Figure 1S 500 nm 200 nm 2 μm

Figure 2S-1 (+)-Mode LDI-MS spectra obtained with a) acridine (M.W. = 179) and b) perdeuterated acridine dissolved in toluene. [Acridine+H] a) S/N [Acridine-d 9 +H] Mass(m/z) b) S/N Mass(m/z)

[d-Acridine+H] Mass(m/z) S/N Figure 2S-2 a) b) S/N Mass(m/z) [d-Acridine+H] LDI MS spectra were obtained from a)d- acridine dissolved into d-toluene and b) d-acridine dissolved into d-toluene:d-methanol=1:1.

Supporting Information SteelNSG NSG with 4-MBA NSG with 11-MUDA S/N (signal to noise) Standard deviation Relative Ratio  MW : g/mol  Conc. : 1.11 mg/ml  Voltage 20KV  80% grid  50ns delay time  50 shot  1933 Laser Intensity Steel NSG NSG with 4-MBA NSG with 11-MUDA [M+H] + Mass(m/z) S/N Mass(m/z) S/N Mass(m/z) S/N Mass(m/z) S/N Figure 3S-1

Supporting Information  MW : g/mol  Conc. : 1.27mg/ml  Voltage 20KV  80% grid  100ns delay time  50 shot  2457 Laser Intensity Steel [M+H] + Mass(m/z) S/N Mass(m/z) Figure 3S-2 SteelNSG NSG with 4-MBA NSG with 11-MUDA S/N (signal to noise) Standard deviation Relative Ratio NSG NSG with 4-MBA NSG with 11-MUDA S/N

Supporting Information  MW : g/mol  Conc. : 1.8mg/ml  Voltage 20KV  80% grid  100ns delay time  50 shot  2600 Laser Intensity Steel [M+H] + Mass(m/z) S/N Mass(m/z) S/N Mass(m/z) S/N Mass(m/z) S/N Figure 3S-3 SteelNSG NSG with 4-MBA NSG with 11-MUDA S/N (singnal to noise) Standard deviation Relative Ratio NSG NSG with 4-MBA NSG with 11-MUDA

Supporting Information  MW : g/mol  Conc. : 1.0mg/ml  Voltage 20KV  80% grid  100ns delay time  50 shot  2282 Laser Intensity Steel M+M+ Mass(m/z) S/N Mass(m/z) Figure 4S-1 SteelNSG NSG with 4-MBA NSG with 11-MUDA S/N (singnal to noise) Standard deviation Relative Ratio M+M+ M+M+ M+M+ NSG NSG with 4-MBA NSG with 11-MUDA S/N

Supporting Information  MW : g/mol  Conc. : 1.65mg/ml  Voltage 20KV  80% grid  10ns delay time  50 shot  1605 Laser Intensity Steel Mass(m/z) S/N Mass(m/z) Figure 4S-2 SteelNSG NSG with 4-MBA NSG with 11-MUDA S/N (signal to noise) Standard deviation Relative Ratio M+M+ M+M+ M+M+ M+M+ NSG NSG with 4-MBA NSG with 11-MUDA S/N

Supporting Information  MW : g/mol  Conc. : 2.4 mg/ml  Voltage 20KV  80% grid  100ns delay time  50 shot  2182 Laser Intensity Steel Mass(m/z) S/N Mass(m/z) Figure 4S-3 SteelNSG NSG with 4-MBA NSG with 11-MUDA S/N (signal to noise) Standard deviation Relative Ratio M+M+ M+M+ M+M+ M+M+ NSG NSG with 4-MBA NSG with 11-MUDA S/N

Improvements in (+)-mode LDI MS signal intensities were observed when citric acid and 11-MUDA were used together with a nanostructured gold surface in analyses of (a) acridine, (b) pyrazinecarboxamide, and (c) caffeine. The red and purple bars in (a), (b), and (c) correspond to the NSG surfaces and the NSG surfaces with the 11-MUDA layer and citric acid, respectively. Supporting Information Figure 5S-1 (a)(b)(c) S/N

Supporting Information  MW : g/mol  Conc. : 1.10mg/ml  Voltage 20KV  80% grid  10ns delay time  100 shot  1900 Laser Intensity NSG NSG with 11-MUDA NSG with 11-MUDA and Citric acid [M+H] + Mass(m/z) S/N Mass(m/z) S/N Mass(m/z) S/N Figure 5S-2 NSG NSG with 11-MUDA NSG with 11- MUDA and Citric acid S/N (signal to noise) Standard deviation Relative Ratio

Supporting Information  MW : g/mol  Conc. : 1.8mg/ml  Voltage 20KV  80% grid  100ns delay time  50 shot  2600 Laser Intensity [M+H] + Mass(m/z) S/N Mass(m/z) S/N Mass(m/z) S/N Figure 5S-3 NSG NSG with 11-MUDA NSG with 11- MUDA and Citric acid S/N (singnal to noise) Standard deviation Relative Ratio NSG NSG with 11-MUDA NSG with 11-MUDA and Citric acid