Nanodevices, nanoelectronics

Nanoscale devices and machines are either present in nature [67] or must be synthesized starting from more simple components [68-70]. The idea that atoms could be used to construct nanoscale devices and machines was first raised by Feynman in the previously mentioned address There is plenty of room at the bottom [21]. A key sentence of Feymnan s talk is the following The principles of physics do not speak against the possibility of maneuvering things atom by atom . The advent of nanotechnology was depicted in an exciting and visionary way by Eric 

The bottom-up approach opens virtually unlimited possibilities regarding the design and construction of artificial molecular devices and machines capable of performing specific functions upon stimulation with external energy inputs [84], Furthermore, such an approach can provide invaluable contributions to give a better understanding of the molecular-level aspects of the extremely complicated devices and machines that are responsible for biological processes. 

Molecular devices and machines operate via electronic and nuclear rearrangements, that is, through some kind of chemical reaction. Like their macroscopic counterparts, they are characterized by 

1) the kind of energy input supphed to make them work, 

In the late 1970s, a new branch of chemistry called supramolecular chemistry emerged and expanded very rapidly [86, 87]. In the same period, research on molecular electronic devices began to flomish and the idea arose that molecules are much more convenient building blocks than atoms to construct nanoscale devices and machines [88]. The main reasons that provide the basis of this idea are as follows [78]  

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Nanodevices are systems with nanostructured materials that carry out specific functions with either improved performance or new attributes. Recent years have witnessed the emergence of new device paradigms based on nanostructured materials, including nanoelectronic devices, nano-optoelectronic devices, spintronic devices, nanosensors, and drug and gene delivery systems. 

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