We use a 1" diameter fused silica hemisphere (Hyperion Optics, Corning 7979, infrared grade) that is first rinsed in ultrapure water from a Milli-Q system (18.2 MOhm) and then placed in Nochromix solution (CAUTION: working with Nochromix solution should only be done after reading and understanding the appropriate MSDS sheets) for at least 1 hour before it is again rinsed with copious amounts of ultrapure water. Then the hemisphere is sonicated in methanol for at least 15 minutes, rinsed, sonicated for 15 minutes, and rinsed again, all with ultrapure water, and then dried using house nitrogen gas passed through a desiccator. The hemisphere is then plasma cleaned (Harrick Plasma) for about 30-60 seconds on "high" setting. The flow cell is then assembled by first dispensing ultrapure water into the flow cell, adding a Viton O-ring, and finally securing the cleaned hemisphere onto the sample cell using clamps.