Changes In Optical Properties Research Articles

Research of Optical Properties and Biocompatibility in Different Zones of Multilayered Translucent Zirconia on Hydrothermal Aging

Objective: We assessed the changes in optical properties and biocompatibility of transition zones in multilayered translucent monolithic zirconia exposed to prolonged hydrothermal aging and compared the results to those with different yttrium oxide contents. Materials and Methods: Four types of zirconia blocks from IPS e.max ZirCAD were used: 3Y-TZP e.max ZirCAD LT (ZL), 4Y-TZP e.max ZirCAD MT (ZM), 5Y-TZP e.max ZirCAD MT Multi (ZT), and 3Y/5Y-TZP e.max ZirCAD Prime (ZP). A total of 120 specimens (15.0 mm diameter and 1.5 mm height) were fabricated and divided into three groups (n = 10). The aging process for the specimens was conducted in an autoclave set to 134 °C and 0.2 MPa, with durations of 0 h (control), 5 h (first aged), and 10 h (second aged). The optical properties and biocompatibility were analyzed, followed by a statistical analysis of the data (α = 0.05). Results: Before and after aging, ZL and ZP exhibited the lowest color changes. ZT exhibited the highest average transmittance and translucency parameter values, while ZL had the lowest. The water contact angle test showed the highest value in ZM and lowest in ZL across all the aging stages. ZL, ZM, and ZP showed a considerable decrease in the water contact angle; however, ZT did not. A cell counting kit-8 assay showed ZL had the highest value, while ZM had the lowest. A filamentous actin test exhibited the highest value in ZL and lowest in ZM. In the vinculin analysis, ZL and ZT exhibited the lowest values, whereas ZM and ZP had the highest. Conclusion: 3Y/5Y-TZP exhibited a balanced performance across critical parameters, such as color stability, translucency, and biocompatibility, aligning with 3Y-TZP. While 5Y-TZP demonstrated superior translucency, it confirmed the lowest color stability, whereas 3Y-TZP achieved the highest biocompatibility. These properties provide clinicians with a reliable material option that ensures superior esthetic outcomes and long-term prognosis, ultimately contributing to improved patient satisfaction and clinical longevity.

Coupling Effect of Elemental Carbon and Organic Carbon on the Changes of Optical Properties and Oxidative Potential of Soot Particles under Visible Light.

Soot particles, coming from the incomplete combustion of fossil or biomass fuels, feature a core-shell structure with inner elemental carbon (EC) and outer organic carbon (OC). Both EC and OC are known to be photoactive under solar radiation. However, research on their coupling effect during photochemical aging remains limited. This study examines how the optical properties and oxidative potential (OP) of wood, coal, and diesel soot particles with varying EC and OC levels are affected by exposure to visible light. Wood soot, which has the highest OC content, showed the most significant changes in both optical properties and OP, indicating its highest sensitivity to visible light aging. Molecular composition analysis revealed that the reduction of polycyclic aromatic hydrocarbons (PAHs) and methyl-PAHs primarily affects the optical properties, while oxygenated PAHs play a major role in OP. Combined with the results from reactive oxygen species detection, it is suggested that EC initiates photoreactions by generating superoxide anions, while OC undergoes compositional changes that result in subsequent atmospheric effects. These findings enhance our understanding of the photochemical aging process of soot particles and their implications for climate and health.

Hydrogen adsorption on zinc-terminated ZnO(0001) surface at varying coverages and its effects on electronic and optical properties: A DFT+U Study

Abstract Spin-polarized density functional theory implementing Hubbard corrections (DFT+U) were utilized to study H adsorption of different coverages on Zn-terminated ZnO(0001) surface. Changes in electronic and optical properties were observed upon H adsorption of varying coverages, namely with 0.25 monolayer (ML), 0.50 ML, 1 ML, and 2 ML coverage. In terms of surface structure, H atoms were found to adsorb on top of Zn forming Zn-H bond lengths ranging from 1.54-1.73 Å for certain coverages. On the other hand, O-H bond length values are 2.41 Å and 2.37 Å for 0.50 ML and 2 ML coverage respectively. Additionally, for 0.50 ML, the most stable configuration is when one H atom adsorbs on top of Zn and the other near the hollow site. At low coverage (0.25 ML and 0.50 ML), H prefers to interact with topmost layer Zn atoms resulting to shifts in the electronic bands relative to the pristine surface’s. In addition, at high coverage (1 ML and 2 ML), shifting of bands are observed and are mainly guided by Zn-H atom interaction for 1 ML and weak H-O atom interaction for 2 ML. The observed decrease in band gap as the coverage was increased from 1 ML to 2 ML is supported by the red shift in the absorption plot. However, for low H coverage adsorption, the optical plots deviate due to emergence of flat bands. Changes in electronic properties such as shifts in conduction band minimum (CBM) and decrease in measured band gap occur as guided by the interaction of adsorbed H atoms with the surface atoms and are supported with obtained optical plots. These findings present the tunability of Zn-terminated ZnO(0001) polar surface properties depending on H coverage.

Modification of microstructural, mechanical and optical properties with carbon ion irradiation in Y2SiO5 crystals

Yttrium orthosilicate Y2SiO5 crystals, a member of the silicate family, are versatile and multifunctional materials when doped with rare earth or transition metal ions. However, there have been limited investigations into the impact of ion irradiation on the crystal structure of Y2SiO5 crystals to date. In this paper, the effect of microstructure, mechanical and optical properties of Y2SiO5 crystal before and after different fluences of carbon ions irradiation was investigated utilizing complementary characterization techniques. The results indicate that carbon ion irradiation caused lattice disorder and damage, which resulted in structural deterioration and changes in optical properties, such as decrease in the optical band gap energy (from5.77 eV to 5.44 eV), changes in the effective refractive index (neff) which resulted in the formation of “well + barrier” type and “barrier” type waveguides. In addition, elastic modulus increased after carbon ion irradiation. The results will be helpful for understanding the damage study of the Y2SiO5 crystal with carbon ion irradiation and proving that ion beam techniques can be used for material modification.

Reveal mechanical and optical properties changes during prolonged skin stretching via in vivo continuous investigation

Skin expansion is a well-established technique in plastic surgery, and recent studies have highlighted its potential in promoting hair regeneration. This study aimed to explore how the mechanical and optical properties of skin change during a prolonged stretching process. A hybrid method was developed to assess, in vivo, the effects of an 8-day skin stretching protocol—previously used in hair regeneration research—on the dorsal skin of mice. This method combined mechanical and optical measurement systems. Tensile stress–strain curves were generated using a spring-based setup, while optical properties such as scattering and birefringence were analyzed with a polarimetry imaging system that incorporated the Mueller matrix (MM) and Mueller matrix polar decomposition (MMPD) methods. The results showed that Young's modulus increased from approximately 5 kPa on day 1 to 60–100 kPa by days 6–8, indicating collagen fiber straightening and increased stiffness. Optical analysis revealed greater anisotropy in both scattering and birefringence, as reflected by changes in MM elements and MMPD results. These changes suggest skin adaptation and regeneration, particularly within the first 24 h of stretching. Interestingly, alterations in optical properties closely mirrored changes in mechanical properties, pointing to a coordinated process of structural remodeling and functional adaptation in the skin. These findings offer valuable insights into skin remodeling and adaptation, which could guide future tissue engineering strategies.

Effects of chemical etching on surface structure and tribological behavior of silicate substrates

Abstract This study investigated the effect of chemical etching on the surface structure and tribological behavior of silicate substrates. Silicate surfaces were etched using a mixture of nitric acid (HNO3) and ammonium bifluoride (NH4HF2) for durations ranging from 1 to 60 min. The etched surfaces were characterized using optical microscopy, scanning electron microscopy, surface profilometry, water contact angle measurements, and UV–vis spectroscopy to evaluate the changes in surface morphology, roughness, wettability, and optical properties. Tribological performance was assessed using reciprocating ball-on-plate friction tests. The results showed that increasing the etching time resulted in the formation of microscale surface features, increased surface roughness, enhanced hydrophilicity, and reduced optical transmittance. The average friction coefficient decreased with an increase in the etching time up to 30 min, beyond which a slight increase was observed. The 1-minute etched specimen exhibited the best wear resistance with the narrowest wear track and the least material removal. The improved tribological performance was attributed to the formation of a stable transfer film, reduced real contact area, and entrapment of wear debris. This study highlights the potential of chemical etching as a technique to tailor the surface structure and tribological properties of silicate materials for various applications.

Vibrational, optical and elastic properties of Cs2AgBiX6 (X= Br, Cl) double perovskite materials: DFT, PL, Raman and Brillouin scattering studies

In this study, we explore the temperature-dependent Raman, photoluminescence (PL) and Brillouin spectroscopy, as well as Density Functional Theory (DFT) calculation results of Cs2AgBiBr6 and Cs2AgBiCl6 double perovskites. Single crystals of Cs2AgBiBr6 and Cs2AgBiCl6 were synthesized via a hydrothermal method. The lattice structure has been clearly defined, and the electronic band structures, validated by DFT calculations, are consistent with previously reported data. Optical properties calculated via DFT approach indicate superior energy storage capacity for Cs2AgBiBr6. Changes in optical properties at room temperature suggest potential suitability for specific applications, ranging from photovoltaics to lasers. Raman and Brillouin spectroscopy have revealed significant insights regarding the vibrational properties and atomic interactions within the materials, thereby contributing to a better understanding of the atomic interactions within the perovskite structures. Experimental data has highlighted anomalies in the Raman shifts, indicating the presence of a phase transition in Cs2AgBiBr6 at 115 K. However, no such phase transition was observed in Cs2AgBiCl6. This observation is further supported by Brillouin spectroscopy. PL measurements on Cs2AgBiBr6 revealed the presence of a low-temperature phase transition at 35 K. DFT calculations also provide detailed insights into the elastic properties of these perovskites, notably indicating superior mechanical strength for Cs2AgBiCl6. These findings will enhance the understanding of perovskite materials and expand their potential technological applications, especially in environments with varying thermal conditions

Nonlinear optical parameters and electronic properties of plasma polymerized methyl acrylate thin films

Plasma polymerized methyl acrylate (PPMA) thin films were fabricated on a borosilicate glass substrate at a plasma power of 28 W to study nonlinear optical parameters and electronic properties. X-ray Diffraction analysis confirmed the amorphous nature of the PPMA films, while Attenuated total reflectance Fourier transform infrared spectroscopy indicated monomer fragmentation due to plasma polymerization. Field emission scanning electron microscope images of the films display a water wave-like structure. PPMA films demonstrated thermal stability up to approximately 574 K in both N2 and air environments. The values of direct band gap energies increase from 3.30 to 3.41 eV with increasing film thicknesses, whereas the Urbach energy values show in an opposite manner. The Wemple-DiDomenico model was employed to analyze both the oscillator energies ranging from 5.54 to 6.44 eV and the dispersion energies ranging from 10.56 to 12.89 eV. The static linear refractive index showed typical dispersion behavior, with film thickness conforming to Moss's rule. The nonlinear refractive index and 2nd and 3rd order nonlinear susceptibilities decrease with increasing the studied films. The lattice dielectric constant values exceeded the high-frequency dielectric constant, indicating the presence of lattice vibrations and free carriers. Electronic parameters are fluctuating with increasing film thickness. The observed changes in nonlinear optical parameters and electronic properties highlight the potential of PPMA films for applications in photovoltaic and optoelectronics.

"Optical Properties and Translucency of ImplantSupported PEEK Crowns: Spectrophotometric Evaluation"

AIM- To evaluate the difference in optical properties and translucency parameters of implant supported PEEK crowns at different time intervals. MATERIAL AND METHODS: Optical properties and translucency parameters of implant supported PEEK crowns were assessed in 35 patients using spectrophotometer RESULT: Results revealed noticeable changes in translucency parameters and optical properties of implant supported PEEK crowns at 3 months. CONCLUSION- Our study on 35 patients on implant-supported PEEK crowns revealed that glazing improves surface roughness and opalescence, enhancing aesthetic appeal. Although, oral fluids containing intrinsic and extrinsic factors still adversely affect PEEK's color stability and surface quality

Optical Characterization of Coastal Waters with Atmospheric Correction Errors: Insights from SGLI and AERONET-OC

This study identifies the characteristics of water regions with negative normalized water-leaving radiance (nLw(λ)) values in the satellite observations of the Second-generation Global Imager (SGLI) sensor aboard the Global Change Observation Mission–Climate (GCOM-C) satellite. SGLI Level-2 data, along with atmospheric and in-water optical properties measured by the sun photometers in the AErosol RObotic NETwork-Ocean Color (AERONET-OC) from 26 sites globally, are utilized in this study. The focus is particularly on Tokyo Bay and the Ariake Sea, semi-enclosed water regions in Japan where previous research has pointed out the occurrence of negative nLw(λ) values due to atmospheric correction with SGLI. The study examines the temporal changes in atmospheric and in-water optical properties in these two regions, and identifies the characteristics of regions prone to negative nLw(λ) values due to atmospheric correction by comparing the optical properties of these regions with those of 24 other AERONET-OC sites. The time series results of nLw(λ) and the single-scattering albedo (ω(λ)) obtained by the sun photometers at the two sites in Tokyo Bay and Ariake Sea, along with SGLI nLw(λ), indicate the occurrence of negative values in SGLI nLw(λ) in blue band regions, which are mainly attributed to the inflow of absorptive aerosols. However, these negative values are not entirely explained by ω(λ) at 443 nm alone. Additionally, a comparison of in situ nLw(λ) measurements in Tokyo Bay and the Ariake Sea with nLw(λ) values obtained from 24 other AERONET-OC sites, as well as the inherent optical properties (IOPs) estimated through the Quasi-Analytical Algorithm version 5 (QAA_v5), identified five sites—Gulf of Riga, Long Island Sound, Lake Vanern, the Tokyo Bay, and Ariake Sea—as regions where negative nLw(λ) values are more likely to occur. These regions also tend to have lower nLw(λ) values at shorter wavelengths. Furthermore, relatively high light absorption by phytoplankton and colored dissolved organic matter, plus non-algal particles, was confirmed in these regions. This occurs because atmospheric correction processing excessively subtracts aerosol light scattering due to the influence of aerosol absorption, increasing the probability of the occurrence of negative nLw(λ) values. Based on the analysis of atmospheric and in-water optical measurements derived from AERONET-OC in this study, it was found that negative nLw(λ) values due to atmospheric correction are more likely to occur in water regions characterized by both the presence of absorptive aerosols in the atmosphere and high light absorption by in-water substances.

Comprehensive analysis of organic dye doped metal-coordinated single crystals: A study of structural, optical, thermal, dielectric, piezoelectric and mechanical characteristics

Organic dye can induce positive changes in optical, mechanical and electrical properties of semi-organic single crystals. Single crystals of pure and 0.01 mol% SSY dye doped ZTS are grown from a slow evaporation solution technique. The structural properties of pure and SSY-dyed ZTS crystals are characterized using SCXRD and PXRD, confirming the maintenance of crystallinity and incorporation of dye molecules within the host lattice of ZTS crystal. Both ZTS crystals belong to orthorhombic crystal system with space group Pca21. The refined lattice parameters and cell volume of present pure ZTS crystal are a = 11.1723 Å, b = 7.7989 Å, c = 15.5357 Å, α = β = γ = 90°, V = 1353.6762 Å3. The intensity of all Raman peaks in ZTS is enhanced by the incorporation of dye. Optical spectroscopic UV–visible and photoluminescence techniques highlight the comparative studies of light absorption, energy bandgap, optical constants and fluorescence emission. An increment of 0.05 eV in optical bandgap is observed in dyed ZTS. The dielectric properties with variation in frequency range (23 Hz–10 MHz) at different temperature range (30–100 °C) are evaluated through impedance spectroscopy, showing an increase in dielectric constant around 15 % and reduction in dielectric loss, indicating potential for improved performance in electronic applications. A significant enhancement is observed in the piezoelectric coefficient (d33) in dyed ZTS single crystals. The d33 value of ZTS is increased from 2.75 to 2.95 pC/N by the doping of organic dye. Vickers micro-hardness tester is used to know the mechanical strength through micro-indentation, which illustrated an increase in the hardness nature of dyed ZTS single crystals. These findings provide a foundation for the future development of ZTS-based materials for technological applications, offering a promising route for the advancement of functional materials in the domain of piezoelectric and optoelectronic technologies.

Nanosilicon Stabilized With Ligands: Effect of High‐Energy Proton Beam on Luminescent Properties

ABSTRACTSilicon nanopowders with nitrogen heterocyclic carbene (NHC) and butyl as stabilizing ligands were synthesized by bottom‐up chemical methods. Transmission electron microscopy (TEM) was used to obtain nanoparticle size distribution with 1.8–2.5‐nm average diameter. Optical characteristics (photoluminescence [PL] and infrared [IR] absorption spectra) of samples were investigated as fabricated and on different steps of irradiation by high‐energy 22.5‐MeV protons. The PL spectral changes are slightly different for two cases, but in general, we can see a decrease in luminescence amplitude with fluence growth up to 4·1014 cm−2, mainly for NHC‐stabilized nanosilicon. Main mechanisms of radiation‐induced changes in nanosilicon sample optical properties are discussed by the joint use of PL and IR spectra analysis.

Development of Readily Available & Robust High Heat Flux Gardon Gauges

Concentrated solar power (CSP) technologies deliver concentrated solar energy as a heat source to industrial processes, power generation cycles, and chemical cycles. CSP systems require accurate and reliable high flux measurements, and next generation CSP systems will require flux measurement up to 1000 W/cm2. Existing flux measurement devices do not comprehensively meet the flux rating, cycle life, cost, and lead-time needs of stakeholders, necessitating the development of an improved flux sensor. In this study, Sandia National Laboratories (SNL) partnered with Hukseflux Thermal Sensors to develop a low-cost, short lead-time, and robust flux sensor rated to 250 W/cm2. Three prototype circular foil gauge designs were assessed for performance at the National Solar Thermal Test Facility (NSTTF) at SNL. Each gauge design measured flux up to 250 W/cm2 with <5% measurement error. Following baseline error quantification, gauges were exposed to flux above 500 W/cm2 to assess gauge failure mechanisms. Gauges physically survived >500 W/cm2 flux exposure, but measurement error was found to increase after foil coatings reached 400 °C. The results of this study suggest that coating optical properties change at excessive temperatures and that foil coating temperature, rather than heat flux level, dictates the acceptable gauge measurement range.

Formation and radiolytic alteration of uraniferous solid bitumen related to hydrothermal base-metal mineralization in the Bytíz deposit, Příbram district, Czech Republic

The Bytíz deposit is a part of the Příbram uranium and base-metal ore district. It is an example of a vein-type deposit with polyphase hydrothermal mineralization. Samples of uraniferous solid bitumen from Bytíz with U content up to 38 wt% are characterized petrologically, geochemically, and mineralogically using EPMA, Raman and infrared microspectroscopy. The bitumen-bearing samples consist of base-metal sulfides: galena, sphalerite, pyrite, chalcopyrite, and also minor amounts of tetrahedrite, stibnite, and acanthite, associated with Mn-bearing calcite, quartz and silicates (chlorite, muscovite). Solid bitumens were found in the form of small veins and droplets, and roundish to irregular accumulations, in association with uraninite and carbonate veins.U-bearing minerals in the studied samples are represented by uraninite and more rarely by coffinite. Three generations of uraninite in association with solid bitumen were distinguished: 1. spherulites and large grains, filled with organic phase in the cracks; 2. as a part of complex textures inside areas with organic matter; in this case, the uraninite was assumed to have been remobilized; and 3. small inclusions in the latest calcite veins.More than 80 vol% of the solid bitumen from the vein fillings appeared to be radiolytically altered. Radiolytic alteration results in changes in optical properties and in composition, and in the formation of various textures around uraninite grains: halos, and irregular textures from simple massive to flow, dendritic, and fractured to a very complex morphology. The random reflectance values of unaltered mineral-free bitumen range from 0.45% to 0.99%, while in the radiolytically altered bitumen the average reflectance values are higher, from approximately 1.72% to 3.44%.The degree of graphitization of the organic matter was assessed by infrared micro-spectroscopy. Spectral maps show significant destruction changes of the aliphatic CH bonds and an increase in the content of oxygen functional groups in the vicinity of U minerals.On the element distribution maps, obtained by EPMA, the distribution of S, U, Pb and other elements across solid bitumen in the vicinity of uraninite and coffinite has a very heterogeneous character. An elevated content of sulfur in bitumen was also found, as well as a clear interdependence between S and C. It is suggested that the presence of sulfur in solid bitumen may result in ‘clouding’ of the solid bitumen with tiny stibnite grains. The dark rims of the halos observed under the optical microscope may be due to an elevated U content at the rims around the uraninite.Based on analysis of complex textural relationships of the solid bitumens with coexisting minerals, the formation of solid bitumen in association with uraninite is therefore assumed to relate to several stages of the influx of hydrothermal fluid. The temperature of the fluid, associated with bitumen formation was estimated to be up to 270 °C, according to chlorite thermometry.

Stable optical response during electron–phonon equilibration in laser-excited gold

We study the optical response of solid gold driven by ultrashort pulses of visible light by tracking the conduction band density and damping rates. While we find rapid changes in optical properties during and shortly after the laser excitation, we obtain an almost unchanged reflectivity during the stage of electron–phonon temperature equilibration. These predictions are in good agreement with experimental data and exhibit a strong compensation of damping mechanisms as a source for the stable response, although electron and ion temperatures change significantly. Considering the complex interplay of damping processes in solid gold, our model gives a more fundamental interpretation of optical measurements than existing approaches.

Preparation and properties of strong gamma ray shielding and irradiation resistant glass

CeO2 doped lead silicate glasses samples were prepared by high temperature melting method. The structural, thermal and optical properties of the glasses were characterized by density, expansion coefficient, XPS and ultraviolet-visible spectroscopy. Additionally, the related theoretical work was carried out for verification. The changes in structure and optical properties of the glass before and after irradiation were investigated. The influence mechanism of different content of CeO2 (PbO) on the structure and properties of shielding glass was discussed. By comparing the three transmittance conversion formulas, it is found that the characteristic coefficient can be further calculated if the transmissivity with varied thicknesses is known. This coefficient method allows for accurate calculation of transmittance for glasses with arbitrary thicknesses while demonstrating experimental validation. The accuracy improves as more measured values of transmittance for glasses with different thicknesses are obtained and as more iterations of characteristic coefficients are performed. This method is suitable for both scientific research and production practice. The test results show that the transmittance of the glass with 45 wt% PbO and 2 wt% CeO2 content is above 60 % in the wavelength range of 400–800 nm before irradiation and decreased less than 10 % after irradiation. The measured shielding rate of 60Co gamma rays can reach more than 51 %. The calculated transmittance of 300 mm thickness glass is greater than 50 %. The superior gamma ray shielding capability along with its radiation resistance make this glass provide key support for window materials used in various fields such as nuclear industry, aerospace, military and medicine.

Electrochemically Driven Optical Dynamics of Reflectin Protein

Neuronally triggered phosphorylation monotonically and cyclably drives the assembly of reflectin proteins, resulting in the fine-tuning of colors reflected from specialized skin cells in squid for camouflage and communication. Reflectin has been found as the primary constituent within stacks of plasma membrane-bounded platelets (iridosomes) found in iridocyte cells. This cellular ‘superstructure’ consisting of alternating layers of high refractive index platelets and low refractive index extracellular space effectively functions as a biological Bragg reflector. In vivo, reflectin assembly triggers osmotic dehydration of the Bragg lamellae, reducing the platelet thickness, and thus dynamically tuning the color of the reflected light. Our previous study has shown that electrochemistry, used as in vitro surrogate for in vivo phosphorylation-mediated charge neutralization, triggers voltage-calibrated and cyclable control of the rate and size of reflectin assembly. This process is highly similar to the observed physiological behavior. Here, we demonstrate for the first time that electrochemical reduction enables tunable and reversible control of refractive index and thickness of a reflectin thin film formed by drop-casting on a conductive substrate to mimic the platelet structures in cephalopod iridophores. Electrochemically driven in situ spectroscopic ellipsometry was developed to trigger and simultaneously analyze the change in optical properties of the reflectin film and thus further elucidate the color-changing mechanisms in squid skin. Our results confirm the hypothesis that the extent of charge neutralization controlled by applied voltage plays a role in calibrating the water volume fraction within platelets and the resulting optical features. This work opens new means for analyzing the biophysical mechanisms regulating color change by reflectin assembly, designing advanced functional materials and devices, and bridging the biotic–abiotic interface.

Thermal Control Coatings Flown on Low Earth Orbit Materials Experiments

Coatings developed by AZ Technology were exposed to the space environment on two different platforms and analyzed for optical property changes. These coatings were primarily for passive thermal control, but electrostatic dissipative coatings and marker coatings were also flown. Some materials were flown on the Materials on International Space Station Experiment (MISSE) 15th and 16th flights, and some were flown on the Materials Exposure and Technology Innovation in Space (METIS) first flight. The MISSE and METIS flights were both in low Earth orbit but had very different results. Space environmental and molecular contamination effects on optical properties are reviewed. Future experiments, including the Regolith Adherence Characterization flight to the moon, are discussed.

Excited‐State Dynamics and Optical Properties of Silica Under Ultrafast Laser Irradiation

AbstractExcited by intense infrared ultrafast light pulses, a wide bandgap material undergoes nonlinear ionization, generating a high density of free electrons in conduction states. As a result, the electronic band structure is critically modified and the bandgap shrinks. This induces rapid changes in optical properties, dramatically affecting the absorption spectrum during light coupling to the dielectric surface or during nonlinear propagation inside the bulk. This study analyzes the structural behavior and the modification of the optical properties of laser‐excited silica glass at the molecular cluster level through first‐principles simulations. Employing density functional theory and the GW approximations for band structure under nonequilibrium conditions, alongside the Bethe–Salpeter equation, the dynamics of the optical properties of fused silica are comprehensively explored. The behavior of excited fused silica in a wide photon energy range (from a few to 20 eV) is thus predicted. Laser‐induced electron excitation triggers a redistribution of charges between oxygen and silicon atoms, accompanied by a significant increase in electronic pressure, local atomic structure rearrangement, and material expansion. Molecular dynamics simulations offer a temporal perspective on the excited state dynamics, unveiling the intricate interplay between electronic and atomic effects on bandgap evolution. The analysis sheds light on excitonic resonances, intraband and interband transitions in fused silica under ultrafast laser irradiation, providing valuable insights into its excited state behavior and optical properties.

Transparent bamboo as a replacement for glass: Effects of lignin decolorisation methods on weatherability

Transparent bamboo proved to be a promising substitute for glass due to its high light transmittance and excellent mechanical properties. Nevertheless, it was susceptible to outdoor weathering, which negatively affected its physical and mechanical properties. In this study, two decolorisation methods, namely the delignification method and the lignin modification method, were used to produce transparent bamboos with epoxy resin, referred to as DL-TB and LM-TB, respectively. The changes in surface color, optical and mechanical properties, wettability, thermal stability, and thermal insulation properties of transparent bamboo during accelerated UV weathering were evaluated. Additionally, the deterioration mechanism of DL-TB and LM-TB was investigated. The findings revealed that DL-TB demonstrated better transparency and mechanical properties than LM-TB, although it exhibited lower thermal insulation properties. Furthermore, DL-TB demonstrated enhanced color stability and higher hydrophobicity on weathered surfaces than LM-TB. Unexpectedly, the tensile properties of both two transparent bamboos significantly improved after weathering, especially for LM-TB, which was due to the EP post-curing and the formation of more hydrogen bonds between lignin and EP. These observations revealed that lignin played a key role in the photodegradation process of transparent bamboo, but further attempts should be made in future studies to improve its color stability.