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PREPARED BY :-
UPVITA PANDEY
A11123912006, B.TECH.
A M I T Y S C H O O L O F N U C L E A R S C I E N C E & T E C H N O L O G Y
S U M M E R I N T E R N S H I P
SMALL ANGLE NEUTRON
SCATTERING FROM
NANOPARTICLES
• BASIC PROPERTIES OF NEUTRON
• NEUTRON SOURCES
• NEUTRON SCATTERING
• SMALL ANGLE NEUTRON SCATTERING
• SANS INSTRUMENTATION
• APPLICATION OF SANS
• NANOPARTICLES
• EXPERIMENTS AND RESULTS
OUTLINE
WHAT IS
NEUTRON ?Chadwick’s Discovery of the Neutron
JAMES CHADWICK
Experimental demonstration of the neutron, 1932
Nobel Prize, 1935
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
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.
NEUTRON SOURCES
TYPES OF NEUTRON SOURCES
Continuous reactors
Spallation sources
Photo neutron sources
Pulsed reactors
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.
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.
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.
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.
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
Incident wave
Nucleus
The 1994 Nobel Prize in Physics – Shull & Brockhouse.
Neutrons show where the atoms…….
…and what the atoms do.
ELASTIC SCATTERING INELASTIC SCATTERING
TYPES OF SCATTERING
ik
fk
k q / 2
i fk k
4sin( )
2q
( )
dS q
d
Used to study structures
ik
fk
k q
i fk k
2
( , )d
S qd dE
Used to study dynamics
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.
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.
Summaries the use of various techniques of neutron scattering to determine various aspects of matter.
SMALL ANGLE NEUTRON SCATTERING
Small-angle neutron scattering is used to study
the structure on a length scale of 10 - 1000 Å.
sample
detector
2
ki
kfQ
Q = |ki-kf| = 4sin/
Q range ~ 0.001 - 1 Å-1
2 ~ 0.5 to 10 olow Q values ~ 4 to 10 Å
large wavelength small angles
THEORY OF SANS
2
r2 2
(( ) - ) ( ) ( )p m
d
dQ n V P Q S Q
2( ) ( )P Q F Qwhere Intraparticle structure factor
(depends on shape and size of the particles)
'
1( ) 1 exp[ .( )]k k
k k
S Q in
'Q R R
(decided by interaction between the particles)
Interparticle structure factor
n = number density of particles
V = volume of the particle
= scattering length density (p particle, m matrix)Rk’
Rk
Rk-Rk’
Information that can be obtained using SANS
Scattering intensityI (Q) = n V2 ( p - s)
2 P(Q) S(Q)
n = number density of particles
V = volume of the particle
= scattering length density (p particle, s solvent) }
P(Q) = |F(Q)|2 =Intraparticle structure factordepends on the shape and size of the particles }
S(Q) = Interparticle structure factor}
decided by the interaction between the particles
Number Density
&
Volume Fraction}
Composition
Shape, Size
&
Size Distribution
Interaction
&
Ordering
SANS INSTRUMENTATION
Guidetube Monochromator Collimator Sample Detector
BeO filter
Source slit3cm2cm
Sample slit1.5cm1cm
1m 3He PSD
Schematic of SANS instrument
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)
λcut-off 4.7Ǻ
λavg 5.2Ǻ
(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
distance
2m
Sample-to-detector
distance
1.85m
Angular divergence 0.5o
Detector Linear He3-Position
Sensitive Detector
Q range 0.017-0.350 Ǻ
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.
Applications of SANS
Small-Angle Neutron Scattering
Soft Condensed
Matter
Material Science
Biology
Superconductor
Flux Lines
ADVANTAGES DISADVANTAGES
Neutron scattering lengths varyrandomly with atomic no. and areindependent of momentum transfer
High penetration ability of neutrons
Right Q and right energy transfer forinvestigating both the structure anddynamics in condensed matter
Wide range of wavelengths can beachieved by using cold sources
As this is through nuclear reaction, thesignal 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
SMALL ANGLE NEUTRON SCATTERING
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.
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.
COMPARING NANOPARTICLES WITH OTHER SCALED LIVING AND NON LIVING THINGS
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 ParticleTracking•Contrast Agent For X-Ray
Nanodevices:NanotubesNanoporesDendrimersQuantum DotsNanoshells
APPLICATIONS OF NANOPARTICLES
EXPERIMENTS AND RESULTS
The sample of 1 wt% HS40, 1 wt% SM30and 1 wt% TM 40 nanoparticles forneutron scattering experiments wereprepared by diluting stock solutions inD20.
Characterization of Silica Nanoparticles using SANS
The wavelength (λ) of the neutronbeam used was 5.2 Å
The scattered neutrons from samples were detected using a 1m linear detector.
Dilute System
Characterization of Nanopaticles
Particle Mean radius
(nm)
Polydispersity
SM30 51.5 0.26
HS40 86.4 0.20
TM40 140.2 0.13
( ) ( )d
Q P Qd
2
3
3{sin( ) cos( )( )
( )
QR QR QRP Q
QR
0.017 0.1 0.30.01
0.1
1
10
50
Silica Nanoparticles
1 wt% SM30
1 wt% HS40
1 wt% TM40
d/d
(cm
-1)
Q (Å-1)
S(Q) for spherical particles
CHARACTERIZATION OF NANOPARTICLE USING DYNAMIC LIGHT SCATTERING
WHAT IS DYNAMIC LIGHT SCATTERING ?
• It determines the size of the particles from nanometer to few microns.Thesize of the particles is determined by measuring the random change in theintensity of the scattered light from a suspension.
• hydrodynamic diameter obtained by this technique is the diameter of asphere that has the same translational diffusion coefficient as the particle.
• the radius by using Stokes-Einstein equation is given by
d(H)=𝑘𝑇/3𝜋𝜼𝑫
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
1 10 100 1000 100000.0
0.2
0.4
0.6
0.8
1.0g2(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
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.