Field - dipole interactions in L-cysteine-thiolate self assembled at p- and n-GaAs(100) electrodes

Combined ab initio and XPS Investigations of the Electronic Interactions of L–Cysteine Adsorbed on GaAs(1 0 0)

“…Since the usual chemical shift, ΔBE is 1.4 ± 0.3 eV at As−S species and around 0.6 eV at Ga−S species, the first one can be easily discerned in the XPS spectra whereas the latter one manifests itself as a slight broadening of the Ga (3d) peak . As seen in Figure , the value of the I As‐3d5/2 / I Ga‐3d5/2 ratio is lower at the p‐doped substrate (1.30±0.01) than at the n‐doped one (1.45±0.01), suggesting that the adsorption of the cysteine in ethanol solution involves rather As‐sites at p‐doped and Ga‐sites at n‐doped GaAs(1 0 0), respectively, as previously found for the films formed in aqueous solutions . This conclusion is further supported by the higher weight of the As−S species observed at the p‐doped sample (7.3 %) than that found at the n‐doped one (4.7 %) as well as the higher value of the full width at half maximum (FWHM) parameter of the Ga‐3d 5/2 and Ga‐3d 3/2 components at the n‐doped sample (1.16 eV) than at the p‐doped one (1.05 eV).…”

“…This hybrid bio‐solid‐state electro‐optical device can be used as a photo‐sensor. According to our previous results, the PS I could be directly attached to the GaAs surfaces through the thiol group of the cysteine instead of using N‐ϵ‐maleimidocaproic acid or N‐β‐maleimidopropionic acid as linkers. The configuration of the adsorbed species is thus important, and any information in this respect very useful.…”

“…Consequently, we have extended our studies to semiconducting substrates, where the self‐assembling phenomenon also takes place. L‐cysteine monolayers spontaneously formed on p‐ and n‐GaAs(1 0 0) electrodes in aqueous solutions have been investigated combining experimental and theoretical approaches . The XPS data evidenced the preferential of the L‐cysteine with As‐sites at the p‐doped and with Ga‐sites at the n‐doped substrates, and pointed out different configurations of the adsorbed species at the two types of semiconducting substrate.…”

Enhanced inhibition of steel corrosion by L‐cysteine under visible‐light illumination

“…Several studies have emphasized that the presence of surface oxides and the corresponding microstructure plays an important role on the adsorption of L‐cysteine and inhibition efficiency . Electrochemical results show that the specimen surface presents distinct photovoltaic effect, implying the existence of oxide layer on the specimen surface.…”

“…Therefore, the corresponding surface electronic state must exert a significant effect on the adsorption mode of the adsorbed L‐cysteine and inhibition efficiency consequently. L‐cysteine adsorption behavior on p ‐ and n ‐GaAs (gallium arsenide) semiconductor surface without considering its corrosion inhibition performance have been characterized . However, to the best of our knowledge, few studies have focused on the preferential bonding of L‐cysteine on steel in neutral media under illumination and its effect on the substrate corrosion resistance.…”