Smart gold particles control light and chemical reactions
Physicist Quynh Nhu Nguyen has developed a new way to precisely tune tiny gold particles to interact with light. The results could contribute to more efficient sensors, better solar cells and new forms of light-controlled chemistry.
The research focused on so-called core-shell nanoparticles: extremely small gold particles coated with a thin layer of another material. By precisely controlling the size, shape and composition of these particles, it turns out that it is possible to specifically modify their optical properties.
Among other things, Nhu Nguyen developed a method for coating gold particles with a shell of aluminum-doped zinc oxide. In doing so, she was able to independently vary the size of the gold core, the thickness of the shell and the amount of aluminum. This created a great deal of control over how the particles absorb and scatter light.
In addition, Nhu Nguyen discovered that light itself can be used to grow a silver difference on gold particles. In the process, it was found that small spherical gold particles use absorbed light particularly efficiently to drive chemical reactions. In contrast, in gold particles with sharp edges and corners, silver growth proceeded differently: there, silver formed mainly on the edges of the particle.
To investigate the processes, Nhu Nguyen made the nanoparticles step by step in liquid with colloidal chemistry. Then she analyzed the properties with spectroscopy and electron microscopy. This allowed her to track exactly how light, shape and material combine to determine the behavior of the nanoparticles.
Nanomaterials that can efficiently direct or amplify light play an important role in future technologies. For example, they can be used in highly sensitive sensors for medical diagnostics or environmental measurements. They also offer opportunities for photonics, which uses light instead of electricity for information processing.
In addition, the technology can contribute to more efficient solar energy and more sustainable chemical processes. Because the particles use light to drive reactions, the prospect opens up for new forms of chemistry that use less energy and are more precise.
According to Nhu Nguyen, the work especially demonstrates the importance of nanoscale design: by cleverly building materials at the atomic and nano levels, completely new properties can emerge that do not occur at larger scales.
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