In situ electrochemical exfoliation of embedded graphite to superficial graphene sheets for electroanalytical purposes

Development of a 3D disposable device for the electrochemical determination of diclofenac in different matrices

In this work, the development of a disposable electrochemical device (US$ 0.02 per electrode) using a 3D printed support (3Ds) of acrylonitrile butadiene styrene (ABS) insulating filament with a composite material (CM) based on graphite and nail polish, immobilized on the support surface, was described for the electrochemical determination of diclofenac (DCF). The device was compared to the commercial glassy carbon electrode (GCE) and showed superior electroanalytical performance with approximately 1.8-fold higher current density. Additionally, an amperometric method for DCF determination in tap water, synthetic urine, and pharmaceutical formulation samples with the proposed electrode, using a flow injection analysis (FIA-AD) system, was developed. The optimized method presented excellent detectability (LOD = 0.47 µmol L^-1), with excellent precision and accuracy (relative standard deviation < 5.6%) and percent recovery from spiked samples ranging from 89 to 106%. In addition, the sensor showed optimal analytical frequency with approximately 108 injections per hour, which demonstrates the potential of this system using the proposed disposable electrode for implementation in routine analysis and quality control with good selectivity and sensitivity.

Systematic study of physicochemical and electrochemical properties of carbon nanomaterials

Carbon nanomaterials exhibit exceptional properties and broad horizon applications, where graphene is one of the most popular allotropes of this family due to its astounding performance in every stratum vis-à-vis other classical materials. The large surface area of 2630 m² g⁻¹, high electrical conductivity, and electron mobility of non-toxic graphene nanomaterials serve as the building blocks for supercapacitor studies. In this article, comparative studies are carried out between electrochemically exfoliated graphene sheets (GSs), solvothermally synthesized graphene quantum dots (GQDs) and acid refluxed carbon nanotubes (CNTs) as an energy storage electrode nanomaterial through cyclic voltammetry (CV). The electrochemical properties of the materials are well correlated with the physicochemical characteristics obtained from Raman, Fourier-transform infrared, and absorption spectroscopy. Thin GSs (0.8–1 nm) and small size (6–10 nm) GQDs fabricated by using laboratory-grade 99% purity graphite rods resulted in promising low-cost materials at mass scale as compared to conducting CNTs. The 0D graphene quantum dots proved to be an excellent energy electrode material in an alkaline electrolyte solution compared to other carbon nanomaterials. The distinct characteristic features of GQDs, like superior electrical properties, large surface area, and abundant active sites make them an ideal candidate for utilization in supercapacitors. The GQDs exhibited an enhanced specific capacitance of 113 F g⁻¹ in 6 mol L⁻¹ KOH through cyclic voltammetry.

Carbon nanomaterials exhibit exceptional properties and broad horizon applications, where graphene is one of the most popular allotropes of this family due to its astounding performance in every stratum vis-à-vis other classical materials.

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.

3D-printing for forensic chemistry: voltammetric determination of cocaine on additively manufactured graphene-polylactic acid electrodes

Cocaine is probably one of the most trafficked illicit drugs in the world. For this reason, police forces require fast, selective, and sensitive methods for cocaine detection at crime scenes. Taking benefit of additive manufacturing, we demonstrate that 3D-printed graphene-polylactic acid (G-PLA) electrodes using the affordable fused deposition modelling technique can identify and quantify cocaine in seized drugs. The detection of cocaine based on its electrochemical oxidation on such electrodes was dramatically improved after an electrochemical surface treatment that generates reduced graphene oxide (anodic followed by a cathodic treatment). Square-wave voltammetric determination of cocaine was achieved in the concentration range between 20 and 100 μmol L-1, with a detection limit of 6 μmol L-1, and free from the interference of paracetamol, caffeine, phenacetin, lidocaine, benzocaine and levamisole, which are common adulterants found in seized drugs. The analytical characteristics obtained using 3D-printed G-PLA electrodes were comparable with those of previously reported electrochemical sensors, but presented the inherent advantages of the 3D-printing technology that enables low-cost, reproducible, and large-scale production of such electrodes in remote areas combined with the use of an environmentally-friendly biopolymer.