Table 3.
XPS high-resolution C 1s and S 2p chemical species for pure NTA and mixed NTA/OEG Monolayers on Au.a
| monolayer | time in NTA thiol | time in OEG thiol | carbon species percentage (std dev) | ||
|---|---|---|---|---|---|
| C-C, C-H | C-O,C-N, C-S, and β-shifted carbonsb | N-(C=O) and C-(C=O) | |||
| (285.0 eV) | (286.8 eV) | (288.9 eV) | |||
| theoretical carbon species percentages | |||||
| NTA thiol | 41.4 | 44.8 | 13.8 | ||
| OEG thiol | 50.0 | 50.0 | 0.0 | ||
|
| |||||
| experimental carbon species percentages | |||||
| NTA a | 24 hrs | -- | 47.9 (1.1) | 38.4 (0.9) | 13.7 (0.6) |
| NTA b | 5min | -- | 51.1 (0.7) | 36.4 (0.9) | 12.5 (1.1) |
| OEG 1 | 5min | 0.5 hr | 50.1 (0.7) | 42.0 (0.6) | 7.9 (0.9) |
| OEG 2 | 5min | 24 hrs | 48.3 (0.8) | 45.8 (0.3) | 5.9 (0.9) |
| Pure OEG | -- | 24 hrs | 48.6 (0.9) | 51.4 (0.9) | ndc |
a
All the data were taken at 0° take-off angle in the hybrid mode. The take-off angle is defined as the angle between the sample surface normal and the axis of the XPS analyzer lens
b
β-shifted carbon is C-(C=O)-N
c
nd: not detected