What is a Nanometer?
~1m
~ 1 km
Department of Materials Science and Engineering, Northwestern University
What is a Nanometer?
~ 10 mm
~1m
Department of Materials Science and Engineering, Northwestern University
~ 1 mm
What is a Nanometer?
~ 10 µm
~ 10 mm
Department of Materials Science and Engineering, Northwestern University
What is a Nanometer?
~ 1 µm
~ 10-20 µm
~10 mm
~ 1 mm
Department of Materials Science and Engineering, Northwestern University
What is a Nanometer?
~ 1 nm
~ 1 µm
Department of Materials Science and Engineering, Northwestern University
Viruses and Bacteria
Cyanobacterium thin section
(blue-green algae)
Human papillomavirus
~50 nm
~5 µm
Department of Materials Science and Engineering, Northwestern University
What is a Nanometer?
Department of Materials Science and Engineering, Northwestern University
Size & Scale
Reference Points
nano
10-9
micro
10-6
milli
10-3
(meter)
100
Department of Materials Science and Engineering, Northwestern University
kilo
103
What is nanotechnology?
Definitions of nanotechnology on the Web:
• Technology development at the atomic, molecular, or
macromolecular range of approximately 1-100 nanometers to
create and use structures, devices, and systems that have novel
properties.
plan2005.cancer.gov/glossary.html
• Anything that is made up of components that are fabricated at
the scale of 100 nanometers or less.
nue.clt.binghamton.edu/intro1_6.html
•the branch of engineering that deals with things smaller than
100 nanometers (especially with the manipulation of individual
molecules)
wordnet.princeton.edu/perl/webwn
Department of Materials Science and Engineering, Northwestern University
It matters how you slice it!
Slice into
smaller cubes
1cm
1cm
1cm
Area = 6 x (1 cm)2 x 1 cube
1mm
= 6 cm2
Area = 6 x (0.1 cm)2 x 1000 cubes
= 60 cm2
Department of Materials Science and Engineering, Northwestern University
1mm
1mm
It matters how you slice it!
7000
2
total surface area (m )
6000
5000
4000
3000
2000
1000
0
1.E-09
1nm
1.E-08
10
nm
1.E-07nm
100
1.E-06
1 µm
1.E-05
10
µm
cube edge
1.E-04
100
µm
11.E-03
mm
Department of Materials Science and Engineering, Northwestern University
11.E-02
cm
Lots of surface atoms!
0.5
0.45
Assuming surface atoms
within 0.1 nm of surface
fraction of surface atoms
0.4
0.35
0.3
0.25
Onset of “nanoscale”
0.2
0.15
0.1
0.05
0
1.E-09
1nm
1.E-08
10
nm
1.E-07
100 nm
1.E-06
1 µm
1.E-05
10
µm
cube edge
1.E-04
100
µm
11.E-03
mm
Department of Materials Science and Engineering, Northwestern University
11.E-02
cm
Materials Science & Engineering
ce
n
e
i
c
S
s
l
a
i
r
Mate
Processing
NanoStructure
Ma
Properties
ng
E
s
l
teria
g
n
i
r
e
ine
Department of Materials Science and Engineering, Northwestern University
Size-Dependent Properties
At the nanometer scale, properties become size-dependent.
For example,
(1)
(2)
(3)
(4)
(5)
(6)
Chemical properties – reactivity, catalysis
Thermal properties – melting temperature
Mechanical properties – adhesion, capillary forces
Optical properties – absorption and scattering of light
Electrical properties – tunneling current
Magnetic properties – superparamagnetic effect
Æ New properties enable new applications
Department of Materials Science and Engineering, Northwestern University
Surface Energy
Surface atoms possess more energy than bulk atoms.
Consequently, surface atoms are more chemically reactive.
Nanoparticles possess enhanced chemical reactivity.
Example: NASA is exploring aluminum nanoparticles
for rocket propulsion due to their explosiveness
Department of Materials Science and Engineering, Northwestern University
Nanoparticle Catalysts
Macroscopic gold is chemically inert.
Gold nanoparticles are used to catalyze
chemical reactions.
Example: Reduced pollution in oxidation
reactions (i.e., environmentally friendly)
Nanoparticle Catalysis Resarch Group, Tsukuba, Japan
http://unit.aist.go.jp/isc/english_ver/each_groups_e/nano-cat_e/nano-cat_e.htm
Department of Materials Science and Engineering, Northwestern University
Alka Seltzer Missiles
Water
Lid
Department of Materials Science and Engineering, Northwestern University
Mentos and Diet Coke
•
•
•
•
www.youtube.com/watch?v=5Zh1jYN2JPs
Part chemical (surfactant effect)
Part physical (nano-pores on the surface)
Lots of gas!!!
Department of Materials Science and Engineering, Northwestern University
Size-Dependent Properties
At the nanometer scale, properties become size-dependent.
For example,
(1)
(2)
(3)
(4)
(5)
(6)
Chemical properties – reactivity, catalysis
Thermal properties – melting temperature
Mechanical properties – adhesion, capillary forces
Optical properties – absorption and scattering of light
Electrical properties – tunneling current
Magnetic properties – superparamagnetic effect
Æ New properties enable new applications
Department of Materials Science and Engineering, Northwestern University
Macroscale Melting Temperature
At macroscopic length scales, the melting temperature of materials
is size-independent.
For example, an ice cube and a glacier both melt at the same
temperature (32ºF).
Department of Materials Science and Engineering, Northwestern University
Nanoscale Melting Temperature
Nanocrystal size decreases
surface energy increases
melting point decreases
e.g., 3 nm CdSe nanocrystal melts at 700 K compared to
bulk CdSe at 1678 K
Department of Materials Science and Engineering, Northwestern University
Predicted melting temperature reduction:
0
-50
∆Tm
-100
Gold, Tm=1336K
γs-l=0.132 J/m2
-150
-200
-250
-300
1.E-09
1nm
101.E-08
nm
1.E-07
100
nm
1.E-06
1 µm
1.E-05
10
µm
1.E-04
100
µm
Particel Size
Particle
Department of Materials Science and Engineering, Northwestern University
11.E-03
mm
Summary
• Because of the increasing surface-to-volume ratio, the fraction of
atoms at particle surfaces dramatically increases at the nanoscale
• Surface-dependent properties are therefore most evident at the
nanoscale, e.g., catalysis of chemical reactions
• One example of surface-dependent thermodynamic property
changes at the nanoscale is the dramatic decrease in the melting
temperature of nano- vs. macro-sized particles
• This Nano-Thermo Unit is dedicated to quantifying those
changes
Department of Materials Science and Engineering, Northwestern University