UV-visible diffuse reflectance spectra

Fig. 36. UV-visible diffuse reflectance spectra and elemental analysis data for Ti-SBA-15 (1) sample 1 (2) sample 2 (3) sample 3 and (4) sample 1 after treatment with 30% H202 [from Trukhan et al. (234)].

Recently, a large anionic pigment has been intercalated into an LDH host by ion-exchange of an Mg/Al LDH nitrate precursor with a solution of C.I. Pigment Red 48 2 (the calcium salt of 4-((5-chloro-4-methyl-2-sulfophenyl)azo)-3-hydroxy-2-naphthalene-carboxylic acid), in ethane-1,2-diol [215]. The UV-visible diffuse reflectance spectra of C.I. Pigment Red... 

UV-Visible diffuse reflectance spectra also show that vanadium is mainly present as V in V-containing silicalite samples. TPR and XPS results are in agreement with this conclusion. In addition, XPS data indicate that V is homogeneously dispersed in VSU545, whereas in VSill 17 part of the vanadium is segregated on the external surface of the silicalite samples. 

The accessibility of the primary amine functions of chitosan has been quantified in organic solvent by formation of a salicylaldimine Schiff base upon treatment with salicylaldehyde. When contacting salicylaldehyde the aerogel beads of chitosan become yellow and their UV-visible diffuse reflectance spectra exhibit the absorption band at 318 nm, characteristic of the Schiff base. Quantitative GC analysis of the remaining salicylaldehyde in the solution allows calculation of the fraction of reacted amino groups, which corresponds to the fraction of accessible sites. In the aerogel formulation, up to 70% of the amine groups are accessible [92]. 

Figure 4. (a) UV-visible diffuse reflectance spectra of 2(coiled)/Cab-0-Sil and 2(uncoiled)/Cab-0-Sil composites, and (b) the same samples after deposition... 

Silver-containing ceramic catalyst prepared by impregnating acid washed kaolin with silver nitrate solution after calcination in air at 1200 °C appeared to be highly active in the oxidation of methanol to formaldehyde. In this catalyst the silver was stabilized by the presence of [AIO4] in ionic form. Under the reaction conditions, the silver ions were partially reduced by the atomic hydrogen released from methanol and formed metallic particles. XPS and UV-Visible diffuse reflectance spectra (UV-Vis DRS) revealed that after the reaction about one-third of silver in the catalyst was still in ionic state. 

Fig. 2 UV-visible diffuse reflectance spectra for (Gai tZn ,)(Ni A) with various compositions (x)...

Fig. 6.14 UV-visible diffuse reflectance spectra of bare and N-doped Ti02 (anatase). The diagram is adapted from [96] with permission from the American Chemical Society...

Another method for the intercalation of metalloporphy-rins into clays has been explored using porphyrins and metalloporphyrins as organic templates in the hydrothermal synthesis of layered silicates. X-ray powder-diffraction data indicate that the porphyrins are intercalated parallel to the silicate layers. Microanalysis and UV-visible diffuse-reflectance spectra indicate that the porphyrins are incorporated intact. 

UV-visible diffuse reflectance spectra were recorded on a Beckman UV 5270 spectrometer in the 700-230 nm range. 

Figure 8.23 UV-visible diffuse reflectance spectra ofCe-Ca based (top) oxides and (bottom) oxyfluorides. Reproduced with the permission of ACS or American Chemical Society...

UV-visible diffuse reflectance spectra of polymeric Pd(p-Et2N)TPP and Ru(CO)(p-Et2N)TPP(t-Bupy) in aqueous 0,1 M TEAP solution. Electroreduction at 0.6 V.)... 

Ultraviolet-visible (UV-vis) diffuse reflectance spectra of supported WOx samples and standard W compounds were obtained with a Varian (Cary 5E) spectrophotometer using polytetrafluoroethylene as a reference. The Kubelka-Munk function was used to convert reflectance measurements into equivalent absorption spectra [12]. Spectral features of surface WOx species were isolated by subtracting from the W0x-Zr02 spectra that of pure Z1O2 with equivalent tetragonal content. All samples were equilibrated with atmospheric humidity before UV-vis measurements. 

Ground-state absorption studies of the probe molecules adsorbed within zeolites were performed by UV-visible diffuse reflectance spectroscopy. Cationic form of the zeolite without probe molecule was used as a comparison sample. The remission function was calculated by using the Kubelka-Munk equation. Steady-state photoluminescence studies were carried out with the Hilger spectrofluorimeter. The spectra were recorded at room temperature and 77 K, respectived. 

A protonated form of Beta-zeolite with Si02/Al20j molar ratio equal to 20 was used for the sample preparation. The gold concentration in the samples was analyzed by energy dispersive spectroscopy. State of gold was studied by UV-visible diffuse reflectance spectroscopy. The spectra presented in Figs. 1,2 were obtained by subtraction of the support spectmm from the spectra of Au supported samples. 

The UV-visible diffuse reflectance spectrum of N-doped HO2 (anatase), which was prepared by the sol-gel method, is compared with that of bare T1O2 (anatase) in Fig. 6.14. The two spectra essentially differ for the broad absorption in the... 

Figure 7, UV-visible diffuse reflectance and absorption spectra of Pd(p-Et2N)TPP in CHaCN, 0.1 M TBAP solution. (Controlled-potential electroreduction of the film at 0.7 V and controlled-potential electrooxidation of solution at 0.9 V.)...

The progressive increase in the extent of POM reduction, as evidenced by the ultraviolet visible diffuse reflectance (UV-vis DR) spectra of catalysts downloaded after different reaction times during catalyst equilibration. 

The electronic transitions of silicalite and TS-1 in the UV-visible spectrum have provided significant information about the structure of TS-1. The diffuse reflectance spectra of the two materials (Fig. 11) show a strong transition at 48,000 cm-1 that is present in the spectrum of TS-1 and absent from that of silicalite. This transition must be associated with a charge-transfer process localized on Tiiv. The frequency of this transition is modified by the presence of H20 (Fig. 12). As the H20 partial pressure increases, the peak at 48,000 cm- is progressively eroded with formation of a lower-frequency absorption, which reaches a new stable maximum value at 42,000 cm. These frequencies come very close to those that can be calculated by the Jorgensen equation for Tiiv tetrahedrally and octahedrally coordinated to oxygen, respectively. Furthermore,... 

All ground state diffuse reflectance spectra were recorded using a Phillips PU8800 UV-Visible spectrophotometer equipped with an integrating sphere, interfaced to an Elonex PC-386SX computer. These ground state diffuse reflectance spectra were measured relative to a BaSC>4 white reflectance standard (Eastman Kodak Ltd.). 

Figure 5.27 Difference diffuse reflectance spectra of powdered Zr02 irradiated with all UV/visible wavelengths for 45 min (1) in vacuo DRS(vac) = Rq -R/,v(vac) (2) in the presence of O2 P = 100 Pa DRS(02) = Ro - Rav(02) (3) in the presence of of H2 P = 100 Pa DRS/Hz) = Rq - R/,v(H2). Reprinted in part with permission from Emeline et al (1998b). Copyright (1998) American Chemical Society.

V wide-line NMR spectra were collected on a Bmker MSL 300 FT NMR spectrometer operating at 78.9 MHz and equipped with a special probe head for measurements in the absence of air. UV-Visible-NIR diffuse reflectance spectra (DRS) were measured in air using a Perkin Elmer Lamda 19 instrument after transformation of reflectivity (R) according to the Kubelka-Munk function F(R) = (l-R)V2R.o. BaS04 was used as a reference. 

To gain information on metal surface compounds of both photoimmobilized and immobilized samples their diffuse reflectance spectra in IR, visible and UV region were measured using spectrophotometer "Hitachi-340". ESR spectra of catalysts iso were examined using radiospectrometer "Varian-E-9". 

Diffuse Reflectance spectra (DRS) of samples were recorded using a Caiy 5 spectrometer with a diffuse reflectance accessory in the wavelength range 200-2500 nm, covering UV, visible and near-infrared regions. 

As seen in Fig. 9.8, ultraviolet-visible diffuse reflection (UV-Vis) spectra shows a strong absorption band from 275 to 500 nm, which is derived from the 4/ 5d transition of Eu " ions [39]. In addition. Fig. 9.8 shows the photoluminescence excitation (PLE) and photoluminescence emission (PL) of NaBaScSi2O7 0.1Eu phosphor. The PLE spectmm indicates the typically broad... 

Diffuse reflectance spectra in the UV-visible-near IR range were recorded on a Beckman 5270 spectrometer equipped with an integration sphere and a double monochromator. BaS04 was us as reference. 

The UV-visible-near IR diffuse reflectance spectra of the en-SiOa+INi, ENien and ENien+INi samples exhibit three d-d transitions, characteristic of nickel complexes in oct edral symetry. In the following, we will only consider the Vi band due to the A2g — T2g transition, because the V2 and V3 ones are less resolved. For the samples considered, the Vi band position varies between 890 nm which is characteristic of the [Ni(en)3] complex, e.g. present in the ENien samples, and 1160 nm which is characteristic of [Ni(H20)6] complex, e.g. present in standard impregnated INi samples (Table 3) [2]. 

---