Diffuse reflectance FTIR spectroscopy

Ean Q, Pu C, Ley KL, Smotkin ES. 1996. In situ FTIR-diffuse reflectance spectroscopy of the anode surface in a direct methanol fuel cell. J Electrochem Soc 143 L21-L23. 

An analogous ship-in-bottle complex, [VO(bpy)2]2+-NaY, could be designed starting from a vanadyl exchanged Y zeolite upon bpy addition.[97] Strong spectroscopic proof for the formation of such complex was evident from FT-Raman, FTIR, diffuse reflectance spectroscopy, XPS and EPR as follows ... 

FTIR diffuse reflectance spectroscopy was recently applied by Kazanski et al. (61) to monitor the interactions of molecular hydrogen with silica,... 

In situ FTIR diffuse reflection spectroscopy (FTIR-DRS) has been routinely used to track various adsorbates, but the specific adsorption sites (e.g., on the Pt or Ru site) carmot be determined with this technique." Further it carmot be used to track OH and H adsorption, which are both of significant importance in electrochemical studies. To om knowledge, adsorbed OH has not yet been directly observed on any Pt anodes except via the Ap XANES technique. Thus, the evidence for OH formation had to come previously from the coincidence of the potential for the onset of water activation and the CO oxidation peak in CV cmves (e.g., see Fig. 6 below). 

Interactions between a steel surface and an ethylene-vinyl acetate copolymer grafted with maleic anhydride were investigated by FTIR diffuse reflectance spectroscopy. The failed surfaces obtained after a mechanical separation of the polymer/steel assemblies were analysed. A two-step mechanism was proposed the opening of the anhydride cycle by a hydrolysis reaction, leading to the formation of a carboxylic diacid, followed by the reaction of the acid with some oxidised metallic elements present at the metal surface. This study underlines the contribution of FTIR reflectance techniques to the understanding of adhesion mechanisms. 7 refs. 

The problems discussed above may be circumvented by eliminating the mobile phase before measuring the spectra of the eluites, as first demonstrated by Shafer et al. [379] for pSFC-FTIR. Each eluite was deposited on a moving glass plate, on which a layer of powdered KC1 or KBr had been laid down from methanol slurry for diffuse reflectance spectroscopy (SFC-DRIFTS). Solvent elimination SFC-FTIR after deposition of the eluites on to a moving ZnSe substrate is quite straightforward the window is moved to the... 

An infrared spectrum is a plot of percent radiation absorbed versus the frequency of the incident radiation given in wavenumbers (cm ) or in wave length ( xm). A variation of this method, diffuse reflectance spectroscopy, is used for samples with poor transmittance, e.g. cubic hematite crystals. Increased resolution and sensitivity as well as more rapid collection of data is provided by Fourier-transform-IR (FTIR), which averages a large number of spectra. Another IR technique makes use of attenuated total reflectance FTIR (ATR-FTIR) often using a cylindrical internal reflectance cell (CIR) (e.g. Tejedor-Tejedor Anderson, 1986). ATR enables wet systems and adsorbing species to be studied in situ. 

The adsorption of furan, 2,5-dihydrofuran and tetrahydrofuran on sodium-ion exchanged faujasites with different Si/Al ratios was studied by combining temperature-programmed desorption (TPD), inelastic neutron scattering (INS), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), quantum mechanical computations and Monte-Carlo simulations. 

Mesoporous vanadosilicate molecular sieves with MCM-48 structure and atomic SiA ratio 30-200 have been synthesized using vanadyl sulphate as the source of vanadium. The product was characterized using X-ray diffraction (XRD), Nj adsorption analysis, transmision electron microscopy (TEM), electron spin resonance (ESR), Fourier-transform Infrared (FTIR), Diffuse reflectance UV-visible spectroscopy (UV-vis) and V solid state NMR. A noticeable decrease in unit cell parameters and main pore diameter was observed. Thus, a strong interaction between vanadium and mesoporous wall can be suggested. 

FTIR-DRS Fourier transform infrared diffuse reflection spectroscopy... 

Anatase, rutile, and brookite Ti02 can be prepared with a simple sol-gel procedure that allows one to avoid any calcination treatment. These materials have been extensively studied in the partial oxidation of aromatic alcohols in aqueous medium [65-70]. Their electronic properties have been investigated by diffuse reflectance spectroscopy and quasi-Fermi level measurements [70] the values of band gap, valence band, and conduction band edges are almost identical for all the samples in which anatase phase is predominant, whereas appreciable differences can be noticed in the presence of high amounts of rutile. ATR-FTIR... 

Surface characterization by spectroscopic techniques yields information on the functional groups and elemental composition on the surface of polymeric biomaterials. The most common spectroscopic tools used for biomedical polymers are X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), and Fourier transform infrared spectroscopy (FTIR) (diffuse reflectance and attenuated total internal reflectance modes). Each of these techniques is discussed in the succeeding text. 

AA spectroscopy was used to study the rate and extent of metal incorporation under the above conditions. Powder X-ray diffractomctry (Philip PW1710), FTIR (Peridn Elmer 1710), diffuse reflectance spectroscopy (Perkin Elmer Lamda 9 uv-vis near ir photospectrometer), XPS (Kratos ES300 with A1 radiation at 1468.6 ev), ESR (Varian E3 calibrated with DPPHO and TEM (Joel Instruments CXIOO) were used to confirm the formation of this ordered polymeric Rh+ network on the oxide surface. TPR and in-situ FTIR were also used to study the thermal stability of the supported and unsupported complexes in H2, CO and air. The total surface area of the oxide-suppirated catalysts was measured by BET N2 adsorption (Carlo Erba Soiptomatic 1800) at 77K. 

A Fourier transform infrared spectrophotometer (FTIR, model-IR Prestige-21, Schimadzu Corporation, Japan) was used for the structural determination of functional groups and compounds. The FTIR spectra of modified and unmodified clay in the solid state using potassium bromide (KBr) as a reference material were recorded by diffuse reflectance spectroscopy (DRS technique). This technique consists of preparation of sample by mixing about 0.5 mg of powder sample with 50 mg of high-purity infrared-grade KBr powder (Aldrich). The KBr was previously oven dried to reduce the interference of water. The spectra were recorded in the wave number range of 4000—400 cm with a resolution of 4 cm and 20 scans were carried for each sample in transmittance mode. 

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]. 

Characterization of the Cu-ZSM-5 catalyst by in-situ diffuse reflectance FTIR spectroscopy after treatments in CO, air and NjO is presented in figure 10, the CO adsorption in figure 11. 

FTIR instrumentation is mature. A typical routine mid-IR spectrometer has KBr optics, best resolution of around 1cm-1, and a room temperature DTGS detector. Noise levels below 0.1 % T peak-to-peak can be achieved in a few seconds. The sample compartment will accommodate a variety of sampling accessories such as those for ATR (attenuated total reflection) and diffuse reflection. At present, IR spectra can be obtained with fast and very fast FTIR interferometers with microscopes, in reflection and microreflection, in diffusion, at very low or very high temperatures, in dilute solutions, etc. Hyphenated IR techniques such as PyFTIR, TG-FTIR, GC-FTIR, HPLC-FTIR and SEC-FTIR (Chapter 7) can simplify many problems and streamline the selection process by doing multiple analyses with one sampling. Solvent absorbance limits flow-through IR spectroscopy cells so as to make them impractical for polymer analysis. Advanced FTIR... 

Samples were characterized by FTIR spectroscopy with a Perkin Elmer (Spectrum BX) spectrometer using KBr pressed disks as matrices. The DRIFT experiments were carried out with a Broker IFS 55 spectrometer equipped with a Thermo Spectra Tech reacting cell. UV-vis Diffuse Reflectance spectra were recorded on a Perkin Elmer Lambda 45 spectrophotometer equipped with a diffuse reflectance attachment. Raman spectra were collected with Perkin Elmer system 2000 NIR FT-Raman using as excitation radiation the 5th harmonic of a diode pumped Nd YAG laser (1065 nm). 

Persson, I., Persson, P., Valli, M., Fozo, S., Malmensten, B., 1991. Reaction on sulphide mineral surfaces in connection with xanthate flotation studied by diffuse reflectance FTIR spectroscopy, atomic absorption spectrophotometry and calorimetry. In K. S. E. Forssberg (ed.). Flotation of Sulphide Mineral. Inter. J. Miner. Process, 33 67 - 81 Peters, E., 1977. The electrochemistry of sulphide minerals. In J. O M. Bockris, D. A. J. Rand, B. J. Weich (eds.). Trends in Electrochemistry. New York Plenum Press, 267 - 290 Peters, E., 1986. Leaching of sulphides. In P. Sortunasundaran (ed.). Advances in Mineral Processing. Proc. Sym. Honoring N. Arbiter on His 75th Birthday, SME, Inc. Colorado, 445-462... 

Another similar study of crystallization was performed where on-line ATR-FTIR spectroscopy was used to provide concentration information, however on-line diffuse reflectance Fourier-transform infrared... 

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