A sonochemical approach to the direct surface functionalization of superparamagnetic iron oxide nanoparticles with (3-aminopropyl)triethoxysilane

Abstract

We report a sonochemical method of functionalizing superparamagnetic iron oxide nanoparticles (SPION) with (3-aminopropyl)triethoxysilane (APTES). Mechanical stirring, localized hot spots and other unique conditions generated by an acoustic cavitation (sonochemical) process were found to induce a rapid silanization reaction between SPION and APTES. FTIR, XPS and XRD measurements were used to demonstrate the grafting of APTES on SPION. Compared to what was reported in literature, the results showed that the silanization reaction time was greatly minimized. More importantly, the product displayed superparamagnetic behaviour at room temperature with a more than 20% higher saturation magnetization.

Keywords: (3-aminopropyl)triethoxysilane (APTES); functionalization; nanoparticles; silanization; sonochemical; superparamagnetic iron oxide nanoparticles (SPION).

Scheme 1

Schematic representation of the sonochemical synthesis of APTES-functionalized SPION.

Figure 1

FTIR spectrum of (a) naked SPION (b) APTES-functionalized SPION. The binding of APTES onto the SPION is revealed by the 1109 and 1044 cm⁻¹ peaks assigned to the Si–O–Si bond.

Figure 2

XPS spectrum showing APTES functionalized SPION, the bands at 103, 287 and 402 eV correspond to the presence of silicon, carbon and nitrogen on the surface of the SPION.

Figure 3

XRD pattern of APTES-functionalized SPION with the peaks correspond to either magnetite or maghemite compared with JCPDS 5-0664.

Figure 4

(a) TEM micrograph of the APTES–SPION (b) Magnetization curves of the APTES-functionalised SPION at 300 K.