novel nitrogen-doped carbon dots for degrading azo dyes and sensing heavy metals

This work presents an application perspective of recently developed, novel green synthesized self-heteroatom doped n-carbon dots (n-cds) derived from biomass pumpkin seeds, possessing an energy gap of 2.35 ev and an unremarkable quantum efficiency of 65.5%, besides a graphitic carbon structure they are doped with various metal and nonmetal ions and an overall size distribution of 5-8 nm. here we have used them as a novel photocatalyst by mixing them with widely known photocatalyst titanium dioxide, thereby enhancing the overall photocatalytic efficiency of the amalgam of both materials. further, this novel amalgam of carbon dots has demonstrated a well-distinguished ftir, xrd, and uv absorbance and emission wavelength spectra, and displayed a broad absorbance wavelength spectra in lower energy region, hence more efficient compared to pure titanium dioxide. thus the composite of tio2/n-cds degraded congo red dye in a short duration of 18 minutes, illuminated under uv light, and has shown 90% degradation efficiency. however, only 40% degradation was shown by pure n-cds. further, we have used these carbon dots as a sensing material for the detection of heavy metal ions and the results have demonstrated a good detection limit of the heavy metal hg2+ ions among other tested metal ions, owing to its excellent selective and sensitive property of fluorescent quenching analysis, resulted in the creation of non- fluorescent centers, effective charge transfer and overall energy transfer, with a minimum detection threshold limit of 20 nm.