A novel "off-on" fluorescence nanosensor for sensitive determination of sulfide ions based on carbon quantum dots and gold nanoparticles: Central composite design optimization

In this research, a novel turn off-on fluorescent sensor for indirect determination of sulfide ions in aqueous media was designed based on carbon dots (CDs). This probe was established by using carbon dots in the present of gold nanoparticles (GNPs) and utilized as a fluorescence-enhancement probe. In this sensor, GNPs quenches the fluorescence of the CDs while addition of sulfide ions removes GNPs from the surface of CDs, resulting in regeneration of fluorescence intensity. The three factors of pH, time and temperature were selected for their effects on the sensing function to be optimized. The optimization of parameters was done by central composite design (CCD) through response surface methodology (RSM) application. The sensing results have proved the high selective and sensitive performance of the sensor. The linear range is 1.00-19.50 ppm and the detection limit is 0.57 ppm. The relative standard deviation (RSD) of the reported method is 2.53%.