Recent Developments and Future Perspectives of Molybdenum Borides and MBenes.

Metal borides have received a lot of attention recently as a potentially useful material for a wide range of applications. In particular, molybdenum-based borides and MBenes are of great significance, due to their remarkable properties like good electronic conductivity, considerable stability, high surface area, and environmental harmlessness. Therefore, in this article, the progress made in molybdenum-based borides and MBenes in recent years is reviewed. The first step in understanding these materials is to begin with an overview of their structural and electronic properties. Then synthetic technologies for the production of molybdenum borides, such as high-temperature/pressure methods, physical vapor deposition (PVD), chemical vapor deposition (CVD), element reaction route, molten salt-assisted, and selective etching methods are surveyed. Then, the critical performance of these materials in numerous applications like energy storage, catalysis, biosensors, biomedical devices, surface-enhanced Raman spectroscopy (SERS), and tribology and lubrication are summarized. The review concludes with an analysis of the current progress of these materials and provides perspectives for future research. Overall, this review will offer an insightful reference for the understanding molybdenum-based borides and their development in the future.

Spinel NiFe2O4 nanoparticles decorated 2D Ti3C2 MXene sheets for efficient water splitting: Experiments and theories.

Design and demonstration of cost-effective, robust, and earth-abundant electrocatalysts for efficient water splitting have attracted a great deal of interest. Herein, we have decorated NiFe2O4 nanoparticles on the emerging novel two-dimensional (2D) Ti3C2 (MXene) sheets in order to achieve better electrocatalytic performance for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The synthesized NiFe2O4/Ti3C2 composite showed extraordinary kinetic metrics for electrocatalytic OER, revealing a low overpotential of 266 mV at a current density of 10 mA/cm2, and a small Tafel slope of 73.6 mV/dec. For HER, the composite exhibited an overpotential of 173 mV at 10 mA/cm2 with a small Tafel slope of 112.2 mV/dec. The high electrocatalytic performance of NiFe2O4/Ti3C2 composite is believed to be originated from a well-constructed nanoparticle-sheet interface, synergistic effect, and the high metallic conductivity of Ti3C2 MXene sheets. These experimental results are further supported by the state-of-the-art density functional theory (DFT) simulations. The study providing information about the structure, electronic properties, bonding, and interaction mechanism between Ti3C2 (MXene) and NiFe2O4. Moreover, offering the values of the theoretical overpotential of Ti3C2 (MXene), NiFe2O4, and the NiFe2O4/Ti3C2 composite for both OER and HER activities. Interestingly, the theoretical overpotential follows the qualitative trend of NiFe2O4/Ti3C2 < NiFe2O4 < Ti3C2 MXene for OER and NiFe2O4/Ti3C2 < Ti3C2 MXene < NiFe2O4 for HER, agreeing with the experimental observations. There is charge transfer from NiFe2O4 to MXene leading to enhancement in electronic states near Fermi level which may be due to interactions between C 2p orbital of Ti3C2 MXene and 3d orbital of Ni and Fe. Therefore, this work provides new insights for designing new efficient non-noble metal-based electrocatalysts in the future.

Magnetic gas sensing: working principles and recent developments.

Gas sensors work on the principle of transforming the gas adsorption effects on the surface of the active material into a detectable signal in terms of its changed electrical, optical, thermal, mechanical, magnetic (magnetization and spin), and piezoelectric properties. In magnetic gas sensors, the change in the magnetic properties of the active materials is measured by one of the approaches such as Hall effect, magnetization, spin orientation, ferromagnetic resonance, magneto-optical Kerr effect, and magneto-static wave oscillation effect. The disadvantages of different types of gas sensors include their chemical selectivity and sensitivity to humidity and high-temperature operation. For example, in the case of chemiresistive-type gas sensors, the change in the sensor resistance can drastically vary in the real environment due to the presence of other gas species and the overall electrical effect is quite complex due to simultaneous surface reactions. Further, it is not easy to make stable contacts for powdered samples for the conventional electrical property-based gas sensors. Fire hazard is another issue for the electrical property-based hydrogen gas sensors due to their flammable nature at higher operating temperature. In this regard, to solve these issues, magnetic gas sensor concepts have emerged, in which the magnetic properties of the materials get modified when exposed to gas molecules. In this review article, the working principles, fundamentals, recent developments, and future perspectives in magnetic gas sensors are reviewed. Finally, the prospects and opportunities in these exciting fields are also commented upon based on their current progress.

TiO2 nanoflowers based humidity sensor and cytotoxic activity.

We have systematically investigated the humidity sensing performance and cytotoxic activity of TiO2 nanoflowers synthesized by hydrothermal method. Our result reveals that TiO2 nanoflower based sensor devices show good performance at room temperature with a maximum sensitivity of ∼815% along with a response time of ∼143 s and a recovery time of ∼33 s. Our findings also evaluate the cytotoxic effect of TiO2 nanoflowers on human HepG2 cell lines. The cells are cultured in DMEM medium with varying concentrations of TiO2 nanoflowers for 24, 48 and 72 hours respectively. The results indicate that TiO2 nanoflower doses time dependently suppress the proliferation of HepG2 cell lines.