A new label-free optical imaging technique based on unscattered light can detect nanoparticles as small as 25 nm in diameter. The technology overcomes several limitations of other advanced methods for imaging tiny particles, and its developers at the University of Houston and the University of Texas M D Anderson Cancer Center in the US say it might be used to study viruses and other structures at the molecular level.
Imaging nanoscale objects via optical techniques is difficult for two reasons. First, the objects’ small size means that they scatter little light, making it hard to distinguish them from the background. Second, individual nano-objects within a close-packed group tend to be separated by distances that are smaller than the diffraction limit for visible light (around a few hundred nanometres) making it impossible to resolve them with conventional methods.
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