small angle neutron scattering from nanoparticles.

1. SMALL ANGLE NEUTRON
SCATTERING FROM
NANOPARTICLES
PREPARED BY : -
UPVITA PANDEY
A11123912006, B.TECH.
AMITY SCHOOL OF NUCLEAR SCIENCE & TECHNOLOGY
SUMMER INTERNSHIP

2. OUTLINE
• BASIC PROPERTIES OF NEUTRON
• NEUTRON SOURCES
• NEUTRON SCATTERING
• SMALL ANGLE NEUTRON SCATTERING
• SANS INSTRUMENTATION
• APPLICATION OF SANS
• NANOPARTICLES
• EXPERIMENTS AND RESULTS

3. WHAT IS
NEUTRON ?
Chadwick’s Discovery of
the Neutron
JAMES CHADWICK
Experimental
demonstration of the
neutron, 1932
Nobel Prize, 1935

4. The Neutron has Both Particle-Like and Wave-Like
Properties
 Charge = 0; Spin = ½
 Mass = 1.675 x 10-27 kg
 Magnetic dipole moment: mN = - 1.913 mN
 Nuclear magneton : mN = eh/4pmp = 5.051 x 10-27 J T-
1
 Velocity (v), kinetic energy (E), wave vector (k),
wavelength (l),
 temperature (T).
 E = mnv2/2
= kBT = (hk/2p)2/2mn;
k = 2 p/l = mnv/(h/2p)
Neutron

5. WHY USE NEUTRON ?
 Neutrons interact through short-range nuclear interactions.
They are very penetrating and do not heat up (i.e., destroy)
samples. Neutrons are good probes for investigating
structures in condensed matter.
 Neutron wavelengths are comparable to atomic sizes and
inter-distance spacing. Neutron energies are comparable to
normal mode energies in materials (for example phonons ,
diffusive modes). Neutrons are good probes to investigate the
dynamics of solid state and liquid materials.
 Neutrons interactions with hydrogen and deuterium are
widely different making the deuterium labeling method an
advantage.

6. NEUTRON SOURCES
TYPES OF NEUTRON SOURCES
Continuous
reactors
Spallation sources
Photo
neutron
sources
Pulsed reactors

7. I. SPALLATION SOURCES
Beams of high kinetic
energy (typically 70MeV) H-ions
are produced (linear
accelerator) and injected
into a synchrotron ring to
reach much higher energies
(500-800MeV) and then
steered to hit a high Z
(neutron rich) target (W-183
or U-238) and produce
about 10-30
neutrons/proton with
energies about 1MeV. These
neutrons are then
moderated, reflected,
contained, etc., as is usually
done in a nuclear reactor.
Most spallation sources
operate in a pulsed mode.
The spallation process
produces relatively few
gamma rays but the
spectrum is rich in high
energy neutrons. Typical
fast neutron fluxes are 1015-
1016 n/sec with a 50MeV
energy deposition/neutron
produced. Booster targets
(enriched in U-235) give
even higher neutron fluxes.

8. MAJOR SPALLATION SOURCES IN THE
WORLD
-- IPNS (Argonne): 500MeV protons, U target, 12 μA (30
Hz), pulse width = 0.1μsec, flux = 1.5 x1015 n/sec,
operating since 1981.
-- SNS (Rutherford, UK): 800MeV protons, U target, 200
μA (50 Hz), pulse width = 0.27μsec, flux= 4 x 1016 n/sec,
operating since 1984.
-- WNR/PSR LANSCE (Los Alamos): 800MeV protons, W
target, 100 μA (12 Hz), pulse width =0.27μsec, flux = 1.5
x1016 n/sec, operating since 1986.
-- KENS (Tsukuba, Japan): 500MeV protons, U target,100
μA (12 Hz), pulse width = 0.07 μsec, flux = 3 x 1014 n/sec,
operating since 1980.

9. II. NUCLEAR REACTORS
Nuclear reactors are based
on the fission reaction of
U-235 (mainly) to yield 2-
3 neutrons/fission at
2MeV kinetic energies.
Moderators (D2O, H2O)
are used to slow down the
neutrons to thermal
(0.025eV) energies.
Reflectors (D2O, Be,
graphite) are used to
maintain the core critical.
Whereas electrical power
producing reactors use
wide core sizes and low
fuel enrichment (2-3% U-
235), research reactors use
compact cores and highly
enriched fuel (over 90%)
in order to achieve high
neutron fluences.
Regulatory agencies
encourage the use of
intermediate enrichment
(20-50%) fuel in order to
avoid proliferation of
weapon-grade material.

10. WORLD AROUND RESEARCH REACTORS
A short list of research reactors in the world follows:
 CRNL-Chalk River, Canada (135 MW),
 IAEBeijing,China (125 MW),
 DRHUVA-Bombay, India (100 MW),
 ILL-Grenoble, France (57 MW),
 NLHEP-Tsukuba, Japan (50 MW),
 NERF-Petten, The Netherlands (45 MW),
 Bhabha ARCBombay,India (40 MW),
 IFF-Julich, Germany (23 MW),
 JRR3-Tokai Mura, Japan (20 MW),
 KFKI-Budapest, Hungary (15 MW),
 HWRR-Chengdu, China (15 MW),
 LLB-Saclay, France (14MW),
 HMI-Berlin, Germany (10 MW), INSIDE THE REACTOR HALL, ILL
 Riso-Roskilde, Denmark (10 MW),
 VVR-M Leningrad, Russia (10 MW).
 The ILL-Grenoble facility is the world leader in neutron scattering after two major
upgrades over the last 20 years.

11. Incident wave
WHAT IS NEUTRON SCATTERING
?
The scattering of
neutrons occurs in
two ways, either
through interaction
with the nucleus
(nuclear scattering)
or through
interaction of
unpaired electrons
(and hence the
resultant magnetic
moment) with the
magnetic moment
of the neutron
(magnetic
scattering).
Scattered waves
Nucleus

12. The 1994 Nobel Prize in Physics – Shull &
Brockhouse.
Neutrons show where the atoms…….
…and what the atoms do.

13. TYPES OF SCATTERING
ELASTIC SCATTERING INELASTIC SCATTERING
i k
f k
kq
/2
ki  k f
4
sin( )
2
q
 

 ( )
d
S q

d


Used to study structures
i k
f k
k  q
i f k  k
2
( , )
d
S q

d dE
 

Used to study dynamics

14. COHERENT SCATTERING
Coherent scattering occurs when there is phase relationship among
scattered neutrons. This represents the scattering which can produce
interference thus provide structural information.

15. INCOHERENT SCATTERING
In incoherent scattering, scattered neutrons do not have a phase
relationship. This happens because of the difference in scattering
length of different elements even different isotope of the same
element have different magnetic ordering, will have different
scattering length.

16. Summaries the use of various techniques of neutron scattering to
determine various aspects of matter.

17. SMALL ANGLE NEUTRON SCATTERING
Small-angle neutron scattering is used to study
the structure on a length scale of 10 - 1000 Å.
sample
 2
detector
ki
kf
Q
Q = |ki-kf| = 4sin/
Q range ~ 0.001 - 1 Å-1
 ~ 4 to 10 Å low Q values 2 ~ 0.5 to 10 o
large wavelength small angles

18. THEORY OF SANS
2
r
( ) ( - )2 2 ( ) ( ) p m
d
d
Q n   V P Q S Q



2
where P(Q)  F(Q) Intraparticle structure factor
(depends on shape and size of the particles)
     ' Q R R
S Q i
'
1
( ) 1 exp[ .( )] k k
k k
n
Interparticle structure factor
(decided by interaction between the particles)
n = number density of particles
V = volume of the particle
 = scattering length density (p  particle, m  matrix)
Rk’
Rk
Rk-Rk’

19. Information that can be obtained using SANS
Scattering intensity
I (Q) = n V2 ( p - s)2 P(Q) S(Q)
n = number density of particles
V = volume of the particle
Number Density
&
Volume Fraction
}
 = scattering length density (p  particle, s  solvent) }
P(Q) = |F(Q)|2 =Intraparticle structure factor
depends on the shape and size of the particles }
S(Q) = Interparticle structure factor
}
decided by the interaction between the particles
Composition
Shape, Size
&
Size Distribution
Interaction
&
Ordering

20. SANS INSTRUMENTATION
BeO filter
Source slit
3cm2cm
Sample slit
1.5cm1cm
1m 3He PSD
Guide
tube Monochromator Collimator Sample Detector
Schematic of SANS instrument

21. SANS at
DHRUVA
DHRUVA is a 100MW
natural Uranium
reactor with peak
thermal neutron flux of
1.8 x 1014 n/cm2/sec,
tailor-made for neutron
scattering experiments
with tangential beam
holes, through-tube,
provision for separate
moderators for cold
and hot neutrons, guide
tube laboratories, etc.
INSTRUMENTS SPECIFICATIONS
Beam port Guide G1
λ*(guide cut-off) 2.2Ǻ
Monochromator BeO filter at liquid N2
temperature(77K)
λ4.7Ǻ
cut-off λ5.2Ǻ
avg (Δλ/λ) ~15%
Flux at sample 2.2 x 105 n/cm2/sec
Source slit 3cm x 2cm
Sample slit 1.5cm x 1cm
Source-to-sample
2m
distance
Sample-to-detector
distance
1.85m
Angular divergence 0.5o
Detector Linear He3-Position
Sensitive Detector
Q range 0.017-0.350 Ǻ

22. Components of Neutron Scattering Instruments
 MONOCHROMATORS
– Monochromate or analyze the energy of a neutron beam using Bragg’s law .
 COLLIMATORS
– Define the direction of travel of the neutron.
 GUIDES
– Allow neutrons to travel large distances without suffering intensity loss.
 DETECTORS
– Neutron is absorbed by 3He and gas ionization caused by recoiling particles
is detected.
 CHOPPERS
– Define a short pulse or pick out a small band of neutron energies.
 SPIN TURN COILS
– Manipulate the neutron spin using Lamor precession.
 SHIELDING
– Minimize background and radiation exposure to users.

23. Applications of SANS
Small-Angle Neutron Scattering
Soft
Condensed
Matter
Material
Science
Biology
Superconductor
Flux Lines

24. SMALL ANGLE NEUTRON SCATTERING
ADVANTAGES DISADVANTAGES
 Neutron scattering lengths vary
randomly with atomic no. and are
independent of momentum transfer
 High penetration ability of neutrons
 Right Q and right energy transfer for
investigating both the structure and
dynamics in condensed matter
 Wide range of wavelengths can be
achieved by using cold sources
 As this is through nuclear reaction, the
signal to noise ratio is high
 High installation and maintenance
cost
 Neutron sources are characterized by
low fluxes and have limited use in
investigations of rapid time dependent
processes
 Large amount of sample(1mm thick
and 1cm diameter) is required

25. WHAT ARE NANOPARTICLES ?
 Nanoparticles have a large surface area and this dominates the contributions made
by the small bulk of the material.
 They absorb greater amount of solar radiation.
 They produce quantum effects due t confinement of their electrons in
semiconductor particle.
 Surface Plasmon resonance in some metal particles.
 Super para-magnetic in magnetic materials.
 At elevated temperature, they possess the property of diffusion.
 They have the ability to form suspension because the interaction of the particle
surface with the solvent is strong enough to overcome density difference.

26.  Zinc oxide particles have been found to have superior UV blocking properties
compared to its bulk substitute i.e. they are used in the preparation of sunscreen
lotion.
 Nanoparticles have also been attached to textile fibers in order to create smart and
functional clothing.
 Particles (typically sub 10 nm) are used as a drug carriers and imaging agents in
biomedical field.
 Various types of liposome nanoparticles are currently used clinically as delivery
systems for anticancer drugs and vaccines.

27. COMPARING NANOPARTICLES WITH OTHER SCALED
LIVING AND NON LIVING THINGS

28. APPLICATIONS OF NANOPARTICLES
Applications of
Nanoparticles
A Vehicle for Drug
Delivery:
•Gene Gun
•Uptake By Cell
Sensors:
•Surface Plasmon
•Fluorescence
Quenching
•Gold Stains
•Electron Transfer
As a Heat Source:
•Hyperthermia
•Opening of Bonds
•Opening of Containers
Labeling &Visualization:
•Immunostaining
•Single Particle
Tracking
•Contrast Agent For X-Ray
Nanodevices:
Nanotubes
Nanopores
Dendrimers
Quantum Dots
Nanoshells

29. EXPERIMENTS AND RESULTS
Characterization of Silica Nanoparticles using SANS
The sample of 1 wt% HS40, 1 wt% SM30
and 1 wt% TM 40 nanoparticles for
neutron scattering experiments were
prepared by diluting stock solutions in
D20.
The wavelength (λ) of the neutron
beam used was 5.2 Å
The scattered neutrons from
samples were detected using a 1m
linear detector.

30. Dilute System
Characterization of Nanopaticles
50
10
1
0.1
0.01
Silica Nanoparticles
Particle Mean radius
(nm)
1 wt% SM30
1 wt% HS40
1 wt% TM40
Polydispersity
SM30 51.5 0.26
HS40 86.4 0.20
TM40 140.2 0.13
( ) ( )
d
Q P Q
d



2
 3{sin( QR )  QR cos( QR
)

 3

 
( )
( )
P Q
QR
0.017 0.1 0.3
d/d (cm-1)
Q (Å-1)
S(Q) for spherical particles

31. CHARACTERIZATION OF NANOPARTICLE
USING DYNAMIC LIGHT SCATTERING
WHAT IS DYNAMIC LIGHT SCATTERING ?
• It determines the size of the particles from nanometer to few microns.The
size of the particles is determined by measuring the random change in the
intensity of the scattered light from a suspension.
• hydrodynamic diameter obtained by this technique is the diameter of a
sphere that has the same translational diffusion coefficient as the particle.
• the radius by using Stokes-Einstein equation is given by
d(H)=푘푇/3휋휼푫
Where:-
d(H) = hydrodynamic diameter
D = translational diffusion coefficient
k = Boltzmann’s constant (1.3806 x 10-23 J/K)
T = absolute temperature
η = viscosity

32. 1 10 100 1000 10000
1.0
0.8
0.6
0.4
0.2
0.0
g2(t)
HS40 silica nanoparticles
TM40 silica nanoparticles
Delay Time (u Sec)
Particle hydrodynamic
radius
(nm)
Polydispersity
SM30 105 0.149
HS40 155 0.214
Auto correlation function
the size of HS40 is smaller than TM40
as diffusion is inversely proportional to
size of the particles

33. CONCLUSION
 Neutron is a very good probe for studying structure as well as dynamics of
materials. It also covers the large spectrum of length and time scales.
 SANS is a useful neutron scattering technique for studying the
materials on a length scale of 10 – 5000 Å.
 SANS gives information on structure and interaction of particles
dispersed in a medium.
 SANS signal depends on the product of the form factor P(Q) and structure
factor S(Q). Structural information are obtained through P(Q) and interaction is
determined by S(Q).
 SANS is used for variety of samples. Some of the special properties of the
neutrons make SANS useful to study samples in bulk, magnetic samples and
easy possibility in samples to vary the contrast.