Hi,

You can use a DLS (Dynamic Light Scattering) instrument to check the nanoparticle dispersion. A simple TEM image can give a better idea about dispersion and uniformity.

The nanoparticle size and uniformity basically depend on the nature of synthesis route used (if you have used chemical methods). Main factors include the strength of reducing agent (NaBH4 is better for small-sized and uniform nanoparticles, provided you have optimized the concentration.), concentration of metal precursor salt, solvent type and concentration of surfactant or stabilizer used. It is better to do systematic iterations with these factors for better understanding or you can follow an already published route.Once the nanocrystals are formed, in principle, you cannot revert it back until and unless you convert them back into salt form by adding an oxidizer( depending on the nature of the metal).

For drug loading efficiency, you can refer this paper.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364390/pdf/12249_2012_Article_9782.pdf

I hope this helps. Good luck.

Dear Deepa,

Dispersion stability in nanofluids is a complex issue. It depends on the nature of nanoparticles used, nature of base fluid, use of surfactants, dispersion technique used etc.

I am assuming that you have used ultrasonication to disperse the nanoparticles in the base fluid. The effectiveness of sonication can be checked by comparing the particle size after sonication. DLS analysis will give you the hydrodynamic particle sizes present in the sample. 

To check uniformity of dispersion, you could use UV-vis spectrophotometry. If the nanoparticles are uniformly dispersed, the peak absorbency of the medium will remain same since, particles are evenly dispersed. As the particle settle down, or form aggregates, the absorbency will reduce. So by monitoring the peak absorbency of colloid, you could compare the dispersion of different samples and also compare stability with time.

Regarding improving the stability:

1) you need to optimize the process parameters such as sonication mode, duration, amplitude, surfactant type and concentration, etc.

2) As a precursor, measure the zeta-potential of the mixture, if it is above +25 mV or less than -25 mV, the mixture can attain good stability.

3) Try adjusting the pH for improving the zeta potential.

4) Use surfactants to promote steric repulsion among particles so that they will not form aggregates.

Good luck...

To know either the samples are of similar sizes or not you should go for DLS (Malvern Zetasizer Nano) that describes the hydrodynamic particle size and zeta potential also to show particles stability. Moreover, do TEM of your samples that describes the internal structure and morphology of particles with their sizes. But keep in mind it is not necessary that the results of DLS and TEM should be same.

To gain uniform size of particles, review/revise before process parameters and in-process parameters like pH, temp, stirring speed, reaction time, method of preparation, conc. of precursors, type and conc. of surfactant you used, sonication mode etc.

The dispersivity of a nanoparticle relates to drug loading in such way that if you have not gained uniform size particles then drug loading in nanoparticles will not be efficient

I prefer to use Laser-Doppler measurement device, from my experience it is better in resolution. SEM, TEM will only gove you some non-representative picture, but can also contribute some insight.

To make particles uniform, one needs to improve dispersion (or maybe the manufacturing method for the nanoperticles to begin with)

Thank you all. It was very much useful for me. I will proceed keeping these issues in mind before trying loading of the drug. Thank you again.