Laser-synthesized oxide-passivated bright Si quantum dots for bioimaging

Abstract

Crystalline silicon (Si) nanoparticles present an extremely promising object for bioimaging based on photoluminescence (PL) in the visible and near-infrared spectral regions, but their efficient PL emission in aqueous suspension is typically observed after wet chemistry procedures leading to residual toxicity issues. Here, we introduce ultrapure laser-synthesized Si-based quantum dots (QDs), which are water-dispersible and exhibit bright exciton PL in the window of relative tissue transparency near 800 nm. Based on the laser ablation of crystalline Si targets in gaseous helium, followed by ultrasound-assisted dispersion of the deposited films in physiological saline, the proposed method avoids any toxic by-products during the synthesis. We demonstrate efficient contrast of the Si QDs in living cells by following the exciton PL. We also show that the prepared QDs do not provoke any cytoxicity effects while penetrating into the cells and efficiently accumulating near the cell membrane and in the cytoplasm. Combined with the possibility of enabling parallel therapeutic channels, ultrapure laser-synthesized Si nanostructures present unique object for cancer theranostic applications.

Numerical Investigation of Ultrashort Laser-Ablative Synthesis of Metal Nanoparticles in Liquids Using the Atomistic-Continuum Model

“…Pulsed laser ablation has emerged as a powerful technique for the synthesis of nanoparticles, which profits from a natural production of nanoclusters during laser-materials interaction [1,2]. When ablated in gaseous ambient, the nanoclusters can be deposited on a substrate to form a thin nanostructured film [3][4][5][6][7][8][9], while ablation in a water environment leads to the formation of a colloidal nanoparticle solution [10][11][12][13][14][15][16][17][18]. Such a synthesis can lead to exceptional purity of formed nanomaterials, while their properties are often unique and not reproducible by conventional chemical methods.…”

Bi‐Modal Nonlinear Optical Contrast from Si Nanoparticles for Cancer Theranostics

“…Having negligible toxicity compared to quantum dots based on compound semiconductors and being capable of providing efficient imaging and therapeutic functionalities based on its unique physicochemical characteristics, nanosilicon occupies a particularly important niche related to biological applications. The imaging functionality of nanosilicon typically employs photoluminescence (PL) of quantum‐confined excitonic states in silicon (Si) nanocrystals (NCs) with sizes smaller than the exciton Bohr's radius (≈5 nm for the bulk crystalline Si (c‐Si)), which enables tracking the presence of Si nanoparticles (NPs) in cells or tissues . On the other hand, Si NPs can serve as efficient sensitizers of local heating under external stimuli to initiate hyperthermia‐based therapies.…”

“…Similar large NP sizes look much more preferable to ensure good transport of NPs in vivo and time‐delayed dissolution, conditioning a prolonged circulation of the NPs in the blood stream . However, such large sizes are not consistent with quantum confinement mechanism for the generation of efficient PL for imaging, while extrinsic PL bands related to silicon oxide coatings (blue and blue‐green) are not very strong and overlap with auto‐fluorescence bands of many proteins …”

Preparation of Silcon Nanoparticles and Films By Pulsed Laser Deposition

“…A method of the pulsed lased deposition under ablation of a solid target in inert gas atmosphere allows us to control both the morphology and photoluminescent properties of Si NPs [2]. Laser-ablated Si NPs are dispersible in aqueous media and they can act as PL labels in bioimaging [3]. Our present work is devoted to a search of the optimal conditions to prepare Si NPs by using laser ablation of solid targets in inert gas atmosphere.…”