title: Stabilization of superparamagnetic iron oxide nanoclusters in concentrated brine with cross-linked polymer shells.
abstract: Iron oxide nanoparticles, in the form of sub-100-nm clusters, were synthesized in the presence of poly(acrylic acid) (PAA) or poly(styrene sulfonate-alt-maleic acid) (PSS-alt-MA) to provide electrosteric stabilization. The superparamagnetic nanoclusters were characterized using a superconducting quantum interference device (SQUID), transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and zeta potential measurements. To anchor the polymer shell on the nanoparticle surface, the polymer was cross-linked for a range of cross-linking densities. For nanoclusters with only 12% (w/w) PSS-alt-MA, electrosteric stabilization was sufficient even in 8 wt % NaCl. For PAA, the cross-linked polymer shell was essentially permanent and did not desorb even upon dilution of the nanoparticles for iron oxide concentrations down to 0.014 wt %. Without cross-linking, over half of the polymer desorbed from the particle surfaces. This general approach of the adsorption of polymer stabilizers onto nanoparticles followed by cross-linking may be utilized for a wide variety of cross-linkable polymers without the need to form covalent bonds between the nanoparticles and polymer stabilizer. Thus, this cross-linking approach is an efficient and inexpensive method of stabilizing nanoparticles for large-scale applications, including the electromagnetic imaging of subsurface reservoirs, even at high salinity.
authors: Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, USA.
authors: Ki Youl
authors: KY
authors: Yoon
authors: Csaba
authors: C
authors: Kotsmar
authors: Davis R
authors: DR
authors: Ingram
authors: Chun
authors: C
authors: Huh
authors: Steven L
authors: SL
authors: Bryant
authors: Thomas E
authors: TE
authors: Milner
authors: Keith P
authors: KP
authors: Johnston
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008298:Maleates / Q000737:chemistry*; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry*; D012492:Salts / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; D058185:Magnetite Nanoparticles; D008298:Maleates; D011137:Polystyrenes; D012492:Salts; C017082:brine; C006903:carbopol 940