In the current research, the silicon carbon oxynitride (SiCON) thin film was deposited on the silicon (Si) substrate by radio frequency (RF) reactive magnetron sputtering method. To comprehensively assess the impact of nitrogen flux rate on thin film characteristics, a suite of advanced analytical methods was utilized. The GIXRD analysis confirmed that the SiCON thin film is amorphous in structure. Additionally, Raman spectroscopy detected no graphite nanocrystals within the film. Ellipsometry measurements further showed that the refractive index of the thin films rises with increased nitrogen flux in the reactive gas, indicating a direct correlation between nitrogen concentration during deposition and optical properties. Based on the designs made with McLeod\'s software, the amount of reflection can be reduced up to 5.7 % at the wavelength of 4 μm and up to 8.5 % in the wavelength range of 3-5 μm for an optimal thickness thin film. The atomic force microscopy (AFM) examination revealed that the surface roughness of the thin films decreases as the nitrogen flux in the reactive gas mixture increases. Additionally, measurements of the water contact angle (WCA) indicated that the SiCON thin films exhibit a hydrophilic state.

The change in composition and pressure, both of which lead to new desired properties by altering the structure, is particularly important for improving device performance. Given this, we focused here on the mechanical, elastic, and optoelectronic characteristics of the Cd0.75Zn0.25Se alloy using density functional theory at various pressures from 0 GPa to 20 GPa. It is found that the bulk modulus of the material rises with increasing pressure and exhibits mechanical stability as well as cubic symmetry. In addition, the increased pressure leads to a rise in the direct bandgap energy of the material from 2.03 eV to 2.48 eV. The absorption coefficient of the alloy also increases as the pressure increases, where the effective range of absorption covers the broad spectrum of light in the visible range from orange to cyan. This is due to the electronic transitions caused by the altered pressure. The optical parameters, including optical conductivity, extinction coefficient, reflection, and refractive index, are also analyzed under the influence of pressure. Based on this research, effective applications of the Cd substituted Zn-chalcogenides (CdZnSe) alloys in the fields of optoelectronics and photovoltaics are outlined, especially concerning fabricating solar cells, photonic devices, and pressure sensors for space technology.

This study investigates the development of novel nanocomposite films based on a blend of polyethylene oxide (PEO) and polyvinyl alcohol (PVA) loaded with varying weight percentages of copper cobaltite nanoparticles (CuCo2O4 NPs). The primary objective was to fabricate these nanocomposites using a solution casting technique and explore the influence of CuCo2O4 content on their structural, optical, electrical, and dielectric properties. Spinel-type CuCo2O4 NPs were synthesized via the hydrothermal method and incorporated into the PEO/PVA blend. X-ray diffraction (XRD) analysis revealed the transformation of the polymer matrix towards an amorphous state with increasing CuCo2O4 content. UV-Vis spectroscopy studies demonstrated a decrease in both the direct and indirect band gaps of the nanocomposites, suggesting potential applications in optoelectronic devices. Impedance spectroscopy measurements revealed a significant enhancement in ionic conductivity (three orders of magnitude higher than the pristine blend) for the nanocomposite film containing 1.8 wt% CuCo2O4. The real permittivity (ε\') and imaginary permittivity (ε″) of the polymer nanocomposites exhibited a decrease with increasing frequency due to the interplay of various polarization mechanisms. Notably, incorporating 1.8 wt% CuCo2O4 nanoparticles led to a remarkable improvement in energy density compared to the pristine blend. Additionally, a significant decrease in the potential barrier was observed. These findings demonstrate the successful fabrication of PEO/PVA-CuCo2O4 nanocomposite films with enhanced optical, electrical, and dielectric properties. The observed improvements suggest promising applications for these materials in energy storage devices and potentially in optoelectronic devices like light-emitting diodes.

This original work investigated the optical properties and Monte-Carlo (MC) based simulation of light propagation in the flavedo of Nanfeng tangerine (NF) and Gannan navel orange (GN) infected by Penicillium italicum. The increase of absorption coefficient (μa) at around 482 nm and the decrease at around 675 nm were both observed in infected NF and GN during storage, indicating the accumulation of carotenoids and loss of chlorophyll. Particularly, the μa in NF varied more intensively than GN, but the limited differences of reduced scattering coefficient (μs\') were detected while postharvest infection. Besides, MC simulation of light propagation indicated that the photon packets weight and penetration depth at 482 nm in NF were reduced more than in GN flavedo, while there were almost no changes at the relatively low absorption wavelength of 926 nm. The simulated absorption energy at 482 nm in NF and GN presented more changes than those at 675 nm during infection, thus could provide better detection of citrus diseases. Furthermore, PLS-DA models can discriminate healthy and infected citrus, with the accuracy of 95.24 % for NF and 98.67 % for GN, respectively. Consequently, these results can provide theoretical fundamentals to improve modelling prediction robustness and accuracy.

BACKGROUND: The aim of this work is to use first principles calculations to examine the effects of different mechanical strains on the optoelectronic and photocatalytic capabilities of the 2D/2D nanoheterostructure of AlN/GaN. By utilizing the lmBJ (Meta-GGA) and PBEsol (GGA) functional, the bandgap of the nanoheterostructure is calculated and found to be 4.89 eV and 3.24 eV. Simulated 2D AlN/GaN nanoheterostructure exhibits exceptional optical and electronic characteristics under applied biaxial tensile and compressive strains. The band gap changes from 4.89 to 3.77 eV, while the energy gap nature transitions from direct to indirect during tensile strain fluctuations of 0% to 8%. Strain is also found to have a significant effect on the optical absorption peaks. And a 0-8% rise in tensile strain causes the initial absorption peak of the 2D AlN/GaN nanoheterostructure to shift from 4.88 to 4.20 eV, which results in a 14% red shift in photon energy for every 2% change in strain. Furthermore, the optimum bandgap and band edge positions of the 2D AlN/GaN nanoheterostructure enable the water redox process to produce hydrogen and oxygen for wide range of pH. Thus, modification via strain may be an effective method for altering the optical as well as electronic characteristics of a 2D AlN/GaN nanoheterostructure, and this study may pave the way for new applications of this material in optoelectronic devices in the future.
METHODS: In the current work, density functional theory is used to explore every attribute of the 2D AlN/GaN nanoheterostructure. To characterize the electronic exchange-correlation, we used the PBEsol functional. In order to prevent any interlayer contact between periodicity of images, a vacuum is produced along the z-direction of approximately 10 Å. To increase the precision of bandgap prediction, the electronic and optical characteristics were computed using the meta-GGA lmBJ functional. To account for interlayer van der Waals interactions, nanoheterostructure computations were performed using the DFT-D3 functional.

Herein, we fabricated nanoscale 2D CeO2 sheet structure to develop a stable resistive gas sensor for detection of low concentration (ppm) level formaldehyde vapors. The fabricated CeO2 nanosheets (NSs) showed an optical band gap of 3.53 eV and cubic fluorite crystal structure with enriched defect states. The formation of 2D NSs with well crystalline phases is clearly observed from HRTEM imag-es. The NSs have been shown tremendous blue-green emission related to large oxygen defects. A VOC sensing device based on fabricated two-dimensional NSs has been developed for the sensing of different VOCs. The device showed better sensing for formaldehyde compared with other VOCs (2-propanol, methanol, ethanol, and toluene). The response was found to be 4.35, with the response and recovery time of 71 s and 310 s, respectively. The device showed an increment of the recovery time (71 s to 100 s) with the decrement of the formaldehyde ppm (100 ppm to 20 ppm). Theoretical fit-tings provided the detection limit of formaldehyde ≈ 8.86 ± 0.45 ppm with sensitivity of 0.56 ± 0.05 ppm-1. The sensor device showed good reproducibility with excellent stability over the study period of 135 days, with a deviation of 1.8 % for 100 ppm formaldehyde. The average size of the NSs (≈ 24 nm) calculated from HRTEM observation showed lower value than the calculated Debye length (≈ 44 nm) of the charge accumulation during VOCs sensing. Different defect states, interstitial and surface states in the CeO2 NSs as observed from the Raman spectrum and emission spectrum are responsible for the formaldehyde sensing. This work offers an insight into 2D semiconductor-based oxide materi-al for highly sensitive and stable formaldehyde sensors. .

CaWO4 nanoparticles were obtained by facile mechanochemical synthesis at room temperature, applying two different milling speeds. Additionally, a solid-state reaction was employed to assess the phase composition, structural, and optical characteristics of CaWO4. The samples were analyzed by X-ray diffraction (XRD), transition electron microscopy (TEM), and Raman, infrared (IR), ultraviolet-visible (UV-Vis) reflectance, and photoluminescence (PL) spectroscopies. The phase formation of CaWO4 was achieved after 1 and 5 h of applied milling speeds of 850 and 500 rpm, respectively. CaWO4 was also obtained after heat treatment at 900 °C for 12 h. TEM and X-ray analyses were used to calculate the average crystallite and grain size. The Raman and infrared spectroscopies revealed the main vibrations of the WO4 groups and indicated that more distorted structural units were formed when the compound was synthesized by the solid-state method. The calculated value of the optical band gap of CaWO4 significantly increased from 2.67 eV to 4.53 eV at lower and higher milling speeds, respectively. The determined optical band gap of CaWO4, prepared by a solid-state reaction, was 5.36 eV. Blue emission at 425 (422) nm was observed for all samples under an excitation wavelength of 230 nm. CaWO4 synthesized by the solid-state method had the highest emission intensity. It was established that the intensity of the PL peak depended on two factors: the morphology of the particles and the crystallite sizes. The calculated color coordinates of the CaWO4 samples were located in the blue region of the CIE diagram. This work demonstrates that materials with optical properties can be obtained simply and affordably using the mechanochemical method.

Currently, the most reliable approach to reconstruct optical properties, namely absorption coefficient, reduced scattering coefficient, scattering coefficient and asymmetry factor, of turbid media is through inverse Monte Carlo simulation. To determine these optical properties, three measurements are required: total transmission, total reflection and collimated transmission. However, the accurate determination of the collimated transmission is very difficult. To overcome the difficulty of measuring the collimated transmission, it is proposed to measure the total transmission and total reflection of the same sample with two different thicknesses instead. To prove this alternative solution, machine learning is used to prove that the repeated measurement for two different thicknesses carries all the necessary information. As a result, all four optical properties can be measured with high accuracy, particularly for interpolation problems where the test data fall within the range of the training data. For extrapolation problems, high accuracy can be achieved in the determination of at least the absorption coefficient, reduced scattering coefficient and scattering coefficient. Hence, these results allow that in the future, an easier and therefore more precise reconstruction of the optical properties is possible, potentially even with inverse Monte Carlo simulations as the current standard.

Cesium lead halide perovskite (CsPbX3; X = Cl, Br, I) nanocrystals showing intense band-edge emission and high photoluminescence quantum yield are known to be a potential candidate for application in optoelectronic devices. However, controlling toxicity due to the presence of Pb2+ in lead-based halide perovskites is a major challenge for the environment that needs to be tackled cautiously. In this work, we have partially replaced Pb2+ with Mn2+ ions in the CsPb(Cl/Br)3 nanocrystals and investigated their impact on the structural and optical properties. The Rietveld refinement shows that CsPbCl2Br nanocrystals possess a cubic crystal structure with Pm3 ̅m space group, the Mn2+ doping results in the contraction of the unit cell. The CsPb(Cl/Br)3: Mn nanocrystals show a substantial change in the optical properties with an additional emission band at ~588 nm through a d-d transition, changing the emission color from blue to pink. Here, a didodecyldimethylammonium bromide (DDAB) ligand that triggers both anion and ligand exchange in the CsPb(Cl/Br)3: Mn nanocrystals have been used to regulate the exchange reaction and tune the emission color of halide perovskites by changing the peak position and the PL intensities of band-edge and Mn2+ defect states. We have also shown that oleic acid helps in the desorption of oleylamine capping from the CsPb(Cl/Br)3: Mn nanocrystal surfaces and DDAB, resulting in the substitution of Cl¯ with Br¯ as well as provides capping with shorter branched length ligand which led to increase in the overall PL intensity by many folds.

UNASSIGNED: Spatial frequency domain imaging (SFDI) applies patterned near-infrared illumination to quantify the optical properties of subsurface tissue. The periocular region is unique due to its complex ocular adnexal anatomy. Although SFDI has been successfully applied to relatively flat in vivo tissues, regions that have significant height variations and curvature may result in optical property inaccuracies.
UNASSIGNED: We characterize the geometric impact of the periocular region on SFDI imaging reliability.
UNASSIGNED: SFDI was employed to measure the reduced scattering coefficient ( μ s \' ) and absorption coefficient ( μ a ) of the periocular region in a cast facial tissue-simulating phantom by capturing images along regions of interest (ROIs): inferior temporal quadrant (ITQ), inferior nasal quadrant (INQ), superior temporal quadrant (STQ), central eyelid margin (CEM), rostral lateral nasal bridge (RLNB), and forehead (FH). The phantom was placed on a chin rest and imaged nine times from an \"en face\" or \"side profile\" position, and the flat back of the phantom was measured 15 times.
UNASSIGNED: The measured μ a and μ s \' of a cast facial phantom are accurate when comparing the ITQ, INQ, STQ, and FH to its flat posterior surface. Paired t tests of ITQ, INQ, STQ, and FH μ a and μ s \' concluded that there is not enough evidence to suggest that imaging orientation impacted the measurement accuracy. Regions of extreme topographical variation, i.e., CEM and RLNB, did exhibit differences in measured optical properties.
UNASSIGNED: We are the first to evaluate the geometric implications of wide-field imaging along the periocular region using a solid tissue-simulating facial phantom. Results suggest that the ITQ, INQ, STQ, and FH of a generalized face have minimal impact on the SFDI measurement accuracy. Areas with heightened topographic variation exhibit measurement variability. Device and facial positioning do not appear to bias measurements. These findings confirm the need to carefully select ROIs when measuring optical properties along the periocular region.