Structural Changes in Acetophenone Fluid Films as a Function of Nanoscale Thickness.

Area of Science:

• Surface Science
• Materials Chemistry
• Physical Chemistry

Background:

• Understanding fluid/solid interfaces is crucial for materials science and nanotechnology.
• Acetophenone films on silver substrates provide a model system for studying interfacial phenomena.
• Controlling film thickness is key to investigating confinement effects on molecular behavior.

Purpose of the Study:

• To experimentally observe the development of a fluid/solid interface.
• To investigate the relationship between acetophenone film thickness and molecular orientation.
• To compare experimental data with theoretical models of fluid film thickness.

Main Methods:

• Dynamic wetting technique to control fluid film thickness via substrate rotational velocity.
• Ellipsometry to determine absolute film thickness.
• Infrared reflection absorption spectroscopy (IRRAS) to analyze chemical environment and molecular orientation.

Main Results:

• Acetophenone film thickness varied from ~200 nm to 2 μm with substrate velocity (0.003–1.872 cm s^-1).
• Film thickness increase followed a Landau trend, proportional to velocity^2/3.
• Molecular orientation changes were observed with decreasing film thickness, indicating confinement effects.

Conclusions:

• Nanometer-scale confinement (<100 nm) induces significant molecular ordering in acetophenone films.
• The observed ordering in thin films resembles that of frozen acetophenone, suggesting solid-like behavior.
• Experimental findings align with theoretical predictions, validating the model system for interfacial studies.