Self-assembled monolayer desorption

Self-assembled monolayer desorption ionization mass spectrometry (SAMDI)... 

Valter B, Ram MK, Nicolini C (2002).Thermal desorption high-resolution mass spectrometry of mixed self-assembled monolayers on gold. Langmuir. 18 1535-1541. 

In principle, the neutral desorbed products of dissociation can be detected and mass analyzed, if ionized prior to their introduction into the mass spectrometer. However, such experiments are difficult due to low ejfective ionization efficiencies for desorbed neutrals. Nevertheless, a number of systems have been studied in the groups of Wurm et al. [45], Kimmel et al. [46,47], and Harries et al. [48], for example. In our laboratory, studies of neutral particle desorption have been concentrated on self-assembled monolayer targets at room temperature [27,28]. Under certain circumstances, neutrals desorbed in electronically excited metastable states of sufficient energy can be detected by their de-excitation at the surface of a large-area microchannel plate/detector assembly [49]. Separation of the BSD signal of metastables from UV luminescence can be effected by time of flight analysis [49] however, when the photon signal is small relative to the metastable yield, such discrimination is unnecessary and only the total yield of neutral particles (NP) needs to be measured. 

Ex situ measurements in the presence of dissolved oxygen have proved that the mixed monolayer was stable in the solution free of 6TG and guanine. Madueno etal. [Ill] have also studied adsorption and phase formation of 6TG on mercury electrode. At high potentials, the molecules were chemisorbed and were able to form a self-assembled monolayer. When the potential was scanned to more negative values, reductive desorption of the monolayer was observed. Cathodic voltam-metric peaks, which are typical of a 2D condensed phase transition, divided the potential window into two regions one, in which self-assembled monolayer was stable, and the second, in which a physisorbed state existed. 

Oh, S.-K, Nakagawa, M., and Ichimura, K. Self-assembled monolayers derived from calix[4]resorcinarenes exhibiting excellent desorption-resistance and their applicability to surface energy photocontrol. Chem. Lett., 349 (1999). 

Wilhelm, T. and Wittstock, G. (2001) Patterns of functional proteins formed by local electrochemical desorption of self-assembled monolayers. 

Self-assembled monolayers (SAMs) do not require assembly by mechanical compression. SAMs form from charged materials that have adsorption-desorption properties that promote self-assembly as shown in Fig. 19.1(b). The substrate is simply immersed in a dispersion of the chaiged materials, withdrawn, and rinsed. Films are held together with either strong ionic bonds or covalent bonds... 

Noh, J., Kara, M. Molecular-scale desorption processes and the alternating missing-row phase of alkanethiol self-assembled monolayers on Au(lll). Langmuir 17, 7280-7285 (2001)... 

Voltammetry of the Reductive Desorption of Thiol Self assembled Monolayers from Electrode Surface I 595... 

---