Colloidal arrays

Asher S A, Holtz J, Liu L and Wu Z 1994 Self-assembly motif for creating submicron periodic materials. Polymerized crystalline colloidal arrays J. Am. Chem. Soc. 116 4997-8... 

Bragg diffraction on crystalline colloidal arrays Photonic crystal material is composed of a crystalline colloidal array that diffracts light at wavelengths determined by the optical lattice spacing, which is affected by the presence of analyte 5,14,15... 

Asher, S. A., Crystalline colloidal array chemical sensing devices, In ACS PRF summer school on nanoparticle materials, June 6 18, 2004. Eastern Michigan University, Ypsilanti, MI, 2004... 

Using a glassy carbon electrode modified with a mercury film, Weber et al. [66] measured the association and dissociation rate constants for the complex formed between Pb + and the 18-crown-6 ether. It was found that Pb + forms a complex with 18-crown-6 with a stoichiometiy of 1 1 in both nitrate and perchlorate media. The formation constant, for the nitrate and perchlorate systems are (3.82 0.89) X 10 and (5.92 1.97) x lO mol Ls , respectively. The dissociation rate constants, are (2.83 0.66) x 10 with nitrate and (2.64 0.88) x 10 s with perchlorate as counter ion. In addition, the binding of Pb + with benzo-18-crown-6 embedded in a polymerized ciystalline colloidal array hydrogel has been also analyzed [67]. 

Pan G, Kesavamoorthy R, Asher SA. Nanosecond switchable polymerized crystalline colloidal array Bragg diffracting materials. Journal of the American Chemical Society 1998, 120, 6525-6530. 

Asher SA, Holtz JH. (1998) Polymerized crystalline colloidal array sensor methods, US5854078. 

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. 

Asher, S., Peteu, S., Reese, C. et al.. Polymerized crystalline colloidal array chemical-sensing materials for detection of lead in body fluids. Anal. Bioanal. Chem., 373, 632, 2002. 

Foulger, S., Lattam, A., Jiang, P. et al., Optical and mechanical properties of polyfethylene glycol) methacrylate hydrogel encapsulated crystalline colloidal arrays, Langmuir, 17, 6023, 2001. 

Selective electroless nickel plating of particle arrays on polyelectrolyte multilayer was investigated for the potential applications in sensors, optoelectronics, and biochips.96 This process is based on the preparation of functional colloidal arrays on surfaces. In the next step metal deposition is carried out on the surfaces of the patterned particles secured on the substrate. Samples of colloidal arrays on patterned polyelectrolyte templates are first pretreated with a Pd(II)-based catalyst. After rinsing with deionized water and drying, samples were plated with nickel using dimethylamine borane (DMAB) as a reducing agent. Based on the results of this work,96 it was shown that the selective electroless nickel deposition on 3D patterned surfaces can be successful. 

Recently reported techniques for lead determinations also include polymerized crystalline colloidal array (IPCCA) for the detection of Pb in high ionic-strength environments, such as body fluids (Asher etal. 2002). Flow injection (FI) analysis may be used to measure lead in environmental solid samples with spectroscopic detectors (Yebra-Biurrun and Moreno-Cid Barinaga 2002). Other techniques include ultra-fast high-performance liquid chroma-... 

FIGURE 54.9 Two mechanisms for flow-based assembly of colloidal arrays, (a) Assembly through a template weir. (Reprinted from Park, S.H., and Xia, Y., Chem. Mater., 10, 1745, 1998. With permission.) (b) Assembly through permeation-driven flow of water in PDMS. (Reprinted from Randall, G.C., and Doyle, P.S., Proc. Natl. Acad. Sci. USA, 102, 10813, 2005. With permission.)... 

While we have only focused here on applications for DNA electrophoresis, colloidal crystals have also been used as a stationary phase for separating hydrophobic dyes and proteins [40]. The arrays may prove especially interesting for electrophoretic protein separations, since the pore size provides a steric constraint, no pressure drop is required for transport through the small pores and the bead surfaces serve as a substrate for reversed-phase adsorption. These arrays thus offer a tunable variety of separation mechanisms. Indeed, proteins with similar hydrophobic groups, which cannot be separated by high performance liquid chromatography (HPLC) due to their similar adsorption properties, are rapidly separated by charge in colloidal arrays [40]. 

That the optical properties of such 2D/3D colloid arrays will depend on particle packing densities has been demonstrated by Dusemund et al., who measured the reflectivity of gold colloid films as a function of colloid volume fraction [47]. Although the films were not ordered they showed a clear shift in surface plasmon position with increasing particle volume fraction. The only compromise was that the volume fraction could not be directly determined on the samples from which spectra were taken, but had to be measured on separately prepared TEM grids. Several groups have found that clustered quantum dots exhibit red-shifted fluorescence, a question recently reviewed by Weller [48]. 

Yi DK, Seo E M, Kim D Y. 2002b. Fabrication of a mesoscale wire sintering of a polymer colloid arrayed inside a one dimensional groove pattern. Langmuir 18(13) 5321 5323. 

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

Porous Structure from in situ Colloidal Array 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. 

Rugge A, Ford WT, Tolbert SH. 2003. From a colloidal crystal to an inter connected colloidal arrays a mechanism for a spontaneous rearrangement. Langmuir 19 7852 7861. 

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