Structure and desorption energetics of ultrathin D2O ice overlayers on serine- and serinephosphate-terminated self-assembled monolayers.
This paper reports on the structure and desorption dynamics of thin D2O ice overlayers (0.2-10 monolayers) deposited on serine- and serinephosphate- (with H+, Na+, Ca2+ counterions) terminated self-assembled monolayers (SAMs). The D2O ice overlayers are deposited on the SAMs at approximately 85 K in ultrahigh vacuum and characterized with infrared reflection absorption spectroscopy (IRAS). Reflection absorption (RA) spectra obtained at sub-monolayer D2O coverage reveal that surface modes, e.g. free dangling OD stretch, dominate on the serine SAM surface, whereas vibrational modes characteristic for bulk ice are more prominent on the serinephosphate SAMs. Temperature programmed desorption mass spectrometry (TPD-MS) and TPD-IRAS are subsequently used to investigate the energetics and the structural transitions occurring in the ice overlayer during temperature ramping. D2O ice (approximately 2.5 monolayers) on the serine SAMs undergoes a gradual change from an amorphous- to a crystalline-like phase upon increasing the substrate temperature. This transition is not as pronounced on the serine phosphate SAM most likely because of reduced mobility due to strong pinning to the surface. We show also that the energy of desorption for a sub-monolayer of D2O ice on serinephosphate SAM surfaces with a Na+ and Ca2+ counterions is equally high or even exceeds previously reported values for analogous high-energy SAMs.
Division of Molecular Physics, Department of Physics, Chemistry, and Biology, Linköping University, SE-581 83 Linköping, Sweden.
Mattias
M
Ostblom
Johan
J
Ekeroth
Peter
P
Konradsson
Bo
B
Liedberg
D000327:Adsorption; D002118:Calcium / Q000737:chemistry; D017666:Deuterium Oxide / Q000737:chemistry*; D006046:Gold / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D008567:Membranes, Artificial; D008958:Models, Molecular; D044367:Phase Transition; D010768:Phosphoserine / Q000737:chemistry*; D012694:Serine / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics
D008567:Membranes, Artificial; D010768:Phosphoserine; D012694:Serine; D006046:Gold; D006859:Hydrogen; D012964:Sodium; D017666:Deuterium Oxide; D002118:Calcium