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.