Devices molecular switching device

Figure 14. An orthogonally-fused system that could act as a molecular switching device.

Introduction of an azabenzene unit into the surfactant backbone permitted light-induced cis-trans rearrangements. A change in conductivity accompanied the cis-to-trans transition. Thus, these LB films offer a basis for the construction of molecular switching devices (Fig. 120) [743-745],... 

Kawai, S. H., Gilat, S. L., Lehn, J. M., Dual-Mode Optical-electrical molecular switching device. J. Chem. Soc., Chem. Commun. 1994, 1011-1013. 

Fig. 8. Schematic of the procedure used for fabrication of nanoscale molecular-switch devices by imprint lithography [62]. (a) Deposition of a molecular film on Ti/Pt nanowires and their micron-scale connections to contact pads, (b) Blanket evaporation of a 7.5 nm Ti protective layer, (c) Imprinting of 10 nm Pt layers with a mold that was oriented perpendicular to the bottom electrodes and aligned to ensure that the top and bottom nanowires crossed, (d) Reactive ion etching with CF4 and O2 (4 1) to remove the blanket Ti protective layer.

S. H. Kawai, S. L. Gilat, R. Ponsient, and J.-M. Lehn, A Dual-mode molecular switching device bis-phenolic diarylethenes with integrated photochromic and electrochromic properties, Chem. Eur. J. 1, 285-293 (1995). 

The suitability of fluorescent PET systems for use in the emerging field of molecular switching devices was pointed out in Sect. 4 due to their natural on-off action induced by ion input. Discussions in Sect. 6 have also illustrated the value of PET sensor ideas in the design of reagents and also of reporters on receptor-guest interactions. Such versatility of the fluorescent PET sensor logic makes this research worthwhile. 

Long-distance intervalence electron transfer is now demonstrated with metal-metal distances up to 25 A. Distance dependence of electron transfer has strong implications for the search of, for example, molecular switch devices or biosensors. The bridging ligand dicyanamidobenzene has been extensively studied, and for example, complex (18) exhibits a very strong coupling (0.32 eV) for a metal-metal distance of 19.5 A. ... 

I. Yamazaki, N. Ohta, Photochemistry in LB Films and Its Application to Molecular Switching Devices , Pure Appl. Chem., 67, 209 (1995)... 

The reversible nature of self-assembling capsules has already been exploited as molecular switching devices and catalysts. Other applications may involve the development of artificial enzymes, and the design of specific drug delivery systems. 

Another topic of current chemistry should be addressed here briefly, again with reference to the article on "Rotaxancs and Pseudorotaxanes, where further aspects of molecular machinery are discussed in greater detail. A solid state, electronically addressable, bistable L21catc-nane-based molecular switching device was fabricated from a single monolayer of the [21catenane. - The... 

These systems may afford promising candidates for superconducting LB films and for molecular switching devices. 

A wide range of instrumental techniques are needed to characterise products fully - X-ray crystallography, mass spectrometry (especially FAB-MS and electrospray MS), H and NMR, UV-Vis spectroscopy, and electrochemistry - in the solid state and in solution. As much information as possible is needed in order to establish both the exact nature and long-range structural features (superstructure) of rotaxanes, catenanes and knots. As noted at appropriate points in the text, there is considerable interest in applications for these classes of compounds, particularly in respect to molecular switching devices. 

Like rotaxanes, catenanes are mechanically interlocked molecules. However, instead of interlocking one ring shaped macrocycle and a dumbbell shape, catenanes consist of interlocked macrocycles. The number of macrocycles contained in a catenane is indicated by the numeral that precedes it. Catenanes have bistable and multistable forms and a switchable, bistable [2]catenane is commonly exploited in nanotechnology and molecular electronics because its behavior can be controlled by electrochemical processes [89]. Collier et al. was the first to demonstrate the electroactivity of interlocked catenanes [90]. The authors affixed phospholipid counterions to a monolayer of [2]catenanes and then sandwiched this system between two electrodes. This work resulted in a molecular switching device that opened at a positive potential of 2 V and closed at a negative potential of 2 V. 

New natural polymers based on synthesis from renewable resources, improved recyclability based on retrosynthesis to reusable precursors, and molecular suicide switches to initiate biodegradation on demand are the exciting areas in polymer science. In the area of biomolecular materials, new materials for implants with improved durability and biocompatibility, light-harvesting materials based on biomimicry of photosynthetic systems, and biosensors for analysis and artificial enzymes for bioremediation will present the breakthrough opportunities. Finally, in the field of electronics and photonics, the new challenges are molecular switches, transistors, and other electronic components molecular photoad-dressable memory devices and ferroelectrics and ferromagnets based on nonmetals. 

Delonno E, Tseng HR, Harvey DD, Stoddard JF, Heat JR (2006) Infrared spectroscopic characterization of [2]rotaxane molecular switch tunnel junction devices. J Phys Chem B 110 7609-7612... 

Fig. 7 A molecular switch made of the leg of a legged Cu-porphyrin adsorbed on a Cu(211) surface, (a) An idealized version of such a molecular switch where the switching leg is exactly interconnected to two atomic wires in a Fig. la like configuration. The device resistance is maximum for a perpendicular = 0 conformation, (b) The real experimental device where the STM tip apex can be maintained at 0.7 nm or 0.9 nm separation between the tip and the surface in between the leg switching. In this case, the resistance is minimum for perpendicular to the Cu(211) surface = 0 conformation. The energetic of the switching mechanism can be calculated and the switching barrier height was also determined experimentally...

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