An in-situ AFM investigation of canavalin crystallization kinetics
An in-situ AFM investigation of canavalin crystallization kinetics
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DOI：
10.1016/s0039-6028(97)00187-8
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发表时间：
1997-07-20
期刊：
影响因子：
1.9
通讯作者：
Lee, JD
中科院分区：
文献类型：
--
作者：
Land, TA;DeYoreo, JJ;Lee, JD
我们提出的结果，在原位原子力显微镜调查刀豆球蛋白晶体生长的动力学。结果表明，取决于过饱和度，生长发生在一个生长单元的高度产生的简单和复杂的螺位错源，2D形核岛，或宏观团簇沉积到表面上，然后横向传播的步骤束的步骤。刀豆球蛋白在三种不同pH（pH = 7.0、7.7和8.0）下的步进速度随浓度线性变化，并给出强烈依赖于pH的动力学系数β，在pH 7.3时β约为2.6 × 10（-3）cm·s（-1），在pH 8.0时β约为5.8 × 10（-4）cm·s（-1）。单个步骤的速度与由macroclusters创建的步骤束的速度，以及发生的2D成核宽梯田，限制扩散的长度尺度为I毫米的顺序。一个简单的扩散分析表明，表面扩散，而不是体扩散是控制机制iii溶质运输的步骤。给出了阶跃均匀化对阶跃衰减具有指数时间依赖性的证明，并与Schwoebel和Shipsey以及埃利希和Hudda [R.L.]的模型的预测定性一致。Schwoebel，E.J. Shipsey，J. Appl. Phys. 37（1966）3682：G.埃利希Hudda，J.Chem.Phys.li（1966）1039]：表明系统的行为与表面扩散控制生长与向上阶扩散偏置耦合的模型一致。利用Gilmer等[G. H.吉尔默河Ghez，N. Cabrera，J. Crystal Growth 8（1971）79].最好的拟合的数据是获得与表面扩散长度为0.4-0.9 μ m，并导致吸附到平台E-ad，并在步骤E-inc，分别为0.27和< 0.1 eV的结合的活化能值的估计。这种分析的结果相比，从NH 4 H2 PO 4（ADP），一种常见的无机晶体，其中的动力学系数是三个数量级更大的干涉测量所获得的。比较表明，这种差异的主要原因是与ADP相比，刀豆球蛋白对表面的吸附速率慢。(C)1997年Elsevier Science B.V.
We present the results of an in-situ atomic force microscopy investigation of the kinetics of canavalin crystal growth. The results show that, depending on the supersaturation, growth occurs on steps of one growth unit in height generated either by simple and complex screw dislocation sources, 2D nucleating islands, or macroclusters which sediment onto the surface before spreading laterally as step bunches. The step velocity of canavalin al three different pHs (pH = 7.0, 7.7 and 8.0 varies linearly with concentration and gives a kinetic coefficient beta which depends strongly on pH, with beta approximate to 2.6 x 10(-3) cm s(-1) at pH 7.3 to beta approximate to 5.8 x 10(-4) cm s(-1) at pH 8.0. Analysis of the velocity of single steps versus that of step bunches created by macroclusters, as well as the occurrence of 2D nucleation on broad terraces, constrains the length scale for diffusion to be of the order of I mm. A simple diffusion analysis is presented which indicates that surface diffusion rather than bulk diffusion is the controlling mechanism iii solute transport to the steps. A demonstration of step homogenization with an exponential time dependence fur step pair decay is presented, and is found to be in qualitative agreement with predictions of the models of Schwoebel and Shipsey and Ehrlich and Hudda [R.L. Schwoebel, E.J. Shipsey, J. Appl. Phys. 37 (1966) 3682: G. Ehrlich, F.G. Hudda, J. Chem. Phys. li (1966) 1039]: showing that the behavior of the system is consistent with a model of surface-diffusion controlled growth coupled with an up-step diffusion bias. The relationship between step speed and terrace width during step homogenization was investigated quantitatively using the model of Gilmer a al. [G.H. Gilmer, R. Ghez, N. Cabrera, J. Crystal Growth 8 (1971) 79]. The best fit to the data is obtained with a surface diffusion length of 0.4-0.9 mu m, and leads to estimates for values of the activation energy for adsorption to the terrace E-ad, and for incorporation at the step E-inc, of 0.27 and < 0.1 eV, respectively. The results of this analysis are compared to those obtained from interferometric measurements on NH4H2PO4 (ADP), a common inorganic crystal, for which the kinetic coefficient is three orders of magnitude larger. The comparison indicates that the main reason for this difference is the slow adsorption rate to the surface for canavalin as compared to ADP. (C) 1997 Elsevier Science B.V.