Oxazine-Functionalized CdSe/ZnS Quantum Dots for Photochemical pH Sensing

pH is the most important chemical parameter of an aqueous solution, and it is widely used in biochemistry, environmental science, and other fields. In this article, we have successfully prepared an application-type ratiometric photochemical pH sensor combining semiconductor nanomaterial CdSe/ZnS quantum dots (QDs) and oxazine 170 perchlorate (O170). This sensor facilitated fluorescence resonance energy transfer (FRET) between CdSe/ZnS QDs (donor) and O170 (acceptor) due to the dipole–dipole interaction. Molar absorption coefficient, Foster radius, and FRET efficiency were determined, and the experimental FRET efficiency was found to be very close to the theoretical value. Thus, we utilized the interaction of QD nanomaterials and the O170 dye to promote oxazine-functionalized CdSe/ZnS QDs and revealed the principle of the FRET-based sensor. We mixed these two substances to form a sensitive film that covered the end face of an optical fiber. The experimental results showed that the FRET-based fiber-optic pH sensor exhibited a large detection range and good performance in terms of linearity, sensitivity, and repeatability. The pH sensor studied by the photochemical method has great application potential in the fields of marine monitoring and environmental protection.