Studies on the effect of electrode pretreatment on the coverage of self-assembled monolayers of dodecanethiol on gold by electrochemical reductive desorption determinationElectronic supplementary information (ESI) available. See DOI: 10.1039/c1an15642j

This paper examines the effect of five major pretreatments on the surface coverage Γ m of dodecanethiol self-assembled monolayer on polycrystalline gold electrode (C 12 SH-SAMs-Au). It is based on the electrochemical reductive desorption in the alkaline solution by cyclic voltammetry (CV). The five different pretreatment methods include: aqua regia pretreatment, reductive annealed pretreatment, UV/O 3 pretreatment, piranha reagents pretreatment and simple polishing pretreatment, and then all above pretreatments following the same procedure of electrochemistry cleaning. The experimental results show that the surface coverage Γ m for C 12 SH-SAMs-Au by the five pretreatment methods are: aqua regia pretreatment (8.0 × 10 −10 mol cm −2 ) ∼ reductive annealed pretreatment (7.8 × 10 −10 mol cm −2 ) > UV/O 3 pretreatment (5.0 × 10 −10 mol cm −2 ) ∼ piranha reagents pretreatment (4.1 × 10 −10 mol cm −2 ) ∼ simple polishing pretreatment (4.0 × 10 −10 mol cm −2 ). This indicates that Au surfaces pretreated by aqua regia and reductive annealing can achieve the best results, and the Γ m values obtained are consistent with the theoretical coverage values ( Γ m 8.0 × 10 −10 mol cm −2 ); however, the Γ m values for other three pretreatment methods (UV/O 3 , piranha reagents and simple polishing) are not satisfactory, obtaining only almost half of the theoretical Γ m value. Thus, we recommend aqua regia and reductive annealed pretreatments as the best methods for self-assembling the alkyl thiol monolayer (C n SH-SAMs-Au), whereas UV/O 3 , piranha reagents and simple polishing pretreatments are not recommended. The effect of five different pretreatments on the surface coverage Γ m of C 12 SH-SAMs-Au are studied and aqua regia and reductive annealed pretreatments are recommended.