Chemical Engineering Journal 162 (2010) 852–858 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Nature factory of silver nanowires: Plant-mediated synthesis using broth of Cassia fistula leaf Liqin Lin a,b,c,d , Wenta Wang b,c,d , Jiale Huang b,c,d , Qingbiao Li a,b,c,d,∗ , Daohua Sun b , Xin Yang b,c,d , Huixuan Wang b,c,d , Ning He b , Yuanpeng Wang b a Environmental Science Research Center, College of Oceanography and Environmental Science, Xiamen University, Xiamen 361005, PR China b Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, PR China c National Engineering Laboratory for Green Chemical Productions of Alcohols, Ethers and Esters, Xiamen University, Xiamen 361005, PR China d Key Lab for Chemical Biology of Fujian Province, Xiamen University, Xiamen 361005, PR China article info Article history: Received 20 January 2010 Received in revised form 2 June 2010 Accepted 17 June 2010 Keywords: Green synthesis Nanowires Cassia fistula leaf Silver abstract In this paper, we demonstrated a green protocol in which silver nanowires with diameters in the range of 50–60 nm and lengths up to tens of micrometers were synthesized with extract of the Cassia fistula leaf as reductant and capping agent at room temperature. Different techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and UV–vis spec- troscopy were employed to characterize the nanowires. Particularly, TEM images recorded at intervals revealed that the resulting silver nanowires evolved from spherical nanoparticles via one-dimensional aggregation. The results also showed that reaction temperature played a crucial role in the formation of silver nanowires. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Morphology-controlled fabrication of nanostructures has become one of the most important and challenging aspects of modern nanotechnology due to their potential applications in optical, electronic and mechanical nanodevices. For instance, considerable effort has been made to develop new synthetic routes to one-dimensional metal nanostructures such as nanorods, nanowires and nanotubes in the last decade [1–4]. Silver nanowires (AgNWs) have attracted much attention owing to the unique elec- trical and thermal conductivities of bulk silver. Various methods have been successfully developed for the synthesis of AgNWs. Until now, the most widely used methods are solution-phase chemical approaches, which can be divided into templated and non-templated processes. Templated process involves hard and soft templates. Highly ordered materials including microchannels in alumina or polymer membranes [5,6], mesoporous materials [7–9], carbon nanotubes [10] and DNA [11,12] can be used as hard templates to direct the growth of nanowires. However, removal of ∗ Corresponding author at: Department of Chemical and Biochemical Engineer- ing, College of Chemistry and Chemical Engineering, Xiamen University, No. 422, Southern Siming Road, Xiamen 361005, PR China. Tel.: +86 0592 2189595; fax: +86 0592 2184822. E-mail address: kelqb@xmu.edu.cn (Q. Li). the rigid templates from the nanowires generally requires rigorous condition or complicated process, which consequently will limit the scale of production. Therefore, it is rational to develop the soft-template or non-template methods. Murphy and co-workers have synthesized AgNWs with uniform diameters in the pres- ence of silver seeds with cetyltrimethyl ammonium bromide (CTAB) served as soft template [13]. Xia’s group has synthesized AgNWs by reducing silver nitrate with ethylene glycol (EG), and polyvinylpyrrolidone (PVP) was introduced as structure-directing reagent rather than a soft template [14,15]. Although AgNWs can be well controlled through different methods mentioned above, they were synthesized either at high temperature or via synergetic action of several reagents. There is a growing need to develop environmentally benign alternatives to these existing methods. Biosynthesis of nanoparticles as an emerging highlight of nanobiotechnology has received increasing attention. To date, a variety of bacteria [16–23], fungi [24–26], and plants [27–36] have been demonstrated to produce metal nanopar- ticles with different morphologies. For example, single crystalline triangular gold nanoparticles could be modulated by plant extracts of Tamarind leaf, Aloe vera and lemongrass [32–34]. Our group showed that sundried Cinnamomum camphora leaf could be used to synthesize silver nanoparticles and gold triangular nanoparti- cles in aqueous solutions at ambient conditions [36]. And recently, He et al. reported the biosynthesis of gold nanowires using the cell free extract of Rhodopseudomonas capsulate [23]. However, 1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2010.06.023