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Soft materials are attracting much attention for the development of biostructures able to mimic the movement of natural systems by remote actuation. Multi-sensitive hydrogels are among the best materials for obtaining dynamic and biocompatible soft structures for soft actuators and related biomedical devices. Nevertheless, bioinks based on naturally occurring and stimuli responsive hydrogels able to be 3D printed continues being a challenge for advanced applications. In this work 3D printable electrically and magnetically responsive, non-cytotoxic, hybrid hydrogels based on alginate and zero monovalent iron nanoparticles (NPs) are presented. The effect of NPs addition on the physico-chemical properties of the hydrogels is addressed, together with its effect on the functional electroactive and magnetoactive response. NPs concentration up to 10 % do not affect the mechanical stability of the gels, while promoting an increase actuation response., Competing Interests: Declaration of competing interest None., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

In the current study describes the synthesis, characterization, and photocatalytic activity (PCA) of ZnO nanoparticles (NPs) synthesized via the polymeric precursor technique in the first step, following annealing ranging from 500 to 900 °C in a second step. X-ray diffraction data analysis confirms the formation of the wurtzite crystal structure in the as-prepared and thermally annealed samples. To adjust the crystallite mean size and physical properties, thermal annealing procedures in atmospheric air are used. The UV–Vis spectroscopy studies show that the optical band gap of the as-fabricated ZnO NPs decreases monotonically, from ~ 3.4 eV to ~ 3.1 eV, as the annealing temperature increases. The PCA of the ZnO NPs against methylene blue dye tests revealed an increase in efficiency as the annealing temperature increases from 500 °C, reaching a maximum performance for the sample annealed at 700 °C. Above that annealing temperature, the efficiency tends to slightly decrease. Our findings suggest that the PCA tests of the ZnO NPs do not show a straightforward dependence on the NPs' size, but it seems to be correlated with the density of defects, such as oxygen vacancies, which are modulated by the annealing temperature. In addition, thermoluminescence (TL) glow curves exhibit a well-defined peak located at ~ 622 K for the as-prepared ZnO NPs. The TL peak intensity shows a decreasing trend with the annealing temperature up to ~ 700 °C. This result was correlated with the modulation of charge traps as the annealing temperature is increased. It means, the TL peak intensity is directly related to the amount of trapped charges (electrons and holes); therefore, a more intense TL peak suggests less photogenerated charge available for the catalytic activity, leading to a marked reduction of the PCA. [ABSTRACT FROM AUTHOR]

Dysprosium (Dy3+)-doped tin oxide (SnO2) nanoparticles (NPs) have been successfully synthesized using the chemical polymer precursor method. This material blends the holding matrix’s electronic properties with dysprosium’s optical and magnetic properties, making it a promising material for technological applications. X-ray diffraction patterns and the Raman spectra of all NPs indicated the formation of only the SnO2 phase. The decrease in particle size (from ~ 11 to ~ 6 nm) and increase in lattice parameters depending on the Dy content were determined. The latter proves the solid solution between Sn and Dy ions, which is in agreement with the ionic radii mismatch between them. Transmission electron microscopy (TEM) confirms the particle size and size reduction observed through XRD. X-ray photoelectron spectroscopy (XPS) results suggest a change of the oxidation state from Sn4+ to Sn2+with the Dy content, with more Dy3+ than the values accessed from EDS analysis. The latter strongly suggests that the Dy3+ surface gets enriched as the dopant amount increases, driving to the surface passivation of structural defects in good agreement with Raman spectroscopy results. Optical properties show a modest bandgap reduction with the Dy content. Meanwhile, magnetic measurements indicate the coexistence of ferromagnetic and paramagnetic contributions for 1% Dy-doped SnO2 NPs. However, only the paramagnetic contribution is observed after this concentration level. The ferromagnetic contribution detected for lower dopant amounts (≤ 1%) has been attributed to the presence of bound magnetic polarons (BMP’s). [ABSTRACT FROM AUTHOR]

A simple single-phase material, a random close-packed (volume fraction 67%) ensemble of highly monodisperse bare maghemite (γ-Fe2O3) nanoparticles, is shown to exhibit ideal superspin-glass behavior (mimicking that of model spin-glasses), namely, an unprecedentedly sharp onset of the absorption component of the ac susceptibility, narrow memory dips in the zero-field-cooled magnetization and a spin-glass characteristic field-dependence of the magnetic susceptibility. This ideal behavior is attributed to the remarkably narrow dispersion in particle size and to the highly dense and spatially homogeneous configuration ensured by the random close-packed arrangement. This material is argued to constitute the closest nanoparticle analogue to a conventional (atomic) magnetic state found to date. [ABSTRACT FROM AUTHOR]