Dissolution of ZnO Nanoparticles at Circumneutral pH: A Study of Size Effects in the Presence and Absence of Citric Acid
Dissolution of ZnO Nanoparticles at Circumneutral pH: A Study of Size Effects in the Presence and Absence of Citric Acid
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DOI：
10.1021/la203542x
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发表时间：
2012-01-10
期刊：
影响因子：
3.9
通讯作者：
Grassian, Vicki H.
中科院分区：
文献类型：
--
作者：
Mudunkotuwa, Imali A.;Rupasinghe, Thilini;Grassian, Vicki H.
了解工程纳米颗粒的尺寸依赖性过程，包括溶解，对于解决这些材料的潜在环境和健康影响及其长期稳定性至关重要。在这项研究中，实验测量的尺寸依赖性溶解的良好表征的氧化锌（ZnO）纳米粒子的粒径在4至130 nm的范围内已被测量在circumneutral pH值（pH值7.5）和比较。溶解被发现是增强与较小的ZnO纳米粒子相比，较大尺寸的颗粒，即使纳米粒子存在于溶液中的聚集体的流体动力学直径的顺序为1-3 μ m的大小。柠檬酸的存在下，显着提高了所有尺寸的ZnO溶解的程度，并观察到最大的增强为4 nm的颗粒。虽然这些结果被发现是在定性的理论预测，线性化形式的开尔文方程计算表面自由能产生的数量与文献中的预期值不一致。这种不一致的原因进行了讨论，包括潜在的偏差，从经典的热力学的溶解度行为作为一个结果缺乏详细的知识的表面结构和表面性质，包括不同的表面晶面的存在下，和聚集状态。
Understanding size-dependent processes, including dissolution, of engineered nanoparticles is essential in addressing the potential environmental and health impacts of these materials as well as their long-term stability. In this study, experimental measurements of size-dependent dissolution of well-characterized zinc oxide (ZnO) nanoparticles with particle diameters in the range of 4 to 130 nm have been measured at circumneutral pH (pH 7.5) and compared. Dissolution was found to be enhanced with smaller ZnO nanoparticles compared to larger-sized particles, even though the nanoparticles were present in solution as aggregates with hydrodynamic diameters on the order of 1-3 mu m in size. The presence of citric acid significantly enhanced the extent of ZnO dissolution for all sizes, and the greatest enhancement was observed for the 4 nm particles. Although these results are found to be in qualitative agreement with theoretical predictions, a linearized form of the Kelvin equation to calculate a surface free energy yielded quantities inconsistent with expected values from the literature. Reasons for this inconsistency are discussed and include potential deviations of solubility behavior from classical thermodynamics as a result of a lack of detailed knowledge of surface structure and surface properties, including the presence of different surface crystal facets, and the aggregation state.