Reflectance and photophysical properties of rhodamine 6G/2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid as cold hybrid colorant

Rhodamine 6G (Rh6G) is modified by ethylenediamine to obtain rhodamine with amine functional groups (Rh6G-NH2). Rh6G-NH2 as an initial core is used to bond coumarin derivatives. Synthesized fluorescent colorants are specified using Fourier transform infrared spectroscopy (FT-IR), proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) to analyze the structure of the fluorescent pigments. Fluorescence microscopy, fluorescence spectrophotometer, and UV–visible–NIR reflectance spectra are used to demonstrate the optical properties. UV–Vis–NIR reflectance spectra showed that synthesized colorants were transparent in NIR region. Also, photophysical properties of 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid (MOHCYAA), Rh6G-NH2, and hybrid 2-(4-methyl-2-oxo-2H-chromen-7-yloxy) acetic acid/rhodamine 6G (HMR) were investigated. Type of solvent had a strong effect on quantum yield. Rh6G-NH2 (ϕs = 0.66) and HMR (ϕs = 0.72) displayed the maximum quantum yield in ethanol due to good interaction with ethanol and the formation of ring-opened amide form of rhodamine group. Finally, Rh6G-NH2 and HMR displayed the maximum quantum yield in ethanol due to good interaction of structure with ethanol and the formation of ring-opened amide form of rhodamine group in compound.