Institutional Repository of Dalian Institute of Chemical Physics, CAS
Not a member yet
45557 research outputs found
Sort by
Crystal structure, magnetic and heat capacity properties of a new chiral mononuclear iron(II) compound
No full textA new chiral mononuclear iron(II) compound, formulated as {[Fe(ACBP)(3)]center dot(ClO4)} (1, ACBP = (S,S)-3,3'-(1,2-dimethylpropanedioxy)-2,2'-bipyridine), has been synthesized and structurally characterized. The magnetic study revealed that compound 1 possesses antiferromagnetic exchange interactions between Fe(II) ions through the hydrogen bonds. The low-temperature heat capacity of compound 1 was measured in the temperature range from 1.9 to 300 K using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). Additionally, the thermodynamic functions in the experimental temperature range have been derived by fitting the heat capacity data to a series of theoretical and empirical models. The standard molar heat capacity, entropy and enthalpy of compound 1 at 298.15 K and 0.1 MPa have been determined to be = (1036.9 +/- 10.4) J mol(-1) K-1, = (1059.6 +/- 10.6) J mol(-1) K-1 and = (160.29 +/- 1.60) kJ mol(-1), respectively
Cobalt-graphene nanomaterial as an efficient catalyst for selective hydrogenation of 5-hydroxymethylfurfural into 2,5-dimethylfuran
No full textThe synergy of single Co atoms/Co clusters and CoOx nanoparticles, as well as reduced graphene oxide, enabled a Co-graphene nanomaterial to exhibit superior catalytic performance in the hydrogenation of HMF into DMF, including the omission of pre-reduction treatment, high specificity for cleavage of C?O/C-O bonds, excellent catalytic activity and enhanced stability
Rapid Identification of Bacteria by Membrane-Responsive Aggregation of a Pyrene Derivative
No full textAn imidazolium-derived pyrene aggregation was developed to rapidly identify and quantify different bacteria species. When the nonemissive aggregates bound to the anionic bacteria surface, the sensor disassembled to turn on significant fluorescence. At the same time, ratiometric signals between pyrene monomer and excimer emission were controlled by different interactions with various bacteria surfaces. The resulted different fluorescent emission profiles then were obtained as fingerprints for various bacterial species. By converting emission profiles directly into output signals of two channels, fluorescence increase and ratiometric change, a two-dimensional analysis map was generated for bacteria identification. We demonstrated that our sensor rapidly identified 10 species of bacteria and 14 clinical isolated multidrug-resistant bacteria, and we determined their staining properties (Gram-positive or Gram-negative)
Surface modification with highly-homogeneous porous silica layer for enzyme immobilization in capillary enzyme microreactors
No full textImmobilized enzyme micro-reactors (IMERs) are of vital importance in developing miniaturized bioanalytical systems and have promising applications in various biomanufacturing. An inherent limitation in designing IMERs is the one-dimensional cylindrical geometry of micro-channels that offers limited exposed surface area for molecular reorganization and enzyme immobilization. In this study, we report a robust capillary-IMER based on a three dimensional porous layer open tubular (3D-PLOT) column which is prepared by an easy-to-control surface modification strategy via single-step in situ biphasic reaction. The 3D-PLOT column with highly uniform porous geometry and narrow distribution of porosity can greatly enhance the surface-area-to-volume ratio of the micro-channels, showing the beneficial effects for enzyme immobilization to enhance reaction efficiency and shorten analysis time. Taking trypsin as a model enzyme, enzymatic activities of immobilized enzyme are analyzed. We compare enzyme assays using the proposed 3D-PLOT-IMER with those using normal capillary-IEMR without surface modification as well as free trypsin. The 3D-PLOT-IMER exhibits excellent stability and inter/intra-day reproducibility, and these characteristics imply the reliability of the proposed IMERs for accurate enzyme assay. The feasibility of the proposed method for potential application in biological analysis is demonstrated by coupling the 3D-PLOT-IMER with a nano-LC-MS/MS system for online digestion of standard proteins, cell extraction and living Hela cells. Our study show that the surface modification with the proposed 3D-porous layer is a simple and efficient approach for enzyme immobilization, and could be widely suitable for different kinds of IMERs
Investigation on the reaction area of PEMFC at different position in multiple catalyst layer
No full textTo study the oxygen reduction reaction (ORR) at different through-plane position in catalyst layer, a multiple catalyst layer (MCL) was designed in which the reaction area could move from proton exchange membrane (PEM) to gas diffusion layer (GDL). The reaction layer (layer Y) was sandwiched between proton conduct layer (layer X) and air diffusion layer (layer Z) to simulate the real reacting process in an ordinary catalyst layer. Three MEA samples with MCL were made, the reaction area was set near the PEM, in the middle of catalyst layer and near the GDL, respectively. According to the polarization curves, the position of reaction area in catalyst layer has obvious influence on cell performance and the output current at the same working voltage increased when the reaction area moved towards GDL. Besides, how the charge transfer resistance and mass transport resistance of reaction area at different position in CL changed when output current increased has also been studied in this work using EIS. Simulation results about current and proton distribution have also been verified in this work. (C) 2019 Elsevier Ltd. All rights reserved
Pt/ZSM-22 with Partially Filled Micropore Channels as Excellent Shape-Selective Hydroisomerization Catalyst
No full textPt/ZSM-22 with partially filled micropore channels (Pt/Z22-PF) was prepared through a facile in-situ coke deposition approach. Compared with conventional Pt/ZSM-22 with evacuated micropore channels (Pt/Z22-E), Pt/Z22-PF exhibits much higher activity and isomer yield in n-dodecane hydroisomerization. Specifically, the turnover frequency of n-dodecane and the maximum multibranched isomer yield on Pt/Z22-PF are about twice that on Pt/Z22-E (314 vs. 144 h(-1), 49 % vs. 29 %). Theoretical simulations and adsorption experiments demonstrate that the diffusion limitation of hydrocarbon and the accessibility of acid sites inside the micropore channels are reduced dramatically because of the partial fill. This is beneficial for the diffusion of alkene intermediates and the suppression of cracking reactions, resulting in a superior activity and high yield of isomers, especially multibranched isomers
Reversible Hydrogen Uptake/Release over a Sodium Phenoxide-Cyclohexanolate Pair
No full textHydrogen uptake and release in arene-cycloalkane pairs provide an attractive opportunity for on-board and off-board hydrogen storage. However, the efficiency of arene-cycloalkane pairs currently is limited by unfavorable thermodynamics for hydrogen release. It is shown here that the thermodynamics can be optimized by replacement of H in the -OH group of cyclohexanol and phenol with alkali or alkaline earth metals. The enthalpy change upon dehydrogenation decreases substantially, which correlates with the delocalization of the oxygen electron to the benzene ring in phenoxides. Theoretical calculations reveal that replacement of H with a metal leads to a reduction of the HOMO-LUMO energy gap and elongation of the C-H bond in the alpha site in cyclohexanolate, which indicates that the cyclohexanol is activated upon metal substitution. The experimental results demonstrate that sodium phenoxide-cyclohexanolate, an air- and water-stable pair, can desorb hydrogen at ca. 413 K and 373 K in the solid form and in an aqueous solution, respectively. Hydrogenation, on the other hand, is accomplished at temperatures as low as 303 K
Coherent interference of molecular electronic states in NO by two-color femtosecond laser pulses
No full textQuantum coherence interference between electronic states in molecules is an important factor for controlling electronic and nuclear dynamics in photoinduced physics and chemistry. We measure and model molecular angle-dependent photoionization yields to explore coherent interference dynamics between quasiequal energy electronic-vibrational states of the nitric oxide molecule, NO, by ultrafast phase-controlled two-color femtosecond laser pulses. We demonstrate by experiment and theory that the photoelectron angular distribution of NO, where two excited electronic states are coherently combined by ultrafast pulses, is a function of the relative phase of the pulses, and the photoelectron kinetic energy. The modification of photoelectron emission angular patterns encodes the information of the coherence via electronic state interference. The result allows access to phase-dependent state correlations and ultrafast vibrationic dynamics in molecules
Kinetic modeling of methanol to olefins process over SAPO-34 catalyst based on the dual-cycle reaction mechanism
No full textA kinetic model for methanol to olefins (MTO) process over SAPO-34 catalyst was established based on the dual-cycle reaction mechanism. Simplifications were made by assuming olefins-based cycle as virtual species S, and aromatics-based cycle as R, where the former mainly accounts for the production of higher olefins, while the latter for lower olefins. Transformation of S to R was considered with the participation of methanol and olefins. Meanwhile, a phenomenological deactivation model was developed to account for the deactivation process. With the proposed model, the evolution of methanol conversion and product selectivity with time on stream could be predicted, and key reaction characteristics, such as the autocatalytic nature of the reaction, could also be captured due to its mechanism-based nature. Further simulations of MTO reactors at different scales validated the robustness and applicability of the current model in MTO process development and optimization. (c) 2018 American Institute of Chemical Engineers AIChE J, 65: 662-674, 201
HPLC with cellulose Tris (3,5-DimethylPhenylcarbamate) chiral stationary phase: Influence of coating times and coating amount on chiral discrimination
No full textCoating cellulose tris (3,5-dimethylphenylcarbamate) (CDMPC) on silica gels with large pores have been demonstrated as an efficient way for the preparation of chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC). During the process, a number of parameters, including the type of coating solvent, amount of coating, and the method for subsequent solvent removing, have been proved to affect the performance of the resultant CSPs. Coating times and the concentration of coating solution, however, also makes a difference to CSPs' performance by changing the arrangement of cellulose derivatives while remaining the coating amount constant, have much less been studied before, and thereby, were systematically investigated in this work. Results showed that CSPs with more coating times exhibited higher chiral recognition and column efficiency, suggesting that resolution was determined by column efficiency herein. Afterwards, we also investigated the effect of coating amount on the performance of CSPs, and it was shown that the ability of enantio-recognition did not increase all the time as the coating amount; and four of seven racemates achieved best resolution when the coating amount reached to 18.37%. At the end, the reproducibility of CDMPC-coated CSPs were further confirmed by two methods, ie, reprepared the CSP-0.15-3 and reevaluated the effect of coating times