GRAPHENE-LIKE BASED-CHEMIRESISTORS INKJET-PRINTED ONTO DIFFERENT SUBSTRATES

The performances reproducibility of liquid phase sensor devices represents a current open question for the scientific community. The attention is focused on both the materials (sensing material solutions/dispersions, substrates) and deposition methods. Concerning the latter issue in our previous work we demonstrated that, among solution processable fabrication techniques, the inkjet printing (IJP) allows to deposit the sensing material based-ink in controlled way [1]. In that case we fabricated liquid phase exfoliated graphene-based chemiresistors and pointed out that the morphology of the printed films was directly influenced by the substrate surface so affecting the device sensing properties [1,2]. In the present work, we investigated the possibility to use self-assembling sensing materials to make the device responses independent of the substrate morphological characteristics. In this framework, we focused the attention on graphene-like (GL) layers that, being a graphene related nanomaterial, attract for low operating temperatures and offer interesting transduction properties and sensitivity to a wide range of chemicals and gas vapors. Additionally, GL layers also exhibit a typical self-assembling behavior. Recently, GL layers have been investigated as new sensing nanostructures for alcohol detection in vapor phase [3]. Here, we exploited the sensing capabilities of GL layers to ethanol in order to investigate their potentiality to be processed by means of IJP. We fabricated ethanol chemiresistors by printing an aqueous suspension of GL layers. The sensing ink was prepared through a double-step oxidation/reduction method starting from a nanostructured carbon black [4,5]. The GL layers-based ink was inkjet printed onto three different substrates with interdigitated Cr/Au electrodes (glossy paper, alumina and silicon dioxide), accordingly to the same printing parameters. The final sensor devices were exposed to 50 ppm of ethanol at RT in dry N2, setting the voltage at 1 V. The electrical responses of the sensor devices, analyzed in terms of conductance variation (DeltaG/G0) when exposed to this analyte, highlighted that, combining the self-assembling property of the GL layers with a controlled deposition method, that is fulfilled by IJP, it is possible to assure a process repeatability at fixed substrate (intra-substrate reproducibility) and by varying the substrates (inter-substrate reproducibility).