pH sensitivity of Si-C linked organic monolayers on crystalline silicon surfaces

Erik J. Faber, Wouter Sparreboom, Wilrike Groeneveld, Louis C.P.M. de Smet, Johan G. Bomer, Wouter Olthuis, Han Zuilhof, Ernst J.R. Sudhölter, Piet Bergveld, Albert van den Berg

    Research output: Contribution to journalArticleAcademicpeer-review

    27 Citations (Scopus)

    Abstract

    The electrochemical behaviour of Si-C linked organic monolayers is studied in electrolyte-insulator-Si devices, under conditions normally encountered in potentiomeric biosensors, to gain fundamental knowledge on the behaviour 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 SiO2 layers and native SiO2 layers modified with hexamethyldisilazone. All samples display pH sensitivity. The number of Si-OH groups on the alkylated samples is calculated to be less than 0.7% of that of a pure SiO2 insulator, which still causes a pH sensitivity of approximate to 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 pK(a) values of all samples with monolayers (4.0-4.4) are lower than that of native SiO2 (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.
    Original languageEnglish
    Pages (from-to)101-112
    Number of pages12
    JournalChemPhysChem
    Volume8
    Issue number1
    DOIs
    Publication statusPublished - 8 Jan 2007

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