7TH SEMESTER

26 –FBAS/BSPHY/F-10

BS-PHYSICS(NANOTECHNOLOGY)

INTERNATIONAL ISLAMIC UNIVERSITY ISLAMABAD

PHYSICS AT NANOSCALEPRESENTATION “INTRODUCTION TO

NANOTECHNOLOGY”

NANOTECHNOLOGY

NANOTECHNOLOGY???

Nanotechnology is the creation of the functional materials ,devices and systems through control of the matter on the nanometer scale and the exploitation of the novel phenomenon properties at that length scale .

(NASA)

NANOTECHNOLOGY is: Creation of useful materials, devices, and

systems through the manipulation of matter on nanometer scale.

NANOMETERSCALE

(1 -100)nm

NANOMETER…..???

10-9 m

NANOMETER: ONE BILLIONTH PART OF A METER IS CALLED

NANOMETER.

THE LENGTH EQUIVALENT TO TEN HYDROGEN OR FIVE SILICON ATOMS ALLIGN IN A STRAIGHT LINE.

SIZEA meter is about the distance from the tip of your nose to the endof your hand (1 meter = 3.28 feet).

Millimeter- One thousandth of meter.(10-3m)

Micron: a micron is a millionth of a meter (or) one thousandth of millimeter (10-6m)

Nanometer:

A nanometer is one thousandth of a micron (10–9m)(or) a billionth of a meter. ie.,one billion nanometers in a meter.

NANOTECHNOLOGY

- Generally nanotechnology deals with structures sized

between 1 to 100 nanometer in at least one dimension.

Ability to design systems with defined structure and function on the nanometer scale.

Involves developing materials, devices within that

size

NANOTECHNOLOGY CONT…Interdisciplinary area :

Biology, Physics, Chemistry, Material science, Electronics,

Chemical Engineering, Information technology

NANOTECHNOLOGY→ Nanotechnology is science, engineering, and

technology conducted at the nanoscale, which is

about 1 to 100 nanometers..

→ Nanoscience and nanotechnology are the study

and application of extremely small things and can be

used across all the other science fields, such as chemistry, biology, Physics.

Nanotechnology Plays by Different Rules

Normal scale Nanoscale

Evolution of TechnologiesPico/Femto

Technology

3000

NANOMATERIAL: A material which has at least one dimension in

the range of (1-100)nm is called nanomaterial.

Nanoscale materials are divided into three category,

1. Zero dimension – length , breadth and heights are confined at single point. (for example, Nano dots)

2. One dimension – It has only one parameter either length (or)breadth (or) height ( example: very thin surface coatings)

3. Two dimensions- it has only length and breadth (for example,nanowires and nanotubes)

4. Three dimensions -it has all parameter of length, breadth andheight. (for example, Nano Particles).

A material which has at least one dimension in the range of (1-100)nm is called nanomaterial.

NANOMATERIAL:

Quantum well

• It is a two dimensional system

• The electron can move in two directions and restricted in one direction.

Quantum Wire

• It is a one-dimensional system

• The electron can move in one direction and restricted in two directions.

Quantum dot

• It is a zero dimensional system

• The electron movement was restricted in entire three dimensions

Why called Quantum ?

• Because, the electronic property is quantized

• The spatial distance is very very small

substrateSemiconductor growth (single layer)

• Nanoparticles• Nanocapsules• Nanofibers• Nanowires• Fullerenes (carbon 60)

• Nanotubes• Nanosprings• Nanobelts• Quantum dots• Nanofluidies

Based on the size and shape, the Nano materials are classified as follows

In quantum dot all the three dimensions are reduced to zero

Quantum dot

Dimension Variation

• Cu - Opaque

• Pt, Au - Inert

• Al - Stable

• Au - Solid

• Si - Insulator

Materials at Micro scale

Materials at Nano scale

• Cu - Opaque → Transparent

• Pt, Au - Inert → Catalysts

• Al - Stable → Combustible

• Au - Solid → Liquid

• Si - Insulator → Conductor

• Composites made from particles of nano-size ceramics or metals smaller than 100 nanometers can suddenly become much stronger than predicted by existing materials-science models.

• For example, metals with a so-called grain size of around 10 nanometers are as much as seven times harder and tougher than their ordinary counterparts with grain sizes in the micro meter range.

• The Nano particles affects many properties such as Melting pointBoiling pointBand gapOptical propertiesElectrical propertiesMagnetic properties

• .Even the structure of materials changes with respect to Size

Why Nano changes the

properties of materials?

The properties of materials can be different at the Nanoscale for two main reasons:

First, Nanomaterials have a relatively larger surface area when compared to the samemass of material produced in a larger form.

Nano particles can make materials more chemically reactive and affect their strength orelectrical properties.

Second, quantum effects can begin to dominate the behaviour of matter at the Nanoscale

WHY NANO WILL CHANGE THE PROPERTIES OF

MATERIALS?

AT THE NANO SCALE THE PROPERTIES CHANGES DUE TO INCREASE IN SURFACE TO VOLUME RATIO.

Why Nano will change the properties of

materials?

Smaller size means larger surface area

0.5 1 2 3 4

1

2

3

4

5

6

R

S / V

0

7

8

9

10

11

12

5

R

Sphere• Volume, V = 4/3 π R3

• Surface Area, S = 4πR2

• Ratio S/V = 3 /RFor He atom, 2R = 0.1 nm. S/V = 6 × 1010

R S/V

3 1

2 1.5

1 3

0.5 6

0.25 12

0.125 24

The melting point decreases dramatically as the particle size gets below 5 nm

Source: Nanoscale Materials in Chemistry, Wiley, 2001

Melting Point

Band gap

The band gap is increases with reducing the size of the particles

Surface Area

The total surface area (or) the number of surface atom increases with reducing size ofthe particles

• For semiconductors such as ZnO, CdS, and Si, the bandgap changes

with size

- Bandgap is the energy needed to promote an electron

from the valence band to the conduction band

- When the bandgaps lie in the visible spectrum, changing

bandgap with size means a change in color

• For magnetic materials such as Fe, Co, Ni, Fe3O4, etc., magnetic properties are size

dependent

- The ‘coercive force’ (or magnetic memory) needed to

reverse an internal magnetic field within the particle is

size dependent

- The strength of a particle’s internal magnetic field can be

size dependent

07-FBAS/BSPHY/F-10

MECHANICAL PROPERTIES

MECHANICAL PROPERTIES Mechanical properties of nanomaterials may reach the

theoretical strength, which are one or two order of magnitude higher than that of single crystal in the bulk form .

The enhancement in the mechanical strength is simply due to the reduced probability of defects.

OPTICAL PROPERTIES

OPTICAL PROPERTIES In the classical sense, colour is caused by the optical

absorbtion of light by the electron in matter, resulting in the visibility of the complementary part of the light.

On the smooth metal surface, light is totally reflected by the high density of electron, no colour , this is a size dependent property.

MAGNETIC PROPERTY

MAGNETIC PROPERTY Magnetic properties of nano structured materials are

distinctly different from that of bulk materials e.g the coercive force or the magnetic memory needed to reverse an internal magnetic field changes with the changes in the size.

The internal magnetic field is also size dependent.

Ferromagnetism disappears and transfers to superparamagnetism in the nanometer scale range due to huge surface energy.

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