Ultrastable and ultrasensitive pH-switchable carbon dots with high quantum yield for water quality identification, glucose detection, and two starch-based solid-state fluorescence materials

It is attractive and encouraging to develop new fluorescent carbon dots (CDs) with excellent optical properties and promising applications prospects. Herein, highly-efficient green emissive CDs (m-CDs) with a high quantum yield (QY) of 71.7% in water are prepared through a facile solvothermal method. Interestingly, the m-CDs exhibit excellent fluorescence stability in the pH range of 1-9. However, the fluorescence intensity of the m-CDs is almost completely quenched as the pH is increased from 9 to 10. The mechanism of the unique pH-responsive behavior is discussed in detail and a plausible mechanism is proposed. Owing to the unique pH-responsive behavior, the m-CDs are used as a on-off fluorescent probe for water quality identification. By combining the reversible pH-ultrasensitive optical properties of the m-CDs in the pH range of 9-10 with the glucose oxidase-mimicking (GOx-mimicking) ability of Au nanoparticles (AuNPs), glucose can be quantitatively detected. Finally, two environment-friendly starch-based solid-state fluorescence materials (powder and film) are developed through green preparation routes.