NANOMATERIALS

G V S R Pavan Kumar

Engineering applications

• Used as hydrogen storage medium, semiconductors, sensors, nano-biotechnology and bio medical engineering.

• Hydrogen can be stored in nanotubes of carbon in fuel cells.

• Carbon nanotubes can be replaced platinum catalyst in fuel cell.

• CNTs are the best medai for prodcution of electricity in fuel cells.

Introduction

• In recent years, nanoscale science and technology grown rapidly, with widespread applications in the fields of medicine, computing, electronics and scientific exploration.

• Nanoscale is usually defined as smaller than a one tenth of a micrometer in at least one dimension, though this term is sometimes used for even smaller materials.

Definitions

• NANOCHEMISTRY is the science of tools, technologies and methodologies for chemical synthesis, analysis and biochemical analysis performed in nanoliter to femtoliter.

• NANOPARTICLES are the particles within the size ranging from 1-50nm

• NANOMATERIALS are the materials having components within size less than 100nm

• A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre).

• It can be written in scientific notation as 1×10−9 m, in engineering notation as 1 E−9 m, and is simply 1 m / 1,000,000,000.

One dimensional nanomaterial called NANOLAYER

Two dimensional nanomaterial called nanotube

Quantumdots-3D nanomaterial

Carbon nanotubes

• These are discovered by S. Iijima in 1991• These are allotropes of carbon with

nanostructure with length-to-diameter ratio greater than 100,00.

• These are considered as sheet of graphite rolled into a cylinder.

• These have a very broad range of electronic, thermal and structural properties.

Single walled nanotubes(SWNTs)

• The diameter of SWNTs is 1nm, with a tube length of many millions of times longer.

• These can be obtained by wrapping a one-atom thick graphite into seamless cylinder.

• These are very important variety of nanotubes with ELECTRIC properties.

• Based on wrapping of graphene sheet these nanotubes are classified as

• Armchair (n=0),Zigzag (n=m),chiral

Multi-walled nanotubes (MWNTs)

• MWNTs consists of rolled layers of concentric tubes of graphite. The inter layer distance in multi walled nanotubes is approximately 3.3A.

• These exhibits both metallic and semi conducting properties.

• Russian Doll model:no of graphene sheets wrapped

• Parchment model:single sheet of graphene rolled in to no of layers like news paper.

Synthesis of carbon nanotubes

• ARC DISCHARGE METHOD• LASER ABLATION METHOD• CHEMICAL VAPOUR DEPOSITION METHOD

Properties of nanotubes

• STRENGTH: carbon nanotubes are the stiffest materials in terms of tensile strength and elastic modulous. Density of these tubes is 1.3-1.4g/cm3

• This property is due to the sp2 carbon-carbon bonds.

• Hardness of nanotubes was found to be the highest.

• ELECTRICAL properties of nanomaterials depend on the symmetry and unique electronic structure of graphene.

• If n=m (armchair) metallic• If n-m is multiple of 3 then the nanotubes are

semiconducting.• The atoms in these nanotubes posses great

vibrational properties.

In catalysis

• Catalysts having CNTS makes a reaction safer, milder and more selective.

• Theses can be used catalysts themselves or as catalyst additives or as catalyst supportive.

• CNTs along with ruthenium are used for the hydrogenation of cinnamaldehyde.

• And some chemical reactions are carried out in nanotubes.

Medicinal applications

• CNTs are used in drug delivery systems, health monitoring, bio-sensing methods and in disease treatment.

• Can be used in altering the function of immune cells.

• Can be used as multifunctional biological transporters.

FULLERENES

• A third and newly discovered allotrope of carbon after graphite and diamond is BUCKMINSITER FULLERENE named in the honor of American Architect Buckminster Fuller, with a chemical formula of C60 .

• C60 resembles the shape of domes designed by Fuller

Types of Fullerenes

• Spherical fullerenes: they look like a soccer ball and often called Bucky balls

• Cylindrical fullerenes: these are called carbon nanotubes or buckytubes

• Planar fullerenes: graphene is an example planar fullerene sheet

DOME built by Buckminster Fuller

Buckminster Fullerene

• Fullerenes are prepared by vaporizing graphite rod in a helium atmosphere. Mixtures of fullerenes are formed. These mixtures are separated by solvent extraction.

• Fullerenes are the class of closed cage carbon molecule characteristically containing 12 pentagons and a variable number of hexagons.

• The C60 attains a icosahedron shape with 60 vertices, 32 faces.

• Another elongated molecule is C70. • By trapping C60 R E Smaelly predicted that a

molecule with formula C240 called RUSSIAN ROLL exsists.

Properties

• These exists as discrete molecules• These are in mustered colored. • Soluble in common organic solvents• Dissolves completely in benzene forms a

magenta solution• These are very tough and with highest tensile

strength.• Thermally stable up to 600oC.

Applications

• Used as organic photo-voltaics• These can also be used as ferromagnets• Used as lubricants• It was found that these fullerenes are active

towards HIV-1 virus.• Alkali metal fullrides are used as

superconductors