We have shown that superparamagnetic iron oxide (Fe3O4) nanoparticles with a surface functionalization of dimercaptosuccinic acid (DMSA) are an effective sorbent material for toxic soft metals such as Hg, Ag, Pb, Cd, and Tl, which effectively bind to the DMSA ligands and for As, which binds to the iron oxide lattices. The nanoparticles are highly dispersible and stable in solutions, have a large surface area (114 m2/g), and have a high functional group content (1.8 mmol thiols/g). They are attracted to a magnetic field and can be separated from solution within a minute with a 1.2 T magnet. The chemical affinity, capacity, kinetics, and stability of the magnetic nanoparticles were compared to those of conventional resin based sorbents (GT-73), activated carbon, and nanoporous silica (SAMMS) of similar surface chemistries in river water, groundwater, seawater, and human blood and plasma. DMSA-Fe3O4 had a capacity of 227 mg of Hg/g, a 30-fold larger value than GT-73. The nanoparticles removed 99 wt% of 1 mg/L Pb within a minute, while it took over 10 and 120 min for Chelex-100 and GT-73 to remove 96% of Pb.

Synthetic elaboration of self-assembled monolayers (SAMs) provides a powerful method for the preparation of smooth, ordered surfaces with carefully controlled functionality. Chemically rugged siloxane-based SAMs have been employed as a foundation for the preparation of a variety of functionalized surfaces. Nucleophilic displacements are described between halide-terminated SAMs and anionic nucleophiles (e.g. azide, thiocyanate, thiolate). Problems were encountered due to the steric congestion surrounding the terminal bromomethylene carbon. The concept of trajectory control is applied to these displacement reactions. In addition, reactions between ester-terminated SAMs and neutral nucleophiles (e.g. amines, hydrazine, hydroxylamine) are described. Evidence is presented suggesting that a modest amount of cross-linking (i.e. imide formation) takes place in the amidation reactions, while reaction stoichiometry indicates that cross-linking is virtually complete for the bifunctional nucleophiles. These synthetic elaborations were also carried out on mixed monolayers to create functionalized SAMs with systematically varied loading densities. Linear correlation (or lack thereof) of elemental composition to predicted functional composition is used to provide an estimation of reaction efficiency.