The schematic representation of the temperature-controlled two-step adsorption experiment is shown in Fig. . SERS spectra obtained for samples prepared at 25 °C with various examined delays are presented in Fig. . A prominent change in the spectral profile can be observed upon the introduction of a delay. Remarkably, a delay as short as 1 minute is sufficient to make the isotopologue added first dominate the surface composition of the adsorbed monolayer (compare the intensity of Cys-cabn and Cys-CABN SERS marker bands in Fig. ) despite equal amounts of both isotopologues present in the system. This is in line with previous reports showing that homocysteine is able to displace the citrate ions from the surface of Au nanoparticles and create a stable monolayer within 60 s from addition . This memory effect constitutes strong evidence that the system is under kinetic control and that detachment of cysteine molecules bound to the AgNP surface faces significant energy barriers. This behavior is observed regardless of the order in which Cys-cabn/Cys-CABN aliquots are added. Reversing this order yields almost exactly the mirror image of the SERS marker bands, as evidenced by Fig. for samples obtained with a 10-minute delay between aliquots. However, the surface composition of the monolayer changes dramatically with increasing temperature, as evidenced by the spectra presented in Fig. , collected for samples prepared at 60 °C. Such samples exhibit spectra with SERS marker bands of virtually equal intensity, suggesting that surface concentrations of both isotopologues are virtually equal as well. This, in turn, indicates that the barriers to the cysteine exchange at the surface of AgNPs are overcome with the moderate increase in temperature and the exchange accelerates. Cys-cabn and Cys-CABN are chemically identical, thus the enthalpy of the exchange reaction is, by definition, equal to zero and the process is driven solely by the entropy. The equilibrium constant for the exchange reaction between chemically identical isotopologues is 1 (in contrast to other works on the subject, where the constant is often difficult to establish ). Thus, since the amounts of both isotopologues in the system are equal after the addition of the second aliquot, the equilibrium state would involve equal amounts of both isotopologues adsorbed onto the AgNPs. That is clearly not the case at 25 °C; however, the system approaches such a state via the exchange already at 60 °C (see Fig. ).