Novel and Fast Microwave-Assisted Synthesis of Carbon Quantum Dots from Raw Cashew Gum

Abstract

Carbon quantum dots (C-dots) with average size of 9 nm were synthesized from an aqueous solution of raw cashew gum (RCG) using a novel and fast microwave-assisted technique which involves two steps.In the first step (partial depolymerization in solution) some monomer units are formed through the autohydrolysis of CG and a small amount of 5-hydroxymethyl furfural can be obtained.The second step involves polycondensation/polymerization to give rise to a polyfuranic structure followed by aromatization/carbonization and nuclear burst.At the end of the process a composite of partially depolymerized CG and C-dot was formed.A mechanism involved in microwave-assisted two-steps synthesis was suggested.Although no passivation reagent was used, an intensely blue photoluminescent material in UV light was obtained.C-dot was characterized by spectroscopy in the medium infrared, thermal analysis, gel permeation chromatography, transmission electron microscopy, zeta potential, and photoluminescence.