Dear Adam, we have used a similar pirhana treatment in the past, and stored the cleaned samples in deionized water after the cleaning procedure. At least we did not experienced any unwanted behaviour of the so-stored glass substrates. Hope this helps, good luck for your experiments, Dirk

Dear Adam, we have used a similar pirhana treatment in the past, and stored the cleaned samples in deionized water after the cleaning procedure. At least we did not experienced any unwanted behaviour of the so-stored glass substrates. Hope this helps, good luck for your experiments, Dirk

Dear Adam,

I would not recommend any storage of pre-cleaned glass. You have to use it right away for self-assembly. It is fine to store glass with open OH- for a short period of time (up to few hours) in DI water, or in the last solvent that you used to "wash out" pieranna. But in few days you will accumulate enough contamination on the surface even in DI water.

A side note: some thiols have to be pre-cleaned too!!!

yes the good kept glove-box should be suitable, specially if you will use Ar instead of N2, but not for a very long time. The dry N2 in my experience induce the static charge on hydroxyl-glass which could influence coming self-assembling.

Thanks guys!

I feel that storing is a tricky issue for piranha cleaned slides.. If u can get a clean water say 0ppm quality you can afford to take little risk by storing for 1-2 days..

I have a small thought..... why not store the slides in piranha itself till you need them for your deposition.. just before your deposition remove it from piranha and do the post-piranha cleaning and continue..!!!(i havent tried this yet)

Based on my experience, the easiest way for keeping a clean glass is using a dessicator. Glasses nicely stored in a dessicator will be good for over month. Another facile way for cleaning a glass slide in case you need it immediately is ozone (but you need a ozone generator or ozone cleaner). It's a small, simple, and powerfully guy. You just need to press buttons then it'll give you clean glass slide in several minutes.

Good luck.

dear Venkatesh Sri, you will just dissolve glass in pierana in days scale, Beside that there is a safety considerations, etc....so strongly not recommended

Jiao- yes dessicator is good idea, but I would not keep it for month as you have the backpressure of oil in the pump, which will penetrate in week scale in dessicator, even if you will have a N2 trap. For dessicator storage I would recommend to connect dessicator to Ar and Vacuo lines, repeat vacum/Ar gas 3 times and left the dessicator under Ar overpressure, this should be probably good for a week, if the dessicator is clean

I agree with Valimir, piranha will dissolve the cations from the glass, a swelling will occur, leading to the destruction of the glass structure. And the desiccators are usually containing so much dirt, even a dirty, unkempt glove box will be cleaner. Or you clean the desiccator as carefully as your samples - so this as well is not a trivial issue ... Life can be so complicated!

Thanks for the help guys.

When considering surface recombination of metals on glass, then it is not a question of organic chemical cross linkers, but mainly a question of surface mobility. and surface cleanliness.

And this can be achieved with smooth, very dense chemically stable passivized surface which can be achieved for instance with ta-C coatings.

Keep the fiber or supports in ultrapure water in closed flasks.

I quite agree with Vladimir and Jiao, I did put my glass in the pre-vaccum desiccator with dried silica gel, and it works quite well for months. However, it has to be noted out that another important parameter that has to be taken into account is the humidity. I do experienced that during the rainy season, the glass is easily devitrified, In this case, putting the Ar or N2 gas into the desiccator will prolong the storing process.

Hi your answers spurred a question for me. Does heating the slides to dry the water after cleaning affect the OH rich surface??

what kind of self-assembly you intend to peruse after getting the OH-groups? If it is critical to have the max amount of OH groups use Ar gas or dry N2 (make sure that it is dry, the bottom of N2 tanks used to have some water condensate). If you do not care about the density of OH-groups than you could use a heat gun to dry it, just make sure that you will not cover slide by dust

You can try to keep it under argon gas in a sealed container.

We wanted to coat a silica film on the glass slides using TEOS sol-gel by spin coating . I'm not sure if the OH group density effects the attachment of the film or not. But was curious if the heat treatment reduces the OH group density.. Thanks Vladimir and Maurizio

Dear Sruvenu, you are welcome, the heat treatment itself does not effect density of hydroxyl surface groups (you could heat substrates in clean air-free and dust free environment up to 400 C without changing this density). It is exposure to moisture and dust that change this density. if you spin-cast the sol-gel in clean room and in clean hood, I would restrain from heating the substrates, but if you use pierana and spin-coating in general lab with dust and moisture around, thank you might check heating as an option.

Run a simple test: compare slide after pierana, and dried by Ar or N2 and the other slide, which you treat by say heat-gun. Test the contact angle on these slides. if the surface is still hyrdophylic, than you could use the heat. If there will be dramatic changes in contact angle, than the answer will be no.

Never thought of such simple experiment. Thanks will definitely try it the next time I synthesize my films. Thanks so much.

I also agree with Vladimir on the storage: We often use glass/SiOx surfaces either cleaned by plasma or piranha and I would always recommend to do it fresh. We also store them under DI water for some hours, but say you plasma cleaned in the morning, one can see some difference in wetting properties often already in the evening of the same day, so we always use the samples at least on the same day after activation.

IS there any published article or any reference that talks about the effect of keeping glass slides in piranha for longer period of time???

please suggest me some references..

1) I support back the Michael recommendation on time gap between pierrana and self-assembly, that what I do too.

2) Venkatesh, it would be hard to find the reference on longer (how long?) period of time due to reasons discussed above, Why actually you intend to apply pieranna for a ;longer period of time? If you like to reduce the thickness of glass, you could use for example HF etching. It well developed technique for Si wafers, as it is used intensively in electronics. The rate of HF etching is few-to tens nm per minute (you could find very intensive literature on this topic),

Yes , i read about HF etching.. I just wanted to know the details of how piranha solution dissolves the glass.. I mean the mechanism, the result of dissolution on the surface characteristics of the glass and all that stuffs.

Is there any reports/references regarding this??

Venkatesh, so you question is "how pierana dissolves glass". I do not know for sure the exact response on this question and either I do not familiar with any short references on this topic., The discussion here were focused on surface chemistry, not on bulk etching. My guess that pierrana interact with glass as any other acid: it attack the Si-Si- bond and broke these by H2SO4 (in this respect the H2SO4 is just the weaker version of HF), Than the H2O2 ingredient of pierana promptly oxidize these bonds yielding OH-surface groups. generated hear obviously faciliatite the reaction. This information should be available in many textbooks on Organic Chemistry, but I could not recommend you any of textbooks that I used, as now students use a new textbooks. You probably require to read a chapter on interaction of acids with Silicon. In addition it was mentioned in our discussion that pierana washed out cations from the glass, I could not provide you more specific answer, as it it out of my research scope. good luck

Sorry for typo: read "generated heat" instead of "generated hear"

One advice: if you want reproducible results always clean fresh before use. I never clean and store! Always use directly after cleaning.

Cleaning the glassware needs to be followed by DI washing and nitrogen drying. Similar to what the semiconductor industry does every day. Vacuum sealing followed re-sealing after introduction of pure nitrogen should help you store your samples as long as you want.