We herein present pioneering studies to reveal that excitation-wavelength-dependent photoluminescence properties of fluorescent silicon nanoparticles (SiNPs) can be realized by rationally designing surface ligands, i.e., several kinds of oxidized indole derivatives. The resultant ligand-decorated SiNPs exhibit strong fluorescence, with significant excitation-wavelength-dependent emissive shifting from ∼420 nm to ∼550 nm. Taking advantage of their unique optical merits, we further exploit the resultant ligand-decorated SiNPs as novel fluorescent labels for anti-counterfeiting and cell imaging.