Green and high-yield synthesis of carbon dots for ratiometric fluorescent determination of pH and enzyme reactions.

In this work, the carbon dots (CDs) were prepared by one-pot hydrothermal method with chitosan as a carbon source and hydrogen peroxide as an oxidant, this route is a novel, simple and green. The prepared CDs has a relatively high photoluminescence (PL) quantum yield (QY) (18.9%) and good water solubility. CdTe quantum dots (CdTe QDs) possess the characteristic of responding to pH rapidly. So a ratiometric fluorescent probe for measuring pH was constructed using the prepared CDs and CdTe QDs. Under the excitation of 330 nm, the probe shows dual (blue and red) emission with peaks at 430 and 600 nm, respectively. When the pH of the solution changes, the blue fluorescence intensity of the CDs remains stable as a reference signal, while the red fluorescence intensity of CdTe QDs changes accordingly. This method has obvious pH-sensitive feature, stable fluorescence properties, and a great linear relationship with pH values in the range of pH 3.0–11.0. What is more, the method can monitor proton-producing enzyme-catalyzed reactions by acting as a ratiometric pH probe. Carbon dots were prepared by one-pot hydrothermal method with chitosan as a carbon source and hydrogen peroxide as an oxidant, and a ratiometric fluorescence was constructed for determination of pH and enzyme reactions based on carbon dots and CdTe quantum dots. Unlabelled Image • Carbon dots were prepared by one-pot hydrothermal method with chitosan as a carbon source and hydrogen peroxide as an oxidant. • A ratiometric fluorescence was constructed for determination of pH based on carbon dots and CdTe quantum dots. • The pH sensor was used to monitor proton-producing enzyme-catalyzed reactions by acting as a ratiometric pH probe. [ABSTRACT FROM AUTHOR]