Nanovalve

Although PMOs and related materials have many potential applications, including adsorbants,49,50 sensors,51 and catalysts,52,53 we focus here on two specific classes of functional materials, nanovalves and polymer-silica nanocomposites formed via the co-assembly of hybrid precursors (or polymer-monomer species) with surfactant mesophases. 

Figure 18.4 Fabrication and operation of a hybrid organic—inorganic nanovalve based on grafting of valve functionality to preformed nanoporous silica, (a) Grafting of ICTES to the surface of the mesoporous silica powders (b) linkage of a dialkylammonium pseudorotaxane to the surface of the silica through reaction with ICTES (c) loading of the pore volume with molecules (d) closing of the nanovalve by complexation of the dialkylammonium pseudorotaxane with a crown ether and (e) release of the pore volume contents by disruption of the crown ether-ammonium complex.

Kottas GS Clarke LI Horinek D Michl J, Artificial molecular rotors, Chem. Rev., 2005,105,1281 -1376. Saha S Leung KCF Nguyen TD Stoddart IF Zink II, Nanovalves, Adv. Funct. Mater., 2007, 17, 685-693. 

Kocer A, Walko M, Meijberg W, Feringa BL (2005) A light-actuated nanovalve derived from a channel protein. Science 309 755-758... 

Kocer A, Walko M, Eeringa BL (2007) Synthesis and Utilization of reversible and irreversible light activated nanovalves derived from the channel protein MscL. Nat Protoc 2 1426-1437... 

Nanovalve Nanovesicles Polymer nanocapsules PEG-coated PLA nanoparticles... 

FAU or MFI membranes can also be modified in order to allow an optical switching of gas transport [124], The switch (guest) is azobenzene and acts as a nanovalve which is inserted in FAU or MFI membranes (hosts). The flux of single components through the trans-slate azobenzene modified membrane is increased by a factor 3 to 6 compared to the cis-state membrane. 

A. Kocer, M. WaUco, W. Meijberg, B. L. Feringa, A light-activated nanovalve derived from a channel protein, Science, 2005, 309, 755-758. 

As described earlier, azobenzene-functionalized nanoporous silica films exhibit dynamic photocontrol of their pore size, which in turn enables photoregulation of mass transport through the film. Their potential applications in nanofluidic devices, nanovalves, nanogates, smart gas masks, membrane separation, and controlled release can be anticipated. 

Hernandez R, Tseng HR, Wong JW, Stoddart JF, Zink JI. 2004. An operational supramolecular nanovalve. J Am Chem Soc 126 3370 3371. 

Leung KCF, Nguyen TD, Stoddart JF, Zink JI. 2006. Supramolecular nanovalves controlled by proton abstraction and competitive binding. Chem Mater 18 5919 5928. 

Maniwa and co-workers have shown that water-SWCNTs can be used as a new type of molecular nanovalve [14]. They carried out a systematic investigation of water-SWCNTs in different gaseous environment below 0.1 MPa using electrical resistance. X-ray diffraction, NMR measurements, and MD simulations. They found that the resistivity of water-SWCNTs exhibits a significant increase in gas atmospheres below a critical temperature at which a particular type of gas molecule can enter the SWCNT in an on-and-off fashion. 

Y. Maniwa, K. Matsuda, H. Kyakuno, et al., Water-filled single-wall carbon nanotubes as molecular nanovalves. Nat. Mater., 6 (2007), 135-141. 

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