where k is the rate of desorption, A is a preexponential factor specific to the reaction, Ea is the activation energy required for desorption, R is the universal gas constant, and T is temperature in Kelvin. The experimental results directly support our hypothesis via the Arrhenius equation that the monolayer stability of MCO should be far superior to MCH at body temperature. Figure b shows results with electrochemical aptamer sensors for the antibiotic vancomycin 39 fabricated with either MCH or MCO passivation layers and tested with repeated scanning for 1 week in target-free phosphate buffered saline (PBS) at body temperature (i.e. 37 °C). Here and in subsequently presented data, we define the term repeated scanning as: 8 sensors (n=4 for MCH, n=4 for MCO) individually scanned using square wave voltammetry at 300Hz (potential step of 4mV from -0.1 V to -0.5 V vs. Ag/AgCl, 0.3 second in duration) approximately every 30 seconds, corresponding to the time required for the potentiostat/multiplexer to cycle through all electrodes tested.