We investigate the influence of salt, acidic, and basic solutions (citrate, NaOH, and HCl) on the size of gold nanoparticles (AuNPs) synthesized by laser ablation in aqueous media. We found that NP size increases from 3 nm to 13 nm when Zeta potential varies from ？100 mV to ？10 mV whatever the concentration and the nature of chemical solution are namely, citrate, NaOH, and HCl. These results demonstrated that the final size of gold NPs produced by laser ablation in liquid media is mainly governed by the charge-dependent growth mechanism. 1. Introduction Pulsed laser ablation in liquid media (PLAL) has become an increasingly important alternative approach for synthesis of colloidal suspensions with novel functional properties [1, 2]. In particular, the fabrication of metallic nanoparticles (NPs) [2, 3], mostly gold and silver, has attracted much interest due to their surface plasmon resonance related properties that are potentially useful for their biological applications [4–7]. Numerous investigations have been performed in order to produce metallic NPs with controlled size and functional properties [8–11]. Variation of laser ablation parameters [9, 12] and chemical properties [13–16] of surrounding liquid media has been the primary focus of these studies. It has been demonstrated that the size of gold NPs produced in water increases with increasing laser pulse energy [17]. The variation in pH of various solutions influences not only the NP size [13, 18], but also the stability of gold colloids [19]. Despite numerous attempts to control the structural properties of gold NPs through synthesis parameters, a solid explanation of the influence of added chemicals on the size of gold NPs has not yet been proposed. In this work, we investigate the structural properties of gold NPs synthesized in three different solutions (citrate, NaOH, and HCl) in order to better understand the mechanism of NP growth during laser ablation in aqueous media. 2. Experimental Gold NPs were prepared by pulsed laser ablation of a solid gold target placed at the bottom of a glass beaker filled with 3？mL of water or various concentrations of hydrochloric acid (HCl), sodium hydroxide (NaOH), and sodium citrate. A nanosecond KrF excimer laser (wavelength: 248？nm, pulse duration: 17？ns, repetition rate: 20？Hz, laser fluence: 1？J/cm2) was focused on the gold target with a 7.5？cm lens (spot size: 0.1？cm2). Several seconds of ablation generally lead to a red coloration of the solution which indicates the formation of gold NPs. Red color corresponds to absorption at ~500？nm and is related
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