Two‐Dimensional, Open‐Pored, Mesoscopic Titania Layers Using Polymeric Nanoparticle Monolayers as a Template

Abstract

example of a single material that can be used to construct an encoded library spanning such a broad wavelength range. ExperimentalSample Preparation: Porous silicon samples were prepared by anodically etching degenerate p-type, B-doped, (100)-oriented silicon with < 2 mX cm resistivity (Siltronix, inc.) in a solution of 48 % aqueous HF:ethanol (3:1 by volume). Freestanding films were ªlifted offº the substrate by application of a current pulse of approximately 10 mA cm ±2 for 2 min in an electrolyte solution comprised of 3 % HF (aq.) in ethanol. At this point the freestanding porous Si film is fractured into small particles by ultrasonication in ethanol for ca. 5 s, producing randomly shaped particles approximately 10 lm thick and 100±500 lm across [8,20].Spectral Measurements: Samples were illuminated with a tungsten lamp, and the reflected light spectrum was measured using an Ocean Optics S2000 CCD spectrometer. For spectral acquisition on particles the light source was focused to a 250 lm-diameter spot using a modified optical microscope and the reflected light was transmitted to the spectrometer using a cubic beam splitter.Polymer Coating: Porous Si±poly(norbornylene) composites were prepared using the following procedure: Into a glass vial was placed the freshly prepared porous Si particles and approx 0.25 mL of a 10 mM solution of tricyclohexylphosphine[1,3bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidine]ruthenium(IV) dichloride catalyst (Strem Chemicals) in dichloroethane. The flask was allowed to sit for 20 min. Excess catalyst was removed from the mixture by washing with 2 mL aliquots of methylene chloride until the supernatant solution was colorless. Polymerization was initiated by addition of 4.0 mL of a 10 mM solution of norbornylene (Aldrich, 99 %) in 1:9 dichloroethane/toluene to the catalyst-impregnated particles. The mixture was gently shaken for two hours at room temperature. The reaction solution was then decanted from the particles and replaced with fresh toluene. The suspension was then heated to 105 C for 15 h. The toluene was decanted off and the composite particles were washed three times with tetrahydrofuran, and then dried under a stream of dry dinitrogen gas. The coated materials were stored in a vacuum desiccator until use. Two-Dimensional, Open-Pored, Mesoscopic Titania Layers using Polymeric Nanoparticle Monolayers as a Template** By Yoon-Hee Cho, Gyoujin Cho, and Jae-Suk Lee*In the past few decades, considerable efforts have been made in the field of preparing inorganic materials such as TiO 2 , SiO 2 , and SnO 2 with ordered porosity for diverse applications in catalysis, medicine, and electronics.[1] With the increasing demand for these materials, relatively simple preparation methods based on the sol±gel process have mainly been pursued. The best-known routes for creating ordered porosity are emulsion templating and replication of three-dimensional (3D) latex arrays.[2] Xia et al. [1] and Pine and coworkers [2] have reported the successful preparation of 3D c...

Synthesis of Well‐defined Amphiphilic Block Copolymers by Organotellurium‐Mediated Living Radical Polymerization (TERP)

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