Carbon nanoscale materials

Resasco, D.E., Carbon Nanotubes and Related Structures. In Nanoscale Materials in Chemistry, 2nd Ed., Klabunde K. J. Richards R. M. (eds.), John Wiley. Sons, Inc., Hoboken,... 

The lure of new physical phenomena and new patterns of chemical reactivity has driven a tremendous surge in the study of nanoscale materials. This activity spans many areas of chemistry. In the specific field of electrochemistry, much of the activity has focused on several areas (a) electrocatalysis with nanoparticles (NPs) of metals supported on various substrates, for example, fuel-cell catalysts comprising Pt or Ag NPs supported on carbon [1,2], (b) the fundamental electrochemical behavior of NPs of noble metals, for example, quantized double-layer charging of thiol-capped Au NPs [3-5], (c) the electrochemical and photoelectrochemical behavior of semiconductor NPs [4, 6-8], and (d) biosensor applications of nanoparticles [9, 10]. These topics have received much attention, and relatively recent reviews of these areas are cited. Considerably less has been reported on the fundamental electrochemical behavior of electroactive NPs that do not fall within these categories. In particular, work is only beginning in the area of the electrochemistry of discrete, electroactive NPs. That is the topic of this review, which discusses the synthesis, interfacial immobilization and electrochemical behavior of electroactive NPs. The review is not intended to be an exhaustive treatment of the area, but rather to give a flavor of the types of systems that have been examined and the types of phenomena that can influence the electrochemical behavior of electroactive NPs. 

An additional factor which may modify the lung toxicity and corresponding risk following exposures to engineered nanoparticulates is the electrostatic attraction/aggregation or agglomeration potential of some nanoscale materials, such as single wall carbon nanotubes (SWCNT). The dimensions of individual SWCNTs have been reported as Inm (diameter... 

Possible Mechanisms and Key Characteristics of Nanomaterials. A nanoparticle/nanomaterial is generally defined as a particle/ material having a physicochemical structure greater than typical atomic/molecular dimensions but at least one dimension smaller than lOOnm. It includes particles/ materials engineered or manufactured by humans on the nanoscale with specific physicochemical composition and structure to exploit properties and functions associated with its dimensions. Some of the common nanoparticle types are (1) carbon-based materials (e.g., nanotubes, fullerenes), (2) metal-based materials (e.g., nanogold, nanosilver, quantum dots, metal oxides), and (3) dendrimers (e.g., dendritic forms of ceramics). 

Both EDLCs and pseudocapacitors benefit from tailored, high surface area architectures because they each store charge on the surface by electrostatic or faradaic reactions, respectively. There are numerous examples in the hterature which show that materials possessing such features as nanodimensional crystallite size and mesoscale porosity exhibit significantly higher specific capacitance as compared to nonpotous materials or materials composed of micron-sized powders. The assembly of nanoscale materials is also important. One structure envisioned to be of interest is an array of vertically aligned carbon nanotubes where the spacing between the tubes is matched to the diameters of the solvated electrolyte ions (3). 

In the field of nanoscale materials, SIESTA has probably made its largest impact in the study of carbon nanotubes. This is a field which has captivated the attention of researchers for their unusual electronic and mechanical properties. Simulation and theory have played a major role, often providing predictions that have guided the way for experimental studies. Work done with SIESTA has spanned many aspects of nanotube science vibrational properties [239-241], electronic states [242-246] (including the effect of lattice distortions on the electronic states [247-250]), elastic and plastic properties [251-254], and interaction with other atomic and molecular species [255-259]. Boron nitride nanotubes have also received some attention [260, 261]. 

There is also a distinction to be drawn between nanoscience and nanotechnology. Nanoscience is the sub-discipline of science that involves the study of nanoscale materials, processes, phenomena and/or devices. Nanoscience includes materials and phenomena at the nanoscale (typically 0.1-100 nm) hence, it includes areas such as carbon nanoscience (e.g. fullerenes), molecular scale electronics, molecular self-assembly, quantum size effects and crystal engineering. Nanotechnology involves the design, characterization, manipulation, incorporation and/or production of materials and structures in the nanoscale range. These applications exploit the properties of the nanoscale components, distinct from bulk or macroscopic systems. Naturally, there is a substantial overlap of scale between nanotechnology and colloid technology. 

In general, the term nanoscale applies to dimensions on the order of 1-100 nanometers (1 nm = 10" m), and one goal of nanotechnology is to develop useful nanoscale devices nano-devlces). Because typical covalent bonds range from 0.1-0.2 nm, chemical structures hold promise as candidates on which to base nanodevices. Among them, much recent attention has been given to carbon-containing materials and even elemental carbon itself. 

Kim, C., Lee, Y. H. (2003). EDLC Application of Carbon Nanofibers/Carbon Nanotubes Electrode Prepared by Electmspinning, in 203rd Meeting, Symposium Nanotubes, Nanoscale Materials, and Molecular Devices, The Electrochemical Society Paris, France. 

Wanekaya, A.K. (2011) Applications of nanoscale carbon-based materials in heavy metal sensing and detection. Analyst, 136, 4383. 

Nanoscale materials do exhibit chemical and ph5 ical properties from different bulk materials. For example, carbon can be made to form tubular structures as shown in Figure 1.23 A. These tubes, called nanotubes, resemble a cylindrical roU of chicken wire. When nanotubes are perfectly formed, they conduct electricity like a metal. 

In October 2008, EPA issued a federal register notice reiterating its position that it would not treat aU nanoscale materials as new chemical substances under TSCA (Environmental Protection Agency, 2008a). However, EPA also classified carbon nanotubes as new and distinct chemical... 

California has indicated that its data call in efforts for engineered nanoscale materials will not end with carbon nanotubes. Rather, it intends to issue a series of letters over the coming months, focusing on various types of engineered nanoscale materials of potential concern. 

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