Green Synthesis of Carbon Dots and Their Application as Photocatalyst in Dye Degradation Studies

Abstract

This paper presents work on green synthesis of the carbon dots from leaves of Elettaria cardamomum (E.C) using simple ultra-sonication technique. In X-ray diffraction analysis, peak at 2θ value of 22.9° confirmed the amorphous nature of synthesized carbon dots. Furthermore, Raman investigations of the synthesized carbon dots illustrated D and G band at 1365 cm−1 and 1575 cm−1, respectively, showing graphitic structure of carbon dots. Similarly, Fourier transform infrared spectrum of carbon dots confirmed the presence of different functional groups such as C=O, C=C, OH, C–OH at absorption peaks values of 1715 cm−1, 1634 cm−1, 3257 cm−1 and 1027 cm−1, respectively. Photoluminescence spectral analysis of carbon dots confirms photoluminescent nature by exhibiting two emission peaks at 520 nm and 850 nm, respectively. UV–visible spectrophotometric investigations confirmed the presence of carbon dots showing two absorption peaks at 220 nm and 272 nm. After confirmation and characterization, the synthesized carbon dots were utilized for studying visible light-induced degradation of congo red and methylene blue dyes. This further investigation showed that the maximum degradation of congo red dye was observed in acidic media at pH 4 with a dye concentration of 5 ppm in a time interval of 50 min. For methylene blue dye, optimum degradation was observed in alkaline medium at a pH value of 8 with 5 ppm dye concentration in a time interval of 55 min.