Patent Application: US-201314912711-A

Abstract:
a process for producing polymer - supported metal nanoparticles involves confinement of metal nanoparticles in polymeric nanotubes or nanosheets in an aqueous environment using hydrophobic reactants . metal nanoparticles supported in the polymeric nanotubes or nanosheets are substantially monodisperse and have an average particle size of 4 nm or less . the polymer - supported metal nanoparticles are useful in fuel cells , sensors , bioanalysis , biological labeling or semi - conductors , especially as catalysts .

Description:
poly ( styrene - alt - maleic anhydride ) ( sma ) is an amphiphilic alternating copolymer that forms nanotubes with a 2 . 8 nm interior diameter in water at ph 7 . the most stable conformation obtained for the self - association at ph 7 is a tubular structure in which eight sma molecules make one twist of a helix . the tubes can grow in length by continued regular stacking of benzene rings . the nanotubes have inner and outer diameters of about 2 . 8 nm and 4 . 1 nm , respectively . the hydrophobic groups are mainly located inside the nanotube and the hydrophilic groups are mainly on the exterior surface of the nanotube . thus , sma nanotubes are capable of solubilizing hydrophobic compounds inside the nanotube , while themselves being solubilizable in aqueous media due to the hydrophilic groups on the exterior surface of the nanotube . poly ( isobutylene - alt - maleic anhydride ) ( ima ) is an amphiphilic alternating copolymer that forms nanosheets with a sheet spacing of about 2 nm in water at ph 7 . ima copolymer at ph 7 forms double layer sheets in which the outer surfaces are hydrophilic and the center gap is hydrophobic . thus , ima nanosheets are capable of solubilizing hydrophobic compounds in the center gap of the nanosheet , while themselves being solubilizable in aqueous media due to the hydrophilic groups on the exterior surface of the nanosheet . 1 wt % sma solutions were prepared by mixing poly ( styrene - alt - maleic anhydride ), partial methyl ester with an average mw = 350 ; 000 ( sigma - aldrich ), with deionized water . an aqueous solution of naoh was used to raise the ph to 7 and the mixture was sonicated until the polymer had completely dissolved . 0 . 1 g of platinum ( ii ) chloride , 98 % ( ptcl 2 , sigma - aldrich ) was weighed and mixed into 3 . 0 g of the 1 wt % sma solution . the mixture was then sonicated for 90 minutes at room temperature to break up aggregated ptcl 2 which would form when mixed into the solution . the sample was left to sit for 1 week until the colour of the solution start to change from a pale green to black with the formation of a precipitate . the precipitate is an excess of ptcl 2 used to ensure a complete solubilisation within the polymeric nanotemplate . this colour change was equivalent to the colour change observed when an identical ptcl 2 / sma solution was reduced with 1 ml of a 0 . 5 m nabh 4 solution , thereby confirming that reduction of the ptcl 2 can occur spontaneously in the interior of the sma nanotubes without the need for additional reducing agent . further confirmation that the platinum precursor compound ptcl 2 is reduced in situ in the sma nanotubes without the addition of additional reducing agent is evident from x - ray diffraction ( xrd ) ( fig1 ). the xrd spectra were obtained at a wavelength of 0 . 6888 å . peaks corresponding to the pt ( 111 ) crystal face at 17 . 49 ° and the ( 200 ) crystal face at 20 . 22 ° ( jcpds 04 - 0802 ) are evident in both the plot for the in situ reduction ( upper plot ) and the nabh 4 reduction ( lower plot ). this shows that pt nanoparticles are present in the sample where no nabh 4 reduction occurred , which can only be a result of spontaneous reduction of ptcl 2 in the sma nanotubes . particle size of the pt nanoparticles may be determined from transmission electron microscopy ( tem ). tem was performed at the canadian centre for electron microscopy on both the sample of pt - sma obtained from spontaneous in situ reduction ( fig2 a ) and the sample obtained from nabh 4 reduction ( fig2 b ). the dominant crystal face was determined from the tem images and the d - spacing determined . the average d - spacing for the pt nanoparticles in the nabh 4 reduced sample was 0 . 198 ± 0 . 007 nm , while the average d - spacing for the pt nanoparticles in the spontaneously reduced sample was 0 . 197 ± 0 . 007 nm . there is no significant difference between the two samples and they correspond to the ( 200 ) miller index . from the graphs in fig2 a and fig2 b showing the particle width distribution of the pt nanoparticles , it is evident that all of the particles have a width less than about 3 nm and that the average particle width is less than about 2 nm . both samples comprise nanoparticles having an average particle size of 1 . 89 ± 0 . 09 nm at the 95 % confidence level . with reference to fig3 a and fig3 b , enhanced catalytic activity of the pt - sma nanoreactor of example 1 was demonstrated by using uv - vis spectroscopy to monitor the polymerization of pyrrole within the polymeric nanotemplate . fig3 a and 3b demonstrate the efficiency of the pt catalyst inside the sma nanotemplate in aqueous solution at neutral ph . sma alone has previously been reported to spontaneously trigger the polymerization of pyrrole due to the confinement effect , but the reaction requires about 1 month to show any measureable change . the high surface - to - volume pt nanoparticles in the sma polymer nanotemplate were used to help catalyze the pyrrole polymerization under the confinement effect . it was found that with the presence of pt nanoparticles in the sma nanotubes , the polymerization of pyrrole requires only a third of the time to start to show a measurable change according to uv - vis spectroscopy . thus , the start of the characteristic polypyrrole peak occurs after only 8 days with the presence of the pt nanoparticles in 1 wt % sma . this peak does not appear for the 1 wt % sma sample without pt nanoparticles until 24 days after the start of the reaction . this demonstrates the additional catalytic activity of the sma nanoreactor with the inclusion of pt nanoparticles . the procedure described in example 1 was adapted to prepare au - sma nanoreactors , except that gold ( i ) chloride ( aucl ) replaced ptcl 2 as the precursor compound . fig4 is a uv - vis spectrum of gold nanoparticles prepared in this example , where the peak at 550 nm in the spectrum is characteristic of au nanoparticles . the contents of the entirety of each of which are incorporated by this reference . chan a s w , groves m , malardier - jugroot . 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( 2008 ) method for fabricating intrinsically conducting polymer nanorods . us 2008 / 0265219 published oct . 30 , 2008 . the novel features will become apparent to those of skill in the art upon examination of the description . it should be understood , however , that the scope of the claims should not be limited by the embodiments , but should be given the broadest interpretation consistent with the wording of the claims and the specification as a whole .