Very High Frequency Electrochemical Reflectance Spectroscopy for Bulk Analyte in Aqueous Solutions

Typical electrochemical impedance spectroscopy relies on measurements at range up to several MHz at the highest depending on the application. In this work, the use of an electric network analyzer to measure system reflectance at extremely high frequencies from 50 kHz to 500 MHz enables Electochemical Reflectance Measurements to be made at much larger than typical frequency ranges with extremely high signal to noise ratios. This setup allows measurements of sample concentrations of various analytes (salts, nanoparticles, and microparticles) in bulk volumes far away from sensor surfaces.

Within its linear operating range, the experimental apparatus is capable of distinguishing bulk salt concentrations over 5 orders of magnitude, and distinguishing between different salts based on anion size, cation size, as well as valency. Observed changes in both magnitude and peak frequency of response were observed, making identifying of these various salts possible best on these measurements possible in the future. Additionally, the device was capable of measuring he concentration change in 5 nm sized Carbon dots and 10-micron latex particles. However, variations in the signals between these particles were difficult to elucidate. We believe with better design of testing cells to create larger linear measurement ranges, the system performance can be improved to better identify these targets.