Through attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), we have studied the adsorption characteristics of small unilamellar vesicles (SUVs) of a gel-phase phospholipid, dipalmitoylphosphatidylcholine (DPPC), on an oxidized gold substrate. By monitoring the frequencies and intensities of vibrational absorption modes due to phosphate and methylene functional groups in the head and tail regions of the phospholipid, we differentiated the adsorption state of the precursor vesicles (i.e., intact vs ruptured vesicles) as a function of vesicular size in the SUV limit and the properties of the aqueous-phase solvent. We found that on oxidized gold, vesicles of DPPC in ultra pure water remained intact for all sizes tested (viz., 65, 80, and 160 nm) with varying degree of deformation. In contrast, when phosphate-buffered saline (PBS) was used as a bathing medium, all vesicles remained intact, were more distorted than the same size in pure water, and appeared to be nearly fully collapsed. Taken together, these results provide a rough guide for controlling vesicular behavior at the oxidized gold surface.

Attenuated total reflection Fourier transform infrared spectroscopy was used to monitor the formation of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), DMPC: lactosylceramide, and DMPC: GD3 lipid bilayers onto a zinc selenide surface. Infrared absorption peak position, bandwidth, and intensity were all used to monitor the formation, acyl chain ordering, and chemical environment within each bilayer. The results from this study indicate that the addition of glycosphingolipids into a DMPC lipid bilayer introduces decreases in both, acyl chain ordering, and homogeneity within the bilayer. GD3:DMPC lipid bilayers possess lipid chain characteristics that are indiscernible from those present in the lactosylceramide:DMPC bilayer, while possessing different structural head groups, indicating that the head group has little influence on the underlying lipid structure. Differences in the phosphate hydration are, however, evident between the three types of bilayer, with phosphate hydration decreasing in the order LacCer:DMPC (1223.4 cm−1) > DMPC only (1226 cm−1) > GD3:DMPC (1229.6 cm−1).Graphical abstractHighlights► Label free in situ analysis of lactosylceramide and GD3 DMPC bilayers. ► Characterization of each bilayer's molecular environments within and at the transmembrane and interfacial domain. ► Report varied levels of hydration for each glycosphingolipid–phospholipid bilayer mixture.

Iodobenzene decomposes on Pd(111) and forms benzene, iodine, adsorbed carbon, and hydrogen. At low initial iodobenzene exposures no iodobenzene desorbs, benzene desorbs at 500 K, and hydrogen desorbs between 500 and 700 K, indicative of decomposition of some of the benzene. At high initial exposures iodobenzene desorbs at about 200 K and benzene desorbs at about 160 K; however, no hydrogen desorbs. Iodine desorbs from Pd(111) around 1000 K. Adsorbed iodine atoms passivate the Pd(111) surface toward the decomposition of iodobenzene and the dehydrogenation of benzene. Experiments with perdeuterated iodobenzene show that the benzene forms from reaction of phenyl with sub-surface hydrogen by 143 K.

The dehydrogenation and decomposition of cyclohexene on clean Pd(111) have been investigated using Fourier transform mass spectrometry detection with thermal desorption spectroscopy (FT–TDS) and laser-induced thermal desorption (LITD–FTMS). TDS shows two molecular desorption peaks for cyclohexene centered around 180 K and 230 K in the submonolayer regime, with benzene desorbing at ∼450 K. LITD experiments show that benzene formation occurs at low temperatures (<150 K). The results of TDS experiments with c-C6H10 on Pd(111) are similar to those on Pt(111). However, the LITD results differ dramatically. Where c-C6H10 reacts away completely in both systems by 180 K, laser-induced desorption of benzene does not occur in significant amounts until ∼280 K on Pt(111).