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Defect influences on the photoactivity of ZnO nanoparticles prepared by a powdered coconut water (ACP) assisted synthesis have been studied. The crystalline phase and morphology of ZnO nanoparticles were effectively controlled by adjusting the calcination temperature (400−700 °C). An induced transition of hybrid Zn 5 (CO 3 ) 2 (OH) 6 /ZnO nanoparticles to single-phase ZnO nanoparticles was obtained at 480 °C. The morphological analysis revealed a formation of ZnO nanoparticles with semispherical (∼6.5 nm)-and rod-like (∼96 nm) shapes when the calcination temperatures were 400 and 700 °C, respectively. Photoluminescence characterizations revealed several defects types in the samples with V Zn and V O + being in the selfassembly of semispherical-and rod-like ZnO nanoparticles. The photocatalytic activity of the ZnO nanoparticles was examined by assessing the degradation of methylene blue in an aqueous solution under low-intensity visible-light irradiation (∼3 W m −2 ). The results point toward the self-assembly of semispherical-and rod-like ZnO nanoparticles that had significantly better photocatalytic activity (∼31%) in comparison to that of spherical-agglomerated-or near-spherical-like species within 120 min of irradiation. The possible photocatalytic mechanism is discussed in detail, and the morphology-driven intrinsic [V Zn +V O + ] defects are proposed to be among the active sites of the ZnO nanoparticles enhancing the photocatalytic activity.

Barium fluoride (BaF2) nanoparticles (NPs) with different sizes were produced through a hydrothermal microwave method (HTMW). We have found that microstructural strain is induced by the surface stress in the nanoparticles.

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The development of new magnetic refrigerants demands an effective investigation of materials with a large magnetocaloric effect in a wide temperature range. Herein, we report on the structural, magnetic, and magnetocaloric properties of the two-site disordered double perovskite GdSrCoFeO 6 prepared by the modified solid-state synthesis method. Temperature-dependent synchrotron X-ray diffraction analysis revealed that GdSrCoFeO 6 crystallizes in the orthorhombic phase (Pnma), with Gd 3+ /Sr 2+ and Co 2+/3+ /Fe 3+/4+ ions randomly distributed on the A-and B-sites, respectively. An observed lattice parameter anomaly around 60 K indicates the occurrence of the magnetoelastic coupling, which coincides with the presence of ferro/ferrimagnetic (FM/FiM) ordering below T C ≈ 65 K from the magnetic measurements. These results match well with our first-principles calculation prediction of low-temperature magnetic (FM/FiM) and electronic (insulating/metal) transitions related to a combined effect of Co and Fe shortand long-range competitions, crossings of spin state at Co ions, and the hybridization degree between Gd-4f and Co-3d states. Additionally, a modified Arrott plot and Kouvel−Fisher analysis were used to establish the nature of the magnetic phase transition in GdSrCoFeO 6 , yielding the critical exponent β = 1.46(6)/1.45(6), γ = 1.48(5)/1.17(2), and δ = 2.01(3)/1.80(5), respectively. The specific heat analysis reveals two well-defined broad peaks (∼10 and ∼70 K), which match well with a Schottky anomaly (Gd-4f) and the magnetic transition of FM/FiM to paramagnetic order, respectively. The magnetocaloric effect (MCE) analysis reveals a maximum magnetic entropy change ΔS M max ≈ 13 J kg −1 K −1 (at ∼8 K) under a field of 0−7 T. These results evidence that the Schottky anomaly and the magnetoelastic coupling seem to be key factors for driving further enhancements to the MCE in GdSrCoFeO 6 , making it a possible candidate for cryogenic applications.