COLLOIDS AND SURFACES B-BIOINTERFACES
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2014
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IF 4.287
Chunhua Gu,Vanminh Le,Meidong Lang,Jianwen Liu
Biodegradable graft copolymer, chitosan- graft -poly( ɛ -caprolactone) (CS- g -PCL) was synthesized via ring opening polymerization and characterized by 1 H NMR and FTIR spectroscopy. Then graft copolymers were self-assembled into micelles as drug delivery system. To evaluate drug-polymer compatibility, the Flory–Huggins interaction parameter between 5-fluorouraci (5-Fu) and hydrophobic segment was calculated. The result was in agreement with experimental data from drug loading content and drug loading efficiency. Meanwhile, DLS and TEM were utilized to evaluate the trend of particle size and morphology in aqueous solution with different repeating units of ɛ -CL. The in vitro drug release data was fitted with three kinetic models, usually applied in the drug delivery system. Results indicated that the release of 5-Fu was controllable and the release half-time could reach as long as 54.46 h, much slower than that of free 5-Fu. Cytotoxicity evaluation and cellular apoptosis study suggested good biocompatibility of CS- g -PCL micelles. Moreover, 5-Fu loaded micelles could delay the release of drug and exert comparable cytotoxicity against A549 cells.
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Journal of the Taiwan Institute of Chemical Engineers
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2014
·
IF 2.637
Chuan-Jun Yue,Miao-Miao Gan,Li-Ping Gu,Ya-Feng Zhuang
Cu/ZSM-5 prepared by in situ impregnated reduction was used for the catalytic dehydration of glycerol under solvent-free conditions. The catalyst was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), ammonia temperature programmed desorption (NH 3 -TPD), and thermogravimetry-differential scanning calorimetry (TG-DSC) analyses. Results showed that the nano-copper in Cu/ZSM-5 was evenly distributed onto the surface of ZSM-5 pores. Under the optimum conditions of the catalytic dehydration of glycerol, conversion was 92.1 wt.%. The selectivities of acrolein and acetol were 80.4 wt.% and 11.5 wt.%, respectively. Moreover, the low temperature favored for acetol selectivity. The synergic catalysis of Cu and ZSM-5 through the enol intermediate was responsible for the selectivity in the catalytic dehydration of glycerol.
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RSC Advances
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2013
·Vol. 4
·期 8
·4194-4202
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IF 2.562
Jinzhu Chen,Guoying Zhao,Limin Chen
Direct conversion of fructose into 5-hydroxymethylfurfural (HMF) and alkyl levulinate is achieved by making use of ionic liquid-based polyoxometalate salts (IL-POMs) as solid acid catalysts. Among these solid acids, phosphotungstic acid-derived IL-POM shows the highest catalytic performance in both the HMF and ethyl levulinate (EL) formation. A study for optimizing the reaction conditions such as the reaction time and the temperature has been performed. High HMF and EL yields of up to 99% and 82%, respectively, are obtained from fructose under the investigated conditions. Moreover, the generality of the catalyst is further demonstrated by processing representative di- and polysaccharides such as sucrose and inulin with good yields to HMF (76% from inulin and 48% from sucrose) and EL (67% from inulin and 45% from sucrose), again under mild conditions, thereby eliminating the separate hydrolysis step before the dehydration reaction. The catalyst recycling experiment indicates that the adsorption and accumulation of oligomeric products on the catalyst surface results in a partial deactivation of catalyst. The mechanism research reveals that a major pathway for EL formation involves a fructose-to-HMF transformation followed by HMF etherification and rehydration of HMF-ether to give EL. The research highlights an efficient, environment-friendly and recyclable solid acid for biomass valorization.
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CATALYSIS TODAY
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2013
·
IF 2.98
Tong Zhang,Xiongfu Zhang,Xinjuan Yan,Lu Lin,Haiou Liu,Jieshan Qiu,King Lun Yeung
A well-designed Pd/ZSM-5@ZIF-8 core–shell structure has been prepared by application of a combination of seed-induction synthesis strategy and self-assembly synthesis techniques. First, uniform ZSM-5 particles with micron size and high crystallinity were prepared from organic-template-free gel systems containing 200 nm ZSM-5 seeds and exchanged with Pd(NO 3 ) 2 aqueous solution. Then incompatibility between the Pd/ZSM-5 core material and ZIF-8 shell precursor was circumvented by surface modification using a layer by layer self-assembly of polyelectrolyte, followed by a subsequent two-step temperature synthesis process inducing the formation of continuous and well-intergrown ZIF-8 shell. Thickness of ZIF-8 shell can be simply tuned by monitoring the assembly cycles. Furthermore, hydrogenations of 1-hexene and cyclohexene were chosen as model reactions to evaluate the catalytic behavior of the Pd/ZSM-5@ZIF-8 core–shell architecture and tert-dodecylthiol was used as a poison to test its anti-poisoning ability. Results show that such core–shell architecture exhibits excellent poison resistance and selectivity control properties for the hydrogenation reactions and can be potentially used as a membrane reactor in the field of heterogeneous catalysis.
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Chemistry-An Asian Journal
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2013
·Vol. 8
·期 7
·1504-1513
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IF 4.572
Si-Hai Wu,Yu-Wu Zhong,Jiannian Yao
Graphical NN-CNN breaking news : 2,3-Di(2-pyridyl)-5-phenylpyrazine, which is able to bind two metals through a NN-CNN-type coordination mode, has been designed and synthesized. A RuPt heterobimetallic complex with this bridging ligand shows near-infrared emission at 750 nm, with a quantum yield of 0.41 % and an excited-state lifetime of 170 ns. en This link goes to a English section zh This link goes to a English section A new bridging ligand, 2,3-di(2-pyridyl)-5-phenylpyrazine (dpppzH), has been synthesized. This ligand was designed so that it could bind two metals through a NN-CNN-type coordination mode. The reaction of dpppzH with cis -[(bpy) 2 RuCl 2 ] (bpy=2,2′-bipyridine) affords monoruthenium complex [(bpy) 2 Ru(dpppzH)] 2+ ( 12+ ) in 64 % yield, in which dpppzH behaves as a NN bidentate ligand. The asymmetric biruthenium complex [(bpy) 2 Ru(dpppz)Ru(Mebip)] 3+ ( 23+ ) was prepared from complex 12+ and [(Mebip)RuCl 3 ] (Mebip=bis( N -methylbenzimidazolyl)pyridine), in which one hydrogen atom on the phenyl ring of dpppzH is lost and the bridging ligand binds to the second ruthenium atom in a CNN tridentate fashion. In addition, the RuPt heterobimetallic complex [(bpy) 2 Ru(dpppz)Pt(CCPh)] 2+ ( 42+ ) has been prepared from complex 12+ , in which the bridging ligand binds to the platinum atom through a CNN binding mode. The electronic properties of these complexes have been probed by using electrochemical and spectroscopic techniques and studied by theoretical calculations. Complex 12+ is emissive at room temperature, with an emission λ max =695 nm. No emission was detected for complex 23+ at room temperature in MeCN, whereas complex 42+ displayed an emission at about 750 nm. The emission properties of these complexes are compared to those of previously reported Ru and RuPt bimetallic complexes with a related ligand, 2,3-di(2-pyridyl)-5,6-diphenylpyrazine. en This link goes to a English section zh This link goes to a English section 1
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JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
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2014
·Vol. 52
·期 19
·2715-2724
·
IF 3.245
Jizhen Zhang,Aihua Li,Huihui Liu,Dongjiang Yang,Jingquan Liu
A recyclable solid-state photoinitiator based on the surface modified niobium hydroxide is prepared and successfully introduces into reversible addition–fragmentation chain transfer (RAFT) polymerization under visible light illumination. It is revealed by gel permeation chromatography analysis that well-defined polymers with controlled molecular weight and narrow polydispersity index can be achieved when the feed ratio of photoinitiator to the RAFT agent was controlled properly. It is also found that the polymerization is highly responsive to external stimulus and when light is removed from the system polymerization stops almost immediately. In addition, the photoinitiator can be recycled and reused to initiate the polymerization for many times without significant decrease of initiation efficiency. At last, the mechanism for the light initiated polymerization is proposed to illuminate how the initiation and chain propagation proceed. This facile, green and visible light initiation methodology could attract more and more applications in polymer science with the depletion of fossil energy. A recyclable solid-state photoinitiator based on the surface modified niobium hydroxide was prepared and successfully introduced into reversible addition–fragmentation chain transfer (RAFT) polymerization under visible light illumination. It is revealed that well-defined polymers with controlled molecular weight and narrow polydispersity index (PDI) can be achieved when the feed ratio of photoinitiator to the RAFT agent was controlled properly. It is also found that the polymerization is highly responsive to light initiation. In addition, the photoinitiator can be recycled and reused to initiate the polymerization for many times without significant decrease of initiation efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52 , 2715–2724
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APPLIED CATALYSIS A-GENERAL
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2014
·
IF 3.674
Xiuquan Jia,Jiping Ma,Min Wang,Zhongtian Du,Fang Lu,Feng Wang,Jie Xu
The promoted effect of Cu(NO 3 ) 2 on aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) catalyzed by VOSO 4 in acetonitrile was intensively investigated. It was revealed that Cu(NO 3 ) 2 facilitated the activation of VOSO 4 to generate active V 5+ species via the generation of NO x gas. The high DFF selectivity is ascribed to Cu 2+ cation which can effectively prohibit oxidative C C bond cleavage reaction of HMF and prevent radical reaction of DFF to humins. In addition, the polarity of solvent plays a great role on high selectivity of DFF.
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FUEL
·
2013
·
IF 3.357
Anqiu Liu,Bing Liu,Yimei Wang,Rongshen Ren,Zehui Zhang
Synthesis of 5-ethoxymethylfurfural (EMF) from the etherification of 5-hydroxymethylfurfural (HMF) and the dehydrative etherification of fructose over K-10 clay supported dodecatungstophosphoric acid (abbreviated as K-10 clay-HPW). 30% wt.% K-10 clay-HPW was found to be the efficient and robust catalyst for the synthesis of EMF. The highest EMF yield of 91.5% was obtained from HMF after 10 h at 100 °C. Further more, the catalyst also showed high catalytic activity for the dehydrative etherification of fructose with EMF yield of 61.5%. The reaction work-up is very simple and the catalyst could be reused several times without the significant loss of its catalytic activity.
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RSC Advances
·
2017
·Vol. 7
·期 23
·13808-13816
·
IF 3.108
Cheng-Yang Cao,Song Lu,Dan Zhang,Lun-Lun Gong,He-Ping Zhang
The 5AT/Sr(NO3)2 mixture has recently attracted attention as a gas-generating agent for use in novel fire-suppression applications. However, it cannot provide the desired combustion behavior alone. Thus, nitroguanidine (NQ) was added as a fuel component to 5AT/Sr(NO3)2 in attempt to improve the mixture's combustion behavior. The effects of NQ on the thermal and burning characteristics of 5AT/Sr(NO3)2 were investigated. Thermogravimetry-differential scanning calorimetric (TG-DSC) analysis with four heating rates (5, 10, 15, 20 K min−1) under a nitrogen atmosphere was performed to determine the thermal characteristics and non-isothermal reaction kinetic parameters. The addition of NQ decreases the activation energy of the Stage II and III decomposition reaction, and accelerates the redox reaction and decomposition of Sr(NO3)2. Thermodynamic calculations and measurements of temperature profile and liner burning rates were performed to evaluate the combustion characteristics. Adding NQ decreased the adiabatic combustion temperature, outlet temperature, average flame height, flame oscillation frequency and pressure exponent of Vieille's equation, and increased the gas output and linear burning rate. Notably, mesa burning occurred when NQ was added, the mechanism of which is elaborated using a physical combustion model. The analysis deepens the understanding of when the gas-phase or condensed-phase reactions control the burning characteristics of the composite propellant.
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ChemCatChem
·
2017
·Vol. 9
·期 19
·3646-3654
·
IF 4.803
Bin Zhang,Qifan Wu,Chao Zhang,Xinluona Su,Ruhui Shi,Weiwei Lin,Yan Li,Fengyu Zhao
Graphical Stability from the support : The excellent stability of a Ru/ZSM-5 catalyst for levulinic acid hydrogenation in water relies on the higher tetrahedral-coordinated Al content and preferable pore connectivity in well-crystallized ZSM-5 zeolite, which suppress Ru aggregation and leaching and the formation of carbonaceous residues in the acidic environment. A long-life topic in the field of heterogeneous catalysis has been to develop supported catalysts that are stable against the aggregation of active metal and carbon deposition. Herein, we report a highly stable Ru/ZSM-5 catalyst for the hydrogenation of levulinic acid in water, which can be recycled at least 10 times without apparent loss of activity (conv. >95 %, yield >85 %). The influences of types of Al species, structure of support, Ru sizes, Ru leaching, and carbon deposition, etc. on activity and stability were discussed in detail. It was confirmed that the tetrahedral-coordinated framework Al in ZSM-5 contributed to the favorable metal–support interaction, and thus suppressed the aggregation and leaching of ruthenium during recycling. Besides, the suitable pore volume and channel network connectivity successfully prevent from deposition of carbonaceous residues.
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ACS Sustainable Chemistry & Engineering
·
2015
·
IF 4.642
Yunlei Zhang,Jianming Pan,Yating Shen,Weidong Shi,Chunbo Liu,Longbao Yu
Employing renewable and widely available feedstock of cellulose as a raw material for 5-hydroxymethylfurfural (HMF) production opens up the possibility of sustainable biorefinery schemes that do not compete with the food supply. In this work, novel and efficient Brønsted acidic polymer nanotubes were successfully prepared by chemical conjugating grafting −SO3H groups onto the surface of polydivinylbenzene (PDVB) nanotubes, which were derived from cationic polymerization of divinylbenzene. By simply adjusting the grafting amounts of hydrophilic −SO3H groups, catalysts with varied hydrophobic and hydrophilic surface wettability (i.e., catalyst-110° and catalyst-10°) could be obtained. It was demonstrated that as-prepared catalyst-10° possessed the higher strong (143 μmol g–1), very strong (614 μmol g–1), and total acidity (786 μmol g–1) than those of catalyst-110°. Besides, the catalytic performance of the synthesized catalyst-110° and catalyst-10° were investigated and compared for the conversion of cellulose to HMF in an ionic liquid (i.e., 1-ethyl-3-methyl-imidazolium chloride, [EMIM]-Cl) system. Particularly, catalyst-110° exhibited the highest HMF yield of 34.6% on a molar basis, which was comparable with that of catalyst-10° (i.e., 37.1%), indicating that its hydrophobic nature was beneficial for decreasing side-reaction of HMF which tend to convert to some other byproducts during the very one-pot reaction. Furthermore, both catalysts can be easily recovered and reused for at least four times without significant loss of their catalytic activities. This work was the continue efforts for fabrication and application solid catalyst for excellent conversion of one-pot cellulose to HMF.
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ACS Chemical Biology
·
2017
·
IF 4.995
Jun Xiong,Xiaona Liu,Qing-Yun Cheng,Shan Xiao,Lai-Xin Xia,Bi-Feng Yuan,Yu-Qi Feng
Toxic heavy metals have been considered to be harmful environmental contaminations. The molecular mechanisms of heavy-metals-induced cytotoxicity and carcinogenicity are still not well elucidated. Previous reports showed exposures to toxic heavy metals can cause a change of DNA cytosine methylation (5-methylcytosine, 5-mC). However, it is still not clear whether heavy metals have effects on the recently identified new epigenetic marks in both DNA and RNA, i.e., 5-hydroxymethylcytosine (5-hmC), 5-formylcytosine (5-foC), and 5-carboxylcytosine (5-caC). Here, we established a chemical labeling strategy in combination with liquid chromatography–electrospray ionization–mass spectrometry (LC-ESI-MS/MS) analysis for highly sensitive detection of eight modified cytidines in DNA and RNA. The developed method allowed simultaneous detection of all eight modified cytidines with improved detection sensitivities of 128–443-fold. Using this method, we demonstrated that the levels of 5-hmC, 5-foC, and 5-caC significantly decreased in both the DNA and RNA of mouse embryonic stem (ES) cells while exposed to arsenic (As), cadmium (Cd), chromium (Cr), and antimony (Sb). In addition, we found that treatments by heavy metals induced a decrease of the activities of 10–11 translocation (Tet) proteins. Furthermore, we revealed that a content change of metabolites occurring in the tricarboxylic acid cycle may be responsible for the decline of the derivatives of 5-mC. Our study shed light on the epigenetic effects of heavy metals, especially for the induced decline of the derivatives of 5-mC in both DNA and RNA.
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