Qf400

The sprayed products were examined by powder XRD (SmartLab Diffractometer, 40 kV, 40 mA), SEM (FEI QF400, attached with an EDX analysis system), TEM (FEI TS12, 120 kV), high-resolution TEM (FEI TF20, 200 kV), UV-visible diffuse reflectance spectroscopy (UV-2450, Shimadzu), and HAADF-STEM imaging and elemental mapping (FEI TF20, 200 kV). Nitrogen sorption isotherms were measured on a Micromeritics TriStar 3000 system at the liquid-nitrogen temperature. The specific surface area and pore size distribution were analyzed according to the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda model, respectively.

An optical microscope (Olympus,
BX53M) equipped with a monochromator
(Acton, SpectraPro 2360i) and a charge-coupled device camera (Princeton
Instruments, Pixis 400, cooled to −70 °C) was used to
measure the dark-field scattering spectra. A 100× dark-field
air objective (Olympus, numerical aperture: 0.9) was used for scattering
measurements. Light from a halogen lamp passed through the objective
and illuminated the sample obliquely. The backward scattered light
passed through the same objective. Dark-field differential scatterometry
can provide richer information than optical measurements of the solution
samples containing the randomly orientated CGNCs. Circularly polarized
excitation in our experiments was realized by a linear polarizer and
a quarter-wave plate, both of which were purchased from Union Optic.
The working wavelength of the quarter-wave plate (WPA4420–550–750)
is 550–750 nm. The polarization handedness convention used
in this work is such that the RCP and LCP vectors rotate clockwise
and counterclockwise along the propagation axis, respectively. The
wavelengths of the scattering peaks were extracted by fitting the
scattering spectra with Gaussian functions. Extinction spectra were
measured on a PerkinElmer Lambda 950 ultraviolet/visible/near-infrared
spectrophotometer. SEM imaging was carried out on an FEI QF400 field-emission
scanning electron microscope operated at a rate of 20 kV.