Deep tissue imaging with acousto-optical tomography and spectral hole burning with slow light effect: a theoretical study

Biological tissue is a highly scattering medium that prevents deep imaging of light. For medical applications, optical imaging offers a molecular sensitivity that would be beneficial for diagnosing and monitoring of diseases. Acousto-optical tomography has the molecular sensitivity of optical imaging with the resolution of ultrasound and has the potential for deep tissue imaging. Here, we present a theoretical study of a system that combines acousto-optical tomography and slow light spectral filters created using spectral hole burning methods. Using Monte Carlo simulations, a model to obtain the contrast-to-noise ratio (CNR) deep in biological tissue was developed. The simulations show a CNR  >  1 for imaging depths of ∼5  cm in a reflection mode setup, as well as, imaging through ∼12 cm in transmission mode setups. These results are promising and form the basis for future experimental studies

On the correlation between dye coverage and photoelectrochemical performance in dye-sensitized solar cells

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/)Concentration depth profiles of the ruthenium based dyes Z907 and N719 adsorbed onto titania are measured directly and used for determining the adsorption isotherm of the dyes. Dye layers formed by both grow in islands on the titania which do not cover the entire titania surface even at the maximum coverage. Impedance spectroscopy in conjunction with the adsorption isotherms shows that recombination losses mainly appear between the dye and the electrolyte solution. The short circuit current and the efficiency increase linearly with the dye coverage. The open circuit voltage slightly increases with increasing dye coverage which is interpreted as most likely to be a consequence of the higher charge in the particles upon higher dye loading on the TiO2 surface

Factors influencing the catalytic oxidation of benzyl alcohol using supported phosphine-capped gold nanoparticles

Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Two phosphine-stabilised gold clusters, Au101(PPh3)21Cl5 and Au9(PPh3)8(NO3)3, were deposited and activated on anatase TiO2 and fumed SiO2. These catalysts showed an almost complete oxidation of benzyl alcohol (>90%) within 3 hours at 80 °C and 3 bar O2 in methanol with a high substrate-to-metal molar ratio of 5800 and turn-over frequency of 0.65 s−1. Factors influencing catalytic activity were investigated, including metal–support interaction, effects of heat treatments, chemical composition of gold clusters, the size of gold nanoparticles and catalytic conditions. It was found that the anions present in gold clusters play a role in determining the catalytic activity in this reaction, with NO3− diminishing the catalytic activity. High catalytic activity was attributed to the formation of large gold nanoparticles (>2 nm) that coincides with partial removal of ligands which occurs during heat treatment and catalysis. Selectivity towards the formation of methyl benzoate can be tuned by selection of the reaction temperature. The catalysts were characterised using transmission electron microscopy, UV-vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy

Combination of diffuse reflectance and transmittance spectroscopy to obtain optical properties of liquid phantoms

We present a simple fiber-optics probe system that could be used in any lab for convenient determination of optical properties of liquid phantoms based on diffuse reflectance and transmittance measurements in the visible/near-infrared region. We employed Monte Carlo simulations to determine the optimal system setup and to test the inverse algorithm employed to extract the optical properties from measured reflectance and transmittance. The inverse algorithm involved obtaining the fit merit function for values within the optical property range and determining the minimum. The performance of the method was tested by predictive error and validated using similar matrix of milk–ink phantoms on reflectance and transmittance. In the range of optical properties of phantoms with optical properties of 0 to 0.5 cm−1 for μa and 20 to 140 cm−1 for μs, the median prediction error for the test phantoms at 630 nm was 1.51% for μs and 8.82% for μa. The median difference in predicted values versus expected values was 1.15 cm−1 for μs and 0.01 cm−1 for μa. In comparison with other techniques, our method was a simple, fast, and convenient way to determine optical properties of liquid phantoms

Determination optical properties of tissue-like phantoms using diffuse reflectance and transmittance spectroscopy

We present a simple, convenient fibre-optics probe system for the determination optical properties of tissue-like liquid phantoms based on diffuse reflectance and transmittance measurements at the wavelength of visible-near-infrared region. The method combined Monte Carlo simulations, multiple polynomial regression and a Newton-Raphson algorithm for solving nonlinear equation system. In the range of optical properties of phantom with the μa at 0 – 0.5 cm-1 and the μs’ at 3 – 45 cm-1, the mean prediction error at 630 nm was 1.91 % for μs’ and 7.51 % for μa. The performance of the method is further tested by predictive error and validated using similar matrix of milk-ink phantoms on reflectance and transmittance

Theoretical modelling of modulation depth of acoustic optical imaging at varying mechanical properties

The signal from acousto-optical imaging is affected by the mechanical properties of a sample. A theoretical model showed that speed of sound, density, peizooptical coefficient, and acoustic amplitude affect modulation depth