Question

Single molecule devices are attractive to certain applications where small size and high capacity are both desirable. In terms of electrical conductivity capacity, most people would thick metal is the best and carbon based materials would be bad; is it true (or) not?

Provide an example to proof your argument.

Answer 1

Electrical conductivity is defined as the measure of the amount of electrical current a material can carry Electrical conductivity is also known as specific conductance. in other words electrical conductivity is a measure of how an electrical current moves within a substance.Conductivity is an intrinsic property of a material.

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The electrical conductivity units are siemens per metre, S?m^-1.

Electrical conductivity increases in a metallic conductor as the temperature is reduced. Below a critical temperature, resistance in superconductors drops to zero, such that an electrical current may flow through a loop of superconducting wire with no appliled voltage !

There are three main factors that affects the conductivity of a material:

1. Cross Sectional Area - If the cross section of a material is large, it can allow more current to pass through it. Similarly, a thin cross section restricts current flow.
2. Length of the Conductor - A short conductor allows current to flow at a higher rate than a long conductor.
3. Temperature - Increasing temperature makes particles vibrate or move more. Increasing this movement (increasing temperature) decreases conductivity because the molecules are more likely to get in the way of current flow.

Now we know carbon has allotrophes - Diamond,  Graphite, Lonsdaleite and  C60 (Buckminsterfullerene)

Graphite is an interesting material, an allotrope of carbon (like diamond). It displays properties of both metals, and nonmetals. Like metals, graphite is a very good conductor of electricity due to the mobility of the electrons in its outer valence shells.

In graphite each carbon atom is covalently bonded to three other carbon atoms. This arrangement makes layers of hexagonal rings that can slip past one another. In graphite each carbon atom has a free electron in its outermost energy shell. This free electron is responsible for conductivity of electricity through graphite.

now when we take a good conducting metal such as copper the  nucleus has 29 protons and 34 neutrons 29 electrons binding the nucleus .

Graphene has very high electron mobility ?105 cm2/Vs?105 cm2/Vs at room temperature but there are also some more problems such as graphene is brittle like a ceramic, which cannot handle mechanical strain.

Now we have a new emerging material called "graphene" It is a form of carbon consisting of planar sheets which are one atom thick, with the atoms arranged in a honeycomb-shaped lattice.

The flat, hexagonal lattice of graphene offers relatively little resistance to electrons, which passes through it quickly and easily, carrying electricity better than superb conductors(copper). the electrons in graphene have a longer mean free path than they in any other material which means they can move freely without any collosions what we called as "resistance".

Carbon nanomaterials consist solely of carbon, and are strong materials with good conductivity. Several scarce metals have similar properties. The metals are found, for example, in cables, thin screens, flame-retardants, corrosion protection and capacitors.

Computer chips where graphene is used , the electrons are faster and much more mobile, which opens up the possibility of its application in computer chips that work more quickly (and with less power) . Graphene is an alternative to silicon ( a rare material) ,If the speed and power requirements of computers keep increasing, silicon may loose its popularity

Graphene also revolutionizing electrical energy storage by vastly improving ultra-capacitors. These are the specialized batteries that can supply huge logs of energy over a short duration of time period.

The problem is that existing materials just can't store that much energy. Graphene, which could be stacked up to create vast expanses of surface area for electrochemical reactions, might revolutionalize.