Post-Treatment of Silicon Nanocrystals Produced by Ultra-Short Pulsed Laser Ablation in Liquid: Toward Blue Luminescent Nanocrystal Generation

Abstract

Blue luminescent colloidal silicon nanocrystals (Si-NCs) were produced in a two-stage process. In the first step, synthesis of Si-NCs was achieved by femtosecond pulsed laser ablation of a silicon wafer, which was immersed in deionized water. The size and the structural and the chemical characteristics of colloidal Si-NCs were investigated by TEM and EDAX analyses, and it is found out that the Si-NCs are in spherical shape and the particle diameters are in the range of 5−100 nm. In the second step, ultrasonic waves and filtering chemical-free post-treatment of colloidal Si-NCs solution was performed to reduce the particle size. High-resolution TEM (HRTEM) studies on post-treated colloidal solution clearly show that small (1−5.5 nm in diameter) Si-NCs were successfully produced. Raman spectroscopy results clearly confirms the generation of Si nanoparticles in the crystalline nature, and the Raman scattering study of post-treated Si-NCs confirms the reduction of the particle size. The UV−vis absorption and photoluminescence (PL) spectroscopy studies elucidate the quantum confinement effect of Si-NCs on the optical properties. The colloidal Si-NCs and post-treated Si-NCs solutions present strong absorption edge shifts toward UV region. Broadband PL emission behavior is observed for the initial colloidal Si-NCs, and the PL spectrum of post-treated Si-NCs presents a blue-shifted broadband PL emission behavior due to the particle size reduction effect.

Luminescent silicon nanocrystals produced by near-infrared nanosecond pulsed laser ablation in water

“…The slow 2.7 eV band is associated with a forbidden triplet-to-singlet transition, its excitation being due to an intersystem crossing between the excited singlet and triplet states. We acknowledge that in previous experiments on LA of Si in water, a blue emission is observed under several excitation energies in the UV range and it is ascribed to QC in Si-NC [11,13,14]. It is worth noting that these excitation features differ from those here evidenced (a bell-shaped band peaked at 5.0 eV).…”

“…To this purpose, laser ablation (LA) in liquids is particularly promising since it provides effective control parameters (laser photon energy, fluence, pulse duration, liquid reactivity) for the morphology and the structure of related products and, therefore, it has attracted much attention [6][7][8][9][10]. Previous works have demonstrated the viability of a green method to produce Si-nanocrystals (Si-NCs) by LA in water, and have addressed their luminescence properties [11][12][13][14]. Recently, it has also been achieved the bio-functionalization of LA induced Si-NCs thus opening the way to useful applications such as fluorescence imaging or drug delivery [15,16].…”

Photoluminescent electrospun polymeric nanofibers incorporating germanium nanocrystals

“…Another very promising solution for nanocrystals generation consists of using laser ablation method [38]. The use of unique scientific facilities of laser-matter interaction properties opens the doors to the generation of wide variety of metal nanoparticles and SC-NCs by using pulsed laser ablation [39,40]. Laser ablation, especially in liquids, is a versatile method of generating colloidal, highly pure and agent-free nanocrystals.…”

Low power zinc-oxide based charge trapping memory with embedded silicon nanoparticles via poole-frenkel hole emission

“…Next, Si-NPs of predominately 2 nm in size (ranging from 1 to 5.5 nm) were synthesized by performing sonification at 40 KHz for 200 min then filtration of the NPs colloidal using filters with a pore size of 100 nm. 11 A TEM image of the synthesized ultra-small non-agglomerate Si NPs is depicted in Fig. 1.…”