Fluorescent Carbon Dots Decorated with ONN Donor Sites by Using Schiff Base Silatrane for Selective Recognition of Mefenamic Acid in Environmental Samples

The microwave-assisted synthesis of fluorescent carbon dots decorated with ONN donor sites (CDs@SBONN) by using the silatranyl derivative of Schiff base is described in this study. The formation of Schiff base (SBONN) and Schiff base silatrane (Silt-SBONN) is confirmed by spectroscopic studies, including Fourier transform infrared spectroscopy, nuclear magnetic resonance, mass spectrometry, and single-crystal X-ray diffraction. The structural parameters of CDs@SBONN have been investigated using thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, Brunauer–Emmett–Teller analysis, and X-ray photoelectron spectroscopy analysis. The ONN donor sites in CDs@SBONN interact with the mefenamic acid (MA) selectively out of different drugs (such as ibuprofen, acetylsalicylic acid, naproxen, diclofenac, and ketoprofen), amino acids (like glycine, valine, and alanine), excipients (like glucose and urea), cations (like Cd2+, Cu2+, Fe3+, and Cr3+), and anions (like Cl–, AcO–, NO3–, and SO42–), and display a quenching signal at λems = 460 nm (λexc = 360 nm). The quenching of the signal is linear in the range of 100–800 nM, and the limit of detection is 40.8 nM. Furthermore, the 1H NMR titrations, fluorescence lifetime studies, density functional theory calculations, and Zeta potential (ζ) studies clarify the interaction through COOH and NH groups of MA and CHN and OH sites of Silt-SBONN. The standardization of the analytical method offers applicability of CDs@SBONN for the evaluation of MA with high accuracy and recovery range in pharmaceutical samples (89.42–102.55) and river water (98.05–100.79) with a relative standard deviation of ONN can have a promising potential application in environmental and biological analysis.