Near-Infrared Surface Plasmon Resonance Measurements of Ultrathin Films. 2. Fourier Transform SPR Spectroscopy
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- 作者：Anthony G. Frutos ; Stephen C. Weibel ; and Robert M. Corn
- 刊名：Analytical Chemistry
- 出版年：1999
- 出版时间：September 15, 1999
- 年：1999
- 卷：71
- 期：18
- 页码：3935 - 3940
- 全文大小：121K
- 年卷期：v.71,no.18(September 15, 1999)
- ISSN：1520-6882
文摘
The application of surface plasmon resonance (SPR)measurements to the study of ultrathin organic filmsadsorbed onto gold surfaces utilizing near-infrared (NIR)excitation from a Fourier transform (FT) spectrometer isdescribed. The FT-SPR experiment measures the NIRreflectivity spectrum from a prism/gold film/water assembly at a fixed angle of incidence approximately 1-2
greater than the critical angle. A strong reflectivity minimum is observed in the FT-SPR spectrum; this minimumcan be shifted from 12 000 to 6000 cm-1 by tuning theangle of incidence. Upon adsorption of a thin biopolymerfilm from solution, a shift in the minimum is observedthat can be correlated to a film thickness using Fresnelcalculations. From experiments on the adsorption ofelectrostatically bound poly(lysine)/poly(glutamic acid)multilayers, an ~60-cm-1 shift per 10-Å change in filmthickness was measured. Frequency shifts of 2 cm-1(corresponding to a thickness change of the polymer layerof ~0.3 Å) can be easily measured from the FT-SPRspectra, demonstrating that this technique has sensitivityequivalent to or better than other visible SPR angle shiftor wavelength shift measurements. Furthermore, theability to perform FT-SPR measurements over a widerange of NIR wavelengths allows one to avoid any absorption bands that might otherwise interfere with the analysis.
greater than the critical angle. A strong reflectivity minimum is observed in the FT-SPR spectrum; this minimumcan be shifted from 12 000 to 6000 cm-1 by tuning theangle of incidence. Upon adsorption of a thin biopolymerfilm from solution, a shift in the minimum is observedthat can be correlated to a film thickness using Fresnelcalculations. From experiments on the adsorption ofelectrostatically bound poly(lysine)/poly(glutamic acid)multilayers, an ~60-cm-1 shift per 10-Å change in filmthickness was measured. Frequency shifts of 2 cm-1(corresponding to a thickness change of the polymer layerof ~0.3 Å) can be easily measured from the FT-SPRspectra, demonstrating that this technique has sensitivityequivalent to or better than other visible SPR angle shiftor wavelength shift measurements. Furthermore, theability to perform FT-SPR measurements over a widerange of NIR wavelengths allows one to avoid any absorption bands that might otherwise interfere with the analysis.