Editorial Feature

Molecular Electronics and Quantum Dots - Properties and Future Applications

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New manufacturing concepts and new materials are required for building electronics at the molecular level. While traditional micro-fabrication methods are approaching the limits of their capabilities, costs and complexities relating to fabrication continue to increase.

Continued innovations in the electronics, IT, and communications sectors would be hampered due to physical restrictions of silicon-based devices. Until solutions are identified, the growing cost of these materials combined with environmentally sensitive and costly processes required for fabrication will continue to stress the electronics sector.

Hence, to overcome these limitations, a wide range of alternative computer architectures has been recommended, including the ones based on optical circuitry, DNA, and quantum mechanical phenomena. One promising area is the application of individual molecules as active electronic devices.

Molecular Electronics in the Future

Molecular electronics look for ways to substitute existing electronics technology by applying one or a few molecules to work as connections, switches, and other logic devices. Molecules arrange themselves into devices that go beyond the restrictions of stiff silicon-based solutions and produce strong and conductive interconnects through environmentally sensitive fabrication methods.

Molecular electronics cover a number of extensive fields and they overlap with many more domains, spanning everything from the fabrication of optical disks based on films of bistable biomolecules to the theoretical design of computers based on molecular switches and wires.

The Future of Molecular Computing

It is predicted that molecular computing will substitute silicon-based computing toward the end of the decade. At the University of California, chemists have developed a molecular switch that can be switched on and off hundreds of times, just a year after the development of a switch that can be turned on only once. Nevertheless, the development of molecular random access memory, or RAM, continues to pose a challenge to the feasibility of molecular computing; however, this new step has made it easy to access molecular RAM.

Both UCLA and HP researchers are working together to develop molecular computers that are able to learn and become enhanced when they are used often. Molecular switches are important for creating computers of this kind. The most recent molecular switches were developed using special molecules, known as catenanes. These contain a pair of small mechanically interlocked rings, with each ring made up of atoms joined in a circle.

The switching motion—caused by removing and restoring an electron—is the molecular basis for the current device. These molecules move in a coherent motion and are capable of identifying one another and lining up in an efficient way. The catenanes are an enhancement over rotaxane molecules. By contrast, rotaxanes remained in a solution state and were relatively more incoherent.

The Background to Quantum Dots

Quantum dots can be defined as crystalline particles of semiconductor materials, which are not visible under normal conditions because they are smaller than the wavelength of visible light. Quantum dots can impart novel properties and, at the same time, remain invisible themselves. They luminesce under ultraviolet light, with the size of the dots regulating its color.

Quantum Dots and their Properties

Quantum dots will remain lit or fluoresce much longer when compared to dyes that are traditionally used for tagging cells. They are demonstrating good potential in early warning test kits for diseases.

Quantum dots are tagged to proteins and their glow helps in identifying specific DNA or proteins, through which numerous diseases can be diagnosed. The amount of light transmitted in a specific color can be used to establish the amount of protein present on each cell. A change in protein concentration on every cell can act as an early indicator of cancer.

Other Unique Properties of Quantum Dots

In addition, quantum dots have other special electronic properties. The shape and size of their structures and thus the number of electrons present in them can be accurately controlled. As a matter of fact, a quantum dot can have anything from one electron to a group of several thousands of electrons.

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