Porous Copper Nanowire Synthesis on CNT-DNA Thin Film Substrates

Biological hydrogels can serve as 3-dimensional bio-templates for tunable nano-porous materials that serve as both electrochemically active high surface area and structural material. We present a general approach to 1) form a composite biopolymer-carbon nanotube hydrogel using covalently crosslinked DNA-CNT, 2) equilibrate the hydrogel bio-template using Na₂PdCl₄ solution to mediate direct metal deposition, and 3) utilize an electroless copper deposition solution to form a porous copper nanowire array on the DNA-CNT substrate. Nanostructure is dependent on the biotemplate molecule, crosslinking mechanism, and drying method. Such multi-functional electro-mechanical materials are envisioned to enable a broad range of applications such as sensors, photovoltaics, catalytic systems, fuel cells, and energy absorption. Previous work allowed for the synthesis of metal aerogels and biotemplated metal films using a drop casting method where the gel was cast directly onto a substrate from a micropipette. The cast samples were then processed using three solutions to prepare and deposit metal directly onto the DNA-CNT substrate forming a biotemplated copper nanowire array. This method limited the bulk size of the cast sample to an approximate surface area of 1cm². To increase the overall surface area and volume of the nanowire arrays, we sought an alternate casting method. The new method cast heated DNA-CNT solutions into a parafilm mold on a glass microscope slide. This molded sample was then processed in a similar method to the drop cast samples. This method is preferable to a drop casting method as it will enable the future manufacturing of larger gels in terms of both surface area and volume. Nanostructured porous metals offer a wide range of applications including catalysis, energy storage and conversion, and sensing. The formation of free-standing metal aerogels with high specific surface area and hierarchical porosity confers significant advantages for conductivity, mass transfer properties, reaction specificity, and strength. This has previously been achieved with a direct reduction method,¹ as well as on gelatin,² and cellulose nanofiber templates.³ To further demonstrate multi-functional nanostructured electrodes, hierarchical DNA-CNT nano-composite aerogels will continue to be explored.