by American Chemical Society Appearing green on a vial lid (left), this structural color material becomes colorless (right) when warmed. Credit: Adapted from ACS Nano 2023, DOI: 10.1021/acsnano.3c00467 Some foods and medicines, such as many COVID-19 vaccines, must be kept cold. As a step toward a robust, stable technique that could indicate when these products exceed safe limits, researchers in ACS...
