Characterization of metal nanoparticles prepared by photoreduction in aqueous solutions of various surfactants using UV–vis, EXAFS and SAXS

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 349; no. 1; pp. 176 - 188
• Main Authors: Harada, Masafumi, Saijo, Kenji, Sakamoto, Naoki
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 05.10.2009; Elsevier
• Subjects: Chemistry; Colloidal dispersions; Colloidal state and disperse state; Exact sciences and technology; EXAFS; General and physical chemistry; Gold particles; Micelles. Thin films; Photoreduction; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Platinum particles; SAXS; Surface physical chemistry; Surfactant-stabilized particles; Surfactant-stabilized particles; Gold particles; Colloidal dispersions; Photoreduction; EXAFS; Platinum particles; SAXS; Particle size; Shape; Growth; Nanoparticle; Cationic surfactant; Micelle; Surfactant; Small angle X ray scattering; Ionic surfactant; Characterization; Ethylene oxide polymer; Particle; Fine structure; Platinum; Gold; Ether; Non ionic surfactant; Transition metal; Hard sphere model; Colloidal dispersion; Metal particle; EXAFS spectrometry; Quaternary ammonium compound; Transmission electron microscopy; Aqueous solution; Aggregate; Formation mechanism; X ray absorption
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2009.08.015

Photoreduction formation mechanisms of metal particles (gold (Au) and platinum (Pt) particles) in aqueous surfactant solutions of dodecyltrimethylammonium chloride (DTAC) and polyethylene glycol lauryl ether (PEG) have been studied by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and extended X-ray absorption fine structure (EXAFS) measurements. EXAFS results confirmed the metallic nature of the nanoparticles, and showed that the average particle size significantly depends neither on the metal species nor on the charged properties (cationic, anionic, or nonionic) of surfactants. The SAXS analysis indicated that the structure of DTAC and PEG micelles could be fitted with the hard-sphere model having the interaction radius R HS and the spherically shaped core–shell structure. At the beginning of the photoirradiation, the increase of the SAXS intensity at q < 1.0 nm −1 was not due to the change of the size and shape of the produced metal particles, but due to the increase in number of produced metal particles in the growth process. Once the radius of metal particles produced during the photoirradiation exceeded a radius ( R shell) of the individual micelles, the metal particle growth was noticeably accelerated and the larger aggregates were formed, which were not stabilized by adsorbed surfactant molecules on their metal surface.