Synthesis of Vertically Aligned Carbon Nanotube Arrays from Premade Bimetallic Aluminum-Iron Oxide Nanoparticles Monolayer

Abstract

: Carbon Nanotubes (CNTs) are excellent materials because of their unique physical and chemical properties. Though catalyst nanoparticles preparation from thin film catalysts are common but premade catalysts nanoparticles in liquid phase has control over the size and composition which control the diameter and length of CNTs. Here, we report the synthesis of vertically aligned (VA) CNTs on metal oxide substrates including silicon oxide and stainless-steel using aluminum-iron oxides Al2O3-Fe2O3 nanoparticles monolayer. Oleic acid functionalized Al2O3-Fe2O3 nanoparticles were assembled onto metal oxide substrate as a monolayer using 11-phousnoundecanoic acid (PNDA) linker molecule where phosphonate group bind to the substrate and terminal carboxylic group of PNDA bind to the surface of bimetallic oxide catalysts. Homogenous catalyst nanoparticles distribution from monolayer assembly can reduce the aggregation of catalyst particles which can increases the catalyst lifetime during CNTs growth. Synthesis of VA-CNTs require Al2O3 catalyst support on substrate surface, but our bimetallic Al2O3-Fe2O3 nanoparticles contain both catalyst support (Al2O3) and catalyst (Fe) in the same particle. The successful VA-CNTs synthesis were achieved by chemical vapor deposition (CVD) process using acetylene as carbon precursor in atmospheric pressure. We envision that our catalyst preparation for VA-CNTs growth can be a cost-efficient method for large scale synthesis of CNTs. Further, the VA-CNTs growth on conductive stainless-steel substrate can facilitate the electrochemical application of this hybrid materials for biomolecule sensing and heavy metals detection.