8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.174Wed 711:10-14:00Design for a micro-reaction field with binary electrosprayliquid-droplet beamsAkihiro Wakisaka, 1 Yutaka Hyoudou, 1 Hitomi Kobara, 1 Taizo Ono, 1 MasahiroTsuchiya, 2 and Kazuo Matsuura 31 National Institute of Advanced Industrial Science and technology, Onogawa 16-1,305-8569, Tsukuba, Japan2 National Defense Academy, Yokosuka, Japan3 Nanomist Technologies Co. , Ltd. , Naruto, JapanWhen a diffusion-controlled chemical reaction proceeds through the mixing of two solutions, themixing speed determines the reaction efficiency. For an extremely efficient mixing, here wewould like to report a novel electrospray method and its application to the synthesis of metalnano-particles. A liquid sample can be atomized to the charged liquid droplets according to theelectrospray phenomenon. We found that the positively and negatively charged fine liquid droplets,generated by two electrospray nozzles aligned face to face with a positive and a negative potential,merged at the center of the two nozzles by the electrostatic attractive force. This novel electrospraysystem can mix two solutions quite effectively. As its application to a chemical reaction, we examinedthe synthesis of polymer-stabilized gold nano-particles by the reduction of HAuCl 4 withascorbic acid. The ethanol solutions of HAuCl 4 (0. 1 mol/L) and ascorbic acid (0.1 mol/L) wereatomized by the electrospray with + 6 kV and − 4 kV, respectively. The resulting charged liquiddroplets collided to fuse efficiently, and the reduction of HAuCl 4 took place therein to produce thegold nano-particles. The fused droplets including the formed gold nano-particles were collectedinto an aqueous polymer solution (1-wt% PVP) by suction with an aspirator. The average diameterfor the gold particles was determined to be 2 3 nm by TEM and DLS analyses, which was in goodcontrast with the size (0.1 2 m m) produced by the conventional batch mixing. This demonstratesthat the micro mixing accomplished by the binary electrosprays works as a small vessel-less reactionfield to control the gold particle size. We anticipate that this novel method leads to theformation of the smallest possible reaction field in the liquid state, with the highest mixing speed.174