Plasma cleaner

Glass slides were sonicated for 5 min with HellmanexIII (Sigma-Aldrich), washed 5 x with double distilled water and sonicated for 5 min each with Acetone (Roth) and 2-Propanol (Roth). Clean glass slides were blown dry with nitrogen and glow discharged under oxygen in a plasma cleaner (Binder) for 5 min. In order to locate the sample in the center of the glass slide a circle was drawn with a grease pencil on the glass slide. Open and closed state DNA origami structures with AuNPs attached (50 pM) were deposited inside the grease circle for one minute, washed two times with 1 ml doubly distilled water and blown dry with nitrogen. Samples for Darkfield microscopy were imaged with a home-built dark-field setup in transmission mode using a 100 x air objective (Olympus) and an oil condenser (Olympus NA 1.4) with a 100 W halogen bulb as illumination source. Images were taken with 100 ms exposure time and 2 x binning on a color CMOS Camera (Thorlabs Kiralux CS895CU). The dark-field scattering spectra were collected with the same home-built dark-field coupled to an Acton SP2300 spectrometer (Princeton Instruments). To analyze the RGB intensity values of individual nanostructures, the images were first thresholded and individual spots then automatically detected.

The empty grid (formvar/carbon - coated, 300 mesh Cu; Ted Pella, Inc) was glow discharged under Argon in a plasma cleaner (Binder) for 60 s. The purified DNA origami structures were immobilized on the freshly treated grids for 3 min, followed by a washing step and a 10 second staining step each with a drop of a 2 % w/v Uranyl formate solution (SPI supplies). The negative stained DNA origami structures were imaged using a JEM-1011 (Jeol) transmission electron microscope operating at 80 kV.