Restricted accessResearch articleFirst published online 2019-10
Orientational Analysis of Monolayers at Low Surface Concentrations Due to an Increased Signal-to-Noise Ratio (S/N) Using Broadband Sum Frequency Generation Vibrational Spectroscopy
spectroscopy was used to deduce the orientation of the terminal methyl (CH3) group of self-assembled monolayers (SAMs) at the air–solid and air–liquid interfaces at surface concentrations as low as 1% protonated molecules in the presence of 99% deuterated molecules. The SFG spectra of octadecanethiol (ODT) and deuterated octadecanethiol (d37 ODT) SAMs on gold were used for analysis at the air–solid interface. However, the eicosanoic acid (EA) and deuterated EA (d39 EA) SAMs on the water were analyzed at the air–liquid interface. The tilt angle of the terminal CH3 group was estimated to be ∼39 ° for a SAM of 1% ODT : 99% d37 ODT, whereas the tilt angle of the terminal CH3 group of the 1% EA : 99% d39 EA monolayer was estimated to be ∼32 °. The reliability of the orientational analysis at low concentrations was validated by testing the sensitivity of the SFG spectroscopy. A signal-to-noise (S/N) ratio of ∼60 and ∼45 was obtained for the CH3 symmetric stretch (SS) of 1% ODT : 99% d37 ODT and 1% EA : 99% d39 EA, respectively. The estimated increase in S/N ratio values, as a measure of the sensitivity of the SFG spectroscopy, verified the capacity to acquire the SFG spectra at low concentrations of interfacial molecules under ambient conditions. Overall, the orientational analysis of CH3 SS vibrational mode was feasible at low concentrations of protonated molecules due to increased S/N ratio. In support, the improved S/N ratio on varying incident power density of the visible beam was also experimentally demonstrated.
VidalF.BussonB.TadjeddineA.“Probing Electronic and Vibrational Properties at the Electrochemical Interface Using SFG Spectroscopy: Methanol Electro-Oxidation on Pt(110)”. Chem. Phys. Lett. 2005. 403(4): 324–328.
2.
FuL.LiuJ.YanE.C.“Chiral Sum Frequency Generation Spectroscopy for Characterizing Protein Secondary Structures at Interfaces”. J. Am. Chem. Soc. 2011. 133(21): 8094–8097.
3.
BarnetteA.L.BradleyL.C.VeresB.D., et al.“Selective Detection of Crystalline Cellulose in Plant Cell Walls with Sum Frequency Generation (SFG) Vibration Spectroscopy”. Biomacromol. 2011. 12(7): 2434–2439.
4.
WeeramanC.YatawaraA.K.BordenyukA.N., et al.“Effect of Nanoscale Geometry on Molecular Conformation: Vibrational Sum Frequency Generation of Alkanethiols on Gold Nanoparticles”. J. Am. Chem. Soc. 2006. 128(44): 14244–14245.
5.
BaldelliS.“Probing Electric Fields at the Ionic Liquid−Electrode Interface Using Sum Frequency Generation Spectroscopy and Electrochemistry”. J. Phys. Chem. B. 2005. 109(27): 13049–13051.
6.
AliagaC.BaldelliS.“Sum Frequency Generation Spectroscopy and Double-Layer Capacitance Studies of the 1-Butyl-3-Methylimidazolium Dicyanamide−Platinum Interface”. J. Phys. Chem. B. 2006. 110(37): 18481–18491.
7.
RosenB.A.HahnJ.L.MukherjeeP., et al.“In situ Spectroscopic Examination of a Low Overpotential Pathway for Carbon Dioxide Conversion to Carbon Monoxide”. J. Phys. Chem. C. 2012. 116(29): 15307–15312.
8.
YeS.KathiravanA.HayashiH., et al.“Role of Adsorption Structures of Zn–Porphyrin on TiO2 in Dye-Sensitized Solar Cells Studied by Sum Frequency Generation Vibrational Spectroscopy and Ultrafast Spectroscopy”. J. Phys. Chem. C. 2013. 117(12): 6066–6080.
9.
ShenY.R.“Surface Properties Probed by Second Harmonic and Sum Frequency Generation”. Nature. 1989. 337(6207): 519–525.
10.
ZhangD.GutowJ.EisenthalK.B.“Vibrational Spectra, Orientations, and Phase Transitions in Long Chain Amphiphiles at the Air/Water Interface: Probing the Head and Tail Groups by Sum Frequency Generation”. J. Phys. Chem. 1994. 98(51): 13729–13734.
11.
GopalakrishnanS.JungwirthP.TobiasD.J., et al.“Air-Liquid Interfaces of Aqueous Solutions Containing Ammonium and Sulfate: Spectroscopic and Molecular Dynamics Studies”. J. Phys. Chem. B. 2005. 109(18): 8861–8872.
12.
MaG.AllenH.C.“DPPC Langmuir. Monolayer at the Air-Water Interface: Probing the Tail and Head Groups by Vibrational Sum Frequency Generation Spectroscopy”. Langmuir. 2006. 22(12): 5341–5349.
13.
MirandaP.B.ShenY.R.“Liquid Interfaces: A Study by Sum Frequency Vibrational Spectroscopy”. J. Phys. Chem. B. 1999. 103(17): 3292–3307.
14.
ChanS.C.JangJ.H.CimatuK.L.A.“Orientational Analysis of Interfacial Molecular Groups of 2-Methoxyethyl Methacrylate Monomer Using Femtosecond Sum Frequency Generation Spectroscopy”. J. Phys. Chem. C. 2016. 120(51): 29358–29373.
15.
PremadasaU.I.AdhikariN.M.BaralS., et al.“Conformational Changes of Methacrylate-Based Monomers at the Air–Liquid Interface Due to Bulky Substituents”. J. Phys. Chem. C. 2017. 121(31): 16888–16902.
16.
CimatuK.L.A.ChanS.C.JangJ.H., et al.“Preferential Organization of Methacrylate Monomers and Polymer Thin Films at the Air Interface Using Femtosecond Sum Frequency Generation Spectroscopy”. J. Phys. Chem. C. 2015. 119(45): 25327–25339.
17.
AdhikariN.M.PremadasaU.I.CimatuK.L.A.“Sum Frequency Generation Vibrational Spectroscopy of Methacrylate-Based Functional Monomers at the Hydrophilic Solid-Liquid Interface”. Phys. Chem. Chem. Phys. 2017. 19(32): 21818–21828.
18.
BoughtonA.P.YangP.TesmerV.M., et al.“Heterotrimeric G Protein β1γ2 Subunits Change Orientation Upon Complex Formation with G Protein-Coupled Receptor Kinase 2 (GRK2) on a Model Membrane”. Proc. Natl. Acad. Sci. U.S.A. 2011. 108(37): E667–E673.
19.
WangC.-y.GroenzinH.ShultzM.J.“Surface Characterization of Nanoscale TiO2 Film by Sum Frequency Generation Using Methanol as a Molecular Probe”. J. Phys. Chem. B. 2004. 108(1): 265–272.
20.
AnfusoC.L.XiaoD.RicksA.M., et al.“Orientation of a Series of CO2 Reduction Catalysts on Single Crystal TiO2 Probed by Phase-Sensitive Vibrational Sum Frequency Generation Spectroscopy (PS-VSFG)”. J. Phys. Chem. C. 2012. 116(45): 24107–24114.
21.
YatawaraA.K.TiruchinapallyG.BordenyukA.N., et al.“Carbohydrate Surface Attachment Characterized by Sum Frequency Generation Spectroscopy”. Langmuir. 2009. 25(4): 1901–1904.
22.
MaozR.SagivJ.DegenhardtD., et al.“Hydrogen-Bonded Multilayers of Self-Assembling Silanes: Structure Elucidation by Combined Fourier Transform Infra-Red Spectroscopy and X-ray Scattering Techniques”. Supramol. Sci. 1995. 2(1): 9–24.
23.
VerreaultD.KurzV.HowellC., et al.“Sample Cells for Probing Solid/Liquid Interfaces with Broadband Sum Frequency Generation Spectroscopy”. Rev. Sci. Instrum. 2010. 81(6): 063111.
24.
StiopkinI.V.JayathilakeH.D.BordenyukA.N., et al.“Heterodyne Detected Vibrational Sum Frequency Generation Spectroscopy”. J. Am. Chem. Soc. 2008. 130(7): 2271–2275.
25.
LagutchevA.HambirS.A.DlottD.D.“Nonresonant Background Suppression in Broadband Vibrational Sum Frequency Generation Spectroscopy”. J. Phys. Chem. C. 2007. 111(37): 13645–13647.
26.
QuastA.D.WildeN.C.MatthewsS.S., et al.“Improved Assignment of Vibrational Modes in Sum Frequency Spectra in the CH Stretch Region for Surface-bound C18 Alkylsilanes”. Vib. Spectrosc. 2012. 61: 17–24.
27.
RichterL.J.Petralli-MallowT.P.StephensonJ.C.“Vibrationally Resolved Sum Frequency Generation with Broad Bandwidth Infrared Pulses”. Opt. Lett. 1998. 23(20): 1594–1596.
28.
GeA.M.PengQ.L.QiaoL., et al.“Molecular Orientation of Organic Thin Films on Dielectric Solid Substrates: A Phase-Sensitive Vibrational SFG Study”. Phys. Chem. Chem. Phys. 2015. 17(27): 18072–18078.
29.
BainC.D.DaviesP.B.OngT.H., et al.“Quantitative Analysis of Monolayer Composition by Sum Frequency Vibrational Spectroscopy”. Langmuir. 1991. 7(8): 1563–1566.
30.
MaG.AllenH.C.“Surface Studies of Aqueous Methanol Solutions by Vibrational Broad Bandwidth Sum Frequency Generation Spectroscopy”. J. Phys. Chem. B. 2003. 107(26): 6343–6349.
31.
DasS.K.SenguptaS.VelardeL.“Interfacial Surfactant Ordering in Thin Films of SDS-Encapsulated Single-Walled Carbon Nanotubes”. J. Phys. Chem. Lett. 2016. 7(2): 320–326.
32.
TyrodeE.HedbergJ.“A Comparative Study of the CD and CH Stretching Spectral Regions of Typical Surfactants Systems Using VSFS: Orientation Analysis of the Terminal CH3 and CD3 Groups”. J. Phys. Chem. C. 2012. 116(1): 1080–1091.
33.
ClarkeM.L.ChenZ.“Polymer Surface Reorientation After Protein Adsorption”. Langmuir. 2006. 22(21): 8627–8630.
34.
IwahashiT.IshiyamaT.SakaiY., et al.“Liquid/Liquid Interface Layering of 1-Butanol and [bmim] PF 6 Ionic Liquid: A Nonlinear Vibrational Spectroscopy and Molecular Dynamics Simulation Study”. Phys. Chem. Chem. Phys. 2015. 17(38): 24587–24597.
35.
MaG.AllenH.C.“Real-Time Investigation of Lung Surfactant Respreading with Surface Vibrational Spectroscopy”. Langmuir. 2006. 22(26): 11267–11274.
36.
TianK.LiH.YeS.“Methanol Perturbing Modeling Cell Membranes Investigated Using Linear and Nonlinear Vibrational Spectroscopy”. Chinese J. Chem. Phys. 2013. 26(1): 27–34.
37.
LambertA.G.DaviesP.B.NeivandtD.“Implementing the Theory of Sum Frequency Generation Vibrational Spectroscopy: A Tutorial Review”. Appl. Spectrosc. Rev. 2005. 40(2): 103–145.
38.
TakeshitaN.OkunoM.IshibashiT.-a.“Molecular Conformation of DPPC Phospholipid Langmuir. and Langmuir–Blodgett Monolayers Studied by Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy”. Phys. Chem. Chem. Phys. 2017. 19: 2060–2066.
39.
AvazbaevaZ.SungW.LeeJ., et al.“Origin of the Instability of Octadecylamine Langmuir Monolayer at Low pH”. Langmuir. 2015. 31(51): 13753–13758.
40.
SchleegerM.NagataY.BonnM.“Quantifying Surfactant Alkyl Chain Orientation and Conformational Order from Sum Frequency Generation Spectra of CH Modes at the Surfactant–Water Interface”. J. Phys. Chem. Lett. 2014. 5(21): 3737–3741.
41.
MeltzerC.PaulJ.DietrichH., et al.“Indentation and Self-Healing Mechanisms of a Self-Assembled Monolayer A Combined Experimental and Modeling Study”. J. Am. Chem. Soc. 2014. 136(30): 10718–10727.
42.
WeberJ.BalgarT.HasselbrinkE.“Conformational Disorder in Alkylsiloxane Monolayers at Elevated Temperatures”. J. Chem. Phys. 2013. 139(24): 244902.
43.
EwersB.W.BatteasJ.D.“Molecular Dynamics Simulations of Alkylsilane Monolayers on Silica Nanoasperities: Impact of Surface Curvature on Monolayer Structure and Pathways for Energy Dissipation in Tribological Contacts”. J. Phys. Chem. C. 2012. 116(48): 25165–25177.
44.
WangH.-F.GanW.LuR., et al.“Quantitative Spectral and Orientational Analysis in Surface Sum Frequency Generation Vibrational Spectroscopy (SFG-VS)”. Int. Rev. Phys. Chem. 2005. 24(2): 191–256.
45.
BeattieD.A.FraenkelR.WingetS.A., et al.“Sum-Frequency Spectroscopy of a Monolayer of Zinc Arachidate at the Solid−Solid Interface”. J. Phys. Chem. B. 2006. 110(5): 2278–2292.
ArnoldR.TerfortA.WöllC.“Determination of Molecular Orientation in Self-Assembled Monolayers Using IR Absorption Intensities: The Importance of Grinding Effects”. Langmuir. 2001. 17(16): 4980–4989.
48.
MountainR.D.HubbardJ.B.MeuseC.W., et al.“Molecular Dynamics Study of Partial Monolayer Ordering of Chain Molecules”. J. Phys. Chem. B. 2001. 105(39): 9503–9508.
49.
SantosG.M.BaldelliS.“Monitoring Localized Initial Atmospheric Corrosion of Alkanethiol-Covered Copper Using Sum Frequency Generation Imaging Microscopy: Relation Between Monolayer Properties and Cu2O Formation”. J. Phys. Chem. C. 2013. 117(34): 17591–17602.
50.
FangM.BaldelliS.“Surface-Induced Heterogeneity Analysis of an Alkanethiol Monolayer on Microcrystalline Copper Surface Using Sum Frequency Generation Imaging Microscopy”. J. Phys. Chem. C. 2017. 121(3): 1591–1601.
51.
UlmanA.“Formation and Structure of Self-Assembled Monolayers”. Chem. Rev. 1996. 96(4): 1533–1554.
52.
TsaoM.W.HoffmannC.L.RaboltJ.F., et al.“Studies of Molecular Orientation and Order in Self-assembled Semifluorinated n-Alkanethiols: Single and Dual Component Mixtures”. Langmuir. 1997. 13(16): 4317–4322.
53.
CimatuK.L.A.BaldelliS.“Spatially Resolved Surface Analysis of an Octadecanethiol Self-Assembled Monolayer on Mild Steel Using Sum Frequency Generation Imaging Microscopy”. J. Phys. Chem. C. 2007. 111(19): 7137–7143.
54.
GuoZ.ZhengW.HamoudiH., et al.“On the Chain Length Dependence of CH3 Vibrational Mode Relative Intensities in Sum Frequency Generation Spectra of Self Assembled Alkanethiols”. Surf. Sci. 2008. 602(23): 3551–3559.
55.
CurtisA.D.BurtS.R.CalcheraA.R., et al.“Limitations in the Analysis of Vibrational Sum Frequency Spectra Arising from the Nonresonant Contribution”. J. Phys. Chem. C. 2011. 115(23): 11550–11559.
56.
TyrodeE.LiljebladJ.F.“Water Structure Next to Ordered and Disordered Hydrophobic Silane Monolayers: A Vibrational Sum Frequency Spectroscopy Study”. J. Phys. Chem. C. 2013. 117(4): 1780–1790.
57.
VerreaultD.HuaW.AllenH.C.“From Conventional to Phase-Sensitive Vibrational Sum Frequency Generation Spectroscopy: Probing Water Organization at Aqueous Interfaces”. J. Phys. Chem. Lett. 2012. 3(20): 3012–3028.
58.
ZhuX.D.SuhrH.ShenY.R.“Surface Vibrational Spectroscopy by Infrared-Visible Sum Frequency Generation”. Phys. Rev. B. 1987. 35(6): 3047–3050.
59.
FrankenP.A.HillA.E.PetersC.W., et al.“Generation of Optical Harmonics”. Phys. Rev. Lett. 1961. 7(4): 118–119.
60.
HüttingerK.J.Höhmann-WienS.KrekelG.“A Method for the Determination of the Acid-Base Interactions and the Work of Adhesion at a Solid–Liquid Interface”. J. Adhes. Sci. Technol. 1992. 6(3): 317–331.
61.
DannJ.R.“Forces Involved in the Adhesive Process: II. Nondispersion Forces at Solid–Liquid Interfaces”. J. Colloid Interface Sci. 1970. 32(2): 321–331.
62.
HindA.R.BhargavaS.K.McKinnonA.“At the Solid/Liquid Interface: FTIR/ATR—The Tool of Choice”. Adv. Colloid Interface Sci. 2001. 93(1–3): 91–114.
63.
WieckowskiA.SavinovaE.R.VayenasC.G.Catalysis and Electrocatalysis at Nanoparticle Surfaces., New York: Marcel Dekker, 2003.
64.
FuL.MaG.YanE.C.Y.“In situ Misfolding of Human Islet Amyloid Polypeptide at Interfaces Probed by Vibrational Sum Frequency Generation”. J. Am. Chem. Soc. 2010. 132(15): 5405–5412.
65.
LiljebladJ.F.TyrodeE.ThormannE., et al.“Self-Assembly of Long Chain Fatty Acids: Effect of a Methyl Branch”. Phys. Chem. Chem. Phys. 2014. 16(33): 17869–17882.
66.
AkamatsuN.DomenK.HiroseC.“SFG Study of Two-Dimensional Orientation of Surface Methyl Groups on Cadmium Arachidate Langmuir–Blodgett Films”. J. Phys. Chem. 1993. 97(39): 10070–10075.
67.
ColavitaP.E.MineyP.G.TaylorL., et al.“Effects of Metal Coating on Self-Assembled Monolayers on Gold. 2. Copper on an Oligo(phenylene-ethynylene) Monolayer”. Langmuir. 2005. 21(26): 12268–12277.
68.
BoughtonA.P.AndricioaeiI.ChenZ.“Surface Orientation of Magainin 2: Molecular Dynamics Simulation and Sum Frequency Generation Vibrational Spectroscopic Studies”. Langmuir. 2010. 26(20): 16031–16036.
69.
ChenX.ChenZ.“SFG studies on Interactions Between Antimicrobial Peptides and Supported Lipid Bilayers”. Biochim. Biophys. Acta. 2006. 1758(9): 1257–1273.
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