Investigation of phosphorous doping effects on polymeric carbon dots: Fluorescence, photostability, and environmental impact

Abstract Carbon dots have arisen as a potential alternative to traditional quantum dots since they fluoresce but are synthesized from sustainably sourced green chemicals. Herein, fluorescent nitrogen-doped polymeric carbon dots (CDs) were synthesized by using citric acid (CA) or malic acid (MA) as carbon precursors and ethylenediamine as the nitrogen precursor. Additionally, phosphoric acid was used as a doping agent for each type of CDs to evaluate the impact of incorporating phosphorus into the nanoparticles. Thus, four kinds of doped CDs (N-doped or N, P co-doped) were obtained and named as CACDs, CA-P-CDs, MACDs, and MA-P-CDs. Quantum yield and fluorescence lifetime analysis indicate that phosphorus doping of up to c.a. 10 wt% does not induce a remarkable influence on CD photoluminescence. The photostability of the N, P co-doped MACDs (MA-P-CDs), however, was observed to increase compared to the N-doped MACDs under 350 nm UV (UV-B) exposure. Lastly, to assess the impact of this emerging nanoparticle on prokaryotes, the bacterial toxicity of these CDs was tested using Shewanella oneidensis MR-1 as a model microorganism. Interestingly, the CDs exhibited no toxicity in most cases, and in fact facilitated bacteria growth. Hence, this work suggests that CDs are potentially eco-friendly fluorescent materials.