Large-Area Structural Color Filtering Capitalizing on Nanoporous Metal-Dielectric-Metal Configuration.

We present a highly efficient structural color filtering approach for large-area application, using a nanoporous anodic alumina (NAA) film overlaid with an aluminum (Al) layer on top of an optically thick Al substrate. The NAA film, consisting of a self-assembled nanopore array in a hexagonal lattice, is equivalent to a quasi-homogeneous medium according to effective medium theory. The proposed structure enables strong absorption at resonance owing to the Fabry-Perot resonance supported by the metal-dielectric-metal configuration and the plasmonic effect mediated by the top nanoporous Al layer. The reflection colors can be readily tuned by altering the NAA thickness that is determined by anodization time, thereby allowing the flexible creation of complicated color images on a single platform. By fabricating three samples with different NAA thicknesses in a large area of 2 cm × 2 cm, it is confirmed that the proposed color filtering scheme exhibits highly enhanced color purity and high reflection efficiency of up to 73%, which is superior to that generated by previously reported NAA-based approaches. The presented strategy can pave the way for the efficient fabrication of large-area color filtering devices for various potential applications, including color display devices, imaging sensors, structural color printing, and photovoltaic cells.

Near Room Temperature, Fast-Response, and Highly Sensitive Triethylamine Sensor Assembled with Au-Loaded ZnO/SnO2 Core-Shell Nanorods on Flat Alumina Substrates.

Chemiresistive gas sensors with low power consumption, fast response, and reliable fabrication process for a specific target gas have been now created for many applications. They require both sensitive nanomaterials and an efficient substrate chip for heating and electrical addressing. Herein, a near room working temperature and fast response triethylamine (TEA) gas sensor has been fabricated successfully by designing gold (Au)-loaded ZnO/SnO2 core-shell nanorods. ZnO nanorods grew directly on Al2O3 flat electrodes with a cost-effective hydrothermal process. By employing pulsed laser deposition (PLD) and DC-sputtering methods, the construction of Au nanoparticle-loaded ZnO/SnO2 core/shell nanorod heterostructure is highly controllable and reproducible. In comparison with pristine ZnO, SnO2, and Au-loaded ZnO, SnO2 sensors, Au-ZnO/SnO2 nanorod sensors exhibit a remarkably high and fast response to TEA gas at working temperatures as low as 40 °C. The enhanced sensing property of the Au-ZnO/SnO2 sensor is also discussed with the semiconductor depletion layer model introduced by Au-SnO2 Schottky contact and ZnO/SnO2 N-N heterojunction.