The scanning tunnelling microscope (STM) has been used to study two quite different systems. First, the unsaturated hydrocarbons ethene and ethyne, chemisorbed on a silicon substrate, and secondly, a monolayer of 4,4'bipyridyl disulfide (PySSPy), chemisorbed on a gold single-crystal sphere, in pure water. The images of the hydrocarbons on silicon showed, at low coverages, random clusters of adsorbates, but at higher coverages, approaching saturation the molecules prefer to be adsorbed on alternate dimer sites.The in situ STM study of the PySSPy on gold, revealed that the monolayer exhibits a marked molecular alignment with specific sites on the gold surface. The periodic unidirectional array showed a separation of 46 f 3 8, with a corrugation of ca. 1.5 A.

O composto 5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) adsorve espontaneamente sobre ouro formando SAMs ("Self-Assembled Monolayers") que, de acordo com os resultados eletroquímicos e de STM ("Scanning Tunneling Microscopy"), contêm poros através dos quais as moléculas dos complexos [Fe(CN) 6 ] 4-, a dependência da corrente faradáica com o pH da solução eletrolítica permitiu o cálculo do pKa da molécula de Hpyt adsorvida sobre ouro (4,2). Os parâmetros termodinâmicos, H ads and G ads , para o processo de adsorção desta molécula foram estimados em -20,01 e -39,39 kJ mol -1 , respectivamente, utilizando-se o modelo de Langmuir. O processo redox da metaloproteína citocromo c foi estudado utilizando-se a SAM de Hpyt. A constante de velocidade heterogênea de transferência de elétrons foi calculada em 2,29 10 -3 cm s -1 .5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) spontaneously adsorbs on gold forming SAMs (self-assembled monolayers) that, based on STM (Scanning Tunneling Microscopy) and electrochemical data, contain pinholes through which [Fe(CN) 6 ] 4-and [Ru(NH 3 ) 6 ] 3+ probe molecules access the underlying gold electrode. For the former molecule, the dependence of the faradaic current on the electrolyte solution pH value allowed the evaluation of the surface pKa as 4.2. The thermodynamic parameters H ads and G ads for the Hpyt adsorption process could be described by the Langmuir model and were calculated as -20.01 and -39.39 kJ mol -1 , respectively. Electrodic redox reaction of cytochrome c metalloprotein was accessed by using the Hpyt SAM with a heterogeneous electron transfer rate constant of 2.29 10 -3 cm s -1 .

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