Additional Absorption Peak Research Articles

Investigating the optoelectronic properties of Mn and Fe doped CuAlS₂ for intermediate band solar cell applications

Chalcopyrites demonstrate compelling features for optoelectronic and photovoltaic devices, attributed to their valuable properties. Their remarkable light-absorption capabilities and well-suited band gap render them so attractive for applications in these fields. By allowing low-energy sub-bandgap photons to pass through and reducing the thermalisation loss from high-energy photons, intermediate-band materials address the primary problems in solar cells. This approach allows for more efficient use of the solar spectrum, helping solar cells exceed the traditional efficiency limits defined by the Shockley-Queisser limit. The objective of this study was to evaluate the electronic and optical characteristics of CuAlS2 systems doped with transition metals (TM = Mn, Fe) using the Full Potential Linearized Augmented Plane Wave approach within the framework of Density Functional Theory. A stable phase within the systems was observed upon replacing the Al atom with TM. The functionality of the intermediate band was governed by the 3d electronic characteristics of the TM3+ ion and its electronic configuration. The optical properties of CuAlS2 doped with Mn and Fe were analysed by calculating the dielectric function, refractive index, reflectivity, and absorption coefficient. Furthermore, the introduction of Mn and Fe through doping led to the creation of an intermediate band, enhancing visible light absorption and power conversion efficiency. Consequently, the optical spectrum of Mn-doped CuAlS2 and Fe-doped CuAlS2 compounds exhibits additional absorption peaks, accompanied by a significant improvement in absorption intensity. Our findings highlighted the need for continued and futuristic research into the scalability of these materials for practical applications in solar cells, optoelectronics, and spintronic devices. This investigation suggests that Mn-doped CuAlS2 holds the highest potential due to its high charge carriers and low recombination rate, indicating enhanced performance in CuAlS2-based intermediate band solar cells.

Low-frequency broadband acoustic metamaterial absorber based on nested resonator and synergistic coupled weak resonances

Utilizing absorbers with sub-wavelength thickness for low-frequency broadband noise control is a challenging problem, and rapid on-demand design of structures based on target noise frequency has received continuous attention. In this work, nested cavities are introduced into the typical neck-embedded Helmholtz resonator (NEHR) to obtain the nested neck-embedded Helmholtz resonator (NNEHR), which exhibits better cavity partitioning volume fraction and covers wider sound absorption band. Both theoretical analysis and simulations demonstrate that NNEHR possesses superior acoustic properties: generating an additional absorption peak, lowering the position of the first absorption peak by 11 %, and increasing the absorption coefficient by 4.7 %. Instantaneous velocity fields and thermal-viscous energy dissipation density illustrate that the efficient sound absorption of NNEHR originates from resonant dissipation in the neck and surrounding areas. Furthermore, by combining the theoretical model with genetic algorithms, three sets of NNEHR metasurfaces are optimized. The optimized structures achieve average absorption coefficients of 0.831, 0.913, and 0.885 in the range of 250–550 Hz, 400–1000 Hz, and 500–2000 Hz, with a thickness of only 50 mm, reflecting sub-wavelength, low-frequency broadband sound absorption characteristics. The excellent absorption stems from synergistic coupled weak resonances and higher-order absorption peaks of constituent units, and the overdamping characteristic ensures the realization of the optimal structure with minimal thickness. The contribution of weak resonant units to the total sound absorption performance can be measured by the surface admittance normalized by the total incident area, and the essence of the coupling effect is the strong interaction between units with adjacent absorbing frequencies. The proposed structure exhibits good sound absorption performance and great adjustability, while the genetic algorithm optimization based on the theoretical model demonstrates high efficiency and robustness, providing a methodology for the design and on-demand optimization of low-frequency broadband structures.

Compositional Transformation and Impurity‐Mediated Optical Transitions in Co‐Evaporated Cu2AgBiI6 Thin Films for Photovoltaic Applications

AbstractQuaternary copper‐silver‐bismuth‐iodide compounds represent a promising new class of wide‐bandgap (2 eV) semiconductors for photovoltaic and photodetector applications. In this study, vapor phase co‐evaporation is utilized to fabricate Cu2AgBiI6 thin films and photovoltaic devices. The findings show that the properties of vapor‐deposited films are highly dependent upon processing temperature, exhibiting increased pinhole density and transforming into a mixture of quaternary, binary, and metallic phases depending on the post‐deposition annealing temperature. This change in phase is accompanied by an enhancement in photoluminescence (PL) intensity and charge‐carrier lifetime, along with the emergence of an additional absorption peak at high energy (≈3 eV). Generally, increased PL is a desirable property for a solar absorber material, but this change in PL is ascribed to the formation of CuI impurity domains, whose defect‐mediated optical transition dominates the emission properties of the thin film. Via optical pump terahertz probe spectroscopy, it is revealed that CuI impurities hinder charge‐carrier transport in Cu2AgBiI6 thin films. It is also revealed that the predominant performance limitation in Cu2AgBiI6 materials is the short electron‐diffusion length. Overall, the findings pave the way for potential solutions to critical issues in copper‐silver‐bismuth‐iodide materials and indicate strategies to develop environmentally compatible wide‐bandgap semiconductors.

Osobennosti povedeniya linii epr (<i>g </i>≈ 4<i>.</i>3) v magnitnykh nanogranulyarnykh kompozitakh

Films of metal-insulator nanogranular composites MxD100 – x with different composition and percentage of metal and dielectric phases (M = Fe, Co, CoFeB; D = Al2O3, SiO2, LiNbO3; x ≈ 15–70 at %) are investigated by magnetic resonance in a wide range of frequencies (f = 7–37 GHz) and temperatures (T = 4.2–360 K). In addition to the usual ferromagnetic resonance signal from an array of nanogranules, the experimental spectra contain an additional absorption peak, which we associate with the electron paramagnetic resonance (EPR) of Fe and Co ions dispersed in the insulating space between the granules. In contrast to the traditional EPR of Fe and Co ions in weakly doped non-magnetic matrices, the observed peak demonstrates a number of unusual properties, which we explain by the presence of magnetic interactions between ions and granules.

Identifying the photon absorption characteristics of Cr-doped Cu2ZnSnS4 (CZTS:Cr) thin film deposited by Co-sputtering technique

This study investigates the potential of a quaternary compound semiconductor to be realized as the absorber layer for third-generation intermediate band solar cells (IBSCs). In this work, the effects of Cr doping into Cu2ZnSnS4 (CZTS) host material to form intermediate band within the forbidden bandgap were studied. The films were deposited by a co-sputtering technique. It has been found that Cr has a high preference to substitute Zn, followed by Sn, then Cu. Insufficient Cr does not lead to intermediate band but, instead, forms defect states within the bandgap. Excess Cr however deteriorates CZTS (112) peak while at the same time secondary phase of cubic-ZnCr2S4 starts to grow. At sufficient levels of Cr content, absorption coefficient tremendously improved to 105 cm−1, resulting in an additional absorption peak attributed to possible formation of an intermediate band. This intermediate band is located at 1.40 ± 0.02 eV below CBM, while the band gap Eg is 1.55 eV. Further optimization to the sulphurization process reveals that the intermediate band peak, ECIL could be adjusted towards blue or red shift by manipulating Cr and/or sulphur content. This yields a bandgap of 1.52 eV with two intermediate bands positioned at 0.90 eV and 1.20 eV above the VBM. These preliminary findings are beneficial prior to realizing a working device of CZTS:Cr intermediate band solar cell.

Optical absorption of bismuthene with a single vacancy: first-principle calculations.

The exceptional mechanical, electronic, topological, and optical properties, make bismuthene an ideal candidate for various applications in ultrafast saturation absorption and spintronics. Despite the extensive research efforts devoted to synthesizing this material, the introduction of defects, which can significantly affect its properties, remains a substantial obstacle. In this study, we investigate the transition dipole moment and joint density of states of bismuthene with/without single vacancy defect via energy band theory and interband transition theory. It is demonstrated that the existence of the single defect enhances the dipole transition and joint density of states at lower photon energies, ultimately resulting in an additional absorption peak in the absorption spectrum. Our results suggest that the manipulation of defects in bismuthene has enormous potential for improving the optoelectronic properties of this material.

Optimized conditions for cobalt diffusion in Sri Lankan colorless topaz and coloration mechanism elucidation through spectro-chemical investigation

Most of natural topaz is colorless; thus, methods of color enhancement are widely used for coloring this mineral. Currently, blue color is obtained by cobalt diffusion due to drawbacks in existing coloration methods. In this study, optimum conditions suitable for Cobalt diffusion in Sri Lankan colorless topaz were investigated and coloration mechanism was elucidated. The diffusion agent was prepared by mixing CoCO3 with Na2CO3, CaCO3 and carbon powder and diffusion was carried-out by varying the temperature and soaking time. Chemical analysis, UV-Vis absorption spectrum, infrared absorption spectra, and Raman peaks of diffused and non-diffused topaz were tested. The results clearly indicated that the optimum condition for Co diffusion in Sri Lankan topaz is 950℃ for 11 h. The EPMA analysis showed that the Co concentration in the diffused sample varied from 0.001 wt% to 0.027 wt% while colorless topaz showed <0.001 wt%. The UV-Vis spectrum of Co diffused blue topaz gave three absorption peaks at 556, 588, and 627 nm corresponding to three spin-allowed electronic transitions of Co2+ ion in teterahedaral coordination. In case of Co diffused topaz, one additional new broader IR absorption peak was noticed around 6640 cm-1 presumably arising by optical transitions of 4A2 → 4T1 in Co2+ (4F). Our results lead to the conclusion that, blue color of the Co diffused topaz is arising by spin-allowed electronic transitions of Co2+ ions in tetrahedral site of topaz matrix through substitution of Si4+ ions.

Chlorophyll f production in two new subaerial cyanobacteria of the family Oculatellaceae.

Chlorophyll (Chl) f was recently identified in a few cyanobacteria as the fifth chlorophyll of oxygenic organisms. In this study, two Leptolyngbya-like strains of CCNU0012 and CCNU0013 were isolated from a dry ditch in Chongqing city and a brick wall in Mount Emei Scenic Area in China, respectively. These two strains were described as new species: Elainella chongqingensis sp. nov. (Oculatellaceae, Synechococcales) and Pegethrix sichuanica sp. nov. (Oculatellaceae, Synechococcales) by the polyphasic approach based on morphological features, phylogenetic analysis of 16S rRNA gene and secondary structure comparison of 16S-23S internal transcribed spacer domains. Both strains produced Chl a under white light (WL) but additionally induced Chl f synthesis under far-red light (FRL). Unexpectedly, the content of Chl f in P. sichuanica was nearly half that in most Chl f-producing cyanobacteria. Red-shifted phycobiliproteins were also induced in both strains under FRL conditions. Subsequently, additional absorption peak beyond 700 nm in the FRL spectral region appeared in these two strains. This is the first report of Chl f production induced by FRL in the family Oculatellaceae. This study not only extended the diversity of Chl f-producing cyanobacteria but also provided precious samples to elucidate the essential binding sites of Chl f within cyanobacterial photosystems.

Cation trivalent tune of crystalline structure and magnetic properties in coprecipitated cobalt ferrite nanoparticles

CoFe2O4, CoBi0.1Fe1.9O4, CoLa0.1Fe1.9O4, and CoAl0.1Fe1.9O4 nanoparticles were successfully synthesized by the coprecipitation method. After annealing at 700 °C for 5 h, the x-ray Diffractometer results confirm that a single phase of cobalt ferrite-based nanoparticles is obtained, which is suitable for ICDD 22-1086. The addition of Bi3+, La3+ and Al3+ ions to the cobalt ferrite nanoparticles modified the crystallite size and lattice constant. Trivalent metal cation substitution tunes the crystallite size which has also been confirmed by measuring the grains with Scanning Electron Microscope images. In the Far Transform Infra-Red curve, the addition of metal ions (Bi3+, La3+, and Al3+) to cobalt ferrite nanoparticles resulted in absorption peaks at the tetrahedral and octahedral sites without any additional absorption peaks. The VSM results showed that saturation magnetization decreased drastically in the presence of trivalent non-magnetic cations, which confirms the replacement of Fe3+ by trivalent non-magnetic cations. The kOe order of the coercive field was obtained in this experiment. The largest coercive field of the cobalt ferrite nanoparticles was obtained with the addition of La3+ ions, i.e. 3.67 kOe suggest to support both Jahn-Teller effect and strain-induced magnetism.

Multipeak dynamic magnetic susceptibility of a superparamagnetic nanoparticle suspended in a fluid

Linear response theory for the case of a uniaxially anisotropic superparamagnetic nanoparticle suspended in a fluid is developed for the situations where, along with the probing field, a stationary bias field is present. The built up description allows for both mechanisms of magnetic relaxation available to the particle: the internal (relaxation of the magnetic moment inside the particle) and external (relaxation together with the particle body due to its Brownian orientation diffusion in a fluid). In this framework, longitudinal dynamic magnetic susceptibility of such a particle is considered. It is confirmed that at zero bias field, frequency dependence of the out-of-phase component of the dynamic susceptibility (absorption spectrum) has two maxima if anisotropy energy is only several times greater than thermal energy. The presence of these peaks is a direct consequence of the bistability of uniaxial magnetic nanoparticles. The magnetizing field changes position and height of these maxima. Moreover, it is shown that in a presence of the bias the spectrum can acquire a third maximum if the Brownian rotation of the suspended particle is retarded with respect to establishment of the intrinsic magnetic equilibrium in it. Necessary conditions for such a situation are analyzed, and criteria for the possible appearance of the additional third absorption peak are indicated.

Optical conductivity of an anharmonic large polaron gas at weak coupling

In a polar solid, electrons or other charge carriers can interact with the phonons of the ionic lattice, leading to the formation of polaron quasiparticles. The optical conductivity and optical absorption spectrum of a material are affected by this electron-phonon coupling, most notably leading to an absorption peak in the midinfrared region. Recently, a model Hamiltonian for anharmonic electron-phonon coupling was derived [M. Houtput and J. Tempere, Phys. Rev. B 103, 184306 (2021)] that includes both the conventional Fr\"ohlich interaction as well as an interaction in which an electron interacts with two phonons simultaneously. In this article, we calculate and investigate the optical conductivity of the anharmonic large polaron gas, and we show that an additional characteristic absorption peak appears due to this one-electron--two-phonon interaction. We calculate a semianalytical expression for the optical conductivity $\ensuremath{\sigma}(\ensuremath{\omega})$ at finite temperatures and weak coupling using the Kubo formula. The electronic and phononic contributions can be split and treated separately, such that the many-body effects of the electron gas may be taken into account through the well-known dynamical structure factor $S(\mathbf{k},\ensuremath{\omega})$. From the resulting optical conductivity, we calculate the polaron effective mass, an estimate for the electron-phonon scattering times, and the optical absorption spectrum of the anharmonic polaron gas. It is shown that the effects are negligible for four common III-V semiconductors (BN, AlN, BP, AlP) in the zinc-blende structure, which justifies the commonly used harmonic approximation in these materials. We show that alongside the well-known polaron absorption peak at the phonon energy $\ensuremath{\hbar}{\ensuremath{\omega}}_{\text{LO}}$, the one-electron--two-phonon interaction leads to an additional absorption peak at $2\ensuremath{\hbar}{\ensuremath{\omega}}_{\text{LO}}$. We propose this absorption peak as an experimentally measurable indicator for non-negligible one-electron--two-phonon interaction in a material, since the height of this peak is proportional to the strength of this anharmonic interaction.

Passive and active low frequency sound absorption performance of the finite and large sized micro-perforated panel absorber on oblique incidence condition

This paper presents a comprehensive investigation on the passive and active low frequency sound absorption performance of the finite and large sized micro-perforated panel absorber (FLS-MPPA) for oblique incidence excitation (OIE), which is of great significance for the engineering implementation of this technic. The theoretical model of the FLS-MPPA is firstly established by applying the modal analysis approach. It is also validated by experimental test. Then, the passive sound absorption performance is explored and the underlying physical mechanisms of these peculiar findings are investigated thoroughly. Finally, the active control performance (applying point source to actively control the sound field) and physical mechanism of the sound absorption improvement of the FLS-MPPA are analyzed. Results obtained demonstrate some key findings. The high order cavity modes excited by OIE reflect most of the incident sound power and have little contribution to the sound absorption in the low frequency range owing to their strong mutual coupling effects and being greatly excited with high modal amplitudes. They also cannot produce additional sound absorption peaks due to their wide resonant frequency band. Weakening such mutual coupling effects can improve the sound absorption and produce additional absorption peaks. The low frequency sound absorption of the FLS-MPPA is significantly improved with control and the achievable maximum sound absorption coefficient is slightly greater than the difference between 1 and the sound power reflection coefficient of the MPP, which validates the feasibility of the active control method for OIE. The reflected sound power induced by the cavity modes is highly reduced and part of the reflected sound power produced by the MPP can even be absorbed by these modes when their amplitudes are reduced to the optimal value, which is the physical nature of the active control. Sensing and controlling the cavity sound field in the corner achieves almost equal sound absorption improvement as that of the optimal control state, based on which the error sensing strategy is constructed.

Dynamic sound absorption characteristics of a series piezoelectric acoustic absorber regulated by voltage.

A piezoelectric acoustic absorber composed of double micro-perforated panels (MPPs) and their back cavity is studied in this paper. The outer layer of the MPP absorber is a common metal MPP, and the inner layer is a piezoelectric MPP made of polyvinylidene fluoride (PVDF) film. When an alternating voltage is applied to the polyvinylidene fluoride (PVDF)-micro-perforated panel (MPP), it can be excited to generate different structural vibration modes, which can bring an additional absorption peak to the absorption performance curve of the piezoelectric acoustic absorber. The numerical simulation and experimental results indicate that the frequency and sound absorption coefficient of the additional sound absorption peak are closely related to the voltage parameters. Especially when the frequency of the alternating voltage is close to the eigen-frequency of PVDF-MPP, the additional sound absorption peak is more significant. Therefore, the absorption coefficient of the piezoelectric acoustic absorber at the corresponding frequency can be effectively enhanced by appropriately adjusting the parameters of the excitation voltage. This method of selectively and specifically improving the sound absorption performance of the required frequency band is very effective in reducing the noise in the dynamic change.

Characterization of the H2O+CO2 continuum within the infrared transparency windows

Absorption spectra of humidified CO2 have been recorded at room temperature by cavity enhanced absorption techniques (CRDS and OFCEAS): (i) in three spectral ranges of the 1.6 µm window (5720–6045 cm−1; 6390–6460 cm−1 and 6570–6665 cm−1), (ii) in four narrow spectral intervals of the 2.3 µm window (4243–4255 cm−1; 4301.3–4302 cm−1; 4421.5–4440 cm−1 and 4518–4535 cm−1), and (iii) around 2853 cm−1. All these spectral ranges are situated in transparency windows of both H2O and CO2. The binary absorption coefficients (BCO2−H2O+BH2O−CO2)are retrieved from low pressure spectra (<1 atm) recorded with different molar fractions of water vapor in CO2 after subtracting the H2O and CO2 local monomer contributions and the self-continuum contribution of each species (i.e. H2OH2O and CO2CO2). Experimental room temperature binary coefficients are then compared to the only available empirical model based on line shape profiles with χ-factors. This model well reproduces our experimental values on the low- and high-frequency edges of the 1.6 µm window and gives a relatively good agreement for the 2853 cm−1 data point. Larger differences are observed in the 2.3 µm window where the calculated values are underestimated by a factor of 3. Around 6000 cm−1, an additional absorption peak is observed which is tentatively interpreted as a collision induced absorption band due to the simultaneous excitation of the H2O and CO2 molecules.

Effects of the Structure and Temperature on the Nature of Excitons in the Mo0.6W0.4S2 Alloy.

We studied the nature of excitons in the transition metal dichalcogenide alloy Mo0.6W0.4S2 compared to pure MoS2 and WS2 grown by atomic layer deposition (ALD). For this, optical absorption/transmission spectroscopy and time-dependent density functional theory (TDDFT) were used. The effects of temperature on A and B exciton peak energies and line widths in optical transmission spectra were compared between the alloy and pure MoS2 and WS2. On increasing the temperature from 25 to 293 K, the energy of the A and B exciton peaks decreases, while their line width increases due to exciton–phonon interactions. The exciton–phonon interactions in the alloy are closer to those for MoS2 than those for WS2. This suggests that exciton wave functions in the alloy have a larger amplitude on Mo atoms than that on W atoms. The experimental absorption spectra could be reproduced by TDDFT calculations. Interestingly, for the alloy, the Mo and W atoms had to be distributed over all layers. Conversely, we could not reproduce the experimental alloy spectrum by calculations on a structure with alternating layers, in which every other layer contains only Mo atoms and the layers in between also contain W atoms. For the latter atomic arrangement, the TDDFT calculations yielded an additional optical absorption peak that could be due to excitons with some charge transfer character. From these results, we conclude that ALD yields an alloy in which Mo and W atoms are distributed uniformly among all layers.

Enhanced Low-Frequency Sound Absorption of a Porous Layer Mosaicked with Perforated Resonator.

A composite structure composed of a porous-material layer mosaicked with a perforated resonator is proposed to improve the low-frequency sound absorption of the porous layer. This structure is investigated in the form of a porous-material matrix (PM) and a perforated resonator (PR), and the PR is a thin perforated plate filled with porous material in its back cavity. Theoretical and numerical models are established to predict the acoustic impedance and sound absorption coefficient of the proposed structure, and two samples made of polyurethane and melamine, respectively, are tested in an impedance tube. The predicted results are consistent with that of the measured. Compared with a single porous layer with the same thickness, the results show that the designed structure provides an additional sound absorption peak at low frequencies. The proposed structure is compact and has an effective absorption bandwidth of more than two octaves especially below the frequency corresponding to 1/4 wavelength. A comparison is also made between the sound absorption coefficients of the proposed structure and a classical micro-perforated plate (MPP), and the results reveal equivalent acoustic performance, suggesting that it can be used as an alternative to the MPP for low–mid frequency sound absorption. Moreover, the influences of the main parameters on the sound absorption coefficient of PPCS are also analyzed, such as the hole diameter, area ratio, flow resistance, and porous-material thickness in the PR. The mechanism of sound absorption is discussed through the surface acoustic impedance and the distributions of particle velocity and sound pressure at several specific frequencies. This work provides a new idea for the applications of the thin porous layer in low- and medium-frequency sound absorption.

Dual-Band, Polarization-Insensitive, Ultrathin and Flexible Metamaterial Absorber Based on High-Order Magnetic Resonance

We demonstrate a dual-band, polarization-insensitive, ultrathin and flexible metamaterial absorber (MA), based on high-order magnetic resonance. By exploiting a flexible polyimide substrate, the thickness of MA came to be 1/148 of the working wavelength. The absorption performance of the proposed structure was investigated for both planar and bending models. In the case of the planar model, a single peak was achieved at a frequency of 4.3 GHz, with an absorption of 98%. Furthermore, additional high-order absorption peaks were obtained by the bending structure on a cylindrical surface, while the fundamental peak with a high absorption was maintained well. Our work might be useful for the realization and the development of future devices, such as emitters, detectors, sensors, and energy converters.

Terahertz Spectral Properties of 5-Substituted Uracils

Applications of terahertz time-domain spectroscopy (THz-TDS) in the fields of chemistry and biomedicine have recently received increased attention. Specifically, THz-TDS is particularly effective for the identification of alkaloid molecules, because it can distinguish the vibration types of base molecules in the THz band and provide a direct characteristic spectrum for the configuration and conformation of biomolecules. However, when THz-TDS technology is used to identify alkaloid molecules, most of them are concentrated in the 0.1–3.0 THz band, limiting the amount of information that can be obtained. In this work, a wide-spectrum THz-TDS system was independently built to explore the absorption spectra of uracil and its 5-substituents in the range of 1.3–6.0 THz. We found that, in the THz band, uracil and its 5-substituents have similar absorption peaks near 4.9 and 3.3 THz, while the 5-substituents have an additional absorption peak in the range of 1.5–2.5 THz. This absorption peak is red-shifted as the relative atomic mass of the 5-substituted atoms increases. Gaussian software was adopted to calculate the absorption spectra of the samples. The simulation conclusions were in good agreement with the experimental results, revealing that the vibration of the base molecule at low frequencies can be attributed to the inter-molecular vibration. This work demonstrates that THz-TDS technology can be used to accurately identify biomolecules with similar molecular structures, reflecting the importance of molecular structure in biological activity.

Synthesis of gold nanoparticles by the spark discharge method for visible plasmonics

This work demonstrates synthesis of metal Au nanoparticles with a plasmon resonance in the visible optical region by the spark discharge method in atmosphere of argon of purity 6.0. With raising of sintering temperature from 25 to 950 °C, the morphology of synthesized Au nanoparticles changed from agglomerates to individual particles with decreasing the median size from 270 to 90 nm according to aerosol spectrometer. While by transmission electron microscopy primary nanoparticles with a gold crystalline structure with sizes in range from 5 to 120 nm were observed. Synthesized nanoparticles ensembles had broad absorption peaks with maximum in the visible optical region with peak positions approximately at 490 nm. High temperature sintered particles had a spherical shape and an additional absorption peak at approximately 640 nm.

Electromagnetic Properties and Microwave Absorption of Electrospun Fe2O3-Carbon Composite Nanofibers with Particle–Nanorod Structure

Multifunctional composite nanostructure prepared via electrospinning has attracted wide attention. In this study, Fe2O3-carbon composite nanofiber with particle–nanorod structure was successfully prepared via electrospinning and followed calcination. Then, the electromagnetic properties of this material have been fully characterized, and the influence of different preparation conditions on these properties has been studied. In addition, compared to pure [Formula: see text]-Fe2O3 nanoparticles and hollow Fe2O3 nanofibers, the composite nanofibers with a thickness of 2.64[Formula: see text]mm exhibited an additional absorption peak at a frequency of 13.92[Formula: see text]GHz and an enhancement in absorption at a frequency of 15.45[Formula: see text]GHz, which may be attributed to the increase in electrical loss introduced by amorphous carbon and the enhanced magnetic loss resulting from the multi-stage reflection introduced by the particle–nanorod structure. This study shows that the composite of Fe2O3 and carbon, and the introduction of the particle–nanorod structure can improve the microwave absorption efficiency of materials, and more nanocomposites can be designed like this to further improve their electromagnetic properties and absorption efficiency in the future.