Ultra‐Smooth, Chemically Functional Silica Surfaces for Surface Interaction Measurements and Optical/Interferometry‐Based Techniques.

Dobbs, Howard A.; Kaufman, Yair; Scott, Jeff; Kristiansen, Kai; Schrader, Alex M.; Chen, Szu‐Ying; Duda, III, Peter; Israelachvili, Jacob N.

The study of interfacial phenomena is central to a range of chemical, physical, optical, and electromagnetic systems such as surface imaging, polymer interactions, friction/wear, and ion‐transport in batteries. Studying intermolecular forces and processes of interfaces at the sub‐nano scale has proven difficult due to limitations in surface preparation methods. Here, we describe a method for fabricating reflective, deformable composite layers that expose an ultra‐smooth silica (SiO2) surface (RMS roughness < 0.4 nm) with interferometric applications. The robust design allows for cleaning and reusing the same surfaces for over a week of continuous experimentation without degradation. The electric double‐layer forces measured using the composite surfaces are within 10% of the theoretically predicted values. We also demonstrate that standard chemisorption and physisorption procedures on silica can be applied to chemically modify the surfaces; as a demonstration of this, the composite surfaces are successfully modified with octadecyltrichlorosilane (OTS) to study their hydrophobic interactions in water using a surface force apparatus (SFA). These composite surfaces provide a basis for the preparation of a variety of new surfaces, and should be particularly beneficial for the SFA and colloidal probe methods that employ optical/interferometric and electrochemical techniques, enabling characterization of previously unattainable surface and interfacial phenomena.

SILICA; SURFACE interactions; INTERFEROMETRY

Advanced Engineering Materials, 2018, Vol 20, Issue 2, p1

1438-1656

Academic Journal

10.1002/adem.201700630