Blue luminescent silicon nanoparticles synthesized from free-standing porous silicon layer by ultrasonic treatment

•Blue luminescent colloidal Si NPs were generated for low dimensional microelectronic/photonic device applications.•Spherical, crystalline and finely distributed Si NPs of around 5 nm were synthesized in solution.•Crystalline lattice fringes with spacing of 0.34 nm corresponding to Si (1 1 1) planes are seen in HRTEM.•Asymmetry of Raman peaks and their red shift confirm the successful generation of Si NPs.•PL peak towards bluer region implies smaller size Si NPs consistent with energy band gap calculations.

Blue luminescent silicon nanoparticles (Si NPs) have been synthesized by using free standing porous silicon (FS-pSi) layer as a seed material. Transmission electron microscopy measurements confirm the generation of spherical nanoparticles with average size of about ∼5 nm. The crystalline nature of Si NPs was confirmed by selective area electron diffraction. The observed asymmetry and shift of Raman peaks with respect to bulk silicon further confirm the successful generation of Si NPs. The observed photoluminescence (PL) (at ∼447 nm) and the chromaticity diagram fall in the blue region. It matches with energy bandgap of SiNPs (∼2.85 eV) estimated by UV–VIS–NIR spectroscopy. This is an easy and versatile approach for generating high densities of Si NPs for possible use in micro and optoelectronic applications.