Department of Health Science and Clothing Environment, Faculty of Human Life and Environment, Nara Women's University, Nara 630-8506, Japan.
J Colloid Interface Sci. 2010 Mar 15;343(2):537-45. doi: 10.1016/j.jcis.2009.11.066. Epub 2009 Dec 4.
Silver particles (Ag particles) were synthesized by the photoreduction of silver perchlorate (AgClO(4)) in water-in-ionic liquid (IL) microemulsions consisting of nonionic surfactant Tween 20, water, and ionic liquids, [1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF(4)]) or 1-octyl-3-methylimidazolium tetrafluoroborate ([OMIm][BF(4)])], mixed with a high-pressure (25 MPa) CO(2). The time evolution of the Ag particle formation by photoreduction was investigated by UV-Vis, cryo-TEM, extended X-ray absorption fine structure (EXAFS), and small-angle X-ray scattering (SAXS) measurements. In the particle formation process, aggregation and precipitation of Ag particles were suppressed under high-pressure CO(2). The average diameters of the metallic Ag particles prepared in water-in-[BMIm][BF(4)] and water-in-[OMIm][BF(4)] microemulsions were estimated from TEM to be 3.2 and 3.7 nm, respectively. SAXS analysis shows that the average diameters of the water droplets, which consisted of ionic precursors of AgClO(4) and Ag particles (or Ag aggregates), were estimated to be about 30-40 nm. In the process of Ag particle formation, the water droplet size under high-pressure CO(2) is more effectively regulated than that under ambient air, thereby preventing Ag particles from aggregating and precipitating.
银颗粒（Ag 颗粒）是通过在水-离子液体（IL）微乳液中的银高氯酸盐（AgClO4）的光还原合成的，该微乳液由非离子表面活性剂 Tween 20、水和离子液体[1-丁基-3-甲基咪唑四氟硼酸盐（[BMIm][BF4]）或 1-辛基-3-甲基咪唑四氟硼酸盐（[OMIm][BF4]）]组成，与高压（25 MPa）CO2 混合。通过紫外可见光谱、低温透射电子显微镜、扩展 X 射线吸收精细结构（EXAFS）和小角 X 射线散射（SAXS）测量研究了光还原过程中 Ag 颗粒形成的时间演变。在颗粒形成过程中，在高压 CO2 下，Ag 颗粒的聚集和沉淀得到了抑制。在水包-[BMIm][BF4]和水包-[OMIm][BF4]微乳液中制备的金属 Ag 颗粒的平均直径通过 TEM 估计分别为 3.2nm 和 3.7nm。SAXS 分析表明，AgClO4 和 Ag 颗粒（或 Ag 聚集体）的离子前体组成的水滴的平均直径约为 30-40nm。在 Ag 颗粒形成过程中，高压 CO2 下的水滴尺寸比环境空气中更有效地调节，从而防止 Ag 颗粒聚集和沉淀。
