Those grinning faces are actually veinlike structures in a piece of grass. Phil Gates of Durham University created the glowing smiles in this micrograph by adding two dyes to a thin slice of a marram grass (Ammophila arenaria) and then shining blue-violet light on it. The first dye, calcofluor M2R, fluoresces blue when bound to cellulose. The second, Auramine O, fluoresces yellow when it binds to the plant polymers cutin and lignin. The blue smiles are made of phloem tissue, which carries nutrients around the plant and has pure cellulose cell walls. Chlorophyll-rich cells, which fluoresce brownish-red without any added dyes, can be exposed as the grooves in this sample open up in response to water in the air, uncurling the blades of grass and triggering photosynthesis.—Manny Morone
ALL THAT GLITTERS
Credit: Courtesy of Orlin Velev
About 15 minutes before this photo was taken, these droplets—mixtures of latex and gold nanoparticles in water—were all just a cloudy red. But as the water evaporated, a mosaic of colors appeared in each, a result of a phenomenon called structural color. Unlike color generated from dyes, which absorb and transmit certain colors of light, structural color like this comes from the arrangement of nanometer-size particles. As the droplets shrank due to evaporation, the latex particles were squeezed together into a crystalline structure. Depending on the spacing of the particles in that structure, which depended on the diameter of the latex spheres, different wavelengths of light were amplified in certain places in the droplet, resulting in the range of colors shown. The gold nanoparticles do not themselves significantly change the colors produced. Instead they increase the contrast between colors.
On the other side of this leaded glass window of an X-ray photoelectron spectrometer, researchers blast sample materials with X-rays, which causes the substances to emit electrons. Analyzing the quantity and energy of those electrons reveals detailed information on the surface chemistry of the sample. The bombardment takes place under a vacuum of 10−10 torr, which is comparable to what you’d find on the surface of the moon. The owner of this instrument, Anderson Materials Evaluation, uses it to study how adhesives and coatings fail.—Craig Bettenhausen