived carbons has been developed. By changing the carbonization temperature and ratios of ionic liquids (ILs) containing a cross-linkable anion, such as 1-butyl-3-methylimidazolium tricyanomethanide [BMIm][C(CN)(3)] and 1-ethyl-3-methylimidazolium tetracyanoborate [EMIm][B(CN)(4)], boron and nitrogen-rich carbons with slit-like pores and specific surface areas exceeding 500 m(2) g(-1) have been prepared. Furthermore, the nitrogen-rich carbons exhibit high adsorption capacity for CO(2) adsorption and selectivity for CO(2)/N(2) separation.

Concentrations of TSP-bound metals in four urban residential locations in Seoul, Korea.

Concentrations of 17 trace metals bound in total suspended particulate (TSP) were measured at four urban residential locations (Jong Ro [JR], Gwang Jin [GJ], Gang Seo [GS], and Yang Jae [YJ]) in Seoul, Korea from February to July 2009. The maximum concentrations of metals were recorded by Fe in the range of 2599 (JR) to 2914 ng m(-3) (GJ), while the least values were observed from Ag or Co with a few ng m-3. The relative ordering of the mean concentration (ng m(-3)) at these sites is generally found on the order of Fe>Zn>Ba>Mn>Pb>Cu>B>Cr>Ni>Sr>V>As>Li>Cd>Mo>Co>Ag or with a few exceptions (e.g., a reversal between Ba and Mn or between Ni and Sr). Calculation of the enrichment factor suggests the significant role of man-made processes on such metals as Cd, Zn, and Pb. Inspection of the temporal patterns indicates the peak occurrence of most metals during the spring season due in part to the Asian Dust (AD) event. However, according to the factor analysis, sources of these metals were dominated by both resuspended soil/road dust and the combustion of fossil fuels. The overall results of our study suggest that the interaction between the environmental conditions and roadside traffic activities are paramount in explaining the metal pollution in these urban residential areas.

Facile ionothermal synthesis of microporous and mesoporous carbons from task specific ionic liquids.

An expedient, template-free, high-yield, and solventless route to nitrogen-rich micro- and mesoporous carbons is reported based on direct, atmospheric-pressure carbonization of task-specific ionic liquids bearing one or more nitrile side chains. The resulting textural properties (pore regime, surface area) are highly dependent upon the structural motifs of the ions comprising the corresponding parent ionic liquid, and uniform carbon films are routinely deposited with this novel methodology, highlighting excited new opportunities in the development of advanced functional carbon composites.

Ultrastable superbase-derived protic ionic liquids.

Protic ionic liquids are synthesized via proton transfer from acids to organic bases. One of the key issues associated with conventional protic ionic liquids is the thermal instability resulting from temperature-induced decomposition via reverse proton transfer. This shortcoming significantly hampers the use of these protic ionic liquids in separations, electrochemical capacitors, fuel cells, and so forth. Herein we show that it is possible to prepare protic ionic liquids with thermal stabilities approaching those of common aprotic ionic liquids. Our new class of protic ionic liquids, derived via integrated neutralization and metathesis of superbasic phosphazenes or guanidines, exhibits exceptionally low vapor pressures at 150 degrees C while being stable to strong alkali agents such as aqueous KOH, suggesting potential in energy-related applications, including electrochemical capacitors and PEM-type fuel cells.

Mechanistic investigation of the isomerization of 5-vinyl-2-norbornene.

The isomerization reaction of 5-vinyl-2-norbornene (VNB) to 5-ethylidene-2-norbornene (ENB) has been performed using a catalytic system consisting of an alkali metal hydride and an amine. Among various amines tested, only aliphatic 1,2-diamines exhibited the activity for the isomerization. The isomerization was also affected by the alkali metal hydride employed. The activity of the alkali metal hydride increased with the increasing size of alkali metal: KH > NaH > LiH. A series of electron paramagnetic resonance (EPR) and UV-vis experiments on the active species suggest that the isomerization of VNB proceeds through a radical mechanism.

[Ru(phen)2DPPZ]2+ is in contact with DNA bases when it forms a luminescent complex with single-stranded oligonucleotides.

The luminescence intensity of the Delta- and Lambda-enantiomer of [Ru(phen)2DPPZ]2+ ([Ru(phenanthroline)2 dipyrido[3,2-a:2',3'-c]phenazine]2+) complex enhanced upon binding to double stranded DNA, which has been known as "light switch effect". The enhancement of the luminescence required the intercalation of the large ligand between DNA base pairs. In this study, we report the enhancement in the luminescence intensity when the metal complexes bind to single stranded oligonucleotides, indicating that the "light switch effect" does not require intercalation of the large DPPZ ligand. Oligonucleotides may provide a hydrophobic cavity for the [Ru(phen)2DPPZ]2+ complex to prevent the quenching by the water molecule. In the cavity, the metal complex is in contact with DNA bases as is evidenced by the observation that the excited energy of the DNA bases transfer to the bound metal complex. However, the contact of the metal complex with DNA bases is different from the stacking of DPPZ in the intercalation pocket. In addition to the normal two luminescence lifetimes, a short lifetime in the range of 1-2 ns was found for both the delta- and lambda-enantiomer of [Ru(phen)2DPPZ]2+ when complexed with single stranded oligonucleotides, which may be assigned to the metal complex that is outside of the cavity, interacting with phosphate groups of DNA.

Isolation of an oxomanganese(V) porphyrin intermediate in the reaction of a manganese(III) porphyrin complex and H2O2 in aqueous solution.

The reaction of [Mn(TF(4)TMAP)](CF(3)SO(3))(5) (TF(4)TMAP=meso-tetrakis(2,3,5,6-tetrafluoro-N,N,N-trimethyl-4-aniliniumyl)porphinato dianion) with H(2)O(2) (2 equiv) at pH 10.5 and 0 degrees C yielded an oxomanganese(V) porphyrin complex 1 in aqueous solution, whereas an oxomanganese(IV) porphyrin complex 2 was generated in the reactions of tert-alkyl hydroperoxides such as tert-butyl hydroperoxide and 2-methyl-1-phenyl-2-propyl hydroperoxide. Complex 1 was capable of epoxidizing olefins and exchanging its oxygen with H(2) (18)O, whereas 2 did not epoxidize olefins. From the reactions of [Mn(TF(4)TMAP)](5+) with various oxidants in the pH range 3-11, the O-O bond cleavage of hydroperoxides was found to be sensitive to the hydroperoxide substituent and the pH of the reaction solution. Whereas the O-O bond of hydroperoxides containing an electron-donating tert-alkyl group is cleaved homolytically, an electron-withdrawing substituent such as an acyl group in m-chloroperoxybenzoic acid (m-CPBA) facilitates O-O bond heterolysis. The mechanism of the O-O bond cleavage of H(2)O(2) depends on the pH of the reaction solution: O-O bond homolysis prevails at low pH and O-O bond heterolysis becomes a predominant pathway at high pH. The effect of pH on (18)O incorporation from H(2) (18)O into oxygenated products was examined over a wide pH range, by carrying out the epoxidation of carbamazepine (CBZ) with [Mn(TF(4)TMAP)](5+) and KHSO(5) in buffered H(2) (18)O solutions. A high proportion of (18)O was incorporated into the CBZ-10,11-oxide product at all pH values but this proportion was not affected significantly by the pH of the reaction solution.