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

Abstract

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.

Measuring Electrochemical Surface Area of Nanomaterials versus the Randles−Ševčík Equation

“…[11] Some approaches could also be used for gold surfaces, which are often used as important nanoparticle electrocatalysts. Different types of strategies without the necessity to use conventional redox probes can be found in the literature [13,14] and the outcome could be different, depending on the choice the value of the area calculated. The correct choice of the redox probe is one crucial factor.…”

SERS multiplexing of methylxanthine drug isomers via host–guest size matching and machine learning

“…Caffeine (CAF) also exists in its protonated form in our studies as its conjugated acid has a pK a of 10.4. 4 The binding of CB7 to CAF was first suggested by Issacs and co-workers in 2009 but without reporting the binding constant, 38 meanwhile the host-guest complexations of CB with TBR and TPH were studied for the first time.…”

Electrochemical studies of lateral flow assay test results for procalcitonin detection

“…In the present work, CVs were performed with the paper strip as a working electrode which exhibits low conductivity. Thus, to enhance electron transmission between the working electrode and electrolyte and to record oxidation/reduction currents in CV curves, the redox probe [Fe(CN)6 ] 3−/4− was added as a marker to investigate changes in electrode behaviour after loading different concentrations of PCT on the paper strip [34,36,37].…”