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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