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Evaluation of the pH-sensitive swelling of a hydrogel by means of a plasmonic sensor substrate

: Kroh, Christoph; Wuchrer, Roland; Günther, Margarita; Härtling, Thomas; Gerlach, Gerald

Fulltext ()

Journal of sensors and sensor systems : JSSS 7 (2018), No.1, pp.51-55
ISSN: 2194-8771
ISSN: 2194-878X
Bundesministerium für Bildung und Forschung BMBF
VIPC; 03VP01970
Journal Article, Electronic Publication
Fraunhofer IKTS ()

The inline monitoring of parameters in aqueous liquids is facing an increasing demand in many different application areas. Hydrogels with pH-induced swelling and deswelling behavior offer a means to measure pH in such liquids. Here we investigate the optical interrogation of a pH-sensitive hydrogel which can be applied in the physiological pH range. For this, a nanostructured gold substrate supporting surface plasmon oscillations is coated with a HPMA/DMAEMA/TEGDMA/EG hydrogel. The gel swells in the pH range under investigation (here 4.5 to 6.5), and the resulting refractive index changes subsequently lead to a spectral shift of the plasmon resonance of the gold nanostructure. The spectral resonance position is determined from optical transmittance spectra of the sensor substrates, and the initial results for our hydrogel reported here indicate a nearly linear dependence between the swelling state and the plasmon resonance wavelength.