I have prepared microgel particles whose size should be around 100-150 nm. I have filtered the sample with the help of 250nm filter. But when I am carrying out the dynamic light scattering experiments, I see that the particle size is around 300-350nm. I am assuming that the particles are aggregating. ( I have diluted the sample enough to carryout the experiment). Can any of you suggest some ideas so as to reduce the aggregation?
Hi, in our lab we use a a solution (0.5%) of an anionic surfactant as the dispersing media, to prevent agglomeration (requiring a correction for refractive index and viscosity). It works for a wide range of systems, but I would recommend you to find out what is the best dispersant for your particles.
Poly-phosphates are good anti-aggregation agents. They are used tp prevent agglomeration of particles when measuring particle size and distribution by laser scattering, for example.
Another thought: Microgel particles are deformable. I can well imagine that a 350nm gel particle could squeeze through a 250nm pore. Especially as you are measuring the hydrodynamic diameter, which includes the fluffy polymer coat at the edge of the particle. It's probably more like seaweed than a cricket ball :-).
Try to make temperature sweeps and monitor the change in size, if any. Temperature controls solvent quality; if you are at not-so-good or even poor solvent, you get unbalanced dispersion attractions that cause aggregation; at good solvent conditions, attractions are very weak and the particles disperse uniformly and nicely.
u can try using anionic surfactants or using ultrasonic.
u can try using anionic surfactants or using ultrasonic.
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