Microwave-Assisted Self-Organization of Colloidal Particles in Confining Aqueous Droplets

详细信息    查看全文

• 作者：Shin-Hyun Kim ; Su Yeon Lee ; Gi-Ra Yi ; David J. Pine ; Seung-Man Yang
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：August 23, 2006
• 年：2006
• 卷：128
• 期：33
• 页码：10897 - 10904
• 全文大小：1244K
• 年卷期：v.128,no.33(August 23, 2006)
• ISSN：1520-5126

文摘

Monodisperse aqueous emulsion droplets encapsulating colloidal particles were produced inthe oil phase, and controlled microwave irradiation of the aqueous drop phase created spherical colloidalcrystals by so-called evaporation-induced self-organization of the colloidal particles. Unlike usual colloidalcrystals, colloidal crystals in spherical symmetry (or photonic balls) possessed photonic band gaps for thenormal incident light independent of the position all over the spherical surface. While the consolidation ofcolloidal particles in emulsion droplets in an oven took several hours, the present microwave-assistedevaporation could reduce the time for complete evaporation to a few tens of minutes. Under the microwaveirradiation, the aqueous phase in emulsions was superheated selectively and the evaporation rate of watercould be controlled easily by adjusting the microwave intensity. The result showed that the packing qualityof colloidal crystals obtained by the microwave-assisted self-organization was good enough to show photonicband gap characteristics. The reflectance of our photonic balls responded precisely to any change in physicalproperties including the size of colloidal particles, refractive index mismatch, and angle of the incidentbeam. In particular, for polymeric particles, the photonic band gap could be tuned by the intensity ofmicrowave irradiation, and the reflection color was red-shifted with stronger microwave irradiation. Finally,for better photonic band gap properties, inverted photonic balls were prepared by using the spherical colloidalcrystals as sacrificial templates.