Covalent immobilization of a fluorescent pH-sensitive naphthalimide dye in sol–gel films

  • Antje KriltzEmail author
  • Christin Löser
  • Gerhard J. Mohr
  • Sabine Trupp
Original Paper


A pH indicator dye was covalently linked to inorganic–organic hybrid sol–gel layers via its carboxyl function by the formation of an amide bond. For this, the dye was activated by 2-succinimido-1,1,3,3-tetramethyluronium tetrafluoroborate and linked to N-(3-(trimethoxysilyl)propyl)-ethylendiamine. Different ratios of tetraethoxy-silane, diisobutyldimethoxysilane and 3-glycidoxypropyltrimethoxysilane were evaluated to tailor the performance of the sensing material. Fluorescence spectroscopy of the optimised sensor layers with a molar ratio of organically modified siloxane to tetraethoxysilane of 25.9 and of dye/amino groups of 1.16, showed a reversible fluorescence signal increase of 117 % upon protonation, and a pk a 6.5. The signal changes were caused by photoinduced electron transfer between the methylpiperazine moiety and the naphthalimide fluorophore, its efficiency being modulated by protonation of the methylpiperazine nitrogen. The influence of parameters such as synthesis, dip-coating process and heat-treatment on the performance of the sensor layers was investigated. Optimum signal changes were obtained when heating the sol–gel structure up to 170 °C.


Sol–gel pH indicator dye Naphthalimide-based receptor Fluorescent dye 



S. Trupp and G. J. Mohr were kindly supported by the Bayerische Staatsministerium für Wirtschaft, Infrastruktur, Verkehr und Technologie within project AZ-Nr.: 20.10-3410-2 (Projekt Sensormaterialien).


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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • Antje Kriltz
    • 1
    Email author
  • Christin Löser
    • 1
  • Gerhard J. Mohr
    • 2
  • Sabine Trupp
    • 2
  1. 1.Institut für Physikalische ChemieFriedrich-Schiller-Universität JenaJenaGermany
  2. 2.Fraunhofer Research Institution for Modular Solid-State Technologies EMFT, Workgroup Sensor MaterialsRegensburgGermany

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