"By using a maximum likelihood single molecule localization method, the molecule can be localized with single nanometer accuracy," Zhang says. "After the dye molecule is bleached (typically within hundreds of milliseconds), the fluorescence disappears and the hotspot is ready for the next adsorption event."
Choosing the right concentration of the dye molecules enables the adsorption rate on the surface of a hotspot to be controlled so that only one adsorbed molecule emits photons at a time. Since BEAST uses a camera to record the single molecule adsorption events, multiple hotspots within a field of view of up to one square millimeter can be imaged in parallel.
In their paper, Zhang and his colleagues see hotspots being put to use in a broad range of applications, starting with the making of highly efficient solar cells and devices that can detect weak chemical signals.
"A hotspot is like a lens that can focus light to a small spot with a focusing power well beyond any conventional optics," Cang says. "While a conventional lens can only focus light to a spot about half the wavelength of visible light (about 200-300 nanometers), we now confirm that a hotspot can focus light to a nanometer-sized spot."
Through this exceptional focusing power, hotspots could be used to concentrate sun light on the photocatalytic sites of solar devices, thereby helping to maximize light- harvesting and water-splitting efficiencies. For the detection of weak chemical signals, e.g., from a single
molecule, a hotspot could be used to focus incident light so that it only illuminates the molecule of interest, thereby enhancing the signal and minimiz
|Contact: Xiang Zhang|
DOE/Lawrence Berkeley National Laboratory