Valley photonic crystals (PCs) play a crucial role in controlling light flow and
realizing robust nanophotonic devices. In this study, rotated gradient valley PCs
are proposed to realize topological rainbow trapping. A topological rainbow is
observed despite the presence of pillars of different shapes, which indicates the
remarkable universality of the design. Then, the loss is introduced to explore the
topological rainbow trapping of the non-Hermitian valley PC. For the step-angle
structure, the same or different losses can be applied, which does not affect the
formed topological rainbow trapping. For a single-angle structure, the applied
progressive loss can also achieve rainbow trapping. The rainbow is robust and
topologically protected in both Hermitian and non-Hermitian cases, which is
confirmed by the introduction of perturbations and defects. The proposed
method in the current study presents an intriguing step for light control and
potential applications in optical buffering and frequency routing.
 

Due to the large versatility in organic semiconductors, selecting a suitable (organic semiconductor) material for photodetectors is a challenging task. Integrating computer science and
artificial intelligence with conventional methods in optimization and material synthesis can guide
experimental researchers to develop, design, predict and discover high-performance materials for
photodetectors. To find high-performance organic semiconductor materials for photodetectors, it is
crucial to establish a relationship between photovoltaic properties and chemical structures before
performing synthetic procedures in laboratories. Moreover, the fast prediction of energy levels is
desirable for designing better organic semiconductor photodetectors. Herein, we first collected large
sets of data containing photovoltaic properties of organic semiconductor photodetectors reported in
the literature. In addition, molecular descriptors that make it easy and fast to predict the required
properties were used to train machine learning models. Power conversion efficiency and energy
levels were also predicted. Multiple models were trained using experimental data. The light gradient
boosting machine (LGBM) regression model and Hist gradient booting regression model are the
best models. The best models were further tuned to achieve better prediction ability. The reliability
of our designed approach was further verified by mining the photovoltaic database to search for
new building units. The results revealed that good consistency is obtained between experimental
outcomes and model predictions, indicating that machine learning is a powerful approach to predict
the properties of photodetectors, which can facilitate their rapid development in various fields.
 

In this work, we employed the casting procedure to synthesize polymer hybrids from epoxy with acrylic polymer coating with nanoclay. The investigated polymer hybrid was composed of 80% epoxy resin, 17% acrylic polymer solution, and 3% nanoclay. The polymer hybrid samples were ranged in thickness from 1 to 3 mm. The influence of the sample’s thickness on thermal stability, thermal conductivity, and mechanical properties, as well as the constant angle of polymer hybrids were examined. The structural investigation revealed that the loaded nanocaly is crystalline with an average crystal size of 56 nm inside the amorphous polymer matrix. Also, it consistently dispersed throughout the epoxy matrix, showing that the tiny nanoparticles were meant to agglomerate with one another. The maximum thermal stability was found in polymer hybrids with a thickness of 2 mm, and the contact angle was closed to 90° for polymer hybrids with a thickness of 1.5 mm. The hardness values were remained constant around 73 ± 1 and were unaffected by sample’s thickness. Meanwhile, increasing the polymer hybrid's thickness slightly improves the impact and flexural strength values. The anticipated value of the wear rate was slightly changed while increasing with applied force. As the thickness of the synthesized polymer hybrids was rose from 1 to 3 mm, the thermal conductivity was fell from 0.47 to 0.32 W/m K. The synthesized hybrid epoxy and acrylic polymer coating/nanoclay was exhibit significant thermal and mechanical stability, as well as hydrophobicity, and hence may be employed for floor painting and waterproofing applications.

The effect of Ag content on the linear and nonlinear optical characteristics of thermal evaporated  Se90−xTe10Agx thin films, 100 nm thick, (where x = 0, 2, 4, 6, and 8 at.%) has been examined. The optical measurements were reviewed in the wave length range of 390–2500 nm based on the transmittance and reflectance data, and the amorphous state of the as-prepared thin film was confirmed by X-ray diffraction. The absorption coefficient, extinction coefficient, bandgap, optical density, optical conductivity, dissipation factor, and other optical properties were examined and discussed. For all of the samples, the extinction coefficient of Se90−xTe10Agx declines as the wavelength and Ag concentration rise, whereas the absorption coef f icient increases linearly with incident photon energy. Furthermore, the optical bandgap and the width of localized states alter in the exact opposite direction, which is consistent with previously reported findings. The decrease in the optical band gap as Ag concentration increases could be attributable to an increase in the amount of disorder in the materials and the density of defect states. Other critical optoelectronic characteristics are also determined, and they are found to be influenced by the Ag ratio and photon wavelength. These materials may be ideal for optical memory applications due to their high absorption coefficient and compositional dependence of absorption.

Nickel oxide (NiO) nanoparticles were formed using the chemical precipitation method. The effect of the calcination process on the structural parameters, optical bandgap, and photocatalytic performance was investigated. The structural characteristics were carried out using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The XRD analysis reveals that the formed NiO crystallized in an fcc crystal structure and the calcination process influences the crystallite size, microstrain, dislocation density, and average surface area. For example, the smallest and largest particle sizes (19.13 nm and 27.63 nm) were achieved for the samples prepared at 800 °C for 4 h and 900 °C for 2 h, respectively. Based on the diffuse reflectance spectroscopy analysis, the energy bandgap has the lowest values (3.33 eV) for the prepared NiO that calcinated at 800 °C for 2 h compared with other samples. The formation of a Ni–O stretching vibra tion mode is revealed by FTIR, and the broadness of the absorption band confirms that the NiO samples are nanocrystals. The morphology of the prepared NiO reveals the formation of spherical nanoparticles for NiO calcinated at 700 °C, while dodecahedron-like shapes were observed for NiO calcinated at 800 and 900 °C. The photocatalytic performance of NiO nanoparticles as catalysts for the degradation of indigo carmine dye was investigated under ultraviolet–visible irradiation up to 3 h. The best degradation efficiency was found to be 76% for NiO calcinated at 800 °C for 4 h, which belonged to the smallest crystallite size of 19.13 nm, and the highest surface area of 47.02 m2g−1. The superior and excellent performance of this sample compared to other samples was confirmed by achieving the highest reaction rate constant (4.51 × 10−3min−1). The proposed photodegradation mechanism shows the importance of increasing the time required for the recombination process between the positive holes and the excited electrons, which is the best possible when using the optimum photocatalyst sample that was prepared at 800 °C for 4 h.

The structural parameters, photoluminescence (PL), and magnetic characteristics of MxSn1−xOy (M/SnO2) nanocomposites, synthesized by the hydrothermal method, where x = 0.0, 0.5, and M present non-magnetic metals (Cu, Al) and magnetic metals (Fe, Ni, Mn) were studied. The crystallite size and porosity of SnO2 were reduced by mixing with Cu, Al, Fe, or Ni, meanwhile, increased by integrating with Mn. The residual stress of SnO2 was increased 5-fold by Mn doping. The energy dispersive X-ray analysis revealed that Al is the lowest ion for full acceptor incorporation into the SnO2 lattice, while the other doped metal ions show better incorporation.  SnO2 doping has a significant impact on the particle morphologies of MxSn1−xOy nanocomposites. The Debye temperature (θD) and Young’s modulus (Y) were estimated from the FTIR spectra. The value of θD is 633.86 K for SnO2 nanoparticles and increased to 694.68 K for Mn/SnO2, while it decreased to 608.27 K for Fe/SnO2. The value of Y was increased from 518.30 GPa for SnO2 to 864.41 GPa for Cu/SnO2 nanocomposite. The PL intensity of SnO2 was decreased by Cu, Fe, Ni, and Mn doping, whereas it was increased by Al doping. The blueshift was observed for Al/SnO2 and Mn/SnO2, whereas it is a slight ultraviolet shift for Cu/SnO2, Fe/SnO2, and Ni/SnO2 nanocomposites. SnO2 nanoparticle and Al/SnO2 nanocomposite exhibit weak ferromagnetic behavior by increasing the magnetic field (H) up to 4 kG, while with further increase in H, the samples exhibit diamagnetic behavior. In contrast, the Fe/SnO2, Ni/SnO2, and Mn/SnO2 nanocomposites show a paramagnetic trend, while the Cu/SnO2 nanocomposites exhibit a diamagnetic trend in the magnetic field range of 0–20 kG. The saturated magnetization and magnetic moment are enhanced for all MxSn1−xOy nanocomposites, whereas the corrective field and magnetic anisotropy are decreased compared to SnO2 nanoparticles. The f indings recommended SnO2 and Al/SnO2 composites for spintronic devices and cathode–luminescence displays, Fe/SnO2, Ni/SnO2, and Mn/SnO2 nanocomposites for magnetic imaging, and Cu/SnO2 composites for catalytic and plastic deforma tion applications.

In this article, the casting method was used to prepare poly(methyl methacrylate)/hydroxyapatite (PMMA/HA) nanocomposite f ilms incorporated with different contents (0.5, 1, and 1.5 wt%) of graphene nanoplatelets (Gnp). The chemical properties and surface morphology of the PMMA/HA blend and PMMA/HA/Gnp nanocomposite were characterized using FTIR, and SEM analysis. Besides, the thermal conductivity, dielectric and electrical properties at (1–107 Hz) of the PMMA/HA blend and PMMA/HA/Gnp composites were investigated. The structural analysis showed that the synthesized composites had a low agglomerated state, with multiple wrinkles of graphene flakes in the PMMA/HA blend. The thermal conductivity was improved by more than 35-fold its value for pure PMMA. The AC and DC electrical conductivities of PMMA/HA/Gnp composites were enhanced with increasing the amount of Gnp and the estimated exponent (s) being between 1.25 and 1.3. The values of the real part (ɛ′) and imaginary part (ε′′) of the dielectric constant as well as electrical impedance depend on the Gnp ratio. The value of ɛ′ was reduced at the lower frequency (< 105 Hz) and became constant at the higher frequency which attributed to the relaxation time. The values of ε″ are small at low frequencies and increase with increased frequency due to the electronic polarization effects as well as to the dipoles not beginning to follow the field variation at higher frequencies. The increase in the dielectric loss, tan(δ), with an increase in Gnp content, to 0.5 wt%, due to the interfacial polarization mechanism occurred in the composite’s films corresponding to frequencies.

The direct impregnation approach is used to synthesize nickel dimethylglyoxime (NDG) on γ-alumina (γ-Al2O3) composites to be used as a catalyst. The structural, thermal, and magnetic characteristics of γ-Al2O3, NDG, and NDG/γ-Al2O3 composites are investigated and their photocatalytic performance towards methylene blue (MB) and methyl orange (MO) is examined. The finding supports the use of NDG over γ-Al2O3 as catalysts, besides their enhanced thermal stability. The scanning elec tron microscope (SEM) and transmission electron microscopy (TEM) demonstrate that the catalyst particles are dispersed uniformly, indicating that the Ni microcrystalline or Ni nanoparticles on γ-Al2O3 are most likely distributed in a single phase and/or in a homogenous route. X-ray diffraction (XRD) results together with the results of SEM and TEM indicated that NDG/γ-Al2O3 nanocomposite catalysts can be prepared effectively by impingement approach. The average crystallite size of γ-Al2O3 is 6 nm, whereas the average crystallite size of NDG/γ-Al2O3 composites is 10 nm. Both γ-Al2O3 and NDG/γ Al2O3 composites have a weakly diamagnetic response, whereas NDG exhibits poor ferromagnetism response. The calculated values for the photodegradation efficiency, after UV–visible irradiation for 130 min, towards MO dye employing γ-Al2O3, NDG, and NDG/γ-Al2O3 composites as a catalyst are 74.2, 36.7, and 61.7%, respectively, whereas their values towards MB dye are 17.8, 5.3, and 19.1%, respectively. Furthermore, when NDG was combined with γ-Al2O3 to form NDG/γ-Al2O3 composites, the degradation performance was significantly improved and could be suitable for the degradation of other dyes.