Infrared reflectance spectroscopy

Vibrational Spectroscopy. Infrared absorption spectra may be obtained using convention IR or FTIR instrumentation the catalyst may be present as a compressed disk, allowing transmission spectroscopy. If the surface area is high, there can be enough chemisorbed species for their spectra to be recorded. This approach is widely used to follow actual catalyzed reactions see, for example. Refs. 26 (metal oxide catalysts) and 27 (zeolitic catalysts). Diffuse reflectance infrared reflection spectroscopy (DRIFT S) may be used on films [e.g.. Ref. 28—Si02 films on Mo(llO)]. Laser Raman spectroscopy (e.g.. Refs. 29, 30) and infrared emission spectroscopy may give greater detail [31]. 

In situ Fourier transform infrared and in situ infrared reflection spectroscopies have been used to study the electrical double layer structure and adsorption of various species at low-index single-crystal faces of Au, Pt, and other electrodes.206"210 It has been shown that if the ions in the solution have vibrational bands, it is possible to relate their excess density to the experimentally observed surface. 

Reaction products can also be identified by in situ infrared reflectance spectroscopy (Fourier transform infrared reflectance spectroscopy, FTIRS) used as single potential alteration infrared reflectance spectroscopy (SPAIRS). This method is suitable not only for obtaining information on adsorbed products (see below), but also for observing infrared (IR) absorption bands due to the products immediately after their formation in the vicinity of the electrode surface. It is thus easy to follow the production of CO2 versus the oxidation potential and to compare the behavior of different electrocatalysts. 

It is only since 1980 that in situ spectroscopic techniques have been developed to obtain identification of the adsorbed intermediates and hence of reliable reaction mechanisms. These new infrared spectroscopic in situ techniques, such as electrochemically modulated infrared reflectance spectroscopy (EMIRS), which uses a dispersive spectrometer, Fourier transform infrared reflectance spectroscopy, or a subtractively normalized interfacial Fourier transform infrared reflectance spectroscopy (SNIFTIRS), have provided definitive proof for the presence of strongly adsorbed species (mainly adsorbed carbon monoxide) acting as catalytic poisons. " " Even though this chapter is not devoted to the description of in situ infrared techniques, it is useful to briefly note the advantages and limitations of such spectroscopic methods. 

The different species formed by steps (18) to (20) or (18 ) to (20 ) have been detected by in situ infrared reflectance spectroscopy, and such dissociative steps are now widely accepted even if the exact nature of the species formed during (20) or (20 ) is still a subject of discussion. Several groups proposed the species (COH)3js as the main, strongly adsorbed species on the platinum surface, even though no absorption infrared band can be definitely attributed to (COH),, . However, the formyl-like species ( CHO), , . has been formally identified, since it gives an IR absorption band ataroimd 1690cm . ... 

The different kinds of adsorbed CO were observed by in situ infrared reflectance spectroscopy. The results showed that using bulk Pt-Ru alloys, the adsorbed CO species formed by dissociation of methanol, or from dissolved CO on the surface of the electrode, are different on R and on Ru. The adsorption of CO occurs on pure Pt and Ru and on alloys of different compositions, but a shift detected in the wave number of the... 

EMIRS electrochemically modulated infrared reflectance spectroscopy... 

In the early work of Bewick and Robinson (1975), a simple monochromator system was used. This is called a dispersive spectrometer. In the experiment the electrode potential was modulated between two potentials, one where the adsorbed species was present and the other where it was absent. Because of the thin electrolyte layer, the modulation frequency is limited to a few hertz. This technique is referred to as electrochemically modulated infrared reflectance spectroscopy (EMIRS). The main problem with this technique is that data acquisition time is long. So it is possible for changes to occur on the electrode surface. 

W.R. Hruschka, Data analysis wavelength selection methods, pp. 35-55 in P.C. Williams and K. Norris, eds. Near-infrared Reflectance Spectroscopy. Am. Cereal Assoc., St. Paul MI, 1987. P. Geladi, D. McDougall and H. Martens, Linearization and scatter-correction for near-infrared reflectance spectra of meat. Appl. Spectrosc., 39 (1985) 491-500. 

Beden B, Bewick A, Lamy C. 1983. A study by electrochemically modulated infrared reflectance spectroscopy of the electrosorption of formic acid at a platinum electrode. J Electroanal Chem 148 147-160. 

Infrared reflectance spectroscopy provides information on the vibrational states in the interphase. It can be interpreted in terms of molecular symmetry, force constants and chemical bond lengths. The intensity of the spectral peaks of the adsorbed molecules is determined both by standard... 

A method is available, utilising on-line near-infrared reflectance spectroscopy, for controlling the uniform application of poly (vinyl alcohol) size [198]. 

In recent years,3 4 however, there has been renewed interest in the study of the electrode/solution interface due in part to the development of new spectroscopic techniques such as surface-enhanced Raman spectroscopy,5-7 electrochemically modulated infrared reflectance spectroscopy and related techniques,8,9 second-harmonic generation,10-12 and others which give information about the identity and orientation of molecular species in the interfacial... 

Pierre [60] has reported a study of the characterisation of the surface of oil slicks by infrared reflective spectroscopy. A double-beam spectrophotometer was modified for studying the reflectance spectra (at angles of incidence 45°, 60°, 70°) of oil layers (20-30 xm thick) on the surface of water using pure water as reference. 

Downey, G., Dublin, I. Authentication of coffee bean variety by near-infrared reflectance spectroscopy of dried extracts. J. Sci. Food Agric. 71 (1), p. 41 —49, 1996... 

The infrared surface spectroscopic analysis was applied only to gas-solid surfaces imtil Bewick et al. succeeded ) to measure an in situ infiored spectra on electrode surfaces in electrochemical systems. They controlled the electrode potential and obtained the difference spectra between the measured and the reference potentials (EMIRS Electrochemically Modulated Infrared Reflectance Spectroscopy). This technique is employed in this theses also and discussed in detail in a later section. 

Ren, G., and Chen, F. (1999). Simultaneous quantification of ginsenosides in American ginseng (Panax quinquefolium) root powder by visible/near-infrared reflectance spectroscopy. /. Agric. Food Ghent. 47, 2771-2775. 

E.W. Ciurczak, R.P. Tourlini and M.P. Demkowicz, Determination of particle size of pharmacentical raw materials using near infrared reflectance spectroscopy. Spectroscopy, 1, 36-39 (1986). 

M. Blanco, J. Coello, H. Iturriaga, S. Maspoch, C. Pezuela and E. Russo, Control analysis of a pharmaceutical preparation by near-infrared reflectance spectroscopy a comparative study of a spinning module and fibre optic probe, Anal. Chim. Acta, 298, 183-191 (1994). 

S. Lonardi, R. Viviani, L. Mosconi, et al., Dmg analysis by near-infrared reflectance spectroscopy. Determination of the active ingredient and water content in antibiotic powders, J. Pharm. Biomed. Anal., 7, 303-308 (1989). 

P. Corti, E. Dreassi, G. Ceramelli, S. Lonardi, R. Viviani and S. Gravina, Near Infrared Reflectance Spectroscopy applied to pharmaceutical quality control. Identification and assay of cephalosporins, Analusis 19, 198-204 (1991). J.K. Drennen and R.A. Lodder, Pharmaceutical applications of near-infrared spectrometry, in Advances in Near Infrared Measurements, vol. 1, G. Patonay (ed.), JAI Press, Greenwich, CT, pp. 93-112, 1993. 

A.J. O Neil, R.D. Jee and A.C. Moffat, Measurement of the cumulative particle size distribution of microcrystalline cellulose using near infrared reflectance spectroscopy. Analyst, 124, 33-36 (1999). 

P.E. Luner, S. Majuru, J.J. Seyer and M.S. Kemper, Quantifying crystalline form composition in binary powder mixtures using near-infrared reflectance spectroscopy, Pharm. Dev. Tech., 5, 231-246 (2000). 

A.D. Patel, P.E. Luner and M.S. Kemper, Quantitative analysis of polymorphs in binary and multi-component powder mixtures by near-infrared reflectance spectroscopy, Int. J. Pharm. 206, 63-74. Erratum in Int. J. Pharm., 212, 295 (2000). 

M. Blanco, J. Coello, A. Eustaquio, H. Itturriaga and S. Maspoch, Development and validation of methods for the determination of miokamycin in various pharmaceutical preparations by use of near infrared reflectance spectroscopy, Analyst, 124, 1089-1092 (1999). 

Berardo, N. (1992) Measuring Italian ryegrass quality by near infrared reflectance spectroscopy (NIRS). In Murray, I. and Cowe, LA. (eds) Making Light Work Advances in Near Infrared Spectroscopy. VCH, Weinheim, Germany, pp. 272-276. 

Reeves, J.B. Ill and McCarty, G.W. (2001) Quantitative analysis of agricultural soils using near infrared reflectance spectroscopy and a fibre-optic probe. Journal of Near Infrared Spectroscopy 9, 25-34. 

HC Example 2 The goal of the project described here is to use HCA to help tenmne whether near-infrared reflectance spectroscopy (NIR) can be usedx> facilitate the sorting of recycled plastic containers. (This data set is also dismssed in Example 2 of KNN, Section 4.3.1.2.) Waste plastic containers were btained and the reflectance spectra measured in the range 1100-2500 nn. The materials represented in the data set are listed in Table 4.4. 

The raw data plots and experience with near-infrared reflectance spectroscopy indicates the need for preprocessing to miniinize the effects of scatter. However, to illustrate the effect of preprocessing on the analysis, no preprocessing will be performed for the first pass through the data. ... 

Dannetun P, Boman M, Stafstrom S, Salaneck WR, Lazzaroni R, Fredriksson C, Bredas JL, Zamboni R, Taliani C (1993) The chemical and electronic structure of the interface between aluminum and polythiophene semiconductors. J Chem Phys 99(l) 664-672 Ahn H, Whitten JE (2003) Vapor-deposition of aluminum on thiophene-terminated self-assembled monolayers on gold. J Phys Chem B 107(27) 6565-6572 Fisher GL, Flooper A, Opila RL, Jung DR, Allara DL, Winograd N (1999) The interaction between vapor-deposited A1 atoms and methylester-terminated self-assembled monolayers studied by time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy and infrared reflectance spectroscopy. J Electron Spectrosc Relat Phenom 98-99 139-148... 

Huck, C. et al., Quantitative Fourier transform near infrared reflectance spectroscopy (NIRS) compared to high performance liquid chromatography (HPLC) of a flavone in Primulae veris Flos extracts, Pharm. Pharmacol Lett., 9, 26, 1999. 

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