The laser-scribed graphene (LSG) has already demonstrated as highly sensitive (bio)sensors. These flexible electrodes with large electrochemical areas were produced using direct-write laser process on polyimide sheets. The UV laser source was adapted into a Hypercube CoreXY 3D printer. In view of this, this work aims to produce and characterize LIG electrodes for simultaneous determination of uric acid (UA) and nitrite. First, the electrode was characterized by Raman spectroscopy, with three absorption bands being observed in 1349 (band D), 1585 (band G) and 2694 cm–1 (band 2D) confirming the formation of graphene. The X-ray diffractogram of the electrode exhibited a peak centered on 2 = 25.1o indicating a high degree of graphitization of the material [1]. The scanning electron microscopy (SEM) images showed that the laser treatment converted the polyimide into a porous graphene film (Fig. 1A), as confirmed by Raman. Moreover, a peak-to-peak separation (∆Ep) of 90 mV for the voltammetric response for the [Fe(CN)6]3-/[Fe(CN)6]4- couple was achieved. Electrochemical impedance spectroscopy was used to evaluate the resistance to charge transfer (Rct) when compared to commercially screen-printed carbon electrodes (SPCE). The Nyquist plot showed that the electronic transfer on LSG surface electrodes was significantly greater than SPCE. As a proof-of-concept, the LSG electrode was applied for simultaneous detection of UA and sodium nitrite. Using differential-pulse voltammetry and Britton-Robinson buffer (pH=3) as the supporting electrolyte, a linear range from 10 to 100 µmol L-1 and 10 to 70 µmol L-1, and detection limit values of 0.074 and 0.27 µmol L-1 were achieved for UA and sodium nitrite, respectively.
Figure 1. (A) SEM image of laser induced graphene electrodes. (B) Baseline-corrected DPV response curves for uric acid and sodium nitrite at different concentrations. The corresponding calibration curve for (C) uric acid. (D) and nitrite.
In conclusion, it is possible to state that LIG electrodes are efficient for the determination of uric acid and nitrite. The electrode fabrication is easily reproduced, affordable and can be extended to large scale production.
[1] Nature Communications volume 5, Article number: 5714 (2014), Laser-induced porous graphene films from commercial polymers, DOI: 10.1038/ncomms6714.