Grulke Eric A, Beck Matthew J, Yokel Robert A, Unrine Jason M, Graham Uschi M, Hancock Matthew L
Chemical & Materials Engineering, University of Kentucky.
Center for Computational Sciences, University of Kentucky.
Environ Sci Nano. 2019 May 1;6(5):1478-1492. doi: 10.1039/C9EN00222G. Epub 2019 Apr 4.
Nanoparticle dissolution in local milieu can affect their ecotoxicity and therapeutic applications. For example, carboxylic acid release from plant roots can solubilize nanoceria in the rhizosphere, affecting cerium uptake in plants. Nanoparticle dispersions were dialyzed against ten carboxylic acid solutions for up to 30 weeks; the membrane passed cerium-ligand complexes but not nanoceria. Dispersion and solution samples were analyzed for cerium by inductively coupled plasma mass spectrometry (ICP-MS). Particle size and shape distributions were measured by transmission electron microscopy (TEM). Nanoceria dissolved in all carboxylic acid solutions, leading to cascades of progressively smaller nanoparticles and producing soluble products. The dissolution rate was proportional to nanoparticle surface area. Values of the apparent dissolution rate coefficients varied with the ligand. Both nanoceria size and shape distributions were altered by the dissolution process. Density functional theory (DFT) estimates for some possible Ce(IV) products showed that their dissolution was thermodynamically favored. However, dissolution rate coefficients did not generally correlate with energy of formation values. The surface-controlled dissolution model provides a quantitative measure for nanoparticle dissolution rates: further studies of dissolution cascades should lead to improved understanding of mechanisms and processes at nanoparticle surfaces.
纳米颗粒在局部环境中的溶解会影响其生态毒性和治疗应用。例如，植物根系释放的羧酸可使根际中的纳米氧化铈溶解，影响植物对铈的吸收。将纳米颗粒分散液与十种羧酸溶液进行长达30周的透析；透析膜能透过铈-配体络合物，但不能透过纳米氧化铈。通过电感耦合等离子体质谱法（ICP-MS）分析分散液和溶液样品中的铈。通过透射电子显微镜（TEM）测量颗粒大小和形状分布。纳米氧化铈溶解于所有羧酸溶液中，导致纳米颗粒逐渐变小，并产生可溶性产物。溶解速率与纳米颗粒表面积成正比。表观溶解速率系数的值随配体而变化。纳米氧化铈的大小和形状分布均因溶解过程而改变。对一些可能的Ce(IV)产物的密度泛函理论（DFT）估计表明，它们的溶解在热力学上是有利的。然而，溶解速率系数通常与生成能值不相关。表面控制溶解模型为纳米颗粒溶解速率提供了一种定量度量：对溶解级联的进一步研究应有助于更好地理解纳米颗粒表面的机制和过程。
