Logo: to the web site of Uppsala University

Owing to their affordability and high theoretical capacity, metal dichalcogenides are attractive anode candidates for sodium-ion batteries (SIBs). Nonetheless, their practical deployment remains impeded by complex phase transitions and pronounced volume changes during cycling. In this work, a simple self-assembly strategy was employed to construct a porous MoS2/rGO/CoS2 nanocomposite, in which MoS2 microrods and CoS2 nanoparticles are intimately coupled within a reduced graphene oxide (rGO) matrix. The synergistic integration, facilitated by epitaxial growth of ZIF-67 on GO planes and Mo-MOF rods, imparts enhanced structural stability and upgrades reaction kinetics, thereby significantly boosting Na+ storage performance. The MoS2/rGO/CoS2 electrode exhibits an impressive reversible specific capacity of 541 mAh g- 1 at a current density of 0.1 A g- 1 after 90 cycles, as well as an outstanding ultrafast cycling charge/discharge capability of 291 mAh g- 1 at 1 A g- 1, retaining 61.39 % of its initial capacity over 500 cycles. This study presents a practical, straightforward approach to designing metal dichalcogenide heterostructures to enhance the performance of Na+ ion storage.

Hydrogen (H2) detection using metal-oxide semiconductor (MOS) sensors is often limited by insufficient active sites, slow surface reactions, and modest sensitivity. To overcome these constraints, we developed a highly responsive hydrogen sensor based on bimetallic palladium-silver (Pd-Ag) decorated zinc ferrite (ZnFe2O4, ZFO) nanoparticles synthesized via a low-temperature self-combustion route. Ag was incorporated during ZFO preparation (1-4 wt%), followed by post-synthesis surface decoration with Pd (0-1.25 wt%). Structural, morphological, and chemical analyses were performed using X-ray diffraction (XRD), Raman spectroscopy, fieldemission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Gas-sensing measurements demonstrate that Ag loading enhances the H2 response up to an optimum of 2 wt%, while co-decoration with 0.75 wt% Pd yields an exceptionally high response of 3500 % to 5000 ppm H2 at 350 degrees C, representing a 70-fold improvement over pristine ZFO. The enhanced performance originates from increased oxygen vacancies, a higher density of chemisorbed oxygen species, and synergistic chemical and electronic sensitization provided by Pd-Ag nanoclusters. Compared with previously reported monometallic-decorated or undecorated ZFO sensors, the Pd-Ag/ZFO system exhibits markedly superior sensitivity, selectivity, and response dynamics, highlighting its promise for next-generation hydrogen detection technologies.

In this work, two major sources of pollution: (1) Water pollution due to heavy metals, and (2) Electromagnetic wave (EMW) pollution, often regarded as the fourth category of pollution (after air, water, and soil pollution) are addressed. A unique bio-based triphasic nanocomposite (Fe3O4/alpha-Fe2O3/carbon) is synthesized and its superior properties are demonstrated to address both types of environmental pollution. The nanocomposite, derived from lightweight apple tree roots, is used for Pb (II) ion removal from aqueous solutions via adsorption and magnetic separation. The biomass-derived highly porous biochar decorated with iron-oxide showed adsorption efficiency of nearly 100% and corresponding capacity of 149 mg.g-1 under optimal conditions for initial Pb (II) concentration of 50 mg.L-1. Furthermore, a remarkable adsorption capacity of 731 mg.g-1 is achieved using lower amount of the adsorbent for a slightly lower efficiency (97%). In addition, the mesoporous composite showed excellent EMW absorption efficiency with effective absorption bandwidth of 7.8 GHz and reflection loss of -61.7 dB, arising from very good impedance matching, and high dielectric and magnetic losses. This work establishes the multifunctional properties of the synthesized composite, and addresses the UN Sustainable Development Goal (SDG) 6 (Clean water and sanitation) and SDG 13 (Climate action, including pollution management). The synthesis and exploration of a multifunctional biochar/iron-oxide triphasic nanocomposite is reported to address two UN Sustainable Development Goals (SDGs), SDG 6 (Clean water and sanitation) and SDG 13 (Climate action, including pollution management). The performance of the nanocomposite as an adsorbent for the toxic heavy metal (Pb) from water, and for the absorption of harmful electromagnetic radiation is investigated. image

Efficient control of the structural, magnetic and electrical properties of Rare-earth (RE) based perovskites (ABO₃) is crucial for advanced spintronic applications and can be achieved by means of site-specific substitution. In this comprehensive study, we explore the role of (Nd)_A-site and (Mn)_B-site co-substitution on the physical properties of pristine LaCoO₃ perovskite. The resulting compound La_0.5Nd_0.5Co_0.5Mn_0.5O₃ (LNCMO) with an orthorhombic (Pbnm) crystal structure (a =5.4811(4) Å, b = 5.5074(4) Å and c =7.7491(5) Å) exhibits a significantly reduced Jahn-Teller distortion (JT) compared to pristine LaCoO₃ with a monoclinic (I2/a) structure. The ac-magnetic susceptibility χ(T, f, H_dc) measurements and wait time dependence of the isothermal magnetization M(t) provide clear evidence for the re-entrant spin-glass-like behavior with freezing temperature T_SG =133 K below the ferrimagnetic Curie temperature (T_FiM ∼137.4 K). Additionally, the asymmetric response of magnetic relaxation in the system to positive and negative temperature cycling well below the freezing temperature has been explained by means of the hierarchical model. Furthermore, a giant coercivity (H_C ∼14 kOe) and remanence (M_R ∼ 6440 emu mol⁻¹ ) with weak loop-asymmetry indicates the presence of large magnetic anisotropy in LNCMO, evidenced by a high magneto-crystalline anisotropy field (H_K ∼80 kOe) and anisotropy constant (K₁ ∼ 1.45 × 10⁷ erg cm⁻³). The unique electronic structure of trivalent Nd (5f³) and mixed valent Mn (3d⁴/3d³) with spin-orbit coupling energies 4 eV and 11.43 eV/10.51 eV, respectively and competing exchange interaction (∼0.67 meV) between Mn and Co cations in different pathways results in enhanced magnetic-order parameters. Moreover, the co-substitution results to a pseudo-first order like state close to the spin-state transition H^* of Co (S = 0 → 2) which has been verified by the modified Arrott plot analysis yielding critical exponents β = 0.67, γ = 1.44 and δ = 3.13. A field-induced metamagnetic transition H_T emerges in the range 30 K ⩽T⩽ 130 K which has been mapped along with other parameters resulting in a H-T phase diagram which clearly distinguishes various magnetic phases and sharp crossover between the different states providing a clear and vivid picture of the overall magnetic structure of LNCMO.

We describe a magnetic relation in analogy to the well-known dielectric Lyddane-Sachs-Teller relation [R. H. Lyddane et al., Phys. Rev. 59, 673 (1941)]. This magnetic relation follows directly from the model equations for nuclear induction due to fast oscillating electromagnetic fields [F. Bloch, Phys. Rev. 70, 460 (1946)] and relates the static permeability with the product over all ratios of antiresonance and resonance frequencies associated with all magnetic excitations within a given specimen. The magnetic relation differs significantly from its dielectric analog where the static properties are related to ratios of the squares of resonance frequencies. We demonstrate the validity of the magnetic Lyddane-Sachs-Teller relation using optical magnetization data from terahertz electron magnetic resonance spectroscopic ellipsometry measurements in the presence of an external magnetic field on an iron-doped semiconductor crystal of gallium nitride.

There has recently been a fundamental need to develop high efficiency microwave absorbers to reduce electro-magnetic pollution. It is often very difficult to obtain superior absorption with only one material, so we have explored composites using fillers of activated carbon derived from biological material (oleaster seeds) and resin (apricot tree gum) with Fe₃O₄ in a paraffin wax matrix to improve the dielectric properties and achieve a high specific surface area. A 1 mm thick layer of a Fe₃O₄ + resin (FEOR), with the magnetic nanoparticles anchored to the gum, resulted in a reflection loss of −71.09 dB. We compared this with the results for composites using a filler of Fe₃O₄ + activated carbon, and one with a three-component filler of Fe₃O₄ + activated carbon + resin which had a very porous structure that had a direct effect on the surface polarization. However, the FEOR sample had near-ideal impedance matching, close to 1, which resulted in high absorption performance. In addition, the presence of defects improves microwave attenuation by dipole polarization and charge carrier trapping. This work suggests the use of new types of biomaterials to increase microwave absorption.