arXiv subjects

Joanna Borowiec

Publications and source records attributed to Joanna Borowiec.

3 recordsLinked to original sources

arXiv2024

Inverse Diffusion Approximation for Extraction of Scattering and Absorption Coefficients in Highly Scattering Media

Photon transport through a diffusing slab can be described by the radiative transfer equation (RTE). When the slab is highly scattering and weakly absorbing, the RTE simplifies to the diffusion equation. In this paper, an inverse diffusion approximation (IDA) method is numerically developed to determine the optical properties (reduced scattering $μ'_s$ and absorption coefficient $μ_a$) of a homogeneous slab using simple reflectance and transmission measurements with a spectrometer. The reflectance and transmission of a diffusing slab with an arbitrary thickness can then be predicted by solving the forward problem by using the calculated $μ'_s$ and $μ_a$. Our method is validated both numerically, by directly comparing with Monte-Carlo simulations, and experimentally, by comparing with measurements on ZnO/PDMS and TiO$_2$/PDMS composite polymer films with varying thicknesses. The IDA method is also applied to distinguish between different types of tissue. Overall, our method could be used to guide the design of radiative cooling reflectors, or lighting and optical display diffusers for applications in medical imaging and other fields.

physics.optics↗

arXiv2023

Ordered Arrays of Gold Nanoparticles Crosslinked by Dithioacetate Linkers for Molecular devices

The final performance of a molecular electronic device is determined by the chemical structure of the molecular wires used in its assembly. Molecular place-exchange was used to incorporate di-thioacetate terminated molecules into ordered arrays of dodecanethiol capped gold nanoparticles. X-ray photoelectron spectroscopy confirmed successful molecular replacement. Room-temperature molecular conductance of a statistically large number of devices reveals that conductance is enhanced by up to two orders of magnitude for the di-thioacetate terminated molecules. Density functional theory transport calculations were performed on five different configurations of the di-thioacetate molecules between gold electrodes, and the calculated average conductance values are in good agreement with the conductance experimentally-observed trend. Our findings highlight important cooperative effects of bridging neighboring gold nanoparticles and choice of appropriate molecular wires when designing devices for efficient transport.

cond-mat.mtrl-sci↗

arXiv2022

Scalable Organic Semiconductor Neutron Detectors

A long-standing limitation of semiconductor neutron detectors is the lack of a scalable solution to make large area instruments. Neutron detectors are used in a wide range of applications, including the nuclear industry, safeguarding radioactive material, neutron imaging, non-destructive testing, understanding space weather effects on commercial electronics used in aviation, and for fundamental science such as nuclear and particle physics. Here we demonstrate that a solution processed organic semiconductor technology, which is scalable, can solve this aproblem. We have demonstrated detection of fast neutrons from monoenergetic beams (energies 0.565 and 16.5 MeV), from AmBe sources, and thermal energy (0.025 eV) in devices sensitised with B-10 enriched B_4C. This energy range is of interest for many of the applications listed above. The detector response is found to be linear with flux up to 1.5 x 10^7 n/cm^2/s. As organic semiconductors are a similar density to human tissue, this technology may be of interest for medical physics applications, for example B neutron capture therapy dose monitoring and understanding neutron interactions in human tissue.

physics.ins-det↗