Institute of Chemistry
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A convenient and efficient synthesis method to improve the emission intensity of rare earth ion doped phosphors: the synthesis and luminescent properties of novel SrO:Ce3+ phosphor
No full textConvenient, efficient synthesis methods that improve the emission intensity of rare earth ion doped phosphors are relatively rare. In this study, a simple modified solid-state reaction is proposed. This approach can greatly improve reaction temperature and overcome the requirement for harsh conditions. Its advantages come from the substitution of a solid-solid interface for a solid-gas interface. A novel Ce3+ doped SrO phosphor with an enhancive bright cyan emission is prepared and the photoluminescent properties of SrO:Ce3+ are first reported. This study will provide valuable clues for synthesizing many other ion doped functional materials besides rare earth ion doped luminescent materials
Effect of the initial stage of film growth on device performance of organic transistors based on dinaphtho[2,3-b:2 ',3 '-f]thieno[3,2-b]thiophene (DNTT)
Get PDFThe initial stage of organic film growth is considered to be vital for the carrier transport in organic thin-film transistors with bottom gate configuration. The same topographies of 40 nm dinaphtho[2,3-b:2',3'-f] thieno[3,2-b] thiophene (DNTT) films on para-sexiphenyl (p-6P) monolayer and bare SiO2 exhibited quite different field-effect mobilities, 1.9 and 0.1 cm(2)/V s, respectively. The further investigation indicated there were different growth behaviors at their initial stages of film growth. Column islands with high density were observed on SiO2, while lamina islands on p-6P monolayer due to the good diffusion ability and their good epitaxial relationship. The latter is beneficial to obtain high quality film with less boundaries and defects. The work demonstrated that the initial stage of film growth is an important factor to determine the device performance of organic transistors, which is significant to improve the device fabrication and optimize the device performance. (C) 2015 Elsevier B.V. All rights reserved
A comprehensive study of the enantioseparation of chiral drugs by cyclodextrin using capillary electrophoresis combined with theoretical approaches
No full textFour chiral drugs were enantioseparated by native beta-cyclodextrin (beta-CD) and negatively charged carboxymethyl-beta-cyclodextrin (CM-beta-CD) using capillary electrophoresis coupled with electro-chemiluminescence detection (CE-ECL). Using 50 mM pH 5.5 Tris-H3PO4 with 10 mM CM-beta-CD as a running buffer, high resolution efficiency could be obtained. With the help of isothermal titration calorimetry (ITC), nuclear magnetic resonance (NMR) and molecular modeling, the chiral recognition mechanism was comprehensively investigated. Thermodynamic parameters data from ITC revealed that CM-beta-CD exhibited stronger binding affinity with analytes than beta-CD, and that the driving forces of CM-beta-CD responsible for chiral recognition were mainly electrostatic interactions between negatively charged CM-beta-CD and positively charged analytes. In addition, from both a macroscopic and microscopic point of view, the results of NMR and molecular modeling investigation adequately confirm the conclusion by comparing the stereochemical structures of complexes. Combination of ITC, NMR and molecular modeling techniques not only can assist CE to investigate the chiral discrimination mechanism, but also can predict and guide CE enantioseparation efficiency conversely. (C) 2015 Elsevier B.V. All rights reserved
Carbon dots based fluorescent sensor for sensitive determination of hydroquinone
No full textIn this paper, a novel biosensor based on Carbon dots (C-dots) for sensitive detection of hydroquinone (H(2)Q) is reported. It is interesting to find that the fluorescence of the C-dots could be quenched by H(2)Q. directly. The possible quenching mechanism is proposed, which shows that the quenching effect may be caused by the electron transfer from C-dots to oxidized H(2)Q-quinone. Based on the above principle, a novel C-dots based fluorescent probe has been successfully applied to detect H(2)Q Under the optimal condition, detection limit down to 0.1 mu M is obtained, which is far below U.S. Environmental Protection Agency estimated wastewater discharge limit of 0.5 mg/L Moreover, the proposed method shows high selectivity for H(2)Q over a number of potential interfering species. Finally, several water samples spiked with H(2)Q are analyzed utilizing the sensing method with satisfactory recovery. The proposed method is simple with high sensitivity and excellent selectivity, which provides a new approach for the detection of various analytes that can be transformed into quinone. (C) 2015 Elsevier B.V. All rights reserved
Luminescence Properties of Ca2Ga2SiO7:RE Phosphors for UV White-Light-Emitting Diodes
No full textA series of Eu2+-, Ce3+-, and Tb3+-doped Ca2Ga2SiO7 phosphors is synthesized by using a high-temperature solid-state reaction. The powder X-ray diffraction and structure refinement data indicate that our prepared phosphors are single phased and the phosphor crystalizes in a tetrahedral system with the P (4) over bar 2m (113) space group. The Eu2+ - and Ce3+-doped phosphors both have broad excitation bands, which match well with the UV light-emitting diodes chips. Under irradiation of lambda = 350 nm, Ca2Ga2SiO7:Eu2+ and Ca2Ga2SiO7:Ce3+, Li+ have green and blue emissions, respectively. Luminescence of Ca2Ga2SiO7:Tb3+, Li+ phosphor varies with the different Tb3+ contents. The thermal stability and energy-migration mechanism of Ca2Ga2SiO7:Eu2+ are also studied. The investigation results indicate that the prepared Ca2Ga2SiO7:Eu2+ and Ca2Ga2SiO7:Ce3+, Li+ samples show potential as green and blue phosphors, respectively, for UV-excited white-light-emitting diodes
In-situ electrochemical route to aerogel electrode materials of graphene and hexagonal CeO2
No full textWe reported a one-step in-situ electrochemical route to synthesize 3D aerogel electrode materials including graphene and hexagonal CeO2 composites. The graphene/CeO2 aerogel can be formed via freeze-drying graphene/CeO2 colloidal solution that was obtained by electrochemical exfoliation of graphite anode and in-situ deposition of CeO2 nanoparticles on graphene sheets in mixing electrolyte of (NH4)(2)SO4/Ce(NO3)(3) and (NH4)(2)SO4/(NH4)(2)Ce(NO3)(6). The as-obtained CeO2 nanoparticles were closely contacted with graphene, which can enhance the synergistic effect between graphene and CeO2. It is interesting that the as-obtained CeO2 products possessed hexagonal crystal structure that was rarely reported. The Faradaic reactivity of the graphene/CeO2 composites as supercapacitor was enhanced with the increase of the concentration of Ce salts in initial electrolyte. The introduction of CeO2 to graphene electrode can lead to the presence of additional pseudocapacitance besides the electric double-layer capacitance. This simple one-step in-situ electrochemical route can be extended to synthesize various graphene/metal oxide aerogel electrode materials for electric energy storage. (C) 2015 Elsevier Inc. All rights reserved
Investigate the Binding of Catechins to Trypsin Using Docking and Molecular Dynamics Simulation
No full textTo explore the inhibitory mechanism of catechins for digestive enzymes, we investigated the binding mode of catechins to a typical digestive enzyme-trypsin and analyzed the structure- activity relationship of catechins, using an integration of molecular docking, molecular dynamics simulation and binding free energy calculation. We found that catechins with different structures bound to a conservative pocket S1 of trypsin, which is comprised of residues 189-195, 214-220 and 225-228. In the trypsin-catechin complexes, Asp189 by forming strong hydrogen bonding, and Gln192, Trp215 and Gly216 through hydrophobic interactions, all significantly contribute to the binding of catechins. The number and the position of hydroxyl and aromatic groups, the structure of stereoisomers, and the orientation of catechins in the binding pocket S1 of trypsin all affect the binding affinity. The binding affinity is in the order of Epigallocatechin gallate (EGCG) > Epicatechin gallate (ECG) > Epicatechin (EC) > Epigallocatechin (EGC), and 2R-3R EGCG shows the strongest binding affinity out of other stereoisomers. Meanwhile, the synergic conformational changes of residues and catechins were also analyzed. These findings will be helpful in understanding the knowledge of interactions between catechins and trypsin and referable for the design of novel polyphenol based functional food and nutriceutical formulas
Thermogel-mediated sustained drug delivery for in situ malignancy chemotherapy
No full textIn the past few decades, the in situ sustained drug delivery platforms present fascinating potential in sentinel chemotherapy of various solid tumors. In this work, doxorubicin (DOX), a model antitumor drug, was loaded into the thermogel of poly(lactide-co-glycolide)-block-poly( ethylene glycol)-block-poly(lactide-co-glycolide). The moderate mechanical property of DOX-loaded hydrogel was confirmed by rheological test. In vitro degradation revealed the good biodegradability of thermogel. The DOX-loaded hydrogel exhibited the sustained release profiles up to 30 days without and even with elastase. The improved in vivo tumor inhibition and reduced side-effects were observed in the DOX-incorporated hydrogel group compared with those in free DOX group. The excellent in vivo results were further confirmed by the histopathological evaluation or terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. The thermogel with great prospect may be used as an ideal controlled drug delivery platform for the designated and long-term antitumor chemotherapy. (C) 2015 Elsevier B.V. All rights reserved
New insights into the role of lattice oxygen in the catalytic carbonization of polypropylene into high value-added carbon nanomaterials
No full textCatalytic conversion of waste plastics into high value-added carbon nanomaterials (CNMs) has attracted increasing attention; however, the role of lattice oxygen in the carbonization of plastics still remains ambiguous. In this work, firstly, a nickel catalyst with different content of lattice oxygen was prepared by the sol-gel combustion synthesis method. Subsequently, the effect of lattice oxygen in the nickel catalyst on the catalytic carbonization of polypropylene (PP, an example of plastics) into CNMs was investigated. It was found that the yield of CNMs increased dramatically with the increasing content of lattice oxygen. Large and short platelet-like carbon fibers were obtained when the content of lattice oxygen was low. With the increasing content of lattice oxygen, small, winding and short carbon nanofibers were produced. When the content of lattice oxygen further increased, long, small and straight cup-stacked carbon nanotubes were formed. Besides, it was demonstrated that lattice oxygen not only prevented the coalescence of nickel catalyst nanoparticles into large particles and promoted their reconstruction into rhombic shape, but also facilitated the catalytic carbonization of PP degradation products. This work provides new insights into the carbonization mechanism of plastics and puts forward a novel chemical method to prepare CNMs with diverse morphologies by controlling the content of lattice oxygen in the catalyst
Facet-Dependent Effect of Well-Defined CeO2 Nanocrystals on the Adsorption and Dephosphorylation of Phosphorylated Molecules
No full textCeO2 nanocrystals (CN) with different morphologies (i.e., cube, octahedron, and rod) are prepared and the facet-dependent effect of these CeO2 nanocrystals on the adsorption and dephosphorylation of phosphorylated molecules is investigated for the first time using the model p-nitrophenyl disodium orthophorphate (p-NPP). Due to their different surface atomic configurations, the {111} and {110} facets have much higher adsorption capacity and kinetic catalytic activities than {100} facets. All the CeO2 nanocrystals can intensely promote the dephosphorylation reaction owing to the strong interaction between Ce cations and phosphoryl oxygens resulting in the cleavage of phosphoester bonds. As was expected, the above facet-dependent effect can be verified by the practical application results of the CeO2 nanocrystals on the capture and dephosphorylation of phosphopeptides. Thus, surface engineering could be a useful and feasible strategy for not only fundamentally understanding the interaction between crystal facets and molecules but also effectively developing high-performance functional materials