反相微乳液法制备钯纳米粒子的反应动力学。对粒度的影响
Reaction Kinetics in the Production of Pd Nanoparticles in Reverse Microemulsions. Effect on Particle Size
摘要：
在微乳液中合成金属纳米颗粒时，我们假设颗粒尺寸主要由反应速率控制。因此，观察到的粒径变化作为反应条件，如浓度、温度、所用表面活性剂的类型等，不应与这些条件的改变直接相关，而应与它们对反应速率产生的变化间接相关。通过时间分辨紫外-可见光谱，我们测量的反应速率中生产的钯纳米粒子在不同的反应物浓度的微乳液内，保持所有其他参数不变。然后将测量的反应速率与通过透射电子显微镜（TEM）测量的颗粒尺寸相关联。我们发现，纳米颗粒的尺寸线性增加的反应速率增加，独立的实际反应物浓度。我们提出的动力学控制主要是通过扩散的还原剂通过表面活性剂单层覆盖的微乳液膜。根据该模型，我们预测粒径应通过反应动力学间接取决于胶束半径（v0 ~ r^-3）、水体积（v0~ vw ^-3）和微乳液总体积（v0~vT^-3）以及温度（Arrhenius）。本文探讨了其中的一些预测。
英文摘要：
In the synthesis of metallic nanoparticles in microemulsions, we hypothesized that particle size is mainly controlled by the reaction rate. Thus, the changes observed on the particle sizes as reaction conditions, such as concentrations, temperature, type of surfactant used, etc., are varied should not be correlated directly to the modification of those conditions but indirectly to the changes they produce on the reaction rates. By means of time resolved UV-vis spectroscopy, we measured the reaction rates in the production of Pd nanoparticles inside microemulsions at different reactant concentrations, keeping all the other parameters constant. The measured reaction rates were then correlated with the particle sizes measured by transmission electron microscopy (TEM). We found that nanoparticle size increases linearly as the reaction rates increases, independently of the actual reactant concentrations. We proposed that the kinetics is controlled mainly by the diffusion of the reducing agent through the surfactant monolayer covering the microemulsion membrane. With this model, we predicted that particle size should depend indirectly, via the reaction kinetics, on the micelle radius (v0 ~ r^-3), the water volume (v0~vw^3) and the total microemulsion volume (v0~vT^-3), and temperature (Arrhenius). Some of these predictions were explored in this article.
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