Ultraplus field emission

NP size, polydispersity, and superficial
charge are measured by dynamic light scattering (DLS, Zetasizer Nano
ZS, Malvern U.K.). Typically, 1 mL of the diluted sample is put in
12 mm square glass cuvettes for 90° sizing (Optical Cuvette,
Sarstedt) and measured at least in triplicate. ζ potential measurements
are performed at room temperature on a Zetasizer Nano ZS (Malvern,
U.K.), fitted with a high-concentration ζ potential cell. Nanoparticle
morphology is assessed by scanning and transmission electron microscopy,
SEM and TEM, respectively. For SEM observations (Carl Zeiss Ultraplus
Field Emission), 100 μL of purified samples are dropped on a
polycarbonate isopore membrane filter (cutoff 0.05 μm) under
vacuum ultrafiltration and let dry overnight. Before the observation,
5–7 nm of Au is deposited on the sample. For cryo-TEM observation
of EVs (Cryo-TEM TECNAI by FEI), 5 μL of the purified sample
is dropped on a Formvar/Carbon 200 mesh grid (Agar scientific) and
observed at an 80 kV accelerating voltage. The concentration of cHANPs
and EVs is quantified by nanoparticle tracking analysis NTA (Nanosight
NS300, Malvern Instruments Ltd., U.K.). Both samples are observed
at a dilution of 1:100, at 25 °C for 300 s with a manual shutter
and gain adjustment. Results are analyzed with NP Tracking Analysis
software.

The scanning electron microscope (SEM) images were obtained using Zeiss Ultra Plus field emission scanning electron microscope with an electron energy of 5 kV. Atomic force microscope (AFM) images were obtained using a nanoscope scanning probe microscope (Dimension fastscan, Bruker, Germany) under ambient conditions. Au coating was sputtered on the surface of the polymer nanostructure arrays using an ion sputtering apparatus (E-1045, Hitachi, Japan). The light absorption performance of substrates were measured using a spectrophotometer (Shimadzu UV3600, Shimadzu, Japan) combined with an integrating sphere for the 300−800 nm wavelength range. For Raman scattering measurements, 10 μL R6G aqueous solution (10⁻⁶ M) was dropped onto the substrates and then dried in the dark. Also, the same amount of 10⁻¹ M R6G solution was drop-casted on glass to get reference Raman spectra. SERS spectra were collected using a Dispersive Raman Microscope (Senterra R200-L, Bruker Optics, Germany).

Size and polydispersity of the bare and conjugated cHANPs are measured by dynamic light scattering (DLS) by Zetasizer Nano, Malvern Panalytical (UK). The size measurement is performed dropping 1 mL of suspension in a square glass cuvette (Optical Cuvette, Sarstedt) at room temperature in triplicate.
Scanning electron microscopy (SEM), Carl Zeiss Ultraplus Field Emission, Zeiss (Germany) and transmission electron microscopy (TEM), Cryo-TEM TECNAI G2-20, and FEI (OR, USA) observations are performed to investigate the nanoparticle morphology.
For SEM observations, 200 μL of suspension is deposited by ultrafiltration on polycarbonate Isopore™ membrane filters with a 50 nm cut-off by Merck KGaA (Germany) then left to dry. A 7 nm Au layer is deposited via sputter coating on the membrane filter that is observed at 10 kV. 20 μL of suspension is dropped on copper grids with carbon film by Agar Scientific Ltd. (Stansted, UK) and left to dry prior to observation at 120 kV.