Electrochemical Etching Tips Suitable To Be Used In Tip Enhanced Raman Spectroscopy

Tip Enhanced Raman Spectroscopy (TERS) is a form of measurement by which we are able to acquire not only the topographic features of a surface but also its chemical properties via inelastic vibrational scattering. Raman scattering is extremely weak (1 in 106 photons) therefore enhancement is required. Metal tips (gold, silver) act as an antenna by plasmonically coupling far field laser light to create an intense, localized electromagnetic field beneath the tip.  This localized field enhances Raman scattering which was once too weak to measure but due to the magnification from the metal tip is now more easily detected. Preparation of these tips will be through electrochemical etching in a homemade etching device and voltage regulator.  Tip quality will be assessed via light and/or electron microscopy. Silver or gold tips are selected due to their plasmons in the visible frequency range. Future studies will help to find a relationship between the freshness of solution and increase in voltage.  Although tungsten’s plasmon is not in the visible frequency range, plating it with silver could serve effective in TERS. To prepare the tungsten tip for silver plating, they will be chemically etched by various concentrations of potassium hydroxide, increasing the surface roughness.  The goal is to find positive correlation between tungsten’s surface roughness and subsequent silver plating. Overall tip quality will also be correlated to etching parameters such as etching voltage and solution age. This research will aid in future TERS measurement for optimal identification of surface chemistry and topography.