Hollow Nanostructures

The dendrite-like structures were made from highly porous hollow spheres. As the SnOEP became localized at the benzene-water interface, the platinum seeds formed during the photoreduction were able to grow in autocatalytic fashion and form Pt dendrites that eventually became nano foams [60]. 

---

Zhou H, Fan T, Zhang D, Guo Q, Ogawa H (2007) Novel bacteria-templated sonochemical route for the in situ one-step synthesis of ZnS hollow nanostructures. Chem Mater 19(9) 2144-2146... 

Mayers, B., Jiang, X., Sunderland, D., Cattle, B. Xia, Y. Hollow nanostructures of platinum with controllable dimensions can be synthesized by templating against selenium nanowires and colloids. 

P. Liu and L. Zhang, Hollow nanostructured polyanihne Preparation, properties and applications, Crit. Rev. Solid State Mater. Set, 34, 75-87 (2009). 

While the thermal oxidation of a compact metal surface is usually limited to the growth of an oxide layer with a thickness of a few of nanometers, bulk metal nanostmctures can be fully converted into the corresponding oxide or chalcogenide. Again the relative diffusion rate of metal atoms and the oxidation agent in the oxide determine the oxidation kinetics and structure formation. A topographic transformation to a metal oxide nanostructure is observed when the mobility of the oxidation agent exceeds the one of the metal atoms. When this is not the case, the so-called nanoscale Kirkendall effect (NKE) responsible for the formation of sophisticated hollow nanostructures, such as nanospheres, nanotubes, and nanopeapods, proceeds [2-5]. 

One very special type of shape control results in hollow nanoparticles of different geometries. In principle, the process is rather simple, in that a particle of any structure may serve as template that is coated by a layer of the desired metal. Subsequent removal of the inner template, either by calcination or by selective dissolution, will result in the formation of hollow nanostructures. Whilst this general technique can be applied to many types of material, one special application that involves only metals is as follows. In this case, silver nanocrystals of different shapes are coated by gold layers, via a simple chemical process based on the reductive power of elementary silver towards Au. ... 

The morphologies of magnetic multicomponent nanocrystals can be subdivided into several groups, namely core hdl nanoparticles, dumbbell nanopartkles, and the more recently discovered hollow nanostructures. The general approach towards the... 

Young CZ, Wang GL. Solvothermal synthesis of CdO hollow nanostructures from Cd02 nanoparticles. Mater Lett 2008 62(4/5) 673-7. 

Besides nanotubes, layered materials are able to build up other hollow nanostructures, such as fullerenes, nanoonions, or nanoseashells. For carbon, many of these systems have been synthesized experimentally. It is possible to construct theoretically and synthesize experimentally corresponding inorganic nanostructures. Prominent examples are inorganic multi-walled fullerenes built up from WS2, M0S2 or V2O5. These inorganic fullerenes are by now even synthesized in large quantities for applications as technical lubricants and have been studied experimentally and theoretically. 

In this chapter we have reviewed the latest contributions within the field of modelling inorganic nanotubes and inorganic fullerene-like structures. We have seen that many inorganic layered materials are able to form hollow nanostructures similar to systems formed by graphene and other forms of carbon. Most of the materials studied theoretically have been experimentally synthesized as well. Some of them are even produced in large amounts for industrial applications. 

Kirkendall Effect The Kirkendall effect is a phenomenon observed frequently in solid materials [38]. It refers to a vacancy counter diffusion process through an interface of two solid materials, metals in particular, to compensate the unequal material flow formation at the interface [38a]. In metals and metallic alloys, the vacancy is atomic defect, that is, empty lattice site. Combination of excess vacancies can lead to the formation of void within the fast-diffusion side of the interface [39]. While this phenomenon has been known for a very long time, synthesis of hollow nanostructures based on Kirkendall effect was realized fairly recently [40]. Ym studied the time evolution in the formation of hollow nanospheres and found that Kirkendall diffusion followed the Tick s law [41]. This means that the diffusion of atoms and vacancies is driven by the difference in atom concentration. Wu et al. synthesized hollow nanostructures of CoCuPt alloy catalyst by using Co nanoparticles as the sacrificial templates. For this trimetallic system, Co atoms diffused faster than those of Pt or Cu to form core-shell like Co CuPt hollow nanoparticles and then the CoCuPt hollow spheres (Fig. 2.10) [42]. 

Liu P, Zhang L (2009) Hollow nanostructured polyanUine preparation, properties and applications. Crit Rev Solid State... 

H. Zhou et al. [6] developed a novel bacteria-templated sonochemical route for the controllable assembly of ZnS nanoparticles into desired hollow nanostructures. It is based on artificial mineralization and cell disruption under ultrasound. Two shapes of bacteria cocci and bacillus were used as templates to direct the formation of corresponding ZnS hollow spheres and hollow nanotubes, respectively. The inorganic replicas retain the original morphologies of the templates faithfully. This bacteria-templated sonochemical method can be extended to the synthesis of various ZnS hollow assemblies by templating other shapes of bacterium such as vibrios, spirillum, square bacteria, etc. Meanwhile, this method is expected to be a generic means to the siiiple synthesis of hollow assemblies of various materials. 

Yang, Y., Wang, K.W., He, Q. and U, J.B. (2008) Controlled preparation of MnOj hierarchical hollow nanostructures and their application in water treatment. Advanced Materials, 20,452-6. 

Lou, X.W., Wang, Y Yuan, C Lee, J.Y., and Archer, L.A. (2006) Template-free synthesis of Sn02 hollow nanostructures with high lithium storage capacity. Adv. Mater., 18, 2325-2329. 

Wang, Z., Wang, Z.C., Madhavi, S., and Lou, X.W. (2012) One-step synthesis of Sn02 and Ti02 hollow nanostructures with various shapes and their enhanced lithium storage properties. Chem, Eur. /., 18, 7561-7567. 

J.Y. Kim, J.C. Park, H. Kang, H. Song, K.H. Park, CuO hollow nanostructures catalyze [3 + 2] cycloaddition of azides with terminal alkynes, Chem. Commtm. 46 (2010) 439-441. 

---