The pH at silica-water interfaces (pHint) was measured by grafting a dual emission fluorescent probe (SNARF) onto the surface of mesoporous silica nanoparticles (MSN). The values of pHint of SNARF-MSN suspended in water were different from the pH of the bulk solution (pHbulk). The addition of acid or base to aqueous suspensions of SNARF-MSN induced much larger changes in pHbulk than pHint, indicating that the interface has buffering capacity. Grafting additional organic functional groups onto the surface of SNARF-MSN controls the pHint of its buffering region. The responses of pHint to variations in pHbulk are consistent with the acid/base properties of the surface groups as determined by their pKa and are affected by electrostatic interactions between charged interfacial species as evidenced by the dependence of ζ-potential on pHbulk. Finally, as a proof of principle, we demonstrate that the hydrolysis rate of an acid-sensitive acetal can be controlled by adjusting pHint via suitable functionalization of the MSN surface. Our findings can lead to the development of nanoreactors that protect sensitive species from adverse conditions and tune their chemical reactivity.

中文翻译：

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通过表面官能化控制介孔二氧化硅纳米粒子的界面pH。

通过将双发射荧光探针（SNARF）接枝到介孔二氧化硅纳米颗粒（MSN）的表面上，测量二氧化硅-水界面的pH（pHint）。悬浮在水中的SNARF-MSN的pHint值不同于本体溶液（pHbulk）的pH。向SNARF-MSN的水悬浮液中添加酸或碱会导致pHbulk的变化比pHint大得多，这表明该界面具有缓冲能力。将额外的有机官能团接枝到SNARF-MSN的表面上可控制其缓冲区域的pHint。pHint对pHbulk变化的响应与表面基团的pKa确定的酸/碱特性一致，并且受带电界面物质之间静电相互作用的影响，这由ζ电位对pHbulk的依赖性证明。最后，作为原理上的证明，我们证明了可以通过对MSN表面进行适当的官能化调节pHint来控制酸敏感性乙缩醛的水解速率。我们的发现可以导致开发纳米反应器，从而保护敏感物种免受不利条件的影响并调整其化学反应性。