Laser fragmentation of silicon microparticles in liquids for solution of biophotonics problems

Abstract

The possibility of manufacturing silicon nanoparticles by picosecond laser fragmentation of silicon microparticles in water is analysed. It is shown that for fragmentation duration of 40 min, the dependence of the average sizes of particles on the initial mass concentration of the micropowder varied in the range of 0.5–12 mg mL-1 is nonmonotonic, with the maximum average size of 165 nm being achieved at a concentration of 5 mg mL-1. To explain the obtained result, the simulation of propagation of a focused laser beam in a scattering suspension of silicon microparticles is performed for their different mass concentrations. It is demonstrated that at concentrations not exceeding 5 mg mL-1, fragmentation occurs in the paraxial region of the beam when it propagates deep into the cuvette with a suspension, while at higher concentrations it occurs primarily in the superficial layer owing to strong extinction. Calculations results allow the experimental features of the formation of silicon nanoparticles to be explained. Spectrophotometry measurements on suspensions of nanoparticles obtained at the initial concentration of microparticles of 12 mg mL-1 are compared with the theoretical estimates of the absorption and scattering coefficients obtained in the framework of the Mie theory. Measured optical properties indicate the potential of using fragmented nanoparticles as scattering and/or absorbing contrast agents in optical imaging of biological objects.

Photomechanical Laser Fragmentation of IrO2 Microparticles for the Synthesis of Active and Redox‐Sensitive Colloidal Nanoclusters

“…Consequently, MP‐LFL with ps‐laser pulses has been successfully applied to generate NPs from various materials in the past. Silicon NPs were produced in a fixed ablation chamber, [ 31 ] while the fabrication of aluminum, [ 35 ] zinc oxide, [ 29 ] and boron carbide [ 29 ] NPs utilized a liquid jet setup. Here, the liquid jet setup has the significant advantage of precise control of the energy delivered to the MP educt.…”

“…[24,25] While the mechanisms, application potential, and scalability of LAL and NP-LFL have been thoroughly investigated, [2,26,27] the use of microparticles (MPs) in the LFL process remains limited to individual applicatory studies. [28][29][30][31] Compared with LAL, where complex and expensive beam-guiding methods are required, [15] MP-LFL can be performed relatively simply and cost-efficient in a liquid jet containing the MP educts. While, e.g., metals, are readily available in bulk form, many oxides are produced in microparticulate form, predestined for MP-LFL, and thus require additional pressing and heat treatment to be viable for LAL.…”

“…[29] However, up to date, the MP-LFL mechanism has been poorly investigated, and only a couple of specialized studies exist that exclusively focus on the photothermal aspect. [31,36] Yet, to scale the MP-LFL process and identify optimal processing conditions that lead to high productivity of surfactant-free, pure, colloidal NPs with targeted nanoparticle sizes, the laser-induced fragmentation mechanism of microparticles leading to size reduction and the formation of product NPs in MP-LFL are still unknown.…”

“…[ 29 ] While the concentration of the initial MP influences the scattering and absorption of the incident laser pulse within the liquid, an impact on the final NP size distribution was also shown. [ 31 ]…”

“…[29] While the concentration of the initial MP influences the scattering and absorption of the incident laser pulse within the liquid, an impact on the final NP size distribution was also shown. [31] From a mechanistic standpoint, it has been proposed that, photothermal and photomechanical processes play a role in MP-LFL. [29,36] In fact, the importance of photomechanical processes under stress confinement has been highlighted for the interaction of laser pulses with organic microparticles.…”