Synthesis and Characterization of Graphene Quantum Dots Functionalized Silver Nanoparticle from Moringa Oleifera Extracts

Abstract

Graphene quantum dots (GQDs) are famously known for large surface area, good dispersibility, good conductivity, and high transparency with good photochemical, electrochemical, and optical properties that are utilized in many biomedical and biotechnological applications. Interestingly, GQDs were reported to serve as an excellent reducing reagent in the synthesis of noble metal nanoparticles such as silver nanoparticles (AgNPs). Moreover, GQDs eradicate the limitation of impurities of AgNPs synthesized using plant extracts as a stabilizer and reducing agents. Therefore, we experimented GQDs synthesis from moringa oleifera (MO) plant extracts compared to citric and urea synthesized GQDs. And used the synthesized GQDs to synthesize, reduce and functionalize AgNPs. MO contains about 110 compounds, high nutrients, vitamins, oleic oil, and phytoconstituents such as alkaloids, flavonoids, glucosinolates, saponins, tannins, terpenes, steroids, phenolic acids, which suggested to us that, MO extracts can serve as a capping agent in the synthesis of nanoparticles. Initially, MO leaves and seeds water phase extracts were obtained by overnight distillation and lyophilized to create a stock solution of 1mg/ml. Next, following Das, R. et al and slightly modifying the followed method by varying the MO extract concentration from 20µL to 60 µL, AgNPs were synthesized by hydrothermal method. GQDs were separately synthesized adopting Tran, H.V. et al method and later added to the AgNPs forming a more stable hybrid structure that was characterized using the UV-vis spectroscopy (UV-Vis), Nano zeta sizer, Raman spectroscopy, and the Fourier Infrared transmission resonance (FTIR). As the concentration of MO extract increased, the color change intensity increased symbolizing the formation of AgNPs while the luminous bright solutions under the UV light symbolized the formation of GQDs. This study lay the foundation for further research and analysis to be done on the nanozyme or biosensor application of enhanced functionalized and stable hybrid AgNPs with GQDs.