Apresentação em tema: "Nanoparticles Characterization:"— Transcrição da apresentação:
1 CARACTERIZAÇÃO DE NANOPARTICULAS E NANOESTRUTURAS Aula 10 QF933 Instituto de Química UNICAMP
2 Nanoparticles Characterization: Measurement of the particles size by the PCS techniqueMSc. Priscyla D. MarcatoDr. Nelson Durán
3 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 particlesAnalysis of these intensity fluctuations yields the velocity of the Brownian motion and hence the particle size using the Stokes-Einstein relationship.
4 Temperature and viscosity must be known Brownian MotionParticles, 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 energyTemperature and viscosity must be known
16 turbidity is linear with concentration Lowconcentrationturbidity is linear with concentrationHighconcentrationParticles are so close together that the scattered radiation is re-scattered by other particles.
17 Optical arrangement in 173° backscatter detection
18 Directions-isotropic) InformationSize by:- IntensityI d6Rayleigh Scattering(For nanoparticles less than d =λ/10 or around 60nm the scattering will be equal in allDirections-isotropic)
19 8 nm80 nmThis 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
27 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.
32 Homogeneização a quente Ativo + Lipídio fundidoHomogeneização a frioHomogeneização a quenteSolidificação(nitrogênio líquido)Solução de tensoativo (quente)(sob alta agitação)Moído (micropartículas lipídicas)AgitaçãoPré-emulsãoSolução de tensoativo (fria)Micro-suspensãoHomogeneizado à alta Pressão