Construction of conventional metasurfaces with unconventional interband plasmonics: a versatile route for sustainable bismuth-based structural color generation
The colors generated by the different types of proposed nanostructures have been found to discolor less than traditional pigments.
This project is partly funded by the European Marie Slodowska Curie METASCALE project and the national ASSESS MCIN/AEI/NextGenerationEU/PRTR project.
Madrid /January 10, 2024
A team of researchers led by the Laser Processing group of the IO-CSIC has published in the journal Advanced Optica Materials the development of a new technique for the sustainable and economical generation of structural colors using plasmonic metasurfaces..
Unlike conventional approaches that require expensive noble metals such as gold and silver to generate these metasurfaces, this study focuses on the use of alternative plasmonic materials such as bismuth, a much more economical and environmentally friendly material. The results of this research offer a cost-effective and robust solution for the fabrication of colored metasurfaces with the potential to be applied in industry replacing more polluting techniques.
Plasmonic metasurfaces consist of nanometer-sized elements that can be designed to reflect only certain colors through different optical interactions. That is, when white light interacts in the nanostructures some wavelengths are selectively cancelled or reflected and the set of the latter results in the observation of the desired color.
In most cases, noble metals such as gold and silver are used to build these structures due to their excellent plasmonic properties in the visible spectrum. However, these metals are scarce and expensive. The research team has explored the use of interband plasmonic materials, whose plasmonic-like optical properties are based on their interband electronic transitions rather than on their free carriers. Bismuth (Bi) is one such interband plasmonic material, and has proved to be an attractive alternative to gold and silver. In addition to being cheaper, bismuth is environmentally friendly.
Researchers have designed and fabricated two different types of metasurfaces using Bismuth prepared through pulsed laser growth. Carlota Ruiz de Galarreta (IO CSIC/University of Exeter), has been responsible for the design and fabrication of square arrays of nanodiscs arranged on a dielectric/metal bilayer system. Another structure that does not require the formation of nanodiscs is also being studied, which has been designed and fabricated by Fernando Chacón-Sánchez with nanocoatings that form Fabry-Pérot-type cavities. Both structures make it possible to generate different pure and durable colors by adjusting the dimensions of the nanometric elements that form them. The figure shows the two structures.
Schematic of bismuth-based nanostructures for color reflection, on the right, Fabry Perot cavities and on the left metasurfaces formed by nanodiscs arranged in a square lattice.
Experimental comparison between metasurfaces composed of nanodiscs and planar metasurfaces with Fabry-Pérot cavities revealed that the former are excellent for color microprinting, while Bi Fabry-Pérot cavities formed by nanoflakes are ideal for macroscopic-sized color coatings due to their simplicity and ease of fabrication. These findings demonstrate the potential of bismuth as a plasmonic material for a variety of applications, including color displays, anti-counterfeiting imaging, holography and colorization.
The general use of interband plasmonic materials opens up new possibilities in the generation of structural colors. In addition to bismuth, it has been observed that other materials such as indium and antimony also exhibit suitable plasmonic behaviors in different regions of the electromagnetic spectrum and can replace noble metals in various plasmonic-based applications.
This study represents a significant advance in the field of plasmonics knowledge and for the industry in the generation of sustainable structural colors. The use of interband plasmonic materials, such as bismuth, not only offers a more cost-effective and environmentally friendly alternative, but also expands the possibilities for the design and fabrication of nanophotonic devices for structural color.
This is a research work of the Laser Processing Group in collaboration with the Centre for Metamaterial Research and Innovation, the Department of Applied Physics of the Universidad Autónoma de Madrid, the Department of Physics, Carlos III University of Madrid , thePOLYMAT Institute of the University of the Basque Country UPV/EHU and International Iberian Nanotechnology Laboratory (INL)
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