Photoluminescence enhancement of 1,2,4-triaminobenzene molecules by modification with hydrolytically polycondensed 3-aminopropyltriethoxysilane

Small-molecule dyes with longer wavelength and higher photoluminescence quantum yield (PLQY) in water have attracted increasing attention due to their bright potential in fluorescence analysis technologies. Here, a red-emitting fluorescent dye of 1,2,4-triaminobenzene (TriAB) was modified with 3-aminopropyltriethoxysilane (APTES) to avoid contact with water molecules and to suppress fluorescence quenching due to O-H vibrations in water. The formation of a silica-like structure from hydrolytically polycondensed APTES was confirmed by X-ray diffractometry and Fourier-transform infrared absorption spectroscopy. Modification of TriAB with hydrolytically polycondensed APTES induced orange emission in the powder state, although TriAB powder did not exhibit any fluorescence before modification. The PLQY of APTES-modified TriAB in water was 11.1 %, which was higher than that of TriAB in water, 4.5 %. These results confirmed that the APTES derived silica-like matrix shielded TriAB from both water and intermolecular interactions with other TriAB molecules, overcoming fluorescence quenching.