Colloidal Metal Deposition onto Functionalized Polystyrene Microspheres

Abstract

Three different methods are described for uniformly anchoring metal colloids (Pt, Pd, and Au) onto the surface of polystyrene microspheres (PSMS). The first method we have employed is electrostatic deposition of preformed anionic colloidal particles onto a polycationic surface. In this method the functional groups on the surfaces of the microspheres (amine or carboxylic acid) are used to give the surface a net charge. These ionic spheres were then treated with polyelectrolytes of the opposite charge, which uniformly cover the surface. When the spheres have a net positive charge at the surface they show excellent adhesion of Au colloids. These metal-derivatized spheres can be prepared with electroactive viologen groups as well. In the second method investigated here, metal colloids are adsorbed to the surface of neutral functionalized PSMS. We report the synthesis and characterization of catalytically important noble monometallic colloids using various chemical and sonochemical methods. These metal colloids are then adsorbed onto suitably functionalized PSMS. The metal-immobilized microspheres are reacted with a linker such as 4-mercaptobutyl phosphonic acid and subsequently used for growing multilayers of ZrPV(Cl) (zirconium and N,N′-dialkyl-4,4′bipyridinium dichloride) by alternating Zr 4+ and PV(Cl). The third method described here for supporting metal particles on PSMS involves depositing a precursor metal oxide or hydroxide onto the PSMS, followed by reduction to give fine metal particles on the surface of the PSMS. Metal particle sizes formed by this method are 2-4 nm. The colloids, microspheres, and resulting catalysts prepared by all three methods have been characterized by electron microscopy (TEM and SEM) and by energy-dispersive X-ray (EDX) microanalysis, and those prepared by method 2 have been characterized by diffuse reflectance UV-vis spectroscopy as well.

Nanoengineering of Particle Surfaces

“…Dokoutchaev et al recently reported the alternating assembly of metal nano-sized particles and oppositely charged polyelectrolyte onto polystyrene microspheres. [64] In that work, [64] low gold nanoparticle coverage and non-uniform coatings were obtained, although the nanoparticle loading was increased by repeated depositions of nanoparticle and polyelectrolyte in the LbL manner. Using the same strategy, Caruso et al demonstrated the step-wise formation of regular nanoparticle layers on colloidal particles.…”

“…[80] Using a similar method, Dokoutchaev et al formed metal particles of 2±4 nm diameter on polystyrene microspheres by depositing a precursor metal (palladium) oxide or hydroxide onto the spheres, followed by reduction to give fine metal particles on the surface. [64] The synthesis of polymer-coated microspheres with silver colloids on their surface using free radical chemistry has also been reported. [81] The metal salt and organic monomers are mixed together in solution.…”

“…Sonication of PdCl 4 2± in aqueous solution leads to large Pd colloids that precipitate immediately, whereas conducting the sonication reaction in the presence of amine-functionalized polystyrene microspheres results in deposition of 8 nm Pd colloids on the particles. [64] The sonochemical approach is an attractive means for coating particles. It appears to be best suited for the modification of particle surfaces with nanoparticles, but not necessarily for forming regular coatings of these materials.…”

Advanced Core-Shell Composite Nanoparticles Through Pickering Emulsion Polymerization

“…Such materials provide a new class of supramolecular building blocks and can "exhibit unusual, possibly unique, properties which cannot be obtained simply by co-mixing polymer and inorganic particles." (Barthet et al, 1999) In comparison with the recently reported methods to synthesize core-shell composite particles, for example, post-surface-reactio (Ding et al, 2004;Lynch et al, 2005), electrostatic deposition (Dokoutchaev et al, 1999), and layer-by-layer self-assembly (Caruso, 2001;Caruso et al, 1999;Caruso et al, 2001), we synthesize core-shell composite nanoparticles through a novel Pickering emulsion polymerization route (Ma and Dai, 2009;Ma et al, 2010). Figure 1 illustrates the polymerization route and its comparison with the conventional emulsion polymerization.…”

Preparation of a functional nanofibrous polymer membrane incorporated with poly(2-aminothio phenol) stabilized gold nanoparticles

“…Research studies on metal nanoparticles (MNPs) are continuously increasing because of their unusual properties compared to bulk metals and potential applications in electrical, optical, magnetic, catalytic, and chemical/ biochemical sensing areas [12][13][14]. MNPs-based composites have been prepared through incorporation of them into silica or metal oxide surfaces [15], polymer micelles [16], and microspheres [17].…”