Research on 'smart glass' may provide new ideas for fuel cell development

Smart glass "is an energy-saving product that can be found in windows of cars, buildings, and airplanes. However, smart glass usually takes several minutes to reach a dull state, and cycling between light and dark for a long time can also reduce the quality of coloring. According to foreign media reports, chemists at Colorado State University have proposed a nanoscale smart glass design method by better understanding the working principle of smart glass at the nanoscale, which may improve the color changing speed and durability of smart glass.

Colby Evans, a graduate student at the university, and Justin Sambur, an assistant professor in the Department of Chemistry, are researching "electrochromic" smart glass. Its working principle is to use voltage to drive lithium ions in and out of tungsten oxide transparent films. Evans said, "You can imagine it as a see through battery." A typical tungsten oxide smart glass plate takes 7-12 minutes from transparency to complete color change.

Researchers focus on studying electrochromic tungsten oxide nanoparticles, which have a width 100 times smaller than human hair. Experiments have shown that the coloring speed of a single nanoparticle is four times faster than that of a thin film composed of the same particles. This is because the interface between nanoparticles in the film captures lithium ions, slowing down the coloring behavior. Over time, the performance of the material will also decrease.

To prove their point, researchers used a bright field transmission microscope to observe how tungsten oxide nanoparticles absorb and scatter light. When making "smart glass" samples, they constantly change the amount of nanoparticle materials in the sample, observe their mutual contact and changes in coloring behavior as the number of nanoparticles increases. Then, they used scanning electron microscopy to capture high-resolution images of the nanoparticles, covering length, width, and spacing, in order to determine how many particles were clustered together, how many were dispersed, and so on.

Based on the experimental results, researchers propose that if materials based on nanoparticles are manufactured and the particles are kept at the optimal spacing to avoid ion capture, it may be possible to improve the performance of smart glass. This method can also be used to guide the application research of batteries, fuel cells, capacitors, and sensors.