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pH Sensitivity of SiC Linked Organic Monolayers on Crystalline Silicon Surfaces
Author(s) -
Faber Erik J.,
Sparreboom Wouter,
Groeneveld Wilrike,
de Smet Louis C. P. M.,
Bomer Johan,
Olthuis Wouter,
Zuilhof Han,
Sudhölter Ernst J. R.,
Bergveld Piet,
van den Berg Albert
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600447
Subject(s) - potentiometric titration , monolayer , titration , chemistry , silicon , electrochemistry , biosensor , electrolyte , analytical chemistry (journal) , electrode , inorganic chemistry , materials science , organic chemistry , biochemistry
Abstract The electrochemical behavior of SiC linked organic monolayers is studied in electrolyte–insulator–Si devices, under conditions normally encountered in potentiometric biosensors, to gain fundamental knowledge on the behavior of such Si electrodes under practical conditions. This is done via titration experiments, Mott–Schottky data analysis, and data fitting using a site‐binding model. The results are compared with those of native SiO 2 layers and native SiO 2 layers modified with hexamethyldisilazane. All samples display pH sensitivity. The number of SiOH groups on the alkylated samples is calculated to be less than 0.7 % of that of a pure SiO 2 insulator, which still causes a pH sensitivity of ≈25 mV per pH unit in the pH range: 4–7. The alkylated samples hardly suffer from response changes during up‐ and down‐going titrations, which indicates that very little oxide is additionally formed during the measurements. The p K a values of all samples with monolayers (4.0–4.4) are lower than that of native SiO 2 (6.0). The long‐term drift (of approximately 1 mV h −1 ) is moderate. The results indicate that biosensors composed of alkylated Si substrates are feasible if a cross‐sensitivity towards pH in the sensor signal is taken into account.