why not, If you use cryo-TEM

TEM give you an exact size and more accurate BUT Sometimes due to low contrast in TEM images the size measurement of the particles especially surface or coating layer could be underestimated. So, the hydrodynamic diameter which estimated by Zetasizer (DLS) is always greater than the size estimated by TEM.

I prefer both DLS and TEM for size estimation. DLS estimated hydrodynamic radius and TEM estimated projected area diameter after sample preparation on grid.

Typical micellar characterisation can be done in several ways (Microscopy, Scattering, Mechanical, Spectroscopic and Molecular Dynamic Simulations),

Scattering

(1) If you do not have a literature indication of typical size of your micellar system and even if you have, a first approach (more easily accessible) to characterize the size of the micelles would be to use Dynamic Light Scattering (DLS) to estimate the size, sometimes this can be difficult to characterize the size if your micelles are in a metastable or transition state and it might require you to make a range of dilutions of your sample to find out the actual micellar size.

(2) More advanced scattering techniques which could prove very useful to your characterization (size, packing parameters and micellar state) would be x-ray scattering or neutron scattering, with the latter to probably be more useful if the micellar size you have is >100 nm (Need specialized facilities for this).

Microscopy

(3) First, using simple optical microscopy, you might be able to see the micelles you are looking for with a high magnification objective.

(4) Confocal Microscopy is a less invasive technique, if a dye that could be trapped preferentially in your micelles, you might be able to see the micelles in 3D with very good resolution with a standard Confocal Microscope.

(5) Wet-AFM and Wet-SEM, could be valuable techniques also although the sample preparation and the special equipment for liquid visualization might not be easily available. And you have to be lucky that your micellar structures are not going to be destroyed or changed by the electron beam.

(6) cryo-TEM, is not usually available as it is a expensive instrument, and you might have difficulty seeing the micelles with it and more importantly, you have to make sure the correct preparation technique is used and you are not seeing artefacts of the freezing, drying, neither coating effects.

Mechanical

(7) Surface tension measurements

With this measurements you could find an important parameter about the formation of your micelles. This instruments (e.g. Kirbon delta-8 or others) allow the measurement of the critical micellar concentration (c.m.c.) which is the value at which your molecules start to form spherical micelles. There are other advanced ways of measuring the c.m.c. with other techniques.

(8) Rheology

Measuring the Viscosity of your sample might give you information about the inter-micellar interactions and micellar state of your sample with different conditions (e.g. pH, temperature, solvent, presence of salts).

Spectroscopy

(9) By Fourier transform infrared spectroscopy (FTIR) and NMR the molecular environment of your molecules can be probed and this might give you interesting information about the type of bonding between the constituents of your micelles and the micellar state. H-NMR chemical Shifts can give you a c.m.c. values and well and dipolar couplings could give you additional information.

Molecular Dynamics Simulations

This computations simulations could give you relevant information about the size of your micelles too and could be compared with the size measured by different techniques.

Dear Chao,

Hi!. Hope you will a couple of research articles on TEM analysis of micellar structures on my researchgate page - one in BBA and another in J Biosci. We used negative staining. Although magnetic resonace spectroscopy has also used by us in some other publication at this site.

Dear Chao,

Micelles are dynamic in nature and it is not possible to see them on a TEM grid unless you are using CRYO-TEM facility. DLS could be useful to get the direct value of the size. However, you can calculate the size of the micelle by simple Surface tension measurement and following the packing parameter calculation. Please refer to Jacob Israelachvili papers.

characterization of micelle DLS, FTIR, TEM and Flurocence microscopy.

Chao Wang @

TEM cannot be used to characterize micelles. When preparing a dry sample, they will disintegrate. Cryo-TEM will give some idea of the micelles, but as the temperature decreases, they change their shape or size. The best methods are small-angle X-ray or neutron scattering.

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