In this contribution, we present an experimental and numerical study on the coating of Al plasmonic nanostructures through a conformal layer of high-refractive-index molybdenum oxide. The investigated structures are closely coupled nanodisks where we observe that the effect of the thin coating is to help gap narrowing down to the sub-5-nm range, where a large electromagnetic field enhancement and confinement can be achieved. The solution represents an alternative to more complex and challenging lithographic approaches, and results are also advantageous for enhancing the long-term stability of aluminum nanostructures.

Hydrogen has the potential to become a crucial energy storage vector, allowing to maximise the advantages of renewable and sustainable energy sources. Hydrogen is usually stored as compressed hydrogen gas, or liquid hydrogen. However, the former requires high pressure, the latter cryogenic temperatures, being a huge limit to the widespread adoption of these storage methods. Thus, new materials for solid-state hydrogen storage shall be developed. Here we show that a α−MoO3 thin film, grown via atomic layer deposition, is a promising material for reversibly storing hydrogen. We found that hydrogen plasma is a convenient way to hydrogenise − at room temperature and relatively low pressures (500 or 1000 mTorr) − layered monocrystalline α−MoO3 thin films. Hydrogen has been shown to locate itself in the van der Waals gap along the [010] oriented α−MoO3 film. The process has been found to be totally reversible in air. Our essay could be a starting point to a transition from conventional (gas and liquid) to more advantageous solid-state hydrogen storage materials.