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Structure and desorption energetics of ultrathin D2O ice overlay ers on serine- And serinephosphate-terminated self-assembled monolayers
Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik.
Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Organisk Kemi.
Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik.
2006 (Engelska)Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, nr 4, s. 1695-1700Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

This paper reports on the structure and desorption dynamics of thin D 2O 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 ~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 (~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. © 2006 American Chemical Society.

Ort, förlag, år, upplaga, sidor
2006. Vol. 110, nr 4, s. 1695-1700
Nationell ämneskategori
Teknik och teknologier
Identifikatorer
URN: urn:nbn:se:liu:diva-50301DOI: 10.1021/jp055169jOAI: oai:DiVA.org:liu-50301DiVA, id: diva2:271197
Tillgänglig från: 2009-10-11 Skapad: 2009-10-11 Senast uppdaterad: 2021-09-24
Ingår i avhandling
1. Temperature programmed studies of molecular assemblies on gold
Öppna denna publikation i ny flik eller fönster >>Temperature programmed studies of molecular assemblies on gold
2004 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This thesis investigates the properties of ultra-thin layers of organic molecules deposited at or adsorbed onto thin films of gold. The two main experimental techniques used in this thesis work are Temperature Programmed Desorption-Infrared Reflection Absorption Spectroscopy (TPD-IRAS), an excellent technique to probe the structure and orientation of molecular layers on metallic substrates, and Temperature Programmed Desorption-Mass Spectroscopy (TPD-MS), a very useful tool to study the energetics of molecular layers and adsorbates on solid surfaces. The two techniques are especially powerful when used simultaneously because they can be used to 1) follow molecular rearrangement phenomena occurring prior and during desorption; 2) find correlations between such rearrangement phenomena and the ultimate binding strength of the molecules/adsorbates to the surface.

The TPD-IRAS and TPD-MS techniques have been used to study: I) the structure and desorption dynamics of DNA bases on gold; II) the phase behavior of oligo(ethylene glycol) (OEG)-terminated selfassembled monolayers (SAMs) on gold; and III) the nucleation, growth and structure of D2O-ice on SAMsat liquid nitrogen temperatures in ultra high vacuum.

The first part investigates the orientation, structure and binding strength of DNA bases spontaneously adsorbed to gold. The four DNA bases interact very differently on and with the gold surface. Guanine and adenine interact strongly with the surface, and displays a series of complex structural transitions during the desorption event. Adenine form strong bonds with the gold surface, whereas cohesive interactions seem to dominate for guanine. Cytosine and thymine display a less complicated desorption behavior, and the corresponding desorption energies are lower/ much lower than those observed for adenine and guanine. These results are in qualitative agreement with recent studies of the activity of immobilized oligonucleotides on gold nanoparticles.

The second part is a study of SAMs of thiolated molecules on gold exposing OEG-tails in different conformations, all trans and helical, toward the ambient. The temperature dependence is investigated using TPD-IRAS, and it is found that the helical OEGs undergo a reversible phase transition into the all trans oramorphous states at approximately 60 °C, depending on chemical groups used to attach the OEG tail tothe alkyl thiol portion.

The third part focuses on ultra-thin ad-layers of D2O deposited onto OEG substrates at low temperature in UHV. Extensive simulations of RA spectra of the D2O-ice overlayers are performed using Maxwell Garnett effective medium theory to support the interpretation of the experimental data. These simulations reveal that the ice overlayers contain a significant and varying volume fraction of voids. Isothermal annealing ofthe ice overlayers shows that the kinetics of the amorphous to crystalline phase transition of ice, normally observed at about 140 K, is strongly dependent on the conformation of the OEG layer. The kinetics is fast on helical OEG SAMs most likely because of the existence of specific nucleation sites that governs the crystalline formation of ice.

The binding strength and structure of D2O deposited to biomimetic phosphate SAMs with H+, Na+ and Ca2+ as counter-ions are also investigated. D2O is tightly bound to Ca2+- and Na+- phosphate SAMs, affecting several ad-layers of D2O. These results may have implication for the chemistry occurring at biomineral surfaces, and specifically for the role of water on the nucleation and growth of hydroxyapatite, the inorganic component in bone.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University, 2004. s. 43
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 908
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
urn:nbn:se:liu:diva-179560 (URN)9185295809 (ISBN)
Disputation
2004-12-03, sal Planck, Fysikhuset, Linköpings Universitet, Linköping, 10:15
Opponent
Tillgänglig från: 2021-09-24 Skapad: 2021-09-24 Senast uppdaterad: 2023-02-24Bibliografiskt granskad

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Östblom, MattiasEkeroth, JohanKonradsson, PeterLiedberg, Bo

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