Carbon Nanotubes Carbon Nanotubes were discovered by Mr

Carbon Nanotubes

Carbon Nanotubes were discovered by Mr. Sumio Ijima in the year 1991

Introduction l l l As there name suggests, these are cylindrical in shape and their diameter is around 1 nm which is approximately 50, 000 smaller compared to the diameter of a human hair. These belong to the structural family of fullerenes. These are made up of a single layered sheet of graphite known as graphene. Hence, they are allotropes of carbon.

Types Of Carbon Nanotubes l Single Walled Nanotubes ~ SWNT l Multi Walled Nanotubes ~ MWNT

SWNT These are made of a single sheet of graphene. l They can be classified into three types depending on the orientation of the C – hexagons in the tube……Zig Zag Nanotubes, Armchair Nanotubes & Chiral Nanotubes. l

Zig Zag Nanotubes In these type of nanotubes the hexagons are so arranged that their apex is parallel to the axis of the tube. l These are optically inactive. l

Arm Chair Nanotubes In these type of nanotubes the hexagons are so arranged that their apex is perpendicular to the axis of the tube. l These are optically inactive. l

Chiral Nanotubes Arranging the hexagons in any other way other than that in the zig zag or arm chair models gives structures to nanotubes which are chiral i. e. they have mirror images and can’t be superimposed. l These are optically active. l

SWNT ~ Compilation

MWNT These are prepared from either a single or many graphene sheets. l There structures can be postulated by the two models ~ Russian Doll Model & The Parchment Model. l

Russian Doll Model l In this model graphene sheets are arranged in concentric cylinders.

The Parchment Model l In this model a single graphene sheet is rolled over itself. It looks like a scroll.

Properties Of Carbon Nanotubes l l They possess the highest strength to weight ratio amongst all known materials. They are harder than steel but smaller than a single human hair. They are conductors of heat and electricity. They can be used to trap heat. Their electrical conductivity can be manipulated to a higher scale of variance depending upon molecules that combine with the carbon atoms.

Applications Of Carbon Nanotubes l l l l energy-storing electronic textiles artificial muscles catalyst supports nearly impenetrable bullet-proof vests and body armor hydrogen, ammonia, humidity, and pollution sensors DNA biosensors, immunosensors, and health monitoring sensors biological sensors, for applications such as: monitoring hydrogen levels in premature babies quality control in food production plants pollution monitoring in truck and auto engines biomedical sensors (small enough to pass through cells, and not trigger immune response)

Applications Of Carbon Nanotubes l l l biological and chemical warfare agent sensors semiconductor devices field-effect transistors (FET) field emission displays (FED) for large-area TV's advanced generation high resolution flat panel displays light emission devices silicon etching molecular electronics heat-conducting applications supercapacitors advanced reinforced composites conductive adhesives, coatings, caulks, paints, and sealants

Applications Of Carbon Nanotubes l l l l l advanced atomic force microscopes nano-motors and mechanisms nanoscale tools, such as tweezers sports equipment (tennis racquets, yacht masts, fishing rods, etc. ) earthquake-resistant buildings or towers frictionless, low-wear bearings and other nanoscale components solid lubricant or as additives as heat sinks to develop lightweight spacecraft parts

Nanowires NW

Introduction A nanowire is a wire of dimensions of the order of a nanometer. l At these scales, quantum mechanical effects are important — hence such wires are also known as "quantum wires". l

Types Of Nanowires Metallic ~ Ni, Pt , Au l Semi Conducting ~ In. P, Si, Ga. N l Insulating ~ Si. O 2, Ti. O 2 l

Properties And Applications Of Nanowires Semi Conducting Nanowires can be used to make transistors which can be used as switches or as amplifiers. l NW are ballistic conductors as the electrons can flow continuously inside them which eliminates the evolution of heat and wastage of energy. l They can be used as magnetic information storage mediums. l

Properties And Applications Of Nanowires They are used in energy conversion devices. l They can be used to construct logic gates. l Nanowire arrays are used in Field Emission Devices. l Their optical properties are intriguing which result in various applications. l Alike carbon nanotubes their electrical resistance can be manipulated. l