Highly sensitive SnO2 sensor via reactive laser-induced transfer.

Gas sensors based on tin oxide (SnO2) and palladium doped SnO2 (Pd:SnO2) active materials are fabricated by a laser printing method, i.e. reactive laser-induced forward transfer (rLIFT). Thin films from tin based metal-complex precursors are prepared by spin coating and then laser transferred with high resolution onto sensor structures. The devices fabricated by rLIFT exhibit low ppm sensitivity towards ethanol and methane as well as good stability with respect to air, moisture, and time. Promising results are obtained by applying rLIFT to transfer metal-complex precursors onto uncoated commercial gas sensors. We could show that rLIFT onto commercial sensors is possible if the sensor structures are reinforced prior to printing. The rLIFT fabricated sensors show up to 4 times higher sensitivities then the commercial sensors (with inkjet printed SnO2). In addition, the selectivity towards CH4 of the Pd:SnO2 sensors is significantly enhanced compared to the pure SnO2 sensors. Our results indicate that the reactive laser transfer technique applied here represents an important technical step for the realization of improved gas detection systems with wide-ranging applications in environmental and health monitoring control.

Probing the selectivity of a nanostructured surface by xenon adsorption.

Surface-supported molecular self-assembly with the goal to produce highly ordered, functional supramolecular nanostructures are often realized using nanopatterned surfaces, which exhibit long range - ideally periodic - modulations of the molecule adsorption properties. To elucidate the physical origins of the site-specific adsorption properties of such a nanopatterned substrate, we investigated the temperature-dependent microscopic structure and the dynamics of adsorbed Xe at different temperatures on single-sheet h-BN on a Rh(111) nanomesh. In combination with molecular dynamics simulations we show that the site-specific adsorption arises from two different interactions of similar magnitude with respect to their lateral variations. The first can be attributed to a van der Waals type interaction, whereas the second originates from lateral variation of the electrostatic surface potential and is of polarization type. Both types lead to an adsorption energy minimum at the rim of the nanomesh pore and are therefore responsible for stabilizing dynamic and static Xe rings in these pores. The insight into this interplay of interactions should pave the way to gain a more general knowledge on such site-specific adsorption processes.