Enhanced silver nanoparticle dispersion on nitrogen-, oxygen-functionalized carbon nanotubes synthesized by CVD

Abstract

This work investigates the surface decoration of nitrogen-doped carbon nanotubes (N-CNTs) and oxygen-functionalized multiwalled carbon nanotubes (O-N-CNTs) with silver nanoparticles (Ag-NPs). N-CNTs and O-N-CNTs were synthesized by chemical vapor deposition at 850 °C using different precursor systems. N-CNTs were obtained from benzylamine and ferrocene, whereas O-N-CNTs were synthesized from a benzylamine/isopropanol mixture with ferrocene, promoting the incorporation of oxygen-containing surface functionalities during growth. Ag nanoparticles were synthesized via chemical reduction and subsequently anchored to nanotube surfaces using a filtration-assisted deposition process. Electron microscopy revealed significant differences in nanoparticle distribution between the two CNT systems. O-N-CNTs promoted the formation of smaller, more homogeneously distributed Ag nanoparticles, with particle sizes mainly between 4 and 12 nm, whereas N-CNTs exhibited larger particles and localized aggregation. X-ray diffraction analysis confirmed the presence of crystalline face-centered cubic Ag, while Raman spectroscopy indicated that the graphitic structure of the nanotubes remained largely preserved after decoration. X-ray photoelectron spectroscopy analysis revealed that metallic Ag was the dominant chemical state in both decorated systems. However, O-N-CNTs-Ag exhibited broader oxygen-related environments together with additional oxidized Ag surface species, suggesting stronger interfacial interactions between Ag nanoparticles and oxygen-containing functional groups. The results demonstrate that oxygen functionalities generated directly during CVD growth provide effective anchoring sites for Ag nanoparticles without requiring aggressive post-synthesis acid treatments. The combination of homogeneous nanoparticle dispersion and the preservation of nanotube structure makes O-N-CNTs-Ag promising for applications in sensing, catalysis, electrochemical devices, and water treatment technologies.