Let say we have a system containing many particles of two kinds A & B (B is present in larger fraction). Initially particles are homogeneously mixed. On switching-on some interaction among the A particles, the system evolves such a way that A particles aggregate to form small clusters in the background of B where aggregate size is directly dependent on strength of interaction. Now my question is, 'what is the best way to characterise this phenomenon quantitatively?
Try Electronspray ionization (ESI) Mass spectrometric analysis for the characterization of nano clusters. It will give you exact no of atoms in the clusters of same kind.
My system is in colloidal length scale and so I can image the clusters with optical microscope. Now how do I extract the cluster size or relevant length from image analysis?
Try out Dynamic light scattering (DLS) and zetapotential. They can give you important information on colloidal stability and aggregation interactions.
For a statistically robust analysis, Dynamic Light Scattering as suggested by Rajeev is probably the best option, but it does have a limit at about 2um or so. Beyond that, SEM or optical microscopy could be useful. To get information from an optical image should be straightforward. Just threshold your image in ImageJ, and the default Analyze particles option will give you the area of the particles which will be correlated to the cluster size. Remember to set the px-um scaling! See this:
http://microscopy.berkeley.edu/courses/dib/sections/04IPIII/particles.html
I was hoping to get answers related to parameters that can be extracted from these kind of optical micro-graphs. Something similar to power spectral density. What kind of image analysis should I look for?
It is difficult to accurately quantify, simply from SEM or TEM images, in your case lachit. The polymers in most cases melt during imaging, to avoid that, low accelerating voltage is required. But it compromises on resolution. If it's below 200 nm aggregates, anyways SEM won't be useful with conventional instruments available at Iisc.
Regarding image processing u can use ImageJ or digital micrograph softwares to analyze ur data.
DLS can also give u reliable hydrodynamic radii in nanoscale, if your colloids are stable within the time scale of measurements. Resolution of DLS is 30 nm - 3 um, where it is relatively accurate.
Since you are trying to identify interactions in the colloids, simple image processing is not useful. You look for Small angle scattering XRD or dynamic scattering measurements to firstly identify and then quantify the type of interactions. Optical images can only support your theory.
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