Optical Gas Sensing Properties of Nanoporous Nb₂O₅ Films

Nanoporous Nb₂O₅ has been previously demonstrated to be a viable electrochromic material with strong intercalation characteristics. Despite showing such promising properties, its potential for optical gas sensing applications, which involves the production of ionic species such as H⁺, has yet to be explored. Nanoporous Nb₂O₅ can accommodate a large amount of H⁺ ions in a process that results in an energy bandgap change of the material which induces an optical response. Here, we demonstrate the optical hydrogen gas (H₂) sensing capability of nanoporous anodic Nb₂O₅ with a large surface-to-volume ratio prepared via a high temperature anodization method. The large active surface area of the film provides enhanced pathways for efficient hydrogen adsorption and dissociation, which are facilitated by a thin layer of Pt catalyst. We show that the process of H₂ sensing causes optical modulations that are investigated in terms of response magnitudes and dynamics. The optical modulations induced by the intercalation process and sensing properties of nanoporous anodic Nb₂O₅ shown in this work can potentially be used for future optical gas sensing systems

Plasmon Resonances of Highly Doped Two-Dimensional MoS₂

The exhibition of plasmon resonances in two-dimensional (2D) semiconductor compounds is desirable for many applications. Here, by electrochemically intercalating lithium into 2D molybdenum disulfide (MoS₂) nanoflakes, plasmon resonances in the visible and near UV wavelength ranges are achieved. These plasmon resonances are controlled by the high doping level of the nanoflakes after the intercalation, producing two distinct resonance peak areas based on the crystal arrangements. The system is also benchmarked for biosensing using bovine serum albumin. This work provides a foundation for developing future 2D MoS₂ based biological and optical units

Enhanced gas permeation through graphene nanocomposites

The use of membranes for gas permeation and phase separation offers many distinct advantages over other more energy-dependent processes. The operational efficiencies of these membranes rely heavily on high gas permeability. Here, we report membranes with significantly increased permeability without a considerable decrease in mechanical strength or selectivity, synthesized from a polymer nanocomposite that incorporates graphene and polydimethylsiloxane (PDMS). These graphene–PDMS nanocomposite membranes were able to enhance the gas permeation of N₂, CO₂, Ar, and CH₄ in reference to pristine PDMS membranes. This is achieved by creating interfacial voids between the graphene flakes and polymer chains, which increases the fractional free volume within the nanocomposites, giving rise to an increase in permeation. An optimal loading of graphene was found to be 0.25 wt%, while greater loading created agglomeration of the graphene flakes, hence reducing the effective surface area. We present the enhancements that the membranes can provide to sensing and phase separation applications. We show that these nanocomposites are near transparent to CO₂ gas molecules in sensing measurements. This study offers a new area of research for graphene-based nanocomposites