Designing sterically demanding thiolate coated AuNPs for electrical characterization of BPDT in a NP–molecule–nanoelectrode platform

Abstract

Molecular electronics with single or few molecules requires a stable metal–molecule nanojunction platform. Herein, we report the design and synthesis of gold nanoparticles coated with sterically demanding thiol ligands that are essential to fabricate a versatile and stable nanoelectrode–molecule–nanoparticle platform suitable for electrical characterization of small organic molecules. By combining ω-tetraphenylmethane ether functionalized alkyl thioacetate and alkyl thiols, we prepared highly stable gold nanoparticles in a one-phase reaction providing simple and efficient purification. This robust preparation gives highly pure nanoparticles in very high yields (up to 90%) with long-time shelf stability. The synthesis in this work has superior reproducibility compared to previous synthesis processes that are currently being used for such molecular electronics platforms. Electron microscopy confirms the formation of uniform and small nanoparticles in the range of 5 to 7 nm. These nanoparticles with different ligand surface coverages were placed in a 20 nm nanoelectrode setup using dielectrophoretic forces. This setup was utilized to characterize the conductivity of the molecular wire 4,4′-biphenyldithiol introduced via ligand place-exchange under ambient conditions.