Materials Chemistry and Physics 130 (2011) 1195–1202 Contents lists available at SciVerse ScienceDirect Materials Chemistry and Physics j ourna l ho me pag e: www.elsevier.com/locate/matchemphys Biosynthesis of silver nanoparticles using leaves of Stevia rebaudiana M. Yilmaz a , H. Turkdemir b , M. Akif Kilic c , E. Bayram d , A. Cicek e,g , A. Mete f , B. Ulug g,∗ a Department of Metallurgy and Materials Engineering, Faculty of Engineering, Bartın University, Bartın, Turkey b Department of Chemistry, Faculty of Arts and Sciences, Uluda˘ g University, 16059 Görükle, Bursa, Turkey c Department of Biology, Faculty of Science, Akdeniz University, Campus 07058, Antalya, Turkey d Department of Chemistry, Faculty of Science, Akdeniz University, Campus 07058, Antalya, Turkey e Department of Physics, Faculty of Arts and Sciences, Mehmet Akif Ersoy University, 15100 Burdur, Turkey f Department of Chemistry, Faculty of Arts and Sciences, Inonu University, Malatya, Turkey g Department of Physics, Faculty of Science, Akdeniz University, Campus 07058, Antalya, Turkey a r t i c l e i n f o Article history: Received 1 April 2011 Received in revised form 18 August 2011 Accepted 27 August 2011 Keywords: Silver nanoparticles Stevia rebaudiana Ultraviolet–visible spectroscopy Fourier transform infrared spectroscopy Nuclear magnetic resonance a b s t r a c t The synthesis of silver nanoparticles employing a shadow-dried Stevia rebaudiana leaf extract in AgNO 3 solution is reported. Transmission electron microscopy and X-ray diffraction inspections indicate that nanoparticles are spherical and polydispersed with diameters ranging between 2 and 50 nm with a max- imum at 15 nm. Ultraviolet–visible spectra recorded against the reaction time confirms the reduction of silver nanoparticles indicating that the formation and the aggregation of nanoparticles take place shortly after the mixing, as they persist concurrently with characteristic times of 48.5 min and 454.5 min, respectively. Aggregation is found to be the dominant mechanism after the first 73 min. Proton nuclear magnetic resonance spectrum of the silver nanoparticles reveals the existence of aliphatic, alcoholic and olefinic CH 2 and CH 3 groups, as well as some aromatic compounds but no sign of aldehydes or carboxylic acids. Infrared absorption of the silver nanoparticles suggests that the capping reagents of silver and gold nanoparticles reduced in plant extracts/broths are of the same chemical composition of different ratios. Ketones are shown to play a somehow active role for the formation of nanoparticles in plant extracts/broths. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Among the vast number of physical, chemical and biological methods for the synthesis of nanoparticles, biological processes are preferred for economic and environmental concerns. Physi- cal methods such as vapor deposition, molecular beam epitaxy [1], chemical vapor deposition [2] etc., require expensive high technology and are neither suitable for mass production nor energy-efficient. Although they are relatively more affordable and suitable for mass production as well as allowing tight control over the particle size distribution in many ways, chemical methods [3] are not environment friendly. Biosynthesis of nanoparticles offers many advantages over the corresponding physical and chemical methods. Contrary to alternative physical and chemical methods employing toxic chem- icals which are unacceptable for medical applications, biological synthesis methods use bacteria [4–6], yeast [7], fungi [8–10] or plants [11–35] all of which already exist in natural recycling pro- cesses. Furthermore, overall material and energy consumptions in ∗ Corresponding author. Tel.: +90 242 310 22 72; fax: +90 242 227 89 11. E-mail address: bulug@akdeniz.edu.tr (B. Ulug). biological methods are extremely lower, offering a low-cost green alternative. In biological methods employing microorganisms, enzymes/proteins which are either already present in the envi- ronment as products of common microorganism activities or are force-secreted when they meet specific metal ions are reported to be responsible for intra- [5,6] or extracellular [4,7,9,10] nanoparti- cle production. Reduced metal ions by the enzymes/proteins yield highly stable intra- or extracellular nanoparticles [36]. The reduc- tion of metal ions by means of plant extracts is the least studied biological method although such ability of plants has been known for decades. In the use of plant extracts, metal ions are put into a soup of molecules characteristic of the particular plant, some of which reduce the metal ions yielding nanoparticles. In this respect, using plant extracts for the reduction of metal ions could be argued to be inefficient since many molecules might remain unreacted by the end. However, reduction rate of gold and silver ions by the plant leaf extracts is reported to be larger than that by fungi [8,9,11,12]. Many plants are known to uptake metal ions and reduce them to zero-valence atoms which then accumulate in their roots, stems, seeds and leaves. Certain plants are employed efficiently in decontaminating the soil polluted with heavy metal ions and radioisotopes [37,38]. Accumulation of metals in some plants, which are known as hyperaccumulators [37,39,40] could reach 0254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2011.08.068