A group of civil and environmental engineering graduate students at the University of Wisconsin-Madison is designing an affordable, easy-to-use test that will allow residents to identify lead in their tap water.
For the students, it’s literally a golden opportunity to make a big difference in human health: Their system—a color-changing solution that detects lead in tap water—uses gold nanorods attached to silica nanoparticles.
The solution turns from a wine-red color to colorless when lead is present. PhD student Hanwei Wang says that’s due to an effect called “localized surface plasmon resonance.” For gold, that means the electrons in nanoparticles—which are smaller than a wave of visible light—resonate with light waves and produce different shades depending on the nanoparticles’ size and shape.
“When lead is present, there’s a chemical reaction happening that etches the gold nanorods, shortening them,” Wang says. “That changes the color of the water with the solution in it. The higher the concentration of lead, the lighter the water sample’s color becomes.”
In fact, in the team’s experiments lead turns the red solution clear. The students have used colorimetric sensing, a form of spectroscopy, to evaluate the test results.
Read the full article here: https://engineering.wisc.edu/news/for-at-home-tap-water-test-under-development-seeing-red-means-no-lead/