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| In the laser laboratory, Tlek Tapani and Nicolò Maccaferri are testing how porous structures enable gold to absorb more light energy than ordinary gold. Photo Credit: Mattias Pettersson |
Scientific Frontline: "At a Glance" Summary
- Main Discovery: Reshaping gold into a sponge-like nanoporous structure fundamentally alters its interaction with light, drastically enhancing its electronic properties and optical absorption without modifying its chemical composition.
- Methodology: Researchers fabricated thin films of nanoporous gold metamaterial and exposed them to ultrashort laser pulses, utilizing advanced electron microscopy and X-ray photoelectron spectroscopy (XPS) to isolate morphology-driven behaviors from intrinsic electronic structure changes.
- Key Data: The electronic temperature within the nanoporous gold film reached approximately 3200 K (~2900 °C), significantly higher than the 800 K (~500 °C) observed in standard solid gold films under identical conditions.
- Significance: This structural modification generates highly energetic "hot" electrons that take longer to cool, enabling light-induced transitions and chemical reactions that are nearly impossible to achieve with unstructured gold.
- Future Application: Optimizing efficiency in hydrogen production, carbon capture, catalysis, energy harvesting, and the development of quantum batteries and smart materials for sustainability.
- Branch of Science: Nanophysics, Material Science, and Ultrafast Optics.
- Additional Detail: The electronic behavior is tunable by systematically varying the filling factor—the ratio of gold to air within the sponge structure—establishing physical architecture as a scalable design parameter for various materials.
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| The nanoporous structure allows the gold to interact with light in a way that would otherwise not be possible. Image Credit: Generated by AI |
By changing the physical structure of gold at the nanoscale, researchers can drastically change how the material interacts with light – and, as a result, its electronic and optical properties. This is shown by a study from Umeå University published in Nature Communications.
Gold plays a crucial role in modern advanced technology thanks to its unique properties.
New research now demonstrates that changing the material's physical structure – its morphology – can fundamentally enhance both its electronic behavior and its ability to interact with light.
“This might make it possible to improve the efficiency of chemical reactions such as those used in hydrogen production or carbon capture,” says Tlek Tapani, one of the leading researchers behind the study and doctoral student at the Department of Physics.
Absorbs more light energy
The researchers worked with nanoporous gold, a so-called metamaterial produced in a laboratory. Thanks to its sponge-like structure, nanoporous gold has even better properties for technical applications than ordinary solid gold.
In this study, the researchers observed that a thin film of nanoporous gold interacts with light in ways that solid gold cannot. By exposing the "gold sponge" to ultrashort laser pulses, they found that the porous structure allows the material to absorb more light energy over a wider spectrum.
As a result, the electrons become considerably more energetic. The electronic temperature was estimated to reach about 3200 K (~2900 °C) in the nanoporous film, compared with just 800 K (~500 °C) in the unstructured gold film used as a reference, under the same conditions. It also takes longer for the "hot" electrons to cool down and return to their initial state at room temperature.
“Such elevated electronic temperatures enable light induced transitions that would otherwise be nearly impossible,” says Nicolò Maccaferri, leader of the Ultrafast Nanoscience Unit at the Department of Physics and senior author of the article. “Interestingly, using advanced electron microscopy and X-ray photoelectron spectroscopy experiments (XPS) here at Umeå University, we were able to confirm that these unique behaviors are driven solely by the material's physical shape and not by changes to the electronic structure of gold itself.”
Can be extended to other materials
The experiments suggest that nanoporous structures can be used as a new design parameter to engineer materials used in advanced technologies. By systematically varying the filling factor (the ratio of gold to air in the “sponge"), researchers can tune the electronic behavior of not only gold but also other metals in a controllable way, which could improve the efficiency of chemical reactions.
“Our research shows that by manipulating material architecture at the nanoscale, we can use structure itself as a design parameter,” says Nicolò Maccaferri. “These results can be generalized, in principle, to every material, with implications in how we design smart materials for sustainability and technology, with applications spanning from catalysis to energy harvesting, medicine and quantum batteries.”
Published in journal: Nature Communications
Authors: Tlek Tapani, Jonas M. Pettersson, Nils Henriksson, Carla M. Brunner, Ann Céline Zimmermann, Erik Zäll, Nils V. Hauff, Lakshmi Das, Anastasiia Sapunova, Gianluca Balestra, Massimo Cuscunà, Aitor De Andrés, Tommaso Giovannini, Denis Garoli, and Nicolò Maccaferri
Source/Credit: Umeå University | Sara-Lena Brännström
Reference Number: phy020226_01