Nanoparticles - PowerPoint Presentation

Slide1

NanoparticlesSlide2

A

particle is defined as a

small object that behaves as a whole unit with respect to its transport and properties.

NanoparticlesSlide3

According

to

diameterUltrafine particles (nanoparticles), 1-100 nmFine particles , 100 nm- 2.5 µm

Coarse particles, 2.5-10 µm

NanoparticlesSlide4

Suspensions of nanoparticles

are possible since the interaction of the particle surface with the solvent is strong enough to overcome density differences, which otherwise usually result in a material either sinking or floating in a liquid.

NanoparticlesSlide5

According to

morphology

Scientists have taken to naming their particles after the real-world shapes that they might represent.

NanoparticlesSlide6

Nanospheres

NanoparticlesSlide7

Nanorods

NanoparticlesSlide8

Nanoboxes

NanoparticlesSlide9

Nanoneedles

NanoparticlesSlide10

And more

have appeared in the literature

NanoparticlesSlide11

These morphologies sometimes

arise

SpontaneouslyTemplating

NanoparticlesSlide12

It All Starts with

Carbon

CarbonSlide13

If the ability of each atom to attract all those negatively charged electrons (called

electronegativity

) are reasonably close (that is, if the difference in electronegativity is no more than 2), then they can form covalent bonds.Because the electronegativity of carbon atoms is 2.5 (roughly in the midrange), they can form

strong, stable, covalent bonds with many other types of atoms with higher or lower values.

CarbonSlide14

What you fine at the tip of your pencil.

GraphiteSlide15

Graphite, is essentially

sheets of carbon atoms

bonded together into one huge molecule. GraphiteSlide16

Because the

only bonding between sheets

is the van der Waals’ force, the sheets slide easily over eachother. Drag the graphite across paper, and it leaves a trail of itself on the page.

GraphiteSlide17

Hydrogen

atoms hanging on only at the edges. GraphiteSlide18

GraphiteSlide19

FullereneSlide20

A fullerene is any

molecule

composed entirely of carbon, in the form of a hollow sphere, ellipsoid or tube.Fullerenes are

similar in structure to graphite, which is composed of stacked graphene sheets of linked

hexagonal rings

; but they may also contain

pentagonal

(or sometimes heptagonal) rings.

FullereneSlide21

Spherical

fullerenes

are: BuckyballSmallest member is C20 (unsaturated version of

dodecahedrane C20H20 )

and the most common is

Buckminsterfullerene (C

60

)

. C

70

, C

80

FullereneSlide22

The

first fullerene

molecule to be discovered buckminsterfullerene (C60).The name was homage to Buckminster Fuller

BuckminsterfullereneSlide23

The suffix "

-

ene" indicates that each C atom is covalently bonded to three others (instead of the maximum of

four), a situation that classically would correspond to the existence of bonds involving two pairs of electrons ("

double bonds

").

BuckminsterfullereneSlide24

While many of the atoms in

buckyballs

are connected together in hexagons (just as in graphite sheets), some of the atoms are connected together in pentagons.

Buckyball clustersSlide25

The

pentagons allow

the sheet of carbon atoms to curve into the shape of a sphere. Every buckyball surface contains 12 pentagons and 20 hexagons

.

BuckminsterfullereneSlide26

No

two pentagons share an edge (which can be destabilizing, as in pentalene C8H

6 ).

BuckminsterfullereneSlide27

Vaporizing

carbon

with a laser and allowing the carbon atoms to condense. Produce a very small

number of buckyballs.

Creating

buckyballsSlide28

Vaporized

carbon by placing two carbon electrodes close together and generating an

electric arc between them in a reaction chamber filled with a low pressure of helium or neon .generated much

larger quantities of buckyballs

Creating

buckyballsSlide29

Combustion

synthesis

Mixes a hydrocarbon with oxygen and burns the hydrocarbon

at a low pressure.

Creating

buckyballsSlide30

As antioxidants

C Sixty, Inc

. Using buckyballs in the real worldSlide31

A

free radical

is a molecule or atom that has an unpaired electron

which makes it very

reactive

.An antioxidant

is a molecule that can

supply an electron

and

neutralize a free radical

.

When a buckyball meets a free radical, the unpaired

electron in the free radical pairs

up with one of the

buckyball’s

delocalized electrons

,

forming a covalent bond

between the

free radical and a carbon atom

in the buckyball.

As antioxidantsSlide32

Buckyballs

are not naturally soluble in water, and therefore not soluble in the bloodstream.C Sixty has added a

water-soluble molecule to buckyballs.

Functionalization

Buckyballbased

antioxidants are several times

more effective

than antioxidants available

today.

Each buckyball-based antioxidant can

counteract several free radicals

because each buckyball has many carbon atoms for the free radicals to bond

to.

As antioxidantsSlide33

Antioxidant molecules currently in use can

only counteract one free-radical

molecule apieceAs antioxidantsSlide34

Drug

delivery Slide35

Drug delivery Slide36

Anti-aging

or anti-wrinkle creams Buckyball-based drug to fight arteriosclerosis.C Sixty is working on both

burn creams and an

HIV

drug.

Sony

is developing

more efficient fuel cell

membranes

.

Siemens

has developed a buckyball-based

light

detector

.

Additional

buckyball-based antioxidant type drugs Slide37

A type of buckyball which uses

boron atoms

, instead of the usual carbon, was predicted and described in 2007 by

Rice University scientists. Build

a "buckyball" using

silicon atoms , it would

collapse

.

Boron is nearby

(one atomic unit from carbon

)

Boron buckyball (B

80

)Slide38

Initial work with

60 boron

atoms failed to create a hollow ball that would hold its form.So another boron atom was placed into the centre of each hexagon

for added stability.

Boron buckyball (B

80)Slide39

With

each atom forming

5 or 6 bonds, is predicted to be more stable than the C60 buckyball.

Boron buckyball (B80)Slide40

B

80

is actually more like the original geodesic domeBoron buckyball (B80)Slide41

Spherical particles based on multiple carbon layers surrounding a buckyball core; proposed for lubricants.

NanoonionsSlide42

C20H10

. The molecule consists of

a cyclopentane ring fused with 5 benzene rings, so another name for it is Circulene

.

BuckybowlSlide43

Nanotubes Slide44

In

1991

Sumio Iijima placed a sample of carbon soot containing

buckyballs in an electron microscope

to

produce some photographs of

buckyballs

— which he in fact did — but some odd,

needleshaped

structures

caught his attention.

Nanotubes Slide45

Cylinders

of carbon atoms

that were formed at the same time that the buckyballs were formed.T

hese cylinders are each

a lattice of carbon atoms

— with each atom covalently bonded

to

three other

carbon atoms.

Nanotubes Slide46

like a sheet of graphite rolled into a cylinder

NanotubesSlide47

Some

of these cylinders are

closed at the ends and some are open.

Nanotubes Slide48

lattice can be orientated

differently

Nanotubes Slide49

Armchair

nanotubes, there is

a line of hexagons parallel to the axis of the nanotube.

NanotubesSlide50

Zigzag

nanotubes, there’s

a line of carbon bonds down the center.

Nanotubes Slide51

Chiral

nanotubes

, exhibit a twist or spiral (called chirality) around the nanotube.

Nanotubes Slide52

Single-walled

carbon nanotubes (SWNT) or

multi-walled carbon nanotubes (MWNT). Nanotubes Slide53

By adding

just a few percentage

of nickel nanoparticles to the vaporized carbon (using either the arc-discharge or

laser-vaporization) as

many nanotubes as

buckyballs or

even

more can be made.

Carbon

atoms

start

sweating

onto the

surface

of the

particle

and

bond together

,

growing a nanotube

.

When you

anchor one end

of the

growing nanotube

to the

metal nanoparticle

, it

can’t close into the sphere

shape of a buckyball.

Producing nanotubesSlide54

There are

three methods

that various companies have developed to produce carbon nanotubes in bulk quantities and at a lower

cost.

Producing nanotubesSlide55

high-pressure

carbon

monoxide deposition, or HiPCOInvolves a

heated chamber through which

carbon monoxide gas

and small clusters of iron

atoms flow. When

carbon monoxide

molecules

land

on the

iron

clusters, the iron acts as a catalyst and helps a

carbon monoxide

molecule

break up

into a

carbon atom

and an

oxygen

atom. The

carbon

atom

bonds

with

other carbon

atoms to

start

the

nanotube lattice

; the

oxygen

atom

joins

with

another carbon monoxide

molecule to form

carbon dioxide

gas, which then floats off into the air.

Producing nanotubesSlide56

Chemical-

vapor

deposition, or CVDA hydrocarbon — say, methane

gas flows into a

heated chamber

containing a substrate coated with

a catalyst

, such as

iron particles

. The temperature in the chamber is high enough to

break

the

bonds between

the

carbon

atoms and the

hydrogen

atoms in the methane molecules resulting in carbon atoms with no hydrogen atoms attached. Those

carbon

atoms

attach

to the

catalyst particles

, where they

bond to other carbon

atoms forming a nanotube.

Producing nanotubesSlide57

A

new

method uses a plasma process to produce nanotubes. Methane gas, used as the source of carbon, is

passed through a

plasma torch

. Nobody’s revealed the details of this process yet, such as what, if any, catalyst is

used?!

Producing nanotubesSlide58

They’re

really, really

strong.The tensile strength of carbon nanotubes is approximately 100 times greater than that of steel of the

same diameter.Young’s modulus

for carbon nanotubes, a measurement of

how much force it takes to bend a material

, is about

5 times

higher than

for

steel

.

The

properties of nanotubesSlide59

There are two things that account for this

strength:

carbon-to-carbon covalent bondsnanotube is one large

molecule, same as diamond.

The properties of nanotubesSlide60

Nanotubes are

strong

but are also elastic.This means it takes a lot of force to bend a nanotube, but the little guy will spring right back to its

original shape when you release it.

The properties of nanotubesSlide61

Carbon

nanotubes are also

lightweight, with a density about one quarter that of steel.

The properties of nanotubesSlide62

High

thermal

conductivity, more than 10 times that of silver.Metals depend upon the

movement of electrons to

conduct heat

.Carbon

nanotubes

conduct heat by the

vibration of the covalent bonds

holding the carbon atoms

together.

A diamond

, which is also a lattice of carbon atoms covalently bonded, uses the same method to conduct heat, so it’s also an excellent thermal

conductor.

The properties of nanotubesSlide63

A

little bit

sticky, The electron clouds on the surface of each nanotube provide a mild

attractive force between the nanotubes. This attraction is called

van der Waals’ force

.

The properties of nanotubesSlide64

Conducts

electricity

Nano-sensorsThe properties of nanotubesSlide65

Functionalization

Nano-sensorsSlide66

Functionalization

Nano-sensorsSlide67

NanobudsSlide68

Megatubes

are

larger in diameter than nanotubes and prepared with walls of different thickness; potentially used for the transport of a variety of molecules of different sizes.

Megatubes