Silica nanomaterials have been studied based on their potential applications in a variety of fields, including biomedicine and agriculture. A number of different molecules have been condensed onto silica nanoparticles’ surfaces to present the surface chemistry needed for a given application. Among those molecules, (3-aminopropyl)triethoxysilane (APS) is one of the most commonly applied silanes used for nanoparticle surface functionalization to achieve charge reversal as well as to enable cargo loading. However, the colloidal stability of APS-functionalized silica nanoparticles has not been thoroughly studied, which can be problematic when the high reactivity of amine groups is considered. In this study, four different types of silica nanoparticles with varied location of added APS have been prepared via a reverse micro emulsion process, and their colloidal stability and dissolution behavior have been investigated. Systematic characterization has been accomplished using transmission electron microscopy (TEM), silicomolybdic acid (SMA) spectrophotometric assay, nitrogen adsorption–desorption surface area measurement, and aerosol ion mobility-mass spectrometry to track the nanoparticles’ physical and chemical changes during dissolution. We find that when APS is on the interior of the silica nanoparticle, it facilitates dissolution, but when APS is condensed both on the interior and exterior, only the exterior siloxane bonds experience catalytic hydrolysis, and the interior dissolution is dramatically suppressed. The observation and analyses that silica nanoparticles show different hydrolysis behaviors dependent on the location of the functional group will be important in future design of silica nanoparticles for specific biomedical and agricultural applications.

中文翻译：

---

(3-氨基丙基)三乙氧基硅烷对反相微乳液合成二氧化硅纳米粒子溶解的影响

人们根据二氧化硅纳米材料在生物医学和农业等多个领域的潜在应用对其进行了研究。许多不同的分子已凝结在二氧化硅纳米粒子的表面上，以呈现给定应用所需的表面化学性质。在这些分子中，(3-氨基丙基)三乙氧基硅烷 (APS) 是最常用的硅烷之一，用于纳米颗粒表面功能化，以实现电荷反转并实现货物装载。然而，APS 功能化二氧化硅纳米粒子的胶体稳定性尚未得到彻底研究，当考虑到胺基的高反应性时，这可能会出现问题。在本研究中，通过以下方法制备了四种不同类型的二氧化硅纳米粒子，其添加的 APS 的位置不同反微乳液过程，并研究了它们的胶体稳定性和溶解行为。使用透射电子显微镜（TEM）、硅钼酸（SMA）分光光度测定、氮吸附-解吸表面积测量和气溶胶离子淌度-质谱法完成了系统表征，以跟踪纳米粒子在溶解过程中的物理和化学变化。我们发现，当APS位于二氧化硅纳米粒子的内部时，它有利于溶解，但是当APS在内部和外部都缩合时，只有外部硅氧烷键经历催化水解，并且内部溶解被显着抑制。