Colloidal array structure

Porous Structure from in situ Colloidal Array Structure Inversion... 

The opals obtained by self-assembly are mechanically unstable because there is only Van der Waals force between spheres. The subsequent infiltration process could easily destroy the ordered colloid arrays. So we annealed the opals of polymer sphere to increase their stability. As a result, there would form interconnections between spheres, which come from the slight melting of the sphere surfoces. These necks can provide the opal with necessary mechanical stability. In addition, they are important for producing inverse opal structure. After infiltration, when the samples are treated with calcinations, these necks can act as channels for the transport of the products formed during calcination like CO2. 

PHOTORESPONSIVE 2-D COLLOIDAL ARRAY AND ITS IN SITU STRUCTURE INVERSION... 

As discussed in Section 5.3, the colloids of the amphiphilic polydispersed azo polymers possess a hydrophobic core and hydrophilic corona. It is interesting to observe that polar organic solvents such as THF can also induce in situ structure inversion of the colloidal array of the azo homopolymer (Li et al., 2006c). Porous structures with pore sizes in submicrometer scale can be directly obtained from the colloidal arrays of BP-AZ-CA through the structure inversion. Moreover, by exploiting the photoresponsive properties of BP-AZ-CA, films with ordered elliptical pores can be feasibly prepared from the colloidal arrays of the ellipsoidal colloids obtained after the laser light irradiation. 

As discussed earlier, the porous structures and the colloidal arrays are composed of the same polymer indicated by spectroscopic analysis. This confirms that the porous films are formed through a solvent-induced in situ structure... 

Li YB, Tong XL, He YN, Wang XG. 2006c. Formation of ordered mesoporous films from in situ structure inversion of azo polymer colloidal arrays. J Am Chem Soc 128 2220 2221. 

In Figure 28, we show explicitly that initially perfectly mixed particles spontaneously create various micellar structures. Depending on the ratio x of the depths of the potential wells Ssoivent-solvent and esoivent-coiioidt we Can observe the emergence of lamellar, hydrophobic the hydrophilic colloidal arrays or coexistence of the two phases (Figure 26.28a). For other physical... 

FIGURE 26.28 (a) Micellar structures obtained by using MD-DPD simulations (above) and (below) comparison of the microstrucmres obtained from simulations (1) to real colloidal arrays (2). (b) The colloidal agglomerates simulated in increasing spatial scales. 

Reflection Periodic structures AZ, Cholesteric liquid crystalline polymers Crystalline colloidal arrays embedded in a gel network Gels... 

Ordered particle packings are also being used in other sensor type applications. Asher et al. ° described a system, where colloidal arrays of polymer particles were embedded in a gel-matrix. Changes in the environment of the particles caused the structures to shrink or expand, which could then be measured through the changes in the optical properties, as exemplified in Fig. 4. The same general idea can be applied to silica particles. This way, very specific sensors could be created when combined with appropriate surface modifications of the silica particles. The latter could be attached to the end of optical fibers or produced as a multisensor array on a chip. 

Mono-molecular surface layers exhibit strong effects in small colloidal particles. In the visible region even sub-monomolecular ad-layer of sulfides, iodides, oxides or borates lead to a significant modification of the plasmon resonance [9] (Figure 9). Ordered arrays of metal-columns deposited on, imprinted in or etched out of a substrate surface allow the excitation of extended plasmons similar to colloid arrays. Sharp tip structures allow high local fields and thus enable efficient energy transfer applied e.g. in surface enhanced Raman scattering (SERS). 

Ordered Array Structure of Polymer Colloidal Particles on a Patterned Substrate. 174... 

Figure 3.88 Reflectance spectra of the (a) 400 nm polystyrene colloidal array, (b) Ti02 nanoparticle-infiltrated polystyrene colloidal array and (c) liquid-electrolyte-infiltrated Ti02 inverse opal structure. Adapted from Kwak et al., 2009 Copyright (2009) Wiley-VCH Verlag GmbH c Co. KGaA...

A solid emulsion is a suspension of a liquid or solid phase in a solid. For example, opals are solid emulsions formed when partly hydrated silica fills the interstices between close-packed microspheres of silica aggregates. Gelatin desserts are a type of solid emulsion called a gel, which is soft but holds its shape. Photographic emulsions are gels that also contain solid colloidal particles of light-sensitive materials such as silver bromide. Many liquid crystalline arrays can be considered colloids. Cell membranes form a two-dimensional colloidal structure (Fig. 8.44). 

In 1997, a Chinese research group [78] used the colloidal solution of 70-nm-sized carboxylated latex particles as a subphase and spread mixtures of cationic and other surfactants at the air-solution interface. If the pH was sufficiently low (1.5-3.0), the electrostatic interaction between the polar headgroups of the monolayer and the surface groups of the latex particles was strong enough to attract the latex to the surface. A fairly densely packed array of particles could be obtained if a 2 1 mixture of octadecylamine and stearic acid was spread at the interface. The particle films could be transferred onto solid substrates using the LB technique. The structure was studied using transmission electron microscopy. 

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