Using Block Copolymer Micellar Thin Films as Templates for the Production of Catalysts for Carbon Nanotube Growth

Abstract

We report a novel approach that uses block copolymer micelles as a means to create large area arrays of iron-containing nanoclusters capable of catalyzing the growth of carbon nanotubes (CNTs). The amphiphilic block copolymer poly(styrene-block-acrylic acid) (PS-b-PAA) forms micelles in solution which are capable of self-organizing into ordered structures on surfaces. By spin-coating these solutions onto a variety of substrates, we can create quasihexagonal arrays of PAA spheres within a PS matrix. The carboxylic acids groups in the PAA domains can be utilized in an ion-exchange protocol to selectively sequester iron ions, which results in iron-containing nanoclusters that are nearly monodisperse in size (diameter ∼8 nm) and patterned at a density of approximately 10 11 particles per cm 2 . In principle, this route for synthesizing iron-containing nanoclusters offers the capability of controlling the cluster size and spacing by altering the molecular weight of the block copolymer. In this report, we demonstrate the ability of these block-copolymer-templated iron-containing nanocluster arrays to catalyze the growth of CNTs in a thermal chemical vapor deposition (CVD) process. We present transmission electron microscope (TEM) and scanning electron microscope (SEM) images of the as-grown CNTs still attached to their growth substrate, which allows us to characterize both the CNTs and the catalytic nanoclusters after CVD growth.

Controlling the Morphology of Carbon Nanotube Films by Varying the Areal Density of Catalyst Nanoclusters Using Block‐Copolymer Micellar Thin Films

“…Preparation of Carbon Nanotube Growth Catalysts: Details about synthesizing iron oxide nanocluster arrays have been published previously [21,22,24]. In brief, PS-b-PAA was mixed with toluene at a concentration of 10 mg mL -1 and heated to 145°C for 20 min in a sealed vial to create a spherical block-copolymer micellar solution.…”

“…[21,22,24] The polymer thin film was then treated in oxygen plasma to remove the organic components, leaving an iron oxide nanocluster array, as shown in Figure 1A. Previous studies have demonstrated that the iron oxide nanocluster structure is Fe 2 O 3 .…”

Raspberry-like Pt clusters with controlled spacing produced by deposition of loaded block copolymer micelles from supercritical CO2

“…These periodic nanostructures can potentially be utilized as templates for creating metal nanostructures with controlled features, such as size or spacing. There are various reports describing the incorporation of inorganic functional components into microdomains of self-assembled block copolymer thin film structures or micelles [19,[23][24][25][26][27][28][29][30][31], proving it to be a promising tool for the preparation of nanostructured arrays with tunable spacing and size. Selective loading of BCP domains with metallic nanoparticles usually requires three conceptual steps: firstly, creating the BCP thin film or micelles on a substrate, secondly, impregnating selectively one domain of BCP with certain precursor, and, finally, formation of metal nanoparticles, which is sometimes followed by a separate step of BCP destruction.…”

Hierarchical positioning of gold nanoparticles into periodic arrays using block copolymer nanoring templates

“…A first well-known procedure for the production of metal NP arrays consists of using BCP micelles as reservoirs for the loading of metal salts, either in solution [18,19] or after the micellar film deposition [20][21][22]. Selective binding between metal salts and BCPs occurs via the formation of p complexes with olefin groups [23], electrostatic interactions [18,24] or metal coordination reactions [25] with a polar group, often nitrogen atoms of pyridine units.…”