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Iron Oxide and Iron Sulfide Films Prepared for Dye-Sensitized Solar Cells
摘要： In this paper, the prospects of iron oxide ?lms and their sul?dation for dye-sensitized solar cells (DSSC) are reviewed. Iron oxide thin ?lms were prepared by hollow cathode plasma jet (HCPJ) sputtering, with an admixture of oxygen in the argon working gas and with an iron nozzle as the sputtering target. The discharge was powered by a constant current source in continuous mode and by a constant voltage source in pulsed mode. Plasma composition was measured by an energy-resolved mass spectrometer. Moreover, secondary electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), absorption and Raman spectra of the ?lms are presented. Strong correlation between the color of the iron oxide ?lm and its phase composition was revealed. Iron oxide ?lms were sul?ded at 350 °C. A relatively clean pyrite phase was obtained from the magnetite, while the marcasite with admixture of the pyrite phase was obtained from the hematite. Low in?uence of sul?dation on the ?lms’ microstructure was demonstrated.
关键词： iron oxide,absorption spectroscopy,hollow cathode plasma jet,dye-sensitized solar cell,iron sul?de
更新于2025-09-23 15:19:57
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Spin-wave excitation and critical angles in a hybrid photon-magnon-coupled system
摘要： We studied “strongly enhanced” excitations of magnetostatic spin-waves in a hybrid magnon-photon-coupled system consisting of an inverted split-ring resonator and an yttrium iron garnet film. The backward-volume magnetostatic wave, magnetostatic surface wave, forward-volume magnetostatic wave modes, as well as multiple mixed modes were observed according to the direction of externally applied magnetic fields with respect to the spin-wave propagation direction. From experimental measurements, we found that there exist certain characteristic angles, which is to say, critical angles (θc), whereby the group velocity of the excited spin-wave modes reaches zero, along with a single ferromagnetic resonance peak. Furthermore, we analytically derived the critical angles as sin θc = (Heff /H){2 ? (1 + μ0Ms/Heff )sin2 fc}1/2, where Heff is the effective magnetic-field strength, H the externally applied field strength, and μ0Ms is the saturation magnetization. This analytical form is in quantitative agreement with estimations from experimentally observed spin-wave modes. This work not only provides a better understanding of multiple-mode spin-wave excitations in given field directions with the help of photon-magnon coupling, but also offers better coupling controllability based on the change of the external magnetic field direction.
关键词： inverted split-ring resonator,critical angles,photon-magnon coupling,spin-wave,yttrium iron garnet
更新于2025-09-23 15:19:57
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Enhancement of magneto-optical properties in magnetic photonic crystal slab waveguide based on yttrium iron garnet
摘要： In this work, a polarization-independent waveguide based on magnetic photonic crystal (MPC) with a triangular lattice of air holes in Yttrium Iron Garnet (YIG) slab grown on alumina (Al2O3) substrate is proposed, where both TE-like and TM-like periodic band gaps overlap. YIG is well known for its attracting magneto-optical (MO) properties and used to produce a coupling between the TE and TM modes. Thus, a nonreciprocal effect can be obtained by applying an external magnetic field parallel to the direction of propagation. At 1550 nm, the complete photonic band gap is simulated and optimized using the three dimensional plane-wave expansion method. The aim of this study is to enhance Faraday rotation (FR) while maintaining a low modal birefringence. A numerical analysis in function of magnetic gyration (g) has been reported, using the BeamProp software. The results reveal a proportional relation between FR, ?n and g, such for g = 0.5, a large FR of 26.11×104 °/cm with ?n = 7×10–6. The results show a real improvement of this MPC structure based on YIG with larger FR, lower modal birefringence and minimal losses. The notable enhancement in the MO behaviour could improve the performance of optical isolators, and makes it suitable for nonreciprocal devices.
关键词： modal birefringence,magneto-optical properties,Yttrium Iron Garnet,Faraday rotation,magnetic photonic crystal
更新于2025-09-23 15:19:57
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Construction of the 0D/2D heterojunction of Ti3C2Tx MXene nanosheets and iron phthalocyanine quantum dots for the impedimetric aptasensing of microRNA-155
摘要： A promising nanocarrier of the complementary DNA (cDNA) toward miRNA-155 was synthesized on the basis of the nanohybrid type of Ti3C2Tx MXene nanosheets decorated using iron phthalocyanine quantum dots (FePc QDs) (denoted as Ti3C2Tx@FePcQDs) to construct a novel ultrasensitive impedimetric aptasensing system for microRNA-155 (miRNA-155). Owing to π–π* stacking interaction between Ti3C2Tx nanosheets and FePc QDs, the homogeneous nanostructure of the Ti3C2Tx@FePcQD nanohybrid that comprises mixed-valence states (Ti2+/Ti3+ and Fe2+/Fe3+), multicomponent (Ti-O and Ti-C), and various N-related groups was achieved. The constructed Ti3C2Tx@FePcQDs-based aptasensor displayed an ultrahigh sensitivity for detecting miRNA-155 with a low detection limit of 4.3 aM (S/N = 3) within the miRNA-155 concentration ranging from 0.01 fM to 10 pM. Compared with the individual component-based aptasensors and other reported miRNA-155 aptasensors, the proposed impedimetric aptasensing system exhibited substantial merits of a feasible preparation process, non-use of labels or electrochemical indicators, fast response time, and comprehensive sensing performances for detecting miRNA-155. This strategy for determining miRNAs can extensively be applied as the platform for anchoring other kinds of aptamers in detecting diverse targets, thus indicating its great potential application for the early diagnosis of cancer biomarkers.
关键词： Impedimetric aptasensing,Iron phthalocyanine,Nanohybrid,Detection of miRNA-155,Ti3C2Tx MXene nanosheets,Electrochemical aptasensor
更新于2025-09-23 15:19:57
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Synthesis of highly fluorescent and water soluble graphene quantum dots for detection of heavy metal ions in aqueous media
摘要： Fluorescent graphene quantum dots (GQDs) are nanomaterials which possess unique properties that show great potential in different applications. In this work, GQDs were synthesized using graphene oxide (GO) as precursor via thermal treatment at high temperature. The obtained GQDs were highly fluorescent and were suitable for the determination of heavy metal ions. X-ray diffraction, FTIR spectroscopy, and UV visible spectroscopy confirm the formation of GQDs. TEM images show that formed GQDs have size ranging from 2 to 10 nm. Emission profile of aqueous GQDs was taken by exciting GQDs at different wavelength. The intensity of GQDs remains the same for 4–5 months. Furthermore, as prepared, GQDs were used for selective recognition of Fe3+, Pb+2, and Cr3+ from the bunch of different metal ions in aqueous media. Lower limit of detection obtained for Fe3+, Cr3+ and Pb2+ using GQDs were 50, 100 and 100 nM, respectively, which indicates that the GQDs can be utilized as a promising material for sensing of the heavy metal ions.
关键词： GQDs,Lead and chromium ions,Iron,Fluorescence
更新于2025-09-23 15:19:57
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Spin pumping and laser modulated inverse spin Hall effect in yttrium iron garnet/germanium heterojunctions
摘要： In this work, undoped semiconductors, germanium (Ge) and germanium tin (GeSn), were grown on ferrimagnetic insulator yttrium iron garnet (YIG) thin ?lms using ultra-high vacuum molecular beam epitaxy. The crystallinity of the structure was determined from x-ray diffraction and high-resolution transmission electron microscopy combined with energy dispersive x-ray spectroscopy. Both spin pumping and inverse spin Hall effects (ISHEs) of YIG/Ge and YIG/GeSn heterojunctions have been investigated with the help of broadband ferromagnetic resonance (FMR). We observe that the spin mixing conductances of YIG/Ge (60 nm) and YIG/GeSn (60 nm) are 5.4 (cid:2) 1018 m(cid:3)2 and 7.2 (cid:2) 1018 m(cid:3)2, respectively, responsible for giant spin current injection. Furthermore, it is found that spin pumping injects giant spin current from ferrimagnetic YIG into the Ge semiconductor. The infrared laser modulated ISHE was examined using heavy metal platinum as a spin current collector. Also, it has been noted that the variation in the power of laser irradiation signi?cantly changed the ISHE voltage of YIG/Ge/Pt spin junctions, saturated magnetization, FMR linewidth, and Gilbert damping parameter of YIG, which could be attributed to the laser-induced thermal effect. The outcomes from this study are promising for the development of Ge-based spintronic and magnonic devices.
关键词： germanium tin,magnonics,germanium,spin pumping,inverse spin Hall effect,yttrium iron garnet,spintronics
更新于2025-09-23 15:19:57
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Iron Oxide Nanopowders Obtained via Pulsed Laser Ablation, for Supercapacitors
摘要： Nano-sized magnetite powders with addition of iron nitrides were synthesized via pulsed laser ablation (PLA) of an iron target in atmospheric air. A series of iron oxide nanopowders with various phase compositions (ranging from magnetite to hematite) and structures (from 2D lamellas and spherical nanoparticles to continuous 3D structures) were prepared via heat treatment of the initial (as-synthesized) powder at temperatures in the range 200–500°C. The powders were introduced into the composition of carbon paste electrodes (CPEs). The capacitive characteristics of the electrodes prepared were studied in comparison to a commercial electroexplosive iron oxide powder. The capacitances of electrodes were matched to the structural characteristics of the materials and their phase compositions. With the chosen electrode-preparation method, the powder heat-treated at 500°С (sample Fe/500) showed the highest capacitance. The potential of the studied ultrafine materials based on ablative iron oxide was shown for use in electrodes for supercapacitors.
关键词： supercapacitor,specific capacitance,pulsed laser ablation,iron oxides,nanopowder
更新于2025-09-23 15:19:57
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Manipulation of the Size and Phase Composition of Yttrium Iron Garnet Nanoparticles by Pulsed Laser Post-Processing in Liquid
摘要： Modi?cation of the size and phase composition of magnetic oxide nanomaterials dispersed in liquids by laser synthesis and processing of colloids has high implications for applications in biomedicine, catalysis and for nanoparticle-polymer composites. Controlling these properties for ternary oxides, however, is challenging with typical additives like salts and ligands and can lead to unwanted byproducts and various phases. In our study, we demonstrate how additive-free pulsed laser post-processing (LPP) of colloidal yttrium iron oxide nanoparticles using high repetition rates and power at 355 nm laser wavelength can be used for phase transformation and phase puri?cation of the garnet structure by variation of the laser ?uence as well as the applied energy dose. Furthermore, LPP allows particle size modi?cation between 5 nm (ps laser) and 20 nm (ns laser) and signi?cant increase of the monodispersity. Resulting colloidal nanoparticles are investigated regarding their size, structure and temperature-dependent magnetic properties.
关键词： laser melting,yttrium iron oxide,monodisperse,laser fragmentation,phase transformation,garnet,perovskite,laser ablation,ferrimagnetic nanoparticles
更新于2025-09-23 15:19:57
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Bionic Repair of Thermal Fatigue Cracks in Ductile Iron by Laser Melting with Different Laser Parameters
摘要： Nodular iron brake discs typically fail due to serious thermal fatigue cracking, and the presence of graphite complicates the repair of crack defects in ductile iron. This study presents a novel method for remanufacturing ductile iron brake discs based on coupled bionics to repair thermal fatigue cracks discontinuously using bio-inspired crack blocking units fabricated by laser remelting at various laser energy inputs. Then, the ultimate tensile force and thermal fatigue crack resistance of the obtained units were tested. The microhardness, microstructure, and phases of the units were characterized using a digital microhardness meter, optical microscopy, scanning electron microscopy, and X-ray di?raction. It was found that the units without defects positively impacted both the thermal fatigue resistance and tensile strength. The unit fabricated at a laser energy of 165.6+19?15 J/mm2 had su?cient depth to fully close the crack, and exhibited superior anti-cracking and tensile properties. When the unit distance is 3 mm, the sample has excellent thermal fatigue resistance. In addition, the anti-crack mechanism of the units was analysed.
关键词： bionic crack blocked unit,repair discontinuously,thermal fatigue crack,ductile iron,laser remelting
更新于2025-09-23 15:19:57
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Dual-emission CdTe/AgInS2 photoluminescence probe coupled to neural network data processing for the simultaneous determination of folic acid and iron (II)
摘要： This work focused on the combination of CdTe and AgInS2 quantum dots in a dual-emission nanoprobe for the simultaneous determination of folic acid and Fe(II) in pharmaceutical formulations. The surface chemistry of the used QDs was amended with suitable capping ligands to obtain appropriate reactivity in terms of selectivity and sensitivity towards the target analytes. The implementation of PL-based sensing schemes combining multiple QDs of different nature, excited at the same wavelength and emitting at different ones, allowed to obtain a specific analyte-response profile. The first-order fluorescence data obtained from the whole emission spectra of the CdTe/AgInS2 combined nanoprobe upon interaction with folic acid and Fe(II) were processed by using chemometric tools, namely partial least-squares (PLS) and artificial neural network (ANN). This enabled to circumvent the selectivity issues commonly associated with the use of QDs prone to indiscriminate interaction with multiple species, which impair reliable and accurate quantification in complex matrices samples. ANN demonstrated to be the most efficient chemometric model for the simultaneous determination of both analytes in binary mixtures and pharmaceutical formulations due to the non-linear relationship between analyte concentration and fluorescence data that it could handle. The R2P and SEP% obtained for both analytes quantification in pharmaceutical formulations through ANN modelling ranged from 0.92 to 0.99 and 5.7e9.1%, respectively. The obtained results revealed that the developed approach is able to quantify, with high reliability and accuracy, more than one analyte in complex mixtures and real samples with pharmaceutical interest.
关键词： CdTe/AgInS2 combined nanoprobe,Artificial neural network,Iron,Partial least-squares,Folic acid
更新于2025-09-23 15:19:57