On–Off–On fluorescence sequential sensor for silver ions, thiamine and anti-counterfeiting application using mannitol derived carbon dots

Abstract

We are reporting the synthesis of mannitol derived carbon dots (MCDs) and their application as silver ion and thiamine sensors. The synthesized MCDs were characterized by HR-TEM, FT-IR, UV–visible, fluorescence, XRD and Raman methods. The synthesized MCDs exhibit a blue emission at 444 nm and the quantum yield of the MCDs is 43.8%. The MCDs particle size was determined to be 3.09 nm with a mono-dispersed nature, using HR-TEM images. Next, we have used MCDs as a probe for the detection of silver ions and thiamine. Interestingly, the highly blue emitting MCDs fluorescence was quenched (ON–OFF) upon the addition of silver ions. On addition of thiamine into the same solution, the fluorescence was enhanced (OFF–ON) . Based on the emission intensity changes, we determined the concentrations of silver ions and thiamine. The limit of detection of silver ions and thiamine were calculated to be 0.5 nM and 0.57 nM (LOD = 3 S/m), individually. The MCDs show high selectively towards the detection silver ions and thiamine. To this end, we have applied this sensor method for the sensing of silver ions in water, silver antibiotic sulfadiazine cream and also thiamine in drugs and biological samples. Notably, we have developed a wax pencil, designed for on-site monitoring of silver ions and thiamine with a wax coated paper based kit. Further, we have successfully prepared an anti-counterfeiting fluorescent ink using mannitol derived carbon dots and a PEG solution. Our anti-counterfeiting fluorescent ink is a low cost material, easy to use and it can replace the commercially available fluorescent inks.