On Thursday November 24 2005 7:09 pm, M. G. Devour wrote: > I don't know why they're so pervasive either, but I can remember back > when I worked in research going to all sorts of trouble to try to > prepare TEM samples to supposedly visualize the particle size of iron > we were using to catalyze a certain chemical reaction. > > I spent days trying to spray an aqueous colloidal suspension we were > using onto a carbon film supported on copper TEM grids on a hotplate > with an airbrush... without destroying the microscopically thin film. > > The idea was supposedly to make sure the particles were sufficiently > isolated in the aerosol droplets, and the water eliminated quickly > enough that they would not have a chance to agglomerate. > > All I ever remember us getting from the TEM were wonderful pictures > of huge gnarled clumps that were indecipherable as to the size of > whatever particles they were made up of. > > In other words, folks, getting from isolated particles of silver > suspended in water to "particles" dried out on a surface is *NOT* a > trivial exercise. There's little reason to believe there's any > relationship between TEM photos and what's in the water. > > Unless the vendor describes sample preparation technique in detail, > there's really no way to know what's in the pictures. > > > If a TEM is not the right tool for the job, what is? Is there some > > other relatively readily available test which will show not only > > the amount of ionic silver present but actually measure the size/s > > of any silver ions present? > > Aren't some folks using visible/UV scanning spectrophotography > nowadays? The absorption of wavelengths of light is directly > correlatable with particle size directly in the unmodified > suspension. It'll give you particle size distribution. > > Be well, > > Mike D. > [Mike Devour, Citizen, Patriot, Libertarian] > [[email protected] ] > [Speaking only for myself... ]
Hi Mike, and thanks for your response. Your recounting of your personal experience in attempting to use a TEM has definitely added to my understanding of the tool/process and its shortcomings for our purposes. I'm currently trying to Google "measuring ions". So far I haven't found much other than measuring concentration. -- LTR Registered Linux user #280295 [email protected]
