Biosynthesis of silver fine particles and particles decorated with nanoparticles using the extract of Illicium verum (star anise) seeds Carlos Luna a,⇑ , V.H.G. Chávez a , Enrique Díaz Barriga-Castro a , Nuria O. Núñez b , Raquel Mendoza-Reséndez c a Centro de Investigación en Ciencias Físico Matemáticas/Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Nuevo León, Av. Universidad S/N, San Nicolás de los Garza, 66450 Nuevo León, Mexico b Instituto de Ciencia de Materiales de Sevilla, CSIC-US, Avda. Americo Vespucio n° 49, Isla de la Cartuja, 41092 Sevilla, Spain c Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, Av. Universidad S/N, San Nicolás de los Garza, 66450 Nuevo León, Mexico highlights  Silver nanoparticles (NPs) have been prepared using extracts of Illicium verum seeds.  The NPs arrangement was varied from a random distribution to big NPs coated with small NPs.  The microstructural and spectroscopic properties of these NPs arrangements were investigated.  A particle formation mechanism has been proposed associated to the studied biosynthesis. graphical abstract article info Article history: Received 10 September 2014 Received in revised form 24 November 2014 Accepted 17 December 2014 Available online 8 January 2015 Keywords: Biosynthesis Silver nanoparticles Illicium verum SERS Plasmons abstract Given the upsurge of new technologies based on nanomaterials, the development of sustainable methods to obtain functional nanostructures has become an imperative task. In this matter, several recent researches have shown that the biodegradable natural antioxidants of several plant extracts can be used simultaneously as reducing and stabilizing agents in the wet chemical synthesis of metallic nanoparti- cles, opening new opportunities to design greener synthesis. However, the challenge of these new tech- niques is to produce stable colloidal nanoparticles with controlled particle uniformity, size, shape and aggregation state, in similar manner than the well-established synthetic methods. In the present work, colloidal metallic silver nanoparticles have been synthesized using silver nitrate and extracts of Illicium verum (star anise) seeds at room temperature in a facile one-step procedure. The resulting products were colloidal suspensions of two populations of silver nanoparticles, one of them with particle sizes of few nanometers and the other with particles of tens of nm. Strikingly, the variation of the AgNO 3 /extract weight ratio in the reaction medium yielded to the variation of the spatial distribution of the nanoparti- cles: high AgNO 3 /extract concentration ratios yielded to randomly dispersed particles, whereas for lower AgNO 3 /extract ratios, the biggest particles appeared coated with the finest nanoparticles. This biosynthe- sized colloidal system, with controlled particle aggregation states, presents plasmonic and SERS proper- ties with potential applications in molecular sensors and nanophotonic devices. Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2014.12.076 1386-1425/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: carlos.lunacd@uanl.edu.mx (C. Luna). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 141 (2015) 43–50 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa