Papers by Keyword: Optical Properties

Abstract: Yttrium-doped ZnO aerogel nanostructures with low Y concentrations (0.5 and 1 at.%) were synthesized through a modified sol–gel process coupled with supercritical isopropanol drying, yielding highly porous and crystalline materials. Structural and optical characteristics were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Utraviolet–Visible (UV–Vis) spectroscopy, and photoluminescence (PL) spectroscopy. XRD results confirmed the formation of single-phase polycrystalline ZnO with a hexagonal wurtzite structure for all samples, along with lattice perturbations consistent with the substitution of Zn²⁺ by Y³⁺ ions. FTIR spectra further supported successful ZnO network formation, revealing a systematic shift of the Zn–O stretching band toward lower wavenumbers upon Y incorporation. UV–Vis measurements showed that yttrium doping enhances optical absorbance and induces a slight redshift of the absorption edge, indicating a modest narrowing of the band gap. PL analysis demonstrated a remarkable enhancement in UV and visible emission for the ZnO:Y (0.5 at.%) sample, which exhibited the highest overall PL intensity across the investigated spectral range. This enhancement is attributed to an increased radiative recombination rate of photogenerated carriers and the formation of additional defect-related states introduced by low-level Y doping. These findings highlight the strong potential of yttrium-modified ZnO aerogels for tunable optical and photonic applications.

Abstract: In this study, TiO₂ nanoparticles (NPs) were co-doped with silver (Ag) and gold (Au) via a solvothermal method conducted at for 30 min to enhance their structural, morphological, and optical properties. The TiO₂ samples were prepared as follow: pure TiO₂, TiO₂ doped with 0.5% Ag:1% Au, 1% Ag:0.5% Au and 1% Ag:1% Au NPs named as, S₀, S₁, S₂ and S₃, respectively. The samples were annealed at for 2 hours. Several characterizing methods namely; XRD, FTIR, AAS, FESEM, EDX and PL were used to investigate the presences of doping ratios with noble metals and their effects on the structural, morphological and optical properties of TiO₂. The XRD results revealed that the average crystallite size of the doped samples decreased compared to the un-doped TiO₂. The average crystallite size of S₀, S₁, S₂ and S₃ were found to be 13.56, 12.69, 11.76 and 11.49 nm, respectively, which can be related to the inhibition of crystal growth due to doping. FTIR analysis confirmed slight shifts and changes in intensity in O-H and C-O bands suggest the interaction between the TiO₂ matrix and the Ag/Au dopants, indicating successful surface modification and potential changes in surface chemistry. AAS revealed the presence of Ag and Au. The average particle size of S₀, S₁, S₂ and S₃ were found to be 23.82, 20.05, 19.25 and 18.89 nm, respectively. At the same time, element mapping images confirmed the homogeneous spatial distribution and incorporation of Ag and Au in the doped samples. PL analysis indicated that doping TiO₂ with Ag/Au NPs significantly decreases electron –hole recombination.

Abstract: Thin films of ZnMn₂O₄ were deposited on quartz substrates at 250 °C using the Pulsed Laser Deposition (PLD) technique and then annealed in air at 500 °C for 6 hours. The films were tested for detection of NO₂ and NH₃ at different operating temperatures. The films showed rapid response time is (7.2 s) for NO₂ and (13.5 s) for NH₃ at 300 °C. The upper sensitivity of NH₃ is 15%, while the upper sensitivity of the samples tested with 60ppm NO₂ is 93% at a temperature of around 300°C. Also, the structural properties as X-ray diffraction ( XRD), Field emission scanning electron microscopy (FESEM), and optical properties were studied. Keywords: Gas sensors, pulse laser deposition, PLD, ZnMn₂O₄, Sensing properties, 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).