If you prepare silica particle from hydrolyzing tetraetyoxysilane using the sol-gel method, the surface of silica particles are covered with SiOH (silanol) groups.  There are typically about several OH groups per 1 square nanometer.  Even if you heat the particle to near 1000oC, there are still surface SiOH groups, though the number of hydrogen bonded OH group substantially decrease and mostly free OH groups.  These OH groups, either hydrogen bonded or free OH, are hydrophilic.  Therefore, if you can keep the silica surface from contaminating from the atmospheric organic compounds, the surface of the silica should be hydrophilic.  The SiOSi groups are not exposed to the surface and thus widely believed hydrophobicity of the SiOSi will not contribute to the property.  Super hydrophobic property can be prepared even from hydrophilic materials, as long as you control the surface roughness.  Silica nano particles can create nano-surface roughness in the presence of other polymer matrix.  In such a case, wetting by water droplet can be influenced by the surface tension of the water and the angle of the nano particles.  Of course, if you treat the silica surface with compounds, such as silane coupling agents, you can make the outermost surface hydrophobic (use hydrophobic organofunctional group such as saturated aliphatic chains or fluorinated chains).  If you use tricoloro or trialkoxy silanes, multilayer adsorption results.  On the other hand, if you use monochloro or monoalkoxysilane, the hydrophobic portion of the silane will point to the air side as air is quite hydrophobic.  Furthermore, the mono functional silane will only cover the surface at the monomolecular layer, if you wash the surface treated surface with pure organic solvent.  Such surface treatment combined with nano surface roughness will make the surface quite hydrophobic.

If you prepare silica particle from hydrolyzing tetraetyoxysilane using the sol-gel method, the surface of silica particles are covered with SiOH (silanol) groups.  There are typically about several OH groups per 1 square nanometer.  Even if you heat the particle to near 1000oC, there are still surface SiOH groups, though the number of hydrogen bonded OH group substantially decrease and mostly free OH groups.  These OH groups, either hydrogen bonded or free OH, are hydrophilic.  Therefore, if you can keep the silica surface from contaminating from the atmospheric organic compounds, the surface of the silica should be hydrophilic.  The SiOSi groups are not exposed to the surface and thus widely believed hydrophobicity of the SiOSi will not contribute to the property.  Super hydrophobic property can be prepared even from hydrophilic materials, as long as you control the surface roughness.  Silica nano particles can create nano-surface roughness in the presence of other polymer matrix.  In such a case, wetting by water droplet can be influenced by the surface tension of the water and the angle of the nano particles.  Of course, if you treat the silica surface with compounds, such as silane coupling agents, you can make the outermost surface hydrophobic (use hydrophobic organofunctional group such as saturated aliphatic chains or fluorinated chains).  If you use tricoloro or trialkoxy silanes, multilayer adsorption results.  On the other hand, if you use monochloro or monoalkoxysilane, the hydrophobic portion of the silane will point to the air side as air is quite hydrophobic.  Furthermore, the mono functional silane will only cover the surface at the monomolecular layer, if you wash the surface treated surface with pure organic solvent.  Such surface treatment combined with nano surface roughness will make the surface quite hydrophobic.

thank you sir, I have decided to use Trimethoxy(methyl)silane as silane coupling agent. Hope it works well

I think you misunderstood the previous comment. The particles can be used to create a nanoscaled roughtness. Afterwards the well structured surface is modified by a hydrophobic silane resulting in a siloxane layer.

unfortunately I do not agree with the mentioned number relation for surfaces which are organic, ... For example what kind of bond can be observed if we use a R3SiOR and an surface which contains organic OH or a metallic surfaces with valence orbitals with much higher energy. Of course in prince of water no link in between the surface and the siloxane wil be observable. You might compare this with our results on modified Cu surfaces.

sir michael schmit, thank you for reply sir . which project should i refer for  results on modified cu surface. I couldnt find it sir

Normally we use SiO2 surfaces (silicon wafers). But for IRRAS (internal refection absorption spectroscopy) the coating have to be applied onto a copper coated wafer.

Sorry that I haven't mentioned the publication before. Researchgate works not very good with the Safari browser.

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