A single-step laser scribing process is used to pattern nanostructured electrodes on paper-based devices. The facile and low-cost technique eliminates the need for chemical reagents or controlled conditions. This process involves the use of a CO laser to pyrolyze the surface of the paperboard, producing a conductive porous non-graphitizing carbon material composed of graphene sheets and composites with aluminosilicate nanoparticles. The new electrode material was extensively characterized, and it exhibits high conductivity and an enhanced active/geometric area ratio; it is thus well-suited for electrochemical purposes. As a proof-of-concept, the devices were successfully employed for different analytical applications in the clinical, pharmaceutical, food, and forensic fields. The scalable and green fabrication method associated with the features of the new material is highly promising for the development of portable electrochemical devices.
Asingle-step laser scribing process is used to pattern nanostructured electrodes on paper-based devices.T he facile and low-cost technique eliminates the need for chemical reagents or controlled conditions.T his process involves the use of aC O 2 laser to pyrolyze the surface of the paperboard, producing ac onductive porous non-graphitizing carbon material composed of graphene sheets and composites with aluminosilicate nanoparticles.The new electrode material was extensively characterized,and it exhibits high conductivity and an enhanced active/geometric area ratio;i ti st hus well-suited for electrochemical purposes.A saproof-of-concept, the devices were successfully employed for different analytical applications in the clinical, pharmaceutical, food, and forensic fields.T he scalable and green fabrication method associated with the features of the new material is highly promising for the development of portable electrochemical devices.
Drug trafficking is a major worldwide problem. In this context, cocaine is one of the most commonly used drugs of abuse. In addition, street cocaine is commonly seized adulterated with pharmaceutical compounds, and the composition of the mixture provides a chemical fingerprint that can assist the police in tracking the distribution route of the drug; hence, the development of facile, cost-effective methods for determining the composition of street cocaine is an important objective. Herein we report a simple strategy for the fabrication of paper-based analytical devices (PADs) for the dual electrochemical and surface-enhanced Raman-scattering (SERS) determination of cocaine samples. Accordingly, a 2-μm-thick Au film was prepared by depositing gold nanoparticles (AuNPs) on office paper with wax-barrier templates to create nanostructured gold tracks that are mainly formed by Au(111) fcc planes as electrodes and SERS transducers. These devices were characterized by scanning electron microscopy, X-ray diffractometry, electrochemical impedance spectroscopy, and energy-dispersive X-ray spectroscopy. The optimized device is simple and inexpensive to prepare and exhibited a Raman-scattering enhancement factor of 3 × 106, a 15-fold superior electroactive area, and a 2.6-fold decrease in charge-transfer resistance when compared with a conventional Au electrode. In addition, these PADs were successfully used in a forensics scenario to screen and analyze a seized street cocaine sample, determine its chemical profile, and to identify simultaneously caffeine, paracetamol, and levamisole adulterants.
Gold is among the most used materials in electrocatalysis. Despite this, this noble metal is still too expensive to be used in the fabrication of low cost and disposable devices. In the present work, gold-leaf sheets, usually employed in decorative crafts and wedding candies, is introduced as an inexpensive source of gold. Planar-disc and nanoband gold electrodes were simply and easily manufactured by combining gold leaf and polyimide tape. The planar disc electrode exhibited electrochemical behavior similar to that of a commercial gold electrode in 0.2molL HSO; cyclic voltammetry of a 1mmolL solution of potassium ferricyanide (K[Fe(CN)]) in 0.2molL KNO, using this novel electrode, displayed an 80mV difference between the oxidation and reduction peak potentials. The electrode also delivers promising prospects for the development of wearable devices. When submitted to severe mechanical deformation, this electrode exhibited neither loss of electrical contact nor significant variation in electrode response, even after fifteen bending and/or folding cycles. The thickness of the gold-leaf sheet facilitates the production of nanoband electrodes with behavior similar to that of ultramicroelectrodes. The electrode surface is easily renewed by cutting a thin slice off its end with a razor blade; this process led to limiting currents that were reproducible, presenting a relative standard deviation (RSD) of 3.8% (n = 5).
This study demonstrates a fast and simple method to fabricate enhanced ePADs using pencil-drawing with a CO2 laser treatment of the carbon surface deposited on paper. The sensor was applied to the detection of furosemide in a synthetic urine sample.
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