Carbon nanotubes randomly decorated with gold clusters: from nano²hybrid atomic structures to gas sensing prototypes

TLDR

Carbon nanotube surfaces activated and decorated with metal nanoclusters are studied as prototypes for molecular recognition, with the key concept that shaping metallic clusters to donate or accept fractional charge upon adsorption alters electron transport. This study investigates carbon nanotubes decorated with gold clusters. The authors use first‑principles calculations to model gold atom binding, diffusion, and cluster structure on defect‑rich CNT surfaces, and experimentally decorate multi‑wall CNTs with gold via vacuum evaporation after RF oxygen plasma activation or colloid injection into RF atmospheric plasma, characterizing the hybrids with XPS and TEM. Simulations predict gold atom binding and diffusion energies on CNT surfaces and show that gold nanoclusters modify electronic transport, while sensor tests demonstrate that the nano‑hybrids detect NO₂, CO, C₂H₅OH, and C₂H₄.

Abstract

Carbon nanotube surfaces, activated and randomly decorated with metal nanoclusters, have been studied in uniquely combined theoretical and experimental approaches as prototypes for molecular recognition. The key concept is to shape metallic clusters that donate or accept a fractional charge upon adsorption of a target molecule, and modify the electron transport in the nanotube. The present work focuses on a simple system, carbon nanotubes with gold clusters. The nature of the gold–nanotube interaction is studied using first-principles techniques. The numerical simulations predict the binding and diffusion energies of gold atoms at the tube surface, including realistic atomic models for defects potentially present at the nanotube surface. The atomic structure of the gold nanoclusters and their effect on the intrinsic electronic quantum transport properties of the nanotube are also predicted. Experimentally, multi-wall CNTs are decorated with gold clusters using (1) vacuum evaporation, after activation with an RF oxygen plasma and (2) colloid solution injected into an RF atmospheric plasma; the hybrid systems are accurately characterized using XPS and TEM techniques. The response of gas sensors based on these nano2hybrids is quantified for the detection of toxic species like NO2, CO, C2H5OH and C2H4.