Near‐Field Optical Microscopes Take a Close Look at Individual Molecules

Researchers have recently looked at individual dye molecules with a resolution of about 50 nanometers, about six times finer than the diffraction limit for the 600‐nm light they are using. They achieved these unprecedented optical resolutions and the sensitivity needed for single‐molecule detection with nearfield scanning optical microscopy. This technique surpasses the diffraction limit by placing a subwavelength‐sized optical element within tens of nanometers of the sample: Traveling over such short distances, light has no opportunity to diffract and take on its asymptotic far‐field characteristics. And unlike other high‐resolution imaging techniques, such as electron microscopy and scanning tunneling microscopy, the technique allows the study of fluorescence in molecules’ natural biochemical environments, such as the biological membranes responsible for photosynthesis.

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