Patchy particles

Similarly, Lan et al. [7] developed a one-step microfluidic method for fabricating nanoparticle-coated patchy particles. A coaxial microfluidic device was employed to produce Janus droplets composed of curable phase and non-curable phase. The results showed that nanoparticles were dispersed either in the continuous fluid or the non-curable phase fluid. The nanoparticles (30 nm or 300-500 nm) were adsorbed onto the interface between these phases, and the curable phase was solidified by UV-irradiated polymerization. Thus, the patchy microparticles asymmetrically coated by nanoparticles were synthesized. They also employed Si02, TS-1, and fluorescent polystyrene nanoparticles as the coating materials to demonstrate the validity of the method. The microfluidic approach exhibited excellent controllability in morphology, monodispersity, and size for the nanocomposites. The morphology of the particles could be controlled from less than a hemisphere to a sphere by adjusting the flow rate ratio of the two dispersed phases. The method can be applied to other nanoparticles with specific surface properties. 

Bianchi, E. et al. (2007). Fully Solvable Equihhrimn Self-assembly Process Fine-tuning the Clusters Size and the Connectivity in Patchy Particle Systems. Journal of jj i Ol liemistr, 111 (40), 11765-11769. 

Anisotropic particles, such as patchy, multicompartment, and Janus particles, have attracted significant attention in recent years because of their novel morphologies and diverse potential applications. The noncentrosymmetric features of these particles make them a unique class of nano-or microcolloidal materials. Patchy particles usually have different compositional patches in the corona, whereas multicompartment particles have a multiphasic anisotropic architecture in the core domain. In contrast, Janus particles, named after the double-faced Roman god, have a strictly biphasic geometry of distinct compositions and properties in the core and/or corona. This property of Janus particles allows for distinct shape, composition, chemistry, polarity, functionality, electrical, and properties, making them suitable for applications in switchable display devices, interface... 

Patchy particles are defined as particles with precisely controlled patches of varying surface and interaction properties. As schematically described in Figure 19,... 

Figure 19 Schematic representation of anisotropic particles (a) Janus particles, (b) multicompartment particles, (c) patchy particles, (d) patchy Janus particles, and (e) patchy multicompartment particles. (Reproduced from Ref. 45. Royal Society of Chemistry, 2011.)...

Janus particles have equal phase-separated domains which can be located either in the core or in the corona (if present), whereas multicomparOnent particles can be generally defined as a colloidal structures which are composed of multiple phase-separated domains in the core. Particles with patches on the surface are called patchy particles and have potential applications in electronics and targeted drug delivery. Furthermore, Janus or multicompartment particles with patches on the surface can be called patchy-Janus particles or patchy-multicompartment particles, respectively. 

Although many techniques such as conventional TEM (sometimes on selective staining), cryo-TEM, SEM, SAXS, and 2D NOESY NMR have been employed to reveal the exact structure of anisotropic particles such as Janus, multicompartment, and patchy particles, it is still difficult to fully determine the structure of the particle. Often, TEM is used to provide direct evidence for the formation of anisotropic particles. However, for samples with poor... 

Another interesting challenge remains in the area of describing the interactions. In the above studies, all interactions between particles and lipids were parameterized via their short-range potential. Moreover, particle surface chemistry was assumed to be uniform. It is possible to envision a variety of more interesting possibilities. One such possibility would include Janus or patchy particles, where the surface chemistry is nonuniform (there is a lateral phase separation into more hydrophobic and more hydrophilic areas). Very recently, Alexeev, Uspal and Balazs [75] used DPD simulations to study this problem, and some representative results of their... 

Pawar AB, Kretzschmar 1 (2010) Fabrication, assembly, and application of patchy particles. Macromol Rapid Commun 31(2) 150... 

Sdortino F, ZaccareQi E (2011) Reversible gels of patchy particles. Curr Opin Solid State Mat Sd 15 246... 

Field-induced assembly can be used for the assembly of patchy particles. Figure 17(a) shows chains of metallo-dielectric polymer latex spheres with a hemispherical coating of gold. In the presence of an AC electric field, the... 

Bao H, Peukert W, Taylor RK One-pot colloidal synthesis ofplasmonic patchy particles, Adp Mater 23 2644-2649, 2011. 

It should be noted that for polymerization-modified perlite the strength parameters of the composition algo go up with the increasing initial particle size. [164]. In some studies it has been shown that the filler modification effect on the mechanical properties of composites is maximum when only a portion of the filler surface is given the polymerophilic properties (cf., e.g. [166-168]). The reason lies in the specifics of the boundary layer formation in the polymer-filler systems and formation of a secondary filler network . In principle, the patchy polymerophilic behavior of the filler in relation to the matrix should also have place in the failing polymerization-modified perlite. 

Fig. 14. Different particles occurring in radiolarian ooze Black micronodules, patchy clay aggregates, glassy sharp dged fragment volcanic ash. (Clay aggregates can partly be formed as weathering products of volcanic ash or partly be new built).

Rather unusually Adams and Baker analysed the discharge from the mixer rather than the more conventional in situ analysis. Results are thus given in sequential form and despite the scatter rtf the individual samples it is possible to identify trends of segregation. Sample size is not quoted, but as only twenty-five or so black particles were counted in each sample it is likely that the sample is coarse grained and will reflect quite wide variations due to local patchiness of the black polythene component. 

In 1979, Santolicandro et al. confirmed and expanded the findings of Lin et al. (104). They reported a centrally oriented deposition pattern for 0.5-1.5 jnn Tc-labeled particles in patients with asthma In COPD patients, they found a patchy, nonuniform deposition pattern (106). 

The surface coagulation mechanism appears to be associated with at least partial de-wetting of the particle at the interface, either as a consequence of desotption of the stabilizing surfactant or as a consequence of a patchy surface with some of the patches being hydrophobic. FIFE particles, which have a low surface energy (c. 12 mN m ) and frequently a low concentration of charged... 

Along this line of using amphiphilic features of particles to drive assembly using a hydrophobic effect, there has been a recent surge of interest in the fabrication and behavior of anisotropic patchy or Janus-type colloidal particles as a promising route to innovative nanocomposite materials [40, 41]. Whereas a thorough review lies outside our scope, we would like to highlight a few examples. Muller and coworkers prepared disc-like polymer Janus particles from assem-... 

It should also be mentioned that a particular pre-treatment may be aUoy specific. For example, a relatively well-defined DC anodic oxide usually forms on a clad aluminium surface comprising a thin layer of co-extruded pure aluminium aUoy. In contrast, a more branched, less well defined and patchy anodic oxide will form in the same electrolyte on a 2xxx series alloy surface because of the presence of second phase Al-Cu particles, which do not have the same electrochemical potential as the matrix. 

Some controversy existed with respect to the exact structure of the iron particles in the alumina-promoted catalysts. In X-ray studies, the lattice constant was found to deviate slightly from that of pure a-Fe, an effect that was denoted as paracrystallinity and was attributed to elastic strain of the iron lattice caused by molecular epitaxy with hercynite during the catalyst activation (12). Careful re-investigation of the structural properties by X-ray diffraction and Mossbauer spectroscopy (13) revealed, however, the formation of high purity (bulk) a-Fe, and it was suggested that the effect of paracrystallinity might be reconciled with the presence of a patchy skin of alumina. Recent additional experiments including microstructural analysis of the formation of the active catalyst provided evidence... 

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