I would like to know how we may confirm that the monolayer of APTES on the glass slide is uniform and/or that it is indeed a monolayer and not multi-layer coating of APTES? Even after sonicating the glass slide 5 times in ethanol as mentioned in prior literature, I see a white-colored precipitate after drying the silanized glass slide for 3 hr at 120 deg C. Also, the gold nanoparticles aggregate and deposit as clusters on the surface separated by micron distances, even if the colloidal suspension is sonicated prior to deposition. Does sonication induce aggregation? It must be noted that I used microscope glass slide instead of cover glass slide used in prior research. I would like to know why "cover glass slide" is preferred to "microscope glass slide" for chemisorption of gold nanoparticles?
You need to prepare a monolayer using the Langmuir -Blodget method and check its monolayer with an atomic force microscope.
Yuri Mirgorod Sir, Thanks for letting me know that AFM helps in confirming monolayer adsorption. Could you please provide an elaborate description of the Langmuir-Blodgett method or provide any reference for the same? The protocol that I follow includes immersing the cleaned glass slides in 10% APTES (in ethanol), brief sonication (~5 mins) to remove excess APTES, drying in oven at 120 deg C for 3 hrs and then incubating with colloidal gold for 24 hrs. If it is different from the above method, please let me know. Thanks!
Yuri Mirgorod Sir, Thank you! I did read about the Langmuir-Blodgett technique for gold nanoparticle assembly... However, it looks like it would form only a closely-packed "bed" of gold nanoparticles by virtue of the inherent tendency of gold nanoparticles to form a hexagonal structure... Is it possible to control the spacing between the nanoparticles? For example, separate them by few tens of nanometers...I have been trying to find relevant info, but have not found any yet.
You can press on the monolayer in different ways, that is, to obtain a layer on the plate, when the nanoparticles are far from each other. You need to try or search for such an experiment.Look at the work of our laboratory with barium titanate under the guidance of A. P. Kuzmenko.
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