Electrical Properties of Polyetherimide-Based Nanocomposites Filled with Reduced Graphene Oxide and Graphene Oxide-Barium Titanate-Based Hybrid Nanoparticles.

The electrical properties of nanocomposites based on polyetherimide (PEI) filled with reduced graphene oxide (rGO) and a graphene oxide hybrid material obtained from graphene oxide grafted with poly(monomethyl itaconate) (PMMI) modified with barium titanate nanoparticles (BTN) getting (GO-g-PMMI/BTN) were studied. The results indicated that the nanocomposite filled with GO-g-PMMI/BTN had almost the same electrical conductivity as PEI (1 × 10-11 S/cm). However, the nanocomposite containing 10 wt.% rGO and 10 wt.% GO-g-PMMI/BTN as fillers showed an electrical conductivity in the order of 1 × 10-7 S/cm. This electrical conductivity is higher than that obtained for nanocomposites filled with 10% rGO (1 × 10-8 S/cm). The combination of rGO and GO-g-PMMI/BTN as filler materials generates a synergistic effect within the polymeric matrix of the nanocomposite favoring the increase in the electrical conductivity of the system.

Affordable equipment to fabricate laser-induced graphene electrodes for portable electrochemical sensing.

Graphene-based materials present unique properties for electrochemical applications, and laser-induced conversion of polyimide to graphene is an emerging route to obtain a high-quality material for sensing. Herein we present compact and low-cost equipment constructed from an open-source 3D printer at which a 3.5-W visible (449 nm) laser was adapted to fabricate laser-induced graphene (LIG) electrodes from commercial polyimide, which resulted in electron transfer kinetic (k0) of 5.6 × 10-3 cm s-1 and reproducibility calculated by relative standard deviation (RSD < 5%) from cyclic voltammograms of [Fe(CN)6]3-/4- using 5 different electrodes. LIG electrodes enabled the simultaneous voltammetric determination of uric acid (+ 0.1 V vs. pseudo-reference) and nitrite (+ 0.4 V vs pseudo-reference), with limit of detection (LOD) values of 0.07 and 0.27 µmol L-1, respectively. Amperometric measurements for the detection of H2O2 (applying + 0.0 V vs. Ag|AgCl|KCl(sat.)) after Prussian blue (PB) modification and ciprofloxacin (applying + 1.2 V vs. Ag|AgCl|KCl(sat.)) were performed under flow conditions, which confirmed the high stability of LIG and LIG-PB surfaces. The LOD values were 1.0 and 0.2 µmol L-1 for H2O2 and ciprofloxacin, respectively. The RSD values (< 12%) obtained for the analysis using three different electrodes attested the precision of LIG electrodes manufactured in two designs. No sample matrix effects on the determination of ciprofloxacin in milk samples were observed  (recoveries between 84 and 96%). The equipment can be built with less than $300 and each LIG electrode costs less than $0.01.