Search Results (5)

Effective osteogenesis for bone regeneration is still considerably challenging for a porous β-tricalcium phosphate (β-TCP) scaffold to achieve. To overcome this challenge, hollow manganese dioxide (H-MnO₂) nanoparticles with an urchin-like shell structure were prepared and added in the porous β-TCP scaffold. A template-casting method was used to prepare the porous H-MnO₂/β-TCP scaffolds. As a control, solid manganese dioxide (S-MnO₂) nanoparticles were also added into β-TCP scaffolds. Human bone mesenchymal stem cells (hBMSC) were seeded in the porous scaffolds and characterized through cell viability assay and alkaline phosphatase (ALP) assay. Results from in vitro protein loading and releasing experiments showed that H-MnO₂ can load significantly higher proteins and release more proteins compared to S-MnO₂ nanoparticles. When they were doped into β-TCP, MnO₂ nanoparticles did not significantly change the surface wettability and mechanical properties of porous β-TCP scaffolds. In vitro cell viability results showed that MnO₂ nanoparticles promoted cell proliferation in a low dose, but inhibited cell growth when the added concentration went beyond 0.5%. At a range of lower than 0.5%, H-MnO₂ doped β-TCP scaffolds promoted the early osteogenesis of hBMSCs. These results suggested that H-MnO₂ in the porous β-TCP scaffold has promising potential to stimulate osteogenesis. More studies would be performed to demonstrate the other functions of urchin-like H-MnO₂ nanoparticles in the porous β-TCP. Full article

Based on MnO₂/carbon cloth (CC) composite materials, an Ag-doped MnO₂ nanowire, self-assembled, urchin-like structure was synthesized in situ on the surface of CC using a simple method, and a novel and efficient flexible electrode material for supercapacitors was developed. The morphology, structure, elemental distribution, and pore distribution of the material were analyzed using SEM, TEM, XRD, XPS, and BET. The electrochemical performance was tested using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). In the three-electrode system, GCD testing showed that the specific capacitance of the material reached 520.8 F/g at 0.5 A/g. After 2000 cycles at a current density of 1 A/g, the capacitance retention rate was 90.6%, demonstrating its enormous potential in the application of supercapacitor electrode materials. Full article

Rechargeable aqueous Zn/MnO₂ batteries are very potential for large-scale energy storage applications owing to their low cost, inherent safety, and high theoretical capacity. However, the MnO₂ cathode delivers unsatisfactory cycling performance owing to its low intrinsic electronic conductivity and dissolution issue. Herein, we design and synthesize a Ag-doped sea-urchin-like MnO₂ material for rechargeable zinc-ion batteries (ZIBs). Doping Ag was found to reduce charge transfer resistance, increase the redox activity, and improve the cycling stability of MnO₂. The unique sea-urchin-like structure maintains rich active sites for charge storage. As a result, the Ag-doped MnO₂-based ZIB presents a high reversible specific capacity to 315 mA h g⁻¹ at 50 mA g⁻¹, excellent rate performance, and a capacity retention of 94.4% when cycling over 500 cycles. An ex situ TEM test demonstrates the low-dissolution property of Ag-doped MnO₂. A flexible quasi-solid-state ZIB is successfully assembled using Ag-doped MnO₂ on graphite paper, which shows a stable specific capacity of 171 mA h g⁻¹ at 1 A g⁻¹ when cycled over 600 cycles. Our investigation demonstrates the significant role played by Ag doping in enhancing the ZIB performance of MnO₂, and gives some insight into developing advanced active materials by heteroatom doping. Full article

Three-dimensional (3D) urchin-like MnO₂@poly (sodium 4-styrene sulfonate) (PSS)/poly (diallyl dimethylammonium chloride) (PDDA)/PSS particles were prepared via the layer-by-layer (LBL) assembly of polyelectrolytes for the extraction of Zn²⁺ from alkaline media. The adsorption performance of Zn²⁺ on MnO₂, MnO₂@PSS/PDDA/PSS, and MnO₂@(PSS/PDDA)₃/PSS was investigated in batch experiments. The adsorption of Zn²⁺ on MnO₂@PSS/PDDA/PSS has been studied under various conditions, such as initial Zn²⁺ concentration, adsorbent dosage, the solution’s pH, and reaction time. The Zn²⁺ adsorption process is well represented by the pseudo-second-order kinetic model, and the equilibrium data fit the Freundlich isotherm well. MnO₂@PSS/PDDA/PSS also showed high efficiency for Pb²⁺ and Cu²⁺ removal from slightly alkaline water. Thus, our research provides a deep insight into the preparation of 3D manganese oxides with polyelectrolyte films for the extraction of heavy metal ions, such as Pb²⁺, Cu²⁺, and Zn²⁺, from slightly alkaline wastewater. Full article

Si is a promising material for applications as a high-capacity anode material of lithium-ion batteries. However, volume expansion, poor electrical conductivity, and a short cycle life during the charging/discharging process limit the commercial use. In this paper, new ternary composites of sea urchin-like Si@MnO₂@reduced graphene oxide (rGO) prepared by a simple, low-cost chemical method are presented. These can effectively reduce the volume change of Si, extend the cycle life, and increase the lithium-ion battery capacity due to the dual protection of MnO₂ and rGO. The sea urchin-like Si@MnO₂@rGO anode shows a discharge specific capacity of 1282.72 mAh g⁻¹ under a test current of 1 A g⁻¹ after 1000 cycles and excellent chemical performance at different current densities. Moreover, the volume expansion of sea urchin-like Si@MnO₂@rGO anode material is ~50% after 150 cycles, which is much less than the volume expansion of Si (300%). This anode material is economical and environmentally friendly and this work made efforts to develop efficient methods to store clean energy and achieve carbon neutrality. Full article