Inexpensive and rapid fabrication of paper-based electrochemical cells using a gold leaf and a toner laser printer

ABSTRACT This article presents a simple and innovative approach for the fabrication of flexible and low-cost planar electrochemical cells using paper-deposited gold electrodes (PGLE). This approach involves the use of a laser printer to selectively deposit toner onto a hydrophobic filter paper, which is then laminated with a gold leaf. The toner layer, which defines the design of the electrochemical circuit, acts as an adhesive and allows the gold to bond securely. The excess gold not adhering to the toner was gently removed using a cotton stick to create the working electrode, counter electrode, and reference electrode, with their contacts made with the thin layer of pure metal. The proposed approach takes advantage of readily available materials and common office tools that can be easily recovered even in low-resource settings. It allows the electrode geometry to be quickly modified but also to change the type of metal leaf adopted. In addition, the use of hydrophobic paper provides a viable alternative to plastic substrates for the fabrication of sustainable analytical devices capable of operating in both droplet and bulk mode. Furthermore, it must be also underlined that the functionality of the devices was not damaged during prolonged exposure to aqueous solutions. After optimization of the fabrication process, the electrochemical characterization of these cells was performed by using potassium hexacyanoferrate(II), hexamine ruthenium (III) chloride and dopamine as the prototype analytes. Voltammetric responses displayed a good inter-device reproducibility (5.4%), thus confirming the effectiveness of this easy and fast assembling strategy. In these tests, the possibility of using a silver leaf to assemble PGLEs with Ag/AgCl reference electrodes was also assayed. Finally, PGLEs were tested for the quantification of lead and copper in tap water by square wave anodic stripping voltammetry, thus demonstrating that they displayed expected performances in various modes of operation. In particular, the proposed method presented a good linear range between 10 and 100 ppb and 2 and 100 ppb as well as low detection limits of 2.9 and 0.6 ppb, for Pb 2+ and Cu 2+ , respectively. The dry construction process is an attractive option to other expensive, laborious, and time-consuming methods and does not require the use of solvents or post-production heat treatments and could be used to implement devices for flow-injection and microchip capillary electrophoresis analysis.