Plasmonically Enhanced Reflectance of Heat Radiation from Low-Bandgap Semiconductor Microinclusions

Increased reflectance from the inclusion of highly scattering particles at low volume fractions in an insulating dielectric offers a promising way to reduce radiative thermal losses at high temperatures. Here, we investigate plasmonic resonance driven enhanced scattering from microinclusions of low-bandgap semiconductors (InP, Si, Ge, PbS, InAs and Te) in an insulating composite to tailor its infrared reflectance for minimizing thermal losses from radiative transfer. To this end, we compute the spectral properties of the microcomposites using Monte Carlo modeling and compare them with results from Fresnel equations. The role of particle size-dependent Mie scattering and absorption efficiencies, and, scattering anisotropy are studied to identify the optimal microinclusion size and material parameters for maximizing the reflectance of the thermal radiation. For composites with Si and Ge microinclusions we obtain reflectance efficiencies of 57 - 65% for the incident blackbody radiation from sources at temperatures in the range 400 - 1600 {\deg}C. Furthermore, we observe a broadbanding of the reflectance spectra from the plasmonic resonances due to charge carriers generated from defect states within the semiconductor bandgap. Our results thus open up the possibility of developing efficient high-temperature thermal insulators through use of the low-bandgap semiconductor microinclusions in insulating dielectrics.Comment: Main article (8 Figures and 2 Tables) + Supporting Information (8 Figures

Reconstructing charge-carrier dynamics in porous silicon membranes from time-resolved interferometric measurements

We performed interferometric time-resolved simultaneous reflectance and transmittance measurements to investigate the carrier dynamics in pump-probe experiments on thin porous silicon membranes. The experimental data was analysed by using a method built on the Wentzel-Kramers-Brillouin approximation and the Drude model, allowing us to reconstruct the excited carriers’ non-uniform distribution in space and its evolution in time. The analysis revealed that the carrier dynamics in porous silicon, with ~50% porosity and native oxide chemistry, is governed by the Shockley-Read-Hall recombination process with a characteristic time constant of 375 picoseconds, whereas diffusion makes an insignificant contribution as it is suppressed by the high rate of scattering

Neurovascular unit dysfunction with blood-brain barrier hyperpermeability contributes to major depressive disorder: a review of clinical and experimental evidence

About one-third of people with major depressive disorder (MDD) fail at least two antidepressant drug trials at 1 year. Together with clinical and experimental evidence indicating that the pathophysiology of MDD is multifactorial, this observation underscores the importance of elucidating mechanisms beyond monoaminergic dysregulation that can contribute to the genesis and persistence of MDD. Oxidative stress and neuroinflammation are mechanistically linked to the presence of neurovascular dysfunction with blood-brain barrier (BBB) hyperpermeability in selected neurological disorders, such as stroke, epilepsy, multiple sclerosis, traumatic brain injury, and Alzheimer’s disease. In contrast to other major psychiatric disorders, MDD is frequently comorbid with such neurological disorders and constitutes an independent risk factor for morbidity and mortality in disorders characterized by vascular endothelial dysfunction (cardiovascular disease and diabetes mellitus). Oxidative stress and neuroinflammation are implicated in the neurobiology of MDD. More recent evidence links neurovascular dysfunction with BBB hyperpermeability to MDD without neurological comorbidity. We review this emerging literature and present a theoretical integration between these abnormalities to those involving oxidative stress and neuroinflammation in MDD. We discuss our hypothesis that alterations in endothelial nitric oxide levels and endothelial nitric oxide synthase uncoupling are central mechanistic links in this regard. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to the pathophysiology of MDD may help to identify novel therapeutic and preventative approaches

Reflectance of pigmented polymer coatings: comparisons between measurements and radiative transfer calculations

Solar reflectance spectra of pigmented coatings have been obtained from spectroscopic measurements involving integrating sphere attachments. We demonstrate that measured and computed reflectances of an extended four-flux model [Appl. Opt. 37, 2615 (1998)]</p

Optical properties of nano-structured dye-sensitized solar cells

Radiative transfer computations are carried out to describe the intrinsic and effective optical properties of light diffusing and absorbing materials consisting of anatase titania pigments hosted in an electrolyte medium. The intrinsic visible absorption</p

Observability of resonance optical structure in fractal metallic clusters

We investigate optical properties of the deterministic network model for fractal metallic clusters at the percolation threshold. As input data we used the experimental bulk dielectric function of gold, aluminum, and nickel. Sharp absorption resonances in</p

Polaron absorption in tungsten oxide nanoparticle aggregates

Small tungsten oxide nanoparticles were prepared from a heated tungsten filament, by gas evaporation in air at pressures between 1 and 9 Torr. Transmission electron microscopy showed that the median particle diameter increased with pressure during evapora</p

Experimental and Monte Carlo analysis of isotropic multiple Mie scattering

This paper demonstrates patterns in the multiple scattering behavior of three test cases, of which one is verified experimentally. Mie scattering patterns are known to emerge when the scattering angle is plotted versus the dimensionless parameter qR, where q is the scattering wave vector for a single particle, and R is the radius of the scattering particle. The power-law behavior of single scattering is modified, but not completely destroyed, when translated to multiple scattering situations. The predicted behavior is seen in translucent sheets, where transparent refractive index matched micro (TRIMM) particles scatter light, a case which is ideal to model with Mie scattering. © 2004 Elsevier B.V. All rights reserved

Oxidation kinetics of nickel nanoparticles

The oxidation kinetics of nickel particles with an approximate median size of 15 nm was determined by thermogravimetry. The particles had a thin initial oxide shell amounting to 36 wt % of the sample. The kinetics was studied in pure oxygen in the tempera</p