Colloids and Surfaces A: Physicochem. Eng. Aspects 305 (2007) 54–57 A simple method to synthesize silver nanoparticles by photo-reduction Lilia Coronato Courrol a,* , Fl´ avia Rodrigues de Oliveira Silva b , La´ ercio Gomes c a Universidade Federal de S˜ ao Paulo, UNIFESP/Campus Diadema, Diadema, SP, Brazil b EPUSP, LSI, USP, S˜ ao Paulo, SP, Brazil c Centro de Lasers e Aplica¸ c˜ oes, IPEN/CNEN-SP, S˜ ao Paulo, SP, Brazil Received 29 January 2007; received in revised form 13 April 2007; accepted 18 April 2007 Available online 29 April 2007 Abstract In this work, a photo-induced method for obtaining silver nanoparticles (SNPs) was investigated using UV LED, xenon lamp and sodium lamp excitation. Silver colloidal solutions were prepared using autopolymerizable resin and AgNO 3 in an ethanol solution. This study shows that the combination of pulsed laser ablation in liquids with previous UV–visible illumination provides a simple, applicable and flexible technique for the fabrication of nanoparticles of 5–8 nm in size. © 2007 Elsevier B.V. All rights reserved. Keywords: Nanoparticles; Polymers; Laser; Spectroscopy; Silver nanoparticle; Photo-reduction 1. Introduction Silver nanoparticles (SNPs) show remarkable optical proper- ties that depend on their size and shape [1,2]. Metal nanoparticles can be used as optical biomarkers because they exhibit sig- nificant advantages over alternative markers. One of their key advantages is that unlike fluorophores, fluorescent proteins or even quantum dots, silver nanoparticles do not photode- compose during extended illumination. These properties make SNPs ideal for the spectral interrogation of various biological interactions [3–5] and allow their use as tags to indicate the location and environment of the target of interest. Therefore, nanoparticles can be used as a probe to continuously moni- tor dynamic events in living cells for weeks or months. One exciting application of metal biomarkers is the development of tools for cancer diagnostics. When gold or silver nanoparticles are conjugated to cancer antibodies, cancer cells are marked with those particles and every cell can be detected under a * Corresponding author. Present address: UNIFESP Campus Diadema, Rua Prof. Artur Riedel, 275, Cep 09972-270, Jd Eldorado-Diadema, Brazil. Tel.: +5511 95811307; fax: +5511 38169315. E-mail addresses: lcourrol@gmail.com, lcourrol@unifesp.br (L.C. Courrol). simple microscope due to their enhanced scattering properties [6]. A challenge in colloid chemistry is to control not only metal nanoparticle size but also particle shape and morphology [7]. Many techniques have been exploited in the preparation of shape-controlled silver nanoparticles. Polymers have been shown to be excellent hosts for trap- ping nanoparticles of metals and semiconductors [8] and also capable of acting as stabilizers or surface capping agents. When nanoparticles are embedded or encapsulated in a polymer, the polymer terminates the growth of the particles by controlling their nucleation. The photolysis process with nanosecond laser excitation in a silver colloidal solution has recently been used for the synthesis of nanoparticles. Kamat et al. [9] proposed that the photolysis process causes silver nanoparticles to lose electrons by photoe- jection, producing a transient state which precedes the complete fragmentation of the larger particles used in their work. Takami et al. [10] proposed that the reduction in the size of gold parti- cles observed after irradiation with nanoseconds Nd:YAG laser pulses is explained by particle heating, melting and vaporiza- tion. Mohanty et al. [11] proposed that laser irradiation causes silver nanoparticles to break down into smaller fragments which reassemble producing particles of new dimensions. Maillard 0927-7757/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2007.04.052