Review for Rare-Earth-Modified Perovskite Materials and Optoelectronic Applications

Efficient Design of Broadband and Low-Profile Multilayer Absorbing Materials on Cobalt-Iron Magnetic Alloy Doped with Rare Earth Element

Magnetic metal absorbing materials have exhibited excellent absorptance performance. However, their applications are still limited in terms of light weight, low thickness and wide absorption bandwidth. To address this challenge, we design a broadband and low-profile multilayer absorber using cobalt-iron (CoFe) alloys doped with rare earth elements (REEs) lanthanum (La) and Neodymium (Nd). An improved estimation of distribution algorithm (IEDA) is employed in conjunction with a mathematical model of multilayer absorbing materials (MAMs) to optimize both the relative bandwidth with reflection loss (RL) below -10 dB and the thickness. Firstly, the absorption performance of CoFe alloys doped with La/Nd with different contents is analysed. Subsequently, IEDA is introduced based on a mathematical model to achieve an optimal MAM design that obtains a balance between absorption bandwidth and thickness. To validate the feasibility of our proposed method, a triple-layer MAM is designed and optimized to exhibit wide absorption bandwidth covering C, X, and Ku bands (6.16-12.82 GHz) and a total thickness of 2.39 mm. Then, the electromagnetic (EM) absorption mechanisms of the triple-layer MAMs are systematically investigated. Finally, the triple-layer sample is further fabricated and measured. The experimental result is in good agreement with the simulated result. This paper presents a rapid and efficient optimization method for designing MAMs, offering promising prospects in microwave applications, such as radar-stealth technology, EM shielding, and reduced EM pollution for electronic devices.

Luminescent/Temperature-Sensing Properties of Multifunctional Rare-Earth Upconversion Kevlar Nanofiber Composite under 1550 nm

The unique properties of upconversion nanoparticles (UCNPs) are responsible for their diverse applications in photonic materials, medicine, analytics, and energy conversion. In this study, water-soluble rare-earth upconversion nanomaterials emitting green, yellow, and red light under 1550 nm excitation were synthesized. These nanomaterials were then integrated into water-soluble Kevlar nanofibers (KNFs) to fabricate ultra-thin composite films exhibiting favorable mechanical characteristics. The characterization of the products, along with their luminescent, mechanical, and temperature-sensing properties, was examined. The results indicate that the composite material exhibited varying colors based on the doped nanoparticles when subjected to 1550 nm excitation. The composite showed highly sensitive temperature-sensing properties, excellent luminescent characteristics, and superior mechanical strength. This study suggests that KNFs are effective carriers of UCNPs. This study offers a reference for the utilization of rare-earth upconversion in anti-counterfeiting displays, wearable health monitoring, and remote temperature sensing.

Optical and dielectric properties of divalent copper based double perovskite compound, Gd2CuTiO6

In this work, we have investigated high temperature dielectric properties and room temperature optical properties on rare earth ion based orthorhombic Gd2CuTiO6(GCTO). Optical properties like reflectance and band gap were determined from ultra-violet visible (UV-Vis) diffuse reflectance spectroscopy technique and photoluminescence (PL) spectrum. The compound exhibited substantial optical absorption and emission in the visible region. Our findings reveal the presence of an intermediate band, as evidenced by the difference between the band gap values obtained from the Tauc plot using the diffuse reflectance spectrum (3.07 eV) and the PL spectrum (2.4 eV). Furthermore, thermogravimetric analysis demonstrated high thermal stability with <0.4% change in mass over a wide temperature range of 30 °C-1200 °C in air environment. Moreover, lead-halide free compound, GCTO is highly thermally stable oxide double perovskite with wide band gap and absorption in the UV-Vis range are highly suitable for optical applications In addition, dielectric properties of the compound have been examined using impedance spectroscopy as a function of frequency ranging from 500 Hz to 1 MHz and temperature between 300 K and 550 K. Compounds with relaxor behaviour at high temperatures and high thermal stability are desired for several applications. Because of the cation disorders present in this compound, GCTO displays dielectric relaxor behaviour indicative of a distribution of relaxation times. Furthermore, the frequency-dependent modulus illustrated a thermally activated conduction mechanism. Cole-Cole plots of electrical modulus suggest prominent grain contribution above 350 K.

Integrated experimental and theoretical studies on structural and magnetic properties of thin films of double perovskite ruthenates: Ba2DyRuO6 & Sr2DyRuO6

Thin films of double perovskite ruthenates, viz., Ba2DyRuO6 (BDRO) and Sr2DyRuO6 (SDRO), have been successfully grown on a SrTiO3 substrate using the pulsed laser deposition technique. The BDRO samples crystallizes in cubic structure, while SDRO exhibits monoclinic structure as revealed in their X-Ray diffraction examination. Temperature-dependent magnetization measurements suggest the presence of ferromagnetism in BDRO, while paramagnetism is present for the SDRO thin film. Surprisingly, both films show canted antiferromagnetism at ∼T = 5 K as revealed in their isothermal magnetization curves. The inverse susceptibility has been fitted to the Curie-Weiss law for the SDRO sample, where the Curie temperature (TC ∼ -336.6 K) has been obtained, thus suggesting the prevalence of antiferromagnetic interactions. The existence of the canted magnetism at a lower temperature may be attributed to the Dzyaloshinskii-Moriya (D-M) interactions in the monoclinic SDRO sample due to structural distortion. However, the emergence of canted antiferromagnetism at lower temperatures (5 K) in the BDRO sample with cubic symmetry having no D-M interactions may be attributed to the various modifications at the surface of the thin films. Overall, a comparison made between the magnetic properties of both the thin films i.e., BDRO & SDRO, reveals the suppression of bulk magnetic ordering when compared to their bulk counterparts. The possible reason for the absence of any magnetic ordering in these thin films may be due to any modifications in superexchange interactions, any exchange bias, stress-strain, or uncompensated spins present in these types of thin films. UV-visible measurements for both the samples reveal a direct influence of the A-site element (Sr/Ba) on their band gaps, i.e., 3.66 eV and 2.59 eV for BDRO and SDRO samples, respectively, hence suggesting their insulating nature. We have also carried out first principles calculations with DFT using the CASTEP software to gain more insights into the experimental data. These thin films with insulating-antiferromagnetic properties may be crucial for "spintronics devices".

Impact of Layered Perovskite Oxide La0.85Yb0.15AlO3 on Structure and Transport Properties of Polyetherimide

This study aims to improve properties of Ultem^® polyetherimide (PEI) by incorporating up to 2 wt% additives of the perovskite oxide La_0.85Yb_0.15AlO₃ (LYA). The structure of dense PEI/LYA films was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) in combination with an analysis of their elemental composition using energy-dispersive spectroscopy (EDS). The PEI/LYA films exhibit a two-layer structure. Contact angle measurements revealed hydrophilization of the membrane surface enriched with the perovskite. The transport properties were tested via gas separation and pervaporation processes. The separation selectivity of He/N₂ and O₂/N₂ gas pairs increased with the growth of the LYA content in the membranes. Pervaporation of a methanol(MeOH)-cyclohexane(CH) mixture was effective due to the high sorption of MeOH in the PEI/LYA membranes. The maximal pervaporation separation index was found for the PEI/LYA(2%) membrane.

LnNP@ZIF8 Smart System for In Situ NIR-II Ratiometric Imaging-Based Tumor Drug Resistance Evaluation

Just-in-time evaluation of drug resistance in situ will greatly facilitate the achievement of precision cancer therapy. The rapid elevation of reactive oxygen species (ROS) is the key to chemotherapy. Hence, suppressed ROS production is an important marker for chemotherapy drug resistance. Herein, a NIR-II emission smart nanoprobe (LnNP@ZIF8, consisting of a lanthanide-doped nanoparticle (LnNP) core and metal-organic framework shell (ZIF8)) is constructed for drug delivery and in vivo NIR-II ratiometric imaging of ROS for tumor drug resistance evaluation. The drug-loaded nanoprobes release therapeutic substances for chemotherapy in the acidic tumor tissue. As the level of ROS increases, the LnNPs shows responsively descending fluorescence intensity at 1550 nm excited by 980 nm (F1550, 980Ex), while the fluorescence of the LnNPs at 1060 nm excited by 808 nm (F1060, 808Ex) is stable. Due to the ratiometric F1550, 980Ex/F1060, 808Ex value exhibiting a linear relationship with ROS concentration, NIR-II imaging results of ROS change based on this ratio can be an important basis for determining tumor drug resistance. As the chemotherapy and resistance evaluation are explored continuously in situ, the ratiometric imaging identifies drug resistance successfully within 24 h, which can greatly improve the timeliness of accurate treatment.

Editorial for Special Issue: Advanced Materials and Technologies in Nanogenerators

Nanogenerators, based on Maxwell's displacement current as the driving force, have inspired a new and developing field since their invention in 2006 [...].