Addressable molecular devices

Present address Molecular Devices Corporation, 4700 Bohannon Drive, Menlo Park, California 94025, USA. 

In addition to the immunochromatographic assays, another system used by the Allies during Desert Storm for the detection of biological warfare agents was the Light Addressable Potentiometric System (LAPS) produced by Molecular Devices (Sunnyvale, CA)19. The LAPS detected toxins and... 

From this comparison it can be concluded that on the device level there are fundamental limits for the miniaturization of hybrid-molecular electronics, which are not only governed by the size of the molecule but also depend on the size that an electromechanical or capacitative grid has to have in order to influence its energy levels. These architectural issues regarding the interfacing of a molecular device to the outside world or the assembly of many devices into larger circuits will have to be addressed to a larger extent in the near future. 

In conclusion, this book is intended as an overview of the principles behind and state-of-the-art in interfacial supramolecular chemistry. The book is suitable for researchers and graduate students and focuses on assemblies that demonstrate at least the potential to produce useful devices such as solar cells, electrochromic devices, molecular wires, switches and sensors which are addressable by using electrochemical and optical stimuli. Molecular materials for nanoscale molecular devices remain an intriguing conceptual possibility. 

The exohedral derivatives of fullerenes with organometallic compounds have received extensive attention and appropriate materials have been generated as catalysts, molecular devices, liquid crystals, and so on [10-13]. The discussion in this chapter will not address such materials but will only specifically examine endohedral metallofullerenes because they are viewed as more unique, fascinating, and promising due to the strong interactions between the encapsulated metallic species and the carbon cages [2]. 

The systems discussed above have been studied in solution, where each molecule behaves independently. Incoherence, therefore, remains a major impediment to designing and realizing systems capable of performing useful functions. The problem of obtaining ordered arrays of molecular devices that can comunicate with the macroscopic world can be addressed by their aggregation on surfaces [70] or organization at liquid-gas or liquid-liquid interfaces [71]. 

In this chapter we focus our attention on the use of rotaxanes as the framework for the assembly of switchable molecules. This is indeed only one of the many different types of molecules and molecular assemblies that have been proposed in the literature as candidates for the development of novel devices. However, the chemistry of rotaxanes has developed considerably, mostly through the efforts of Professor Stoddart and his coworkers [4]. We will describe some of our own collaborative work with the Stoddart group and venture into some relatively unexplored aspects of the physical chemistry of rotaxanes. We will also address in detail some of the real problems that hamper the practical use of molecular devices in technological applications. Finally, we will discuss the use of metal and semiconductor nanoparticles as a possible new route for the development of new types of molecular devices. 

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