Swift catalytic reduction of hazardous pollutants by new generation microgels

In this manuscript, we report for the first time a new generation microgel synthesis without using any divinyl functionalized cross-linker. A new generation less crosslinked microgel structure has been achieved by optimizing the amount of N-hydroxy methyl acrylamide (NHMA) and using a fixed amount of styrene (St), acrylic acid (AA) and N-vinyl pyrrolidone (NVP) via a free radical emulsion solution polymerization technique. Poly(NHMA) works as a hydrophilic as well as a crosslinking agent. Furthermore, microgels have been upgraded into a composite by incorporation of Ag nanoparticles for catalytic reduction applications. Microgels and their composites have been characterized by EDAX, FT-IR, particle size analyzer, SEM, TEM, TGA, UV-vis spectroscopy and XRD. Methylene blue (MB) dye and p-nitrophenol (PNP) were chosen as model hazardous pollutants for catalytic reduction applications. Microgels efficiently adsorb both pollutants over the surface and microgel_Ag composites dramatically reduced both pollutants in the non-toxic form at room temperature by using smaller doses of NaBH₄.

Poly(ethylene glycol) microparticles produced by precipitation polymerization in aqueous solution

Methods were developed to perform precipitation photopolymerization of PEG-diacrylate. Previously, comonomers have been added to PEG when precipitation polymerization was desired. In the present method, the LCST of the PEG itself was lowered by the addition of the kosmotropic salt sodium sulfate to an aqueous solution. Typical of a precipitation polymerization, small microparticles or microspheres (1-5 μm) resulted with relatively low polydispersity. However, aggregate formation was often severe, presumably because of a lack of stabilization of the phase-separated colloids. Microparticles were also produced by copoymerization of PEG-diacrylate with acrylic acid or aminoethylmethacrylate. The comonomers affected the zeta potential of the formed microparticles but not the size. The carboxyl groups of acrylic-acid-containing PEG microparticles were activated, and scaffolds were formed by mixing with amine-containing PEG microparticles. Although the scaffolds were relatively weak, human hepatoma cells showed excellent viability when present during microparticle cross-linking.

Room-temperature preparation and characterization of poly (ethylene glycol)-coated silica nanoparticles for biomedical applications

Monodisperse, spherical, polyethylene glycol (PEG)-coated silica nanoparticles have been prepared at room temperature and characterized for the purpose of biomedical applications. The particles were synthesized by the hydrolysis of tetramethyl orthosilicate (TMOS) in alcohol media under catalysis by ammonia, and their size can range from about 50-350 nm in diameter. We studied the particle size and size distribution using a scanning electron microscope (SEM) and an asymmetric field-flow fractionation (AFFF) multiangle static light-scattering instrument. The chemical and/or physical binding of PEG to the silica nanoparticles was studied by infrared spectroscopy, and the weight percentage of PEG attached to the particles was quantified. The PEG-coated silica nanoparticles showed enhanced colloidal stability when redispersed into aqueous solutions from the dried state as a result of the steric stabilization function of the PEG polymer grafted on the surface of particles. A nonspecific protein-binding test was also carried out to show that the PEG coating can help reduce the protein adsorption onto the surface of the particles, relating to the biocompatibility of these PEG-coated particles. Also, the inclusion of magnetic nanoparticles into the silica particles was shown as an example of the possible applications of PEG-coated silica particles. These silica nanoparticles, as a matrix for encapsulation of certain reagents, have potential for applications to in vivo diagnosis, analysis, and measurements inside intact biologic systems.