The influence of contamination on compositional imaging of self-assembled monolayers by scanning force microscopy

Comparative Studies of Photoelectron Spectroscopy and Voltammetry of Ferrocene-Terminated Self-Assembled Monolayers Possessing Different Electron-Donating Abilities

“…Figure (a) shows Fe 2p spectra for each SAM. The Fe 2p 3/2 and 2p 1/2 signals for the Fc SAM were observed at 707.8 and 720.6 eV, respectively, in accordance with previous reports. ,− The lack of the signal at around 710 eV indicates that the ferrocene moiety is not oxidized and possesses electrochemical activity on the surface . Although the Fe 2p peaks for FcCO and OctFc SAMs were shifted to higher and lower binding energy, respectively, the ferrocene moiety of these SAMs was also not oxidized during SAM formation.…”

Electronic-State Changes of Ferrocene-Terminated Self-Assembled Monolayers Induced by Molecularly Thin Ionic Liquid Layers: A Combined Atomic Force Microscopy, X-ray Photoelectron Spectroscopy, and Ultraviolet Photoelectron Spectroscopy Study

“…35 The negligible signal at approximately 710 eV indicates that the ferrocene moiety is not oxidized 99,100,102 and is electrochemically active on the surface. 100 As in the case of Au 4f spectra, the peak intensities of Fe 2p spectra decreased upon IL adsorption. In addition, the peak positions for the FcCO and Fc SAMs were shifted to lower binding energies upon IL adsorption by ∼0.3 and ∼0.1 eV, respectively, which can be attributed to a more efficient screening of the excited core hole in the vicinity of adsorbed IL layers (the final-state effect).…”

“…This step-like shape is not common for usual XPS spectra, but it has been repeatedly reported for spin-polarized Fe compounds including ferrocenium derivatives. 29,99,100,106,115 Recently, Taylor et al reported the Fe 2p spectra of various bulk ILs composed of imidazolium cations tethering ferrocene or ferrocenium groups with usual anions such as TFSI or PF 6 , and they revealed broad and asymmetric peaks at approximately 710−715 eV for ferrocenium-containing ILs. 102 Although not mentioned in the literature, the common ferroceniumcontaining cations showed different Fe 2p peak shapes as a function of the anion species, indicating the high variability of the peak shapes with respect to the microscopic environments of ferrocenium moieties.…”

“…The Fe 2p 3/2 and 2p 1/2 signals for the ferrocene SAMs were observed at approximately 708 and 720 eV, respectively, and the peak positions were in accordance with typical values for ferrocene derivatives 30,33,36,98102 and the value in our previous report within experimental uncertainty (0.1 eV) 35 . The negligible signal at approximately 710 eV indicates that the ferrocene moiety is not oxidized 99,100,102 and is electrochemically active on the surface 100 .…”

“…87 where the photoelectron intensities are not correlated to the IL-deposition amount ( Figure 4(b)). 29,99,100,102,105,106 In general, it is known that the XPS Fe 2p spectra of ferrocenium compounds show broad and asymmetric peaks at a higher binding energy compared to those of ferrocene compounds. Because ferrocene and ferrocenium derivatives are diamagnetic (low-spin Fe(II)) and paramagnetic (low-spin Fe(III)) at room temperature, respectively, 107110 the complex 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Fe 2p spectral shapes of ferrocenium compounds are ascribed to the multiplet splitting caused by the exchange interactions between the unpaired valence electron and the unpaired core electron; 105,111 other factors such as spin-orbital and crystal-field effects 112,113 and final-state screening by cyclopentadienyl ligands 114 also contribute to the multiplet splitting.…”