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1.
以表面固定Cu2+的改性大尺寸SiO2大孔材料作为载体,考察了时间、pH和给酶量对漆酶固定化效果的影响,并对固定化漆酶的活性和稳定性进行了研究。结果表明:5 h时吸附达到平衡,pH为4.5、漆酶与载体比例为5 mg·g-1时固定化效果最好,酶活回收率可达到100.4%;固定化漆酶的最适pH和最适温度较游离漆酶的均有升高且范围变宽,固定化后,漆酶的pH稳定性和热稳定性都得到显著提高;固定化漆酶的K m值略高于游离漆酶的;固定化漆酶具有良好的操作稳定性,与底物反应反复操作10批次后剩余酶活为72.7%。  相似文献   

2.
CuTAPc-Fe3O4纳米复合粒子及其漆酶固定化研究   总被引:1,自引:0,他引:1  
黄俊  周菊英  肖海燕  龙胜亚  王军涛 《化学学报》2005,63(14):1343-1347
漆酶的固定化研究对基于漆酶催化的光纤生物传感器具有十分重要的意义. 制备了四氨基酞菁铜(CuTAPc)-Fe3O4纳米复合粒子, 并用红外(IR)、场发射扫描电镜(FEG-SEM)、X射线衍射(XRD)、能谱、粒径仪等对其进行了表征. 结果表明形成了以CuTAPc包覆在Fe3O4纳米粒子表面的纳米复合粒子, 粒子呈现不规则球形, 且分布均匀, 粒子平均粒径在50 nm左右. 用此纳米复合粒子通过戊二醛交联法固定了漆酶, 固定后的酶比游离酶具有更好的贮存稳定性及操作稳定性. 这为研制高性能的光纤生物传感器打下了较好的基础.  相似文献   

3.
用溶胶凝胶法合成了Y2-xSiO5∶Eux纳米发光材料,使用XRD、FTIR和TEM对其结构进行了表征。讨论了相结构、煅烧温度和Eu3+掺杂浓度对材料发光性能的影响及规律。结果显示煅烧温度在900 ℃以下,材料主要呈非晶相结构,900 ℃以上材料主要呈晶态结构;颗粒随煅烧温度升高而增大,在非晶态时颗粒大小在15~45 nm,在晶态时颗粒大小为60~80 nm。激发光谱和荧光发射光谱受材料晶相结构以及Eu3+掺杂浓度的影响,在晶态结构中Y2-xSiO5∶Eux纳米材料呈现更精细的激发和发射光谱。在激发光谱中,电荷转移态吸收(CST)随煅烧温度升高呈现兰移现象,晶态时CST同非晶态相比明显红移;在发射光谱中,非晶态时 5D07F2跃迁呈现强的发光峰,随材料制备温度升高而增强,在晶态时该发光峰强度减弱,在长波波段呈现两个新的发光尖峰,并随煅烧温度升高而增强; 5D07F1发射峰从非晶态转变为晶态后,光谱裂分为三重尖峰;而 5D07F0跃迁发光光谱受结构和颗粒大小影响较小。同时在60~80 nm的Y2-xSiO5∶Eux晶体中,发现材料 5D07F25D07F1跃迁发光强度,均受Eu3+掺杂浓度的影响,当掺杂浓度x=0.4时,材料发光强度最大。  相似文献   

4.
采用水热法制备了0D/2D复合Ti3C2Tx MXene,利用X射线衍射、动态光散射和荧光光谱表征了其结构与形貌,结果表明形成了量子点吸附于纳米片的Ti3C2Tx复合结构(QDT)。相比未引入量子点的Ti3C2Tx,由QDT组装得到的自支撑膜电极的电化学性能有了显著提高:在三电极体系中,扫速为5 mV·s-1时,比电容为338 F·g-1,当扫速达到2 000 mV·s-1,电容保持率达到46%;在两电极体系中,0.5 A·g-1时的比电容达到216 F·g-1,10 000次循环后电容保持率为87%。以上性能可归结于:量子点提供了更多的离子吸附位点,且纳米片尺寸减小,缩短了离子传输路径。  相似文献   

5.
采用沉淀法和浸渍法制备了2种铬基(Cr2O3和CrO3/Cr2O3)催化剂,用于气相氟化2-氯-1,1,1-三氟乙烷合成1,1,1,2-四氟乙烷。研究发现含有低价铬(Cr3+)物种的Cr2O3催化剂上2-氯-1,1,1-三氟乙烷的稳态转化率为18.5%,而含有高价铬(Cr6+)物种和低价铬(Cr3+)物种的CrO3/Cr2O3催化剂初始转化率达到30.6%,然而存在明显的失活。含有Cr6+物种的CrO3/Cr2O3催化剂的2-氯-1,1,1-三氟乙烷氟化反应初始TOF值为1.71×10-4 molHCFC-133a·molCr(Ⅵ)-1·s-1,高于含有Cr3+物种的Cr2O3催化剂(4.16×10-5 molHCFC-133a·molCr(Ⅲ)-1·s-1)。Cr2O3催化剂在氟化反应前后催化剂的物相结构保持不变;而含有高价铬物种的CrO3/Cr2O3催化剂经HF反应后生成了CrOxFy活性物种。然而,CrOxFy物种在反应中挥发或转化成稳定但无活性的CrF3,从而导致催化剂失活。  相似文献   

6.
采用沉淀法和浸渍法制备了2种铬基(Cr2O3和CrO3/Cr2O3)催化剂,用于气相氟化2-氯-1,1,1-三氟乙烷合成1,1,1,2-四氟乙烷。研究发现含有低价铬(Cr3+)物种的Cr2O3催化剂上2-氯-1,1,1-三氟乙烷的稳态转化率为18.5%,而含有高价铬(Cr6+)物种和低价铬(Cr3+)物种的CrO3/Cr2O3催化剂初始转化率达到30.6%,然而存在明显的失活。含有Cr6+物种的CrO3/Cr2O3催化剂的2-氯-1,1,1-三氟乙烷氟化反应初始TOF值为1.71×10-4 molHCFC-133a·molCr(Ⅵ)-1·s-1,高于含有Cr3+物种的Cr2O3催化剂(4.16×10-5 molHCFC-133a·molCr(Ⅲ)-1·s-1)。Cr2O3催化剂在氟化反应前后催化剂的物相结构保持不变;而含有高价铬物种的CrO3/Cr2O3催化剂经HF反应后生成了CrOxFy活性物种。然而,CrOxFy物种在反应中挥发或转化成稳定但无活性的CrF3,从而导致催化剂失活。  相似文献   

7.
合成了大环三胺配体-1,4,7-三氮杂环癸烷([10]aneN3),并对文献方法进行了改进,简化了步骤,节省了溶剂。在25±0.1 ℃,离子强度I=0.10 mol·L-1 (KNO3)条件下,采用pH电位滴定法,测定了配体的质子化常数以及与Cu(Ⅱ)离子的配位平衡常数,讨论了配体与金属离子的配位情况。通过分光光度法,在pH值7~9范围内(2×10-4 mol·L-1 tris做为缓冲溶液),研究了配合物催化对-硝基苯酚乙酸酯(NA)水解动力学行为,得到了NA酯的水解速率常数kcat。结果表明催化水解速率对底物(NA)及配合物浓度均呈一级反应,水解反应遵循速率方程v=(kcatcCu2++kOH-cOH-+…)cNA;在中性和弱碱性条件下能很好的催化NA的水解,pH=9.19时,催化速率常数达到了4.405×10-2 mol-1·L·s-1,优于国际上同类研究报道的结果;催化反应受酸碱平衡控制。结合滴定结果,提出了催化反应机理。  相似文献   

8.
Cd2Ge7O16中Tb的长余辉发光特性   总被引:3,自引:0,他引:3  
本文研究了Cd2Ge7O16∶Tb3+材料的发光及其长余辉性质。指出Tb3+的发光是该离子的 5D3- 7DJ5D4- 7DJ两种跃迁产生的;随着掺杂浓度的增加 5D4- 7DJ跃迁增强,发光颜色由蓝变绿。并把该材料的长余辉性质归结为基质结构中有电子陷阱和空穴陷阱。提出余辉机理模型。  相似文献   

9.
采用高温固相法在空气中合成了Ba1.97-yZn1-xMgxSi2O7:0.03Eu,yCe3+系列荧光粉。分别采用X-射线衍射和荧光光谱对所合成荧光粉的物相和发光性质进行了表征。在紫外光330~360 nm激发下,固溶体荧光粉Ba1.97-yZn1-xMgxSi2O7:0.03Eu的发射光谱在350~725 nm范围内呈现多谱峰发射,360和500 nm处有强的宽带发射属于Eu2+离子的4f65d1-4f7跃迁,590~725 nm红光区窄带谱源于Eu3+5D0-7FJ (J=1,2,3,4)跃迁,这表明,在空气气氛中,部分Eu3+在Ba1.97-yZn1-xMgxSi2O7基质中被还原成了Eu2+;当x=0.1时,荧光粉Ba1.97Zn0.9Mg0.1Si2O7:0.03Eu的绿色发光最强,表明Eu3+被还原成Eu2+离子的程度最大。当共掺入Ce3+离子后,形成Ba1.97-yZn0.9Mg0.1Si2O7:0.03Eu,yCe3+荧光粉体系,其发光随着Ce3+离子浓度的增大由蓝绿区经白光区到达橙红区;发现名义组成为Ba1.96Zn0.9Mg0.1Si2O7:0.01Ce3+,0.03Eu的荧光粉的色坐标为(0.323,0.311),接近理想白光,是一种有潜在应用价值的白光荧光粉。讨论了稀土离子在Ba2Zn0.9Mg0.1Si2O7基质中的能量传递与发光机理。  相似文献   

10.
采用硅酸盐作为基质材料,通过高温固相法合成了Li4SrCa(SiO42:Eu3+红色荧光粉。通过X射线粉末衍射、X射线光电子能谱、透射电镜和荧光光谱,对所得样品的物相、形貌及其发光性能进行了表征分析。结果表明,掺入Eu3+后,Li4SrCa(SiO42的晶体结构并没有发生改变。在393 nm光激发下,荧光粉的荧光光谱中693 nm处发射峰强度最强。以693 nm作为监测波长,荧光激发峰分别为361 nm(7F05D4)、375 nm(7F05G3)、413 nm(7F05D3)、393 nm(7F05L6)和464 nm(7F05D2),即样品对近紫外和蓝光有较好的吸收。利用发射光谱研究了Eu3+掺杂浓度(物质的量分数)对荧光粉发光强度的影响。当Eu3+的掺杂浓度x=0.10时,样品发射强度最强,发射红光,其色坐标为(0.637 5,0.353 7)。通过Dexter强度与浓度关系分析了浓度猝灭机制。  相似文献   

11.
娄太平  张乐  郭军兴 《化学学报》2010,68(6):466-470
研究了在不同温度下的NaNO3和AgNO3水溶液中Li1.3Ti1.7Al0.3(PO4)3和Na1.3Ti1.7Al0.3(PO4)3离子交换行为.实验表明Li1.3Ti1.7Al0.3(PO4)3和Na1.3Ti1.7Al0.3(PO4)3均显示出了高选择性与Na+和Ag+进行离子交换的特征,且对Ag+的选择性高于Na+.升高温度可显著提高Ag/Li和Ag/Na的交换反应速度.  相似文献   

12.
Single crystals of K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K3RESi2O7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K3LuSi2O7, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K3LuSi2O7 crystallizes in space group P63/mmc with a=5.71160(10) Å and c=13.8883(6) Å. The structures containing the remaining rare earths crystallize in the space group P63/mcm with the lattice parameters of a=9.9359(2) Å, c=14.4295(4) Å, (K3GdSi2O7); a=9.88730(10) Å, c=14.3856(3) Å, (K3TbSi2O7); a=9.8673(2) Å, c=14.3572(4) Å, (K3DySi2O7); a=9.8408(3) Å, c=14.3206(6) Å, (K3HoSi2O7); a=9.82120(10) Å, c=14.2986(2) Å, (K3ErSi2O7); a=9.80200(10) Å, c=14.2863(4) Å, (K3TmSi2O7); a=9.78190(10) Å, c=14.2401(3) Å, (K3YbSi2O7). The optical properties of the silicates were investigated and K3TbSi2O7 was found to fluoresce in the visible.  相似文献   

13.
The near infrared spectra of aqueous solutions of the ethylsulfates of La, Nd, Gd, Tb, Er, Yb, Lu, Y, and Na have been determined from about 0.2 mol-dm–3 to nearly saturation. The extinction coefficients of water have been calculated taking into account the absorption of ethylslfate anions determined in separate experiments. Their values appeared to be nearly the same as that of pure water. The relative contents of free OH groups in 0.5 and 0.7M solutions have been estimated from the absorbances at 1160 nm. They were lower in solutions of the heavy rare-earth ethylsulfates (Tb, Er, Yb, Lu) than in equimolar solutions of the lighter ones (La, Nd), confirming our previous view that secondary hydration of the heavy trivalent rare-earth cations is distinctly stronger than that of the lighter ones. A comparison of the spectra of these aqueous ethylsulfates with those of perchlorates shows that the structure-breaking ability of the C2H5SO 4 ion is much smaller than that of perchlorate anion.  相似文献   

14.
The crystal structures of compounds with nominal compositions Bi6FeP2O15+x (I), Bi6NiP2O15+x (II) and Bi6ZnP2O15+x (III) were determined from single-crystal X-ray diffraction data. They are monoclinic, space group I2, Z=2. The lattice parameters for (I) are a=11.2644(7), b=5.4380(3), c=11.1440(5) Å, β=96.154(4)°; for (II) a=11.259(7), b=5.461(4), c=11.109(7) Å, β=96.65(1)°; for (III) a=19.7271(5), b=5.4376(2), c=16.9730(6) Å, β=131.932(1)°. Least squares refinements on F2 converged for (I) to R1=0.0554, wR2=0.1408; for (II) R1=0.0647, wR2=0.1697; for (III) R1=0.0385, wR2=0.1023. The crystals are complexly twinned by 2-fold rotation about , by inversion and by mirror reflection. The structures consist of edge-sharing articulations of OBi4 tetrahedra forming layers in the a-c plane that then continue by edge-sharing parallel to the b-axis. The three-dimensional networks are bridged by Fe and Ni octahedra in (I) and (II) and by Zn trigonal bipyramids in (III) as well as by oxygen atoms of the PO4 moieties. Bi also randomly occupies the octahedral sites. Oxygen vacancies exist in the structures of the three compounds due to required charge balances and they occur in the octahedral coordination polyhedron of the transition metal. In compound (III), no positional disorder in atomic sites is present. The Bi-O coordination polyhedra are trigonal prisms with one, two or three faces capped. Magnetic susceptibility data for compound (I) were obtained between 4.2 and 350 K. Between 4.2 and 250 K it is paramagnetic, μeff=6.1 μB; a magnetic transition occurs above 250 K.  相似文献   

15.
The room temperature structures of the five layer Aurivillius phases A2Bi4Ti5O18 (A=Ca, Sr, Ba and Pb) have been refined from powder neutron diffraction data using the Rietveld method. The structures consist of [Bi2O2]2+ layers interleaved with perovskite-like [A2Bi2Ti5O16]2− blocks. The structures were refined in the orthorhombic space group B2eb (SG. No. 41), Z=4, and the unit cell parameters of the oxides are a=5.4251(2), b=5.4034(1), c=48.486(1); a=5.4650(2), b=5.4625(3), c=48.852(1); a=5.4988(3), b=5.4980(4), c=50.352(1); a=5.4701(2), b=5.4577(2), c=49.643(1) for A=Ca, Sr, Ba and Pb, respectively. The structural features of the compounds were found similar to n=2-4 layers bismuth oxides. The strain caused by mismatch of cell parameter requirements for the [Bi2O2]2+ layers and perovskite-like [A2Bi2Ti5O16]2− blocks were relieved by tilting of the TiO6 octahedra. Variable temperature synchrotron X-ray studies for Ca and Pb compounds showed that the orthorhombic structure persisted up to 675 and 475 K, respectively. Raman spectra of the compounds are also presented.  相似文献   

16.
针对银精矿样品复杂,难消解的特点,研究了不同酸溶法和碱熔法对样品的消解情况,建立了硝酸,盐酸,氢氟酸,高氯酸消解银精矿的方法。根据元素灵敏度和抗干扰性,选定各元素的测定波长。通过酸溶样和碱熔样测定结果比对,验证了方法准确性。建立了四酸消解-电感耦合等离子体光谱法测定银精矿中铜、铅、锌、砷、镉、钙、镁、锰含量的方法,元素的线性相关系数均在0.9999以上。通过共存元素干扰实验,确定了银精矿中高含量元素(铜、铅、锌、铁、锑、铋等)对测定元素结果没有影响。方法检出限:Cu 0.0063 mg/L, Pb 0.0159 mg/L ,Zn 0.0090 mg/L,As 0.0192 mg/L, Cd 0.0093 mg/L ,Ca 0.0084 mg/L, Mg 0.0075 mg/L, Mn 0.0081 mg/L。测定下限:Cu 0.0105mg/L,Pb 0.0265 mg/L, Zn 0.0150 mg/L, As 0.0320 mg/L, Cd 0.0155 mg/L, Ca 0.0140 mg/L, Mg 0.0125 mg/L,Mn 0.0135 mg/L。3个样品的相对标准偏差在0.87%~3.56%之间,加标回收率在95.00%~103.56%之间。方法流程短,操作简单,快速,灵敏度和再现性高,结果准确可靠,可以满足银精矿中铜、铅、锌、砷、镉、钙、镁、锰含量的测定。  相似文献   

17.
Tao Lin  Wei Li  Maochu Gong  Yao Yu  Bo Du  Yaoqiang Chen   《Acta Physico》2007,23(12):1851-1856
TiO2,ZrO2-TiO2,andZrO2-TiO2-CeO2 were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature programmed desorption (NH3-TPD), oxygen storage capacity (OSC), and temperature programmed reduction (H2-TPR). The results showed that ZrO2-TiO2-CeO2 exhibited large number of surface strong acid, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V2O5 and 9% (w)WO3 for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O2, and the results of catalytic activity showed that the catalyst used ZrO2-TiO2-CeO2 as support yielded nearly 100% NO conversion at 275 °C at a gas hourly space velocity (GHSV) of 10000 h−1, and it had the best catalytic activity and showed great potential for practical application.  相似文献   

18.
The phase relations in the system In2O3–TiO2–MgO at 1100 and 1350°C are determined by a classical quenching method. In this system, there are four pseudobinary compounds, In2TiO5, MgTi2O5 (pseudobrookite type), MgTiO3 (ilmenite type), and Mg2TiO4 (spinel type) at 1100°C. At 1350°C, in addition to these compounds there exist a spinel-type solid solution Mg2−xIn2xTi1−xO4 (0≤x≤1) and a compound In6Ti6MgO22 with lattice constants a=5.9236(7) Å, b=3.3862(4) Å, c=6.3609(7) Å, β=108.15(1)°, and q=0.369, which is isostructural with the monoclinic In3Ti2FeO10 in the system In2O3–TiO2–MgO. The relation between the lattice constants of the spinel phase and the composition nearly satisfies Vegard's law. In6Ti6MgO22 extends a solid solution range to In20Ti17Mg3O67 with lattice constants of a=5.9230(5) Å, b=3.3823(3) Å, c=6.3698(6) Å, β=108.10(5)°, and q=0.360. The distributions of constituent cations in the solid solutions are discussed in terms of their ionic radius and site preference effect.  相似文献   

19.
通过调节B2O3-Bi2O3-ZnO-Al2O3(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO3)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明:添加适量的BBZA玻璃能够有效地将BaTiO3陶瓷烧结温度由1 350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO3的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO3陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO3晶粒表面。优化的BaTiO3陶瓷制备条件如下:BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO3陶瓷介电常数达到1 364,介电损耗低至1.2%。  相似文献   

20.
Microstructures of three Bi-W-Nb-O phases have been examined by using high-resolution transmission electron microscopy. Bi17W2Nb3O39 and Bi17WNb3O36 have incommensurate superstructures derived from the defect fluorite-type δ-Bi2O3 and can be regarded as intermediate phases between the type II solid solutions in the Bi-Nb-O and Bi-W-O systems. Bi8W2Nb2O23 has a Bi2WO6-like subunit cell with a stepped superstructure. Formation mechanisms of various superstructures are discussed.  相似文献   

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