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2 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Let’s Get Small

Chris Hughes

Scott Paulson

Costel Constantin

SATURDAY MORNING PHYSICS


SPRING 2011

February 18, 2011

What is a nanometer?

This is a flea on Murray.
A flea is about 1
millimeter in size.

This is Murray. Murray is
about 1 meter in size

Fleas (and all
living things)
are made of
cells. A
typical cell is
about 1
micron

in size

Inside cells
we find
DNA. DNA
is, about 1
nanometer
across (but
can be very
long!)

1000 times
smaller

1000 times
smaller

1000 times
smaller

Why study
nano
-
physics?

Recent breakthroughs allow us to not only study, but also
CREATE (see the 10 micron long “
nanoguitar
”, with 50 nm wide
strings!) objects at the nanometer scale. At this size we find that
systems behave very different from their macroscopic
counterparts, and this will lead to exciting new technologies.
JMU’s
nanoscience

laboratories house
state of the art facilities
where students can create and study a wide variety of systems at
this length scale!



Material Properties: Continuum


Measure Bulk Properties


Electrical (Resistivity)


Mechanical (Strength)


Thermal (melting point)


Optical (color)


Material Properties: Atoms

Hydrogen Spectrum

Electron Density of C60

What is
Nano
?

Study of structure
where at least 1 and
usually 2
-
3 dimensions
are 1~100 nanometers
in size

Fluorescence of CdSe Nanocrystals

Why is
Nanoscience

Different?

Strength and Composites

Why is
Nanoscience

Different

Electronics

Why is
Nanoscience

Different

Chemistry (and Thermal)

Why is
Nanoscience

Different

Chemistry (and Thermal)

Why is
Nanoscience

Different

Chemistry


Number of atoms on surface?


Proportional to r
2


Number of atoms in volume?



Proportional to r
3

as


Reactivity depends on ratio of surface/volume


Proportional to r
2
/r
3

= 1/r


The smaller the sample the bigger surface/volume

Why Now?

Atomic Force Microscopy

Tools of the trade

What Can
Nanoscience

Do?

Lighter, more agile, fly longer
without refuel, hovers,
smaller, gather more
information (superior
sensors).

1947
-

10
0

Transistors

2004
-
10
8
Transistors



More is Different!


Imitating Nature


Nature creates useful
structures at the
nanoscale

all the time.

Nudelman
, F.;
Gotliv
, B. A.;
Addadi
, L.; Weiner, S. (2006).
"Mollusk shell formation: Mapping the distribution of
organic matrix components underlying a single
aragonitic

tablet in nacre".
Journal of Structural Biology
153 (2): 176.

Red Abalone

Nacre is 3000x stronger than the aragonite
it is made of…how?

Imitating Nature

Kalpana

S.
Katti
,
Dinesh

R.
Katti

and
Bedabibhas

Mohanty

(2010).

Biomimetic

Lessons Learnt from Nacre”, in
Biomimetics

Learning from
Nature
,
Amitava

Mukherjee

(Ed.), ISBN: 978
-
953
-
307
-
025
-
4,
InTech
,
Available from:
http://www.intechopen.com/articles/show/title/biomi metic
-
lessons
-
learnt
-
from
-
nacre

DNA


Nature’s most important polymer

DNA Origami


Because of the
complementarity

of DNA, it
can be used as a scaffold to
self
-
assemble structures on the
nano
-
scale.

DNA Origami


Top row, fol ding paths.
a, square;
b
, rectangle;
c
, star;
d
, disk with three holes;
e
, triangle with rectangular domains;
f
, sharp triangle with trapezoidal domains
and bridges between them (red lines in inset). Dangling curves and loops represent unfolded sequence. Second row from top, di
agr
ams showing the bend of
helices at crossovers (where helices touch) and away from crossovers (where helices bend apart).
Colour

indicates the base
-
pair index along the folding path; red
is the 1st base, purple the 7,000th. Bottom two rows, AFM images. White lines and arrows indicate blunt
-
end stacking. White brac
kets in a mark the height of an
unstretched

square and that of a square stretched vertically (by a factor >1.5) into an hourglass. White features in
f

are hairpins; the triangle is
labelled

as in Fig.
3k but lies face down. All images and panels without scale bars are the same size, 165

nm 165

nm. Scale bars for lower AFM imag
es:
b
, 1

m
;
c

f
, 100

nm.

Folding DNA to create nanoscale shapes and patternsPaul W. K.
RothemundNature 440, 297
-
302 (16 March
2006)doi:10.1038/nature04586

DNA Origami


a, Model for a pattern representing DNA, rendered using hairpins on a rectangle (Fig. 2b).
b
, AFM image. One
pixelated

DNA turn (100

nm) is 30 the size of an actual DNA turn (3.6

nm)
and the helix appears continuous when rectangles stack appropriately. Letters are 30

nm high, only 6 larger than those written
using STM in ref. 3; 50 billion copies rather than 1 were
formed.
c
,
d
, Model and AFM image, respectively, for a hexagonal pattern that highlights the nearly hexagonal pixel lattice used in a

i
.
e

i
, Map of the western hemisphere, scale 1:2
10
14
, on a rectangle of different aspect ratio. Normally such rectangles aggregate (
h
) but 4
-
T loops or tails on edges (white lines in
e
) greatly decrease stacking (
i
).
j

m
, Two
labellings

of
the sharp triangle show that each edge may be distinguished. In
j

u
, pixels fall on a rectilinear lattice.
n

u
, Combination of sharp triangles into hexagons (
n
,
p
,
q
) or lattices (
o
,
r

u
).
Diagrams (
n
,
o
) show positions at which staples are extended (
coloured

protrusions) to match complementary single
-
stranded regions of the scaffold (
coloured

holes). Models (
p
,
r
)
permit comparison with data (
q
,
s
). The largest lattice observed comprises only 30 triangles (
t
).
u

shows close association of triangles (and some breakage).
d

and
f

were stretched and
sheared to correct for AFM drift. Scale bars:
h
,
i
, 1

m
;
q
,
s

u
, 100

nm.

Folding DNA to create nanoscale shapes and patternsPaul W. K.
RothemundNature 440, 297
-
302 (16 March
2006)doi:10.1038/nature04586

Toward Better Circuits?


Working with the
CalTech

group,
researchers at IBM
Almaden

Res.
Center are
developing ways of
using DNA self
-
assembled
structures as
templates for
microelectronics.

http://www
-
03.ibm.com/press/us/en/pressrelease/28185.wss

DNA Origami


From
http://www.physics.ox.ac.uk/biophysics/turbe
rfield/images/tetrahedron.jpg

NanoDays/Making Stuff

When: 1
-
4 pm, on March 27
th
.

Where: Explore More Discovery Museum, Harrisonburg VA.


Local high school educators, JMU Nanotechnology faculty,

and the Explore More Discovery Museum are partnering for

the first annual
NanoDays

Celebration.


NanoDays

celebrations

will

combine

simple

hands
-
on

activities

for

children

with

events

exploring

current

research


for

adults
.



NanoDays

activities

demonstrate

different,

unexpected

properties

of

materials

at

the

nanoscale


--

sand

that

won’t

get

wet

even

under

water,

water

that

won’t

spill

from

a

teacup,

and

colors

that

depend

upon


particle

size
.

There

will

also

be

a

microscope

that

allows

you

to

"feel"

the

surface

of

materials

on

the

nanoscale
.