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.