Influence of SiO2 on the structure-controlled synthesis and magnetic properties of prismatic MnO2 nanorods

Facile Hydrothermal Synthesis of Binder-Free Hexagonal MnO2 Nanoparticles for a High-Performance Supercapacitor’s Electrode Material

Manganese dioxide (MnO2)-based nanostructures are promising electrode materials for supercapacitors (SCs) due to their low cost, eco-friendly nature, and high theoretical capacitance. However, the conductivity of MnO2 is poor, which is a big problem when trying to achieve the desired capacitance value. Herein, hexagonal-phase MnO2 nanoparticles (NPs) are directly grown on a 3D conductive carbon cloth (CC) (denoted as MnO2-NPs@CC) as a binder-free electrode through a simple and scalable hydrothermal strategy. The results show that MnO2-NPs@CC with a large specific surface area and high porosity could be employed as a positive electrode material for high-performance SCs. Owing to these attractive properties, the MnO2-NPs@CC electrode delivers a high specific capacitance of 660 F/g at a current density of 2 A/g in 6 M KOH aqueous electrolytes. Moreover, the MnO2-NPs@CC electrode demonstrates excellent cycling stability with high capacitance retention of 92.8% over 10,000 cycles. Such remarkable findings suggest that MnO2-NPs@CC with enhanced electrochemical performance is a favorable electrode material for next-generation high-performance SCs.

Osteogenic potential of sol-gel bioactive glasses containing manganese

Bioactive glasses (BGs) are widely used for bone regeneration, and allow the incorporation of different ions with therapeutic properties into the glass network. Amongst the different ions with therapeutic benefits, manganese (Mn) has been shown to influence bone metabolism and activate human osteoblasts integrins, improving cell adhesion, proliferation and spreading. Mn has also been incorporated into bioceramics as a therapeutic ion for improved osteogenesis. Here, up to 4.4 mol% MnO was substituted for CaO in the 58S composition (60 mol% SiO₂, 36 mol% CaO, 4 mol% P₂O₅) and its effects on the glass properties and capability to influence the osteogenic differentiation were evaluated. Mn-containing BGs with amorphous structure, high specific surface area and nanoporosity were obtained. The presence of Mn²⁺ species was confirmed by X-ray photoelectron spectroscopy (XPS). Mn-containing BGs presented no cytotoxic effect on human mesenchymal stem cells (hMSCs) and enabled sustained ion release in culture medium. hMSCs osteogenic differentiation stimulation and influence on the mineralisation process was also confirmed through the alkaline phosphatase (ALP) activity, and expression of osteogenic differentiation markers, such as collagen type I, osteopontin and osteocalcin, which presented higher expression in the presence of Mn-containing samples compared to control. Results show that the release of manganese ions from bioactive glass provoked human mesenchymal stem cell (hMSC) differentiation down a bone pathway, whereas hMSCs exposed to the Mn-free glass did not differentiate. Mn incorporation offers great promise for obtaining glasses with superior properties for bone tissue regeneration.

High Zr doping effects on the microstructural and optical properties of Mn3 O4 thin films along with ethanol sensing

Transition metal oxides as transparent conducting oxides (TCOs) films, with high optical transparency (≥82%), various valence states and p-type conductivity are used in a several physical domains. This work covers the physical study of Zr doped Mn₃O₄ semiconductor thin films using a spray pyrolysis method where Zr content varies in starting solutions from 0 to 20at.%. The impact of this work is to offer some understanding of microscopic effects of relatively high doping Zr and then correlate these effects with the macroscopic properties for interesting applications especially gas sensor. In fact, the addition of Zr ions pointed out the reduction of crystallite size (24.1 (nm)) with 20at.% doping allowing a better adsorption of gas molecules. In addition, it promotes the increase of optical gap (2.92eV) with 6at.% doping which is a useful parameter for some optical devices. X-ray diffraction (XRD), Raman spectroscopy, FTIR spectroscopy, atomic force microscopy (AFM) and EDAX techniques were used. It is found that these films crystallized in spinel type tetragonal hausmmanite structure. The gas sensing activity of these thin films (0, 6, 12 and 20at.% Zr) was examined with Ethanol. The performances of these last four sensing layers were compared. All the tests were performed at different working temperatures T_work=125, 150, 175 and 225°C and under two gas concentrations: 0.1% and 0.5% ethanol using dry air as carrier gas. The films exhibited noticeably ethanol sensing especially the sample doped with 6% of zirconium exhibits the most excellent sensing performance since it showed a clear response already at a low ethanol concentration of 0.1%.