As Kristina mentioned, try to use around 20 mL of ethanol instead Toluene e 5 mmol of APTES, for a test, under stirring. It is less toxic and safer to use. Additionally, the use of ethanol also enables the silanization via dip coating. Few immersions for few seconds (10 to 30) followed by drying in furnace at 60 °C for 1 h may be enough to assure good silanization. To further improve the coating deposition try a pre-treatment of the substrate with piranha solution or KOH/ethanol solution. Besides clean the surface, they will activate it. Finally, since the amino group from APTES acts as a self-catalyst, it may exempt the use of catalyst, however, to further accelerate the hydrolysis and condensation process try to use 0.5 mol/L HNO3 (acid catalyst) or 0.5 mol/L NH4OH (basic catalyst) in double of stoichiometric volume of water used for hydrolysis and condensation. The use of one or another catalyst will impact over the morphology of the films.

I hope that helps you! Good luck!

Most of the silica silanization reactions are indeed carried out in borosilicate glassware (even at refluxing temperatures of toluene). You can later wash the glassware (e.g. any vial) in a base bath to dissolve any deposited layer and re-use it after thorough drying.

I am also working on this reaction, only my substrate is oxidized silicon surface. I use anhydrous ethanol (w >/= 99.8%) instead of toluene and I do my deposition in a plain beaker. I kind of seal the beaker with parafilm and then cover it with watchglass.

I use ethanol, because according to a paper attached here, it provides smoother surface. Toluene is also fine, but it gives somewhat different surface, depending on your later use. Ethanol is certainly greener :)

Hope this helps. Good luck!

M. Farooq Wahab what alkali would you use, concentration and for how long?

Also, if you use glass you will loose lots of your silicate because it will attach to the container walls.

 At room temperature, the rate of silanization is quite slow anyway, A glass container will not consume the silane significantly. 

A base bath  contains, KOH, water and 2-propanol. Be careful while cleaning glassware with this solution.

http://bnorthrop.faculty.wesleyan.edu/files/2009/09/CleaningGlassware.pdf

I am actually using 2% on toluene for functionalizing my glass slides.

Also I am immersing my glass slides for 2 hours at room temperature, how long do you usually leave them?

As Kristina mentioned, try to use around 20 mL of ethanol instead Toluene e 5 mmol of APTES, for a test, under stirring. It is less toxic and safer to use. Additionally, the use of ethanol also enables the silanization via dip coating. Few immersions for few seconds (10 to 30) followed by drying in furnace at 60 °C for 1 h may be enough to assure good silanization. To further improve the coating deposition try a pre-treatment of the substrate with piranha solution or KOH/ethanol solution. Besides clean the surface, they will activate it. Finally, since the amino group from APTES acts as a self-catalyst, it may exempt the use of catalyst, however, to further accelerate the hydrolysis and condensation process try to use 0.5 mol/L HNO3 (acid catalyst) or 0.5 mol/L NH4OH (basic catalyst) in double of stoichiometric volume of water used for hydrolysis and condensation. The use of one or another catalyst will impact over the morphology of the films.

I hope that helps you! Good luck!

Yes, my usual process is:

@Fabio - do you know if heating treatment contributes to better layer in terms of stability or structure of the layer? Is it necessary?

He heat the GS for drying, if you have a extremely clean oven and are not in a hurry you might do that instead of drying with N2. I prefer doing with gas because you can see if your GS is clean or not after piranha and functionalization.

By the way Kristina, I am using aminopropil trimethoxysylane as you, have you measured your contact angle?

No, I haven't done that yet, I am currently working on another approach.

I just thought of another article that I read that might be of interest to you. This group investigated influence of APTMS concentration on layer formation and its kinetics (among other things). They measured contact angle, too! The article is in attachment, hope it will be of help to you.

Hi,

you can make your silanization in glassware such as petri dishes. The best way should be to do it in a vapour phase, but you can also do your functionalization in solution. one of the most important thing is that you should do it in an anhydrous way.

If you want you can look at this article in which we optimize silicon (or silica) APTES silanization followed by succinic anhydride to have COOH groups on the surface.

If you want some more information fell free to ask.

Good luck

Alessandro

Article Optimization and characterization of a homogeneous carboxyli...

I've had great results using this gas phase method on glass and silicon (Admittedly it is for the triethoxy analogue, but in my experience most volatile silanes work - reaction times may be longer for less volatile compounds):

http://www.sigmaaldrich.com/technical-documents/articles/crp-guide/arget-atrp-procedure-for-pmma-polymer-brush-growth.html

It uses very little reagent, no solvent, it is fast, and I get very reproducibly low-roughness APTES coated silicon. I dedicated a vacuum dessiccator with a grease-less flange and use a communal vented lab oven for the annealing step.

Samples are cleaned pre-derivatisation first with piranha and then with ammonium:hydrogen peroxide. Washed with water, excess water removed using a stream of nitrogen followed by drying in a 130 C oven.

Good luck,

Jeppe Madsen

Hello everybody,

It would be nice of any of you can give an opinion regarding my experimental silanization process. I am using the Piranha cleaned glass substrates (contact angle 5°, after Piranha cleaning) for the silanization process. The silane I am using is N-trimethoxysilylpropyl. I add 1 mL of silane into 50 mL of de-ionized water and heat the solution with continuous magnetic stirring at 80°C for 30 mins. After that I rinse it with extensive water for 30 mins and gave supersonic bath treatment for 30 mins. I dried under these glass substrates under vacuum for 1 h at room temerpature. But unfortunately, the glass substrates were not rendered hydrophobic. I observed the contact angle of only 30° after silane treatment.

Can any body help/suggest me in this regard?

Thank you and BR,