High Product Yield Synthesis of Nitrogen Doped Carbon Dots through Exothermic Reaction for Temperature Sensing and Tartrazine Detection

Rapid, green and high yield synthesis of nitrogen doped carbon dots(N-CDs) through exothermic decomposition reaction of H2O2 using grasshopper powder as precursor and polyethyleneimine (PEI) as a surface passivation reagent. Water-soluble fluorescent N-CDs can be obtained by reacting 5 minutes and purified N-CDs were obtained after an activated carbon adsorption separation procedure with a product yield of 53.3%. TEM, FT-IR, XPS, fluorescence and UV-vis spectra were used to investigate the morphology, elemental information and optical properties of N-CDs. The results indicated that the fluorescence emission of N-CDs is typical excitation wavelength dependent with a strongest emission peak at 417 nm under 330 nm excitation wavelength. There is a good linear response between the fluorescence intensity of N-CDs and temperature, which makes N-CDs a potential nanothermometer to monitor temperature. The great spectral overlap between the blue emission peak (417 nm) of N-CDs and the absorption peak (430 nm) of tartrazine (TAR) leads to an effectively fluorescence quenching phenomenon by TAR through inner filter effect (IFE) and the fluorescence quenching degree (lg(I0/I)) was linearly response to the  TAR concentration in the range of 1-100 µM. The detection limit of developed method is 54.3 nM  for TAR, and the relative standard deviation (RSD) is 1.14% (n=7, c=10 μM). The N-CDs came  from an exothermic reaction is a highly selective and sensitive fluorescent probe for TAR,  and it was successfully applied to the determination of TAR in food samples with satisfactory results.