Heavy metals such as lead, mercury, cadmium, zinc and copper are among the most important pollutants because of their non-biodegradability and toxicity above certain thresholds. Here, we review methods for sensing heavy metal ions (HMI) in water samples using screenprinted electrodes (SPEs) as transducers. The review (with 107 refs.) starts with an introduction into the topic, and this is followed by sections on (a) mercury-coated SPEs, (b) bismuth-coated SPEs, (c) gold-coated SPEs (d) chemically modified and non-modified carbon SPEs, (e) enzyme inhibition-based SPEs, and (f) an overview of commercially available electrochemical portable heavy metal analyzers. The review reveals the significance of SPEs in terms of decentralized and of in situ analysis of heavy metal ions in environmental monitoring.

Graphene is regarded as the ultimate material for future flexible, high-performance and wearable electronics. Herein, we report a novel, robust, all-green, highly reliable (yield ≥ 99%) and up-scalable technology for wearable applications comprising reduced graphene oxide (rGO) thin-films as electroactive component in liquid-gated transistors (LGTs).Although the intrinsic electrical performance of rGO cannot compete with CVD graphene, its ease processability, excellent surface reactivity, and large-area coverage make rGO a formidable material for future flexible and wearable applications. We have established a novel protocol towards the high-yield fabrication of flexible rGO LGTs combining high robustness (>1.5h of continuous operation) with state-of-the-art performances, being similar to those of their rigid counterparts operated under liquid gating, including field-effect mobility of ca. 10 -1 cm 2 V -1 s -1 and transconductance of ca. 25 µS. Permeable membranes have been proved crucial to operate flexible LGTs under mechanical stress and with reduced amounts of solution (< 20 µL). Our rGO LGTs were operated in artificial sweat exploiting two different layouts based on lateral-flow paper fluidics. These approaches pave the road towards future real-time tracking of perspiration via a simple and cost-effective approach. The reported findings contribute to the robust and scalable production of novel graphene-based flexible devices, whose features fulfill the requirements of wearable electronics.Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff)) Published online: ((will be filled in by the editorial staff))

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The monitoring of K + in saliva, blood, urine, or sweat represents a future powerful alternative diagnostic tool to prevent various diseases. However, several K + sensors are unable to meet the requirements for the development of point-of-care (POC) sensors. To tackle this grand-challenge, the fabrication of chemiresistors (CRs) based on 3D networks of Au nanoparticles covalently bridged by ad-hoc supramolecular receptors for K + , namely dithiomethylene dibenzo-18-crown-6 ether is reported here. A multi-technique characterization allows optimizing a new protocol for fabricating high-performing CRs for real-time monitoring of K + in complex aqueous environments. The sensor shows exceptional figures of merit: i) linear sensitivity in the 10-3 to 10-6 m concentration range; ii) high selectivity to K + in presence of interfering cations (Na + , Ca 2+ , and Mg 2+); iii) high shelf-life stability (>45 days); iv) reversibility of K + binding and release; v) successful device integration into microfluidic systems for real-time monitoring; vi) fast response and recovery times (<18 s), and v) K + detection in artificial saliva. All these characteristics make the supramolecular CRs a potential tool for future applications as POC devices, especially for health monitoring where the determination of K + in saliva is pivotal for the early diagnosis of diseases.

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Two graphene oxide (GO) materials with different layer size and proportion of functional groups in the basal planes (hydroxyl and epoxy) and in the edges (carbonyl and carboxyl) were used to modify the surface of commercially available screen printed electrodes. Cyclic voltammetry in 0.1 M KNO 3 was evaluated as an easy to use electrochemical methodology to reduce GO attached to the surface of screen-printed electrodes (SPEs). A cathodic peak related to the reduction of GO was identified, and the peak potential was correlated to the difficulty to reduce GO to Electrochemically Reduced Graphene Oxide (ERGO) depending on the functional groups present in the basal plane and in the edges of the original GO monolayers. Time resolved UV-VIS absorption spectroelectrochemistry in near-normal reflection mode on a screen-printed electrode is used for the very first time as an in-situ characterization technique for real time monitoring unambiguously the electrochemical reduction of graphene oxide.

A new glucose sensor was developed using screen-printed ferrocyanide/carbon electrodes. The ferrocyanide is included in the carbon ink of the commercial screen-printed electrode. The immobilization of enzymes glucose oxidase (Gox) and horseradish peroxidase (HRP) were carried out in a very easy way. An aliquot of 10 mL of a Gox/ HRP mixture was deposited on the electrode surface and left there until dried (approximately 1 h) at room temperature. The ferricyanide generated enzymatically was detected amperometrically applying a potential of À0.1 V (vs. Ag pseudo reference electrode). The sensor, so constructed, shows a good sensitivity to glucose (À2.12 mA/mM) with a slope deviation of AE 0.06 mA/mM and a linear range comprised between 0.05 and 1 mM of glucose, with a limit of detection of 0.025 mM. These sensors show good intersensor reproducibility and a high stability. When they are stored at 4 8C, no significant changes in the slope value of the glucose calibration plot were found after 3 months. Glucose was determined in real samples as honey, blood, drink for babies and glucosed drink with a great accuracy.