Introduction: Higher concentrations with doping precursors, especially nitrogen compounds, along with metal doping, can simultaneously shift the emission wavelength of carbon dots toward longer wavelengths, improving crystallinity.
Methods: In this study, carbon quantum dots with simultaneous metal and non-metal doping of Zn, N, S CQDs were synthesized using carbon precursors citric acid monohydrate ZnCl2, PEG400 and thiourea in aqueous solution by hydrothermal method. Our syntheses were carried out with the same volume of 30 ml in three ratios of 1:1, 1:2, 1:5 citric to thiourea at a constant temperature of 185 °C for 8 hours by hydrothermal method and the results of wavelength changes to redshift with increasing thiourea to citric acid ratio and improved penetration of metal ions into the carbon dots structure were reported.
Results: The first sample recorded an emission wavelength at 458 nm with a peak intensity of 864, QY23% at an excitation wavelength of 400 nm, the second sample recorded an emission wavelength at 471 nm with an intensity of 917, QY17%, and the third sample recorded an emission wavelength of 522 nm with a QY of 810, QY30%.
Conclusion: More nitrogen doping along with metal doping increases the wavelength.
Keywords: Bio-carbon dots, wavelength enhancement, nitrogen doping, biosensing, cancer detection