Reductive Desorption of SAMs

Similar to other fundamental studies on SAMs, alkane thiols on Au(l 11) have also been prevailing in electrochemistry with, however, aromatic thiols receiving increased attention. A major topic has been formation and stability of SAMs and 

SAM-coated and clean substrates can easily reach 20 j,C/cm, which means that a simple coverage calculation from charge associated with the desorption wave is flawed, as pointed out by Schneider and Buttry [137]. In this context it is worth noting that the diflerence in capacity between SAM-coated and dean electrodes is not only due to the introduction of a dielectric layer but depends also on the surface of the SAM and its interaction with the environment, that is, whether the surface exhibits some additional charges either due to ionic tail groups or due to speciflc interaction of the SAM with the electrolyte. 

In contrast to the detailed work on the Au(l 11) surface, desorption studies from the other low-index surfaces are scarce with, for example, MC9 and MC4/8 on Au(l 10) [45, 46] and MC4 [47] on Au(l 00). Compared to Au(l 11) thiols are more stable on Au(l 10) as reflected by a negative shift of the desorption peak by 200-300 mV, which was explained by the difference in the pzc for both surfaces [46]. N o obvious differences in the shape of the desorption peaks were found for Au( 1 0 0) compared to Au(l 11). Interestingly, for MC4 a higher thiol coverage compared to both MC4 on the Au(l 11) and MC2 Au(l 0 0) was concluded from the desorption studies. For polycrystalline surfaces the desorption signal is more complicated with additional features, possibly due to the presence of different crystallographic domains [94, 163, 164]. 

---

Also, reductive desorption of SAMs of such asymmetrical disulfides as butyl hexadecyl disulfide and decyl-2(perifluoro-hexyl)ethyl disulfide has been studied on Au(lll), using CV [168]. Peak potentials corresponding to electrochemical desorption waves of the adsorbed species were different from those obtained for monolayers... 

Voltammetry of the Reductive Desorption of SAMs Experimental Features... 

Fig. 16 Reaction-time dependence of the peak potential for the reductive desorption of SAMs. Toluene solutions containing 1 mol dm isocyanic acid n-butyl ester and 0.2 mol dm triethylamine were reacted with MPOH SAMs on Au(l 11) at room temperature. (Reproduced from Ref 111 by permission. Copyright The Japan Society for Analytical Chemistry.)...

---