Propanethiol, adsorption

Such anion adsorption can be prevented by chemisorbing a mono-layer of a strongly adherent thiol molecule to the Au surfaces [97,98]. 1-Propanethiol (PT) was used here because the gold nanotubules can still be wetted with water after chemisorption of the PT monolayer [97].t The Em versus applied potential curves for an untreated and PT-treated gold nanotubule membrane, with KBr solutions present on either side of the membrane, are shown in Fig. 13. The untreated membrane shows only cation permselectivity, but the permselectivity of the PT-treated membrane can be switched, exactly as was the case with the nonadsorbing electrolyte (Fig. 12). 

It was pointed out that adsorption of propanethiol or hexanethiol occurs according to the following reaction (58) RSH —> RSads + H+ + e desorption can occur by an electrooxidation, RSads + 3H20—> RSO,H + 5H + + 5e. A comparative study of the amount of thiol adsorbed and the effect of this adsorption on hydrogen chemisorption showed that one molecule of thiol is adsorbed on one accessible platinum atom (58). 

According to Maxted (36), at low temperatures the molecule would be adsorbed through sulfur atom anchoring. Around this point the hydrocarbon chain could, thanks to its free rotation, inhibit adsorption over the whole adjacent surface. A comparison of the toxicities of hexanethiol and propanethiol shows that the ratio of these toxicities is exactly equal to the ratio of the surface area covered by the two molecules. 

Most of the linker molecular monolayers are stable over broad potential ranges, limited by reductive and oxidative desorption and cleavage of the Au-S bond. The adsorption process can be followed in real time through several intermediate phases, such as reported for cysteamine [38] (and 1-propanethiol [155]). The in situ STM images shown in Figure 2.6 thus offer an overall impression of the microenvironment for immobilized redox proteins in voltammetric action. ... 

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