Adsorption of Fluorescein Isothiocyanate Isomer-I (FITC-I) Dye on TiO2(110) from an Acetone Solution

Abstract

We have adsorbed fluorescein isothiocyanate isomer-I (FITC-I) dye (C21H11NO5S) onto the rutile TiO2(110) surface via a substitutional reaction between the dye and a pre-adsorbed, (2×1) ordered trimethyl acetate (TMA) layer. The TMA was prepared by evaporation of trimethyl acetic acid in an ultra-high vacuum (UHV) chamber. The TiO2(110)-(2×1)-TMA crystal was then removed from the vacuum chamber and immersed in a 10 mM FITC-I/acetone solution. The resulting TiO2(110)-FITC-I sample was analysed using UHV scanning tunneling microscopy (STM) and infrared-visible sum-frequency (SF) spectroscopy. STM showed the presence of large, bright spots attributed to adsorbed FITC-I dye molecules and SF spectroscopy showed vibrational bands assignable to FITC-I molecules. Together, this indicates that the dye molecule can be adsorbed intact onto the TiO2(110) surface via an exchange-reaction in solution.