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A fully roll-to-roll manufactured electrochemical sensor with high sensing and manufacturing reproducibility has been developed for the detection of nitroaromatic organophosphorus pesticides (NOPPs). This sensor is based on a flexible, screen-printed silver electrode modified with a graphene nanoplatelet (GNP) coating and a zirconia (ZrO2) coating. The combination of the metal oxide and the 2-D material provided advantageous electrocatalytic activity toward NOPPs. Manufacturing, scanning electron microscopy–scanning transmission electron microscopy image analysis, electrochemical surface characterization, and detection studies illustrated high sensitivity, selectivity, and stability (∼89% current signal retention after 30 days) of the platform. The enzymeless sensor enabled rapid response time (10 min) and noncomplex detection of NOPPs through voltammetry methods. Furthermore, the proposed platform was highly group-sensitive toward NOPPs (e.g., methyl parathion (MP) and fenitrothion) with a detection limit as low as 1 μM (0.2 ppm). The sensor exhibited a linear correlation between MP concentration and current response in a range from 1 μM (0.2 ppm) to 20 μM (4.2 ppm) and from 20 to 50 μM with an R 2 of 0.992 and 0.991, respectively. Broadly, this work showcases the first application of GNPs/ZrO2 complex on flexible silver screen-printed electrodes fabricated by entirely roll-to-roll manufacturing for the detection of NOPPs.

Thin-film pH electrodes on thermoplastic substrates can be subjected to γ-radiation (up to 45 kGy) without loss of stability or sensing performance, with important ramifications for monitoring analytes in sterile environments. pH-sensing membranes composed of polyvinyl chloride (PVC), trioctyl trimellitate (TOTM), and a standard hydrogen ionophore were cast onto screen-printed carbon electrodes with exfoliated graphene as a solid contact. Irradiated thin-film electrodes were conditioned in phosphate buffers and monitored for up to 3 months for changes in voltage readout and pH sensitivity, relative to untreated controls. The sensitivities of both irradiated and control electrodes were consistently Nernstian over a 100 day window, with both types exhibiting logarithmic voltage decays but in opposite directions. The γ-irradiated electrodes had excellent long-term stability with quasi-linear voltage drifts of +0.28 mV (∼0.005 pH) per day. Voltage readouts from sterilized thin-film electrodes in cell culture media could be converted by single-point calibration into pH values that fell within 0.07 units relative to a commercial pH meter (calibrated daily).

The inkjet printing of metal electrodes on polymer films is a desirable manufacturing process due to its simplicity but is limited by the lack of thermal stability and serious delaminating flaws in various aqueous and organic solutions. Kapton, adopted worldwide due to its superior thermal durability, allows the high-temperature sintering of nanoparticle-based metal inks. By carefully selecting inks (Ag and Au) and Kapton substrates (Kapton HN films with a thickness of 135 μm and a thermal resistance of up to 400 °C) with optimal printing parameters and simplified post-treatments (sintering), outstanding film integrity, thermal stability, and antidelaminating features were obtained in both aqueous and organic solutions without any pretreatment strategy (surface modification). These films were applied in four novel devices: a solid-state ion-selective (IS) nitrate (NO 3 − ) sensor, a single-stranded DNA (ssDNA)-based mercury (Hg 2+ ) aptasensor, a low-cost protein printed circuit board (PCB) sensor, and a long-lasting organic thin-film transistor (OTFT). The IS NO 3 − sensor displayed a linear sensitivity range between 10 −4.5 and 10 −1 M (r 2 = 0.9912), with a limit of detection of 2 ppm for NO 3 − . The Hg 2+ sensor exhibited a linear correlation (r 2 = 0.8806) between the change in the transfer resistance (R CT ) and the increasing concentration of Hg 2+ . The protein PCB sensor provided a label-free method for protein detection. Finally, the OTFT demonstrated stable performance, with mobility values in the linear (μ lin ) and saturation (μ sat ) regimes of 0.0083 ± 0.0026 and 0.0237 ± 0.0079 cm 2 V −1 S −1 , respectively, and a threshold voltage (V th ) of −6.75 ± 3.89 V.

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