A pH sensitive fluorescent carbon dots for urea and urease detection

In this manuscript, a pH-sensitive carbon dots were prepared by directly carbonizing m-phenylenediamine aqueous solution in high pressure autoclave. The prepared carbon dots were gradually protonated with the increase of hydrogen ions concentrations. The fluorescence of prepared carbon dots gradually decreased with the pH value increasing from 3.0 to 9.4, and there existed a well linear relationship between fluorescence intensity at 520 nm and pH value in the range from 6.2 to 8.6. Therefore, the prepared carbon dots showed the potential to be a fluorescent probe for pH detection. Based on the pH-responsive fluorescent carbon dots and urease-catalyzed hydrolysis of urea, we further proposed an assay system for the determination of urea and urease respectively in the range from 0.05 to 3.0 mmol center dot L-1 and 2.5 to 80 mg center dot L-1.