片状纳米氧化锌单晶的制备和表征

本文提供了一种应用二步法制备片状纳米氧化锌单晶的实验方法--首先,以尿素为沉淀剂宿主,以氯化锌、碱式碳酸锌为原料,应用均匀沉淀法获得纳米氧化锌的片状纳米级前驱物;然后通过控温热分解前驱物制备出片状纳米氧化锌单晶.用扫描电镜观测了制备的ZnO单晶的形貌,并通过红外光谱对其进行了表征.结果表明:实验制备的氧化锌均为无色透明的片状单晶,结晶形貌为正六边形、五边形、矩形以及其它不规则形状,单晶直径在30～600μm之间,厚30～60nm;影响纳米氧化锌单晶制备的主要因素是反应物料配比、沉淀剂宿主尿素的浓度(1∶6)以及反应温度(70～85℃).此外,乙醇的含量对片状纳米前驱物的形貌影响很大,10;～40;的乙醇含量利于形成片状纳米氧化锌单晶.     

利用锌渣氧粉碱驱晶化法制备纳米氧化锌紫外吸收剂

以硫酸为浸出剂,提取锌渣氧粉中的锌,形成精制ZnSO4溶液为锌源,NaOH溶液为沉淀剂,采用低温开放溶液法制备出纳米氧化锌,研究锌碱摩尔比、反应温度、不同初始锌离子浓度对产品晶体结构和形貌的影响,确立控制条件:初始Zn2+浓度0.1 mol·L-1,锌碱摩尔比1:5,控制62℃条件下恒温搅拌反应1 h,制备出锥形的六方晶系纤锌矿结构纳米氧化锌,颗粒分布均匀,平均粒径为100 nm.ZnO的形成是以负离子四面体ZnO2-2为生长基元,由Zn(OH)2到ZnO"结晶-溶解-再结晶"过程.制备的氧化锌在紫外光区280～400 nm波段有很强的吸收性,在可见光区有较好的透过率,具有良好紫外光遮蔽性和可见光透过性,可作为紫外线吸收剂使用.     

聚乙烯醇对ZnO纳米棒结构和光学性能的影响

以六水硝酸锌为锌源,聚乙烯醇(PVA)为分散剂,制备了纳米氧化锌(ZnO).利用X射线衍射(XRD)和电子扫描电镜(SEM)对氧化锌的晶体结构、形貌和尺寸进行了表征.利用吸收光谱对氧化锌的吸收率进行了测量.结果表明,所制备的氧化锌属于六方纤锌矿单晶结构,呈棒状结构.通过改变PVA含量,氧化锌纳米棒的长度可以从400nm到2μm可调.吸收光谱表明,随着PVA含量增加,吸收光谱发生红移.讨论了PVA作用下氧化锌纳米棒的形成机理.     

改进的多元醇法制备高分散纳米氧化镁及其锶吸附性能研究

以六水合氯化镁(MgCl·6H2O)为原料,以尿素为沉淀剂,采用改进的多元醇法制备了颗粒均匀、分散性好的纳米氧化镁粒子,并分别研究了反应温度和反应时间对前驱体和MgO粉体结构和形貌的影响.研究表明,在110℃反应8h后制备的前驱体为30 nm左右纳米颗粒状碱式碳酸镁Mg5 (CO3)4(OH)2(H2O)4.在700℃焙烧3h后可得到粒径为50 nm左右分散性较好的MgO纳米粒子.该种纳米氧化镁粉体对水溶液中的锶具有较好的吸附作用,吸附量为5.3 mg/g.     

氨配合法控制合成片状纳米氧化锌

以次氧化锌为原料,采用氨配合法制备片状纳米氧化锌.制备过程包括氨浸、净化、脱氨、煅烧等工序.重点研究了添加剂用量、反应温度、空气流量、锌氨络合溶液浓度对片状纳米氧化锌前驱体形貌的影响,以及煅烧温度和煅烧时间对片状纳米氧化锌产品影响.利用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)对产品进行表征.结果表明:在添加剂的加入量为0.5;(质量分数)、反应温度为90 ℃、空气流量为7 L· min-1、锌氨络合溶液浓度为1.13 mol· L-1,煅烧温度为350 ℃,煅烧时间为6 h条件下,制备的产品为片状纳米氧化锌,片层厚度在10 nm左右,产品纯度达99.13;.     

水热合成法制备纳米氧化锌粉

采用水热法合成了氧化锌纳米棒,研究了不同合成条件对ZnO纳米晶的影响.采用碱式碳酸锌作为前驱体,水为水热介质,可获得氧化锌纳米棒,水热时间的延长和水热温度的提高都使氧化锌纳米棒的长径比减小,其紫外发射光和近红外发射强度增大.当在体系中加入聚乙二醇时,可获得片状氧化锌结晶.当以0.5 mol/L的碳酸钠水溶液为水热介质,可得到长径比超过20,直径为500 nm左右分散均匀的纳米氧化锌棒.以氢氧化锌为前驱体,也能得到氧化锌纳米棒,其长径比为15左右.     

一步法制备纳米氧化锌的形成机理

以氯化锌和氢氧化钠为原料,采用直接水解一步法制备了针状和球形纳米氧化锌.借助于XRD、TEM等测试手段,对纳米氧化锌粉体的制备条件和其对粒度、形貌的影响进行了分析研究.利用负离子配位多面体生长基元理论模型,解释了直接水解合成氧化锌纳米晶体的形成机理和生长习性.研究结果表明,一步法直接合成纳米氧化锌的结晶过程遵循溶解-结晶-聚集生长机理模型;ZnO为极性晶体,具有极性生长特性,其成核过程包括均相成核和非均相成核.     

燃烧法制备La_2O_3纳米晶的研究

以硝酸镧作为氧化剂,柠檬酸铵作为燃料,用少量尿素作引发剂,采用燃烧法制备了La_2O_3纳米晶.并研究了煅烧温度、原料计量比和释放气体等因素对样品的影响.室温固相反应法制得的粘稠膏状络合物LaCit,当加热至150 ℃时立即引起燃烧,得到灰色前驱物,前驱物经700 ℃煅烧2 h得到单晶纳米La_2O_3样品.利用XRD、TEM和SEM测试方法对样品表征,结果表明:样品形貌为透明矩形片状单晶,平均长度为100~150 nm,宽度为40~80 nm,厚度约为20 nm,产率为85;~87;,粒度分布均匀,具有良好的分散性.     

片状ZnO薄膜的制备及其在DSSC中的光电性能研究

采用均匀沉淀法在导电玻璃基体上制备ZnO前驱体薄膜,然后热分解前驱体制备出ZnO薄膜用作染料敏化太阳能电池(DSSC)的光阳极.使用XRD和SEM对ZnO薄膜的结构和形貌进行表征.讨论了n(尿素)/n(Zn2+)、Zn2+浓度、均匀沉淀反应温度、薄膜焙烧温度等工艺因素对ZnO在DSSC中的光电性能影响.结果表明,均匀沉淀法制备ZnO薄膜为六方纤锌矿结构,ZnO薄膜以片状在基体上生长.优化的ZnO薄膜组装的DSSC在100mW/cm2下的短路电流为5.39 mA/cm2,开路电压为O.516 V.     

乙醇/水混合溶剂热法制备不同形貌的CuO晶体

以Cu(NO3)2·3H2O为原料,加入NaOH或NaOH+Na2CO3水溶液沉淀剂,生成Cu(OH)2或Cu2(OH)2CO3沉淀作前驱物,采用乙醇/水混合溶剂热法制备CuO.用FT-IR、XRD、SEM等方法对产物进行了表征.研究了溶剂的组成、前驱物的种类等因素对产物形貌及生成速率的影响.实验结果显示:以Cu2(OH)2CO3作前驱物,溶剂组成为V(C2H5OH):V(H2O)=1:2、150 ℃处理12 h可得形状规整的片状CuO;而以Cu(OH)2作前驱物,在相同条件下处理所得产物形貌为纺锤形.     

First-principles coexistence simulations of supercooled liquid silicon

We perform first-principles coexistence simulations of the low-density and the high-density phases of supercooled liquid silicon and find a negative slope for the coexisting line in the temperature-pressure plane. Electron density maps and electron-localization function plots of the two phases of silicon show marked differences. The calculated differences suggest more localized electrons in the low-density liquid compared to the high-density liquid, coming from an increased population of covalent bonds, which further explain the calculated negative slope in the two phase coexistence regime. This is consistent with the presence of a pseudo-gap in low-density liquid silicon, absent in the high-density liquid which shows a metallic behavior.     

Triethyl ammonium salt of O,O′-bis(p-tolyl)dithiophosphate, [Et3NH]+[(4-MeC6H4O)2PS2]−

Triethyl ammonium Salt of O,O′-bis(p-tolyl)dithiophosphate and O,O′-bis(m-tolyl)dithiophosphate have been obtained by reaction of p- and m-cresol, respectively with P₂S₅ in toluene and have been characterized by elemental analysis, IR, ¹H and ³¹P NMR spectroscopy. The molecular structure of O,O′-bis(p-tolyl)dithiophosphate has been determined. Crystal data: [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻: Monoclinic, P2₁/c, a=15.2441(9) ?, b=10.415(2) ?, c=3.9726(9) ?, β=91.709(7)°, V=2217.5(1) ?⁻³, Z=4.Supplementary materials Additional material available from the Cambridge Crystallographic Data Centre (CCDC no. 600927 for [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻ comprises the final atomic coordinates for all atoms, thermal parameters, and a complete listing of bond distances and angles. Copies of this information may be obtained free of charge on application to The Director, 12 Union Road, Cambridge CB2 2EZ, UK (fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).     

Crystal structures of thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane

Structures of both thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane, ?C₆H₄?CH₂SCH₂?C₆H₁₀?CH₂SCH₂?, have been determined, wherecis andtrans refer to the attachments to the cyclohexane ring. Thecis form crystallizes in the monoclinic space groupP2₁/c witha=8.4299(11)Å,b=21.772(2)Å,c=8.9724(13)Å, β=116.574(11)^o, andZ=4. Thetrans isomer packs into the monoclinic space groupP2₁ witha=8.159(16)Å,b=10.185(5)Å,c=9.558(2)Å, β=112.435(18)^o, andZ=2. The cyclohexane ring of thecis isomer is in the chair conformation, while the cyclohexane of thetrans isomer is found in a twisted boat conformation.     

CTAB与SDBS对碳酸锶粒子生长形态调控及机理研究

以表面活性剂CTAB和SDBS为化学添加剂,采用化学共沉淀法对碳酸锶晶体的生长形态进行调控,成功地制备出了实心的树枝状和花瓣为空心的花状碳酸锶粉体,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析手段对样品进行了表征;最后重点对化学添加剂可能产生的影响机理进行了初步的探讨.结果表明,CTAB和SDBS在晶体生长的过程中能起到显著的影响作用,两者对粒子分散性能的作用效果相反,而且后者对晶体(013)和(213)晶面表面能降低的贡献明显大于前者.     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.     

Synthesis and Crystal Structure of 5-[2-(6-bromonaphthalenyloxymethyl)]-3-(4-morpholinomethyl)-1,3,4-oxadiazole-2(3<Emphasis Type="Italic">H</Emphasis>)-thione

Abstract  The title compound, C₁₈H₁₈BrN₃O₃S, a derivative of 1,3,4-oxadiazole, crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.8731(3), b = 8.9994(4), c = 15.7099(6) ?, α = 92.779(3)°, β = 130.575(3)°, γ = 107.868(4)°, Z = 2. The dihedral angle between the mean planes of the planar naphthyl and morpholine (chair) rings with the planar oxadiazol ring is 50.1(8) and 76.8(6)°, respectively. The planar naphthyl ring is twisted 52.2(5)° with the mean plane of the morpholine ring. A group of four intermolecular close contacts are observed between a bromine atom and hydrogen atoms from the closely packed naphthyl, morpholine and oxy–methyl groups in the unit cell. These molecular interactions in concert with an additional series of π–π stacking interactions that occur between the center of gravity of the two 6-membered rings of the naphthalene group influence the twist angles of each of these three groups. A MOPAC AM1 calculation of the conformation energy of the crystal structure [226.0128(9) kcal] compared to that of the minimum energy structure after geometry optimization [29.9744(1) kcal] reveals a significantly reduced value. The twist angles of the three groups above also change after the AM1 calculation giving support to the influence of both intermolecular C–H···Br short-range interactions and Cg π–π stacking interactions on these angles which therefore play a role in stabilizing crystal packing. Graphical Abstract  Crystal structure of 5-{[(6-bromonaphthalen-2-yl)oxy]methyl}-3-(morpholin-4-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione, C₁₈H₁₈BrN₃O₃S, is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of irisolidone from the flowers of Pueraia lobata

Irisolidone (5,7-dihydroxy-6,4′-dimethoxyisoflavone) was isolated from the flowers of Pueraia lobata and its crystal structure was examined by X-ray single crystal diffraction. The crystal structure of irisolidone is monoclinic, space group P2₁/c with a = 15.491(9) ?, b = 7.895(4) ?, c = 13.321(7) ?, β = 110.546(9)° and Z = 4. Hydrogen bonding and aromatic π–π stacking assemble the title compound into a three-dimensional networking structure.     

Synthesis of spinacine and spinacine derivatives: crystal and molecular structures of Nπ-hydroxymethyl spinacine and Nα-methyl spinaceamine

The natural amino acid L-Spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) has been synthesized following a new pathway which gives a chemically and optically pure product with an excellent yield. The crystal structures of a synthetic intermediate, N^π-hydroxymethyl-spinacine, and a spinacine derivative, N^α-methyl-spinaceamine, have been investigated through X-ray diffraction: Spi(πMeOH)·H₂O, monoclinicP2 _i,a=8.571(1),b=6.682(1),c=8.588(1) Å, and β=94.67(1)^o. Spm(αMe)·2HCl·H₂O, triclinicP l,a=7.492(4),b=10.799(3),c=7.040(2) Å, α=91.88(2), β=98.36(3) and γ=73.34(3)^o. Spi(πMeOH) crystallizes with a water molecule and displays a zwitterionic character. The carboxylate group is in equatorial position and forms a short electrostatic interaction of 2.618(2) Å between one of its oxygens and the protonated nitrogen of the tetrahydropyridine ring. The crystal packing is assured by strong O?H???O, O?H???N, N?H???N intermolecular hydrogen bonds and C?H???O close contacts. The biprotonated compounds Spm(αMe) crystallizes with two Cl^? anions and a water molecule. The positive charge on the imidazole ring is delocalized on the conjugated moiety N=C?N. The crystal is built up by clusters formed by two biprotonated Spm(αMe) molecules, four Cl^? anions and two water molecules linked together by hydrogen bonds.