Overview Size Fascinations

Nanosolids, or so-called nanoparticles, nanoclusters, nanocrystallites, nanograins, etc., are defined as substance or device that is in the shape of a spherical dot, a cyhndrical rod, a thin plate, or a void of any irregular shape smaller than 10 nm across or substances consisting of such voids or grains that are weakly interconnected [4]. Monatomic chains and monolayer atomic sheets are ideal cases of the one- and the two-dimensional systems at the nanoscale. The substance of a nanosolid can be composites, compounds, alloys, or element media. From a fundamental point of view, nanostructures bridge the gap between an isolated atom and its bulk counterpart with the size dependency of known bulk properties and emerging properties that bulk materials do not have. 

The key difference between a sohd and its elementally isolated atom is the involvement of interatomic interaction that varies with the coordination number (CN, z) of an atom. Without interatomic interaction, neither a solid nor even a liquid could form. The interatomic interaction causes a solid to be completely different from an isolated atom in performance. Compared with its bulk counterpart, on the other hand, a nanosolid has a high proportion of undercoordinated atoms (0 z 12) in the surface skin. For a spherical dot of one micrometer across, the volume sum of all surface atoms is only 1 % of the volume of the entire solid. For a 10 nm-sized dot, the surface-to-volume ratio is 25 % and it reaches 100 % when the solid is around one nm across or consists of three atomic shells or less. The atomic CN is two in the atomic chain interior or at the edge of a singlelayer graphene. Therefore, interaction between the undercoordinated atoms and the high fraction of such undercoordinated atoms form the key discriminating in nature a nanosolid from an isolated atom or from its bulk parent. 

Nanoscaled materials are offering a variety of novel features such as the size dependency of known bulk properties and emerging properties that the bulk parent does not have. New physical and chemical properties occur in such systems because of the unusual bonds between the undercoordinated atoms and the associated entrapment or polarization of electrons. 

The study of nanocrystalline materials is an active area of research in physics, chemistry, and materials engineering as well as biomedical engineering [5, 6]. The striking significance of miniaturizing a solid to the nanometer scale is the tun-ability of the measurable quantities of the solid in all aspects. In transport dynamics, quantized and resonant features due to size effect become apparent. In addition to the large surface-to-volume ratios, the surface, interface, and quantum effects take on a significance that is normally inconsequential for bulk materials. 

Pt containing a network of nanometer-sized pores could generate reversible strain with amplitudes comparable with those of commercially available actuators through surface-charging effects under potentials of about 1 V [24]. The conversion of an external electrical signal into a volume change, and a mechanical force, known as actuation, is of importance to small-scale devices. 

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