An approach towards electronic-structure engineering in two or three dimensions is to utilize chemically synthesized and assembled nanocrystals as building blocks. Nearly monodisperse and stable thiol encapsulated Au (Au-thiols) nanoparticles can be synthesized chemically, which show interesting properties. However, when such system is transferred or placed on solid substrate, reorganization can take place depending upon film-substrate interaction. The information about stability of a structure or evolution of a structure from another is important not only in understanding the processes involved but also for studying different properties and applications. The coupling between such particles is strongly dependent on the morphology of the assembled structure. That is why evolution of morphology can be utilized to monitor the coupling and stability.

Monolayer of gold-thiol nanoparticles, formed at the air-water interface of a Langmuir trough and at different surface pressure, has been transfered to Si surface using simple horizontal deposition technique. The structure and the stability of the transfered monolayer have been studied using two complementary techniques, namely, x-ray reflectivity (XRR) and atomic force microscopy (AFM). Network-like patterns of the in-plane aggregated nanoparticles have been observed through AFM. Electron density profiles, obtained from the time-evolution XRR measurements, clearly show the presence of instability in the transfered films, which in the late drying stage seems to form nanopatterns. The film deposited at high surface pressure shows clear patterns compared to others, suggesting clearly the strong role of initial deposition condition (surface pressure) in pattern formation through instability [published in Phys. Rev. E 80, 056204 (2009)].