Department of Chemistry, Middle East Technical University , 06800 Ankara, Turkey.
Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523, United States.
Langmuir. 2017 Jul 5;33(26):6550-6562. doi: 10.1021/acs.langmuir.7b01219. Epub 2017 Jun 22.
The question is addressed if dust is kinetically important in the nucleation and growth of Ir(0) nanoparticles formed from [BuN]Na(1,5-COD)Ir·PWNbO (hereafter [(COD)Ir·POM]), reduced by H in propylene carbonate solvent. Following a concise review of the (often-neglected) literature addressing dust in nucleation phenomena dating back to the late 1800s, the nucleation and growth kinetics of the [(COD)Ir·POM] precatalyst system are examined for the effects of 0.2 μm microfiltration of the solvent and precatalyst solution, of rinsing the glassware with that microfiltered solvent, of silanizing the glass reaction vessel, for the addition of <0.2 μm γ-AlO (inorganic) dust, for the addition of flame-made carbon-based (organic) dust, and as a function of the starting, microfiltered [(COD)Ir·POM] concentration. Efforts to detect dust and its removal by dynamic light scattering and by optical microscopy are also reported. The results yield a list of eight important conclusions, the four most noteworthy of which are (i) that the nucleation apparent rate "constant" k is shown to be slowed by a factor of ∼5 to ∼7.6, depending on the precise experiment and its conditions, just by the filtration of the precatalyst solution using a 0.20 μm filter and rinsing the glassware surface with 0.20 μm filtered propylene carbonate solvent; (ii) that simply employing a 0.20 μm filtration step narrows the size distribution of the resulting Ir(0) nanoparticles by a factor of 2.4 from ±19 to ±8%, a remarkable result; (iii) that the narrower size distribution can be accounted for by the slowed nucleation rate constant, k, and by the unchanged autocatalytic growth rate constant, k, that is, by the increased ratio of k/k that further separates nucleation from growth in time for filtered vs unfiltered solutions; and (iv) that five lines of evidence indicate that the filterable component of the solution, which has nucleation rate-enhancing and size-dispersion broadening effects, is dust.
问题是探讨在丙烯碳酸酯溶剂中，由[BuN]Na(1,5-COD)Ir·PWNbO（以下简称[(COD)Ir·POM]）还原形成的 Ir(0)纳米颗粒的成核和生长过程中，粉尘是否具有动力学重要性。在简要回顾了自 19 世纪后期以来有关粉尘在成核现象中（通常被忽视）的文献之后，研究了[(COD)Ir·POM]前催化剂体系的成核和生长动力学，考察了对溶剂和前催化剂溶液进行 0.2μm 微滤、用微滤溶剂冲洗玻璃器皿、硅烷化玻璃反应容器、添加<0.2μmγ-AlO（无机）粉尘、添加火焰制造的碳基（有机）粉尘以及起始时微滤[(COD)Ir·POM]浓度的影响。还报告了通过动态光散射和光学显微镜检测粉尘及其去除的努力。结果得出了八项重要结论，其中最值得注意的四项是：(i) 成核表观速率“常数”k 显示出，仅仅通过使用 0.20μm 过滤器过滤前催化剂溶液并用 0.20μm 过滤的丙烯碳酸酯溶剂冲洗玻璃器皿表面，就会使成核速率减慢 5 到 7.6 倍，具体取决于精确的实验及其条件；(ii) 仅仅采用 0.20μm 过滤步骤，就可以将所得 Ir(0)纳米颗粒的尺寸分布从±19 到±8%的范围缩小 2.4 倍，这是一个显著的结果；(iii) 更窄的尺寸分布可以归因于成核速率常数 k 的减慢，以及自催化生长速率常数 k 的不变，即过滤与未过滤溶液中 k/k 的增加比值进一步将成核与生长时间分离；(iv) 有五条证据表明，溶液中具有成核速率增强和尺寸分散展宽效应的可过滤成分是粉尘。
