Carbon nanotubes (CNTs) exhibit exceptional electrical, optical, thermal, magnetic, and mechanical properties, making them promising materials for a wide range of applications. Among various configurations, the synthesis of vertically aligned CNTs is particularly valuable, however, their synthesis relies heavily on catalyst nanoparticles with well-defined size, composition and catalyst support films. Controlling these parameters remains a significant challenge, since the physical properties of CNTs such as specific chirality and diameter are typically determined by the catalyst. This talk will be about demonstrating a true bottom-up approach synthesis of vertically aligned CNTs using bimetallic oxide nanoparticles (biMO-NPs) where catalyst nanoparticles were synthesized in liquid phase without the need of expensive thin films deposition equipment.^[1] Iron based (FeAlOx) and cobalt based (CoAlOx) discrete nanoparticles with tunable geometries were synthesized in the liquid phase from aluminum, iron and cobalt oleate precursors respectively.^[2] These nanoparticles were assembled into monolayer films on silicon oxide (SiO₂) substrates using bifunctional organic linker molecules. The linker molecules, with terminal functional groups, enable controlled anchoring of the nanoparticle substrates, forming a uniform catalyst monolayer of particles with nanoscale thickness. This monolayer assembly approach ensures consistent particle distribution and avoids aggregation of nanoparticles, critical for the uniform growth of CNTs. biMO-NPs composed of FeAlOx and CoAlOx, assembled as monolayer films enabled the successful growth of long VA-CNTs, even on unmodified SiO₂ surfaces. Structural and chemical characterization confirmed the uniformity and composition of the bimetallic nanoparticles as well as the CNT characteristics. 

This study demonstrates that a bottom-up, fully wet-chemistry approach can achieve a high degree of control over the catalyst nanoparticles composition and spatial arrangement. The ability to synthesize and organize bimetallic nanoparticles into functional monolayers offers a simple, scalable, and cost-effective alternative to traditional physical vapor deposition methods for catalyst preparation. Moreover, this work highlights the potential for tuning CNT growth and moving closer to the rational synthesis of CNTs with specific physical properties, including chirality.