Fabricating Carbon Nanofiber Electrodes with Embedded Iron Nanoparticles Using Block Copolymers Templates

Abstract

Due to its high thermal, mechanical and electrochemical stability and good conductivity, carbon is an attractive material for fabrication of many bioelectrochemical devices such as biosensors and biofuel cells. However, carbon’s inert nature makes it difficult to functionalize with biocatalysts; often requiring harsh chemical treatment, such as nitric acid oxidation, to attach reactive amines and carboxylic acids to its surface. Alternatively, metal nanoparticles have been demonstrated to be efficient supports for biocatalysts functionalization. [1-3] Depositing metal nanoparticles on carbon electrodes by physical vapor deposition (PVD) is a viable means of functionalizing carbon electrodes with biocatalyst. However, PVD is an expensive and directional deposition method; this may result in poor surface coverage for 3D carbon electrodes, such as carbon nanofiber mesh electrodes. It has been traditionally difficult to incorporate nanoparticles into carbon nanofibers by embedding them into the polymer precursors prior to pyrolysis, as most metallic nanoparticles will melt at the temperatures needed for carbon pyrolysis (>900 oC). Recent studies, however, points toward a self-assembly approach for fabricating well organized layers of carbon loaded with arrays of platinum nanoparticles patterned by block-copolymers (BCP) templates. [4-6] Herein, we demonstrate an effective method for developing carbon nanofibers meshes embedded with iron nanoparticles, by incorporating a BCP self-assembly approach into our C-MEMS fabrication technique. The main phase of this hybrid method includes electrospinning iron-salt-loaded BCP into nanofiber meshes, and subsequently reducing the iron salts into iron nanoparticles prior to pyrolysis. This cost-effective process will pave the way for fabricating scalable advanced 3-D carbon electrodes that can be applied to biosensors and biofuel cells devices. [1] Zhao, Xin, et al. "Polymer-supported nanocomposites for environmental application: a review." Chemical Engineering Journal 170.2 (2011): 381-394. [2] Zayats, Maya, et al. "Biocatalytic growth of Au nanoparticles: from mechanistic aspects to biosensors design." Nano letters 5.1 (2005): 21-25. [3] Wilner, Ofer I., et al. "Self-assembly of enzymes on DNA scaffolds: en route to biocatalytic cascades and the synthesis of metallic nanowires." Nano letters 9.5 (2009): 2040-2043. [4] Park, Soojin, et al. "From nanorings to nanodots by patterning with block copolymers." Nano letters 8.6 (2008): 1667-1672. [5] Park, Soojin, et al. "Macroscopic 10-terabit–per–square-inch arrays from block copolymers with lateral order." Science 323.5917 (2009): 1030-1033. [6] Jang, Yu Jin, et al. "Nanostructured Metal/Carbon Hybrids for Electrocatalysis by Direct Carbonization of Inverse Micelle Multilayers." ACS nano 7.2 (2012): 1573-1582.