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The growth and characterization of L-arginine phosphate microcrystals in a silica sol gel matrix.

机译：L-精氨酸磷酸酯微晶在硅胶溶胶凝胶基质中的生长和表征。

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摘要

Silica sol-gel has proven to be a versatile material that can host a number of inorganic and organic dopant molecules, providing an environment in which they may retain their activity. This dissertation studies the relationship between crystallization and gelation in a system consisting of L-arginine phosphate (LAP), an organic non-linear optical crystal, in an inorganic silica sol-gel matrix.; The objectives of this research are to investigate the mechanisms of crystal nucleation and growth in a silica sol-gel matrix. Complex impedance measurements were used to determine the solubility of LAP in sol-gel as a function of temperature, the induction times for crystallization of LAP, and the overall rate of LAP precipitation. Analysis of the induction times was performed to determine the interfacial energies, surface entropy factors, and nucleation and growth mechanisms of LAP in sol-gel over a range of temperatures and concentrations.; Nucleation and growth of LAP in sol-gel was found to follow a model of primary nucleation followed by spiral growth (5°C to 20°C) or normal growth (25°C to 40°C) for LAP concentrations high enough that nucleation occurs in the sol. For lower LAP concentrations, heterogeneous nucleation occurs on sample interfaces or electrodes. The solubility of LAP in silica sol-gel was found to follow an Arrhenius relationship, with an enthalpy of solution of 0.68 eV. The enthalpy of solution for LAP in sol-gel is comparable to that in aqueous solutions, while the pre-exponential factor is about 8 times smaller in sol-gel than in water.; The interfacial energies of LAP in sol-gel are close to, but slightly larger than, those in aqueous solution. The interfacial energies decrease with increasing temperature at about the same rate in sol-gel as in aqueous solution.; Conductivity of LAP in sol-gel is primarily through proton conduction and follows an Arrhenius relationship with an activation energy for conduction of 0.26 eV and a pre-exponential factor that depends upon the square root of the LAP concentration.
机译：硅溶胶凝胶已被证明是一种通用材料，可以容纳许多无机和有机掺杂剂分子，从而提供了一种环境，使其可以保持其活性。本文研究了在无机二氧化硅溶胶-凝胶基质中有机非线性光学晶体L-精氨酸磷酸酯（LAP）组成的体系中结晶与胶凝的关系。这项研究的目的是研究硅溶胶-凝胶基质中晶体成核和生长的机理。使用复数阻抗测量来确定LAP在溶胶-凝胶中的溶解度与温度，LAP结晶的诱导时间以及LAP沉淀的总速率之间的关系。对诱导时间进行分析，以确定在一定温度和浓度范围内，溶胶-凝胶中LAP的界面能，表面熵因子以及成核和生长机理。发现LAP在溶胶-凝胶中的成核和生长遵循初生成核的模型，随后是螺旋生长（5°C至20°C）或正常生长（25°C至40°C），对于LAP浓度足以使其成核发生在溶胶中。对于较低的LAP浓度，异质成核发生在样品界面或电极上。发现LAP在二氧化硅溶胶-凝胶中的溶解度遵循Arrhenius关系，溶液的焓为0.68eV。溶胶-凝胶中LAP溶液的焓与水溶液相当，而溶胶-凝胶中的预指数因子约比水小8倍。 LAP在溶胶-凝胶中的界面能接近但略大于水溶液中的界面能。溶胶-凝胶的界面能随着温度的升高而降低，其溶胶-凝胶的速率与水溶液中的速率相同。溶胶-凝胶中LAP的电导率主要是通过质子传导，并遵循Arrhenius关系，具有0.26 eV的传导活化能和取决于LAP浓度平方根的预指数因子。

著录项

  • 作者

    Faltens, Tanya Anne.;

  • 作者单位

    University of California, Los Angeles.;

  • 授予单位 University of California, Los Angeles.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 161 p.
  • 总页数 161
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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