Adsorption and coadsorption of water and glycine on TiO2

Abstract

Adsorption of water, ions, and biomolecules constitutes the first events occurring at biomaterial-biosystem interfaces. In this work, the adsorption and coadsorption of water and glycine on TiO2 were studied by thermal desorption spectroscopy (TDS). The first water monolayer desorbs in three peaks around 180K, 300K, and 400K, which are assigned to water molecularly adsorbed at oxygen sites, at Ti4+ sites, and to recombination of dissociated water, respectively. A fourth desorption peak (160K), appearing at coverages > 0.8 monolayer, is attributed to water clusters and multilayers. The water-TiO2 interaction is changed if the surface is annealed in vacuum, which leads to increased hydroxylation. Desorption spectra from glycine overlayers evaporated on TiO2 in situ show that around 40% of the first monolayer desorbs as intact molecules ( approximately 300-450 K) and the remainder as dissociation fragments and surface reaction products around 600 K. At coverages > 0.6 monolayers, intact molecules desorbing from cluster multilayers at 310 K are detected. The glycine desorption spectra are unaffected by coadsorbed water. In contrast, coadsorption of glycine displaces water from more strongly bound states in the monolayer to more weakly bound states and clusters, making the surface more hydrophobic. The study shows that TDS is a powerful method for characterizing biomaterial surfaces with regard to their interaction with biologically relevant molecules.

Hydrogen desorption from sand-blasted and acid-etched titanium surfaces after glow-discharge treatment

“…where is the pre-exponential factor (often assumed to be 10 13 s −1 ) 35 , is the surface coverage, the exponent x is the order of the desorption kinetics, E d is the activation energy for desorption (equal to adsorption energy for nonactivated desorption), k b is the Boltzmann's constant (1.3807 10 −23 J/K), and T is the temperature (in Kelvin). By plotting the Arrhenius expression…”

“…of the positive slope of the partial hydrogen pressure with R = p(m/z = 2) in the TD spectra (Fig. 8), the equivalent of an activation energy (E d ) for H 2 desorption can be found (assuming a 0 order desorption process 28,29,35 ; see below in discussion). TD results from plasma-treated SLA samples indicate a lowering of the activation energy (E d ) for thermal H 2 desorption (Fig.…”

IR and quantum-chemical studies of carboxylic acid and glycine adsorption on rutile TiO2 nanoparticles

“…This mode is thanks to the extra hydrogen bond about 36 kJ/mol more stable than the pure bridge mode. In synchrotron UPS and thermal desorption experiments, the zwitter ionic form has been detected for multilayer coverage [23,25], whereas a dissociative adsorption (which we do not investigate here) is dominant for sub-monolayer coverage [24,26]. Various forms of binding to the surface via a N-Ti coordination was also tested, where the most stable form found is shown in Fig.…”

“…Glycine adsorption has been studied experimentally, e.g., on the rutile (110) surface by photoelectron spectroscopy [1,23,24], and on TiO 2 crystallites (mainly rutile) using thermal desorption spectroscopy [25].…”

Surface modifications of dental implants

“…These repeating surface features are capable of combining properties of surface chemistry (e.g., surface energy) with biological attachment of adhesion ⁄ matrix peptides. 91,92 Similar photolithographic approaches have been used to create repeated patterns to generate controlled alternating domains of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (EDS) and dimethyldichlorosilane (DMS) as a means to control the adsorption of naturally occurring RGD adhesive proteins in serum (especially vitronectin). 80,82 In this way, a bioactive surface may be generated that uses the natural adhesive proteins in the blood plasma at the time of implant placement.…”