We report a one-pot hydrothermal synthesis of water dispersible luminescent silicon-based nanoparticles (SiNPs) functionalized by amino groups, starting from aminopropyltriethoxy silane and ascorbic acid. The structure, surface chemistry and optical features of the resulting SiNPs are well characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, UV-vis absorption spectra, transient and steady-state fluorescence. The products show high tolerability to extreme pH and high ionic strengths, and excellent photo-stability under UV irradiation, laying the foundation for their practical applications. As a fluorescent sensor, SiNPs have been used to sensitively determine oxytetracycline (OTC); particularly, they can distinguish OTC from other antibiotics with similar structure among the tetracyclines' (TCs') family. In the presence of OTC, the blue emission at 436 nm of SiNPs is dramatically quenched. Meanwhile, a new green emission, peaking at 502 nm, appears and increases with the titration of OTC. Thereby, the trace of OTC can be monitored by SiNPs based on ratio between the two fluorescent intensities (I₅₀₂/I₄₃₆). The I₅₀₂/I₄₃₆ displays a good linear response to OTC concentrations in the range of 0.2 μM to 20 μM with a detection limit of 0.18 μM. Finally, this newly developed protocol is successfully used to determine OTC in milk and the observed recoveries suggest the sensor can serve as an effective tool to detect OTC in foodstuffs.

Preparation of Si NPs and the “on–off–on” fluorescence strategy for Mn ²⁺ detection.