4-aminoantipyrine modified carbon dots and their analytical applications through response surface methodology

A sensitive and selective nanoprobe for detection of hypochlorite (OCl^-) based on 4-aminoantipyrine (AAP) modified carbon dots (CDs-AAP) has been prepared. The CDs-AAP exhibit an emission peak at 484 nm when the excitation wavelength is 370 nm, accompanying 36 nm red shift compare with the pristine CDs. The addition of OCl^- lead to the AAP on the surface of CDs experience a process of hydrazide hydrolysis and double bond addition, causing the singlet and triplet electrons of the excited state more closer in energy (ie, the energy difference between the two is reduced), eventually quenching the fluorescence of CDs due to heavy atomic effects. Central composite design (CCD) and response surface method (RSM) were used to optimize the detection variables of pH, incubation time and temperature. The designed model study indicated that the optimum detection conditions was pH 7.0, temperature 30 °C and incubation time 20 min, respectively. Under optimal conditions, the fluorescent intensity of the nanoprobe linearly responded to the OCl^- concentration from 3 μM to 36 μM and the limit of detection was 40 nM. The proposed nanoprobe was successfully used to the detection of OCl^- in tap water and pool water, and the recovery were in the range of 94% - 103%. In addition, the nanoprobe was also applied in imaging of VMSCs cells and labeling E.coli.