Highly sensitive and stretchable PDA–PAA–Cr3+ hydrogel capacitive strain sensor is fabricated and used to monitor mechanical deformation and human motion.

Scarcity of clean water, due to population growth, global warming, and depletion of natural freshwater sources, is among the most formidable environmental challenges facing humanity. Accordingly, development of cost-effective and widely applicable technologies for water remediation and purification is extremely important and highly sought. We present a new strategy for water purification using a composite material comprising carbon dots (C-dots) encapsulated within a porous hydrogel. The hydrogel matrix allows significant water uptake, while the embedded C-dots constitute effective photothermal mediators, absorbing solar energy for enhanced water evaporation. The C-dots further bestowed greater thermal and mechanical stability to the hydrogel host. The C-dot/hydrogel composite exhibited good operating parameters, including a water evaporation rate of 1.4 kg m2 h‑1 and solar-to-vapor conversion efficiency of 89%. It was applied for diverse water treatment applications, including water desalination and removal of heavy metal ions, detergents, and organic molecules from contaminated water. The C-dot/hydrogel construct is easily synthesized from inexpensive, biocompatible, and environmentally friendly building blocks, is recyclable, and may be employed in varied water purification applications.

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Organophosphates are used as agricultural pesticides and also encountered as toxic nerve agents in chemical warfare. Accordingly, development of sensors for detecting and monitoring organophosphate vapors is highly sought after. We present a new capacitive gas sensor exhibiting remarkable specificity and sensitivity toward the organophosphate nerve gas simulants triethyl-phosphate (TEP) and dimethyl methyl phosphate and the pesticide dichlorvos. Specifically, the capacitive sensor comprises a composite porous graphene oxide matrix intercalating cobalt or nickel ions, prepared through a simple freezedrying procedure. We demonstrate that the porous graphene oxide/ metal ion electrode undergoes fast capacitance changes only upon exposure to organophosphate vapors. Moreover, the sensor exhibits extraordinary sensitivity upon interactions with TEP. Detailed mechanistic analyses, carried out in comparison to porous graphene oxide coupled to other transition metal ions, reveal that the remarkable sensing properties of the Co 2+ or Ni 2+ /porous graphene oxide systems likely arise from the distinct mode of metal ion incorporation into the graphene oxide host matrix and substitution of metal-complexed water ligands with organophosphate molecules. The new metal ion/porous graphene oxide capacitive sensor may be employed for alerting and monitoring organophosphate gases in different environments.

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