Print-Light-Synthesis of ruthenium oxide thin film electrodes for electrochemical sensing applications

Print-Light-Synthesis (PLS) combines the inkjet printing of a ruthenium precursor ink with the simultaneous photo-induced generation of ruthenium oxide films. During PLS, inkjet-printing generates on conductive as well as insulating substrates micrometer-thin reaction volumes that contain with high precision defined precursor loadings. Upon direct UV light irradiation, the Ru precursor converts to RuO₂ while all other ink components escape in the gas phase. No post PLS processes are required, and the as-obtained RuO₂ films can be immediately used as electrochemical devices. Two-dimensional RuO₂ patterns with micrometric resolution and highly-controlled ruthenium loadings (few µg/cm²) are realized. Thin RuO₂ films are generated on insulating substrates, such as polyimide, as well as individual RuO₂ particles on conductive substrates, such as graphene layers. The RuO₂ films are characterized by electron microscopy and spectroscopic techniques. The sensoristic applicability of the PLS-RuO₂ electrodes is demonstrated by potentiometric pH sensing in cell cultures and amperometric detection of L-cysteine. For pH sensing the RuO₂ film electrodes show Nernstian sensitivity. L-cysteine detection of RuO₂-modified graphene electrodes showed an electrocatalytical effect and resulted in the possibility of selectively detecting L-Cysteine also in presence of the interfering compound uric acid.