The fluorescenttrans-styrylbenzene with an aldehyde moiety as the biding site, (E)-4-styrylbenzaldehyde, was synthesized and the chemical structure was measured by H-1 nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The capability of the molecule as a chemosensor for aniline and 4-nitroaniline was examined using FTIR spectroscopy and fluorescence spectroscopy. Both aniline and 4-nitroaniline formed imine groups by a reaction with (E)-4-styrylbenzaldehyde. On the other hand, the (E)-4-styrylbenzaldehyde molecule recognized only 4-nitroaniline with high selectivity. Silica nanoparticles (SNPs), which have fluorescenttrans-styrylbenzene with the aldehyde moiety on the surface, SBA-SNP, was prepared using a modified Stober synthetic method. The prepared SBA-SNP was characterized by field emission scanning electron microscopy, FTIR spectroscopy, and fluorescence spectroscopy. The SBA-SNP had a spherical shape with a mean diameter of 150 nm. The SBA-SNP recognized only the 4-nitroaniline molecule with high selectivity through fluorescence quenching in emission, and the pale green fluorescence color disappeared with increasing concentration of 4-nitroaniline.