Role of Halide Ions and Temperature on the Morphology of Biologically Synthesized Gold Nanotriangles

Abstract

In this paper, we demonstrate the effect of halide ions on the formation of biogenically prepared gold nanotriangles using the leaf extract of lemongrass (Cymbopogon flexuosus) plant. We have also studied the effect of halide ions on the morphology of biogenic nanotriangles. It has been shown that iodide ions have a greater propensity to transform flat gold nanotriangles into circular disk-like structures as compared to other halide ions. The study also suggests that the presence of Cl- ions during the synthesis promotes the growth of nanotriangles, whereas the presence of I- ions distorts the nanotriangle morphology and induces the formation of aggregated spherical nanoparticles. The change in the morphology of gold nanotriangles has been explained in terms of the ability of the halide ions to stabilize or inhibit the formation of (111) faces to form [111] oriented gold nanotriangles. Last, we have also shown that the temperature is an important parameter for controlling the aspect ratio and the relative amounts of gold nanotriangles and spherical particles. The results show that, by varying the temperature of reaction condition, the shape, size, and optical properties of anisotropic nanoparticles can be fine-tuned.

Facile green synthesis of variable metallic gold nanoparticle using Padina gymnospora, a brown marine macroalga

“…2c) indicates that nanoparticles synthesized are well dispersed in solution. The increase in the reaction rate with the reaction temperature was also reported by Rai et al in case of gold nanotriangle synthesis using lemongrass extract (Rai et al 2006). …”

Synthesis of metal nanoparticles in living plants

“…The efficient and rapid extracellular synthesis of Ag, Cu and Au nanoparticles using broth extracts of several plants has been reported, such as Aloe vera (Chandran et al, 2006), Medicago sativa (Gardea-Torresday et al, 2002), Pelargonium graveolens (Shiv Shankar et al, 2003a, 2003b, Azadirachta indica (Shiv Shankar et al, 2004), Avena sativa (Armendariz et al, 2004a), wheat (Armendariz et al, 2004b), Tamarindus indica (Ankamwar et al, 2005a), lemongrass (Shiv Shankar et al, 2005), Emblica officinalis (Ankamwar et al, 2005b), Humulus lupulus (Rai et al, 2006), Spinacia oleracea and Lactuca sativa (Kanchana et al, 2011) and Capsicum annum (Jha and Prasad, 2011). For a more exhaustive list of plant species whose extracts have been used for metal nanoparticle production, refer to Narayanan and Sakthivel (2011).…”

Time dependent spectral change upon potential step perturbation for Au nanoparticles immobilized on an organic monolayer-modified ITO electrode

“…Recently, Rai and coworkers have demonstrated the effect of halide ions on the reshape of Au nanotriangles prepared using the leaf extract of lemongrass plant [25]. The purified triangles were One must be aware of the fact that the surface energy of the facet of metal nanoparticle is higher than that of bulk metal [28,29].…”