The ultra-sensitive optical sensor (IMAGE) Chalmers University of Technology Caption The new sensor is based on an optical phenomenon, plasmons, which occur when metal nanoparticles capture light and give the particles a distinct colour. This colour changes when the amount of hydrogen in the surroundings varies and the sensor can alarm at critical levels. Credit Illustration: Chalmers University of Technology | Yen Strandqvist Usage Restrictions Images provided in Chalmers University of Technology press releases are, unless specified otherwise, free for download and publication as long as credit is given to the University and the individual creator. Cropping and rescaling of the images is permitted when required for adaptation to the publication’s format, but modifications that would influence the message and content of the original are not. The material is primarily intended for journalistic and informative use, to assist in communication and coverage of Chalmers’ research and education. Commercial usage, for example the marketing of goods and services, is not permitted. We kindly request credit to be given in the following format where possible: Image/Graphic/Illustration: Chalmers University of Technology | Name Surname License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.