Surface plasmon resonance imaging of surface impedance

An imaging impedance measurement technique was developed using surface plasmon resonance (SPR) and electrochemical (EC) potential modulation. It allows measuring the impedance of entire region using a single working electrode. This is useful in analyzing the surface impedance through measurement of the change in the working electrode/sensing surface charge density.;Surface plasmon resonance is a useful phenomenon that can be used to measure changes in the refractive index near the gold sensing surface. With the addition of EC potential control using the gold layer as the working electrode, SPR can be used to extract impedance information from the response of a modulated EC potential. The use of an imaging device allows for a spatially dependent measurement of surface plasmon resonance. The impedance of multiple array elements can be queried simultaneously without the need for individual working electrodes through the use of SPR imaging of impedance.;Measurements of surface capacitance were made of unmodified gold surfaces along with modified regions consisting of self-assembled thiol monolayers. These measured capacitances were in line with published values. An array of thiols were printed and measured on a single gold electrode with the resulting measured capacitance values being also in line with published numbers. Finally, this technique was applied to cancer cells incubated on the gold that showed differences in the impedance of regions of the cells.