Laser-ablated silicon nanoparticles: optical properties and perspectives in optical coherence tomography

Abstract

Due to their biocompatibility silicon nanoparticles have high potential in biomedical applications, especially in optical diagnostics. In this paper we analyze properties of the silicon nanoparticles formed via laser ablation in water and study the possibility of their application as contrasting agents in optical coherence tomography (OCT). The nanoparticles suspension was produced by picosecond laser irradiation of monocrystalline silicon wafers in water. According to transmission electron microcopy analysis the silicon nanoparticles in the obtained suspension vary in size from 2 to 200 nm while concentration of the particles is estimated as 10 13 cm −3 . The optical properties of the suspension in the range from 400 to 1000 nm were studied by spectrophotometry measurements revealing a scattering coefficient of about 0.1 mm −1 and a scattering anisotropy factor in the range of 0.2-0.4. In OCT study a system with a central wavelength of 910 nm was employed. Potential of the silicon nanoparticles as a contrasting agent for OCT is studied in experiments with agarose gel phantoms. Topical application of the nanoparticles suspension allowed the obtaining of the contrast of structural features of phantom up to 14 dB in the OCT image.

On the synthesis and characterisation of luminescent hybrid particles: Mo6 metal cluster complex/SiO2

“…4): deshielding of the Q3-type signal (i.e., Si-OH) by about 2 ppm and the increase in Q4/Q3 ratio. The change in the chemical environment of Si in the Q3-type can be explained by formation of hydrogen bonds between Si-OH and Mo-OH or Mo-OH 2 , while increased intensity of the Q4 signal is likely the result of Si-O-Mo bond formation, which is in agreement with earlier 29 Si NMR data of doped silica materials. [26][27][28] The UV/Vis diffuse reectance spectra of SMPs ( Fig.…”

“…All chemical reagents were of analytical grade. 29 For emission measurements in solid state, powdered samples of compounds 1, 2 and 3, n x @SiO 2 (both SMPs and SNPs) and An and B2 were placed between two non-uorescent glass plates. The measurements were carried out at 298 K. The samples were excited by 355 nm laser pulses (6 ns duration, LOTIS TII, LS-2137/3).…”

“…These observations signify that as metal-cluster complex loading increases above x ¼ 0.1, the value z in the formula [{Mo 6 X 8 }(H 2 O) 6ÀyÀz (OH) y (OSi) z ] 4ÀyÀz tends to 0. 29 Si CP MAS NMR of 3 0.1 @SiO 2 , that is, the sample with the borderline content of the metal cluster complex, showed two noticeable changes in comparison to neat SiO 2 SMPs (Fig. 4): deshielding of the Q3-type signal (i.e., Si-OH) by about 2 ppm and the increase in Q4/Q3 ratio.…”

High‐Aspect‐Ratio Plasmonic Heterostructures for In Vivo Enhanced Optical Coherence Tomography Imaging in the Second Near‐Infrared Biological Window

“…A widely proposed method for overcoming this issue is the incorporation of contrast agents that can enhance optical scattering signals. Over the past few decades, although they are still in the laboratory stage of development, various materials and structures have been explored as promising contrast agents for OCT imaging, such as microbubbles, [ 13 ] carbon nanotubes, [ 14 ] magnetic nanoparticles, [ 15 ] glycerol, propylene glycol, [ 16 ] silicon nanoparticles, [ 17 ] metallic nanostructures, [ 18,19 ] fluorescent agents (e.g., indocyanine green), [ 20 ] and photosensitive proteins (e.g., phytochrome) [ 21 ] (Table S1, Supporting Information). However, most of these agents only operate in the NIR‐I window, or provide relatively small optical scattering cross‐sections in the NIR‐II window, which limits the enhancement of OCT contrast, particularly for in vivo applications.…”

Анализ Структуры Наночастиц, Формируемых Методом Лазерной Абляции Пористого Кремния И Микрочастиц Кремния В Воде

“…Таким образом, размеры сформированных КНЧ во всех трех рассмотренных случаях превышают 50 nm. В то же время при абляции монокристаллического кремния при аналогичных условиях эксперимента в суспензии КНЧ присутствует фракция наночастиц размером 2−40 nm [11,12], что свидетельствует о более высокой эффективности агломерации продуктов абляции в КНЧ при облучении пористого и механически измельченного кремния, чем в случае кристаллической мишени из данного материала, и согласуется со сделанными выше заключениями об увеличении выхода продуктов абляции в рассматриваемых случаях абляции нано-и микроструктурированного кремния [6,9]. Несмотря на относительно большие размеры получившихся в настоящей работе КНЧ для внедрения внутрь биотканей, такой класс частиц, согласно нашим предыдущим расчетам и экспериментальным исследованиям [11], обладает более высокими значениями коэффициента рассеяния света по сравнению с частицами меньшего размера и имеет высокий потенциал для использования в качестве контрастирующих агентов для визуализации поверхностей биологических объектов методом оптической когерентной томографии.…”