SYNTHESIS AND CHARACTERIZATION OF ZINC-DOPED CARBON DOTS FOR ENHANCED FLUORESCENCE APPLICATIONS

Abstract

In this work, zinc-doped carbon dots (Zn-CDs) were successfully synthesized using a simple one-step hydrothermal approach, employing citric acid and urea as carbon precursors, with zinc introduced as the dopant source. Transmission electron microscopy revealed that the synthesized nanoparticles were uniformly distributed, with an average particle size of 3.6 ± 0.5 nm. UV–visible spectroscopy showed a pronounced absorption peak at 360 nm, corresponding to π–π* electronic transitions. Upon excitation at 365 nm, the Zn-CDs exhibited a strong photoluminescence emission centered at 445 nm. Notably, zinc doping led to a significant enhancement in fluorescence performance, with an increase of 52.8% in emission intensity and a quantum yield of 38%, which is approximately 1.6-fold higher than that of pristine carbon dots. The successful incorporation of Zn²⁺ ions was confirmed by spectroscopic analysis, displaying characteristic Zn 2p₃/₂ and Zn 2p₁/₂ peaks at binding energies of 1022.1 eV and 1045.2 eV, respectively. The enhanced photoluminescence can be attributed to improved surface passivation and the formation of zinc-related defect states that promote radiative recombination. Furthermore, the Zn-CDs demonstrated excellent photostability, retaining more than 95% of their fluorescence intensity after 120 minutes of continuous UV exposure, highlighting their strong potential for applications in optical sensing and bioimaging.