Fabrication and Characterization of Nanocomposite Hydrogel Based on Alginate/Nano-Hydroxyapatite Loaded with Linum usitatissimum Extract as a Bone Tissue Engineering Scaffold

In the current paper, we fabricated, characterized, and applied nanocomposite hydrogel based on alginate (Alg) and nano-hydroxyapatite (nHA) loaded with phenolic purified extracts from the aerial part of Linum usitatissimum (LOH) as the bone tissue engineering scaffold. nHA was synthesized based on the wet chemical technique/precipitation reaction and incorporated into Alg hydrogel as the filler via physical cross-linking. The characterizations (SEM, DLS, and Zeta potential) revealed that the synthesized nHA possess a plate-like shape with nanometric dimensions. The fabricated nanocomposite has a porous architecture with interconnected pores. The average pore size was in the range of 100–200 µm and the porosity range of 80–90%. The LOH release measurement showed that about 90% of the loaded drug was released within 12 h followed by a sustained release over 48 h. The in vitro assessments showed that the nanocomposite possesses significant antioxidant activity promoting bone regeneration. The hemolysis induction measurement showed that the nanocomposites were hemocompatible with negligible hemolysis induction. The cell viability/proliferation confirmed the biocompatibility of the nanocomposites, which induced proliferative effects in a dose-dependent manner. This study revealed the fabricated nanocomposites are bioactive and osteoactive applicable for bone tissue engineering applications.

Design of Hierarchical NiCo2O4 Nanocages with Excellent Electrocatalytic Dynamic for Enhanced Methanol Oxidation

Although sheet-like materials have good electrochemical properties, they still suffer from agglomeration problems during the electrocatalytic process. Integrating two-dimensional building blocks into a hollow cage-like structure is considered as an effective way to prevent agglomeration. In this work, the hierarchical NiCo2O4 nanocages were successfully synthesized via coordinated etching and precipitation method combined with a post-annealing process. The nanocages are constructed through the interaction of two-dimensional NiCo2O4 nanosheets, forming a three-dimensional hollow hierarchical architecture. The three-dimensional supporting cavity effectively prevents the aggregation of NiCo2O4 nanosheets and the hollow porous feature provides amounts of channels for mass transport and electron transfer. As an electrocatalytic electrode for methanol, the NiCo2O4 nanocages-modified glassy carbon electrode exhibits a lower overpotential of 0.29 V than those of NiO nanocages (0.38 V) and Co3O4 nanocages (0.34 V) modified glassy carbon electrodes. The low overpotential is attributed to the prominent electrocatalytic dynamic issued from the three-dimensional hollow porous architecture and two-dimensional hierarchical feature of NiCo2O4 building blocks. Furthermore, the hollow porous structure provides sufficient interspace for accommodation of structural strain and volume change, leading to improved cycling stability. The NiCo2O4 nanocages-modified glassy carbon electrode still maintains 80% of its original value after 1000 consecutive cycles. The results demonstrate that the NiCo2O4 nanocages could have potential applications in the field of direct methanol fuel cells due to the synergy between two-dimensional hierarchical feature and three-dimensional hollow structure.

Construction of Hierarchical Porous Architecture on Ni Foam for Efficient Oxygen Evolution Reaction Electrode

Nickel foam (NF) with a three-dimensional porous structure plays an important role in a wide variety of applications such as energy storage and conversion, catalysis, and sensor due to its high porosity, low density, and excellent conductivity. However, the main drawback of NF is that its ligaments are very smooth, and thus the surface area is relatively low. In this work, we propose a novel strategy, oxidization and reduction process, in situ to construct micron/nano pores on the ligaments of commercial NF to fabricate a typical hierarchical porous architecture. This process is simple and green, avoiding the use of sacrificial materials. Furthermore, MnO2 is coated on the micron/nano-porous Ni foam (MPNF) to construct an oxygen evolution reaction (OER) electrode through pulse electrodeposition. The designed MPNF-MnO2 electrode presents enhanced OER electrocatalysis activity with a low overpotential of 363.5 mV at the current density of 10 mA cm−2 in an alkaline solution, which is 66.4 mV lower than that of the NF-MnO2 electrode in the same operating conditions. Furthermore, the porous and wrinkled structures of the MPNF also improve the mechanical integrity of the electrode, resulting in super-long stability.

Ti3C2Tx MXene-Based Three-Dimensional Architecture for Carbon Dioxide Capture

Dramatic increases in fossil fuel consumption inevitably led to the emission of huge amounts of CO2 gas, causing abnormalities in the climate system. Despite continuous efforts to resolve global atmospheric problems through CO2 capture and separation, success has been limited by poor CO2 selectivity in the CO2/N2 mixture. Herein, we demonstrate the fabrication of a three-dimensional (3D) nanostructure from two-dimensional transition metal carbides (Ti3C2Tx, MXene), and assess its utility as an adsorbent in a CO2 capture system. Through structural and textural analysis, we confirm that the as-prepared MXene possesses high size uniformity with a thickness of ~2.5 nm, and that an MXene aerogel interconnected by MXene nanosheets has a 3D porous architecture with micro/nano porosity (Barrett-Joyner-Halenda (BJH) pore size = 11.4 nm). Moreover, the MXene aerogel exhibits favorable adsorption behavior for CO2, due to the high-quality MXene nanosheets even with a low specific surface area. Our approach could lead to significant advances in CO2 capture by adsorbents and open up new opportunities for mass production.