Novel water-dispersible silicon nanoparticles as a fluorescent and colorimetric dual-mode probe for emodin detection

In this study, a colorimetric and fluorescent dual-mode probe based on water-dispersible silicon nanoparticles (SiNPs) was fabricated via a one-step hydrothermal method by using (3-aminopropyl)triethoxysilane (APTES) as the silicon source and ferulic acid as the reducing agent. The as-prepared SiNPs exhibited good thermostability, high salt-tolerance and excellent photo-stability properties. The blue-green fluorescence of the SiNPs could be rapidly and selectively quenched by emodin, and meanwhile the colorimetric response from the original pale yellow color to reddish brown was also visible to the naked eye. Based on the above phenomenon, the quantitative detection of emodin could be achieved through both fluorescence and colorimetric methods. In the fluorescence method, a good linear relationship was obtained in the range of 0.05 to 50 μM with a detection limit of 5.77 nM. In the colorimetric method, comparable sensitivity was also achieved with a detection limit of 9.28 nM. The proposed method was successfully applied to the detection of emodin in traditional Chinese herbs Polygonum cuspidatum and Rheum officinale. Moreover, a SiNP based dual-mode paper sensor was also developed for the visual detection of emodin according to the color change and fluorescence quenching, providing a convenient strategy for emodin sensing.