A spectroscopic investigation of Carbon dots and its reduced state towards fluorescence performance

Abstract

Carbon dots are shown to have potential applications in the areas ranging from catalysis, bioimaging, drug delivery, energy and electronics etc. Owing to its excellent fluorescence property, facile synthesis method and robust chemical inertness, it has become one of the most studied materials for this decade. In present work, hetero-atom doped carbon dots and its reduced forms were studied in detail for their optical properties. A heteroatom (nitrogen, boron, and fluorine) co-doped carbon dots (CNBF) was synthesized (using citric acid as a primitive carbon source). Further, CNBF was reduced with different concentrations of sodium borohydride (NaBH4) leading to the synthesis of rCNBF1, rCNBF2, and rCNBF3. The distinct optical characteristics of CNBF, rCNBF1, rCNBF2 and rCNBF3 were studied using different spectroscopic techniques. The quantum yield and fluorescence lifetime of the reduced forms rCNBF1, 2 and 3 were 39.14%; 41.73%; 44.61 and 13.30 nS, 13.52 nS, 14.21 nS, respectively which was higher than CNBF having a quantum yield of 35.73% and 11.98 nS. It was observed the energy bandgap of rCNBF was higher than CNBF suggesting the functional group modification due to reduction which tuned the optical behaviour. Afterward using transmission electron microscope (TEM) morphologies of CNBF and rCNBF were studied. This study opens a new avenue in designing fluorescent materials using functional group modifications having potential emerging applications. © 2020 Elsevier B.V.