Hollow templating methods

The template method is a general approach for preparing nanomaterials that entaU synthesis or deposition of the desired material within the cylindrical and monodisperse pores of a nanopore membrane or other solid [20-22]. Cylindrical nano-strucmres with monodisperse diameters and lengths are obtained, and depending on the membrane and synthetic method used, these may be solid nano wires or hollow nanombes. This method has been used to prepare nano wires and nanombes composed... 

We report here the synthesis of tailor-made hollow silica nano spheres containing ultrafme particles of Rh, Ir or Rh/Ir bimetals in their cavities by using a crystal template method in a reversed micelle system. The preparation of ultra fine particles in a reversed micelle system has received considerable... 

PREPARATION OF SILICON CARBIDE HOLLOW SPHERES BY A TEMPLATE METHOD... 

Preparation of Silicon Carbide Hollow Spheres by a Template Method... 

Hard-tcmplatc synthesis can provide micro- and nanocontainers with a controlled geometric shape. However, this approach requires complicated synthetic steps, including the dissolution of the template in corrosive media. Collapse of the hollow structure after template removal is also a critical problem. Therefore, the potential drawback of using hard templates forced scientists to search for more efficient and facile routes to prepare CPCs. Among these newly developed approaches, the soft-template method is considered a powerful tool as an alternative strategy to hard-template synthesis. 

Soft-template technique offers advantage of scalability [39]. In hard-template method, a porous membrane of inorganic or polymeric material serves as a rigid mold for chemical or electrochemical replication of stracture. This method provides an easy marmer for production of 1-D nanostractures, but with difficulties of scale up. Hard templates such as silica or carbon spheres are also ideal for synthesis of hollow strac-tures (11 Chen et al. 2003). Classical examples where the template enables the control of morphology of a-Fe Oj nanoparticles can be found in literature (Table 1). 

Hollow microsphere (diameter 360-1200 nm) of PANI-NSA has been fabricated using an emulsion template method at low temperature [284]. In this template method, the target material is precipitated or polymerized on the surface of the template, which results in a core-shell structure. On removing the template, hollow microsphere can be obtained. However, the removal of the template often affects the spherical structure, especially for hollow polymer microsphere. Therefore, they select the emulsion template method as the emulsion can be readily removed through dissolution or evaporation after polymerization. 

Kondo et al. reported a novel fabrication method of polymer nanotubes by combination of an alternate layer-by-layer (LbL) assembly of PLLA and PDLA and the siliea template method. Silica nanoparticles with a diameter of 300 nm were alternately immersed in aeetonitrile solutions of PLLA and PDLA at 50 °C. The immersion process was performed for 10 cycles to deposit 10 double layers of PLLA and PDLA. The resulting partieles were then treated with 2.3% aqueous hydrofluoric acid to remove the siliea core. The hollow eapsules have a spherical shape with a diameter of 320 nm and a shell thiekness of approximately 60 nm. Tubular assemblies with an average diameter of 300 nm and lengths of 2-5 pm are obtained by evaporating water at ambient temperature from a water dispersion of the hollow eapsules on a polyethylene terephthalate (PET) substrate. 

Y. Itoh, M. Matsusaki, T. Kida and M. Akashi, Preparation of Onion-like Biodegradable Hollow Nanocapsules by Silica Template Method, Chem. Lett., 33(12), 1552-1553 (2004). 

Han, J., Liu, Y. and Guo, R. (2009). Reactive Template Method to Synthesize Gold Nanoparticles with Controllable Size and Morphology Supported on Shells of Polymer Hollow Microspheres and Their Application for Aerobic Alcohol Oxidation in Water, Adv. Fund Mater., 19, pp.1112-1117. 

The hard template method is as effective as the soft template method in the synthesis of hollow silica spheres. PS particles are the most widely used template [21]. The general procedure involves two steps the formation of core-shell particles and the subsequent removal of the template, either by selective dissolution or by... 

To better control the ordering of mesopores in the silica shell, along with particle size and shape, the hard template method in combination with surfactant templating has been studied intensively. Typically, hollow particles with hexagonally ordered mesoporous shells can be obtained by using PS beads and CTAB in an aqueous ammonia solution. After the growth of a silica-surfactant meso-structured composite shell on the surfeice, the PS template is finally removed by calcination to form hollow spheres. Several reports have succeeded in... 

Fuji, M Shin, T., Watanabe, H., and Takei, T. (2012) Shape-controlled hollow silica nanoparticles synthesized by an inorganic particle template method. Adv. Powder TechnoL, 23, 562-565. 

We have already fabricated hollow silica-alumina composite spheres prepared by sol-gel based method using aqueous ammonia solution as a promoter of sol-gel reaction [4], and have revealed the influence of their nanostructure of the hollow spheres on their catalytic activity for hydrolysis of NH3BH3 [4], In the present study, we fabricated hollow silica-alumina composite spheres using PS template method and investigated their activity for hydrolytic dehydrogenation of ammonia borane. In addition, we firstly fabricated the hollow spheres using L(+)-arginine as the promoter for hydrolysis of tetraethoxysilane (TEOS) [16],... 

Hollow silica-alumina composite spheres were prepared by polystyrene (PS) template method as follows. The monodisperse PS particles were prepared by emulsifier-free emulsion polymerization [11], The content of PS particles with the diameter of ca. 200 - 300 nm could be tailored through the addition of ethyl alcohol. Then, 15.0 g of the PS template suspension and 6.75 mL of aqueous L(+)-arginine (0.2325 g, Kanto Chem. Co.) solution were added into 40 mL of ethyl alcohol, and then, 20 mL of aluminium(IV) iso-propoxide (AIP, 0.0057 g, Aldrich) / ethyl alcohol solution was added into the mixed solution, following the addition of 0.1551 mL of tetraethoxysilane (TEOS, Kanto Chem. Co., > 99.9 %). The sol-gel reaction was carried out at 323 K for 17 h, and as-prepared hollow silica-alumina composite spheres could be directly obtained. After drying in a desiccator overnight, the obtained fine powders were calcined at 873 K at heating rate = 0.5 K min ... 

Nanocapsules (hollow nanoparticles, nanospheres) are submicrometric colloidal objects composed of a liquid core surrounded by a thin silicone shell. The vesicle templating, solidification in emulsion and solidification of vesicles are the main methods for preparation of the silicone nanocapsules. The vesicle templating method is based on imprinting in the prepared materials the shape and size of the vesicles used as a template. Among the most popular templates are vesicles created from phospholipids (liposomes), double-tailed... 

Shi SJ, Lou ZR, Xia TF, Gu CD, Tu JP (2014) Hollow Li12Mno.5Coo.25Nio.05O2 microcube prepared by binary template method as a cathode material for lithium ion batteries. J Power Sourc 257 198-204... 

Another method to synthesize hollow nanocapsules involves the use of nanoparticle templates as the core, growing a shell around them, then subsequently removing the core by dissolution [30-32]. Although this approach is reminiscent of the sacrificial core method, the nanoparticles are first trapped and aligned in membrane pores by vacuum filtration rather than coated while in aqueous solution. The nanoparticles are employed as templates for polymer nucleation and growth Polymerization of a conducting polymer around the nanoparticles results in polymer-coated particles and, following dissolution of the core particles, hollow polymer nanocapsules are obtained. 

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