An Interactive Quantum Dot and Carbon Dot Conjugate for pH‐Sensitive and Ratiometric Cu²⁺ Sensing

Herein we report the photoinduced electron transfer from Mn 2+ ‐doped ZnS quantum dots (Qdots) to carbon dots (Cdots) in an aqueous dispersion. We also report that the electron transfer was observed for low pH values, at which the oppositely charged nanoparticles (NPs) interacted with each other. Conversely, at higher pH values the NPs were both negatively charged and thus not in contact with each other, so the electron transfer was absent. Steady‐state and time‐resolved photoluminescence studies revealed that interacting particle conjugates were responsible for the electron transfer. The phenomenon could be used to detect the presence of Cu 2+ ions, which preferentially, ratiometrically, and efficiently quenched the luminescence of the Qdots.