Colloid-templated nanoparticle

Figure 6.8 Illustration of colloid-templated nanoparticle assemblies. The process involves the layer-by-layer adsorption of charged polymers and oppositely charged nanoparticles onto the surfaces of the colloidal template. The colloidal core particles may then be removed to generate a hollow sphere of nanoparticles, held together by electrostatic interactions with the linear polymer glue ...

Particularly in 2D systems, control over the self-assembly of colloidal templates has offered a versatile way to produce patterned surfaces or arrays with a precision of few nanometres. Diblock copolymer micellar nanolithography (dBCML) is a versatile method that uses homopolymers or block copolymers for the production of complex surface structures with nanosized features [69], In contrast to other approaches like electron-beam lithography (EBL) and photolithography, dBCML does not require extensive equipment. In fact, it is commonly used in the fabrication of data storage devices and photonic crystals, in catalyses [70], and for the design of mesoporous films and nanoparticle arrays [71]. 

A similar process for preparing functional cyclodextrin nanospheres has been reported by the Harada group [25], )-Cyclodextrins were exhaustively thiolated at the lower rim and assembled around colloidal gold nanoparticles. Following assembly around the gold template the cyclodextrins were linked through the formation... 

Caruso, R. A. Susha, A. Caruso, F. Multilayered Titania, Silica, and Laponite Nanoparticle Coatings on Polystyrene Colloidal Templates and Resulting Inorganic Hollow Spheres. Chem. Mater. 2001,13,400-409. 

Armes et al. [49] have reported the use of pH-responsive microgels based solely on 2-(diethylamino)ethyl methacrylate (DEA) as colloidal templates for the in situ synthesis of Pt nanoparticles (PtNPs). The swollen microgels can be used as nanoreactors efficient impregnation with PtNPs can be achieved by incorporating precursor platinum compounds, followed by metal reduction. Addition of platinic acid, H2PtCl6, to the latex particles causes the protonation of the tertiary amine... 

Caruso, R.A., Susha, A. and Caruso, F., Multilayered titania, silica and laponite nanoparticle coatings on polystyrene colloidal templates and resulting inorganic hollow spheres, Chem. Mater. 13 (2001), pp. 400-409. 

Figure 6.8 Different examples of colloidal templating, or natural lithography, used to make SERS-active surfaces starting from uniform spherical colloidal particles, usually of polystyrene or silica. (NPs, nanoparticles RIE, reactive ion etching.)...

Jia, Y. et al., Macroporous ZrO, ceramics prepared from colloidally stable nanoparticles building blocks and organic templates, J. Colloid Interf. Sci., 291, 292. 2005. 

Ethayaraja, M., Dutta, K. Bandyopadhyaya, R. 2006 Mechanism of nanoparticle formation in self-assembled colloidal templates population balance model and Monte Carlo simulation. Journal of Physical Chemistry B 110, 16471-16481. 

In Fig. 6, we illustrate some different ways that the core-shell topology could be varied for silica and gold. So far we have considered the two normal core-shell structures. We now focus on the third example the assembly of Au Si02 nanoparticles onto spherical polystyrene latex colloids. The resulting spheres are also essentially different to continuous metal shells grown on colloid templates, which have been reported by Halas and colleagues [17] and by van Blaaderen and coworkers [18]. Such continuous shells display optical properties associated with resonances of the whole shell, and are therefore extremely sensitive to both core size and shell thickness, while in the system presented here... 

Infiltration with a second material (the matrix, e.g., an ultraviolet (UV) or thermally curable prepolymer [27,28], an ordinary organic precursor with initiators [29], a sol-gel precursor [30,31], or a dispersion of nanoparticles (1-50 nm) [32-34]) into the interstices of the colloidal template, followed by soHdification and the removal of colloidal template via dissolution, pyrolysis, or chemical etching. 

Codeposition of the colloidal template together with the matrix material, typically in the form of nanoparticles, while the colloidal particles form a highly ordered structure, which can be further processed to remove the sacrificial particle template [25,35]. 

Another recent development features the in situ formation of liquid colloidal templates. The assembly of NPs at the periphery of these templates is driven by electrostatics, resulting in the formation of robust NP-sheUed hoUow spheres, originally termed nanoparticle-assembled capsules (NACs). This scheme is called tandem assembly , nanoparticle-polymer tandem assembly , or polymer-aggregate tern-plating and presents an alternate, simple and non-destructive route for formation of NP-shelled hollow spheres [6,32-35,40,80,81]. 

Making use of constrained polymerisation of divinylbenzene on surfactant-modified colloid silica, Jang and Lim prepared carbon nanocapsules and mesocellular foams. Later, they reported that mesoporous carbons with highly uniform and tunable mesopores were fabricated by one-step vapour deposition polymerisation using colloidal silica nanoparticles as template and polyacrylonitrile as carbon precursor. Hampsey et al. recently reported the synthesis of spherical mesoporous carbons via an aerosol-based, one-step approach using colloidal silica particles and/or silicate clusters as template. ... 

FIGURE 2.33 Proposed mechanism for the formation of nanopores in carbon using a colloidal silica nanoparticle template. (From Pang, J., Hu, Q., Wu, Z., Hampsey, J.E., He, J., and Lu, Y. Micropor Mesopor Mater lA 73-78, 2004. With permission.)... 

LbL capsules are spherical compartments with walls formed by adsorption of alternating layers of positively and negatively charged polyelectrolytes [83]. Assembly of LbL capsules is achieved by consecutive deposition of complementary polymers onto colloidal particles (LbL deposition technique), followed by removal of the colloidal template by addition of acids [16,84-86]. CaC03 nanoparticles are commonly used as templates because they have low toxicity and are biodegradable. LbL capsules are an interesting platform for the design of nanoreactors because their permeability can be selectively modified... 

F. Caruso, M. Spasova, V. Salgueiriilo-Maceira, and L.M. Liz-Marzan, Multilayer assemblies of silica-enciqrsulated gold nanoparticles on decomposable colloid templates, Adv. Mater. 13,1090-1095 (2001). 

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