Facile fabrication and superparamagnetism of silica-shielded magnetite nanoparticles on carbon nitride nanotubes

Abstract

Using conventional methods to synthesize magnetic nanoparticles (NPs) with uniform size is a challenging task. Moreover, the degradation of magnetic N Ps is an obstacle to practical applications. The fabrication of silica-shielded magnetite NPs on carbon nitride nanotubes (CNNTs) provides a possible route to overcome these problems. While the nitrogen atoms of CN NTs provide selective nucleation sites for N Ps of a particular size, the silica layer protects the NPs from oxidation. The morphology and crystal structure of NP-CNNT hybrid material is investigated by transmission electron microscopy (TEM) and X-ray diffraction. In addition, the atomic nature of the N atoms in the NP-CNNT system is studied by near-edge X-ray absorption fine structure spectroscopy (nitrogen K-edge) and calculations of the partial density of states based on first principles. The structure of the silica-shielded NP-CNNT system is analyzed by TEM and energy dispersive X-ray spectroscopy mapping, and their magnetism is measured by vibrating sample and superconducting quantum interference device magnetometers. The silica shielding helps maintain the superparamagnetism of the NPs; without the silica layer, the magnetic properties of NP-CNNT materials significantly degrade over time. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.