Papers by Keyword: Optical Properties

Abstract: In this study, detailed investigations of the structural, electronic, and optical properties of two-dimensional silicene quantum dots (SiQDs-2D) were carried out using first-principles calculations within the framework of density functional theory (DFT). The SiQDs-2D structure was constructed from 13 Si atoms arranged in a hexagonal lattice and passivated by 9 H atoms to enhance stability. The cohesive energy was calculated to be about –2.986 eV, confirming the dynamical stability of the system. The optimized geometry shows that the Si–Si bond lengths are approximately 2.247 Å (nearest neighbor), 3.637 Å (next-nearest neighbor), and 4.275 Å (opposite sites in a hexagon), with an average bond angle of 108.05° and a buckling height of about 0.8 Å. The electronic band structure and density of states (DOS) indicate that SiQDs-2D exhibits semiconducting behavior with a narrow HOMO–LUMO gap, strongly influenced by edge effects and hydrogen passivation. The charge density distribution shows that the HOMO states are mainly localized at the edges, while the LUMO states are more delocalized across the lattice, reflecting unique electronic transition mechanisms in the system. In terms of optical properties, SiQDs-2D presents strong absorption in the ultraviolet region (peak at ~5 eV) with an absorption coefficient of about 10⁸ m⁻¹, accompanied by a low reflectivity in the visible region. The real and imaginary parts of the dielectric function reveal the presence of intrinsic plasmon resonances in the range of 5–6 eV, while the JDOS confirms the role of dominant electronic transitions in the UV region. These results not only demonstrate the stability and unique electronic–optical features of SiQDs-2D but also highlight their potential applications in optoelectronic devices, UV sensors, and ultraviolet shielding materials

Abstract: This study compares the printability, optical, and mechanical properties of two types of coated papers: Magno Satin (MS) and Art Carton (AC). The evaluation includes grammage, thickness, bulk, brightness, opacity, Cobb60 value, oil penetration, tensile properties, tearing strength, and printability using offset ink. Printability tests measured optical density, CIE Lab* values, hue error, and grayness with varying ink film thicknesses from 0.8 to 9.6 microns. The results indicate that MS offers higher brightness and optical density, making it ideal for vibrant, high-quality printing. MS also demonstrated lower Cobb₆₀ value compared to AC, indicating superior water resistance. Additionally, MS exhibited higher tensile strength and stiffness, suitable for applications requiring rigidity, such as brochures. Oil penetration values for both papers were comparable, ensuring effective ink transfer. In contrast, AC showed greater tear strength, tensile energy absorption, and elongation, making it more suitable for packaging due to its robustness and flexibility. The optimal ink film thickness for both papers was around 8.0 microns, beyond which optical density improvements were minimal, and print quality declined due to over-inking. Overall, MS excels in applications requiring superior color vibrancy, detail, and water resistance, while AC is ideal for packaging with its durability and flexibility. Selecting the appropriate paper type based on specific printing requirements ensures optimal print quality and material efficiency.

Abstract: The o-phenanthroline-acyl-amino acid praseodymium complex (Pr [CH₃(CH₂)₄CO NHC H(CH₃)COO]₃ꞏphen) has been synthesized by an in-solution chemical reaction method using H(hex-ala) and 1,10-phenanthroline (phen) as ligands with a view to obtaining rare-earth organic complexes with good optical properties. The molecular structure of the praseodymium complex was determined using CHN elemental analysis, ¹³C NMR testing, and FT-IR spectroscopic testing. We also perform wide-angle and small-angle XRD diffraction wave analysis, polarization microscopy observation, light absorption testing, fluorescence spectral analysis, fluorescence lifetime analysis, and fluorescence variable temperature spectral analysis. The results indicate that the introduction of the auxiliary ligand phen results in a periodic short-range ordered structure and better crystallinity of Pr (hex-ala)₃ꞏphen, which exhibits strong optical anisotropy in the molten state. Good light absorption in the UV-visible region (200 nm - 420 nm), switching from ligand luminescence to a rare earth centered luminescence mechanism, and photoluminescence shifting from the blue to the green region. High fluorescence intensity in the visible and near-infrared regions, good fluorescence lifetime (0.76 µs), and good thermal stability in the range of 25 °C - 200 °C.

Abstract: In this paper, the mechanical, elastic, electronic and optical properties of thallium based-perovskites TlSnX₃ (X = F, Cl, Br and I) were investigated using the first-principles calculations. The elastic parameters calculations show that the perovskites are ductile, anisotropic, and mechanically stables. The cohesive energy calculations indicate that the evaluated perovskites are thermodynamically stable. Moreover, the band calculations with HSE06 method reveal that all perovskites TlSnX₃ (X = F, Cl, Br and I) present a semiconductor feature. Further, the optical properties such as reflectivity, refractive index, extinction and absorption coefficients have been calculated and compared for all perovskites compounds. Interestingly, the found results show that the absorption coefficient α(ω) in the visible and infrared regions reaches high values of 1.02, 1.19, 1.14 and 1.03 × 10⁶ cm^-1 for TlSnI₃, TlSnBr₃, TlSnCl₃ and TlSnF₃ , respectively. These results suggest that the heavy thallium perovskites TlSnX₃ (X = F, Cl, Br and I) have potential for optoelectronic applications.

Abstract: In this study beads like nanoparticles of manganese oxide with different doping of iron concentrations from 2% to 10% were deposited on ultrasonically cleaned glass substrate by chemical bath deposition technique. Different analytical techniques including XRD, SEM, DRS and VSM were utilized to analyze the structure, morphology, optical and magnetic properties. XRD analysis confirms the crystallite size of Fe-MnO₂ were between 13.70 nm to 46.46 nm, morphological examination indicated that Fe-MnO₂ have cubic and beads-like structures. SEM have revealed the average grain size of 613.3 nm and non-uniform deposition of thin film, DRS analysis confirms that pure MnO has band gap energy 2.90 eV and is decreased with increasing concentration of iron i.e shifted towards lower band gap energy semiconductor materials, VSM reveals that magnetization increases with increase in iron concentration. The best properties were obtained at 6% iron doping because, with further increase in doping concentration, the structure started to distort.

Abstract: The low-temperature solid-state method is utilized to prepare Cs₃Cu₂I₅ phosphors powder by using the cesium iodide (CsI) and cuprous iodide (CuI) as the raw materials. The phase structures of samples were investigated by using X-ray spectrum and steady-state fluorescence spectrometer. The experimental results show that all of samples were crystallized in the orthorhombic structure with pnma space group at the annealing temperature of 100-400°C. Cs₃Cu₂I₅ phosphors exhibits a strong blue photoluminescence emission with peak at 440nm under excitation at 310nm. With the increase of the annealing temperature in the range of 100-400°C, the photoluminescence quantum yield (PLQY) of Cs₃Cu₂I₅ powder achieved the 79.95%. It is revealed that the prepared Cs₃Cu₂I₅ powder phosphors potentially have the promising application in the blue light emitting materials.

Abstract: In this work, we investigate the use of reflectance spectroscopy as an accurate, fast, and non-destructive method for measuring the thickness of transparent layers, such as SiO₂, with thicknesses below 200 nm for microelectronic applications. To this end, we fabricated different oxides and analyzed their reflectance spectra using reflectance spectroscopy. The results were compared to theoretical reflectance spectra to validate the method. We introduce key factors to ensure accurate measurement by modeling the reflectance spectra of thin oxide layers with thicknesses ≥ 15 nm on 4H-SiC using the transfer matrix method (TMM).

Abstract: The 45S Bioactive glass-ceramic (BG) and Chromium (Cr)-doped BG materials were successfully produced in this study. XRD, FTIR, and ICP-MS techniques were used to characterize the prepared materials. The XRD testing showed that all samples contained pure BG. Increased Cr ion inclusion shifted the BG diffraction peaks to a lower value of 2 Theta and increased crystallinity. FTIR was used to detect Si-O, P-O, and Ca-O functional groups. Cr ions steadily decreased the Ca-vibration mode area. The ultraviolet-visible spectrophotometry was used to measure the optical characteristics of pure and Cr BG-doped materials. The Cr-doped BG was green in colour, whereas the lab-synthesized BG was white. Two additional bands formed at 433 and 615 nm when Cr ions were doped into the BG structure. These bands may be caused by ⁴A₂ → ⁴T₁ and ⁴A₂ → ⁴T₂ electronic d-d transitions. The findings show that biomedical applications may exist for fluorescent probes manufactured from Cr-BG materials.

Abstract: Nanoscale mixed ferrites with a spinel structure are highly versatile materials widely employed across diverse fields, including engineering, biomedicine, and ecology. This study explores the influence of pH on the structure, morphology, electrophysical, and mechanical properties of CuFe₂O₄ spinel, synthesized using the sol-gel self-combustion method. The investigation reveals that the pH level significantly impacts the structure formation, even at the gel formation stage, thereby shaping the subsequent structure and properties of the synthesized ferrite. X-ray diffraction (XRD) analysis demonstrates that the dominant phase (>90%) corresponds to the cubic spinel phase with the chemical formula CuFe₂O₄, belonging to the Fd3m space group. Notably, the pH of the reaction medium exerts a profound influence on the distribution of iron and copper ions within the octahedral and tetrahedral sublattices of the spinel structure. This variation in cationic distribution manifests in notable changes in the synthesized ferrite's magnetic, mechanical, and degradation properties. Furthermore, the study delves into the impact of the synthesized CuFe₂O₄ spinel as a photocatalyst for degrading organic dyes through the photo-Fenton process. It demonstrates that degradation efficiency is closely related to the ferrite's band gap width and particle size. This study aimed to determine how the pH of the reaction medium impacts the structure, morphology, optical, mechanical, and magnetic characteristics of the nanosized ferrites being synthesized. Furthermore, the synthesized materials were evaluated for their photocatalytic abilities in degrading organic dyes in water. The ferrite powders showcased remarkable dye degradation capabilities via the photo-Fenton process. Degradation efficiency largely hinged on the band gap width and the size of the particles. The most notable outcome was achieved with sample P1, which had particle sizes averaging 12.14 nm. By unraveling the complex relationship between pH, structure, and properties, this research enhances our understanding of the design and optimization of nanoscale mixed ferrites.

Abstract: Copper Zinc Sulfide Cu_xZn_yS (CZS) thin films with different thicknesses were prepared by the ultrasonic spray pyrolysis method (USP). The influence of deposition time on the structural, morphological, and optical properties of the thin films has been investigated. XRD styles revealed the formation of ternary CZS films. Synchrotron X-ray diffraction measurements confirmed the presence of the two phases CuS and ZnS, which form the ternary compound CZS. Crystallite size increases from 75.29 nm to 105.46 nm as deposition time increases whereas the strain parameter decreases from 6.27*10^-4 to 3.28*10^-4. The obtained SEM images show that CZS thin films have a dense and rough surface topography. Spectrometric analysis of the deposited films confirmed the alloy nature of the elaborated films, whereas the corresponding values of band gaps were in the range of 3.28 to 3.17 eV. Results show that increasing the deposition time enhances the optical properties. Furthermore, the electrical properties of CZS films are influenced by the deposition time and phase transition. Significant improvements on these properties were obtained when the thin film thickness increased: the resistivity decreased from 95.10 to 0.12 Ω cm the carrier centration increased from 4.03×10²¹ to 14.07×10²¹ cm⁻³ and the mobility varied from 0.83 to 18.75 cm² V⁻¹ S⁻¹.