Melissa Farmer

Year: Senior

Major(s):  Forensic Science, Chemistry

Mentor: Killelea, Daniel

Department: Chemistry & Biochemistry

Project Title: Determination of the Local Electronic Structure of Ag(111) in the Presence of Subsurface Oxygen

Project Abstract: In the study proposed here, the effect of subsurface oxygen (Osub) on the electronic structure of a silver (Ag) surface will be studied using Ultra High Vacuum Scanning Tunneling Microscopy (UHV-STM). Subsurface oxygen differs from adsorbed oxygen (Oad) in that it is located beneath the surface, instead of being bound onto the surface. It is believed that Osub plays a key role, not as a direct participant, but by weakening the bond between the Ag and Oad and making the Ag surface an ideal one for the epoxidation of ethylene to form ethylene oxide. This reaction is desirable because ethylene oxide is a valuable industrial intermediate used in the creation many important chemicals, including ethylene glycol, polyester fabrics, and detergents. However, even the optimized reaction suffers from significant losses of product to undesired side reactions. Osub may play a key role in maximizing efficiency further. I will use the atomic-resolved capability of UHV-STM to investigate how Osub moderates the reactivity of Oad by measuring the electronic structure of surface Ag atoms in the presence and absence of Osub. STM uses the quantum mechanical property of the tunneling of electrons between the sample and an extremely sharp tip with a point a single atom in width. This results in a current that is measured to generate topographic images of the surface. Various experiments will be conducted to view a pure silver surface, which will then be compared to ones with oxygen atoms present.