Self-Assembled Monolayers of Alkanesulfonic and -phosphonic Acids on Amorphous Iron Oxide Nanoparticles

Abstract

We have functionalized amorphous Fe2O3 nanoparticles with alkanesulfonic and octadecanephosphonic acids. TEM reveals nanoparticles 5−10 nm in diameter. FTIR spectra suggest that while in all cases the alkyl chains are packed in a solid-like arrangement, packing disorder increased with decreasing chain length. TGA of the sulfonic acid-functionalized Fe2O3 nanoparticles shows that moieties started to decompose and desorb from the iron oxide surface at about 260 °C. In the case of the octadecanephosphonic acid (OPA)-functionalized Fe2O3, moieties started to decompose and desorb at 340 °C. It is suggested that free Fe−OH groups can serve as proton donors to assist in the sulfonic acid desorption process and that because of the diprotic nature of the phosphonic acid these free surface Fe−OH groups may no longer be available. Among all, the octadecanesulfonic acid coating displays the lowest magnetization, which may be explained by the high packing and ordering of the alkyl chains on the particle surface. The saturation curve of the OPA case gives the smallest value of magnetization we have ever measured for functionalized Fe2O3 nanoparticles. It is suggested that the spin state of surface Fe3+ ions is affected by the bonded surfactant, through a mechanism of pπ−dπ P−O, and dπ−dπ Fe−P interactions and that the phosphonate empty d orbitals increase magnetic interactions between neighboring Fe3+ spins.

Role of polymeric surfactants on the growth of manganese ferrite nanoparticles

“…After complete aggregation of the building blocks at higher temperatures and longer times, the amount of desorption significantly decreased. Some researchers explained that the TGA behaviors are based on the bi-layer adsorbed models on the particle surface [45,46], while others claimed that the double-stepped TGA curve is due to two different kinds of binding sites [47,48]. Based on experimental results, it seems that the TGA curves for our samples are in agreement with the two different binding sites on the surface of the nanoparticles.…”

Precise surface structure control of inorganic solid and metal oxide nanoparticles through surface-initiated radical polymerization

“…Actually, the stability of P-O-M bonds is demonstrated by numerous metal phosphate compounds [6,30,31] such as those including Zn, Al, Zr, Fe, and Ti. The authors wish to report here the surface modification of Fe 3 O 4 and TiO 2 nanoparticles by phosphoric acid derivatives having a TEMPO-based initiator moiety to produce polystyrene brush via NMRP system.…”

Enhanced magnetic properties of polymer-magnetic nanostructures synthesized by ultrasonication

“…The band of stretching mode of the metals was found to be in the range of 600-500 cm -1 [12]. The bands in the range 600-500 cm -1 and 1087 cm -1 were suppressed upon addition of PVA into NiCoFe 2 O 4 which confirmed the functionalization of Ni-Co ferrites with PVA by forming hydrogen bond [13].…”

“…Various techniques have been suggested to synthesize nanophase materials such as mechanical milling [11], reversed micelles [12] and self-assembled monolayer [13]. Apart from above mentioned techniques, ultrasonication is a homogenizer to diminish particles size in a liquid to improve uniformity and stability.…”