Silicon Nanoparticles Formed via Pulsed Laser Ablation of Porous Silicon in Liquids
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n Nanoparticles Formed via Pulsed Laser Ablation of Porous Silicon in Liquids A. V. Skobelkinaa*, F. V. Kashaeva, A. V. Kolchina, D. V. Shuleikoa, T. P. Kaminskayaa, D. E. Presnova,b,c, L. V. Golovana, and P. K. Kashkarova,d a Faculty
b
of Physics, Moscow State University, Moscow, 119991 Russia Skobeltsyn Research Institute of Nuclear Physics, Moscow State University, Moscow, 119991 Russia c Center of Quantum Technologies, Moscow State University, Moscow, 119991 Russia d National Research Center “Kurchatov Institute,” Moscow, 123182 Russia *e-mail: [email protected] Received March 26, 2020; revised March 26, 2020; accepted April 10, 2020
Abstract—Picosecond pulsed laser ablation of meso- and microporous silicon layers in water and ethanol leads to the formation of nanosilicon suspensions with particle diameters below 100 nm. It is established that the use of porous silicon targets allows the laser ablation threshold to be reduced and the nanoparticle concentration increased as compared to the ablation of crystalline silicon. Keywords: pulsed laser ablation, porous silicon, atomic force microscopy, ablation threshold. DOI: 10.1134/S1063785020070263
In recent years, much effort has been devoted to the application of silicon nanoparticles (Si-NPs) to solving various biomedical problems [1–3]. This interest in Si-NPs is related to their high biocompatibility, biodegradability, and low toxicity. For effective introduction into biological tissues, particle sizes must be below 100 nm. Existing methods of mechanical of ultrasonic comminution, which are traditionally applied to porous (por-Si) and single-crystalline silicon (c-Si) cannot meet this requirement [4]. At the same time, the task of obtaining NPs with diameters below 100 nm can be solved by means of pulsed laser ablation in a liquid medium, and the obtained Si-NP suspensions have proved to be chemically pure [3]. However, the yield of reaction product from this process is rather low, which hinders the use of such SiNPs in view of their low concentration in the suspension. To eliminate this disadvantage, it is possible to form Si-NPs by laser ablation of porous silicon (porSi), a nanocomposite medium comprising silicon nanocrystals separated by nanopores [5], which can be obtained be electrochemical etching of c-Si wafers in an appropriate electrolyte. Depending on the properties of the initial c-Si wafers and electrolyte, this treatment leads to the formation of a layer of either microporous silicon (micropor-Si) with sizes of both pores and nanocrystals not exceeding 10 nm or mesoporous silicon (mesopor-Si) with sizes of both pores and nanocrystals within 10–50 nm. A two-stage process involving (i) formation of a porous layer by electrochemical etching of c-Si and (ii)
subsequent laser ablation of obtained por-Si yields Si-NPs that are highly requested in various biomedical applications [6]. These include photoluminescent labels [6], contrast agents in optical coherent tomography [7], and photosensitizers of singlet oxygen in photodynamic therapy [7]. How
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