Multimode atomic force microscope

The electrical characteristics of the devices were measured using a Keithley 4200-SCS in a N₂-purged glove box. The dielectric film thicknesses were measured using an XP-1 surface profiling system (Ambios Technology, Inc.). Transmission electron microscope (TEM) images were taken using a Technai G2 S-Twin field-emission TEM operating at 200 keV. Atomic force microscopy (AFM) experiments were performed using a Digital Instruments Multimode atomic force microscope controlled by a Nanoscope IIIa scanning probe microscope controller. Chemical composition of the surface was characterized using an AXIS – NOVA (KRATOS Inc.) X-ray photoelectron spectrometer (XPS) with a scanning monochromatic Al source (1486.6 eV). The surface morphology of the films was imaged using a tapping-mode atomic force microscope (Nanoscope III, Veeco Instruments, Inc.) at the Korea Basic Science Institute (KBSI).

A comprehensive examination of the obtained products was conducted using a broad set of characterisation techniques. TEM images were obtained with Gatan Dualvison digital camera on a JEOL 1200EXII transmission electron microscope coupled with energy‐dispersive X‐ray spectroscopy (point resolution, 0.16 nm). Raman spectroscopy was carried out on a Renishaw inVia Raman spectroscopy. The specimens were either in solid state or dispersed in pure water (MilliQ) or water:ethanol 1 : 1 mixture. During the measurements, the carbon nanomaterials samples were deposited on an aluminium substrate. The laser wavelength was set at 514 nm. At least ten accumulations were generally acquired in Raman spectroscopy measurements, the beam was focused in at least three different positions across the specimen and these spectra were averaged to obtain batch‐representative peaks and most reliable results. Atomic force microscopy measurements were carried out with a Digital Instruments Multimode Atomic Force Microscope with IIIa controller. Thermogravimetric (TGA) measurements were carried out on a Polymer Laboratories STA 1500 Simultaneous Analysis System. Samples for TGA analysis were placed in a ceramic crucible which was heated from room temperature up to 900 °C at a rate of 2 °C per minute, with data points collected every 2 seconds under dynamic N2 flow (industrial grade, flow rate 100 ml min⁻¹).

A sheet of muscovite mica (V1, 9.5 mm in diameter) mounted on a metal specimen disc was used as a substrate. Freshly purified exosomes were diluted in DPBS (5 ng/10 µL), and 10 µL of the diluted solution was deposited onto a freshly-cleaved mica sheet. The resulting samples were air-dried. Salt (in DPBS) crystallized on mica was removed by careful washing the dried exosomes once with milliQ water. Exosomes were air-dried and examined using a Digital Instruments Multimode Atomic Force Microscope with Nanoscope IIIa electronics (Digital Instruments, Santa Barbara, CA). Tapping-mode AFM images (512 pixel × 512 pixel) were obtained in air using AFM probes purchased from Asylum (Model HQ-150-Au). These images (1 × 1 µm²) were analyzed using the particle analyzer of the ImageJ software [20 ] to assess particles larger than 78 pixel², which corresponds to 19.5 nm in diameter for circular particles. Similar AFM images were obtained for four different biological preparations of exosomes purified on different days. The total number of particles analyzed for UD-P19 and P19N exosome preparations were 890 and 1,330 respectively.