Plasma-attached gold nanoparticles are useful for thermal history sensing

Researchers have demonstrated that memory-shaped polymers interspersed with accumulations of gold nanoparticles alter their plasmon bond, resulting in desirable optical properties. One potential application is for the sensor material that relies on optical properties to monitor the thermal history of an object or environment.

There is a question of an accessible polymer rooted in gold nanospheres. If the material is heated and stretched, and then cooled to room temperature, the material retains its stretched shape indefinitely. When reheated to 120 degrees Celsius, the material returns to its original shape.

But what is very interesting is that the gold nanospheres are not perfectly dispersed in the polymer. Instead, they form plates, in which their surface plasmon repeats are attached. These plasmon-bonded nanoparticles have optical properties that move according to how close they are to each other, which changes as stretching changes the shape of the cement.

“When evaluating the maximum light wavelength that the material absorbs, there are significant differences depending on whether the polarized light is parallel or perpendicular to the stretch guidance, “says Joe Tracy, associate author of a paper on the work and professor of materials. science and engineering at NC State.” For polarized light parallel to stretch guidance, the longer you have the material stretch, the longer the light moves to the red. For polarized light perpendicular to the stretched direction is blueshift. “

“We also found that while the shape memory polymer retains its shape at room temperature, it regains its original shape in an expected way, depending on the temperature it takes. it ‘s open, “said Tobias Kraus, co – author of the paper, group director of the Leibniz Institute for New Materials and a professor at the University of Saarland.

In particular, once it is stretched 140% beyond its original length, you can determine the maximum temperature at which the polymer is then exposed, up to 120 degrees Celsius, by measure how much it has shrunk back to its original size. Furthermore, due to the plasmon-bound nanoparticles, this change can be measured indirectly, through measurements of the optical properties of the material.

“From a practical point of view, this allows you to create an optical thermal history sensor,” says Joe Tracy. “You can use light to see how hot the material has gotten. An important application of thermal history sensors is to determine the quality or safety of shipping or storage of materials that are sensitive to significant changes in heat. We have demonstrated an approach based on plasmon bonding of gold nanoparticles. “

The concept of the sensor was developed imperially, but the researchers used computer modeling to better understand the structure of the collections of gold nanospheres and how the collections changed during stretching. Plasmon bond strength is related to the gaps between nanospheres, known as the “plasmon regulator.”

“Based on our simulations, we can estimate the distance between plasmon-bonded nanoparticles from their optical properties,” says Amy Oldenburg, co-author of the paper and professor of physics at the University of North Carolina at Chapel Hill. “This comparison is informative for the design of future polymer nanocomposites based on plasmon-bonded nanoparticles.”