I have done an experiment to coat AuNRs with mesoporous silica, now I need to find out if there's porous in the silica shell. I know that the Electron microscope can answer this quest, but it's time-consuming and needs a keen hand for sample preparation. Is there another way other than using EMs to verify that the gold nanorods are uniformly coated with mesoporous silica with porous in it?
Thank you in advance.
Hi Sandip,
What are the typical dimensions you're looking at, here ? I assume your AuNRs and coating are in the range < 100 nm ? If so, I think this would actually be a nice case study for SAXS. The challenge, here, is that the SAXS signal of some diluted solution of your coated nanorods will contain three contributions: this of the AuNRs, the coating (taken to be homogeneous) and the porosity (i.e. the SAXS signal will be the convolution of the 3 contributions).
A first way to tackle the problem would be to measure the pure AuNRs first in order to separate this contribution (you need to make sure that all the experimental conditions are as close as possible). Then, you "only" have the remaining two contributions and you should be able to build a correct analytical model to fit the data. Easier if you have an a priori knowledge for the initial parameters, e.g. from EM studies.
More interesting and more complicated to analyze would be to do an anomalous SAXS experiment about a gold absorption edge.
The "really" interesting feature of SAXS is that, if you have a good control over your AuNRs and coating size/thickness distribution, you could be very accurate about the porosity.
If you don't know much about SAXS, my advice: check the litterature and get in contact with someone from you chemistry or physics dpt who has some X-ray equipement ^^.
Good luck !
It also sounds like a good candidate for AFM, or Atomic Force Microscopy. There are a lot of table top AFMs around and the sample prep. is not too difficult. I don't know if you will be able to distinguish whether they are porous after they are coated, but it is a very quick experiment to try, and doesn't consume much sample. Be sure and look at some uncoated nanorods for comparison!
Looking at the hydrophobicity change of your particles before and after coating should be a way to at least distinguish whether the silica has been coated onto your particles. UV/vis and Raman of the particles could show a change as well. Also if you have access to a zeta sizer or a nanosight you can see if there is a change in particle size and surface charge.
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