High Absorption Peak Research Articles

Deformation pattern classification and energy absorption optimization of the eccentric body centered cubic lattice structures

Lattice structures have shown excellent mechanical properties, such as high energy absorption capacity. In this work, the extended body centered cubic lattice was proposed by offsetting the position of the body center. The pattern recognition method of nonlinear discriminant function was creatively used to classify the proposed eccentric body centered cubic (EBCC) lattice structures according to their deformation patterns. The results indicated that the lattice structures belong to X-Pattern possessed the best energy absorption capability. Further, the relationship between the energy absorption properties and the configuration was captured using a modified symmetric radius basis function (RBF) surrogate model showing higher computational efficiency and approximately equal accuracy compared to the original RBF model. The nondominated sorting genetic algorithm II (NSGA-II) was carried out to obtain the Pareto optimal set, rendering the EBCC structure with balanced properties of high specific energy absorption and low peak crushing force. This work presents a first effort in optimizing the energy absorption of lattice structures through pattern recognition, thus expanding the approaches for designing new lattice structures.

Computational insights into electronic characteristics of 2D PtSe2 nanomaterials: Effects of vacancy defects and strain engineering

The epitaxial growth of PtSe2 monolayer has brings new opportunities for the application and development of materials science. Using first-principles calculations, the effect of vacancy defects, and strain engineering on the electronic properties of PtSe2 monolayer are systematically investigated. The results show that the Pt single vacancy induces a large magnetic moment of 4.0 μB on PtSe2 monolayer and transforms it from semiconductor to metal. However, the Se single vacancy systems are nonmagnetic and realize the PtSe2 from an indirect semiconductor to a direct one. Moreover, the band gap of PtSe2 monolayer can be prominently modulated within a appreciable uniaxial strain range, and the band gap are monotonically increase/decrease as decrease/increase the magnitude of the compressive/tensile strain. In particular, when a specific strain applied, a wide and high absorption peak across near-infrared, visible light and ultraviolet region. These findings not only enrich the fundamental understanding of PtSe2 monolayer but also provide useful guidance to design PtSe2-based spintronic, optoelectronic and gas sensing applications.

Tuning the optoelectronic properties of scaffolds by using variable central core unit and their photovoltaic applications

Central core modification is convenient strategy to adjust the optoelectronic properties that allows significant utilization of small fullerene free donor materials in photovoltaic technology. Herein, four push–pull conjugated molecules in acceptor–donor-acceptor (A-D-A) configuration are investigated through quantum chemical simulations. A comprehensive DFT study of reference R and designed donor materials (D1-D4) in which core is linked with thiophene spaced end-cap acceptors is conducted via selected functional MPW1PW91 and basis set (6-31G). Various critical parameters required to upgrade the efficiency of small molecule donors are electronic energy gaps, optical properties and exciton dynamics that are characterized by frontier molecular orbital diagram, absorption graph, transition density matrix (TDM), density of states (DOS), open-circuit voltage (Voc), and reorganization energy of charge carriers. Red shift occurs in all studied fluorine bearing scaffolds which absorb strongly in visible range 634–690 nm as compared to previously reported non-fluorinated molecule (598 nm). Amongst all donor molecules, D3, elucidates desirable photovoltaic characteristics i.e., highest absorption peak (690 nm), appropriate energy gap (2.17 eV) and considered to be the ideal aspirant in photovoltaics. Furthermore, reduction in reorganization energy and increment in Voc values illustrate that all molecules possess faster charge carrier mobilities than reference. This conceptual study clarified that we could amend the optoelectronic parameters by replacing core with variable electron rich components. Hence, these novel molecules containing fluorine should be recommended for construction of high-performance organic solar cells in future.

Design of selectively multilayered periodic gratings by PSO algorithm for radiative cooling

A novel selective multilayered periodic grating radiator (MPGR) was proposed in the paper, which is composed of Al2O3, SiO and SiO2 on an Al substrate. The influence factors on the radiative cooling power of the selective structure were studied by orthogonal test method, including the grating period, duty cycle and grating height. The spectral absorptivity and electromagnetic field of the MPGR were analyzed by using the rigorous coupled wave analysis (RCWA). Moreover, the MPGR was optimized by using the particle swarm optimization (PSO) algorithm. The results shown that the grating height has the greatest impact on the periodic grating structure. The optimized MPGR obtained a wide and high absorption peak in the atmospheric transparency window, which due to the coupling between SPPs and MPs of different modes. The emissivity of the designed grating presents a weak dependence on the incident angle. The optimized selective MPGR achieves a net cooling power of 118.17 W/m2 at nighttime ambient temperature of 300 K.

Temperature dependence of the spectral properties of Yb3+/P5+/Al3+ co-doped silica fiber core glasses

Yb3+/P5+/Al3+ co-doped silica fiber core glasses with different P5+/Al3+ molar ratios were prepared by the sol-gel method and modified chemical vapor deposition (MCVD) method. The absorption and fluorescence spectra were measured using a temperature range from 25°C to 200°C. Results show that both the major absorption and emission peaks of the Yb3+ ions become weaker and wider with the temperature increasing. The absorption cross sections of HYPA1 (the molar compositions of 0.2Yb2O3-2P2O5-2Al2O3-95.8SiO2) preform slices made by MCVD with a composition similar to the commercial 20/400 ytterbium-doped silica fibers (YDFs) decrease by ∼31.8% (915 nm), ∼25.3% (940 nm) and ∼41.6% (975 nm), in addition, the emission cross sections decrease by ∼32.1% (1030 nm) and ∼22.7% (1080 nm), respectively, all which indicate the decline of the laser properties with the temperature increasing of Yb3+ doped glass samples. The highest absorption peak at 975 nm of HYPA1 is blue-shifted by 0.80 nm as temperature raised from 25°C to 200°C and the absorption coefficient of the peak wavelength is reduced by nearly 5%. Additionally, the results also demonstrate that the Rabs (the ratio of σabs@975 nm/σabs@915 nm) and Rem (the ratio of σem@1030 nm/σem@1080 nm) are affected not only by the P5+/Al3+ molar ratio but also by the temperature. This work is helpful for understanding the fiber laser performance variations with the increase of the fiber core temperature due to high power operation.

Effect of plasmonic Aluminum nanoparticles shapes on optical absorption enhancement in silicon thin-film solar cells

Scattering from metal nanoparticles near their localized plasmon resonance; especially, the resonances of noble metals which are mostly in the visible or infrared part of the electromagnetic spectrum; is a way of improving light absorption in thin-film solar cells. The surface plasmon resonance can be affected by different factors such as the type, size, shape, and dielectric properties of the surrounding medium. Here we investigate, using the Finite Difference Time Domain (FDTD) method, how different shapes of aluminum nanoparticles affect absorption enhancement in silicon thin-film solar cells. Our results show that using these particles more than 30% conversion efficiency for plasmonic solar cells can be achieved compared to a cell without particles. We have also found that although the spherical particles have the highest absorption peak, optimization of some parameters such as the height of the cylinder or disk-shaped particles and their distance from the substrate can increase the absorption. The results can provide more information and insight to understand and optimize plasmonic particles for solar cell applications.

Multi-tonal subwavelength metamaterial for absorption and amplification of acoustic and ultrasonic waves

In this work, an acousto-ultrasound metamaterial-based concept is proposed to achieve high multi-tonal sound absorption at specific design frequencies and their multiple harmonics, which generally requires large and complex systems. This structure can be deployed to improve the performance of air-coupled nonlinear acoustic/ultrasound imaging by filtering unwanted fundamental ultrasound responses while amplifying high order harmonics, since nonlinear ultrasonic experiments generally necessitate advanced signal processing tools digital and pass-band filters to highlight nonlinear features. The structure proposed is an Archimedean inspired spiral cavity metamaterial with a thickness of 1/62 wavelength to achieve high multi-tonal sound absorption performances at a design frequency and the multiple harmonics. The same geometrical configuration can also be used to filter a fundamental design excitation frequency f0 and amplify second harmonic of the desired excitation frequencies, 2f0. An analytical model was developed to optimise the sound absorption and amplification frequencies of the structure with a design frequency of 690 Hz, by matching the geometrical parameters with the resonance and antiresonance mechanisms of the system. Additionally, a parallel arrangement of two Archimedean-inspired spirals is also analytically and experimentally proposed, in order to achieve harmonic absorptions at the resonant frequency of each subsystem (i.e. f01 = 850 Hz, f02 = 950 Hz). Furthermore, acoustic impedance analyses have been analytically conducted in order to physically explain all the resonance and antiresonance mechanism occurring with the proposed structures. Experimental investigations show that the proposed 3D printed metamaterial-based structures are capable to achieve multi-tonal high absorption peaks (above 90%) at the fundamental frequency f0 and odd harmonics (3f0, 5f0, etc) and sound amplification of the even harmonics (2f0 and 4f0). The results show good correlation between the predicted model and experimental results, and thus the sub-wavelength metamaterial provides promising potential for controlling and achieving high level sound absorption at low frequencies and enhancing accuracy of nonlinear ultrasound imaging applications.

Genotypic diversity of 17 cacti species and application to biosynthesis of gold nanoparticles

The genotypic diversity of 17 cacti species were examined and grouped in four clusters using seven inter simple sequence repeat (ISSR) markers. Group representatives (five species) were chosen for AuNPs synthesis in the cacti syrups. To synthesize the Gold nanoparticles (AuNPs), reducing and capping potential of five species of cacti rich in the polyphenolics were explored. Based on the synthesized AuNPs traits (concentration, pH, temperature, and synthesis time), Opuntia pycnacantha with the highest absorption peak at 540 nm was chosen for further characterizations. Varieties of diffraction peaks confirmed the successful synthesis of AuNPs. AuNPs functionalization with the phenolic compounds was confirmed by Fourier transform infrared (FTIR) spectroscopy. At the optimum conditions (pH = 5.0 and T = 60 °C), both dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed more than 87% of AuNPs to be 2.5 nm in size with Zeta potential to be equal to −19.9 mV.

Optoelectronic analysis of spectrally selective nanophotonic metafilm cell for thermophotovoltaic energy conversion

This work theoretically studies a spectrally selective nanophotonic cell based on an asymmetric Fabry-Perot resonance cavity structure with sub-100-nm GaSb layer for improving the thermophotovoltaic (TPV) energy conversion performance. The simulated spectral property of the ultrathin metafilm cell structure exhibits a high absorption peak above the bandgap due to the interference effect with electromagnetic field enhanced inside the GaSb layer between top and bottom silver electrodes, while the sub-bandgap absorption is as low as a few percent because of high reflectivity of the metal. An absorption enhancement nearly 20 times at particular frequency above bandgap is achieved within the sub-100-nm GaSb layer with the nanophotonic cell structure compared to the free-standing one. Besides, a thin layer of MoOx is incorporated into the metafilm cell structure as a hole transport layer to consider the charge collection in practice. With rigorous optoelectronic analysis by considering both radiative and nonradiative recombinations (Shockley-Read-Hall and Auger), the nanophotonic cell is predicted to achieve a TPV efficiency of 22.8% and output power of 0.62 W/cm2 with a black emitter at 1500 K due to spectrally enhanced in-band absorption and low sub-bandgap absorption. With an ideal selective emitter the efficiency can be further improved to 28% by eliminating sub-bandgap photons. While selective emitters still endure the challenges in perfect spectral emittance and high-temperature stability in practice, the proposed wavelength-selective nanophotonic metafilm cell could be a viable route to achieve high-efficiency and low-cost TPV energy conversion.

Pressure induced electronic, optical and thermoelectric properties of cubic SrZrO3: DFT investigation

FP-LAPW method is used to determine the electronic, optical, and thermoelectric characteristics of the SrZrO3. The band structure (BS) plot reveals indirect (Γ-M) energy gap for 0 GPa and 10 GPa. However, at 30 GPA, it converted to direct band gap. The total and partial density of states (PDOS) described the contribution of each atom in the material. The optical characteristics such as complex dielectric function, extinction and absorption coefficients, refractive index, and reflectivity are studied under pressure. The highest absorption peaks are originated due to the direct optical transition O-2p states to the Zr-4d orbitals. Moreover, thermoelectric properties are also investigated with respect to temperature. The Seebeck coefficient and electrical conductivity rises with the upsurge in pressure upto 40 GPa and highest value of ZT is 0.73. The simulated outcomes disclose that SrZrO3is a promising applicant for thermoelectric and optelctronic devices.

Effect of shear deformation on aluminum adsorption on silicene

Silicene has important applications in the field of nanoelectronics due to its superior electronic properties. Based on the density functional theory, the influence of shear deformation on the electronic structure and optical properties of Al absorbed silicene system is studied by using the first-principles calculations. The results show that the most stable adsorption sites of double aluminum atoms on the surface of silicene are top and valley. After silicene adsorbs aluminum atoms, the silicene around the Al atoms attains different degrees of distortion. The analysis of the electron band structure and the density of states shows that after adsorption of Al atoms, the band gap of silicene increases. As the degree of shear deformation increases, the band gap of the adsorption system gradually decreases. Shear deformation causes the highest absorption peak and the highest reflection peak of the adsorption system to redshift, and the degree of redshift increases with the increase of displacement.

Utility of Spectroscopic Studies for Quantification of Cefditoren Pivoxil in Commercial Samples

The current study is devoted to suggest new simple spectrophotometric probes for the estimation and quantification of cefditoren pivoxil (CFP) either in authentic or in commercial samples. Three simple kinetic and derivatize sensitive spectrophotometric methods were established. Two kinetic techniques (method A) and (method B) were based on the estimation of CFP using the oxidation properties of alkaline potassium permanganate at ambient temperature and the relation between the reduction in the absorbance of KMnO4 and the added CFP were also investigated. The intensity of absorbance (A) of the colored MnO4- ions were recorded at wavelengths 610 and 525 NM for the two methods, respectively. Method C was based on derivatization of CFP with 1,2-naphthoquinone-4-sulphonate reagent in a basic solution (pH=11) to produce an orange red colored solution exhibited the highest absorption peak (λmax) at 411 nm. The proposed systems displayed linearity over the concentration ranges of 1.0-16.0, 1.0-10.0 and 0.5-7.0 and#181;g mL-1.The suggested systems were validated obeying analytical methodology guidelines and the acceptance criteria for accuracy, precision, linearity, selectivity, and robustness were met in all cases.

Utility of Spectroscopic Studies for Quantification of Cefditoren Pivoxil in Commercial Samples

The current study is devoted to suggest new simple spectrophotometric probes for the estimation and quantification of cefditoren pivoxil (CFP) either in authentic or in commercial samples. Three simple kinetic and derivatize sensitive spectrophotometric methods were established. Two kinetic techniques (method A) and (method B) were based on the estimation of CFP using the oxidation properties of alkaline potassium permanganate at ambient temperature and the relation between the reduction in the absorbance of KMnO4 and the added CFP were also investigated. The intensity of absorbance (A) of the colored MnO4- ions were recorded at wavelengths 610 and 525 NM for the two methods, respectively. Method C was based on derivatization of CFP with 1,2-naphthoquinone-4-sulphonate reagent in a basic solution (pH=11) to produce an orange red colored solution exhibited the highest absorption peak (λmax) at 411 nm. The proposed systems displayed linearity over the concentration ranges of 1.0-16.0, 1.0-10.0 and 0.5-7.0 and#181;g mL-1.The suggested systems were validated obeying analytical methodology guidelines and the acceptance criteria for accuracy, precision, linearity, selectivity, and robustness were met in all cases.

Effects of extraction conditions on characterization of gelatin from water buffalo (Bubalus bubalis) skin

The study aimed to determine the characteristics of gelatin from water buffalo (Bubalus bubalis) skin pre-treated with NaOH and Ca(OH)2 at different concentrations (0.3 M, 0.5 M and 0.7 M) and extracted at 65˚C for 6 hrs and 24 hrs respectively. The gelatin obtained was evaluated for its moisture, protein and ash content, UV-vis absorption value, colour, emulsifying and foaming properties. The highest yield (20.25%) was observed for gelatin extracted by 0.5 M NaOH at 24 hrs extraction time. For alkaline pre-treatment, it was found that NaOH was more efficient than Ca(OH)2 in terms of preparing the skin for subsequent extraction process. The protein content of the extracted gelatin samples was in the range of 71.76% - 87.83%, showing that the varying processing conditions are sufficiently to recover protein from the raw material. Ash content for all samples was in agreement with USDA standard, which was below than 3%. The extracted gelatin had varying pH values which were from 5.47 to 7.02. The gelatin was colourless with ‘L’ values of more than 80, except for 0.7 M Ca(OH)2 at 24 hrs which showed slightly darker properties. The intensity of the UV-vis absorption spectrum showed that a high absorption peak was observed at 6 hrs of extraction time (230 – 250 nm) compared to 24 hrs extraction time. Emulsifying properties of buffalo gelatin increased with increasing concentrations of alkaline except for 0.7 M NaOH and 0.7 M Ca(OH)2 for both extraction time. Meanwhile, foam expansion of the gelatin extracted from the different extraction conditions was observed to have a significant difference (p < 0.05) for all samples. To our knowledge, buffalo skin has the potential to be an alternative source of gelatin in the diversified industrial application by modifying the extraction conditions in order to produce gelatin with desired quality.

Stereo Perfect Metamaterial Absorber Based on Standing Gear-Shaped Resonant Structure With Wide-Incident-Angle Stability

In this work, a single-band metamaterial absorber (MA) based on a three dimensional (3D) resonant structure is presented. The unit cell is composed of a standing gear-shaped resonator, which is embedded in the dielectric substrate. The proposed 3D MA is ultrathin with a total thickness of 2.3 mm, corresponding 0.077λ0 at its center frequency. The simulation results demonstrate a high absorption peak at 10.1 GHz with absorptivity of 99.9%. The proposed 3D MA is insensitive to the polarization of the incident wave due to its rotationally symmetric structure. Moreover, the proposed 3D MA exhibits a wide-incident-angle stability, as absorptivity of more than 85% can be achieved for both TE and TM incidences with incident angle up to 60°. Most importantly, multiband electromagnetic wave absorption of the stereo MA can be enabled by adjusting the structural parameters of the standing gear. The proposed structure is compatible with 3D printing technology and has potential applications in electromagnetic shielding.

Design of Four Layer Microwave Absorber Based on Polyaniline-Expanded Graphite Composites: Role of Layer Interfaces in Impedance Matching

The present work investigated design simulation of single and multi-layer microwave absorber based on mono-phase (polyaniline) and dual—phase (polyaniline-expanded graphite) dielectric composite material. The work is the extension of author’s earlier work on carbon–based material using the unique behavior of polyaniline and highly conducting Expanded Graphite as fillers. The dual phase composites of polyaniline/Expanded Graphite prepared by in situ polymerization of aniline with different EG concentration of (0.00, 0.15 and 0.25 wt.%) were mixed with Novolac Phenolic Resin (NPR) in (10, 20 and 30 wt.%) to form (PA1-PA3 & PG1-PG3, PG4-PG6). Based on microwave characterization results and employing transmission line model, a theoretical analysis has been qualitatively done on four layer design simulation of absorber to achieve high performance absorption peak and bandwidth and subsequently fabrication of the designed structure for X-band microwave absorption. A calculated reflection loss ∼−80 dB is observed at 10.69 GHz for PG1-PG3-PG5-PA3 four layer designs having overall thickness of 8.6 mm and promising measured reflection loss ∼−63 dB at 10.66 GHz near the central frequency of the experimental frequency range. High performance absorption is interpreted as impedance matching behavior at the layer interface of the multilayer structure.

Ultra-narrowband wavelength adjustable multichannel near perfect absorber in Thue–Morse defective quasi-photonic crystals embedded with MoS2 monolayer

A defective Thue–Morse quasi-photonic crystal containing molybdenum disulfide (MoS2) is suggested to construct an ultra-narrowband multiple resonant absorber in the visible range. Multiple high absorption peaks can be achieved by altering the design of the proposed structure in different ways such as changing the generation number or the symmetry with respect to defect. Two structures are introduced, which create more than seven absorption peaks higher than 40% and one of the peaks about 100%. Defect modes' wavelength can be tuned to show the blue shift by incident angles and the polarization of light. Our optimal structures are useful for applications in multiplex filters and multiple channel sensors due to their high amount and narrowband absorption peaks and can show nearly perfect absorption.

Stable C2N/h-BN van der Waals heterostructure: flexibly tunable electronic and optic properties

Monolayer C2N has been successfully synthesized. To explore the enhancement of its stability and the expansion of its potential applications in electronics and optoelectronics, a vertical van der Waals heterostructure is constructed by C2N monolayer integrated with h-BN monolayer. The first-principles calculations based on the density functional theory show that this structure possesses a type-II band alignment with a smaller direct band gap and lager band offsets, suggesting that photo-generated electron–hole pairs can be well spatially separated, and thus an excellent photoelectric and photovoltaic material can be obtained. Also shown is that the electronic properties of such a heterostructure can be effectively regulated by a vertical strain and external electric field. For example, under compressive strain or forward electric field, its band gap can be significantly reduced to enhance light-excitation electron transition further, meanwhile the feature of direct band-gap and large band offsets is always well-preserved. Furthermore, it is found that the intrinsic heterostructure holds a wide optic adsorption range and large adsorption coefficient, and the applied compressive strain or a positive electric field can lead to a wide and high main absorption peak across the near-infrared, visible light, and ultraviolet region, implying that a tuned heterostructure has more promising applications in optoelectronics.

Study of anion replacement effect on SrCd2X2 (X = P, As, Sb, Bi) compounds by FPLAPW+lo

The structural parameters, optoelectronic and thermoelectric properties of SrCd2X2 (X = P, As, Sb and Bi) compounds have been investigated thoroughly for the first time using first principles methods. The compounds are optimized and obtained structural parameters agree to the experimental data. Electronic band profiles of the compounds reveal that the SrCd2P2, SrCd2As2, SrCd2Sb are direct band gap semiconductors while SrCd2Bi2 is metallic. Valence band is composed on mainly X-p states while Sr-d state in conduction band. Compounds show the strong absorption in the visible region and low frequency ultraviolet region. The characteristics optical peaks shift towards lower energy by replacing the anion from P to Bi. Boltzmann transport theory is implemented through the BoltzTraP code to calculate the electrical and thermal conductivities, Seebeck coefficients and thermo power factor. High absorption peaks and figure of merits of the compounds show that these compounds can be important for optoelectronics and thermo-electric devices.

Bending deformation regulates the electronic and optical properties of black phosphorene

The electronic and optical properties of black phosphorene with different bent angle are studied using density functional theory based on the first-principles. Within the scope of our study, it was found that the phosphorene becomes less stable with the increasement of bending deformation. Bending deformation has great impact on the electronic and optical properties on phosphorene. The bandgap degrades a little at [Formula: see text] bent angle, and then increases when the bent angle does not surpass [Formula: see text], after which the bandgap decreases with the increasement of bending deformation. Besides, the bandgap of black phosphorene occurs a direct to indirect transition at [Formula: see text] bent angle. The bandgap calculated by HSE06 is larger than PBE functional, but the law of changes is consistent. By analyzing the density of states, we concluded that all the undeformed and deformed phosphorene structures have a strong sp orbital hybridization. Besides, the p orbits have narrower gap than s orbits, which causes the narrower bandgaps of these structures. From the analysis of optical properties, we concluded that the black phosphorene with [Formula: see text] bent angle has the highest absorption coefficient. All structures under bending deformation have higher reflectivity peak than intrinsic black phosphorene, among these structures, the black phosphorene with [Formula: see text] bent angle has the highest reflectivity. The novel optical property is observed at the [Formula: see text] deformed structure, it stops absorbing (reflecting) light first. Redshift and blueshift phenomena are observed at the highest absorption peak and reflectivity peak.