Colloids and Surfaces B: Biointerfaces 95 (2012) 229–234 Contents lists available at SciVerse ScienceDirect Colloids and Surfaces B: Biointerfaces jou rn al h om epage: www.elsevier.com/locate/colsurfb Shape-directing role of cetyltrimethylammonium bromide in the green synthesis of Ag-nanoparticles using Neem (Azadirachta indica) leaf extract Zaheer Khan ∗ , Javed Ijaz Hussain, Athar Adil Hashmi Nano-Science Research Lab, Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110025, India a r t i c l e i n f o Article history: Received 9 February 2012 Received in revised form 29 February 2012 Accepted 2 March 2012 Available online 13 March 2012 Keywords: Silver nanoparticles Green synthesis Neem leaf extract CTAB a b s t r a c t 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. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Researchers are showing much interest in “exotic” surfactant, polymers, and lipids molecules, especially dimeric (or “gemini”) and conventional surfactants due to their unusual physicochemical and shape-directing properties in the synthesis and characteriza- tion of advanced nano materials having different morphologies [1]. The morphologies and dynamics of aggregates formed by surfac- tant molecules (spherical micelles, rodlike micelles, bilayers, and reverse micelles) are known to influence strongly the performance properties spanning biology, chemical engineering, medicine and nanotechnology [2]. The literature is replete with the investiga- tions of the use of plants extracts [3], fungi [4], algae [5], proteins and enzymes [6] as the reductant for carrying out the synthe- ses of nanoparticles with a variety of shapes and morphologies in high yields, including multi-branched advanced silver and/or gold nanomaterials [7]; but the use of surfactant in the green synthesis of silver sol has been neglected. The stability, shape, size, and morphologies of metal nanoparticles strongly depend on the method of preparation, type, nature of reductants, and concentration of stabilizers (polymers, ligands, solid matrix and surfactants) [8]. Regarding the role of surfactants we have success- fully demonstrated that size, shape and the kinetics of surfactant stabilized silver nanoparticles by the reduction of Ag + ions with bio-reductants (ascorbic acid, cysteine, paracetamol, aspartic acid, ∗ Corresponding author. E-mail address: drkhanchem@yahoo.co.in (Z. Khan). glucose and tyrosine) largely depend on the [stabilizers], nature of reducing agents, and time of mixing of the reactants [9]. Nanotechnology is a broad interdisciplinary area of research, development and industrial activity which has been growing rapidly world wide for the past decade. Nanoparticles are useful as matrixes for the analyses of several types of biomolecules and for mass spectrometric imaging through surface-assisted laser desorp- tion/ionization mass spectrometry (SALDI–MS), mainly because of their large surface area, strong absorption in the ultraviolet–near- infrared region, and ready fictionalizations [10]. Most of the methods reported in literature are extremely expensive and they also involve the use of toxic, hazardous chemicals as the stabiliz- ers which may pose potential environmental and biological risks. Because of the increasing environmental concerns by chemical syn- thesis routes, an environmentally sustainable synthesis process has led to biomimetic approaches, which refers to applying biologi- cal principles in materials formation. Bio-reduction is one of the fundamental processes in the biomimetic synthesis. Sastry and his co-workers [3b] reported a process for the rapid synthesis of stable silver, gold, and their bimetallic nanoparticles at high concentration using Neem leaf broth and suggested that the flavanone and terpenoid constituents of the leaf broth are believed to be the surface active molecules stabilizing the nanoparticles. Using plants leaves extract for nanoparticle synthesis can be advan- tageous over other biological processes because it eliminates the elaborate process of maintaining cell cultures and can also be suit- ably scaled up for large-scale nanoparticle synthesis [11]. The rising demand for newer nano materials with improved and novel prop- erties has changed the emphasis to studies of surfactant–additive 0927-7765/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfb.2012.03.002