Essay Example on Study of the literature related with the DNA based Molecular Junction Devices

ABSTRACT This review paper is dedicated to the study of the literature related with the DNA based Molecular Junction Devices It first focuses on the Molecular Devices with the area of interest being molecular wires The DNA being a self assembled Molecular wire we will look into the the DNA based Molecular Junction Devices A lot of research has been done on the Charge Transport Mechanism in the DNA We will see whether it is hopping mechanism or tunneling mechanism or some other Further as it has been researched that DNA can be used as a molecular wire we would concentrate our research on the various factors that would effect the conductivity of the DNA wire The various factors can be Length sequence Structural Fluctuations such as stretching the quantity of nucleotide content the electrode material used the miller orientation of the electrode etc Further we would see the various electronic structures based on DNA and its bases We would also briefly look into how far the four bases of DNA i e Adenine Guanine Thymine Cytosine have been exploited so far and their conductivities and their use to make some devices So we will review the literature related to these topics and see into the challenges faced so far and what is the future scope in this field

 INTRODUCTION MOLECULAR DEVICES The ability to utilize single molecules that function as electronic devices has motivated researchers all over the world for years with the continuous drive to reduce to the minimum the electronic circuit elements in semiconductor industry We are presently close to the limit of this reduction in size trend It is possible that electronically functional molecular components can not only address the ultimate limits of possible miniaturization as well as nonlinear devices and memories Miniaturization can be pushed further because There is plenty of room at the bottom as Richard P Feynman stated in a famous talk Upto now many molecules with electronic properties have been identified Many molecules also posses rich optical magnetic thermoelectric electromechanical and molecular recognition properties which can form new devices to replace conventional materials MOLECULAR WIRES Molecular wires are the building blocks of molecular electronics Their typical diameters are less than 3 nm while theor lengths may be macroscopic extending to mm and cm and more Molecular wires are also known as nanowires These are molecular chains that conduct electric current Connecting the Devices In order to use the single molecule electronic components described above in a functional way while preserving the small scale they have to be connected by conducting wires of the same molecular dimensions One of the first to coin the term molecular wire was the 1988 Nobel prize winner Lehn who described a caroviologen molecule that could be incorporated into vesicle membranes 

1 The charge in such a chain can transfer easily through the conjugated pathway between the two terminal groups of the molecule These wires consist of a piece of conjugated polymer analogous to the polymers used for organic electronics In such conjugated polymers generally there is a considerable amount of conformational freedom most notably the rotational freedom around the formally single bonds in the chain 2 Therefore more rigid alternatives have also been proposed as show in One of the advantages of using organic molecules as molecular wires is the level of control over the structural and electronic properties of these wires The conjugated wires can be designed to meet the required rigidity In the last few years researchers have found out that basic building block of all living organisms that is a strand of DNA can also be used as a conductor semiconductor or an insulator in electronic circuits So DNA becomes a great contender for electronic equipments with such small size and self assembling capabilities It is a self assembling molecular wire DNA Deoxyribonucleic Acid stores biological information It contains the genetic instructions used in development functioning and reproduction of all living things DNA is made of proteins lipids and has four major types of molecules that are essential for all known forms of life So DNA is composed of four nitrogen containing nucleobases Cytosine C Thymine T Guanine G Adenine A Nucleotides are attached together to form two long strands that spiral to create a structure called a double helix If you think of the double helix structure as a ladder the phosphate and sugar molecules would be the sides while the bases would be the rungs The bases on one strand pair with the bases on another strand guanine pairs with cytosine and adenine pairs with thymine DNA was first observed by a German biochemist named Frederich Miescher in 1869 

But for many years researchers did not realize the importance of this molecule It was not until 1953 that James Watson Francis Crick Maurice Wilkins and Rosalind Franklin figured out the structure of DNA a double helix which they realized could carry biological information Watson Crick and Wilkins 4 were awarded the Nobel Prize in Medicine in 1962 for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material Nobody would have thought then that this DNA could become a potential electronic component and used in electronic circuits at one time Electron transport through DNA is unrelated to its already known functions and has received a very large amount of attention over the last 30 years after various results have been reported It varies from good conducting properties to semiconductor behavior and insulators Long DNA molecules are considered Insulators whereas short DNA molecules show significant conductance The beauty of DNA lies in the fact that it uses the techniques of genetic engineering that nature has perfected under harsh conditions over billions of years Various studies have confirmed that DNA can act as a molecular wire with phosphate bonds in the DNA backbone acting as tunnel junctions for electrons to move along the DNA based Molecular Junction Devices It first focuses on the Molecular Devices with the area of interest being molecular wires The DNA being a self assembled Molecular wire we will look into the the DNA based Molecular Junction Devices A lot of research has been done on the Charge Transport Mechanism in the DNA We will see whether it is hopping mechanism or tunneling mechanism or some other Further as it has been researched that DNA can be used as a molecular wire we would concentrate our research on the various factors that could affect the conductivity of the DNA wire 

Their typical diameters are less than 3 nm while their lengths may be macroscopic extending to mm and cm and more Molecular wires are also known as nanowires These are molecular chains that conduct electric current Connecting the Devices In order to use the single molecule electronic components described above in a functional way while preserving the small scale they have to be connected by conducting wires of the same molecular dimensions One of the first to coin the term molecular wire was the 1988 Nobel prize winner Lehn who described a caroviologen molecule that could be incorporated into vesicle membranes 1 The charge in such a chain can transfer easily through the conjugated pathway between the two terminal groups of the molecule These wires consist of a piece of conjugated polymer analogous to the polymers used for organic electronics In such conjugated polymers generally there is a considerable amount of conformational freedom most notably the rotational freedom around the formally single bonds in the chain 2 Therefore more rigid alternatives have also been proposed as show in One of the advantages of using organic molecules as molecular wires is the level of control over the structural and electronic properties of these wires The conjugated wires can be designed to meet the required rigidity In the last few years researchers have found out that basic building block of all living organisms that is a strand of DNA can also be used as a conductor semiconductor or an insulator in electronic circuits So DNA becomes a great contender for electronic equipments with such small size and self assembling capabilities It is a self assembling molecular wire DNA Deoxyribonucleic Acid stores biological information It contains the genetic instructions used in development functioning and reproduction of all living things DNA is made of proteins lipids and has four major types of molecules that are essential for all known forms of life So DNA is composed of four nitrogen containing nucleobases Cytosine C Thymine T Guanine G Adenine A Nucleotides are attached together to form two long strands that spiral to create a structure called a double helix If you think of the double helix structure as a ladder the phosphate and sugar molecules would be the sides while the bases would be the rungs