Marina Romanova

Electron Emission Standed Nanodosimetry and Gas Detection

Photoelectron (PE) and thermostimulated exoelectron (TE) emission spectroscopies were explored for gas sensing and electron radiation nanodosimetry. Silicon substrates were in use as the working matter for benzene and isopentane sensing. PbS nanocrystals embedded in ZrO2 thin-films were employed to absorb electron radiation. Both PE and TE influenced by gas absorption and radiation deliver promising approaches for gas sensing and nanodosimetry.

Influence of Ultraviolet and Electron Radiation on Photoelectron Emission Spectra of Lead Sulfide Nanoparticles Embedded in a Matrix of Zirconium Oxide

Lead sulfide (PbS) nanoparticles embedded in a thin-film matrix of zirconium oxide (ZrO2), ZrO2:PbS nanofilms, were studied for application in nanodosimetry of ionizing radiation. Readout of the delivered dose was carried out by measurements of photoelectron emission (PE) current from ZrO2:PbS nanofilms. PE emission was excited by UV photons having energy of 4.6-6.2 eV. First, the nanofilms were irradiated with non-ionizing UV radiation used as a model of ionizing radiation in order to extract exposure-dependent signal from PE spectra of ZrO2:PbS nanofilms. It was found that exposure-dependent signal is provided by PbS nanoparticles and it is the decrease of the increment of PE current calculated in energy range of 4.9-5.5 eV. The extracted signal was further analyzed by irradiating ZrO2:PbS nanofilms with 9 MeV electron radiation. Second degree polynomial relationship was observed between the decrease of the increment of PE spectra calculated in the energy range of 4.9-5.5 eV and dose of electron radiation in the range of 0-10 Gy. Error of dose measurement was calculated for each delivered dose. Error of dose measurement decreases from 65% to 11% when the delivered dose increases from 2 Gy to 5 Gy and doesn’t exceed 11% in the dose range of 5-10 Gy. Changes in PE spectra of ZrO2:PbS nanofilms under influence of electron radiation suggest that the nanofilms have potential to be used in nanodosimetry of ionizing radiation; however, further adjustment of the method is required to reduce dose measurement error.

Influence of Ultraviolet Radiation on Surface Electric Potential of P(VDF-TrFE) Films

Ultraviolet (UV) radiation is able to cause biological changes at the cellular and molecular level. To study biological effects of UV radiation, UV detector is required. 10 monolayer thick ferroelectric P(VDF-TrFE) films consisting of 70% vinylidene fluoride (VDF) and 30% trifluoroethylene (TrFE), or P(VDF-TrFE 70:30), were investigated as a possible material of UV detector. The films were deposited on a glass substrate using Langmuir-Blodgett technique. Changes in surface electric potential of P(VDF-TrFE 70:30) films under influence of UV radiation were investigated by Kelvin force microscopy. A hypothesis was proposed that UV radiation was well absorbed by the glass substrate changing its surface charge. This charge in turn changed polarization of P(VDF-TrFE 70:30) film leading to changes in its surface electric potential. It was found that after 6 minutes of UV irradiation surface electric potential of P(VDF-TrFE 70:30) films decreased and no changes were observed further increasing irradiation time. However, surface electric potential of the bare glass substrate continued to decrease increasing irradiation time. It was also found that surface electric potential of P(VDF-TrFE 70:30) films relaxed to its initial value within half an hour after the irradiation was stopped. The relaxation obeyed exponential law. The study suggests that P(VDF-TrFE 70:30) films deposited on the glass substrate are sensitive to UV radiation and might be able to serve as a material for an UV dosimeter, however, further studies are required.

Influence of ultraviolet radiation on surface electric potential of P(VDF-TrFE) films

Ultraviolet (UV) radiation is able to cause biological changes at the cellular and molecular level. To study biological effects of UV radiation, UV detector is required. 10 monolayer thick ferroelectric P(VDF-TrFE) films consisting of 70% vinylidene fluoride (VDF) and 30% trifluoroethylene (TrFE), or P(VDF-TrFE 70:30), were investigated as a possible material of UV detector. The films were deposited on a glass substrate using Langmuir-Blodgett technique. Changes in surface electric potential of P(VDF-TrFE 70:30) films under influence of UV radiation were investigated by Kelvin force microscopy. A hypothesis was proposed that UV radiation was well absorbed by the glass substrate changing its surface charge. This charge in turn changed polarization of P(VDF-TrFE 70:30) film leading to changes in its surface electric potential. It was found that after 6 minutes of UV irradiation surface electric potential of P(VDF-TrFE 70:30) films decreased and no changes were observed further increasing irradiation time. However, surface electric potential of the bare glass substrate continued to decrease increasing irradiation time. It was also found that surface electric potential of P(VDF-TrFE 70:30) films relaxed to its initial value within half an hour after the irradiation was stopped. The relaxation obeyed exponential law. The study suggests that P(VDF-TrFE 70:30) films deposited on the glass substrate are sensitive to UV radiation and might be able to serve as a material for an UV dosimeter, however, further studies are required.

Inorganic Nanoparticle as a Carrier for Hepatitis B Viral Capsids

Virus like particles (VLP) are used to transport immune response-modulating agents to target cells to treat them. In order to deliver a high concentration of VLP to the cell, a number of VLP can be attached to a nanoparticle to be used as a nanolorry. In this study, SiO2 nanoparticles were attached to Hepatitis B VLP. Spectrophotometry measurements, electron, and fluorescent microscopy evidence showed that the SiO2 – Hepatitis B VLP complexes were formed.