A novel core-shell structure optical pH sensor is developed with upconversion nanoparticles (UCNPs) serving as the core and silica as the shell, followed by grafting bovineserumalbumin (BSA) as another shell via glutaraldehyde cross-linking. The obtained core-shell-shell structure is shortly termed as [email protected]₂@BSA, and its surface provides a platform for loading various pH sensitive dyes, which are alike “modules” to make it feasible for measuring pHs within different pH ranges by simply regulating the type of dyes. Generally, a single pH sensitive dye is adopted to respond within a certain pH range. This study employs bromothymol blue (BTB) and rhodamine B (RhB) to facilitate their responses to pH variations within two ranges, i.e., pH 5.99–8.09 and pH 4.98–6.40, respectively, with detection by ratio-fluorescence protocol. The core-shell-shell structure offers superior sensitivity, which is tens of times more sensitive than those achieved by ratio-fluorescence approaches based on various nanostructures, and favorable stability is achieved in high ionic strength medium. In addition, this sensor exhibits superior photostability under continuous excitation at 980 nm. Thanks to the near infrared excitation in the core-shell-shell structure, it effectively avoids the self-fluorescence from biological samples and thus facilitates accurate sensing of pH in various biological sample matrixes.

开发了一种新型的核-壳结构光学pH传感器，其中以上转换纳米颗粒（UCNPs）为核，以二氧化硅为壳，然后通过戊二醛交联接枝牛血清白蛋白（BSA）作为另一个壳。所获得的核-壳-壳结构简称为[电子邮件保护] ₂@BSA及其表面提供了一个装载各种pH敏感染料的平台，它们类似于“模块”，通过简单地调节染料类型就可以在不同pH范围内测量pH。通常，采用单一的pH敏感染料在一定的pH范围内响应。这项研究使用溴百里香酚蓝（BTB）和若丹明B（RhB）来促进它们对pH范围在两个范围内的响应，即pH 5.99–8.09和pH 4.98–6.40，并通过比率荧光协议进行检测。核-壳-壳结构具有出色的灵敏度，比基于各种纳米结构的比率荧光方法所获得的灵敏度高数十倍，并且在高离子强度介质中实现了良好的稳定性。此外，该传感器在980 nm的连续激发下表现出卓越的光稳定性。得益于核-壳-壳结构中的近红外激发，它有效地避免了生物样品的自发荧光，因此有助于准确检测各种生物样品基质中的pH值。