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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 1 9 1 1 Imaging of aqueous poloxamer gel-based nanocomposites with fluid cell in situ. Left: Nanoparticles as small as ~6 nm are clearly seen in a surrounding thick gel matrix. Right: Intensity line scan of a random single particle dispersed in gel. of the two parts, while still allowing them to be pushed together or pulled away from each other. Such molecular pushing and pulling causes the mole- cule’s fluorescence to change from off to on. As intended, polymers contain- ing the new motifs do not fluoresce in the absence of mechanical force, but they become brightly fluorescent when stretched. Because no chemical bonds are broken, the process is fully revers- ible. Moreover, the fluorescence inten- sity, or brightness, correlates with the extent of deformation. www.unifr.ch , www.global.hokudai.ac.jp . DESCRIPTIVE MICROSCOPY METHOD Getting a close and accurate look at how nanoparticle-and-gel systems organize themselves has proven chal- lenging for scientists who want to understand their properties and how to control them. Now, scientists at the DOE’s Ames Laboratory, Iowa, devel- oped a new microscopy approach for imaging gel nanocomposites in their natural state, which will reveal more useful information about their assem- bly and properties. Researchers are excited about imaging nanoparticles in poloxamers, a group of oddly behaving polymer mate- rials that are liquid at low temperature and become a gel at higher tempera- tures. Due to their interesting phase behavior, these gels hold promise as a matrix medium for the arrangement of nanoparticles, which could enable de- velopment of materials with interesting optical properties. However, it is diffi- cult to image nanoparticles within a gel environment. Using a new approach with fluid cell scanning and transmis- sion electron microscopy, the research- ers are employing a molecular printer to deposit tiny volumes of poloxamer com- bined with gold nanoparticles and then observing them under controlled tem- perature and humidity. ameslab.gov.