An esterase, 3,4-dihydrocoumarin hydrolase, was directly immobilized into silica microcapsules. The hydrolysis reaction of 3,4-dihydrocoumarin by a macroporous silica microcapsule immobilizing the esterase was faster than those by mesoporous ones. Using this macroporous microcapsule, the hydrolysis reaction of p-nitrophenyl acetate proceeded with comparable rate to non-immobilized esterase.
The adsorption behavior of cationic organic molecules was examined on a clay surface. Systematically chosen pyridinium salts and artificially synthesized anionic clay were used. The adsorption equilibrium constants and the free energy for adsorption (ΔG) values were obtained for each pyridinium salt. It was discovered that ΔG values were proportional to the cross-sectional area of the pyridinium salt. These results indicate that hydrophobic and/or van der Waals interactions play an important role for the adsorption process.
A platinum-group-metal-free catalyst comprising Fe-Ni alloy nanoparticles on a γ-Al2O3 support was investigated for use in three-way catalytic converters, with particular attention being paid to its NO reduction activity. The catalyst showed activity for the simultaneous removal of NO, CO, and C3H6 in the stoichiometric NO-CO-C3H6-O2 reaction. Low-oxidation-state Fe sites were found to be effective for NO reduction, while their oxidation by this reaction induced catalyst deactivation. Ni atoms adjacent to the low-oxidation-state Fe atoms were found to stabilize them by catalyzing the consumption of the O atoms in the nanoparticles for CO oxidation, which indirectly promoted further NO reduction.
Five novel heterogeneous mononuclear complex-anchored Ru(III) have been efficiently sono-synthesized and characterized by utilizing several analytical techniques. The assembled complexes could be utilized as effective, robust and recyclable (up to eight consecutive runs) catalysts for one-pot transformation of a vast array of nitriles and aldehydes to primary amides in H2O under aerobic conditions. Moreover, some unreported di- and tetra-amide derivatives were obtained also under the optimal conditions. The results of ICP/OES analysis demonstrated that there is no detected leaching of the recycled catalyst, which suggests the real heterogeneity of the present protocol. The present Ru-complexes exhibited superiority compared to other reported catalysts for amide preparation in terms of low catalyst load, short reaction time, low operating temperature, no hazardous additives required, and high values of TON (990) and TOF (1980 h−1).
The KHMDS-catalyzed tertiary alkylation of aldehydes, ketones or imines using tertiary benzylic organoboronates is reported. This protocol permitted the use of tertiary benzylic alkylboronates as the tertiary alkyl anion for construction of highly congested contiguous sp3 carbon centers. The mild and transition-metal-free reaction conditions are attractive features of the protocol.
A novel zinc-based infinite coordination polymer (Zn-ICP) with functionalized ligand is fabricated by a simple dripping method under mild conditions. Zn-ICP as sensing material shows fast response and high selectivity to ammonia at room temperature due to different metal nodes compared with isomorphic Ni-ICP.
Herein, we achieved nearly quantitative and selective mechanochemical conversion of CO2 to CH4 in the presence of H2O mediated by collision and friction of stainless steel balls without external heating, revealing that this conversion involves the formation of metal carbonates and hydrogenation by H2 gas in situ generated from H2O.
Miniaturized machines have open up a new dimension of chemistry, studied usually as an average over numerous molecules or for a single molecule bound on a robust substrate. Mechanical motions at a single molecule level, however, are under quantum control, strongly coupled with fluctuations of its environment — a system rarely addressed because an efficient way of observing the nanomechanical motions in real time is lacking. Here, we report sub-millisecond sub-Å precision in situ video imaging of a single fullerene molecule shuttling, rotating, and interacting with a vibrating carbon nanotube at 0.625 milliseconds(ms)/frame or 1600 fps, using an electron microscope, a fast camera, and a denoising algorithm. We have achieved in situ observation of the mechanical motions of a molecule coupled with vibration of a carbon nanotube with standard error as small as 0.9 millisecond in time and 0.01 nm in space. We have revealed rich molecular dynamics, where motions are non-linear, stochastic and often non-repeatable, and a work and energy relationship at a molecular level previously undetected by time-averaged measurements or microscopy. The molecular video recording at a 1600-fps rate exceeds by 100 times the previous records of continuous recording of molecular motions.
Regioselective hydrosilylation of aliphatic olefins catalyzed by Co-iminobipyridine complexes, Co〈R〉, were investigated, where R indicates a substituent on the imino nitrogen in an iminobipyridine ligand (iminobypyridine = [2,2′-bpy]-6-C(Me)=N-R). Syntheses of two complexes, Co〈Mes〉 (Mes = 2,4,6-trimethylphenyl) and Co〈Cy〉 (Cy = cyclohexyl), and comparison of their catalytic activity for hydrosilylation of 1-octene with diphenylsilane revealed that the reaction system using Co〈Mes〉 produced a mixture of anti-Markovnikov and Markovnikov hydrosilylation products, whereas that using Co〈Cy〉 produced the anti-Markovnikov product selectively. Crystal structures of these complexes implied that a catalytically active species derived from Co〈Cy〉 has narrower active space for hydrosilylation than that from Co〈Mes〉. According to the Chalk-Harrod mechanism, there are two types of hydrosilylated products (anti-Markovnikov and Markovnikov products), which stem from the way of terminal olefin insertion into an M-H bond (that is 1,2- or 2,1-insertion). One of the intermediates derived from Co〈Cy〉 in the Chalk-Harrod mechanism has hydride and silyl ligands. In the step of olefin insertion into the Co-H bond, 1,2-insertion is more likely to occur from the steric point of view, leading to selective formation of the anti-Markovnikov product.
Binding of dodecylpyridinium chloride (DPC) to water-soluble calix[n]arenes (n = 4, 6, 8) (CALXSn) has been studied by potentiometric titration. The binding isotherms were found to be composed of two phases; one is strong specific binding to one site and the other is cooperative binding to residual sites. Thermodynamic parameters for the specific binding suggests that the complex is stabilized by van der Waals force between the alkyl chain of DPC and hydrophobic cavity of CALXSn in addition to electrostatic force between opposite charges of DPC and CALXSn. The specific site was highly reduced in the presence of cerium cation for CALXS4 and of uranyl cation for CALXS6 and by the pH change from 7.0 to 12.5 for CALXS8. These effects were interpreted by competitive binding of the metal cations and the pyridinium cation of DPC to the specific sites of CALXS4 and CALXS6, and by deprotonation of hydroxyl group having pKa = 10.1 and/or accompanying conformational change of CALXS8. The cooperative binding takes place in one stage for CALXS4 and CALXS6 but in two stages for CALXS8. The multiple-stage cooperativity was consistent with ‘inverted double cone’ conformation of CALXS8. The results were discussed as a model of ligand binding to protein local structure.
Flexible and aromatic photofunctional system (FLAP) has been recognized as an emerging class of versatile π-conjugated molecules. Here we report a viscosity-probing function of flapping peryleneimide and compare its photophysical properties with representative molecular rotors, DCVJ and BODIPY, as well as flapping anthraceneimide. In this comparison, polarity dependence is not negligible in the fluorescence (FL) of the flapping peryleneimide, but it shows more sensitive FL response in a low viscosity range (0.3–3.1 cP), which enables discrimination of different n-alkanes by the FL lifetime measurement. Extremely high photostability of the flapping peryleneimide has also been confirmed, which is promising for the characteristic FL imaging.
The procyanidin B series is a family of dimeric flavonoids composed of catechin(s) and/or epicatechin(s) with a C4-C8′ interflavan bond. We previously reported four TMSOTf-promoted couplings for C4-C8′ interflavan bond formations by using tethered catechin(s) and/or epicatechin(s). Although one of the reactions did not provide the coupling product, the other three reactions proceeded stereoselectively at the C4-position to provide stereochemically diversified products at C3 and C3′ positions toward the procyanidin B series. Here we report computer-assisted models of transition states for the C-C bond formations to explore origins of the stereoselectivity. A systematic search of the transition states using truncated compounds provided TS-Ad, TS-Ba or TS-Cd as the most energetically favorable transition state in each of the three reactions to reproduce the C4-stereoselectivity of the experiments. Exploration of origins of the stabilized energies of TS-Ad, TS-Ba, and TS-Cd by NCIPLOT demonstrated the importance of attractive non-covalent interactions.
There has been a growing interest in stainless steel (SS) corrosion due to massive economic losses. Current efforts are mainly devoted to forming Cr2O3 film or organic coatings on SS surfaces. However, the relevant chromate is a carcinogen and the traditional organic coatings are inefficient for electrochemical corrosion. Here, we prepared a novel superhydrophobic-conductive anti-corrosion polyaniline-silica (PANI-SiO2) coating, the internal conductive polyaniline layer effectively reduces electrochemical corrosion, the external superhydrophobic silica layer obviously reduces chemical corrosion. Compared with 304 stainless steel (304SS), the corrosion potential (Ecorr) of the PANI-SiO2 increases to more than 331 mV (SCE), the corrosion current (Icorr) is reduced by more than one order of magnitude, and the anti-corrosion efficiency reaches 97.51%. Meanwhile, the PANI-SiO2 coating has good long-term anti-corrosion performance for 304SS.
Localized surface plasmon resonance (LSPR) based nano-plasmonic biosensors have attracted great attentions due to rapid detection and label-free capability. Aiming to obtain a high performance LSPR sensor chip, a cauliflower-like nanopillar (CLNP) structure was fabricated based on the cyclo-olefin polymer (COP) material which could increase the sensitivity according to the “hotspots” effect theory. An oxygen plasma etching procedure was introduced to the chip fabrication process to carve the nanopillar surface prepared by nanoimprinting lithography (NIL) into the cauliflower-like nanostructures. In this paper, the cauliflower-like nanopillar structured sensor chip was successfully obtained and the results confirmed that this sensor chip has higher sensitivity compared to an untreated nanopillar structured chip. Meanwhile, the biosensing capability was verified by cell interleukin-6 (IL-6) immunoassay. This approach provides an easy way to fabricate mass-producible LSPR biosensor chips for cell cytokine secretion detection.
Multiple-angle incidence resolution spectrometry (MAIRS), originally developed in our group, is a unique spectroscopic technique for analyzing the structure of molecular aggregates in a thin film, which requires only the refractive index of the film for attaining an analytical accuracy of three significant digits. Since MAIRS is robust to the surface roughness of the film, rough films prepared by using the spin-coating, bar-coating, or drop-casting techniques can be analyzed with a good reproducibility. MAIRS makes the best use of a Fourier transform infrared (FT-IR) spectrometry, which enables us to discuss molecular conformation, packing, polymorphs etc. as well as the molecular orientation. At the moment, MAIRS has two options, pMAIRS and MAIRS2. pMAIRS has already been established and the application is spreading. MAIRS2 is the newest technology, which frees us from FT-IR specific problems, that is to say, interference of water-vapor peaks and of optical fringes. In this review, the cutting-edge analytical technology of MAIRS is described comprehensively for convenience of both pMAIRS and MAIRS2 users.
In this report, nitrogen-, boron- and boron/nitrogen-doped graphene and nitrogen-doped carbon nanohorn were prepared. Electrochemical analysis has shown the higher capacitance performance of the nitrogen-doped graphene (NG) electrode, because nitrogen provides free valence electron to interact with electrolyte. Then magnetic metal oxides were in situ hybridized to a nitrogen-doped graphene to produce magnetic metal oxide/NG hybrid materials, and the electrochemical measurements of the prepared hybrid material electrodes were conducted without and with the external magnetic field (8.98 mT at the inflection point) of using a Helmholtz coil. The specific capacitance took an increasing order of NiO/NG (697 F/g, 747 F/g) < Co3O4/NG (963 F/g, 1092 F/g) < Fe3O4/NG (973 F/g, 1254 F/g) in an external magnetic field of (0 mT, 8.98 mT) at a scan rate of 5 mV/s. Although these electrodes displayed high capacitance and better charge/discharge profile, cycle retention (83 to 92% under no magnetic field) was not necessarily good or it fluctuated under 8.98 mT. These behaviours by the addition of magnetic metal oxides and external magnetic field are due to the electrical conductivity of metal oxides and the Lorentz force effect of the magnetic field, respectively. Thus, it can be confirmed that Fe3O4/NG hybrid has higher potential as a magnetic material electrode for supercapacitors and the magnetic field enhances the capacitance.