We are trying to thermally evaporate quinolinic acid (2,3-Pyridinedicarboxylic acid) onto a gold crystal in UHV using a K-cell. We are having difficulty finding its sublimation temperature. Has anyone managed to deposit this molecule before using this method? If so, do you know its sublimation temperature?
Well, I haven't. But looking for its vapor pressure, I find the following:
" If released to air, an estimated vapor pressure of 6.1X10-6 mm Hg at 25 deg C indicates quinolinic acid will exist in both the vapor and particulate phases in the atmosphere. "
(source: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=6487)
Further information suggessts decomposition upon reaching the melting point around 228°C, or even below around 185..190°C (materials safety data sheets).
Good luck with your experiments
Well, I haven't. But looking for its vapor pressure, I find the following:
" If released to air, an estimated vapor pressure of 6.1X10-6 mm Hg at 25 deg C indicates quinolinic acid will exist in both the vapor and particulate phases in the atmosphere. "
(source: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=6487)
Further information suggessts decomposition upon reaching the melting point around 228°C, or even below around 185..190°C (materials safety data sheets).
Good luck with your experiments
I agree with Kai Fauth appears to have a pretty high vapour pressure at room temperature so a Knudsen cell may not be the best way of dosing. Whats your experimental set up e.g. bakeout etc. Perhaps a glass vial and freeze thawing (for purification) and a short tube with leak valve pointing at your sample. also what does the Mass spec say.
I have a second question, related, how do you handle it (apart from with care) Googling it doesn't really want me to go to near the stuff although MSDS says irritant category 2(3). How(who) will you clean the equipment etc.
Thank you both. The high vapor pressure is clearly going to be an issue and explains a lot of what we have seen in the past couple of days. I am a little cross with myself for not looking into that! I am in agreement that a K-cell at room temperature is not going to work. I think we will try this in the future on a different system with a cryostat so the sample can be cooled (we are after multilayer coverage).
It is not really an experiment I have had much involvement with until yesterday when I was brought in to assist with the use of the vacuum system. I was not around when the sample was loaded into the K-cell but I suspect the molecules would have been loaded into it in a fume hood and then the whole thing carried to the vacuum chamber. If you are interested I can find out?
Thanks again
Yes its good to know about different procedures etc that people have. Glove bags are also a good idea
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