Table I.
Equivalent elemental compositions in atomic percentage determined from XPS analysis of the OH and OMe SAMs on 14 nm, 40 nm and flat gold substrates along with the C/O ratios calculated from those values. The number in parentheses for the atomic percentage indicates the standard deviation from six measurements.
| Substrate | Element (at. %) | OH SAM | OMe SAM |
|---|---|---|---|
| 14 nm AuNPs | C | 59.6 (0.7) | 59.5 (0.8) |
| O | 17.8 (0.8) | 17.9 (0.7) | |
| S | 1.8 (0.2) | 1.6 (0.0) | |
| Au | 20.8 (0.3) | 21.0 (0.4) | |
| C/O ratio | 3.35 | 3.32 | |
| 40 nm AuNPs | C | 60.0 (1.3) | 59.9 (0.8) |
| O | 19.2 (0.8) | 19.5 (0.8) | |
| S | 1.4 (0.2) | 1.2 (0.1) | |
| Au | 19.4 (0.6) | 19.5 (0.5) | |
| C/O ratio | 3.12 | 3.07 | |
| Flat gold | C | 50.1 (0.7) | 47.8 (1.5) |
| O | 15.1 (0.4) | 13.3 (0.4) | |
| S | 1.3 (0.3) | 1.6 (0.2) | |
| Au | 33.5 (0.8) | 37.3 (0.9) | |
| C/O ratio | 3.32 | 3.59 |