Separation of photoluminescent fragment from the silica spheres modified the surface with 3-mercaptopropyltrimethoxysilane

Photoluminescent fragment was separated from the silica spheres modified the surface with 3-mercaptopropyltrimethoxysilane. The spheres were synthesized with the Stöber synthetic method, washed three times with acetone and stored in acetone for 12, 20, and 60 days. The solution color became yellow to dark red with the increase of the storing time. The UV-visible absorption spectra show absorption shoulder at 320 nm for only 60 days sample. Although the major Fourier transform infrared absorption peaks are similar for the 20 and 60 days samples, medium and small absorption peaks for the 20 days samples are not clear compared with 60 days samples. The absorption peaks at 3315, 2869/2968, 2928, 1703, 1294, 1185, 1219, 1080/1033, 971 and 864/761 cm−1 represent C–OH, R–CH3, R2–CH2, –C=O, C–O, C=S, C–C, Si–O–Si, Si–O–C and Si–C absorption, respectively. The luminescent peak is between 2.7 and 3.0 eV with the excitation energies between 3.76 and 3.44 eV for both 12 and 20 days samples. However, the new luminescent peak is observed at near 2.5 eV for the 60 days samples, which may related with sulfur group. -- Highlights: • Strong photoluminescent fragment was separated from the silica spheres. • With this fragment detailed structural analysis becomes possible of the chromophore. • The UV–visible absorption shoulder appears at approximately 320 nm. • The fragments are R–CH3, R2–CH2, –C=O, –N=S=O, C–C, Si–O–Si, Si–O–C and Si–C. • New luminescence peak related with –SH appears for the 60 days sample