under a Tecnai G2 F20 S-TWIN field emission TEM (FEI, USA) equipped
with an energy dispersive X-ray (JEOL, Japan). The FTIR spectra were
recorded in a Frontier FTIR spectrometer (PerkinElmer, USA) with KBr
disks in the wave number range of 600–4000 cm–1. The XPS measurements were conducted on a Kratos AXIS Ultra DLD
spectrometer (Kratos Analytical, UK) under monochromatized Al Kα
X-ray radiation (1486.6 eV). The organic loading in Ni3Si2O5(OH)4-g-P4VP
NTs was measured by thermogravimetric analysis (TGA) performed with
a TGA/DSC2 thermogravimetric analyzer (Mettler Toledo, Switzerland)
at a heating rate of 20 °C/min from 30 to 700 °C under nitrogen
atmosphere. The paramagnetic properties of the magnetic particles
were verified by the magnetization curve measured by vibrating sample
magnetometry. The content of chromium was determined by an atomic
absorption spectrophotometer(Varian AA 320, Varian Inc. Palo Alto,
CA).