Silicon nanoparticle-based near-infrared surface enhanced fluorescence without any “dielectric spacer”

Abstract

For the first time, herein, we report the theoretical investigation on silicon (Si) nanoparticle-based near-infrared (NIR) surface-enhanced fluorescence (SEF). Initially, the scattering spectra of single spherical-shaped Si nanoparticles of different sizes are plotted and characterized all the observed modes using the multipolar decomposition method. Later, the electric field intensity enhancement (EFIE) distribution inside and outside Si nanoparticles is plotted at the wavelengths of electric and magnetic type modes. Finally, the SEF enhancement (χSEF) is estimated by varying the excitation wavelength (λex), fluorescence wavelength (λem), and separation (d) between the fluorophore and Si nanoparticle of different sizes. The χSEF is found to vary from 1 to 3 orders of magnitude when the λem falls in the NIR region. In contrast to the plasmonic or metal nanoparticle-based SEF, the maximum χSEF is observed when d = 0. This indicates that the thin dielectric spacers between the fluorophores and Si nanoparticles are not required to obtain the enhancement in the case of the Si nanoparticle-based SEF technique. This can be considered as a significant advantage over the conventional metal nanoparticle-based SEF, where dielectric spacers are mandatory. Finally, the average SEF enhancement ⟨χSEF⟩ is also estimated.