Nanospace

Uchiyama S, McClean GD, Iwai K et al (2005) Membrane media create small nanospaces for molecular computation. J Am Chem Soc 127 8920-8921... 

The combined features of structural adaptation in a specific hybrid nanospace and of a dynamic supramolecular selection process make the dynamic-site membranes, presented in the third part, of general interest for the development of a specific approach toward nanomembranes of increasing structural selectivity. From the conceptual point of view these membranes express a synergistic adaptative behavior the addition of the most suitable alkali ion drives a constitutional evolution of the membrane toward the selection and amplification of a specific transport crown-ether superstructure in the presence of the solute that promoted its generation in the first place. It embodies a constitutional selfreorganization (self-adaptation) of the membrane configuration producing an adaptative response in the presence of its solute. This is the first example of dynamic smart membranes where a solute induces the preparation of its own selective membrane. 

Conducting reactions in nanospace where the dimensions of the reaction vessel are comparable to those of the reactants provides a new tool that can be used to control the selectivity of chemical transformations.1 This dimensional aspect of nano-vessels has been referred to as shape selectivity.2 The effect of spatial confinement can potentially be exerted at all points on the reaction surface but its influence on three stationary points along the reaction coordinate (reactants, transition states, and products) deserve special attention.3,4 (1) Molecular sieving of the reactants, excluding substrates of the incorrect dimension from the reaction site can occur (reactant selectivity). (2) Enzyme-like size selection or shape stabilization of transition states can dramatically influence reaction pathways (transition state selectivity). (3) Finally, products can be selectively retained that are too large to be removed via the nano-vessel openings/pores (product selectivity). 

In addition to shape selectivity, which is primarily a steric directing effect, orbital confinement,5 a quantum6 electronic7 effect, can also dramatically influence reactivity in nanospace.8 10 This concept, first introduced by Corma and coworkers,8 points out that when molecular orbitals are confined and not allowed to extend over all space that their energies increase. The HOMO is more sensitive than the LUMO to size restrictions resulting in a decrease of the frontier molecular orbital band gap. This effect can be experimentally demonstrated in systems where the size of the... 

Shape selectivity and orbital confinement effects are direct results of the physical dimensions of the available space in microscopic vessels and are independent of the chemical composition of nano-vessels. However, the chemical composition in many cases cannot be ignored because in contrast to traditional solution chemistry where reactions occur primarily in a dynamic solvent cage, the majority of reactions in nano-vessels occur in close proximity to a rigid surface of the container (vessel) and can be influenced by the chemical and physical properties of the vessel walls. Consequently, we begin this review with a brief examination of both the shape (structure) and chemical compositions of a unique set of nano-vessels, the zeolites, and then we will move on to examine how the outcome of photochemical reactions can be influenced and controlled in these nanospace environments. 

H. Tanaka, H. Kanoh, M. El-Merraoui, W.A. Steele, M. Yudasaka, S. Ijiima, K. Kaneko, Quantum effects on hydrogen adsorption in internal nanospaces of single-wall carbon nanohorns. J. Chem. Phys. B, 108(45) (2004) 17457-17465. 

Ultrafast photoreaction dynamics in protein nanospaces (PNS) as revealed by fs fluorescence dynamics studies on photoactive yellow protein (PYP) and related systems... 

So far, direct evidence of C60 hydrogenation inside of nanotubes from HRTEM imaging is absent. It is required as a decisive demonstration of possibility for hydrogen to penetrate inside of peapods but could possibly be challenging experimentally. Chemical reaction within nanospace of carbon nanotubes is possibly only first example of interesting nanoscale chemistry and fullerene hydrogenation in other exotic environments will possibly be successfully demonstrated in future. It is quite likely that hydrogenation in confined space results in formation of fulleranes with different molecular structures. 

Ford DM Simanek EE Shantz DF, Engineering nanospaces Ordered mesoporous silicas as model substrates for building complex hybrid materials, Nanotechnology, 2005,16, S458-S475. 

Synzymes may achieve rate enhancements via binding and proximity effects. Such effects can occur when two reactive partners are bound within the same nanospace, thus increasing their relative encounter frequencies (i.e., the effective concentrations) (Fig. 13.1a) [4]. Some synzymes participate as reagents, and these catalysts feature structurally distinct substrate-binding site(s), together with a cat-alytically effective site(s) (Fig. 13.1b). 

Fig. 13.1 Synzymes may catalyze reactions by binding two (or more) reagents within the same nanospace (a), or they may perform the transformation with the help of catalytically effective site(s) (b).

Koblenz TS, Wassenaar J, Reek JNH (2008) Reactivity within a confined self-assembled nanospace. Chem Soc Rev 37 247... 

Freezing point elevation in nanospace detected directly by atomic force microscopy... 

The employed technique for this purpose was the so-called colloidal-probe AFM (Atomic Force Microscopy). A carbon microparticle with high degree of carbonization was attached to the top of the cantilever tip, forming the colloidal probe, and its interaction force with cleaved graphite was measured within a liquid cell filled with organic liquid, controlled at a desired temperature above the bulk freezing point of the liquid. The two surfaces will form a slit-shaped nanospace because the radius of the particle is far larger than the separation distance concerned here. 

Graphite plate carbon particle Fig. I Schematic drawing of AFM apparatus and image of the nanospace formed between surfaces. 

A graphite plate (HOPG) and carbon particles, which were made from phenolic resin by pyrolyzmg above 2000TI.. were used to form a nanospace with carbonaceous surfaces The particles were evacuated at I lOTl for 24 h before use. The graphite plate was freshly cleaved before measurement. 

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