首页|Silica-based fibers with axially aligned mesopores from chitin self-assembly and sol-gel chemistry
Silica-based fibers with axially aligned mesopores from chitin self-assembly and sol-gel chemistry
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NSTL
Polysaccharide nanorods(chitin,cellulose)can be used as colloidal templates to form silica-based mesoporous materials by combining self-assembly and sol-gel chemistry.Chitin nanorods are chosen here for their self-assembly properties,facile preparation from natural resources,and because of the complexing properties of the free amino groups at their surface in view of further functionalization.Electrospinning of ethanolic co-suspensions,containing the chitin nanorods as pore templates,siloxane oligomers as silica precursors and polyvinylpyrrolidone(PVP)as spinning polymer,allows for forming mats of hybrid organic-inorganic fibers with diameters in the 200-300 nm range.The relative proportions of each component can be adjusted to meet specific characteristics(e.g.micro-/mesoporosity ratio).After calcination,the fibers present an open porosity studied by TEM and N2 volumetry.Elongated mesopores(100-200 nm long,2-4 nm wide)are created by individual chitin monocrystals forming the nanorods.They are highly oriented along the fibers'axes with orientational order parameters P2>0.95 for volume chitin contents(pchitin>0.2.Additional microporosity is provided by the removal of the spinning polymer,PVP.Complementary viscosity measurements on the initial co-suspensions allow discussing the interactions between colloids and their possible impact on the materials'textures observed.The introduction of a monomeric Ti~(4+)precursor in the co-suspensions leads to isolated and tetrahedral Ti units,distributed in the calcined porous silica fibers and possibly close to the pores surface.In addition,preliminary investigations on processing the fibers with a Zn xanthate as ZnS precursor leads to carbonized fibers with nanoparticles and a Zn/S molar ratio close to 1.
NSTL
