T. S. Kavetskyy

New Organic-Inorganic Hybrid Ureasil-Based Polymer Materials Studied by PALS and SEM Techniques

The new organic-inorganic materials, based on polyether chains covalently linked to a silica framework through urea bridges, referred as ureasilicates or ureasils, and semiconducting As2S3-ureasil composites are investigated using positron annihilation lifetime spectroscopy (PALS) and scanning electron microscopy (SEM) techniques. The results obtained show that incorporation of the As2S3 clusters into ureasil affects on the ortho-positronium (o-Ps) intensity or positronium formation probability and micro-/nanoscopic structure compared to the pure polymer, the effect is more essential as the loading fraction of As2S3 increases.

On the application of methods of positron annihilation spectroscopy for studying radiation-stimulated processes in chalcogenide glassy semiconductors

Unirradiated and γ-irradiated (average energy E = 1.25 MeV and dose Φ = 2.41 MGy) chalcogenide glassy semiconductors (CGSs) As2S3 and Ge15.8As21S63.2 are studied by positron annihilation lifetime spectroscopy (PALS) and Doppler broadening of the 0.511-MeV annihilation line (DBAL). Two 22Na positron sources with activities of 0.6 and 2.0 MBq and Kapton film thicknesses of 8.0 and 25.0 μm, respectively, are used. It is shown that radiation-induced changes in the PALS parameters of the CGS types under study are within measurement errors. The DBAL method appeared more efficient and accurate for studying radiation-stimulated processes in CGSs.

Impact of the sample thickness and γ-irradiation dose on the occurrence of radiation-induced optical effects in chalcogenide vitreous semiconductors of the Ge-Sb-S system

The impact of the sample thickness and γ-irradiation dose on the magnitude of total and static radiation-induced optical effects in chalcogenide vitreous semiconductors is studied using the example of Ge-Sb-S alloys of the Ge23.5Sb11.8S64.7 chemical composition. It is established that, at comparable ratios between the doses of γ-irradiation (Φ = 3.0 and 7.72 MGy) and thicknesses of the samples (d = 1.0 and 1.7 mm), the dose change more essentially affects the occurrence of radiation-induced optical effects in the semiconductors examined.

On the structural-optical correlations in radiation-modified chalcogenide glasses

In this work, we report our recent results on the y-irradiation-induced structural transformations in the Ge-Sb-S glasses as observed from the structural studies using high-energy synchrotron x-ray diffraction and extended x-ray absorption fine structure spectroscopy in comparison with the optical measurements using VIS/IR spectroscopy techniques. The structural-optical correlations in the radiation-induced effects are established. The structural changes upon irradiation are explained in the frames of the concept of coordination topological defects formation.

An overview application of silver nanoparticles in inhibition of herpes simplex virus

Abstract Nanoscale particles and molecules are a potential different for the treatment of disease because they have distinctive biologic property based on their structure and size, which is different from traditional small-molecule drugs. The antimicrobial mechanisms of silver nanoparticles include the formation of free radicals damaging the bacterial membranes, interactions with DNA, adhesion to cell surface altering the membrane properties, and enzyme damage. In this review, we focus on applications of silver nanoparticles in inhibition of herpes simplex virus.

Magnetic carbon nanotubes: preparation, physical properties, and applications in biomedicine

Abstract Magnetic carbon nanotubes (MCNTs) have been widely studied for their potential applications in medicine, diagnosis, cell biology, analytical chemistry, and environmental technology. Introduction of MCNTs paved the way for the emergence of new approaches in nanobiotechnology and biomedicine as a result of their multifarious properties embedded within either the carbon nanotubes (CNTs) or magnetic parts. Numerous preparation techniques exists for functionalizing CNTs with magnetic nanoparticles, and these versatile strategies lay the ground for the generation of novel and versatile systems which are applicable to many industries and biological areas. Here, we review and discuss the recent papers dealing with MCNTs and their application in biomedical and industrial fields.

High-dose boron and silver ion implantation into PMMA probed by slow positrons: Effects of carbonization and formation of metal nanoparticles

The Doppler broadening slow positron beam spectroscopy (SPBS) data for the previously observed effect of carbonization in high-dose (>1016 ion/cm2) 40 keV boron-ion-implanted polymethylmethacrylate (B:PMMA) and another one obtained for the effect of formation of metal nanoparticles in high-dose 30 keV silver-ion-implanted polymer (Ag:PMMA) are compared. Following to the Doppler broadening SPBS results, a difference in the high-dose ion-irradiation-induced processes in B:PMMA and Ag:PMMA is detected.

Nanovoids in Glasses and Polymers Probed by Positron Annihilation Lifetime Spectroscopy

Nanovoids in As2S3-based glasses (As2S3, (As2S3)85Ag15, and (As2S3)85(AgI)15), a polymer and a As2S3-polymer nanocomposite were studied using the positron annihilation lifetime spectroscopy (PALS) technique. After computer treatment of the PALS data recorded, it was found that only two components τ 1 (short-lived) near 0.2 ns and τ 2 (long-lived) near 0.4 ns are resolved for the As2S3-based glasses. At the same time, in the case of the polymer sample two components τ 2 near 0.3 ns and τ 3 (pick-off annihilation of ortho-positronium) near 2.8 ns were detected, while for the As2S3-polymer nanocomposite three components τ 1 near 0.2–0.3 ns, τ 2 near 0.4–0.5 ns and τ 3 near 2.4 ns were established. The volume of nanovoids in the materials studied was determined, and the fractional free volumes of the As2S3-polymer nanocomposite and the polymer matrix were compared. The results obtained are important to utilize As2S3-based glasses and polymer nanocomposites for advanced sensor applications.

The role of microRNAs and nanoparticles in ovarian cancer: a review

Abstract MicroRNAs (miRNAs) have had a revolutionary impact on cancer research over the recent years. They emerge as important players in tumourigenesis, leading to a paradigm shift in oncology. Ovarian cancer is the leading cause of death among gynaecologic malignancies. Therefore, there is a strong need for prognostic and predictive markers for early diagnosis which helps optimize and personalize treatment. Asymptomatically, ovarian cancer is often diagnosed at advanced and incurable stages. Efficient targeting and sustained release of miRNAs/anti-miRNAs using nanoparticles conjugated with antibodies and/or peptides could reduce the required therapeutic dosage while minimizing systemic and cellular toxicity. Given miRNAs importance in clinical oncology, here we focus on the development of miRNA nanoformulations to achieve enhanced cellular uptake, bioavailability and accumulation at the tumour site. Although many obstacles need to be overcome, miRNA therapy could be a powerful tool for ovarian cancer prevention and treatment. In this review, we discuss about the emerging roles of miRNAs in various aspects of ovarian cancer.

Carbonization in boron-ion-implanted polymethylmethacrylate as revealed from Raman spectroscopy and electrical measurements

ABSTRACT The results of Raman spectroscopy and electrical measurements of 40 keV boron-ion-implanted polymethylmethacrylate with ion doses from 6.25 × 1014 to 5.0 × 1016 ions/cm2 are reported for the first time. The Raman spectra recorded in the 400–3800 cm−1 range, showing the formation of new carbon–carbon bands for the as-implanted samples at higher ion doses (>1016 ions/cm2), are found to be an additional support for carbonization processes earlier revealed by slow positrons. The current–voltage dependences at 360 K testify also that the as-implanted samples examined with higher fluences (3.75 × 1016 and 5.0 × 1016 ions/cm2) have created a very thin conductive layer or conductive joints due to carbonization.