Ion sensing pencil: Draw your own sensor

A Pencil-Drawn Electronic Tongue for Environmental Applications

“…Initial characterization of ISPs revealed that their response behavior is analogous to classical ion selective electrodes (ISEs) [ 33 ]. This is not surprising given that ion exchange is the key response mechanism.…”

“…The values of sensor sensitivity calculated between 10 −5 and 10 −3 M for all studied sensors are reported in Table 2 . Specific details of the experimental protocols and discussion of these results are available in Reference [ 33 ]. Briefly, sensors exhibit various degrees of agreement with near-Nernstian slopes, which is not surprising given that selectivity of zeolites is inferior to classical ISEs that rely on strong covalent interaction of the target analyte to a very selective ionophore.…”

“…Sensors were prepared and thoroughly characterized according to a procedure reported in our previous publication [ 33 ]. Briefly, synthetic graphite powder (<20 μm, Sigma-Aldrich) and a zeolite ( Table 1 ) were mixed in 60:40 weight ratio in a ball mill.…”

“…Recently, a new approach towards the development of very simple and cost-effective sensors has been suggested [ 33 ]. It relies on the employment of zeolite-based “pencils” that can “draw” sensor lines on polymeric support, thus yielding simple potentiometric ion-sensitive devices (Ion Sensitive Pencils (ISPs)) capable of quantitative analysis of aqueous samples.…”

“…Since then, zeolites have been largely applied in gas sensors [ 36 ] (and references therein), whereas their applications for aqueous media are scarce. Their ion exchange property and the ability to withstand pressures needed to produce ISPs (4+ tonnes as shown in the original publication [ 33 ]) were the key driver of their application in ISPs. However, their selectivity is inferior to classical ionophores so the authors have suggested that the power of ISPs may lay in their application in multisensor arrays.…”