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11LD-I-7
Raman spectroscopy and spectrophotometry studies of silicon nanoparticles for biophotonics
S. Zabotnov1, A. Kolchin1, A. Pavlikov1, F. Kashaev1, D. Kurakina2, A. Khilov2, P. Agrba3, M. Kirillin2, L. Golovan1, P. Kashkarov1
1Lomonosov Moscow State University, Faculty of Physics, Moscow, Russian Federation 2Institute of Applied Physics RAS, Laboratory of Biophotonics, Nizhny Novgorod, Russian Federation
3Lobachevsky State University of Nizhny Novgorod, Faculty of Radiophysics, Nizhny Novgorod, Russian Federation
Nowadays silicon nanoparticles (Si-NPs) produced by mechanical grinding of porous silicon are efficiently used in bioimaging and therapeutic applications [1,2]. We suggest employing an alternative technique consisting in pulsed laser ablation in liquids (PLAL) to fabricate small and chemically pure Si-NPs for biomedical applications.
Pico- and femtosecond laser radiation was used to form the Si-NPs via PLAL from porous silicon targets. In our experiments the Si-NPs are fabricated in water, ethanol and liquid nitrogen and characterized by sizes smaller than 100 nm. Raman spectroscopy revealed a presence of the lines for crystalline (520 cm-1) and amorphous (480 cm-1) silicon phases (Fig.1a). An analysis of the ratio of these lines integral intensities indicated that the volume fraction of the crystalline particles is higher than 87% for all types of the studied samples.
Fig. 1. Raman spectrum for Si-NPs ablated in water for excitation at 632 nm (a) and scattering coefficient spectrum
for Si-NPs ablated in liquid nitrogen (b).
Spectrophotometry measurements of the ablated Si-NPs suspensions revealed that scattering coefficient value reaches up to 0.3 mm-1 in the spectral range of 400 - 1000 nm (Fig.1b as example).
Optical coherence tomography imaging of the suspensions drops administered on agar gel surfaces indicated high efficiency of the Si-NPs as contrast agents providing the contrast up to 30 dB. Thus, the perspectives of the Si-NPs formed via PLAL in optical imaging are demonstrated. This work was supported by the Russian Science Foundation (project № 19-12-00192).
References
[1] O.I. Ksenofontova, A.V. Vasin, V.V. Egorov, et al., Tech. Phys. 59, 66 - 77 (2014).
[2] V. Stojanovic, F. Cunin, J.O. Durand, et al., J. Mater. Chem. B 4, 7050 - 7059 (2016).
