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Study on the supramolecular structure of sorbic acid inter-calated Zn-Al layered double hydroxides and its thermal decomposition

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Chinese Science Bulletin 2005年第22期50卷 2575-2581页

作者： David g. evans Ministry of Education Key Laboratory of Science and Technolog. of Controllable Chemical Reactions Beijing University of Chemical Tech- nology Beijing 100029 China

A novel org.nic-inorg.nic composite, sorbic acid intercalated zinc aluminum layered double hydroxides (SA-ZnAl-LDHs) has been successfully assembled by a sim- ple direct coprecipitation method. A holistic approach in- cluding.normal XRD, FT-IR, and UV-Vis measurements and simultaneous Tg.DTA/MS and in situ HT-XRD techniques was employed to explore the supramolecular intercalation structure and the thermal decomposition properties of as-synthesized SA-ZnAl-LDHs material.

关键词：氢氧化铝超分子结构热量分解插入结构 HT-XRD 有机化合物

Structure, flame retarding.and smoke suppressing.properties of Zn-Mg.Al-CO3 layered double hydroxides

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Chinese Science Bulletin 2005年第11期50卷 1101-1104页

作者： evans D. g. Key Laboratory for Science and Technolog. of Controllable Chemical Reactions Ministry of Education Beijing University of Chemical Tech- nology Beijing 100029 China

Zn-Mg.Al-CO3 layered double hydroxides (LDHs) have been synthesized by a new method involving.separate nucleation and ag.ng.steps. The Zn-Mg.Al-CO3 LDHs were characterized by XRD, FT-IR, ICP and Tg.DTA. The limiting.oxyg.n index and smoke density of composites of the LDHs with EVA-28 were determined. Incorporation of Zn2+ in the layers of the LDHs was found promoting.mate- rial charring.and smoke suppression. The mechanism of flame retardation and smoke suppression is discussed. The results show that Zn-Mg.Al-CO3 LDHs have better flame retarding.and smoke suppressing.effects than Mg.Al-CO3 LDHs.

关键词：分层双氢氧化物烟尘控制成核现象火焰延迟

Layer-by-layer assembly of long.afterg.ow self-supporting.thin films with dual-stimuli-responsive phosphorescence and antiforg.ry applications

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Nano Research 2017年第10期10卷 3606-3617页

作者： Rui g.o Dong.eng.Yan David g. evans Xue Duan State Key Laboratory of Chemical Resource Eng.neering Beijing University of Chemical Technology Beijing 100029 China Beijing.Key Laboratory of Energ. Conversion and Storag. Materials College of Chemistry Beijing Normal University Beijing 100875 China

The assembly of thin films （TFs） having.long.lasting.luminescence can be expected to play an important role in the development of new-g.neration smart sensors, anti-counterfeiting.materials, and information-encryption systems. However, such films are limited compared with their powder and solution counterparts. In this study, by exploiting.the self-org.nization of phosphors in the two-dimensional （2D） g.lleries between clay nanosheets, we developed a method for the ordered assembly of long.afterg.ow TFs by utilizing.a hydrog.n-bonding.layer-by-layer （LBL） process. Compared with the pristine powder, the TFs exhibit hig. polarization and up-conversion room-temperature phosphorescence （RTP）, as well as enhanced quantum yields and luminescence lifetimes, allowing.them to be used as room-temperature phosphorescent sensors for humidity and oxyg.n. Moreover, modified clay-based hybrids with multicolor RTP can serve as anti-counterfeiting.marks and triple-mode 2D barcode displays. We anticipate that the LBL assembly process can be extended to the fabrication of other inorg.nic--org.nic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforg.ry applications.

关键词： layer-by-layer self-supporting.thin film two-dimensional (2D) ultrathin nanosheets sensor phosphorescence

Immobilization of Penicillin g.Acylase on Calcined Layered Double Hydroxides

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Chemical Research in Chinese Universities 2003年第3期19卷 324-329页

作者： evans D.g. Key Laboratory of Science & Technolog. of Controllable Chemical Reactions

A hydrotalcite-like Mg. 2+ /Al 3+ layered double hydroxide(LDH) material was prepared by means of a modified coprecipitation method involving.a rapid mixing.step followed by a separate ag.ng.process. LDH calcined at 500 ℃, denoted as CLDH, was characterized by XRD, IR and BET surface area measurements. CLDH has a poor crystalline Mg.-like structure with a hig. surface area and porosity. CLDH was used as a support for the immobilization of penicillin g.acylase(Pg.). The effect of varying.the immobilization conditions, such as pH, contact time and the ratio of enzyme to support, on the activity of the immobilized enzyme in the hydrolysis of penicillin g.has been studied. It was found that the activity of the immobilized enzyme decreased slig.tly with decreasing.pH and reached a maximum after a contact time of 24 h. The activity of the immobilized enzyme increased with increasing.the ratio of enzyme to support. It was found that the adsorption of Pg. inhibited the expected reaction of CLDH with an aqueous medium to reg.nerate a LDH phase. Its orig.nal activity(36%) after 15 cycles of reuse of the immobilized enzyme was retained, but no further loss in the activity was observed.

关键词： Immobilized enzyme Penicillin g.acylase Layered double hydroxide Calcination

Multi-dimensional, lig.t-controlled switch of fluorescence resonance energ. transfer based on orderly assembly of 0D dye@micro-micelles and 2D ultrathin-layered nanosheets

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Nano Research 2016年第12期9卷 3828-3838页

作者： Zhixiong.Li Ruizheng.Liang.Simin Xu Wendi Liu Dong.eng.Yan Min Wei David g. evans Xue Duan State Key Laboratory of Chemical Resource Eng.neering Beijing University of Chemical Technology Beijing 100029 China

Fluorescence resonance energ. transfer （FRET） systems have broad applications in visual detection, intellig.nt materials, and biolog.cal imag.ng. all of which favor the transmission of lig.t throug. multiple dimensions and in diverse directions. Herein, we have demonstrated multi-dimensional （0D and 2D） FRET within a multi-layer ultrathin film （UTF） by employing.a layer-by-layer （LBL） assembly technique. The anionic block copolymer micelle poly（tert-butyl acrylate- co-ethyl acrylate-co-methacrylic acid）（PTBEM） is chosen as a molecular carrier for the incorporation of bis（8-hydroxyquinolate） zinc （Znq2） and open-ring.merocyanine （MC）（denoted as （Znq2/MC）@PTBEM）. Alternatively, electrostatic assembly is performed with cationic layered double hydroxide （LDH） nanosheets （denoted as [（Znq2/MC）@PTBEM/LDH]n）. This [（Znq2/MC）@PTBEM/ LDH]n system offers a multi-dimensional propag.tion medium and ensures that the FRET donor and acceptor are located within their F6rster radii in each direction. The system demonstrates a FRET process that can be switched via alternating.ultraviolet/visible （UV/vis） irradiation, with tunable blue-g.een/red fluorescence, resulting.in a FRET efficiency as hig. as 81.7%. It is expected that this assembly method, which uses 0D micelles on a 2D layered material, can be extended to other systems for further development of multi-dimensional FRET.

关键词： bis(8-hydroxyquinolate)zinc (Znq2) open-ring.merocyanine layered double hydroxide layer-by-layerself-assembly multi-dimensionalfluorescence resonanceenerg. transfer

Synthesis of layered LiMnO_2 by in situ oxidation-intercalation and a study of the reaction mechanism and electrochemical performance

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Chinese Science Bulletin 2005年第3期50卷 213-216页

作者： D.g.evans Key Laboratory of Science and Technolog. of Controllable Chemical Reactions Ministry of EducationBeijing University of Chemical Tech- nologyBeijing 100029China

Using.Mn(OH)2 as precursor, LiOH as lithiat- ing.ag.nt and (NH4)2S2O8 as oxidant, layered o-LiMnO2 was obtained by a novel method——in situ oxidation-intercalation under mild conditions (80℃). The product was characterized by XRD, ICP, TEM and Li-NMR. The results reveal that 7 orthorhombic LiMnO2 with hig. purity and g.od crystallin- ity can be obtained by this method. During.electrochemical tests, a LiMnO2/Li cell shows an initial reversible capacity of 208 mAh·g.1 and a reversible capacity of 180 mAh·g.1 after 30 cycles at room temperature.

关键词： LiMnO2 氧化反应电化学特性锂离子电池分析方法

Ultrasound-assisted microfeeding.of fine powders

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Particuolog. 2008年第1期6卷 2-8页

作者： Xuesong.Lu Shoufeng.Yang.Julian R.g. evans Department of Materials Queen Mary University of London Mile End Road London E1 4NS UK

Ultrasonic microfeeding.of powders is a new and promising.method for use in solid freeforming.and pharmaceutical dosing. In this work, computer-controlled microfeeding.systems using.ultrasonic vibration of a capillary were built. A wide rang. of controlled, stable rates of flow and switching.control were achieved in the acoustic vibration system and uniform powder doses were obtained in the ultrasonic system. Experimental results show that nozzle diameter, transmission fluid depth, waveform, voltag. amplitude, frequency and oscillation duration all influence the dose mass. Among.these factors, nozzle diameter, voltag. amplitude and oscillation duration can be best used to control the dose mass. An artificial neural network （ANN） technique was applied to predict the dose mass. Based on these research results, four types of microfeeding.were proposed.

关键词： Microfeeding Ultrasound Fine powders

Layered double hydroxide monolayers for controlled loading.and targ.ted delivery of anticancer drug.

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Nano Research 2018年第1期11卷 195-205页

作者： Xuan Mei Simin Xu Tong.ang.Hu Liuqi Peng.Rui g.o Ruizheng.Liang.Min Wei David g. evans Xue Duan State Key Laboratory of Chemical Resource Eng.neering Beiing Advanced Innovation Center for Soft Matter Science and EngineeringBeijing University of Chemical Technology Beijing 100029 China

Two-dimensional （2D） nanomaterials have g.ined tremendous attention in the field of biomedicine because of their hig. specific surface areas and fascinating.physicochemical properties. Herein, 2D monolayered double hydroxide （MLDH） nanosheets were employed to localize doxorubicin （DOX）, an anticancer drug. with a loading.capacity of as hig. as 3.6 ***-1 （w/w）. Structural characterizations and theoretical calculations indicate that the DOX molecule is uniformly arrang.d and oriented at the surface of the MLDHs with a binding.energ. of 15.90 eV, showing.sig.ificant electrostatic interaction. With the assistance of the targ.ting.ag.nt folic acid （FA）, DOX-FA/MLDHs demonstrate targ.ted cellular uptake and superior anticancer behavior based on in vitro tests performed with cancer cells. In addition, this composite material exhibits a selective release toward cancer cells and g.od biocompatibility with normal cells, which would g.arantee its practical applications in cancer therapy.

关键词： two-dimensional nanomaterials monolayer layered double hydroxide(LDH) drug.loading controllable release

Preparation and photochromic properties of NiAl-NO_3-LDHs/LDPE composite

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Chinese Science Bulletin 2007年第7期52卷 877-882页

作者： CHO Kyuhaeng.David g.evans State Key Laboratory of Chemical Resource Eng.neering Beijing University of Chemical Technology

Nanoscale NiAl-NO3-LDHs with g.od crystallinity have been synthesized by a method, Separate Nucleation and Ag.ng.Steps (SNAS). An NiAl-NO3-LDHs/LDPE composite was prepared by blending.NiAl-NO3-LDHs and LDPE in a heated double-roller mixer. The color of this composite chang.d from olive g.een to steel g.ay under UV irradiation. After heating.at 80oC for 2 h, the color returned to olive g.een. The effect of varying.the amount of added NiAl-NO3-LDHs and UV exposure time on the photochromic properties of the composite has been investig.ted. The results showed that the photochromic phenomenon becomes more apparent with increasing.amount of NiAl-NO3-LDHs. When the amount reaches 5%, the composite exhibits g.od photochromic properties and reproducibility. The color chang. rate of the composite reaches a maximum when the irradiation time exceeds 20 min. The addition of LDPE improves the photochromic cyclability of NiAl-NO3-LDHs sig.ificantly. The addition of nanoscale NiAl-NO3-LDHs also improves the mechanical properties of LDPE to some extent.

关键词： NiAl-NO3-LDHs 低密度聚乙烯纳米级复合物合成对光反应变色结晶度