Solid-phase microextraction, a frequently used sample preparation technique, is the miniaturization of the traditional extraction models, which gains copious attention due to its merits, especially, the ability to couple with the chromatography instruments. Currently, the improvement in the applications of solid-phase microextraction is focused on the development of novel coatings to enhance the extraction efficiency. The recent relevant examples of solid-phase microextraction fiber with the newly developed coatings are the highlights. In view of the material species, we classified the coatings in three categories including inorganic coatings (metal–organic frameworks, carbon nanotubes, graphene, metal and metal oxides), organic polymer coatings (polymeric ionic liquids, molecularly imprinted polymers), and other coatings (aptamer-functionalized materials, nanofibers). The applications of solid-phase microextraction fiber in the extraction of various analytes (environmental residues and biological analytes) in different real complex samples are briefly described.
In view of the material species, we classified the coatings in three categories including inorganic coatings (metal–organic frameworks, carbon nanotubes, graphene, metal and metal oxides), organic polymer coatings (polymeric ionic liquids, molecularly-imprinted polymers), and other coatings (aptamer-functionalized materials, nanofibers). The applications of solid-phase microextraction fiber in the extraction of various analytes (environmental residues and biological analytes) in different real complex samples are briefly described.
We developed novel reaction conditions for the removal of the diphenylmethyl group, which is one of the most important protecting groups for amines. The reaction was promoted by adding one equivalent of camphorsulfonic acid in aqueous media, and no acidic solvent was required.
In this work, a novel type of cost-effective bipolar membrane for efficient electrochemical water-splitting has been developed. The bipolar membranes with thin thickness were prepared through a pore-filling concept and showed excellent mechanical properties and water-splitting efficiency under reverse bias conditions. Additionally, an efficient method for the immobilization of metal catalyst on the bipolar membrane junction was investigated to increase the water-splitting efficiency of the membranes.
Fluorescent and aqueous-dispersible polymer dots (PDs) were prepared by simple microwave-assisted synthesis of hyperbranched polyethylenimine (h-PEI) and glycerol through the dehydration of glycerol and the subsequent imine formation with h-PEI.
Induced chirality of the cationic glutamide-based lipidic nanotube was enhanced through the formation of a hetero-network hydrogel with terminal alkylated non-chiral hydrophilic polymer, which was detected by the chiral interaction between the anionic cyanine dye and the nanotube.
This paper describes the generation of periodic motions of solid particle in an oil phase under a direct current (DC) voltage. We found that a dimer and trimer composed of spherical polystyrene (PS) particles exhibit a novel periodic motion, spin. These particles maintain their stable motion without any support from mechanical devices such as rotational axes or electronic switching devices. We expect that the simple DC micromotion is applicable for mechanical and fluidic devices employing microrobots and microfluidics.
Poly[3-(methacrylamido)propyltrimethylammonium chloride] (PMAPTAC) with a well-controlled structure was reacted with FeCl3 to exchange the counter anion from chloride (Cl−) to tetrachloroferrate (FeCl4−) to prepare a magnetic-responsive polymer (PMAPTAFe). PMAPTAFe powder was attracted to a neodymium magnet. A cast film of PMAPTAFe, which can be prepared from the aqueous solution, also showed magnetic-responsive behavior.
Bottom-up synthesis of quasi-one-dimensional graphene nanoribbons (GNRs) with defined structures and controllable properties has attracted great attention for potential applications in electronic and optoelectronic devices. Here we report a new on-surface method for high-throughput synthesis of GNRs without the need to sublime the precursors, but through solution processing. The new method is far simpler and more scalable compared to the previous GNR syntheses based on chemical vapor deposition or (ultra)high vacuum conditions, while preserving the high quality and uniformity as determined by Raman spectroscopy.
A H2 generation system based on the cyanobacterial photosystem I (PSI) reconstituted with 1,4-naphthoquinone-stabilized Pt nanoparticles (PtNPs) was constructed. Irradiating the system with red light (680 nm) and using sodium l(+)-ascorbate as the sacrificial electron donor generated H2, which was detected by GC. The light-induced H2 generation was observed at a maximum rate of 0.026 mol H2 h−1 (mol PSI)−1 using 2,6-dichloroindophenol (DCIP) as the mediator. The H2 evolution was increased to 0.053 mol H2 h−1 (mol PSI)−1 in the presence of cytochrome c (cyt c) as the mediator.
The emission peak wavelengths of Eu2+-doped inorganic phosphors have been predicted from only the stoichiometric information of the host materials. The prediction models were constructed with machine-learning technology optimized for screening inorganic phosphors. They are sufficiently simple and practical to explore the host materials. The error in the predicted emission wavelengths of the phosphors is 139 meV over the entire visible region. The models were theoretically validated by relating them to the current understanding of the mechanism controlling emission spectra.
Divalent calcium ion conducting solid electrolyte with three-dimensional NASICON-type structure, (CaxHf1−x)4/(4−2x)Nb(PO4)3, was successfully developed by introducing Ca2+ cations into HfNb(PO4)3 as mother solid. The existence of three kinds of high valence cation, Hf4+, Nb5+, and P5+, in the structure successfully realized the effective reduction of electrostatic interaction functioned to Ca2+ in the structure. The (Ca0.05Hf0.95)4/3.9Nb(PO4)3 solid showed considerably higher Ca2+ cation conductivity and lower activation energy than those of previously reported NASICON-type Ca0.5Zr2(PO4)3 solid.
Three emitters having a donor–phenyl–acceptor structure are considered as thermally activated delayed fluorescence (TADF) materials. They present different triplet excited-state energies depending on the substitution positions. Consequently, two materials exhibit blue emission with TADF properties. The OLEDs based on o-CzXTN provided a maximum EQE as high as 10.6%.
The present paper reports extremely efficient and versatile route for the synthesis of cubic copper ferrite (CuFe2O4) powder, which is promising for many interesting applications such as Li-ion storage, gas sensors, catalysts, and magnetic devices. The technique uses ethylene glycol (EG) as a solvent of Cu(NO3)2 and Fe(NO3)3. It has been found that crystalline CuFe2O4 powder is obtained by rapid boiling of the solution and spontaneous combustion. This time a hotplate (300 °C) was used, and the time required for obtaining 100 mg of the final product from 50 mL solution was only 15 min. The obtained CuFe2O4 powder has a cubic structure, while the tetragonal phase is more likely to be obtained in the ordinary process. The size of the crystal is rather small, mainly because of the low-temperature process. The technique is promising, because it is rapid and uses only one simple pass. For comparison, much slower drying (overnight at 100 °C) of the same solution has been also studied. It has been found that tetragonal phase CuFe2O4 is formed by subsequent heating the dried materials up to 1000 °C.
The effect of WO3 loading on the activity of Pt/WO3/Al2O3 with loadings of 2–20 wt % WO3 in hydrogenolysis of glycerol was investigated. Pt/WO3/Al2O3 with 7 wt % WO3 loading (coverage of Al2O3 with WO3 monolayer: ca. 33%) exhibited the highest conversion of glycerol and selectivity to 1,3-propanediol (1,3-PDO). The W-(OH)-Al sites at the boundaries between tungsten oxide monolayer domain and alumina have an important role in the selective hydrogenolysis of glycerol to 1,3-PDO.
We developed a mid-IR laser absorption spectrometer for ambient carbon monoxide (CO) measurement that uses a 4.69 µm interband cascade laser with wavelength modulation spectroscopy. The CO concentration was measured with a reproducibility of 0.4‰ (1σ) over a 7-h period. Measurements of CO in outside air with a temporal resolution of 1 s were conducted successfully on the Kashiwa campus of The University of Tokyo over 4 days without trouble.
Copper complexes, generated by the treatment of CuCl2 with EtMgCl, catalyze a reductive coupling reaction of perfluoroarenes with 1,3-dienes via C–F bond cleavage, in which the internal carbon of 1,3-dienes preferably reacts with perfluoroarenes giving rise to branched allylated perfluoroarenes as a major coupling product.
Chemically delithiated Li0.13Mn0.54Ni0.13Co0.13O2−δ was synthesized by the reaction of Li1.2Mn0.54Ni0.13Co0.13O2 with NO2BF4. Charge and discharge tests for the Li0.13Mn0.54Ni0.13Co0.13O2−δ/Mg alloy cell showed high discharge capacity of 273 mA h g−1. Since the XANES spectra showed a shift toward lower energy in the transition metals after discharge, the reduction of the main phase was confirmed accompanied with Mg intercalation. Rietveld analysis revealed that the mixed phases of layered rock-salt and Li2MnO3 types were generated by Mg insertion during the discharge process.
Direct annulative coupling of 3-aryl-1,2-benzisoxazoles and alkynes efficiently proceeds in the presence of a Cp*Rh(III) catalyst to produce 2-(1-isoquinolinyl)phenols of interest in medicinal chemistry as well as materials chemistry. The products may also be useful precursors of quinoline-based bidentate ligands.
Powders of REMO4 (RE: rare earth, M: Nb and Ta) were synthesized by a coprecipitation method employing water-soluble peroxo Nb/Ta complexes. This peroxo-based method is an aqueous solution route free from organics and halides. REMO4 was directly crystallized by annealing the precursor under moderate conditions. It has been revealed that the precursors are also useful for synthesis of oxynitrides under mild nitriding conditions.
Chiral SiO2 nanofibers associated with polyamines on their surfaces could promote polymerization between resorcinol and formaldehyde on silica surface to give phenolic resins (RF). In this process, the chiral information was effectively transferred from SiO2 to the final phenolic resins forming double chiral hybrid.
C3-selective direct coupling reactions of unsaturated 5-membered heterocycles such as 2,5-dihydrofuran, N-tosyl-2,5-dihydropyrrole, and 3-sulfolene with methyl methacrylate or methacryl amide are catalyzed by [Ru(η6-naphthalene)(η4-bicyclo[3.3.1]nona-2,6-diene)] (1b). As an application of this method, a pesticide lead, 2-methyl-3-(tetrahydrofuran-3-yl)propanamide (6ab) is prepared in 2 steps from 2,5-dihydrofuran in 62% total yield.
We report covalently interchain-linked graphene nanoribbons fabricated on Au(111) by a stepwise growth process via two-zone chemical vapor deposition. Prepolymer arrays were grown by surface-assisted polymerization of a precursor, 1,9-dibromodibenzo[g,p]chrysene at 250 °C. Further annealing at 450 °C converted the prepolymers into interchain-linked graphene nanoribbons via intramolecular and intermolecular dehydrogenation reactions.
We have employed two-photon photoemission (2PPE) spectroscopy to observe photoinduced charge transfer at C60 fullerene thin films formed on graphite and Au(111) substrates. From the analysis of the 2PPE intensities of molecular-derived unoccupied states, it is revealed that the photoexcited electron transfer from graphite substrate to C60 is suppressed compared to C60 on Au(111), owing to inert properties of graphite surfaces.
Synthesis of hydrosilanes by the hydrogenolysis reaction with H2 instead of reducing with strong hydride reagents such as lithium aluminum hydride was achieved. An iridium complex catalyst successfully converted silyl triflates and halides with H2 to the corresponding hydrosilanes in the presence of an amine under mild reaction conditions.
Furan dimer diester was obtained by reductive or oxidative homocoupling of furan carboxylate derivatives in the presence of a nickel or palladium catalyst. Treatment of the obtained diester with 1,ω-diol in the presence of titanium alkoxide as a catalyst leads to the corresponding polyester in excellent yields. The obtained polymers show remarkably high melting points compared with the related polyesters composed of a single furan ring derived from furan-2,5-dicarboxylic acid (FDCA). Thermal properties of the furan dimer-derived polyesters are comparable with those of terephthalate polymers such as poly(ethylene terephthalate).
The reactions of fac-[Rh(apt)3] (apt: 3-aminopropanethiolate) with PdII and ZnII gave S-bridged RhIII2ZnII trinuclear and RhIII3PdII3 hexanuclear complexes, respectively. The structures of these complexes, determined by single-crystal X-ray crystallography, were quite different from S-bridged structures derived from fac-[Rh(aet)3] (aet: 2-aminoethanethiolate). This is ascribed to the difference in S–Rh–S bite angles between fac-[Rh(apt)3] with six-membered N,S-chelate rings and fac-[Rh(aet)3] with five-membered N,S-chelate rings.
A novel cyclic emitter composed of tetraphenylsilane and tetraphenylethene backbone was successfully synthesized through a convenient homocoupling procedure. The optical and thermal properties of the compound were revealed. Intriguingly, the compound showed different color emissions in solid film, THF solution, and THF/water mixtures. It is assumed that the violet emission was from an isolated component of the emitter, whereas the sky blue and the green emissions were from a crystalline state, and an amorphous state, respectively. The red-shifted emissions were caused by the change of nature of the excitonic coupling.
In the presence of Pd(OAc)2, three bisacetylacetonate ligands were demonstrated to form a highly efficient catalyst for the Suzuki–Miyaura cross-coupling reactions. The most active bisacetylacetonate ligand with anthracene groups on the backbone showed a wide substrate scope in excellent yields using very low catalyst concentration of 0.01 mol % in ethanol/aqueous media under ambient atmosphere.
The robust superhydrophobic nickel micro/nanostructures with microscale papillae and nanoscale columnar islands were obtained by simple two-step electroless deposition on steel surfaces. The prepared superhydrophobic surfaces were proven to possess excellent anti-corrosion, friction-reducing, and anti-wear properties, which may lead to some new promising applications for superhydrophobic surfaces.
A C70 fragment (1) (C28H14) was synthesized by conversion of a C60 fragment sumanene, via ring expansion and annulation in 3 steps, the key step being the Wagner–Meerwein rearrangement of a five-membered ring to a six-membered one. Both theoretical and experimental investigations exhibited the shallower bowl structure of 1, resulting in the lower bowl inversion barrier than sumanene. It was also revealed that the indenopyrene skeleton largely contributed to the physical properties of 1.
Aluminum film thickness dependence of surface plasmon resonance (SPR) in the far- and deep-ultraviolet regions (170–300 nm) was revealed using an attenuated total reflectance spectrometer. In the far-ultraviolet region (<200 nm), films of thicknesses 23 and 9 nm showed strong SPR excitations in air and 1,1,1,3,3,3-hexafluoro-2-propanol, which were reproduced by simulations based on the Fresnel equations, respectively. Therefore, Al-SPR sensors are expected to work both in air and in liquids by controlling the film thickness.
Quantum yields can be determined by global fitting of prolonged change of concentration against absorbed photon numbers. Quantum yields of synthesized amphiphilic diarylethene in solution and in suspension were analyzed by the global fitting upon irradiation with UV (365 nm) light. Quantum yields of cyclization and cycloreversion reaction in acetonitrile were obtained as 0.59 and 0.013, respectively using the absolute method. In suspension, quantum yield of cyclization was determined as 0.76 using the relative method. The result indicates that the preferred conformation of the open-ring isomer in the aggregate was antiparallel due to the hydrophilic chains and hydrogen bond.
We report a fast, easy-to-handle, and accurate semiempirical quantum mechanical method to find a transition state (TS) for Mn-catalyzed oxidation reactions. Following our previous work, the reparameterization of PM6 (rPM6) for Mn is performed based on our training set. The spin-unrestricted calculations with the resultant parameter sets (UrPM6) successfully provide acceptable TS structures similar to the UDFT-optimized geometries at much lower computational cost. Our method will lead to substantial savings of computational time spent in the TS search for transition-metal-containing species.
We demonstrate the use of density gradient centrifugation for the efficient separation of Au nanoplates (NPTs) and nanoparticles (NPs). The particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis absorption spectroscopy. In addition, Au NPTs display stronger surface-enhanced Raman scattering (SERS) ability compared with that of Au NPs.
A porphyrin-based cubic cage (Cube) was reacted with a Pt(II)-based molecular H2-evolving catalyst, PtCl2(dmbpy) (PtDmb; dmbpy: 4,4′-dimethyl-2,2′-bipyridine), to give Cubes incorporated with one or two equivalents of PtDmb, i.e., Cube(PtDmb) and Cube(PtDmb)2, which was confirmed by ESI-TOF MS spectroscopy. A photochemical H2-evolving system consisting of EDTA (sacrificial electron donor), [Ru(bpy)3]2+ (photosensitizer), and methylviologen (electron relay) was used to demonstrate that the catalyst encapsulated can also serve as an effective H2-evolving catalyst.
A series of Boc-(l-Ala-Aib)n-OCH3 (n = 2, 4, 6, 8) and Boc-(l-Leu-Aib)n-OCH3 (n = 2, 4, 6, 8) peptides were synthesized and subjected to terahertz time-domain (THz-TD) spectroscopy. Signals specific to helical peptides were observed around 2 and 3 THz, which were assignable to accordion-like oscillation modes, based on DFT calculations. Boc-(l-Ala-Aib)8-OCH3 showed intensified signal when compared with Boc-(l-Leu-Aib)8-OCH3, which is due to the large amplitude of the accordion-like oscillation. The accordion-like oscillation modes are discussed in relation with the higher ability of (l-Ala-Aib)8 than (l-Leu-Aib)8 as an electron-transfer mediator.
Highly catalytic performance of La2O3 in transfer hydrogenation reactions was achieved following pretreatment involving a sequence of heat treatments under different atmospheric gases. Furfural (FFR) was converted to furfuryl alcohol (FFA) in a very selective manner (98% conversion, with 96% selectivity) using La2O3 that had been calcined under air at 923 K and treated under H2 at 673 K. Strongly basic sites and weakly acidic sites were generated after heat pretreatment.