Cluster aggregation over spatiotemporal hierarchy; Complex fluids reconstruction to nano architecture

時空間階層を超えたクラスターの凝集; ナノアーキテクチャへの複雑流体の再構築

青柳 登   

Aoyagi, Noboru

Liquid-liquid phase transition is a significant phenomenon common across soft matters such as living cells, liquid crystals, colloidal particles, and, surprisingly, simple water. It sometimes results in intrinsic ordered structures when experiencing the phase separations in those materials; moreover, the liquid contains the condensed phase of multi-component complex fluids. The circumstances often let the non-equilibrium process being with two different ratios: a near-equilibrium reaction and a far-from-equilibrium reaction. Here, we report the real-time observation of the crystal growth and simultaneous nanocrystal aggregation that proceeds from ceric ammonium nitrate (CAN) toward nanoparticles of cerium dioxide in liquid water. Being exposed to strong acid, they become two or three ranges of size, which are different. Utilizing small-angle X- ray scattering (SAXS) for the bulk solutions and peculiar images taken by transmissive electron microscopy (TEM) compares the in-situ nature of the condensed fluids. Our results verified the formation of the hierarchically-assembled structure in solutions as a quasi-ceria colloid-comprised of both of the primary core clusters with 1-3 nm size and the secondary 20-30 nm colloids, in which they are patterning spherical aggregates and flocculation-agglomeration. The dissipation structure and the corresponding fluctuation might play a vital role in controlling this aggregation in order. The present observation expounds on the geometrical ensemble of polyoxometalates in the liquid state. The more massive assembly structure in a complex fluid is of cardinal significance in exploring the potential development of the nanoceria architectures. Our model case using nanoparticle and complex fluid is only one instance of many, regulating two different reactions under the principle of live-and-let-live across non-equilibria.