Shape-directing role of cetyltrimethylammonium bromide in the green synthesis of Ag-nanoparticles using Neem (Azadirachta indica) leaf extract

The shape-directing role of cetyltrimethylammonium bromide, CTAB, is reported to the green synthesis of Ag-nanoparticles for the first time using Neem (Azadirachta indica) leaf extract. UV–vis spectroscopy, transmission electron microscopy (TEM), and selected area electron diffraction (SAED) patterns were used to monitor the growth kinetics, morphology and crystalline nature of Ag-nanoparticles, respectively. It was observed that the growths of Ag-nanoparticles are stopped within 40 min of reaction time. The Ag-nanoparticles are polydispersed spherical and exhibiting an interesting triangle, flat, plate-like hexagonal and some irregular morphology in presence of different [CTAB]. Hexagonal particles aggregated in a systematic manor, leads to produce a fine tiles-like arrangement of Ag-nanoparticles with dimensions between 10 and 37 nm. The nature of reaction–time curves to the reduction of Ag+ ions by Neem leaf extract are much different than those observed by us in our earlier studies using different bio-reductants.

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► Green biosynthetic procedure was used to the preparation of Ag-nanoparticles.
► Neem leaf extracts were acts as reducing, stabilizing and capping agent.
► Morphology of prepared Ag-nanoparticles strongly depends on the presence of CTAB which acts as a shape-directing agent.
► Pre-, post-micellar effects are responsible to the different morphology (quantum dots, spherical, polyhedral and hexagonal) of silver nanoparticles.