CARACTERIZAÇÃO DE NANOPARTICULAS E NANOESTRUTURAS

Aula 10 QF933Instituto de Química

UNICAMP

Nanoparticles Characterization:Nanoparticles Characterization:

Measurement of the particles Measurement of the particles size by the PCS techniquesize by the PCS technique

MSc. Priscyla D. MarcatoDr. Nelson Durán

• If the particles or molecules are illuminated with a laser, the intensity of the scattered light fluctuates at a rate that is dependent upon the size of the particles

• Analysis of these intensity fluctuations yields the velocity of the Brownian motion and hence the particle size using the Stokes-Einstein relationship.

Principle of Measurement

Brownian Motion

Particles, emulsions and molecules in suspension undergo

Brownian motion.

This is the motion induced by the bombardment by solvent

molecules that themselves are moving due to their thermal

energy

Temperature and viscosity must be known

Intensity of the scattered light fluctuates

Intensity of the scattered light fluctuates

Small particles- noisy curve

Large particles- smooth curve

The velocity of the Brownian motion is defined by a property known as the translational diffusion coefficient (usually given the symbol, D).

Stokes-Einstein relationship

Zetasizer Nano ZS Malvern

He-Ne Laser = 633 nm

Determining particle size

Determined autocorrelation function

Depend

Correlation function Correlograms

Correlogram from a sample containing

large particles

Correlogram from a sample containing

small particles

Lowconcentration turbidity is linear with

concentration

High concentration

Particles are so close together that the scattered radiation is re-scattered by other particles.

Optical arrangement

in 173°

backscatter detection

Information

Size by:

- Intensity I d6

Rayleigh Scattering(For nanoparticles less than d =λ/10 or around 60nm

the scattering will be equal in allDirections-isotropic)

This particles will scatter 106 (one million) times more light than the small particle (8 nm)

The contribution to the total light scattered by the small particles will be extremely small

8 nm80 nm

8 80

- Volume d3

d1- Number

V= 4r3 r = d/2V= 4(d/2)3 = 4d3

8

By the Mie theory is possible convert intensity distribution into volume

Two population of spherical nanoparticles : 5 nm and 50 nm

(in equal number)

Which of these distributions should I use?

d(intensity) > d(volume) > d(number)

Direct determination of the number-weighted mean radius and polydispersity from dynamic light-scattering dataPhilipus et al., Applied Optics, 45, 2209 (2006)

We find that converting intensity-weighted distributions is not always reliable, especially when the polydispersity of the sample is large.

Reference

Dynamic Light Scattering:An Introduction in 30 Minutes, Malvern, http://www.malvern.co.uk/common/downloads/campaign/MRK656-01.pdf

HOMOGENEIZAÇÃO À ALTA PRESSÃO

Solução de tensoativo (quente)

(sob alta agitação)

Homogeneizado à alta Pressão

Ativo + Lipídio fundido

Moído (micropartículas lipídicas)

Micro-suspensão

Solução de tensoativo (fria)

AgitaçãoAgitação

Pré-emulsão

Homogeneização a quente

Solidificação(nitrogênio líquido)

Homogeneização a frio

• Rápido e Fácil

•Fácil escalonamento - 99% de reprodutibilidade em escala

industrial

• Evita contaminação no processo de homogeneização

Homogeneização à Alta Pressão

Espectroscopia de Correlação de Fótons

Espectroscopia de Correlação de Fótons

Diâmetro

Potencial Zeta

Espectroscopia de Correlação de Fótons

• Rápido e Fácil

•Fácil escalonamento - 99% de reprodutibilidade em escala

industrial

• Evita contaminação no processo de homogeneização

Dingler e Gohla, J.Microencapsul.19, 11-16 (2002).

500 bar 3 ciclos

Sakulkhul et al., Proceedings of the 2nd IEEE International ( 2007)

MICROSCOPIA ELETRONICA DE VARREDURA (SEM)