Silicon nanoparticles with iron impurities for multifunctional applications

Abstract

Crystalline silicon (Si) nanoparticles (NPs) doped with iron (Fe) in the range from 0.02 to 2.5 at.% were prepared by plasma-ablative synthesis and were investigated by means of the transmission electron microscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), infrared spectroscopy and nuclear magnetic resonance relaxometry. While the nanocrystal size in Si:Fe NPs did not depend significantly on Fe content, the hydrodynamic diameter of NPs in aqueous suspensions increases from 50 to 180[Formula: see text]nm. Both the transverse and longitudinal proton relaxation time were found to decrease in the prepared suspensions of Si:Fe NPs. Maximal shortening of the transverse relaxion was observed for Si:Fe NPs with 0.2 at.% of Fe and the relaxation rate was almost linearly proportional to the NP concentration. Both these findings and in vivo tests indicate that Si:Fe NPs are promising for biomedical applications in magnetic resonance imaging (MRI) and therapy of cancer.

Spin-Dependent Phenomena in Semiconductor Micro-and Nanoparticles—From Fundamentals to Applications

“…While the intratumoral injection induces the stronger antitumor effect, the observed decrease in tumor volume after intravenous administration confirms accumulation of Si NPs in the tumor due to as-called enhanced permeability and retention effect, which is well known for various NPs [105]. It was found that the antitumor effect of iron-doped Si NPs correlate with lifetime of laboratory animals [103]. Figure 42 shows temporal dependences of the number of mice with cancer tumor after intravenous and intratumoral administration of NPs.…”

“…As for the second line of intrinsic Si DBs they are supposed to be localized in SiO 2 surface coating of the NP surfaces, which was confirmed by X-ray photoelectron spectroscopy and FTIR measurements [101]. Furthermore, HR-TEM images of iron doped Si NPs reveal numerous defects of the crystalline structure as twins and grain boundaries related to the fast cooling rate during their formation in argon flow [103]. Both the iron impurities and intrinsic defects as Si DBs are responsible for the large number of electron spin centers in such NPs [101,103].…”

“…Furthermore, HR-TEM images of iron doped Si NPs reveal numerous defects of the crystalline structure as twins and grain boundaries related to the fast cooling rate during their formation in argon flow [103]. Both the iron impurities and intrinsic defects as Si DBs are responsible for the large number of electron spin centers in such NPs [101,103]. The total concentration of electron spin centers in Si NPs approaches 10 18 spin/g [101] that makes this type of NPs to be efficient for shortening the proton spin relaxation in aqueous media as it was already demonstrated for porous Si NPs (see Figure 36).…”

“…Besides the MRI diagnostic modality, it was recently demonstrated the possibility to use Si NPs with iron impurities to suppress the cancer tumor growth in vivo [103]. The intratumoral injection and intravenous administration of iron-doped Si NPs resulted in a decrease of the tumor volume by 32% and 23%, respectively.…”

“…The average lifetime of laboratory animals of the experimental group was about 30% longer than for the control one. The observed antitumor effect of iron-doped Si NPs can be related to dissolution of Si NPs accumulated in tumor followed with release of iron ions, which induce reactive oxygen species with high toxicity for cancer cells [103]. Moreover, aqueous suspensions of Si NPs were explored as efficient sensitizers of electromagnetic radiofrequency (RF) hyperthermia, which is a prospective approach for mild cancer therapy with non-magnetic Si NPs.…”