Light-scattering Properties Research Articles

Density-wave ordering in a unitary Fermi gas with photon-mediated interactions

A density wave (DW) is a fundamental type of long-range order in quantum matter tied to self-organization into a crystalline structure. The interplay of DW order with superfluidity can lead to complex scenarios that pose a great challenge to theoretical analysis. In the past decades, tunable quantum Fermi gases have served as model systems for exploring the physics of strongly interacting fermions, including most notably magnetic ordering1, pairing and superfluidity2, and the crossover from a Bardeen–Cooper–Schrieffer superfluid to a Bose–Einstein condensate3. Here, we realize a Fermi gas featuring both strong, tunable contact interactions and photon-mediated, spatially structured long-range interactions in a transversely driven high-finesse optical cavity. Above a critical long-range interaction strength, DW order is stabilized in the system, which we identify via its superradiant light-scattering properties. We quantitatively measure the variation of the onset of DW order as the contact interaction is varied across the Bardeen–Cooper–Schrieffer superfluid and Bose–Einstein condensate crossover, in qualitative agreement with a mean-field theory. The atomic DW susceptibility varies over an order of magnitude upon tuning the strength and the sign of the long-range interactions below the self-ordering threshold, demonstrating independent and simultaneous control over the contact and long-range interactions. Therefore, our experimental setup provides a fully tunable and microscopically controllable platform for the experimental study of the interplay of superfluidity and DW order.

Melanin Stacking Differences in Pigmented and Non-Pigmented Melanomas: Quantitative Differentiation between Pigmented and Non-Pigmented Melanomas Based on Light-Scattering Properties.

Cutaneous melanoma is a cancer with metastatic potential characterized by varying amounts of pigment-producing melanocytes, and it is one of the most aggressive and fatal forms of skin malignancy, with several hundreds of thousands of cases each year. Early detection and therapy can lead to decreased morbidity and decreased cost of therapy. In the clinic, this often translates to annual skin screenings, especially for high-risk patients, and generous use of the ABCDE (asymmetry, border irregularity, color, diameter, evolving) criteria. We have used a new technique termed vibrational optical coherence tomography (VOCT) to non-invasively differentiate between pigmented and non-pigmented melanomas in a pilot study. The VOCT results reported in this study indicate that both pigmented and non-pigmented melanomas have similar characteristics, including new 80, 130, and 250 Hz peaks. Pigmented melanomas have larger 80 Hz peaks and smaller 250 Hz peaks than non-pigmented cancers. The 80 and 250 Hz peaks can be used to quantitative characterize differences between different melanomas. In addition, infrared light penetration depths indicated that melanin in pigmented melanomas has higher packing densities than in non-pigmented lesions. Using machine learning techniques, the sensitivity and specificity of differentiating skin cancers from normal skin are shown to range from about 78% to over 90% in this pilot study. It is proposed that using AI on both lesion histopathology and mechanovibrational peak heights may provide even higher specificity and sensitivity for differentiating the metastatic potential of different melanocytic lesions.

Double-sided growth of MoSe2 nanosheets onto hollow zinc stannate (ZnO, ZnSnO3, and SnO2) nanofibers (h-ZTO) for efficient CO2 photoreduction

The design of photocatalysts that encourage the conversion of CO2 into useful chemicals has been a recent topic of interest, owing to the consequences of climate change. This study develops h-ZTO/MoSe2 hybrid photocatalysts with multiple heterojunctions using facile electrospinning followed by a solvothermal method. MoSe2 nanosheets are formed inside and outside the h-ZTO hollow nanofibers (NFs), increasing the number of accessible active sites and improving the light-scattering properties, which are fundamental for improved photocatalytic performance. A hybrid photocatalyst was obtained by adjusting the h-ZTO/MoSe2 ratio, which showed significantly higher photocatalytic activity than pure h-ZTO. The morphology, structural, phase composition, and functional characteristics of the synthesized photocatalysts were investigated using FE-SEM, TEM, XRD, XPS, PL, TR-PL, and PEC. The 10 wt% h-ZTO/MoSe2 hybrid photocatalyst demonstrated the effective photocatalytic transformation of CO2 into CO, H2, and CH4 with yielding rates of 140, 64, and 33 µmolg−1h−1, respectively. Furthermore, it exhibited the highest CO2 photoreduction selectivity of 93%. This extraordinary performance can be attributed to the uniform growth of the MoSe2 on the internal and external walls of the hollow nanofibers, which enhanced their light-scattering capabilities and provided abundant active sites for the activation and desorption of CO2 throughout the reaction.

Electrically programmable solid-state metasurfaces via flash localised heating

In the last decades, metasurfaces have attracted much attention because of their extraordinary light-scattering properties. However, their inherently static geometry is an obstacle to many applications where dynamic tunability in their optical behaviour is required. Currently, there is a quest to enable dynamic tuning of metasurface properties, particularly with fast tuning rate, large modulation by small electrical signals, solid state and programmable across multiple pixels. Here, we demonstrate electrically tunable metasurfaces driven by thermo-optic effect and flash-heating in silicon. We show a 9-fold change in transmission by <5 V biasing voltage and the modulation rise-time of <625 µs. Our device consists of a silicon hole array metasurface encapsulated by transparent conducting oxide as a localised heater. It allows for video frame rate optical switching over multiple pixels that can be electrically programmed. Some of the advantages of the proposed tuning method compared with other methods are the possibility to apply it for modulation in the visible and near-infrared region, large modulation depth, working at transmission regime, exhibiting low optical loss, low input voltage requirement, and operating with higher than video-rate switching speed. The device is furthermore compatible with modern electronic display technologies and could be ideal for personal electronic devices such as flat displays, virtual reality holography and light detection and ranging, where fast, solid-state and transparent optical switches are required.

Characteristics and Sources of PM2.5 and Its Light-scattering Properties with Different Chemical Compositions in Urban Area of Beijing

In recent years, the concentration of PM2.5 in the Beijing urban area has decreased with the increase in the proportion of secondary inorganic ions. In order to explore the characteristics and sources of the light scattering of PM2.5 with different chemical compositions, PM2.5 with its chemical components and scattering coefficient were continuously measured at hourly resolution in the Beijing urban area from December 2020 to November 2021. The components, scattering characteristics, and sources of PM2.5 were analyzed. The results showed that NO3- was the major component of PM2.5 in the Beijing urban area, and the ω(NO3-) and ω(SNA) were 24% and 46% in PM2.5, respectively. PM2.5 could be divided into six types according to mass concentration and component proportion. The occurrence frequency of the good-type was the highest during the study with a similar duration in the four seasons, and the ω(SNA), ω(OM), and ω(FS) were 32%, 32%, and 28% in PM2.5, respectively. The dust(D)-type and the OM(O)-type appeared mainly in spring and summer with the lowest frequency during the study. FS and OM were their major components, and the ω(FS) and ω(OM) were 66% and 46% in PM2.5, respectively. The OM+SO42-(OS)-type, OM+NO3-(ON)-type, and NO3-(N)-type appeared mainly in the afternoon in summer, in the early morning and morning in winter, and at approximately 07:00 every day in spring. Under the condition of low humidity[relative humidity (RH)<40%], the MSE of N-type PM2.5 was the highest (4.3 m2·g-1), and that of D-type PM2.5 was the lowest (2.1 m2·g-1), reflecting the high scattering ability of SNA. The MSE increased with relative humidity. Under the condition of high humidity (RH>80%), the MSE of all types of PM2.5 rose to 1.5 to 1.8 times the values under low humidity. The variation trends of SAE showed that particle size increased with the rising of RH level. Under non-high humidity conditions, the scattering coefficients reconstructed by the revised IMPROVE formula fitted well with the measured values at hourly resolution, the correlation coefficients were between 0.81 and 0.97, and the slopes were between 1.00 and 1.21 except for that of D-type. The N-type fitting result was the best. Under high-humidity conditions, the R and the slopes were from 0.82 to 0.84 and from 0.48 to 0.53, respectively. The annual Bsca was 203.8 Mm-1, and N-type PM2.5 contributed the most, accounting for 53%, in which the large particles of NH4NO3 were the major contributor. Bsca of good-type PM2.5 was 67.2 Mm-1, in which small particles of OM were the major contributor. Bsca was 1.5 times the annual Bsca(dry), whereas the Bsca values of SNA were 1.8 to 2.1 times the Bsca(dry). The peak value of NO3- and RH simultaneously appeared around 07:00, resulting in the maximum Bsca of NH4NO3 at this time. The peak value of SO42- and the Bsca of (NH4)2SO4 mainly appeared at 16:00 and at 04:00, respectively. The diurnal variation curves of OM concentration and Bsca were consistent, and the bimodal peaks appeared at 13:00 and 20:00, respectively. In spring and winter, NO3-, SO42- and OM mainly came from the plains east of the Taihang Mountains, and their potential source regions were not in any particular place in summer and autumn; the main potential source regions of FS were the northwest areas of Beijing in spring and autumn. The flow with high RH across the south and southeast of the north China plain and the eastern rim of Bohai Sea was likely to increase the weighted potential source contribution factor values of Bsca of SNA in this region.

Fractal Aggregates of Submicron-sized Grains in the Young Planet-forming Disk around IM Lup

Despite rapidly growing disk observations, it remains a mystery what primordial dust aggregates look like and what the physical and chemical properties of their constituent grains (monomers) are in young planet-forming disks. Confrontation of models with observations to answer this mystery has been a notorious task because we have to abandon a commonly used assumption, perfectly spherical grains, and take into account particles with complex morphology. In this Letter, we present the first thorough comparison between near-infrared scattered light of the young planet-forming disk around IM Lup and the light-scattering properties of complex-shaped dust particles. The availability of scattering observations at multiple wavelengths and over a significant range of scattering angles allows for the first determination of the monomer size, fractal dimension, and size of dust aggregates in a planet-forming disk. We show that the observations are best explained by fractal aggregates with a fractal dimension of 1.5 and a characteristic radius larger than ∼2 μm. We also determined the radius of the monomer to be ∼200 nm, and monomers much smaller than this size can be ruled out on the premise that the fractal dimension is less than 2. Furthermore, dust composition comprising amorphous carbon is found to be favorable to simultaneously account for the faint scattered light and the flared disk morphology. Our results support that planet formation begins with fractal coagulation of submicron-sized grains. All the optical properties of complex dust particles computed in this study are publicly available.

Increased light scattering in electrically stimulated beef longissimus muscle fibres contributes to the observed meat colour at grading

Context Electrical stimulation is often used by meat processors to promote fast muscle pH decline and optimise meat quality. Meat colour can be made more acceptable by this process, but how this relates to the microstructure and light-scattering properties of muscle is still unknown. Aims To investigate the effect of electrical stimulation of beef carcasses on the meat colour at grading and the role of the muscle fibre microstructure and light scattering in determining colour differences. Methods Electrical stimulation inputs (electrical stimulation inputs (ES), n = 8; no electrical stimulation inputs (NS), n = 8) were applied to beef carcasses from female cattle of approximately 18–24 months of age. ES comprised electrical immobilisation, bleed rail electric simulation and hide puller rigidity probe, which have all been shown to increase pH fall post-mortem in beef carcasses. pH fall was monitored, the longissimus thoracis was graded at 20–22 h postmortem and measurements were made of colour, muscle-fibre structure and light scattering. Key results The decline of pH was increased in ES relative to NS, as indicated by lower pH at 2 h postmortem (5.83 vs 6.86 respectively, s.e. = 0.068; P &lt; 0.05) as well as changes in both chromatic colour a* b* and achromatic (no colour) lightness in the muscle. Chromatic changes were evident as higher grader colour scores, increased redness (a*) and yellowness (b*) with higher levels of oxymyoglobin and lower levels of deoxymyoglobin. Achromatic changes were evident as increased lightness (L*) and surface reflectance (%R) at the meat surface, and increased global brightness within the muscle fibres. Conclusions Increased lightness and brightness in electrically stimulated muscles were likely to be due to formation of contraction nodes and distortion of muscle fibres, which changed the microstructure of muscle in ways that increased its light-scattering properties. Implications Consideration of the role of light scattering in determining beef colour at grading will advance understanding of how to improve this important quality trait.

Conventional and Back-Illuminated Cobalt- and Iodine-Mediated Dye-Sensitized Solar Cells for Artificial and Solar Light Conversion

Dye-sensitized solar cells (DSSCs) are among the leading PV technologies for indoor applications. These devices need to be optimized for these illumination conditions since, as it will be demonstrated, the best devices under solar conditions do not originate from the best devices under artificial illumination. This work studies the impact of the photoanode thickness, its light-scattering properties, dye loading, distance from the photoelectrode to the counter electrode on the charge transfer, recombination, and photovoltaic response of cobalt (III/II) bipyridine ([Co(bpy)3] 3+/2+) and iodide/triiodide (I–/I3–) DSSCs under 1 Sun and artificial 1000 lx light illumination. The champion [Co(bpy)3] 3+/2+ device displayed a power conversion efficiency (PCE) of 11.0 and 32.0% under AM1.5G and 1000 lx, respectively. The best I–/I3– cells yielded 9.0% 1 Sun PCE and 23.1% of PCE under 1000 lx. Optimized [Co(bpy)3]3+/2+ and I–/I3– DSSCs demonstrated huge potential as efficient indoor-photovoltaics and can straightforwardly be used as back-illuminated devices to improve the output power under low illumination. Under 1000 lx room light, the champion cobalt DSSCs displayed a record PCE of 27.3% from the rear-side with 85.3% of retention ratio.

REST: A Java Package for Crafting Realistic Cosmic Dust Particles

The overall understanding of cosmic dust particles is mainly inferred from the different Earth-based measurements of interplanetary dust particles and space missions such as Giotto, Stardust, and Rosetta. The results from these measurements indicate the presence of a wide variety of morphologically significant dust particles. To interpret the light-scattering and thermal emission observations arising due to dust in different regions of space, it is necessary to generate computer-modeled realistic dust structures of various shapes, sizes, porosity, bulk density, aspect ratio, and material inhomogeneity. The present work introduces a Java package called Rough Ellipsoid Structure Tool (REST), which is a collection of multiple algorithms, that aims to craft realistic rough-surface cosmic dust particles from spheres, superellipsoids, and fractal aggregates depending on the measured bulk density and porosity. Initially, spheres having N d dipoles or lattice points are crafted by selecting random material and space seed cells to generate a strongly damaged structure, rough surface, and poked structure. Similarly, REST generates rough-surface superellipsoids and poked structure superellipsoids from initial superellipsoid structures. REST also generates rough fractal aggregates, which are fractal aggregates having rough-surface irregular grains. REST has been applied to create agglomerated debris, agglomerated debris superellipsoids, and mixed-morphology particles. Finally, the light-scattering properties of the respective applied structures are studied to ensure their applicability. REST is a flexible structure tool that shall be useful for generating various types of dust structures that can be applied to studying the physical properties of dust in different regions of space.

Low-albedo asteroids: analogues with a high polarization at large phase angles

ABSTRACT While remote observations of the linear polarization of five low-albedo near-Earth asteroids are available at large phase angles, space missions have collected materials from the surface of two of them and one of them is already back to Earth. The structure of the regolith on the surface may be different from that encountered on larger objects, because of their low gravity and thermal stress cycling. Dust particles crushed from low-albedo meteorites (i.e. Orgueil and Allende) are tentatively used as analogues to provide a better approach of such regoliths. The PROGRA2 experiment studies the light-scattering properties of dust particles of various size distributions under Earth’s gravity either deposited or with clouds lifted by an air-draught, as well as under μ-gravity conditions. Similar maximum in polarization (i.e. Pmax) values are obtained experimentally for dark particles deposited or in levitation, showing that multiple scattering is negligible. The increased sensitivity of PROGRA2 instruments, together with imaging techniques, makes it possible to study Pmax with increasing sizes of the lifted particles, up to mm-sizes and above. Our results confirm that particles constituting the regolith are mm-sized and may reach polarization values up to 50 per cent in good agreement with remote observations. Some materials are also suggested to be present on the surface of the particles. Also, huge agglomerates made by random ballistic deposition may be considered as relevant analogues e.g. for pebbles and boulders.

Adaptive statistical filtering of data in the phase images decoding under random additive noise of a photodetector

A method for adaptive statistical filtering of experimental data is proposed to reduce the measurement error of three-dimensional geometric parameters using phase triangulation methods. The method is especially promising for use under conditions of measuring surfaces with random light-scattering properties, a limited dynamic range of a photodetector, and random additive noise. The practical value and efficiency of the proposed approach in the processing of phase images is shown.

The effect of dopant on light trapping characteristics in random silicon nanowires for solar cell applications

The Light management is a fundamental study to improve the solar cell and photoelectrical devices conversion efficiency. Here, the spectral responses of reflection and absorption characteristics of random silicon nanowires (Si-NWs) arrays of different lengths and doping type has been investigated. The Si-NWs have been synthesized by metal induced etching (MIE) approach have dimensions of Sub-wavelength regime. These Si-NWs arrays show efficient light trapping and low reflectance than bare Si due to suppression of Fresnel reflection substantially over a wide spectral range. The comparative study of light trapping in Si-NWs, fabrication by using n-type and p-type Si wafer have been explored to add new dimension in the field of photovoltaic application. Here, diffuse reflection spectra have been used to analyzed the light-scattering properties of Si-NWs, which reveal that the diffuse scattering decreases as the pore depth increases. The field distribution of Si-NWs is simulated using finite differential time domain (FDTD) method, results shows that reflectance could be modified due to light absorption driven by multiple scattering inside the structure reaching high values of apparent absorbance. Current-voltage (I–V) curves have been measured under illumination at standard testing conditions (STC), i.e., 300 K, 1000 W/m2 and 1.5 a.m. global by using solar simulator. These measurement studies indicate that dopant (n-type and p-type) have been effectively influenced the photovoltaic parameters. I–V curve indicated that the power conversion efficiency (PCE) of n-type and p-type doped Si-NWs exhibited PCE of 3.94% and 4.01% respectively.

Fast and Accurate Prediction of Light Scattering from Plasmonic Nanoarrays in Multiple Directions.

The method of moments (MoM) is an efficient electromagnetic numerical method for the accurate prediction of light scattering from plasmonic nanostructures. In practice, the light-scattering properties in different incident directions are often concerning. However, traditional MoM generally resorts to the iterative method, which suffers from the problems of convergence rate and redundant computations for multiple incident excitations. Nanoarray structures will further aggravate these problems due to a large number of unknowns. In this article, an efficient numerical method based on MoM and a hierarchical matrix (H-matrix) algorithm is proposed to solve these problems. Numerical experiments demonstrate the efficiency and accuracy of the proposed method for the prediction of light scattering from plasmonic nanoarrays in multiple directions.

Angular divergence of solar simulators and its impact on the measured Solar Heat Gain Coefficient of fenestration systems

The solar protection feature of shading devices is characterized by the Solar Heat Gain Coefficient (SHGC) or g-value. Given their complex light-scattering properties, it is advisable to test innovative shading devices calorimetrically in a laboratory. In the case of an indoor calorimetric facility, a solar simulator is required as the light source. The light beam radiated by commercial solar simulators is not parallel and in general more divergent than direct sunlight. This study analyses the impact of the angular divergence of radiation from solar simulators on the experimental determination of the SHGC of fenestration systems. It is shown that this effect is not negligible in many cases. Two methods are proposed for this purpose: (1) an experimental one based on measurements with a luminance camera, and (2) a numerical one based on a digital model of a calorimetric facility. Both methods build on the calculation of contribution coefficients from different regions of the field of view of the sample. The methods can be used to correct the effect of angular divergence on SHGC measurements in the future.

Xylanase production by Thermobacillus xylanilyticus is impaired by population diversification but can be mitigated based on the management of cheating behavior

BackgroundThe microbial production of hemicellulasic cocktails is still a challenge for the biorefineries sector and agro-waste valorization. In this work, the production of hemicellulolytic enzymes by Thermobacillus xylanilyticus has been considered. This microorganism is of interest since it is able to produce an original set of thermostable hemicellulolytic enzymes, notably a xylanase GH11, Tx-xyn11. However, cell-to-cell heterogeneity impairs the production capability of the whole microbial population.ResultsSequential cultivations of the strain on xylan as a carbon source has been considered in order to highlight and better understand this cell-to-cell heterogeneity. Successive cultivations pointed out a fast decrease of xylanase activity (loss of ~ 75%) and Tx-xyn11 gene expression after 23.5 generations. During serial cultivations on xylan, flow cytometry analyses pointed out that two subpopulations, differing at their light-scattering properties, were present. An increase of the recurrence of the subpopulation exhibiting low forward scatter (FSC) signal was correlated with a progressive loss of xylanase activity over several generations. Cell sorting and direct observation of the sorted subpopulations revealed that the low-FSC subpopulation was not sporulating, whereas the high-FSC subpopulation contained cells at the onset of the sporulation stage. The subpopulation differences (growth and xylanase activity) were assessed during independent growth. The low-FSC subpopulation exhibited a lag phase of 10 h of cultivation (and xylanase activities from 0.15 ± 0.21 to 3.89 ± 0.14 IU/mL along the cultivation) and the high-FSC subpopulation exhibited a lag phase of 5 h (and xylanase activities from 0.52 ± 0.00 to 4.43 ± 0.61 over subcultivations). Serial cultivations on glucose, followed by a switch to xylan led to a ~ 1.5-fold to ~ 15-fold improvement of xylanase activity, suggesting that alternating cultivation conditions could lead to an efficient population management strategy for the production of xylanase.ConclusionsTaken altogether, the data from this study point out that a cheating behavior is responsible for the progressive reduction in xylanase activity during serial cultivations of T. xylanilyticus. Alternating cultivation conditions between glucose and xylan could be used as an efficient strategy for promoting population stability and higher enzymatic productivity from this bacterium.

Dynamic multifunctional devices enabled by ultrathin metal nanocoatings with optical/photothermal and morphological versatility

Inspired by the intriguing adaptivity of natural life, such as squids and flowers, we propose a series of dynamic and responsive multifunctional devices based on multiscale structural design, which contain metal nanocoating layers overlaid with other micro-/nanoscale soft or rigid layers. Since the optical/photothermal properties of a metal nanocoating are thickness dependent, metal nanocoatings with different thicknesses were chosen to integrate with other structural design elements to achieve dynamic multistimuli responses. The resultant devices demonstrate 1) strain-regulated cracked and/or wrinkled topography with tunable light-scattering properties, 2) moisture/photothermal-responsive structural color coupled with wrinkled surface, and 3) mechanically controllable light-shielding properties attributed to the strain-dependent crack width of the nanocoating. These devices can adapt external stimuli, such as mechanical strain, moisture, light, and/or heat, into corresponding changes of optical signals, such as transparency, reflectance, and/or coloration. Therefore, these devices can be applied as multistimuli-responsive encryption devices, smart windows, moisture/photothermal-responsive dynamic optics, and smartphone app-assisted pressure-mapping sensors. All the devices exhibit high reversibility and rapid responsiveness. Thus, this hybrid system containing ultrathin metal nanocoatings holds a unique design flexibility and adaptivity and is promising for developing next-generation multifunctional devices with widespread application.

Optical properties of an organic-inorganic hybrid film made of regenerated cellulose doped with light-scattering TiO2 particles

Inorganic-organic composites offer immense potential for developing materials with, e.g. improved chemical, optical and electrical properties, by combining characteristics from both substances. In this study, sustainable and modifiable regenerated cellulose films were produced via an ionic liquid process and combined with the excellent properties of titanium dioxide (TiO2) particles to prepare highly light-scattering and UV-absorbing composite film materials. Films with varying TiO2 loadings were cast onto plastic supports and regenerated in water. The resultant TiO2-regenerated cellulose films exhibited homogenous particle dispersion throughout the materials, while some particle size differentiation was observed with scanning electron microscopy, confocal microscopy, energy dispersive X-ray spectroscopy and elemental mapping. Remarkably, the Elrepho spectrophotometer and UV–Vis transmittance and absorbance results confirmed excellent scattering properties for the high-doped TiO2 films in the visible light wavelengths (80%→10% reduction in light transmittance), while complete UV light blocking was achieved even with very low (>0.5–1%) TiO2 addition levels. Furthermore, the TiO2-doped cellulose films also exhibited capabilities for UV activation. TiO2 loading also increased forward and backward scattering of the films, and the laser beam heating rate of the films was affected by both the doping level and thickness of the films. The developed composite material exhibited excellent light-scattering properties with UV shielding capabilities, confirming the potential of the composite for such advanced purposes as photoelectronic, agricultural or packaging applications.

Localized surface plasmon resonance enhanced by the light-scattering property of silver nanoparticles for improved luminescence of polymer light-emitting diodes

This study used photochemical reduction to successfully synthesize triangular silver nanoplates (TAgNPs) and silver nanodecahedrons (AgNDs) with higher light-absorption and higher light-scattering properties, respectively, for the same wavelength. To analyze the contribution of light-absorption and light-scattering of silver nanoparticles to the localized surface plasmon resonance (LSPR) effect, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate was doped with TAgNPs or AgNDs at the same concentration (1.17 μg/cm2) and made into polymer light-emitting diodes (PLEDs). According to the current density-voltageluminance characteristics and electroluminescence (EL) spectra, the enhancement factors for current efficiency and EL intensity for AgND-containing PLEDs were found to be higher than those for PLED with TAgNPs by 24.9% and 138%, respectively. This shows that the metal nanoparticles with higher light-scattering property can induce a relatively strong LSPR effect, which possibly gives a hint to design plasmonic photovoltaic in future.

Electromagnetic resonances observed in small, charged particles

When a particle is charged, electrons can move freely along its surface and influence its optical properties in the same way as a thin, nonuniform metallic layer. These electrons contribute to scattering phenomena, including resonances. We model the light scattering from charged particles and demonstrate that these resonances result from excitation of an anti-symmetric surface plasmon at the layer interfaces. The modeling explains suppression of absorption when the size of the charged particle decreases, as well as differences in the light-scattering efficiencies of as much as a factor of 2 that occur before and after the resonance. These light-scattering properties must be taken into consideration when performing remote-sensing studies of charged particles, like those in the interstellar medium and dust storms.

Choosing a model for laser speckle contrast imaging

Laser speckle contrast imaging (LSCI) is a real-time full-field non-invasive technique, which is broadly applied to visualize blood flow in biomedical applications. In its foundation is the link between the speckle contrast and dynamics of light scattering particles-erythrocytes. The mathematical form describing this relationship, which is critical for accurate blood flow estimation, depends on the sample's light-scattering properties. However, in biological applications, these properties are often unknown, thus requiring assumptions to be made to perform LSCI analysis. Here, we review the most critical assumptions in the LSCI theory and simulate how they affect blood flow estimation accuracy. We show that the most commonly applied model can severely underestimate the flow change, particularly when imaging brain parenchyma or other capillary perfused tissue (e.g. skin) under ischemic conditions. Based on these observations and guided by the recent experimental results, we propose an alternative model that allows measuring blood flow changes with higher accuracy.