CARACTERIZAÇÃO DE NANOPARTICULAS E NANOESTRUTURAS Aula 10 QF933 Instituto de Química UNICAMP

Nanoparticles Characterization: Measurement of the particles size by the PCS technique MSc. Priscyla D. Marcato Dr. Nelson Durán

Principle of Measurement 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.

Temperature and viscosity must be known 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

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

He-Ne Laser  = 633 nm Zetasizer Nano ZS Malvern

Determining particle size Determined autocorrelation function Depend

Correlation function Correlograms

Correlogram from a sample containing large particles Correlogram from a sample containing small particles

turbidity is linear with concentration Low concentration 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

Directions-isotropic) Information Size by: - Intensity I  d6 Rayleigh Scattering (For nanoparticles less than d =λ/10 or around 60nm the scattering will be equal in all Directions-isotropic)

8 nm 80 nm 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 80

By the Mie theory is possible convert intensity distribution into volume V= 4r3 r = d/2 V= 4(d/2)3 = 4d3 8 - Volume  d3 - Number  d1

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 data Philipus 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

Homogeneização a quente Ativo + Lipídio fundido Homogeneização a frio Homogeneização a quente Solidificação (nitrogênio líquido) Solução de tensoativo (quente) (sob alta agitação) Moído (micropartículas lipídicas) Agitação Pré-emulsão Solução de tensoativo (fria) Micro-suspensão Homogeneizado à alta Pressão

Homogeneização à Alta Pressão Rápido e Fácil Fácil escalonamento - 99% de reprodutibilidade em escala industrial Evita contaminação no processo de homogeneização

Espectroscopia de Correlação de Fótons

Espectroscopia de Correlação de Fótons Diâmetro

Espectroscopia de Correlação de Fótons Potencial Zeta

Fácil escalonamento - 99% de reprodutibilidade em escala industrial 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)