sometimes, I see some vapor/fumes being released from the glass container (tightly closed, original glass bottle from sigma) in which Trichloro(octadecyl)silane is being stored. Also, I notice that the solution being polymerized after few weeks. what are the handling/safety procedures that should followed?
It is very difficult to avoid polymerization of this material. The vapor rising is probably a combination of HCl and/or water vapor produced as the OTS reacts with the silanol sites and chemisorbs to the glass. I normally try to react the silanol sites on the glass with hexamethyldisilazane (HMDS) before storing OTS in a glass bottle. Clean the bottle first with a 30 min treatment in 1:1 v/v HCl/methanol. Rinse 3 times with deionized water. Then treat the bottle with concentrated sulfuric acid for 30 min. Rinse 3 times with deionized water. Place the bottle containing the last water rinse in warm (~90 degrees C) water bath for about an hour- this will maximize the number of surface silanol sites on the glass wall. Remove the bottle, pour out the rinse water, and add a bit of ~5/95 v/v HMDS/acetone to the bottle. Swirl the solution to coat the interior walls of the bottle. Lightly cap and allow to stand overnight in the fume hood. Remove and dispose of the HMDS/acetone as organic waste. Rinse the bottle interior 3 times with acetone and let it air dry in the hood. Bake the bottle at 100 degrees C for a few hours to complete the HMDS chemisorption and drive off any residual unreacted HMDS/acetone.
The interior of the bottle should now be hydrophobic with silanols capped by HMDS reaction. I distill OTS and fill the HMDS-reacted bottle in a DRY Ar glove box. Cap the OTS solution until needed for experiments. OTS will still continue to hydrolyze, although more slowly in the HMDS-treated bottle. It is always a good idea to redistill OTS immediately prior to use. NOTE: I also coat the interiors of my distillation glassware collection flasks with HMDS to limit OTS hydrolysis during collection of the OTS distillate. I use HMDS because it is a mono-silanol species that exhibits a 1:1 reaction with glass surface silanols, i.e., unlike OTS it does not polymerize and can only form a protective HMDS monolayer on the glass surface.
Easier way, not as effective of course, is just purge intensively flask with N2/Ar after every used. Additionaly, tape the flask with parafilm to improve tightness. It work quite good in our case.
Another solution (but not so convenient) is just keep flask in glove box etc. under N2/Ar.
Dr. Walter, thank you very much for the detailed explanation. I will try coating HMDS to the glass surface. I was unable to find a proper literature on silane (OTS) storage,so your method should be very useful.
Daniel, Thank you very much for the suggestion. I currently follow the same procedure i.e. injecting N2 in the glass container. unfortunately I notice white flakes on the bottle's neck and it starts polymerizing after 2-3 months (on regular usage).
Dr, Pawlak:
We've also tried bubbling N2 or Ar through OTS just prior to closing the bottle to limit OTS hydrolysis and polymerization during storage. One problem is that Ar or N2 tanks are filled by water pumping or oil pumping. So, the gas may have traces of water or oil in it. The water could cause OTS hydrolysis and polymerization. Oil could adsorb to surfaces, leading to less than ideal OTS chemisorption and SAM formation. We tried passing the N2 or Ar through filter beds (e.g., DRIERITE) to remove water/oil. This helps but we prefer to simply work in the glove box, where the inert gas is filtered and purified and dried by the box. Under these conditions, factors limiting the quality of OTS SAM deposited become the hydration level of the substrate surface and the level of trace water in the solvent used during OTS deposition.
Can you please suggest me disposing of OTS in Toluene Solvent?
Can i just dump into Organic Solvent disposal Tin?
Hi Krishna, you can store the toluene containing OTS in a separate glass bottles (which are meant for storing organic wastes with labels). later, whenever you have collected considerable amount of the solution, then you can give them to liquid waste disposal unit.
Never dispose organic wastes especially aromatic solvents in the sinks. It is hazardous.
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