Coating a polymeric membrane for gas separation is a feasible approach to fabricate gas sensors with selectivity. In this study, poly(methyl methacrylate)-(PMMA-)membrane-coated palladium (Pd) nanoparticle (NP) films were fabricated for high-performance hydrogen (H) gas sensing by carrying out gas-phase cluster deposition and PMMA spin coating. No changes were induced by the PMMA spin coating in the electrical transport and H-sensing mechanisms of the Pd NP films. Measurements of H sensing demonstrated that the devices were capable of detecting H gas within the concentration range 0-10% at room temperature and showed high selectivity to H due to the filtration effect of the PMMA membrane layer. Despite the presence of the PMMA matrix, the lower detection limit of the sensor is less than 50 ppm. A series of PMMA membrane layers with different thicknesses were spin coated onto the surface of Pd NP films for the selective filtration of H. It was found that the device sensing kinetics were strongly affected by the thickness of the PMMA layer, with the devices with thicker PMMA membrane layers showing a slower response to H gas. Three mechanisms slowing down the sensing kinetics of the devices were demonstrated to be present: diffusion of H gas in the PMMA matrix, nucleation and growth of the β phase in the α phase matrix of Pd hydride, and stress relaxation at the interface between Pd NPs and the PMMA matrix. The retardation effect caused by these three mechanisms on the sensing kinetics relied on the phase region of Pd hydride during the sensing reaction. Two simple strategies, minimizing the thickness of the PMMA membrane layer and reducing the size of the Pd NPs, were proposed to compensate for retardation of the sensing response.
Layered perovskites A 3 M 2 O 7 are known to exhibit the so-called hybrid improper ferroelectricity. Despite experimentally confirmed cases (e.g. nonmagnetic M =Ti and Sn), the ferroelectricity in magnetic Ca 3 Mn 2 O 7 remains a puzzle. Here, the structural, ferroelectric, magnetoelectric, and optical properties of Ca 3 Mn 2 O 7 are systematically investigated. Switchable polarization is directly measured, demonstrating its ferroelectricity. In addition, magnetoelectric response is also evidenced, implying the coupling between magnetism and ferroelectricity. Furthermore, strong visible light absorption is observed, which can be understood from its electronic structure. Its direct and appropriate band gap, as well as wide conducting bands, makes Ca 3 Mn 2 O 7 a potential candidate for ferroelectric photoelectric applications.
The superhydrophobic coating was obtained from PTFE, DOTL, PDMS and TEOS on aluminum substrate. a–d present SEM images of coatings without PTFE, with 0.6 g, 1.0 g and 0.6 g PTFE after 34 times icing/deicing experiments, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.