Upconversion emission of fluorescent silver nanoclusters and in situ selective DNA biosensing

Due to their good photostability, high quantum yield and low toxicity, fluorescent silver nanoclusters (Ag NCs) have received much attention as novel fluorophores for sensing applications. In this work, we investigate the upconversion emission of Ag NCs templated by single- and double-stranded DNAs. DNA-templated Ag NCs exhibit upconversion emission at wavelengths identical to those observed for the corresponding Stokes emission. Consequently, the Ag NCs' upconversion behavior can be easily tuned by the used DNA sequences. In addition, the Ag NCs are more stable under such an NIR excitation with the upconversion mode relative to the Stokes mode. As a proof-of-concept application, DNA nucleobase recognition with the in situ formed Ag NCs is realized using the Ag NCs' upconversion emission. We expect that the Ag NCs' upconversion emission is more advantageous than the previously used rare-earth materials, at least with respect to easy modulation of the emission energies by DNA sequences, and could find wide application in sensor design.

由于其良好的光稳定性、高量子产率和低毒性，荧光银纳米簇（Ag NCs）作为用于传感应用的新型荧光团受到了广泛关注。在这项工作中，我们研究了以单链和双链DNA为模板的Ag NCs的上转换发光。以DNA为模板的Ag NCs在与相应斯托克斯发光所观察到的相同波长处呈现上转换发光。因此，Ag NCs的上转换行为可通过所使用的DNA序列轻松调节。此外，在这种近红外激发下，相对于斯托克斯模式，Ag NCs在上转换模式下更稳定。作为概念验证应用，利用Ag NCs的上转换发光实现了对原位形成的Ag NCs的DNA核碱基识别。我们预计Ag NCs的上转换发光比先前使用的稀土材料更具优势，至少在通过DNA序列轻松调节发射能量方面是如此，并且可在传感器设计中得到广泛应用。