Submitted by Maggie Geselbracht / Reed College on Mon, 12/06/2010 - 17:19

Hey VIPEr Community,

I need your help! My senior thesis student is having some difficulties this year, reproducibly making V2O5 films via a sol-gel route.  The details of the synthesis are not important, but the key is that his films must "age" in a "wet" solvent environment before processing ("wet" in this context means isopropanol).  The method is to place the films, coated on a glass substrate and covered with a teflon-coated plastic cover slip, in a small dessicator that has a small beaker of isopropanol in the bottom.  If the atmosphere inside the dessicator becomes too saturated with iPrOH, and the films are left too long, they disappear.  If the films aren't aged long enough, the cover slip does not release cleanly in the next step and too much of the V2O5 film is ripped off.

My student thinks he is having difficulties achieving a reproducible vapor pressure of iPrOH in the dessicator depending on how long it has been closed up before use, lab temperature, etc.  What we need is some sort of nifty sensing device that we could use to figure out the current iPrOH vapor pressure in the dessicator.  Does anyone know of any simple colorimetric devices or molecules that might work here?



Nancy Williams / Scripps College, Pitzer College, Claremont McKenna College
Well, the problem with colorimetrics is that they ain't real quantitative, but Jones' reagent will sense iPrOH, and if it sees enough of it, will change from orange to green.
Mon, 12/06/2010 - 17:31 Permalink
Kyle Grice / DePaul University

Did you ever find a system that worked?  There has got to be a vaporchromic material out there that is reasonable to synthesis or buy.  What does CoCl2 do in the presence of isopropanol?  Its the indicator in drierite.

Maybe something based on TiO2?



Let us know if you figure something out, the detection of gases in an inert atmosphere is pretty interesting.


Dr. Kyle Grice


UCSD Kubiak Lab

Sat, 02/19/2011 - 15:39 Permalink
Clifford Rossiter / SUNY Potsdam

Good Day Maggie, 

A solution that might be available at your local pharmacy or Walmart would be the old fashion alcohol screening test such as Breathscan. These tests detect the presence of ethanol in exhaled air using the color change from the reduction of K2Cr2O7. This is calibrated against a color chart to determine concentration. I do not see why it would not work with isopropanol. Good Luck.




Fri, 02/25/2011 - 09:44 Permalink
Maggie Geselbracht / Reed College
Thanks for the suggestions!  In the short term, we have solved the problem by switching to acetone in the dessicator.  This keeps the gels "wet" but does not redissolve the films if left too long.  We already wash the gels in acetone in the next step, so hopefully this is not introducing a huge change in the chemistry.  And the first batch of films aged in the acetone chamber looked great!
Tue, 03/01/2011 - 02:17 Permalink