Highly-sensitive voltammetric detection of trinitrotoluene on reduced graphene oxide/carbon nanotube nanocomposite sensor.

This work presents the highly-sensitive detection of 2,4,6-trinitrotoluene (TNT) on reduced graphene oxide/multi-walled carbon nanotube (rGO/MWCNT) nanocomposite sensor. The formation of a thin film of this nanocomposite occurred at the cyclohexane/water immiscible interface of a mixture of MWCNT and rGO in the biphasic solution. The film was transferred to a boron-doped diamond (BDD) electrode for the square-wave voltammetric detection of TNT, which presented improved analytical characteristics in comparison with bare BDD and after modification with precursors. Electrochemical impedance spectroscopy also revealed the faster electron transfer for a redox probe on the nanocomposite modified surface. The synergistic properties of both carbon nanomaterials in the thin film modified surface resulted in a TNT sensor with a detection limit of 0.019 µmol L-1 within a wide linear range (0.5-1100 µmol L-1), with superior performance in comparison with other electrochemical sensors produced with carbon nanomaterials. This new material provides great promises for the highly-sensitive detection of other nitroaromatic explosives as well as other analytes. Moreover, the interfacial method enables the production of homogeneous and stable films on large coated areas as well as the large-scale production of electrochemical sensors.

3D printing for electroanalysis: From multiuse electrochemical cells to sensors.

This work presents potential applications of low-cost fused deposition modeling 3D-printers to fabricate multiuse 3D-printed electrochemical cells for flow or batch measurements as well as the 3D-printing of electrochemical sensing platforms. Electrochemical cells and sensors were printed with acrylonitrile butadiene styrene (ABS) and conductive graphene-doped polylactic acid (G-PLA) filaments, respectively. The overall printing operation time and estimated cost per cell were 6 h and $ 6.00, respectively, while the sensors were printed within minutes (16 sensor strips of 1 × 2 cm in 10 min at a cost of $ 1.00 each sensor). The cell performance is demonstrated for the amperometric detection of tert-butylhydroquinone, dipyrone, dopamine and diclofenac by flow-injection analysis (FIA) and batch-injection analysis (BIA) using different working electrodes, including the proposed 3D-printed sensor, which presented comparable electroanalytical performance with other carbon-based electrodes (LOD of 0.1 µmol L-1 for dopamine). Raman spectroscopy and scanning electron microscopy of the 3D-printed sensor indicated the presence of graphene nanoribbons within the polymeric matrix. Electrochemical impedance spectroscopy and heterogeneous electron transfer constants (k0) for the redox probe Ru(NH3)6+3 revealed that a glassy-carbon electrode presented faster electron transfer rates than the 3D-printed sensor; however, the latter presented lower LOD values for dopamine and catechol probably due to oxygenated functional groups at the G-PLA surface.