TY - JOUR
T1 - Orientational analysis of dodecanethiol and p-nitrothiophenol SAMs on metals with polarisationdependent SFG spectroscopy
AU - Cecchet, Francesca
AU - Lis, Dan
AU - Guthmuller, Julien
AU - Champagne, Benoît
AU - Caudano, Yves
AU - Silien, Christophe
AU - Mani, Alaa Addin
AU - Thiry, Paul A.
AU - Peremans, André
PY - 2010/2/22
Y1 - 2010/2/22
N2 - Polarisation-dependent sum frequency generation (SFG) spectroscopy is used to investigate the orientation of molecules on metallic surfaces. In particular, self-assembled monolayers (SAMs) of dodecanethiol (DDT) and of p-nitrothiophenol (p- NTP), grown on Pt and on Au, have been chosen as models to highlight the ability of combining ppp and ssp polarisations sets (representing the polarisation of the involved beams in the conventional order of SFG, Vis and IR beam) to infer orientational information at metallic interfaces. Indeed, using only the ppp set of data, as it is usually done for metallic surfaces, is not sufficient to determine the full molecular orientation. We show here that simply combining ppp and ssp polarisations enables both the tilt and rotation angles of methyl groups in DDT SAMs to be determined. Moreover, for p-NTP, while the SFG active vibrations detected with the ppp polarisation alone provide no orientational information, however, the combination with ssp spectra enables to retrieve the tilt angle of the p- NTP 1,4 axis. Though orientational information obtained by polarisation-dependent measurements has been extensively used at insulating interfaces, we report here their first application to metallic surfaces.
AB - Polarisation-dependent sum frequency generation (SFG) spectroscopy is used to investigate the orientation of molecules on metallic surfaces. In particular, self-assembled monolayers (SAMs) of dodecanethiol (DDT) and of p-nitrothiophenol (p- NTP), grown on Pt and on Au, have been chosen as models to highlight the ability of combining ppp and ssp polarisations sets (representing the polarisation of the involved beams in the conventional order of SFG, Vis and IR beam) to infer orientational information at metallic interfaces. Indeed, using only the ppp set of data, as it is usually done for metallic surfaces, is not sufficient to determine the full molecular orientation. We show here that simply combining ppp and ssp polarisations enables both the tilt and rotation angles of methyl groups in DDT SAMs to be determined. Moreover, for p-NTP, while the SFG active vibrations detected with the ppp polarisation alone provide no orientational information, however, the combination with ssp spectra enables to retrieve the tilt angle of the p- NTP 1,4 axis. Though orientational information obtained by polarisation-dependent measurements has been extensively used at insulating interfaces, we report here their first application to metallic surfaces.
KW - Density functional calculations
KW - Self-assembled monolayers
KW - Sum frequency generation
KW - Surface analysis
KW - Vibrational spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=77049109644&partnerID=8YFLogxK
U2 - 10.1002/cphc.200900733
DO - 10.1002/cphc.200900733
M3 - Article
AN - SCOPUS:77049109644
SN - 1439-4235
VL - 11
SP - 607
EP - 615
JO - ChemPhysChem
JF - ChemPhysChem
IS - 3
ER -