Types of Screen-Printed Electrodes

As it has been mentioned in the previous section, due to the versatility of the production process of screen-printed electrodes, a wide range of SPEs can be made, containing only the working electrode, working and counter electrodes to work with an external reference electrode, a complete electrochemical cell, or even with multiple working electrodes, for applications where a disposable electrode is desired to perform electrochemical measurements Fig. 9.2. 

The most employed inks for the fabrication of screen-printed electrodes are made of carbon, gold, platinum, or silver. Nevertheless, other materials can be easily used. 

Gold or platinum are used in SPEs fabrication, avoiding the use of a great quantity of these expensive materials. In this sense, sometimes a narrow single-electrode sensor is used to replace metal electrodes. 

Carbon and gold have a wide use in the technology of disposable sensors as electrodic materials [8]. Gold has been employed as electrodic material for the genosensors construction for years, and carbon is especially used due to its great superficial chemistry, its low background current, the wide potential window at which it is possible to be employed, its low cost, and its chemical passivity. Nevertheless, the electronic-transfer rate obtained with carbon-based electrodes is lower than that obtained with metallic electrodes [9]. 

However, this disadvantage can be overcome by means of the surface modification of these electrodes with nanostructures, as the use of carbon nanotubes (CNTs) [10], or gold nanoparticles [11], since they improve the electronic transfer of the surface of the electrode, and improve the analj ical characteristics offered by the sensor. Carbon nanofibers can also be used to modify the electrodic surface in order to improve the analj ical characteristics of the transducer. 

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