Stamped multilayer graphene laminates for disposable in-field electrodes: application to electrochemical sensing of hydrogen peroxide and glucose

A multi-step approach is described for the fabrication of multi-layer graphene-based electrodes without the need for ink binders or post-print annealing. Graphite and nanoplatelet graphene were chemically exfoliated using a modified Hummers' method and the dried material was thermally expanded. Expanded materials were used in a 3D printed mold and stamp to create laminate electrodes on various substrates. The laminates were examined for potential sensing applications using model systems of peroxide (H₂O₂) and enzymatic glucose detection. Within the context of these two assay systems, platinum nanoparticle electrodeposition and oxygen plasma treatment were examined as methods for improving sensitivity. Electrodes made from both materials displayed excellent H₂O₂ sensing capability compared to screen-printed carbon electrodes. Laminates made from expanded graphite and treated with platinum, detected H₂O₂ at a working potential of 0.3 V (vs. Ag/AgCl [0.1 M KCl]) with a 1.91 μM detection limit and sensitivity of 64 nA·μM^-1·cm^-2. Electrodes made from platinum treated nanoplatelet graphene had a H₂O₂ detection limit of 1.98 μM (at 0.3 V), and a sensitivity of 16.5 nA·μM^-1·cm^-2. Both types of laminate electrodes were also tested as glucose sensors via immobilization of the enzyme glucose oxidase. The expanded nanographene material exhibited a wide analytical range for glucose (3.7 μM to 9.9 mM) and a detection limit of 1.2 μM. The sensing range of laminates made from expanded graphite was slightly reduced (9.8 μM to 9.9 mM) and the detection limit for glucose was higher (18.5 μM). When tested on flexible substrates, the expanded graphite laminates demonstrated excellent adhesion and durability during testing. These properties make the electrodes adaptable to a variety of tests for field-based or wearable sensing applications. Graphical abstract Expanded graphite (eGR) and expanded nanoplatelet graphene (nGN) were chemically exfoliated, thermally expanded, and manually stamped into flexible multi-layer graphene laminate electrodes. Hydrogen peroxide amperometric testing of eGR laminates compared to nGN laminates and a screen printed carbon (SPC) electrode.