Synthesis of Gold Nanotriangles and Silver Nanoparticles Using Aloe vera Plant Extract

TLDR

Gold nanotriangles and silver nanoparticles were synthesized biogenically by reducing metal ions with Aloe vera leaf extract, with growth monitored by UV‑vis‑NIR spectroscopy and TEM, and the influence of extract concentration on yield and size examined. The method allows size‑controlled gold nanotriangles whose longitudinal surface plasmon resonance can be tuned, with multiply twinned particles and a slow, extract‑directed growth rate yielding single‑crystalline shapes, while silver ions are reduced to ~15 nm spherical nanoparticles.

Abstract

Biogenic gold nanotriangles and spherical silver nanoparticles were synthesized by a simple procedure using Aloe veraleaf extract as the reducing agent. This procedure offers control over the size of the gold nanotriangle and thereby a handle to tune their optical properties, particularly the position of the longitudinal surface plasmon resonance. The kinetics of gold nanotriangle formation was followed by UV-vis-NIR absorption spectroscopy and transmission electron microscopy (TEM). The effect of reducing agent concentration in the reaction mixture on the yield and size of the gold nanotriangles was studied using transmission electron microscopy. Monitoring the formation of gold nanotriangles as a function of time using TEM reveals that multiply twinned particles (MTPs) play an important role in the formation of gold nanotriangles. It is observed that the slow rate of the reaction along with the shape directing effect of the constituents of the extract are responsible for the formation of single crystalline gold nanotriangles. Reduction of silver ions by Aloe veraextract however, led to the formation of spherical silver nanoparticles of 15.2 nm ± 4.2 nm size.