Solvent induced formation of an ordered nanorod array of gold/polymer composite by block copolymer film templating

Abstract

We report a novel method to fabricate ordered arrays of gold-polymer composite nanorods with the orientation in the vertical direction using block copolymer (BCP) film. The salt precursor is selectively infiltrated within vertically aligned cylindrical domains of the BCP film by immersing the template in a simple aqueous solution of HAuCl(4). Scanning electron microscopy suggests that the salt might be uniformly positioned along the polymeric cylinders. A subsequent vacuum ultraviolet light irradiation simultaneously reduces the HAuCl(4) into spherical gold nanoparticles with mean diameter around 2 nm and removes the matrix of the BCP template to produce metal-polymer composite nanorods. While the solvent is methanol, the salt might be concentrated at the bottom of the BCP film. As a result, a periodic pattern of gold nanoparticles with average diameter around 11 nm is formed where the BCP film is completely etched away. The solvent can effectively tune the spatial distribution of the salt precursor along the polymeric cylinders, which is responsible for the different morphologies of the photochemically fabricated nanostructures.

Chemically directed self-assembly of perpendicularly aligned cylinders by a liquid crystalline block copolymer

“…[30][31][32][33][34][35][38][39][40] Moreover, the developed pattern-transfer process can be applied to various metals and metal oxides, as we have reported before.…”

“…We tried to transfer the hexagonal PEO microdomains assembled on a chemically patterned template to an Au nanodot array by applying previously reported template method, 30,35,40 instead of the use of newly designed cleavable block copolymer to fabricate Au nanostructure previously. We tried to transfer the hexagonal PEO microdomains assembled on a chemically patterned template to an Au nanodot array by applying previously reported template method, 30,35,40 instead of the use of newly designed cleavable block copolymer to fabricate Au nanostructure previously.…”

“…We tried to transfer the hexagonal PEO microdomains assembled on a chemically patterned template to an Au nanodot array by applying previously reported template method, 30,35,40 instead of the use of newly designed cleavable block copolymer to fabricate Au nanostructure previously. 35,40 Note, in our process, PEO chains were not removed/etched from the cylindrical microdomains to create nanoholes to transfer the pattern to gold nanodots as in the case for most of the pattern transfer processes. The template method employs the PEO cylindrical microdomains assembled by PEO-b-PMA(Az) as nano-sized ion reactors, into which Au precursors are selectively penetrated and are reduced to form Au nanodots.…”

“…The total free energy of the system is given by the following equation. [30][31][32][33][34][35][36][37][38][39][40] Herein, we applied the chemical epitaxy method with a density multiplication process to DSA of PEO-b-PMA(Az) and obtained an orientation-controlled array of the PEO cylindrical microdomains, hexagonally in lateral and perpendicularly in axial directions, with periodicity below 10 nm half pitch. The hydrophilic PEO and hydrophobic PMA(Az) segments are highly segregated, and F LC further enhance the total segregation power between the segments.…”

Nanopatterning and micropatterning of cobalt containing block copolymers via phase‐separation and lithographic techniques

“…By incorporating transition metals into BCP self‐assemblies, nano‐scale metal containing morphologies such as micelles, vesicles, platelets, and rods in solution, and lamella, cylinders, spheres, and gyroids in the solid‐state were produced . These nanostructures were used as excellent precursors for the synthesis of well‐defined metal nanoparticles via thermal decomposition, radiation treatment, and reduction …”