ZnO纳米棒在Si衬底上外延生长研究

运用热蒸发ZnO粉末法,以金做催化剂,分别在Si(100)和Si(111)两种基片上外延生长了ZnO纳米棒(样品分别标为1#和2#).通过X射线衍射(XRD)和扫描电子显微镜(SEM)分析,结合ZnO与Si的晶格结构特征,从理论上得出了两个样品的晶格匹配关系.1#样品:[0001]ZnO∥[114]Si,[0001]ZnO∥[1-1-4]Si,[0001]ZnO∥[11-4]Si,[0001]ZnO∥[1-14]Si,失配度为1.54;;2#样品:[0001]ZnO∥[111]Si,[21-1-0]ZnO∥[11-0]Si,[1-21-0]ZnO∥[1-01]Si ,[1-1-20]ZnO∥[011-]Si,失配度为18.12;.研究表明Si衬底对ZnO纳米棒生长方向具有调控作用.     

Pyrene分子(小片石墨晶体)的电子传导特性

利用量子理论中基于Green函数的tight-binding方法,对pyrene分子的电子传导和电子流分布进行了理论研究。在考虑到界面耦合和Hopping积分的情况下,得出了电子透射谱和流分布的模拟结果。结果显示透射与电子的能量紧密相关;谱的振荡特征是能级量子化的结果;流分布有着特定的方向,并且在每一个原子点上符合Kirchhoff量子流守恒定律。另外还发现了桥接pyrene分子的正负能开关特性。     

香花石形态所反映的一种可能的孪晶结构

香花石是我国发现的第一个新矿物,它的形态非常复杂.本文基于香花石形态上出现了左形与右形相聚的现象,对香花石形态进行了重新思考,认为同一单形的左形与右形不能相聚形成单晶体,只能形成孪晶,因此,对原香花石晶体图进行了一些修正,认为原香花石晶体图可能是一个孪晶图.这对深入认识晶体形态及晶体对称理论、澄清长期以来人们并没有足够重视的一些基本概念有重要意义.     

Er3+:NaY(Wo.9Moo.1O4)2晶体的生长及光谱性能

采用提拉法(CZ法),生长出质量良好的Er3+:NaY(W0.9Mo0.1O4)2晶体.通过X射线粉末衍射,红外光谱分析,并与NaY(WO4)2相比较,得到Er3+:NaY(W0.9Mo0.1O4)2晶体的结构与NYW类似,仍为四方晶系的白钨矿结构,I4(1)/α空间群.测定了晶体的实际组成,得到晶体中各元素均按理论值进行掺杂,计算了掺杂离子的分凝系数约为1.15.在光谱性质上,测试了晶体的吸收光谱,及晶体在50～1000cm-1波数范围内的拉曼光谱,并计算了各吸收峰的半峰宽及吸收系数A.     

Sargassum fusiforme Polysaccharide-Based Hydrogel Microspheres Enhance Crystal Violet Dye Adsorption Properties

In this study, a polysaccharide-based hydrogel microsphere (SFP/SA) was prepared using S. fusiforme polysaccharide (SFP) and sodium alginate (SA). Fourier transform infrared spectroscopy (FT-IR) demonstrated that SFP was effectively loaded onto the hydrogel microsphere. Texture profile analysis (TPA) and differential scanning calorimetry (DSC) showed that, with the increase of SFP concentration, the hardness of SFP/SA decreased, while the springiness and cohesiveness of SFP/SA increased, and the thermal stability of SFP/SA improved. The equilibrium adsorption capacity of SFP/SA increased from 8.20 mg/g (without SFP) to 67.95 mg/g (SFP accounted 80%) without swelling, and from 35.05 mg/g (without SFP) to 81.98 mg/g (SFP accounted 80%) after 24 h swelling. The adsorption of crystal violet (CV) dye by SFP/SA followed pseudo-first order and pseudo-second order kinetics (both with R² > 0.99). The diffusion of intraparticle in CV dye was not the only influencing factor. Moreover, the adsorption of CV dye for SFP/SA (SFP accounted 60%) fit the Langmuir and Temkin isotherm models. SFP/SA exhibited good regenerative adsorption capacity. Its adsorption rate remained at > 97% at the 10th consecutive cycle while SFP accounted for 80%. The results showed that the addition of Sargassum fusiforme polysaccharide could increase the springiness, cohesiveness and thermal stability of the hydrogel microsphere, as well as improve the adsorption capacity of crystal violet dye.     

Structural and Functional Analysis of the Pyridoxal Phosphate Homeostasis Protein YggS from Fusobacterium nucleatum

Pyridoxal 5′-phosphate (PLP) is the active form of vitamin B6, but it is highly reactive and poisonous in its free form. YggS is a PLP-binding protein found in bacteria and humans that mediates PLP homeostasis by delivering PLP to target enzymes or by performing a protective function. Several biochemical and structural studies of YggS have been reported, but the mechanism by which YggS recognizes PLP has not been fully elucidated. Here, we report a functional and structural analysis of YggS from Fusobacterium nucleatum (FnYggS). The PLP molecule could bind to native FnYggS, but no PLP binding was observed for selenomethionine (SeMet)-derivatized FnYggS. The crystal structure of FnYggS showed a type III TIM barrel fold, exhibiting structural homology with several other PLP-dependent enzymes. Although FnYggS exhibited low (<35%) amino acid sequence similarity with previously studied YggS proteins, its overall structure and PLP-binding site were highly conserved. In the PLP-binding site of FnYggS, the sulfate ion was coordinated by the conserved residues Ser201, Gly218, and Thr219, which were positioned to provide the binding moiety for the phosphate group of PLP. The mutagenesis study showed that the conserved Ser201 residue in FnYggS was the key residue for PLP binding. These results will expand the knowledge of the molecular properties and function of the YggS family.     

立方氮化硼单晶紫外吸收光谱的研究

对于在高温、高压下合成的人工立方氮化硼(cBN)片状单晶进行了紫外吸收光谱和第一性原理的能带结构研究。实验中采用了UV WINLAB光谱分析仪,数据分析由MOLECULAR SPECTROSCOPY软件进行拟合运算,通过特殊的石英夹具对样品的测试表明cBN的紫外吸收波长限为198 nm,带隙为6.26 eV。结合第一性原理计算的cBN的能带结构和电子态密度的计算,可以证实导致紫外光吸收的过程是价带电子吸收光子到导带的间接跃迁。文章实验结果与目前报道的cBN能带结构中禁带宽度的吻合较好,表明cBN具有良好的紫外特性,是一种具有发展前景的紫外光电和高温半导体器件材料。     

矿化剂浓度和温度对水热法合成氧化锌晶体形态的影响

采用水热法，通过改变矿化剂浓度和温度合成了具有不同形态的氧化锌晶体。在较低的温度(350℃)，填充度为35％。矿化剂KOH浓度小于2mol／L时，只合成了氧化锌微晶。当矿化剂KOH浓度大于3mol/L时，合成出多种形态氧化锌晶体，大的晶体达到几十到几百微米，小晶体仅几微米。当矿化剂KOH浓度从4mol／L增加到5mol／L时，晶体的大小没有明显改变。在高矿化剂条件下合成的晶体显露完整的晶面结构，主要显露柱面m{1010}、锥面p{1011}、负极面O面{0001}，有时也显露Zn面{0001}。晶体表面出现斑坑，显示出晶体的表面缺陷。在430℃，填充度为35％，矿化剂KOH浓度大于1．5moL／L时。合成了多种形态氧化锌晶体，大晶体有几十到几百微米，小晶体仅几微米。当矿化剂KOH浓度为2mol／L，KBr浓度为lmol/L时，最大晶体的长度达到1mm。矿化剂KOH浓度为4mol/L时，晶体没有增大。粒度较大的氧化锌晶体形状多为六棱锥体，显露柱面m{1010}、锥面p{1011}、负极面O面{0001}。晶体表面光滑，完整性好。质量高于350℃时合成的晶体。     

Preparation of CdO nanoparticles by mechanochemical reaction

CdO nanoparticles of 43 nm in crystal size were successfully synthesized by the mechanochemical reaction (CdCl₂ + Na₂CO₃) with NaCl as a diluent and subsequent thermal treatment at 700°C for 2 h. The samples were characterized by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effect of calcination temperature on the crystal size of CdO nanoparticles was primarily investigated. The apparent activation energy of CdO nanoparticle formation during thermal treatment was calculated to be 12.2 kJ/mol.     

Crystal Structure and Excimer Fluorescence of Some Benzoylacetonatoboron Difluorides: Stacking Factor

The comparative study of the crystal structures of benzoylacetonato- (1), p-toluylacetonato- (2) and p-ethylbenzoylacetonatoboron (3) difluoride was carried out. Correlation of the luminescence properties of the complexes 1–3 and their crystal structures was revealed. The excimer formation in these compounds occurred the most efficiently for the complexes 1 characterized by the formation of stacks of molecules, unlike the complex 3, where individual dimers behaved as excimer-forming centers. The maximal fluorescence intensity was observed for the complex 2, which had the highest structural ordering.