Quantifying the ultraslow desorption kinetics of 2,6-naphthalenedicarboxylic acid monolayers at liquid–solid interfaces

Kinetic effects in monolayer self-assembly at liquid–solid interfaces are not well explored but can provide unique insights. We use variable-temperature scanning tunneling microscopy (STM) to quantify the desorption kinetics of 2,6-naphthalenedicarboxylic acid (NDA) monolayers at nonanoic acid–graphite interfaces. Quantitative tracking of the decline of molecular coverages by STM between 57.5 and 65.0 °C unveiled single-exponential decays over the course of days. An Arrhenius plot of rate constants derived from fits results in a surprisingly high energy barrier of 208 kJ mol–1 that strongly contrasts with the desorption energy of 16.4 kJ mol–1 with respect to solution as determined from a Born–Haber cycle. This vast discrepancy indicates a high-energy transition state. Expanding these studies to further systems is the key to pinpointing the molecular origin of the remarkably large NDA desorption barrier.