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Publications (3)17.18 Total impact

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    ABSTRACT: Real-time monitoring of the whole growth process of evaporation-induced colloidal self-assembly has been conducted using an optical microspectroscopy setup. Our observations suggest that the assembly process can be divided into three different growth stages as evidenced by the variations detected in the reflectance spectra. The thickness variation of the growing colloidal crystal was monitored by examining the Fabry-Perot fringes in the reflectance spectra. Furthermore, the scalar wave approximation was utilized to analyze the evolution of optical properties with growth. More detailed information, including the time dependence of number of layers and volume fraction of water, has been revealed by comparing the experimental and calculated reflectance spectra. The present work demonstrates that in situ real-time microspectroscopy is a promising technique for monitoring and investigating the dynamic process of colloidal self-assembly.
    Physical Review E 09/2011; 84(3 Pt 1):031605. · 2.31 Impact Factor
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    ABSTRACT: In situ observations of evaporation-induced colloidal self-assembly and in situ measurement of mass transfer process were carried out under a temperature and pressure controlling system. The growth processes of colloidal crystals in different cuvettes recorded by direct video observations revealed that solvent flow around the pore space of the crystal played a key role. By changing the circumstances (temperature and pressure) of the self-assembly system and properties of fluid (viscosity), different evaporation rate of solvent and growth rate of colloidal crystals were measured directly. It turned out that both evaporation rate and growth rate as functions of temperature and pressure fit Stefan's law well. Furthermore, the transfer process of particles in the fluid flow was determined by the fluid-dynamic characteristics, which can be analyzed by the Reynolds number. The results obtained provide an insight into the growth mechanisms of self-assembly and theoretical basis for optimizing the experimental growth conditions of colloidal crystals.
    Langmuir 03/2011; 27(5):1700-6. · 4.19 Impact Factor
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    ABSTRACT: In this paper, cooperative self-assembly (CSA) of colloidal spheres with different sizes was studied. It was found that a complicated jamming effect makes it difficult to achieve an optimal self-assembling condition for construction of a well-ordered stacking of colloidal spheres in a relatively short growth time by CSA. Through the use of a characteristic infrared (IR) technique to significantly accelerate local evaporation on the growing interface without changing the bulk growing environment, a concise three-parameter (temperature, pressure, and IR intensity) CSA method to effectively overcome the jamming effect has been developed. Mono- and multiscale inverse opals in a large range of lattice scales can be prepared within a growth time (15-30 min) that is remarkably shorter than the growth times of several hours for previous methods. Scanning electron microscopy images and transmittance spectra demonstrated the superior crystalline and optical qualities of the resulting materials. More importantly, the new method enables optimal conditions for CSA without limitations on sizes and materials of multiple colloids. This strategy not only makes a meaningful advance in the applicability and universality of colloidal crystals and ordered porous materials but also can be an inspiration to the self-assembly systems widely used in many other fields, such as nanotechnology and molecular bioengineering.
    Journal of the American Chemical Society 08/2008; 130(30):9785-9. · 10.68 Impact Factor