Ferromagnetism was observed at room temperature in monodisperse CeO2 nanospheres synthesized by hydrothermal treatment of Ce(NO3)3·6H2O using polyvinylpyrrolidone as a surfactant. The structure and morphology of the products were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and field-emission scanning electron microscopy (FE-SEM). The optical properties of the nanospheres were determined using UV and visible spectroscopy and photoluminescence (PL). The valence states of Ce ions were also determined using X-ray absorption near edge spectroscopy. The XRD results indicated that the synthesized samples had a cubic structure with a crystallite size in the range of approximately 9 to 19 nm. FE-SEM micrographs showed that the samples had a spherical morphology with a particle size in the range of approximately 100 to 250 nm. The samples also showed a strong UV absorption and room temperature PL. The emission might be due to charge transfer transitions from the 4f band to the valence band of the oxide. The magnetic properties of the samples were studied using a vibrating sample magnetometer. The samples exhibited room temperature ferromagnetism with a small magnetization of approximately 0.0026 to 0.016 emu/g at 10 kOe. Our results indicate that oxygen vacancies could be involved in the ferromagnetic exchange, and the possible mechanism of formation was discussed based on the experimental results.

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The thermoelectric properties of the Ca 3 Co 4 O 9?d and the transition metals-doped Ca 3 Co 3.8 M 0.2 O 9?d (where M = Cr, Fe, Ni, Cu and Zn) ceramics were reported. Ca 3 Co 4 O 9?d single phase was checked by using X-ray diffraction analysis performed for the Ca 3 Co 3.8-M 0.2 O 9?d samples. The scanning electron micrographs showed some degrees of grains alignment in the compacted direction. The resistivity of the samples measured from 100 up to 700°C varies in magnitude for different transition metals substitution. The variation of resistivity was explained by a change of carrier concentration induced by the doped ions. The thermopower increased with increasing temperature but showed no obvious change for any transition metals doping. The thermal conductivities changed for the doped samples but were relatively independent of temperature. The ZT was calculated to be the highest for the Fe substitution for the whole measurement temperature with the maximum value of 0.12 at 700°C.

This review paper provides a recent overview of current international research that is being conducted into the functional properties of cellulose as a nanomaterial. A particular emphasis is placed on fundamental and applied research that is being undertaken to generate applications, which are now becoming a real prospect given the developments in the field over the last 20 years. A short introduction covers the context of the work, and definitions of the different forms of cellulose nanomaterials (CNMs) that are most widely studied. We also address the terminology used for CNMs, suggesting a standard way to classify these materials. The reviews are separated out into theme areas, namely healthcare, water purification, biocomposites, and energy. Each section contains a short review of the field within the theme and summarizes recent work being undertaken by the groups represented. Topics that are covered include cellulose nanocrystals for directed growth of tissues, bacterial cellulose in healthcare, nanocellulose for drug delivery, nanocellulose for water purification, nanocellulose for thermoplastic composites, nanocellulose for structurally colored materials, transparent wood biocomposites, supercapacitors and batteries.

Bio-triboelectric nanogenerators (bio-TENGs) have received a lot of attention for the applications in self-powered implantable or wearable electronics. Several types of cellulose-based bio-TENGs exhibited outstanding output performance, in particular, bacterial cellulose (BC) based bio-TENGs. However, the cellulose needs to go through several processes involving solubilization and regeneration to form the film. These processes destroy the nanostructure and crystallinity, and thus, the maximum output voltage and current may not be utilized. In this work, the bio-TENGs based on BC nanocomposites were simply fabricated by a gradually drying BC hydrogel on a conductive substrate. The BC film was adhesively bonded on the indium tin oxide (ITO) substrate directly without the use of any conductive paste. Furthermore, ZnO nanoparticles were impregnated into the BC nanostructure, particularly at the film surface, to increase the surface roughness and polarizability. The BC/ZnO (ZBC) nanocomposite could not directly bond to the substrate so that it was modified by amino-silane treatment before drying on the substrate. The triboelectric measurements showed that the bio-TENGs based on the BC and ZBC films generated relatively high open-circuit voltage (V oc ) and short-circuit current (I sc ), compared to the BC-TENGs fabricated via other routes. The results emphasize the significance of our preparation method that preserves the nanostructure of the BC and the direct attachment of the films on the substrate without using adhesive tapes. Our bio-TENGs exhibit the maximum V oc and I sc of 57.6 V and 5.78 μA, and the maximum power density of 42 mW/m 2 when matched with an external load. The results from the triboelectric measurements were supported by several characterization techniques to confirm the phase formation, morphology, functional group, thermal stability, and hydrophobicity/hydrophilicity.

In this paper, the potential use of either amine-functionalized or hydroxyl-functionalized magnesium ferrite (MgFe2O4) nanoparticles (NPs) as Congo red nanoad­sorbents is explored and compared. The amine-functionalized MgFe2O4 NPs (denoted as MgFe2O4–NH2 NPs) were synthesized by a one-pot coprecipitation method using ethanolamine as a surface modifier, while the hydroxyl-functionalized MgFe2O4 NPs (denoted as MgFe2O4–OH NPs) were prepared by a hydrothermal method. In general, both nanoadsorbents can be successfully produced without calcination and were found to possess superparamagnetic properties with high saturation magnetization (M s). In particular, MgFe2O4–OH NPs exhibit a higher M s value of ∼53 emu g–1, promoting the rapid separation ability of the NPs from the treated solution using an external permanent magnet. The Congo red removal performance of these nanoadsorbents was investigated as a function of the pH of the aqueous solution and contact time. The removal efficiency of Congo red by MgFe2O4–NH2 NPs was found to be ∼96% within 180 min at pH 6, while MgFe2O4–OH NPs provided a removal efficiency at ∼88% within 420 min at pH 8. In addition, the maximum adsorption capacities (q m) calculated using the Langmuir isotherm equation were found to be 71.4 and 67.6 mg g–1 for MgFe2O4–NH2 and MgFe2O4–OH NPs, respectively. The higher q m value of MgFe2O4–NH2 NPs could be attributed to stronger electrostatic interactions with the sulfonate groups of Congo red formed by larger numbers of protonated amine groups than protonated hydroxyl groups of the adsorbents under the performed conditions. Moreover, reusability experiments also revealed that MgFe2O4–NH2 NPs offered a higher removal efficiency than MgFe2O4–OH NPs for the same cycles tested. Therefore, this study demonstrates that MgFe2O4–NH2 NPs synthesized by a simple one-pot synthetic method are applicable as reusable magnetic nanoadsorbents for Congo red removal in current practice.

We present a simple strategy to achieve excellent dielectric and nonlinear current–voltage properties for pure–CaCu3Ti4O12 ceramics prepared by a modified sol–gel method with different calcining conditions. At 1 kHz and room temperature, the best CCTO ceramic can exhibit a high dielectric constant (ε′) of 9516 with a very low dielectric loss, tan δ ~0.020. The minimum value of tan δ is 0.018 at 2.5 kHz with ε′ ~9433. High breakdown field of 4032 V/cm and nonlinear coefficient of 7.05 were obtained.

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