ABSTRACT
A simple, portable electrochemical surface-enhanced Raman spectroscopy (SERS) system is reported, consisting of a small benchtop Raman spectrometer, a laptop computer, and a portable USB potentiostat. Screen printed electrodes modified with silver colloidal nanoparticles are used as the SERS-active electrode, which exhibit long-term stability once prepared. Spectroelectrochemical analyses of para-aminothiophenol and melamine as model systems was conducted. In both cases, an increase in SERS signal is observed upon modulation of the applied voltage, indicating an inherent benefit of such a system wherein the surface charge can be easily tuned. Given the low cost, rapid analysis time, and good sensitivity of this system, this simple setup could be implemented for many on-site sensing applications, ranging from food and drug analysis to environmental monitoring and to chemical and biological warfare agent detection.
ABSTRACT
Conservation efforts for heritage buildings require a substantial knowledge of the chemical makeup of materials that were used throughout the lifetime of the property. In particular, conservators are often concerned with the identification of colorants used in both interior and exterior wall treatments (paint, wallpaper, etc.) in order to gain perspective into how the building may have appeared during a certain time period in its existence. Ideally, such an analysis requires a technique that provides molecular level information as to the identity of the colorant as well as other sample components (binders, fillers, etc.), which is useful for dating purposes. In addition, the technique should be easily applied to paint layer samples which can be extremely thin and fragile. Herein we report the surface-enhanced Raman spectroscopy (SERS) analysis of paint and wallpaper samples taken from exterior and interior surfaces of a historic building. Several pigments were identified in the samples, which ranged from early inorganic pigments (lead white, barium sulfate, calcium carbonate, anhydrous chromium(III) oxide) which have been used in house paints for centuries, to a more modern pigment (phthalocyanine blue), developed in the middle of the 20th century. This analysis highlights the usefulness of SERS in such a conservation effort, and demonstrates for the first time pigment identification in house paints and wallpaper using SERS, which has far-reaching implications not only in the field of conservation, but also in forensics, industrial process control, and environmental health and safety.