Nanostructured electron transport properties

The use of carbon-based nanomaterials such as CNTs and graphene for the development of POC biosensors has attracted attention due to their physical, electrical, electrochemical, and chemical properties. In particular, one-dimensional nanostructures are very attractive for designing high-density arrays for ultrasensitive protein detection due to their high surface-to-volume ratio and electron-transport properties. Such nanostructures represent a promise for the development of multiple biomaikers assays in ultrasmall sample volumes, being of special interest for medical areas. ... 

One-dimensional (ID) nanostructures such as nanowires, nanorods and nanobelts, provide good models to investigate the dependence of electronic transport, optical, mechanical and other properties on size confinement and dimensionality. Nanowires are likely to play a crucial role as interconnects and active components in nanoscale devices. An important aspect of nanowires relates to the assembly of individual atoms into such unique ID nanostructures in a controlled fashion. Excellent chemical methods have been developed for generating zero-dimensional nanostructures (nanocrystals or quantum dots) with controlled sizes and from a wide range of materials (see earlier chapters of this book). The synthesis of nanowires with controlled composition, size, purity and crystallinity, requires a proper understanding of the nucleation and growth processes at the nanometer regime. 

Polymeric materials have advantages because of their stability and structureforming properties. Electron- and ion-active organic polymeric materials have attracted attention for new devices. In Chapter 5, Kato and co-workers focus on polymeric liquid crystalline materials that are used for the development of functional materials transporting ions and electrons. The nanostructures such as smectic and columnar phases exhibited by side-chain, main-chain, dendritic, and network polymers may exhibit one- and two-dimensional transportation properties. 

In this chapter we report on properties of nanometer-sized semiconductor particles in solution and in thin films and thereby concentrate on the photochemical, photophysical, and photoelectrochemical behavior of these particles. We shall, very briefly, describe the energetic levels in semiconductors and the size quantization effect. The bottleneck in small-particle research is the preparation of well-defined samples. As many preparative aspects are already reviewed in several actual assays, we present here only the preparative highlights of the last two years. In Section IV we describe the fluorescence properties of the particles. We report on different models for the description of the very complex fluorescence mechanism and we show how fluorescence can be utilized as a tool to learn about surface chemistry. Moreover, we present complex nanostructures consisting of either linked particles or multiple shells of different nanosized materials. The other large paragraph describes experiments with particles that are deposited on conductive substrates. We show how the combination of photoelectrochemistry and optical spectroscopy provides important information on the electronic levels as well as on charge transport properties in quantized particle films. We report on efficient charge separation processes in nanostructured films and discuss the results with respect to possible applications as new materials for optoelectronics and photovoltaics. 

Nanostructures can affect ion and electron transport, accessibility of chemical reaction sites, and the fundamental properties of electroehemieal interfaces, among others. 

Mesoscopic materials form the subset of nanostructured materials for which the nanoscopic scale is large compared with the elementary constituents of the material, i. e. atoms, molecules, or the crystal lattice. For the specific property under consideration, these materials can be described in terms of continuous, homogeneous media on scales less than that of the nanostructure. The term mesoscopic is often reserved for electronic transport phenomena in systems structured on scales below the phase-coherence length A0 of the carriers. 

Formalism Electronic Configurations and Transport Properties of Nanostructures, Imperial College Press, London, 2005. 

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