Reflection Of Visible Light Research Articles

Preparation of MgIn2S4/g-C3N4 for enhanced ranitidine photocatalytic degradation activity via Z-scheme electron transfer

The evidence so far indicates that ranitidine (RAN) contains N-nitrosodimethylamine (NDMA), a strong carcinogen, which is extremely harmful to human health under long-term exposure. Hence, a well-design Z-scheme heterostructure composed of 3D MgIn2S4 micro-flower and 2D g-C3N4 nanosheets was fabricated and used to remove RAN. The optimal photocatalyst (MG-30) exhibited the fastest RAN degradation rate of 0.24685 min−1 within 30 min under visible light, which was 78.1 and 19.8 times higher than those of bare MgIn2S4 and g-C3N4, respectively. Impressively, MG-30 was exceedingly resistant to environmental variations including organic matter, inorganic salts and aqueous substrates. In the meantime, MG-30 boasted the merit such as wide pH range for RAN removal. The excellent results originated from the construction of Z-scheme heterojunctions, which improved the carrier separation efficiency and retained the strong redox ability of MG-30, thereby contributing to the creation of rich active species. Meanwhile, the 3D/2D structure of MgIn2S4/g-C3N4 overrode the limited reflection of visible light. The active species analyses revealed that superoxide radical (·O2−) and hydroxyl radical (·OH) mainly participated in RAN degradation. Furthermore, the possible degradation pathways of RAN and toxicity analysis of intermediates produced were presented. This work emphasizes practical application potential of Z-scheme heterostructure photocatalysts for emerging contaminants degradation in wastewater.

Engineering all-polymer planar photonic crystals as aegises against sunlight overheating

Reducing heating by sunlight is of paramount interest for sustainability and energy efficiency. Solar heating causes harmful CO2 emissions related to the cooling of buildings and vehicles cooling and causes a reduction in greenhouse crop yields during hot seasons. Therefore, reducing the absorption of sunlight with low-cost passive systems could play a major role in energy saving and human sustainability from an environmental standpoint. In this work, dielectric mirrors (aegises) are designed to reflect near-infrared radiation and fabricated out of different polymer pairs ranging from commodity to specialty polymers. Structurally similar tandem structures are designed using a quantitative rationale that allows for predicting thermal shielding efficiency that could be used to design optimized reflectors. As a proof-of-concept, structures are designed via the presented rationale and then fabricated out of different polymer pairs and tested. This allowed to study the influence of materials’ dielectric contrast on the efficiency in heat reduction. Thanks to the new rationale and the improved materials, although coming at the cost of an increase of reflectance of visible light, an efficiency of 27 % is achieved with the polymer pair providing the higher dielectric contrast, namely the Aquivion-poly(N-vinylcarbazole) one.

Thermo-optical performance of building glass under salt sedimentation

The phenomenon of salt sedimentation on the building glass surface occurs in coastal salt-fog climates, leading to the changes in surface heat transfer characteristics and optical properties, which affects the indoor environment and gradually reduces building energy performance. Regrettably, there remains a paucity of research concerning the impact of salt sedimentation on the thermal and optical performances of building glass. This study investigated the salt sedimentation features of building glass using an indoor accelerated test, and explored the relationships between surface heat transfer coefficients, optical properties and salt sedimentation. As the spray duration grew, the sedimented salt stains appeared more dispersed and less dense, but their dimensions increased, exhibiting an exponential growth tendency. The salt sedimentation per unit area grew logarithmically with the spray duration, with the magnitudes being 14.4 to 40.0 mg/m2 and 15.6 to 44.3 mg/m2 under 5% and 10% brine concentration conditions, respectively. The convection heat transfer coefficient (CHTC) and radiative heat transfer coefficient (RHTC) showed a linear monotonic increase with the salt sedimentation, in contrast to the control condition, with the maximum growth rates reaching 178.7% and 97.2%, respectively. The extended CHTC model could be used to calculate the CHTC regarding the impact of salt sedimentation and wind speed. The entire solar spectral transmittance and reflectance was affected by salt sedimentation, and the visible light transmittance, reflectance, hemispherical emissivity, and shading coefficient of low-E and clear glasses all decreased linearly with the increase of salt sedimentation.

Uniplanar multirod TDR probe for soil water content measurement over a larger spatial scale

AbstractThis study developed a uniplanar multirod time domain reflectometry (TDR) probe and evaluated it in laboratory experiments for soil water measurement over a larger spatial scale. The sampling volume of the probe was determined by simulating the electric potential distribution around the probe rods by using the HYDRUS‐2D software package and verified by comparison with the measured dielectric constant in saturated sand. The performance of the probe was evaluated by comparing its dielectric measurements in wet sand over a wide range of water content during evaporative drying with that measured by CS640 probes. Additionally, the dependency of visible light reflection on the water content of the sand was evaluated. The results revealed that the average effective thickness of the probe's sampling volume was 5–6 cm on both sides of the plane of the probe rods. The probe accurately measured the soil water content over a 0.88 m2 spatial area. The visible light reflectance of the variably saturated sand surface and the corresponding water content of the sand follow a soil water retention function‐type relationship. The usage of the multirod TDR measurement system at a larger spatial scale carries practical implications, especially in increasing the accuracy of remote sensing data.

Changes in optical properties of polymeric materials due to atomic oxygen in very low Earth orbit

Atomic oxygen (AO) is the dominant constituent of the residual atmosphere in low Earth orbit (LEO). AO collides with spacecraft at a velocity of 8 km/s, causing oxidation and erosion of polymeric materials. Particularly in very low Earth orbit (VLEO) at altitudes below 300 km, the AO density is at least ten times that at 500–700 km, and the concentration of molecular nitrogen (N2) is 10% or more. Such high-flux AO and N2 can cause nonlinear processes and mass losses for polymers. This study aims to clarify the optical property changes for polymeric materials exposed to LEO and VLEO in the Material Degradation Monitor (MDM) mission onboard the Super-Low-Altitude Test Satellite (SLATS). The AO and N2 fluences and the UV irradiances were estimated using the NRLMSISE-00 atmospheric and solar radiation models. The relationships were investigated between the changes in CCD images and the estimated fluences of the samples. For silsesquioxane (SQ)-coated polyimide film, the diffuse reflection of visible light increased noticeably with an AO fluence above 1 × 1021 atoms/cm2. The formation of a silica layer on the coating induces cracks. For silver-coated FEP films, the diffuse reflection increased entirely at AO fluences above 3 × 1021 atoms/cm2. The AO and N2 collisions would erode and roughen the FEP surfaces. Visible transmission through silver-coated FEP films also increased locally with increasing AO fluence, indicating that some AO oxidized the silver layer despite the presence of an Inconel (Ni alloy) layer. The visible reflection from Beta Cloth was decreased by its reaction with UV. Further, the competitive reactions with UV and AO resulted in two-step changes in the visible reflection from the ETFE polymer (cable covering).

Mapping Insect-Proof Screened Citrus Orchards Using Sentinel-2 MSl Time-Series Images

Citrus is a crucial agricultural commodity of the hilly subtropical regions of southern China. Attempts in recent years to combat the destructive disease Huanglongbing (HLB) have led to citrus orchards being covered with insect-proof screens (IPS). Understanding which citrus orchards are covered by IPS is crucial for regional water and soil conservation, as well as control of plastic pollution. However, monitoring of orchards is complicated by IPS spectral interference in remotely sensed image classification. Here, an optimal feature combination scheme is developed and tested for mapping citrus orchards that use IPS. Seasonal Sentinel-2 images from 2021 were used to define indices for vegetation, plastic mulch, red edge, and texture. These were combined with topographic and land surface temperature using random forest classification to determine optimal feature discrimination combinations for orchards in Xunwu County, Jiangxi Province. Results show: (1) significantly higher visible light reflectance from IPS orchards ensures spectral discrimination between IPS covered and uncovered orchards. (2) After feature optimization, the seasonal spectral band has the highest accuracy (86%) in single feature classification. The addition of conventional indices and topographic-temperature features improves classification to 92%. (3) Xunwu County had 460 km2 of citrus orchard cover in 2021, with 88 km2 (19%) of that total being covered with IPS. Our method effectively and accurately maps citrus orchards with or without IPS coverage at 10 m resolution. The effective monitoring of large-scale IPS in other regions can now support the development of local and regional sustainable agricultural policies.

Preparation of cool composite pigment by the layer-by-layer assembling of phthalocyanine green on the surface of rutile TiO2

Purpose This study aims to fabricate a cool phthalocyanine green/TiO2 composite pigment (PGT) with high near-infrared (NIR) reflectance, good color performance and good heat-shielding performance under sunlight and infrared irradiation. Design/methodology/approach With the help of anionic and cationic polyelectrolytes, the PGT composite pigment was prepared using a layer-by-layer assembly method under wet ball milling. Based on the light reflectance properties and color performance tested by ultraviolet-visible-NIR spectrophotometer and colorimeter, the preparation conditions were optimized and the properties of PGT pigment with different assembly layers (PGT-1, PGT-3, PGT-5 and PGT-7) were compared. In addition, their heat-shielding performance was evaluated and compared by temperature rise value for their coating under sunlight and infrared irradiation. Findings The PGT pigment had a core/shell structure, and the PG thickness increased with the self-assembly layers, which made the PGT-3 and PGT-7 pigment show higher color purity and saturation than PGT-1 pigment. In addition, the PGT-3 and PGT-7 pigment showed 11%–16% lower light reflectance in the visible region. However, their light reflectance in the NIR region was similar. Under infrared irradiation the PGT-5 and PGT-7 pigment coating showed 1.1°C–3.4°C and 1.3°C–4.7°C lower temperature rise value than PGT-1 pigment coating and physical mixture pigment coating, respectively. And under sunlight the PGT-3 pigment coating showed 1.5–2.6°C lower temperature rise value than the physical mixture pigment coating. Originality/value The layer-by-layer assembling makes the core/shell PGT composite pigment possess low visible light reflectance, high NIR reflectance and good heat-shielding performance.

Bioinspired Photonic Materials from Cellulose: Fabrication, Optical Analysis, and Applications.

Polysaccharides are a class of biopolymers that are widely exploited in living organisms for a diversity of applications, ranging from structural reinforcement to energy storage. Among the numerous types of polysaccharides found in the natural world, cellulose is the most abundant and widespread, as it is found in virtually all plants. Cellulose is typically organized into nanoscale crystalline fibrils within the cell wall to give structural integrity to plant tissue. However, in several species, such fibrils are organized into helicoidal nanostructures with a periodicity comparable to visible light (i.e., in the range 250-450 nm), resulting in structural coloration. As such, when taking bioinspiration as a design principle, it is clear that helicoidal cellulose architectures are a promising approach to developing sustainable photonic materials. Different forms of cellulose-derived materials have been shown to produce structural color by exploiting self-assembly processes. For example, crystalline nanoparticles of cellulose can be extracted from natural sources, such as cotton or wood, by strong acid hydrolysis. Such "cellulose nanocrystals" (CNCs) have been shown to form colloidal suspensions in water that can spontaneously self-organize into a cholesteric liquid crystal phase, mimicking the natural helicoidal architecture. Upon drying, this nanoscale ordering can be retained into the solid state, enabling the specific reflection of visible light. Using this approach, colors from across the entire visible spectrum can be produced, alongside striking visual effects such as iridescence or a metallic shine. Similarly, polymeric cellulose derivatives can also organize into a cholesteric liquid crystal. In particular, edible hydroxypropyl cellulose (HPC) is known to produce colorful mesophases at high concentrations in water (ca. 60-70 wt %). This solution state behavior allows for interesting visual effects such as mechanochromism (enabling its use in low-cost colorimetric pressure or strain sensors), while trapping the structure into the solid state enables the production of structurally colored films, particles and 3D printed objects. In this article, we summarize the state-of-the-art for CNC and HPC-based photonic materials, encompassing the underlying self-assembly processes, strategies to design their photonic response, and current approaches to translate this burgeoning green technology toward commercial application in a wide range of sectors, from packaging to cosmetics and food. This overview is supported by a summary of the analytical techniques required to characterize these photonic materials and approaches to model their optical response. Finally, we present several unresolved scientific questions and outstanding technical challenges that the wider community should seek to address to develop these sustainable photonic materials.

Light scattering in stacked mesophyll cells results in similarity characteristic of solar spectral reflectance and transmittance of natural leaves

Solar spectral reflectance and transmittance of natural leaves exhibit dramatic similarity. To elucidate the formation mechanism and physiological significance, a radiative transfer model was constructed, and the effects of stacked mesophyll cells, chlorophyll content and leaf thickness on the visible light absorptance of the natural leaves were analyzed. Results indicated that light scattering caused by the stacked mesophyll cells is responsible for the similarity. The optical path of visible light in the natural leaves is increased with the scattering process, resulting in that the visible light transmittance is significantly reduced meanwhile the visible light reflectance is at a low level, thus the visible light absorptance tends to a maximum and the absorption of photosynthetically active radiation (PAR) by the natural leaves is significantly enhanced. Interestingly, as two key leaf functional traits affecting the absorption process of PAR, chlorophyll content and leaf thickness of the natural leaves in a certain environment show a convergent behavior, resulting in the high visible light absorptance of the natural leaves, which demonstrates the PAR utilizing strategies of the natural leaves. This work provides a new perspective for revealing the evolutionary processes and ecological strategies of natural leaves, and can be adopted to guide the improvement directions of crop photosynthesis.

Construction of F–F@FeVO4/ZnCo2O4 photocatalysts with heterojunction interfacial enhancement and surface oxygen vacancies for the removal of tetracycline, sulfamethoxazole, ciprofloxacin and Cr(VI)

For the purpose of promoting application of green and sustainable photocatalytic materials in real-world composite wastewater remediation, developing stable, efficient and pollution-free treatment devices is necessary and actually urgent. We grew vertical nanosheets consisting of FeVO4/ZnCo2O4 directly on the surface of iron foam (F–F), which intertwined to form F–F@FeVO4/ZnCo2O4 p-n heterojunction catalysts with a three-dimensional framework structure. The F–F@FeVO4/ZnCo2O4 photocatalyst showed excellent photocatalytic performance achieving 96.32%, 92.85%, 95.92% and 97.17% removal efficiencies in the presence of tetracycline (TC), sulfamethoxazole (SMX), ciprofloxacin (CIP) and Cr(VI), respectively. In addition, the photocatalyst was assembled into a simulated photoreactor, enabling the continuous treatment of composite wastewater. The reactor achieved removal efficiencies of 94.81%, 90.02%, 94.17% and 97.15% for TC, SMX, CIP and Cr(VI), respectively, in a 100 min reaction. Furthermore, only after ten photocatalytic cycles under visible light does the catalytic efficiency of the reactor decrease slightly. The excellent performance may be attributed to unique structures that reduce visible light reflection and provide highly reactive reaction centers, as well as surface oxygen vacancies and heterojunctions to accelerate photocarrier separation and free radical generation. The high porosity of F–F also reduces the obstruction of visible light between branches. Moreover, the method of growing FeVO4/ZnCo2O4 active components on F–F overcomes a number of problems (increased interfacial charge transfer impedance, poor structural stability and nonuniform distribution, etc.) associated with conventional methods of combining nanomaterials with recyclable substrates (loading, introduction of adhesives and hybridization, etc.). Density functional theory (DFT) calculations explain the mechanism of interface enhancement.

Passivation of oxygen vacancy defects in conductive ZnO nanoparticles via low-temperature annealing in NF3

Oxygen vacancies (VO) often exist in wide-bandgap metal oxide semiconductors (MOSs) as deep-level defects and undermine the reliability of various optoelectronic devices based on MOSs. Conventional methods to passivate VO defects, such as high-temperature annealing or plasma treatment, can compromise device performance. This work demonstrates that passivation of VO defects in aluminum-doped ZnO (AZO) nanoparticles can be realized through low-temperature annealing (350 °C) in an NF3 atmosphere. After the NF3 annealing, the longitudinal optical phonon scattering mode in Raman spectroscopy, the visible light emission intensity in photoluminescence spectroscopy, and the oxygen deficiency-related peak in x-ray photoelectron spectroscopy decrease simultaneously, indicating the passivation of VO defects in AZO nanoparticles. As a result, AZO nanoparticles show higher visible light reflectance and better stability of electrical conductivity owing to the suppression of deep-level light absorption and gas molecule adsorption. This work also offers insights into the passivation mechanism of VO defects in MOSs.

Petrographic Microscopy with Ray Tracing and Segmentation from Multi-Angle Polarisation Whole-Slide Images

‘Slide scanners’ are rapid optical microscopes equipped with automated and accurate x-y travel stages with virtual z-motion that cannot be rotated. In biomedical microscopic imaging, they are widely deployed to generate whole-slide images (WSI) of tissue samples in various modes of illumination. The availability of WSI has motivated the development of instrument-agnostic advanced image analysis software, helping drug development, pathology, and many other areas of research. Slide scanners are now being modified to enable polarised petrographic microscopy by simulating stage rotation with the acquisition of multiple rotation angles of the polariser–analyser pair for observing randomly oriented anisotropic materials. Here we report on the calibration strategy of one repurposed slide scanner and describe a pilot image analysis pipeline designed to introduce the wider audience to the complexity of performing computer-assisted feature recognition on mineral groups. The repurposed biological scanner produces transmitted light plane- and cross-polarised (TL-PPL and XPL) and unpolarised reflected light (RL) WSI from polished thin sections or slim epoxy mounts at various magnifications, yielding pixel dimensions from ca. 2.7 × 2.7 to 0.14 × 0.14 µm. A data tree of 14 WSI is regularly obtained, containing two RL and six of each PPL and XPL WSI (at 18° rotation increments). This pyramidal image stack is stitched and built into a local server database simultaneously with acquisition. The pyramids (multi-resolution ‘cubes’) can be viewed with freeware locally deployed for teaching petrography and collaborative research. The main progress reported here concerns image analysis with a pilot open-source software pipeline enabling semantic segmentation on petrographic imagery. For this purpose, all WSI are post-processed and aligned to a ‘fixed’ reflective surface (RL), and the PPL and XPL stacks are then summarised in one image, each with ray tracing that describes visible light reflection, absorption, and O- and E-wave interference phenomena. The maximum red-green-blue values were found to best overcome the limitation of refractive index anisotropy for segmentation based on pixel-neighbouring feature maps. This strongly reduces the variation in dichroism in PPL and interference colour in XPL. The synthetic ray trace WSI is then combined with one RL to estimate modal mineralogy with multi-scale algorithms originally designed for object-based cell segmentation in pathological tissues. This requires generating a small number of polygonal expert annotations that inform a training dataset, enabling on-the-fly machine learning classification into mineral classes. The accuracy of the approach was tested by comparison with modal mineralogy obtained by energy-dispersive spectroscopy scanning electron microscopy (SEM-EDX) for a suite of rocks of simple mineralogy (granulites and peridotite). The strengths and limitations of the pixel-based classification approach are described, and phenomena from sample preparation imperfections to semantic segmentation artefacts around fine-grained minerals and/or of indiscriminate optical properties are discussed. Finally, we provide an outlook on image analysis strategies that will improve the status quo by using the first-pass mineralogy identification from optical WSI to generate a location grid to obtain targeted chemical data (e.g., by SEM-EDX) and by considering the rock texture.

Stationary and Transient Asymmetric Features in Tropical Cyclone Eye with Wavenumber-1 Instability: Case Study for Typhoon Haishen (2020) with Atmospheric Motion Vectors from 30-Second Imaging

Abstract Dynamics of low-level flows in the eye of Typhoon Haishen (2020) in its late phase of intensification are investigated with a special rapid-scan observation of the Himawari-8 geosynchronous satellite conducted every 30 s. This is accomplished by deriving storm-relative atmospheric motion vectors at an unprecedentedly high spatiotemporal resolution by tracking clouds across five consecutive visible-light reflectivity. The overall low-level circulation center was situated several kilometers away from the storm center defined in terms of the inner edge of the lower part of eyewall clouds. The shift direction is rearward of the storm translation, consistently with a numerical study of the tropical cyclone (TC) boundary layer. Over the analysis period of 10 h, azimuthal-mean tangential wind around this center was increased at each radius within the eye, and the rotational angular velocity was nearly homogenized. The instantaneous low-level circulation center is found to orbit around the overall circulation center at distances around 5 km. Its orbital angular speed was close to the maximum angular speed of azimuthal-mean tangential winds. This rotating transient disturbance is found to transport angular momentum inward, which explains the tangential wind increase and the angular velocity homogenization in the eye. These features are consistent with an algebraically growing wavenumber-1 barotropic instability, whose impact on TC structures has not been explored. This instability enhances wavenumber-1 asymmetry in ring-shaped vorticity, which can be induced by various processes such as translation, environmental shear, and exponential barotropic instability. Therefore, it may appear broadly in TCs to affect wind distribution in their eyes. Significance Statement Axially asymmetric transient features in the inner cores of tropical storms have been suggested to profoundly affect the structures and the time evolutions of tropical storms. However, the scarcity of observations has hindered studying such processes observationally. By using a specially conducted high-frequency satellite imaging of Typhoon Haishen (2020), we derived atmospheric motion vectors nearly homogeneously at an unprecedentedly high spatiotemporal resolution. Various kinds of asymmetric motions in low-level flows in the eye were found. Of particular interest is a special type of wavenumber-1 instability whose role has not drawn much attention; the instability was found to provide angular momentum transport consistent with the measured homogenization of the rotation.

First-principles investigation on structural and photoelectric properties of (Nb, Ta) codoped anatase TiO2

The structural and photoelectric properties of (Nb, Ta) codoped anatase TiO2 were studied by first-principles calculations based on density functional theory and the Hubbard U correction. The results demonstrated that hybridized states composed of Ta 5d and Nb 4d orbitals at the bottom of the conduction band enabled the Fermi level to enter the conduction band and facilitated (Nb, Ta) codoped anatase TiO2 to exhibit n-type metallic characteristics, and the conductivity of Ti0·875Nb0·0625Ta0·0625O2(I) is approximately 3.2 times that of Ti0·9375Nb0·0625O2. Noted that both conductivity and mobility decreased with the increase of the distance between impurity Nb and Ta atoms and the Nb doping concentration. Moreover, the calculated results of optical properties presented the shifts of the absorption edges towards the ultraviolet region, and (Nb, Ta) codoped anatase TiO2 possessed the high transmittance thanks to its low absorption and reflection of visible light.

Colored Silicon Heterojunction Solar Cells Exceeding 23.5% Efficiency Enabled by Luminescent Down-Shift Quantum Dots.

Colored solar panels, realized by depositing various reflection layers or structures, are emerging as power sources for building with visual aesthetics. However, these panels suffer from reduced photocurrent generation due to the less efficient light harvesting from visible light reflection and degraded power conversion efficiency (PCE). Here, color-patterned silicon heterojunction solar cells are achieved by incorporating luminescent quantum dots (QDs) with high quantum yields as light converters to realize an asthenic appearance with high PCE. It is found that large bandgap (blue) QD layers can convert UV light into visible light, which can notably alleviate the parasitic absorption by the front indium tin oxide and doped amorphous silicon. Additionally, a universal optical path model is proposed to understand the light transmission process, which is suitable for luminescent down-shift devices. In this study, solar cells with a PCE exceeding 23.5% are achieved using the combination of a blue QD layer and a top low refractive index anti-reflection layer. Based on ourbest knoledge,the obtained PCE is the highest for a color-patterned solar cell. The results suggest an enhanced strategy involving incorporation of luminescent QDs with an optical path design for high-performance photovoltaic panels with visual aesthetics.

Sorption Kinetics and Sequential Adsorption Analysis of Volatile Organic Compounds on Mesoporous Silica.

Adsorption-desorption behaviors of polar and nonpolar volatile organic compounds (VOCs), namely, isopropanol and nonane, on mesoporous silica were studied using optical reflectance spectroscopy. Mesoporous silica was fabricated via electrochemical etching of silicon and subsequent thermal oxidation, resulting in an average pore diameter of 11 nm and a surface area of approximately 493 m2/g. The optical thickness of the porous layer, which is proportional to the number of adsorbed molecules, was measured using visible light reflectance interferometry. In situ adsorption and desorption kinetics were obtained for various mesoporous silica temperatures ranging from 10 to 70 °C. Sorption as a function of temperature was acquired for isopropanol and nonane. Sequential adsorption measurements of isopropanol and nonane were performed and showed that, when one VOC is introduced immediately following another, the second VOC displaces the first one regardless of the VOC's polarity and the strength of its interaction with the silica surface.

Metal-Insulator Transition Detection of Vanadium Dioxide Thin Films by Visible Light Reflection.

Vanadium dioxide (VO2)-based thin films have received considerable attention in recent years due to their superior performance in creating next-generation color-rendering materials. The near-room-temperature metal-insulator transition of VO2 promises the advantage of active color tuning in the visible wavelength range. Although various results of dynamic color generation combined with plasmonic nanostructures are currently being investigated, so far, very few studies have addressed the visible-light optical performance of pure VO2 thin films prepared on conventional substrates. This article shows in detail the phase-transition behavior of VO2 thin films in the visible wavelength range of 400-750 nm prepared on glass with subsequent annealing at temperatures of 350, 400, 450, and 500 °C. The results show an anomalous phase transition reducing the overall RGB reflectivity correlated with the crystallization behavior of the VO2 phase and scattering effect. The sample annealed at 350 °C shows the smallest phase transition at 47 °C, correlating with a crystallite size of 7 nm. The blue band reflectivity anomaly after annealing at 450 °C was considered an effect of the secondary reflection. The results of this research could play a huge role in the production of active-switching photonic devices, color-managed reflectors, and temperature indicators.

The Reflectance Characteristics of an Inverse Moth-Eye Structure in a Silicon Substrate Depending on SF6/O2 Plasma Etching Conditions.

The global RE100 campaign is attracting attention worldwide due to climate change caused by global warming, increasingly highlighting the efficiency of renewable energy. Texturing of photovoltaic devices increases the devices’ efficiency by reducing light reflectance at their surfaces. This study introduces the change in light reflectance following the process conditions of plasma etching as a texturing process to increase the efficiency of photovoltaic cells. Isotropic etching was induced through plasma using SF6 gas, and the etch profile was modulated by adding O2 gas to reduce light reflectance. A high etch rate produces high surface roughness, which results in low surface reflectance properties. The inverse moth-eye structure was implemented using a square PR pattern arranged diagonally and showed the minimum reflectance in visible light at a tip spacing of 1 μm. This study can be applied to the development of higher-efficiency optical devices.

Features of Carbon and Silicon Thin Films Reflection Spectra in the Visible Region

The article is devoted to the reflection of visible light from a thin absorbing film. For a number of reasons, thin films have recently been the subject of close study. As part of the work, several non-metal films were fabricated on a glass substrate: silicon films (by resistive evaporation) and carbon films (using laser evaporation). The resulting films have an optical thickness in the range of 1 μm (that is, the actual layer thickness is in the range of 0.2-0.4 μm) and at the same time noticeably absorb the light flux. The films were processed according to the standard method in the visible region using a USB4000 spectrometer. Reflection spectra for each of the films were plotted for several different points on the surface. The spectra look similar when differences in numerical values are not considered. The contribution of the interference of rays reflected from the front and rear boundaries is significant at long wavelengths (in the red region), whereas the interference practically disappears against the background of instrument noise in the short wavelength region (violet part of the spectrum). The reason for this is that absorption during propagation of the short-wavelength part inside the film significantly reduces the intensity of the beam reflected from the rear surface of the film.

Multifunctional Ag-ZrB2 composite film with low infrared emissivity, low visible light reflectance and hydrophobicity

Zirconium Boride (ZrB2) thin film exhibits excellent low infrared emissivity property, but the infrared emissivity in the mid-infrared waveband is still higher than that of traditional metal film. In this work, we reported Ag -ZrB2 nanocomposite film with low emissivity in the mid-infrared waveband by magnetron co-sputtering method. The effect of Ag content on properties of Ag-ZrB2 nanocomposite film were discussed in details. As the increase of Ag content, the infrared emissivity ε3-5μm and ε8-14μm decrease to 0.11 and 0.04 respectively. In addition, the reflectivity(R = 65%) of visible light is still lower than that of conventional metals. Consequently, the Ag-ZrB2 nanocomposite film shows low detectability in the infrared and visible wavebands, which is beneficial for infrared–visible compatible stealth. Meanwhile, ZrB2 matrix changes from hydrophilic to hydrophobic due to Ag segregation to the surface.