Confinement nanostructured materials

Zhang, L.Z., Sun, W. and Cheng, P. (2003). Spectroscopic and theoretical studies of quantum and electronic confinement effects in nanostructured materials. Molecules 8, 207-222... 

The chapters in this volume present detailed insights into the synthesis-structure-properties relationships of nanostructured materials. In particular, the catalytic and photocatalytic properties of nanoclusters and nanostructured materials with ultrahigh surface-to-volume ratio are demonstrated. The gas absorption characteristics and surface reactivity of nanoporous and nanocrystalline materials are shown for various separation and reaction processes. In addition, the structural manipulation, quantum confinement effects, transport properties, and modeling of nanocrystals and nanowires are described. The biological functionality and bioactivity of nanostructured ceramic implants are also discussed. 

As stated earlier, catalytic processes contribute at least 20% of the GDP of the United States. Thus, one of the most important applications of nanostructured materials in chemistry lies in the field of heterogeneous catalysis. It is beyond the scope of this chapter to discuss the numerous applications of nanoparticles as catalysts. However, we confine our discussion to a select few examples that demonstrate the potential application of nanoparticles in the field of catalysis. 

Thin films of block copolymers are likely to find many applications as nanostructured materials, due to the ability to tailor nanoscale dot and stripe patterns. Theory for microphase separation in thin films, especially the effect of confinement on structure orientation is now quite advanced. " Models for the effect of confinement on thermodynamics have also been developed, although this aspect has attracted less attention. 

Keywords Polymer crystallization NMR of polymers Polyethylene Hexagonal phases Nanostructured materials Confined polymers Crystal engineering Nanochannels... 

He, H., Y. Zhao, B. Xu, and N. Tao. 2001. Electrochemical potential controlled electron transport in conducting polymer nanowires. Proc Electrochem Soc 19 Quantum confinement VI Nanostructured materials and devices) 20-22. 

Since the discovery of the intense red photoluminescence of porous silicon [1,2], much work has been devoted to this particular nanostructured material [4, 5] and, in the meantime, also to silicon nanoparticles [6, 7]. An important issue of current studies is the influence of the surface passivation on the photoluminescence properties. It has already been said that, in the quantum confinement model, it is essential that the surface is well passivated to avoid any dangling bonds [8]. Being middle-gap defects, these dangling bonds will quench the PL. On the other hand, the surface itself may lead to surface states that can be the origin of another kind of photoluminescence [9,10]. 

This review focuses on the acid-base properties of surfaces of porous solids. In the context of the above discussion, it is inevitable that established practices will require some modifications. It is obvious that solids possess acidity and basicity. The challenge in characterizing their acid-base behavior results from the presence of two phases and from location of the acid-base sites at the interface between the solid and either a gaseous or liquid phase. Moreover, when acid-base chemistry occurs in spaces confined to the micropores or interlayers of nanostructured materials, the rules are broken a second time because all references to acid-base properties of macroscopically honlogeneous phases based on the classical approach become inconsistent. 

Carbon nanotubes (CNT) are formed by a hollow cylinder formed by a unique carbon sheet forming a single walled carbon nanotube (SWCNT) or concentric carbon sheets with different diameters forming multiwalled carbon nanotubes (MWCNT) with carbon-carbon with sp bonding [75]. The particular cylindrical form of CNT is the principal aspect that provides the quantum confinement effect in the oriented ID nanostructured materials [80]. These characteristics provide the possibUity to increase chemical reactivity and electronic properties of this particular carbon material, which becomes a crucial point for biosensing devices [75]. 

J.L. Marin, R. Riera, R. A. Rosas Confined systems and nanostructured materials. In Nanomaterials, Flandbook of Advanced Electronic and Photonic Materials and Devices, Vol.9, ed. by H.S. Nalwa (Elsevier, Amsterdam 2000) p. 55 J.M. Flartmann, M. Charleux, J. L. Rouviere, H. Ma-riette Growth of CdTe/MnTe tilted and serpentine lattices on vicinal surfaces, Appl. Phys. Lett. 70, 1113-1115 (1997)... 

Part 5 covers special structures such as liquid crystals, solid surfaces and mesoscopic and nanostructured materials. The chapter on liquid crystals covers physical properties of the most common liquid crystalline substances as well as some liquid crystalline mixtures. Data compiled in the chapter on solid surfaces refer to atomically clean and well characterized surfaces. The values reported are mainly averages from different authors where reference to the original papers is made. In the chapter on nanostructured materials emphasis is placed on size and confinement effects. The properties associated with electronic confinement are addressed and particular attention is drawn to semiconductor-doped matrices. The two main applications of nanostructured magnetic materials, spintronics and ultrahigh-density data storage media, are also treated. 

Nanostructured materials obtained by sol-gel encapsulation of biomolecules are a novel class of biomaterials. The biological macromolecules, confined within the nanometer-size pores of the matrix, show both similarities to and differences from solution characteristics. The effects of nanoconfinement on the structural and reactivity patterns of the proteins and enzymes are discussed. The applications of these nanostructured biomaterials in the area of molecular biorecognition, detection, and biosensing are also presented. 

The paper is organized in three parts. First, the effects of nanoconfinement on the structure of the sol-gel trapped biomolecule are discussed. Second, from the results on apparent reactivity of these biomaterials, the effects of the matrix on the reactivity of trapped enzyme are elucidated. Finally, the interaction of the confined biomolecules with exogenous ligands/substrates and the applications of these materials in the area of molecular biorecognition are discussed. The reaction chemistries of biologically active molecules in die nanostructured materials have been crucial in establishing the role of the matrix upon the structure and reactivity of the confined proteins. 

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