Using UV/Vis and IR light to Interrogate surfaces

• UV-Vis spectra can be obtained on quartz slides by transmission or reflectance• Spectroscopic ellipsometry can provide film thickness• IR spectra of surfaces usually obtained by reflectance• Raman scattering spectra can be “surface enhanced” and/or “resonance enhanced”

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J. F. Rusling and A.-E. F. Nassar, "Enhanced Electron Transfer for Myoglobin in Surfactant Films on Electrodes" J. Am. Chem. Soc., 1993, 115, 11891-11897.

Spectroscopic ellipsometry

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Ellipsometry is a sensitive optical technique for determining properties of surfaces and thin films. If linearly polarized light of a known orientation is reflected at oblique incidence from a surface then the reflected light is elliptically polarized. The shape and orientation of the ellipse depend on the angle of incidence, the direction of the polarization of the incident light, and the reflection properties of the surface. Modeling the data gives film thickness. (Source; see previous slide)

Yur i M. Lvov, James F. Rusling, D. Laurence Thomsen, Fotios Papadimitrakopoulos, Takeshi

Kawakami and Toyoki Kunitake, “High-Speed Multilayer Film Assembly by Alternate Adsorption of Silica Nanoparticles and Linear Polycation”, J. Chem. Soc., Chem. Commun. 1998, 1229-1230.

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LbL film of polycation and 45 nm silica

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d = 173 nm

= measured elliptical angle; = incidence angle of light on sample

Film characterization - Quartz Crystal Microbalance (QCM)

Oscillation freq. ~ (mass)-1

Adsorbed layer mass and thickness

M/A (g cm-2) = -ΔF (Hz) / (1.83 x 108)

d (nm) ≈ - (-0.016±0.002) ΔF (Hz)

Ru = RuPVP polymer

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Yur i M. Lvov, James F. Rusling, D. Laurence Thomsen, Fotios Papadimitrakopoulos, Takeshi

Kawakami and Toyoki Kunitake, “High-Speed Multilayer Film Assembly by Alternate Adsorption of Silica Nanoparticles and Linear Polycation”, J. Chem. Soc., Chem. Commun. 1998, 1229-1230.

Reflectance-absorbance IR spectroscopy

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Amide I & II

CH2 bending DDAB

RAIR ofMyoglobin-DDAB films

K. Suga and J. F. Rusling, "Structural Characterization of Surfactant and Clay-Surfactant Films of Micrometer Thickness by FT-IR Spectroscopy", Langmuir, 1993, 9, 3649-3655.

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From RAIR analysis of angular dependence- HC chains oriented ~30o to normal

K. Suga and J. F. Rusling, "Structural Characterization of Surfactant and Clay-Surfactant Films of Micrometer Thickness by FT-IR Spectroscopy", Langmuir, 1993, 9, 3649-3655.

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Resonance Raman Spectroscopy

Up to 106 enhancement in signal

Resonance Raman excitation in the UV-range to obtain selectively enhanced signals of DNA/RNA and aromatic amino acids (see Figure 1). Juergen Popp. Biomedical Optics & Medical Imaging, Identification of micro-organisms by

Raman spectroscopy,5 September 2007, SPIE Newsroom. DOI: 10.1117/2.1200708.0856 http://images.google.com/imgres?imgurl=http://www.spie.org/Images/Graphics/Newsroom/Imported/0856/0856_fig1.jpg&imgrefurl=http://spie.org/x16083.xml%3Fhighlight%3Dx2416&usg=__1Bv0gGpEHM5NG35ziyiUEnAL664=&h=1796&w=2591&sz=1926&hl=en&start=18&um=1&tbnid=SCv9PVsQsc9eyM:&tbnh=104&tbnw=150&prev=/images%3Fq%3Dresonance%2Braman%2Bimages%26hl%3Den%26client%3Dfirefox-a%26channel%3Ds%26rls%3Dorg.mozilla:en-US:official%26sa%3DG%26um%3D1

Identification of micro-organisms by Resonance Raman

Mildred S. Dresselhaus; Ado JorioI; Marcos A. PimentaI, Anais da Academia Brasileira de Ciências. vol.78 no.3 Rio de Janeiro Sept. 2006doi: 10.1590/S0001-37652006000300004 Resonance Raman spectroscopy in one-dimensional carbon materials

Carbon Nanotubes

Surface enhanced Raman spectroscopy

Rough Au surface

Au or Ag NPs

Figure 1. Surface-enhanced Raman spectra of 1-methyl adenine (10−5 mol L−1) in presence of a silver hydrosol prepared by the reduction of [Ag(NH3)2]+ with D(+)−xylose. The average particle size is 55nm. Silver hydrosols were activated by 0.002 (A), 0.01 (B), and 0.1 mol L−1 (C) of NaCl. The Raman spectrum of 1−methyl adenine (10−2 mol L−1) in deionised water (D) is included for comparison purposes.

Jana Soukupová, Robert Prucek, Libor Kvítek, and Aleš PanáčekImproving the molecular specificity of surface-enhanced Raman spectroscopyThe synthesis of silver colloid particles with controlled size significantly increases the application range of surface-enhanced Raman spectroscopy.23 September 2007, SPIE Newsroom. DOI: 10.1117/2.1200709.0835

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cancer imaging with Raman

Two different boosters were used - gold-based nanoparticles and carbon nanotubes - which were attached to a tumour-seeking peptide and tracked as they moved around the body

S. Keren et al, Proc. Natl. Acad. Sci., 2008, DOI: 10.1073/pnas.0710575105M Schipper et al, Nat. Nanotech., 2008, DOI:10.1038/nnano.2008.68

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