Intrinsic dual-emitting Si dots for high-precision and broad-range pH detection

High-precision and broad-range pH detection is critical for health status assessment, such as signal transduction, enzyme activity, endocytosis, and cell proliferation and apoptosis. Although pH-responsive ratiometric fluorescent probes offer an effective pH monitoring strategy, their preparation often requires multi-step modification and decreases fluorescence efficiency and stability. Herein, we developed a simple method to prepare fluorescent Si dots with dual emission centers for high-precision and broad-range pH monitoring, and the detection of urease based on pH-responsive Si dots and pH monitoring in living cell was further explored.

The dual-emitting Si dots had two emission centers at 427 nm and 500 nm. The emission at 427 nm showed a fluorescence enhancement and effective quenching in the pH ranges of 3.0-10.0 and 10.0-12.0, respectively. While the emission at 500 nm increased gradually with increasing pH from 3.0 to 12.0. Two linear relationships were obtained between the synchronous fluorescence intensity ratio and pH in the ranges of 7.0-9.5 and 10.0-12.0 with a △pH of 0.1, indicating a broad detection range and high precision. Then the Si dots were used to detect urease activity via urea hydrolysis-mediated pH changes. A linear range of 1-80 U/L was established with a detection limit of 0.28 U/L. Furthermore, the Si dots were used for pH imaging in living HeLa cells. The cells changed from green to blue when the pH of HeLa cells increased from 6.0 to 10.0.

These findings collectively suggest that the intrinsic dual-emitting Si dots may offer a simple and versatile platform for developing pH-relevant biosensors and bioimaging applications. Additionally, this approach provides reliable methods for preparing intrinsic dual-emitting probe and constructing fluorescence ratiometrics, which widely used in health status assessment.