“…In the polar head group region, the ester and choline groups were analyzed from the CO stretching modes of the ester group and the CH bending and CN stretching bands in the choline moiety, respectively. The phosphate stretching modes are observable only on the Au surface, while on the silica surface they are overlapped with the strong SiO 2 stretching mode. − To facilitate discussion of PM IRRAS, data schemes of each analyzed group with the direction of the transition dipole moments are shown in Figure . 1 Structure of the DMPC molecule with marked groups analyzed by PM IRRAS.…”
Section: Resultsmentioning
confidence: 99%
“…The phosphate stretching modes are observable only on the Au surface, while on the silica surface they are overlapped with the strong SiO 2 stretching mode. [39][40][41] To facilitate discussion of PM IRRAS, data schemes of each analyzed group with the direction of the transition dipole moments are shown in Figure 1.…”
In this paper we report on the structural analysis of bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) using polarization modulation infrared reflection absorption spectroscopy (PM IRRAS). The lipid bilayers were formed on SiO2|Au and Au surfaces using the Langmuir-Blodgett and Langmuir-Schaeffer techniques. As we showed in part 1 (Zawisza, I.; Wittstock, G.; Boukherroub, R.; Szunertis, S. Langmuir 2007, 23, 9303-9309), SiO2 layers of 7 nm thickness, synthesized by plasma-enhanced chemical vapor deposition on 200 nm thick gold covered glass slides, allow PM IRRAS investigations. Only minor changes in the order and structure of the lipid bilayer are observed when deposited on SiO2|Au and Au surfaces. The choline moiety in the leaflet directed toward the SiO2 surface exists in trans conformation and shows a tilt of 28 degrees with the surface normal of the CN bond. On the silica surface in the second leaflet directed toward air and in two layers deposited on the Au surface, trans and gauche isomers of the choline moiety are present and the tilt of the CN bond increases to 55 degrees with respect to the surface normal. The order and molecular orientation in the DMPC bilayers on SiO2 and Au surfaces are not affected by time. The analysis of the phosphate stretching mode on the Au surface shows slight dehydration of this group and reorientation of the phosphate moiety.
“…In the polar head group region, the ester and choline groups were analyzed from the CO stretching modes of the ester group and the CH bending and CN stretching bands in the choline moiety, respectively. The phosphate stretching modes are observable only on the Au surface, while on the silica surface they are overlapped with the strong SiO 2 stretching mode. − To facilitate discussion of PM IRRAS, data schemes of each analyzed group with the direction of the transition dipole moments are shown in Figure . 1 Structure of the DMPC molecule with marked groups analyzed by PM IRRAS.…”
Section: Resultsmentioning
confidence: 99%
“…The phosphate stretching modes are observable only on the Au surface, while on the silica surface they are overlapped with the strong SiO 2 stretching mode. [39][40][41] To facilitate discussion of PM IRRAS, data schemes of each analyzed group with the direction of the transition dipole moments are shown in Figure 1.…”
In this paper we report on the structural analysis of bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) using polarization modulation infrared reflection absorption spectroscopy (PM IRRAS). The lipid bilayers were formed on SiO2|Au and Au surfaces using the Langmuir-Blodgett and Langmuir-Schaeffer techniques. As we showed in part 1 (Zawisza, I.; Wittstock, G.; Boukherroub, R.; Szunertis, S. Langmuir 2007, 23, 9303-9309), SiO2 layers of 7 nm thickness, synthesized by plasma-enhanced chemical vapor deposition on 200 nm thick gold covered glass slides, allow PM IRRAS investigations. Only minor changes in the order and structure of the lipid bilayer are observed when deposited on SiO2|Au and Au surfaces. The choline moiety in the leaflet directed toward the SiO2 surface exists in trans conformation and shows a tilt of 28 degrees with the surface normal of the CN bond. On the silica surface in the second leaflet directed toward air and in two layers deposited on the Au surface, trans and gauche isomers of the choline moiety are present and the tilt of the CN bond increases to 55 degrees with respect to the surface normal. The order and molecular orientation in the DMPC bilayers on SiO2 and Au surfaces are not affected by time. The analysis of the phosphate stretching mode on the Au surface shows slight dehydration of this group and reorientation of the phosphate moiety.
“…9) shows a strong band at 850-1100 cm −1 , containing contributions from the Si-N and Si-O stretching vibrations. 20 The 956 cm −1 peak corresponds to OSiN 3 groups. 15 Remarkable changes occur in the absorption bands in this region after milling for >21 min.…”
Section: Spectroscopic Examination Of the Milled Precursorsmentioning
“…3. From previous studies correlating the Si-O frequency with x, one can estimate that 1085 cm -1 would correspond to a sub-oxide SiOx of x=2, that is SiO 2 [27]. Another important feature of these results is the appearance of a second band at 1255 cm-1 when the incident beam is oblique.…”
Section: (A) a Typical Tem Image Of Sub-micron Size Si Whiskers As Fa...mentioning
The physical properties of black silicon (b-Si) formed on Si wafers by reactive ion etching in chlorine plasma are reported in an attempt to clarify the formation mechanism and the origin of the observed optical and electrical phenomena, which are promising for a variety of applications. The b-Si consisting of high density and high aspect ratio sub-micron length whiskers or pillars with tip diameters of well under 3 nm exhibits strong photoluminescence (PL) both in the visible and the infrared, which is interpreted in conjunction with defects, confinement effects and near band-edge emission. Structural analysis indicates that the whiskers are all crystalline and encapsulated by a thin Si oxide layer. The infrared vibrational spectrum of Si-O-Si bondings in terms of transverse-optic (TO) and longitudinal-optic (LO) phonons indicates that disorder induced LO-TO optical mode coupling can be an effective tool in assessing the structural quality of the b-Si. The same phonons are likely coupled to electrons in visible region PL transitions. Field emission properties of these nanoscopic features are demonstrated indicating the influence of the tip shape on the emission. Overall properties are discussed in terms of the surface morphology of the nanowhiskers.
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