Catalytic reduction of 4-nitrophenol over Ag nanoparticles immobilized on Stachys lavandulifolia extract-modified multi walled carbon nanotubes

Abstract

In current research, a new green process for modifying multi walled carbon nanotubes (MWCNTs) using extract of Stachys lavandulifolia as both stabilizer/capper and reductant agent was reported. The adsorbed biopolymers of S. lavandulifolia extract on the surface of CNTs can cause more in situ reduction of silver ions to silver nanoparticles and stabilize them. The physicochemical and structure features of the synthesized nanohybrid were studied in detail using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), wavelength-dispersive X-ray spectroscopy (WDX), inductively coupled plasma (ICP) and X-ray photoelectron spectroscopy (XPS). The achieved outcomes indicated the uniform distribution of Ag nanoparticles on the modified CNTs surface. The resultant MWCNTs@S. lavandulifolia/Ag nanocatalyst shows a superior catalytic behavior towards the reduction of 4-nitrophenol at ambient temperature with a great rate constant. The increased catalytic performance found with synthesized nanocatalyst is attributed to the CNTs surface coated with biopolymers of S. lavandulifolia extract which stabilizes and attracts the aryl nitro substrates adjacent to the catalytic places which in turn facilitates reducing nitro groups. The catalyst can be retained and reapplied seven times with no decrease in its catalytic performance.