Fabrication of a “Green” and Low–Cost Screen–Printed Graphene Sensor and Its Application to the Determination of Caffeine by Adsorptive Stripping Voltammetry

Abstract

This work reports the development of low-cost graphene-based screen-printed sensors using a "green" fabrication procedure. Three-electrode sensors featuring carbon working and counter electrodes and a Ag reference electrode were fabricated by screen-printing on flexible polymer film. Graphene suspension was prepared following a simple, fast and environment-friendly method of solvent exfoliation of graphite in N-methyl pyrrolidone (NMP). Graphene was further dispersed in Nafion and the solution was used to drop-coat the working electrode of the sensor. The modified electrode was characterized using Raman spectroscopy, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The graphene/Nafion modified sensors were used to determine caffeine by anodic adsorptive stripping voltammetry. The procedure consists of a short adsorptive preconcentration step of caffeine on the graphene working electrode followed by an anodic voltammetric scan in the differential pulse (DP) mode. The oxidation current of caffeine is related to its concentration in the sample. High sensitivity was achieved due to the preconcentration step of the target compound on the working electrode. The limit of detection (LOD) for caffeine was 0.021 μmol L -1 and the % relative standard deviation (n=8) was 2.0 %. The sensors were applied to the determination of caffeine in coffee and beverage samples.

How can Electrode Surface Modification Benefit Electroanalysis?

“…Two limiting cases can be envisaged. In the first the accumulated material is directly oxidized or reduced in its adsorbed state – for example in the cases of capsaicin and caffeine – whereas in the second the material has to first desorb and then transport to the electrode surface. The latter case corresponds to the now common practice of using insulating particles (imprinted polymeric nanobeads in the detection of mercury, for example ) and materials as electrode modifiers.…”

Recent Advances in Electrochemical Sensors for Caffeine Determination

“…Lezi et al [ 90 ] described the preparation process and the application of a graphene/Nafion-modified screen-printed electrode (SPE-Nafion/graphene) for CF determination in 0.2 M H 2 SO 4 /0.01 M HCl solution using adsorptive stripping voltammetry. Due to the synergistic effect of Nafion and graphene, the modified SPE exhibited high sensitivity and a low limit of detection for CF ( Table 5 ).…”

Carbon Nanostructure-based Sensors: A Brief Review on Recent Advances

“…GPN and its derivatives have been used as a raw material for sensors in different applications due to their thermal and electrical conductivity, large surface area, fast heterogeneous electron transfer rates, and high mechanical strength [37][38][39][40]. Recent studies showed exceptional results for instance better sensibility, low cost, easy operation, fast response and recovery time, and good selectivity.…”

“…erefore, determining the concentration of caffeine in food samples is necessary to avoid involuntary excessive consumption of this compound. Lezi [39] fabricated a GPN/Nafion sensor to determine the presence of caffeine by adsorptive stripping voltammetry.…”