pictures were collected with a Tecnai G2 20 S-TWIN TEM. Scanning electron
microscopy (SEM) pictures were obtained by a JEOL JSM6700-F. Raman
spectra were recorded by a LabRamHREvo 800 (HORIABA JobinYvon, France).
UV–vis–NIR absorbance spectra were measured on a Varian
Cary5000 spectrophotometer. Fluorescence spectra were acquired by
using a PerkinElmer LS 55 spectrofluorimeter. Fourier-transform infrared
(FTIR) spectroscopic measurements were conducted with a Varian 800
FT-IR. The ζ potentials were measured on a Malvern Zetasizer
Nano ZS.