5th International Eurasian Conference on Biological and Chemical Sciences, Ankara, Turkey, 23 - 25 November 2022, pp.67
Graphitic carbon nitride (g-C3N4, referred to CN) is a well-known semiconductor used as a photocatalyst in the visible region. In this study, CN was synthesized by a one-step heat treatment method using a dicyandiamide precursor, and its surface was modified (called as PEGylated) with a short polymer chain, poly(ethylene glycol) methyl ether (PEGME550, referred to PEG). The synthesized and PEGylated CN samples were characterized by typical analysis techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), Brunauer–Emmett–Teller (BET) specific surface area analysis, and scanning electron microscopy (SEM). The XRD patterns well-demonstrated the formation of graphitic carbon nitride layers. The grafting density of PEG chain to the CN surfaces was determined as 4.48 x 10-2 mmol/g from thermogravimetric analysis (TGA) results. The optical bandgap energies of synthesized and PEGylated CN were estimated as 2.75 and 2.80 eV, respectively, using the Tauc plot from the DRS spectra. The effect of PEGylation on the photocatalytic activity of CN was evaluated by photodegradation of organic dye RhB under visible light illumination. Based on the reduction in RhB absorption intensity centered at 553 nm, the synthesized CN degraded RhB by 22% after 6 hours of light irradiation, while the PEGylated CN decomposed RhB by 48%. A pseudo-first-order reaction kinetic model was applied to quantitatively investigate the photocatalytic activity of the samples. Accordingly, the degradation rate constants of RhB over the PEGylated and synthesized CN were 0.1064 and 0.0415 h-1, respectively, meaning that PEGylated CN showed 2.56 times higher photocatalytic performance compared to that of the pure CN. As a result, this study shows that the photocatalytic activity of CN is significantly increased by grafting oxygen-containing functional groups (herein PEG) to the CN unit without disturbing the crystal structure.