To perform colocalized AFM imaging and Raman measurements on the purified DNA origami nanoantenna, or DONA. first treat a silicone chip with plasma for 10 minutes. Incubate 10 microliters of the purified DONA solution and 10 microliters of 100 millimolar magnesium chloride on the chip for three hours.
Then wash the chip two times with an ethanol-water mixture and blow dry with compressed air. Tape the dried chip on a magnetic disc and insert it into the instrument for atomic force microscopy or AFM imaging. Next, choose the desired laser wavelength, power, and accumulation time for the Raman measurements.
For gold nanoparticle fully coated with TAMRA, select a 633 nanometer laser, 100 microwatt power, and one second integration time. For a single TAMRA measurement, change to 400 microwatt power and four second integration time. After adjusting the parameters, place the cursor on top of the desired DONA in the AFM image.
Then start the Raman measurement. For colocalization measurements, AFM imaging of the sample was performed to locate the DONAs. Following that, Raman spectra from single DONAs were collected and compared to ensure that the spectra obtained were from TAMRA molecules.
The main TAMRA peaks were visible in the fully coated TAMRA gold nanoparticle, although the signal-to-noise ratio for the single molecule TAMRA spectra was lower, the main peaks were identifiable.
