caracterizaÇÃo de nanoparticulas e nanoestruturas aula 10 qf933 instituto de química unicamp
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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)