Gold Nanoparticle Paper-Based Dual-Detection Device for Forensics Applications

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.