Photophysical and reflectance properties of perylene-3,4,9,10-tetracarboxylic diimide (PTCDI)/rhodamine 6 G hybrid for application in cold paints

Abstract

There is an extensive range of applications for fluorescent pigments based on their optical properties. Herein, we focused on the synthesis of a highly fluorescence colorant, a hybrid of perylene-3,4,9,10-tetracarboxylic diimide and rhodamine 6 G (PTCDI-Rh6 G). To this end, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) is modified with ethylenediamine (EDA) to yield PTCDI. Then, PTCDI is reacted with rhodamine 6 G by an amidation reaction. Synthesized colorants are characterized using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and X-ray diffraction (XRD) techniques to analyze the structure of the fluorescent pigments. Field emission scanning electron microscopy (FE-SEM) is used to present the morphology of fluorescent pigments and thermogravimetric analysis (TGA) is utilized to investigate thermal stability. Fluorescence microscopy (FM), fluorescence spectrophotometer (FL), and near-infrared (NIR) reflectance spectra are used to demonstrate the optical properties. Also, fluorescence quantum yield (Φf) of PTCDI-Rh6 G hybrid was calculated in various solvents of H2SO4, DMSO, ethanol, and DMF as obtained 0.06, 0.13, 0.01, and 0.27, respectively. As a result, two optically different substrates namely high absorptive substrate and high reflective substrate are used to investigate the NIR reflectance, and the correlation between the structure of pigments and NIR reflectance. Finally, crystallinity was obtained 85.7 %, 62.9 %, and 31.5 % for PTCDA, PTCDI, and PTCDI-Rh6 G derivatives. NIR reflectance was very sensitive to the degree of crystallization. PTCDI had a reflection of 57 % in range of 700−1000 nm and showed good transparency, while PTCDI-Rh6 G hybrid showed a weaker reflection of 29 %. PTCDI showed better performance in cold colors compared to PTCDI-Rh6 G hybrid.