DNA模板调控纳米无机材料生长

以DNA为模板诱导纳米无机晶体的生长是近年来一个新的研究方向.DNA模板具有完善和严密的分子识别功能,使其组装过程具有高度的选择性.通过人为控制DNA的形状、长度和序列,可以制备出不同结构的纳米功能材料.本文讨论了DNA模板诱导硫化镉、四氧化三铁、硫酸钡、氯化镁和二氧化硅等纳米无机晶体的生长.     

晶体中的各向异性研究

晶体在生长和使用过程中均表现出其独特的各向异性。本文针对一些典型的无机材料在结晶生长和机械性能方面的各向异性,构建了组成与性质之间的关联关系,确立了从材料的组成出发定量计算和预测其物理化学性质的模型方法。结晶生长的化学键合理论揭示了材料的各向异性生长形态取决于微观层次上不同结晶方向的表面键合结构,材料硬度的电负性模型揭示了组成原子的电负性和键合方式决定了材料硬度的各向异性。     

聚合物与表面活性剂混合模板调控碳酸钙结晶

以聚乙烯醇(PVA)和聚苯乙烯磺酸钠(PSSS)分别与十六烷基三甲基溴化铵(CTAB)组成混合模板,在CaCl2、Na2CO3体系中调控合成CaCO3晶体.考察了不同CTAB浓度及结晶温度对碳酸钙晶体的影响.通过扫描电子显微镜(SEM)、红外光谱(FT-IR)及X射线衍射(XRD)等技术对晶体的形貌和结构进行了表征,并对不同形貌碳酸钙的形成机理进行了探讨.结果表明:在PVA和CTAB模板中,5℃为方解石椭球状聚集体,25℃时为菊花状、立方状的方解石和球霰石的混晶,90℃时得到针状文石晶簇.以PSSS和CTAB模板调控下的碳酸钙,5℃时为球状的方解石和球霰石的混晶,25℃为颗粒均匀的球形球霰石,90℃时得到了花朵状文石.不同形貌及晶型碳酸钙的生成源自聚合物与CTAB组成复合物结构的差异.     

泡生法不同轴向蓝宝石的生长和光谱特性研究

应用自行研发的泡生法蓝宝石设备生长了a向及c向蓝宝石晶体,测量了它们的吸收光谱、摇摆曲线,采用KOH腐蚀并观察了两种不同生长方向的晶体缺陷,对两种不同生长方向晶体缺陷的差异进行了分析.结果表明采用a向籽晶生长的蓝宝石晶体透过率略优于c向籽晶生长的晶体,a向生长晶体晶格完整性高于c向生长晶体,c向生长的蓝宝石晶体位错密度明显高于a向生长的蓝宝石晶体.     

BiB3O6晶体最佳生长方向的确定

非线性光学晶体BiB3O6属单斜晶系,晶体的极性生长严重.采用不同方向的籽晶,晶体的形状、尺寸、质量和生长速度有着很大的差异.为了确定晶体的最佳生长方向,热膨胀性能被考虑.通过分析热膨胀椭球,[101]方向被确定为最佳籽晶方向.在适合的高温溶液条件和工艺参数下,沿着该方向,成功生长了尺寸为30mm×30mm×40mm、重120g的BiB3O6晶体.     

温度对气相传输法制备氧化锌晶体生长机制影响研究

为提高气相传输法制备微纳结构样品形貌的可控性,进行了生长温度调控下氧化锌晶体生长机制及其变化的实验研究.实验中的样品制备,以高纯度锌粉末为原料,在无模板、无催化条件下,通过加热蒸发-氧化冷却-生长晶体过程实现.其中,蒸发温度固定于750℃,反应区气体氛围保持稳定,生长区温度在450～ 600℃变化,制备出不同生长温度下样品.对所制备出诸样品,应用扫描电子显微镜、X-射线衍射仪和透射电子显微镜等方法,进行形貌与结构表征.基于表征结果,观察、分析、研究生长温度变化的影响,结合理论分析,得出了生长温度通过对生长过程中锌蒸汽过饱和度的影响,决定着不同生长机制,从而有着不同的形貌结构的样品.     

反应烧结碳材料表面异质外延生长SiO2晶体的研究

利用高温反应烧结在不同结构碳材料表面热蒸发进行二氧化硅(SiO2)晶体的外延生长.采用X-射线衍射仪(XRD)、扫描电镜(SEM)和电子能谱仪(EDS)分析和研究了碳材料表面生成物的物相组成与显微形貌,探讨了SiO2晶体的外延生长机理.研究结果表明,不同结构碳材料表面能外延生长SiO2晶体,但形态不同.在碳纤维表面形成颗粒和短晶须状SiO2晶体,在石墨片上形成凸起团聚状SiO2晶体,而在金刚石表面首先形成了Si-O涂层,然后在Si-O涂层上生长棒状SiO2体.碳材料外延生长SiO2晶体是首先通过热蒸发法使Si沉积到碳材料表面,然后Si与体系中的O反应形成SiO2晶核,在不同结构碳材料表面生长SiO2晶体.     

蓝宝石晶体的生长方向研究

本实验采用提拉法,在中频感应加热单晶炉内,进行了不同生长方向蓝宝石晶体的生长工作,分别取[11-20]和[0001]生长的晶体c面(0001)的晶片.通过应力仪、显微观测和X射线衍射等方式对晶片的位错密度等微观缺陷以及晶体结构进行了检测.实验表明:不同的生长方向生长得到的蓝宝石晶体的质量存在一定的差别,一般情况下,[11-20]方向生长的蓝宝石晶体质量优于[0001]方向生长的晶体.     

溶液中结晶生长的动力学模拟:化学键合方法

基于化学键合的角度对晶体生长过程的理解,提出了一个由动力学因素控制的形貌预测模型.该模型同时考虑了晶体内部结构和环境生长因素对晶体最终形貌的影响.对磷酸二氢钾 (KDP) 和磷酸二氢铵 (ADP) 晶体在不同动力学条件下的生长形貌进行了理论模拟,所预测的结果与实验观测结果基本一致.同时比较了相同过饱和度条件下KDP和ADP晶体的生长形貌,认为晶体局部成键性质不同是导致两者形貌差异的根本原因.本文通过对动力学因素控制的生长形貌的分析,为实际晶体生长过程中的形貌调控研究及应用提供理论依据.     

TiO2三维有序大孔材料的表面特性研究

本文采用聚苯乙烯胶体晶体模板,使用Sol-gel法制备的Ti02溶胶对胶晶模板进行填充,经高温热处理后获得TiO2三维有序大孔结构.采用扫描电子显微术(SEM),透射电子显微术(TEM),BET法,能量色散谱(EDS)以及红外光谱术(IR)对三维有序大孔结构进行了表征.研究表明改变热处理温度和聚苯乙烯球尺寸,可对三维有序大孔结构进行调控;同时本文重点研究了孔壁显微结构和化学组成等表面特性.     

Simultaneous synthesis of different structures of calcium oxalate by living bi‐template

Biomimetic living bi‐templates, mung bean sprouts (MBS), were employed to control the crystallization of calcium oxalate dehydrate (COD). Two kinds of crystals in different shapes were simultaneously grown on the outer surface and the inner stem wall of MBS respectively. The whole process is in the living system that material flow and energy exchange ceaselessly. The products were respectively characterized by SEM, XRD. A presumable mechanism is proposed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Inorganic and organic templates‐assisted solvothermal synthesis of trigonal selenium microrods

A facile and environment‐friendly solvothermal method has been developed for the controlled growth of nano‐ and micro‐structured trigonal selenium (t‐Se) by using green templates. And, the morphology of trigonal selenium can be tuned by using different kinds of templates. The as‐obtained products were characterized by X‐ray powder diffraction (XRD) and scanning electron microscope (SEM). Furthermore, the formation mechanism of trigonal selenium nano‐ and microcrystals was rationally suggested. This method will open a new avenue to synthesize other functional inorganic nano‐ and microcrystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

反应温度和添加剂含量对微波合成碳化硼微观形貌的影响

微波烧结由于具有高效、快速、绿色等特点越来越受到人们的关注.本文以天然煤粉(C)和硼酸(H3BO3)为原料,在无气氛保护条件下,利用2.45 GHz的TE666单频微波烧结炉,快速碳热还原反应法制备出纳米碳化硼(B4C)粉体.结果发现:当煤粉(C)和硼酸(H3BO3)质量比为3∶1,微波烧结温度为1400~1800 ℃,保温时间为5 min,即可制备出结晶良好的碳化硼(B4C)晶体,调整相关工艺参数可以控制B4C晶体的形貌,如直径为50~150 nm的球形颗粒或碳化硼片状结构,通过改变Na2CO3添加剂含量(3wt;~9wt;),可得到不同尺寸的碳化硼纳米片(边长为200~800 nm),获得传统电阻烧结条件下无法得到的碳化硼(B4C)晶体.     

海带硫酸多糖防止草酸钙结石形成的体外模拟

采用扫描电子显微镜、X射线衍射法和红外光谱在草酸钙(CaOxa)结石患者尿液中研究了从海带中提取的硫酸多糖(LSPS)的防石作用.结果表明,LSPS可以抑制一水草酸钙(COM)的成核和聚集,并诱导二水草酸钙(COD)晶体形成.随着ESPS浓度从0增加到0.005, 0.02和0.20 mg/ml,COD的百分含量从0分别增加到22;, 55;和100;.这些结果表明LSPS是抑制CaOxa结石形成的一种潜在药物.     

A study of primary nucleation of calcium oxalate monohydrate: II. Effect of urinary species

Kidney stones consist of various organic and inorganic compounds. Calcium oxalate monohydrate (COM) is the main inorganic constituent of kidney stones. However, the mechanisms for the formation of calcium oxalate kidney stones are not well understood. In this regard, there are several hypotheses including nucleation, crystal growth and/or aggregation of formed COM crystals. The effect of some urinary species such as oxalate, calcium, citrate, and protein on nucleation and crystallization characteristics of COM is determined by measuring the weight of formed crystals and their size distributions under different chemical conditions, which simulate the urinary environment. Statistical experimental designs are used to determine the interaction effects among various factors. The data clearly show that oxalate and calcium promote nucleation and crystallization of COM. This is attributed to formation of a thermodynamically stable calcium oxalate monohydrate resulting from supersaturation. Citrate, however, inhibits nucleation and further crystal growth. These results are explained on the basis of the high affinity of citrate to combine with calcium to form soluble calcium citrate complexes. Thus, citrate competes with oxalate ion for binding to calcium cations. These conditions decrease the amount of free calcium ions available to form calcium oxalate crystals. In case of protein (mucin), however, the results suggest that no significant effect could be measured of mucin on nucleation and crystal growth. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new template for the synthesis of porous inorganic oxide monoliths

A hydrophilic monolith, urea-formaldehyde (UF) resin, was for the first time proposed as a hard template for the synthesis of inorganic monoliths. Three kinds of inorganics, silica, zirconia and titania, were successfully prepared by using the new template. Scanning electron microscopy (SEM), nitrogen sorption measurements indicate that the inorganics are the replicas of their templates. Due to the characteristics of low cost, facile control of structure and ease of removal, the UF resin facilitates mass production of inorganic monoliths, which are attractive to industry. In addition, the hydrophilic characteristic of the UF resin makes it possible to use organic free precursors for preparing inorganic monoliths, which should be benign to the environment. The successful synthesis of the zirconia monolith using non-organic precursors confirms this.     

不同结构物质和有机基质对草酸钙晶体生长的促进作用

本文综述了有机大分子、小分子和有机基质对尿石矿物草酸钙(CaOxa)晶体成核、生长和聚集的促进作用.从促进物的分子结构和草酸钙晶体的晶面性质等方面讨论了不同类型促进物的作用机理.最后指出了该领域所面临的问题和将来的发展方向.     

不同晶相草酸钙晶体的选区电子衍射和X射线衍射比较分析

在卵磷脂-水脂质体中制备了一水草酸钙(COM)、二水草酸钙(COD)和三水草酸钙(COT).并对它们分别进行了透射电镜(TEM)、选区电子衍射分析(SAED)和X射线衍射(XRD)分析.TEM结果表明,COM、COD和COT均为泡状,粒径约80～150nm.将SAED结果与XRD结果对比分析,发现将SAED图谱指标化后所得的衍射数据与XRD的特征峰值基本相符,但在相对强度上存在差别.本实验结果表明,将TEM、SAED和XRD技术联合分析纳米级草酸钙晶体,不但可以观察纳米级草酸钙的形貌,而且能对其晶相、单晶和多晶等进行深入的了解.     

Structural and spectral studies on gypsum crystals under simulated conditions of phosphoric acid production with and without organic and inorganic additives

In the dihydrate process to produce phosphoric acid, phosphate ore [Ca₁₀F₂(PO₄)₆] is leached with sulfuric and weak phosphoric acids to produce phosphoric acid and gypsum as a by‐product. Crystallization of gypsum occurs as the leaching is taking place. The effect of organic and inorganic additives on the structure and spectrum of gypsum crystals under simulated conditions of phosphoric acid production is studied using x‐ray diffraction and infrared spectroscopy. Structure and spectrum of formed gypsum crystals in the absence of additives are slightly different from the standard gypsum crystals (card No. 6‐0046), which reflect the effect of preparation medium on the crystal structure of gypsum crystals. Presence of additives such as cetyl trimethyl ammonium bromide and 1,2‐dihydroxybenzene‐3,5‐disulfonic acid, Al³⁺ and Mg²⁺ increase the crystallinity of gypsum, while presence of additives such as citric acid and sodium dodecyl sulfate decrease the crystallinity of gypsum. Presence of Al³⁺ and Mg²⁺ as additives lead to the formation of calcium sulfate hemihydrate beside calcium sulfate dihydrate. Presence of sodium dodecyl sulfate as an additive inhibits the crystallization of gypsum and leads to the formation of anhydrite and calcium sulfate hemihydrate.