Luminescence of UCNPs. a, Schematic of energy transfer upconversion with Yb3+ as sensitizer and Er3+ as emitter. b, Minimum peak excitation intensities of NIR light needed for multiphoton single-molecule imaging of various classes of luminescent probes. The peak excitation intensity ranges shown are required to detect signals of 100 c.p.s. Credit: Courtesy Daniel Gargas, Emory Chan, Bruce Cohen, and P. James Schuck, The Molecular Foundry, Lawrence Berkeley National Laboratory When imaging at the single-molecule level, small irregularities known as heterogeneities become apparent – features that are lost in higher-scale, so-called ensemble imaging. At the same time, it has until recently been challenging to develop luminescent probes with the photostability, brightness and continuous emission necessary for single-molecule microscopy. Now, however, scientists in the Molecular Foundry at Lawrence Berkeley National Lab, Berkeley, CA have developed upconverting nanoparticles (UCNPs) under 10 nm in diameter whose brightness under single-particle imaging exceeds that of existing materials by over an order of magnitude. The researchers state that their findings make a range of applications possible, including cellular and in vivo imaging, as well as reporting on local electromagnetic near-field properties of complex nanostructures. Read more at: Phys.org
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