Nanostructures in Separation

In addition to SWNT, several other novel forms of carbon nanostructures have received much attention in recent years and hold great promise to find interesting and important applications among them, we can mention double- and multiwalled nanotubes, graphene ribbons, and nanohoms. At the same time, researchers have recently developed methods of producing nanotubes in a variety of arrangements. Due to the potentially different properties and applications of these arrangements (vertical forests, parallel arrays, yarns, ribbons, etc.) they are treated in separate sections. 

Nanostructured adsorbents could play an important role in sample concentrators. The high surface are of nanostructures would provide ample opportunity for improved adsorption. Equally important, properly designed porosity could minimize the transport time intervals of desorbed entities. Nanostructures have been demonstrated to penetrate a highly concentrated plug of a sample agent in a short time span. Nanoscale porosity might also play a role in separation processes in sensor systems. 

Morikawa Y, Kondo T, Nagano S, Seki T. 2007. 3D Photoalignment and patterning of microphase separated nanostructure in polystyrene based block copol3uner. Chem Mater 19 1540 1542. 

Azo BCs are one fascinating class of soft materials, showing a rich variety of microphase-separated nanostructures in films because the strongly bonded azo segments and the non-azo blocks are thermodynamically incompatible. As shown in Fig. 12.1, the microphase-separated morphologies can be controlled to be spheres, cylinders, or lamellae, depending on the length, chemical nature, architecture, and number of repeated units in each block (e.g., Thomas and Lescanec, 1994). 

Figure 12.17. Magnetically induced alignment of microphase-separated nanostructures in PS-based azo LCBCs. All the PS nanocylinders were oriented along the magnetic field, which shows no effect on the lamellar morphologies. Source Reproduced with modifications from Tomikawa et al., 2005.

A colloidal suspension of nanostructured PBI-graphene sheets was used to modify a gold electrode to form a three-dimensional electrode with a sensitivity to hydrogen peroxide [25]. The positively charged nanostructured PBI separate the graphene sheets and keep them suspended in aqueous solution. This so fabricated electrode exhibits superior sensitivity toward hydrogen peroxide. 

Dispersion, although is a process pushed by macroscopic tools and processes, results in very fine and precisely exhibited nanostructures in a polymeric matrix, a monomolecular layer of 15 nm thickness is forced to adsorb on the particles becoming dispersed down to a particle size of 50-250 nm (depending on matrix nature, process efficiency etc.). These particles (with their adsorbed layer) phase separate to monolayers (with a thickness of 80-280 nm), wherein flocculation and network formation occurs at and... 

The extraordinary physical and mechanical properties of BNC pellicles arise from their xmique nanostructure. Well-separated nano- and microfibrils of microbial cellulose create an extensive surface area, which combined with its highly hydrophilic nature, results in a very high liquid loading capacity (i.e., 98-99% for water, much higher than plant cellulose), while maintaining a high degree of conformability [46]. 

---