Hi Arun,

For SEM imaging, sample should be completely dry otherwise it is not feasible to maintain vacuum inside the specimen chamber of SEM. To make the sample completely dry and retain its original characteristics, sample needs to be processed. And sample processing varies from sample to sample.

As you want to observe granules formed over the blanket in UASB reactor, so your sample falls in the category of biological samples as the surface of granules is covered with aggregates of bacteria.

The commonly used protocol for biological samples involves chemical fixation with fixatives like glutaraldehyde followed by postfixation with OsO4. Then, dehydration of the fixed sample is done with increasing alcohol series. After that, dried sample is mounted on specimen stub using electrically conductive double-sided adhesive carbon-tape. Finally, the sample is sputter coated with Au nanoparticles in an ion-sputter coater (to make the sample electrically conductive) and viewed under Scanning Electron Microscope.

There are several intermediary steps and several modifications (like variation in processing time, voltage applied, vacuum pressure etc.) from the standard practice can be made according to your sample.

Electron Microscopy: Principles and Techniques for Biologists by Bozolla J.J and Russell L.D is the best guide for this.

Thanks,

Karamjeet 

I am not an expert in this theme but may be you can freeze dry the sample first and the do you experiment. Take care with sample manipulation for safety (and health) reasons.

The question is: what do you want to see? Which analysis do you want to perform?

If you would like to see granules as they are, try some SEM with water vapour and cooling stage (UniVac /LowVac with Peltier cooling stage). there you should prevent your granulates from drying.

If the vacuum is not a problem then try to see them as they are - dropcast on some substrate (e.g. piece of silicon wafer) and let it dry, Use lower primary energy to avoid charging. Or you can coat the specimen with few nm of metal (gold, platinum) to avoid charging efects.

If you want to do some 3D reconstruction, try embedding it or freze dry and use Cryo-FIB-SEM system.

There are many ways to image the sample, but you should be more specific about what you would like to see and what are the problematic parts of your system for the vacuum.

Hi Arun,

For SEM imaging, sample should be completely dry otherwise it is not feasible to maintain vacuum inside the specimen chamber of SEM. To make the sample completely dry and retain its original characteristics, sample needs to be processed. And sample processing varies from sample to sample.

As you want to observe granules formed over the blanket in UASB reactor, so your sample falls in the category of biological samples as the surface of granules is covered with aggregates of bacteria.

The commonly used protocol for biological samples involves chemical fixation with fixatives like glutaraldehyde followed by postfixation with OsO4. Then, dehydration of the fixed sample is done with increasing alcohol series. After that, dried sample is mounted on specimen stub using electrically conductive double-sided adhesive carbon-tape. Finally, the sample is sputter coated with Au nanoparticles in an ion-sputter coater (to make the sample electrically conductive) and viewed under Scanning Electron Microscope.

There are several intermediary steps and several modifications (like variation in processing time, voltage applied, vacuum pressure etc.) from the standard practice can be made according to your sample.

Electron Microscopy: Principles and Techniques for Biologists by Bozolla J.J and Russell L.D is the best guide for this.

Thanks,

Karamjeet