Ugh! Acetone. Why?

I would want to research the old protocol. When no literature reference is given for it, I'd likely consider it as gossip. A host of published protocols exist for other solvents (toluene or methanol) as well as for vapor deposition. Any of these must be better to avoid the issues with the high vapor pressure solvent.

I agree that anhydrous solvents should typically be used to avoid solution-phase cross-linking (condensation) at the expense of substrate-mediated chemisorption. Perhaps for acetone however the water is acting to keep the glass surface adequately hydroxylated at the expense of modestly increasing the degree of solvent-phase cross-linking. In the end, the only way to know the answer to your overall question is to find a literature reference that has done the study or to do the work yourself.

As a side note ... When the protocol works as needed and you can deal with the safety issues (high vapor pressure of noxious fumes), perhaps staying with what you have now is the best option. Otherwise, my best guess is that you should plan for about two weeks of dedicated study to satisfy yourself that any change you will make in your current silanation protocol works at least as well as your current approach.

The polymeric/polysiloxane coating of silica and glass with trialkoxy- silanes including APTES can be done from any polar solvent including 100% water. Due to hydrolysis trialcoxysilanes can be transformed to silatranes, which are even more soluble and reactive. It is all about right reaction condition (temperature, pH, concentration of silane). In you case the reaction includes quick adhesion of silanes in partly hydrolysed form followed by heating, which provides the formation of stable polysiloxane coating of the surface. The presence of both basic amino- groups and acidic -SiOH groups in partly hydrolysed APTES promotes the formation of polymeric layers at the surface due to intermolecular hydrogen bonding.

Hi,

The polymeric/polysiloxane coating of silica and glass with trialkoxy- silanes including APTES can be done from any polar solvent including 100% water. Due to hydrolysis trialcoxysilanes can be transformed to silatranes, which are even more soluble and reactive. It is all about right reaction condition (temperature, pH, concentration of silane). In you case the reaction includes quick adhesion of silanes in partly hydrolysed form followed by heating, which provides the formation of stable polysiloxane coating of the surface. The presence of both basic amino- groups and acidic -SiOH groups in partly hydrolysed APTES promotes the formation of polymeric layers at the surface due to intermolecular hydrogen bonding.

There are a number of different protocols, but clearly this is an old one. Depending on your process conditions you may simply want to use a 2% sol'n of APTES in ethanol with 0.5% water. However, there are other silanes that give similar results that are anhydrous see the link, which gives a background and has a practicals section on application recipes: https://www.gelest.com/themencode-pdf-viewer/?file=https://www.gelest.com:443/wp-content/uploads/Goods-PDF-brochures-couplingagents.pdf

Thank you all for your answers.

Jeffrey J Weimer , I don't see two peaks at 2929 and 2848 cm^-1, Do I success in my modified APTES on hydroxyapatite?

Văn Nhã Nguyễn Your specific question is off-topic and therefore inappropriate here. It is better when it would be deleted here and posted as a separate topic for the general audience.

Well,

please don't forget the anionic and cationic components even if EC amount reach 1 micromhos/ cm.

Regards

Article Analysis of silanes and of siloxanes formation by Raman spectroscopy

A brief study about reaction and condensation of silanes.