Direct spectroscopic evidence for vanadium species in V-MCM-41 molecular sieve characterized by UV resonance Raman spectroscopy

Vanadium species in tetrahedral and octahedral coordination in V-MCM-41 molecular sieve are characterized by UV resonance Raman bands at 1070 and 930 cm(-1) respectively.

Coke formation during the methanol conversion to olefins in zeolites studied by UV Raman spectroscopy

Coke formation on/in ZSM-5, USY and SAPO-34 zeolites was investigated during the methanol conversion to olefins at temperatures from 298 to 773 K using ultraviolet (UV) Raman spectroscopy. The fluorescence interference that usually obscures the Raman spectra of zeolites in the conventional Raman spectroscopy, particularly for coked catalysts, can be successfully avoided in the UV Raman spectroscopy. Raman spectra are almost the same for adsorbed methanol on the three zeolites at room temperature. However, the Raman spectra of the surface species formed at elevated temperatures are quite different for the three zeolites. Coke species formed in/on SAPO-34 are mainly polyolefinic species, and in/on ZSM-5 are some aromatic species, but polyaromatic or substituted aromatic species are predominant in USY at high temperatures. Most of the coke species can be removed after a treatment with O-2 at 773 K, while some small amount of coke species always remains in these zeolites, particularly for USY. The main reason for the different behavior of coke formation in the three zeolites could be attributed to the different pore structures of the zeolites. (C) 2000 Elsevier Science B.V. All rights reserved.

Identifying framework titanium in TS-1 zeolite by UV resonance Raman spectroscopy

Framework titanium in Ti-silicalite-1 (TS-1) zeolite was selectively identified by its resonance Raman bands using ultraviolet (W) Raman spectroscopy. Raman spectra of the TS-1 and silicalite-1 zeolites were obtained and compared using continuous wave laser lines at 244, 325, and 488 nm as the excitation sources. It was only with the excitation at 244 nm that resonance enhanced Raman bands at 490, 530, and 1125 cm(-1) appeared exclusively for the TS-1 zeolite. Furthermore, these bands increased in intensity with the crystallization time of the TS-1 zeolite. The Raman bands at 490, 530, and 1125 cm(-1) are identified as the framework titanium species because they only appeared when the laser excites the charge-transfer transition of the framework titanium species in the TS-1. No resonance Raman enhancement was detected for the bands of silicalite-1 zeolite and for the band at 960 cm(-1) of TS-1 with any of the excitation sources ranging from the visible tb UV regions. This approach can be applicable for the identification of other transition metal ions substituted in the framework of a zeolite or any other molecular sieve.

UV Raman spectroscopic study on the synthesis mechanism of zeolite X

The synthesis of zeolite X is characterized by UV Raman spectroscopy, NMR spectroscopy, and X-ray diffraction. UV Raman spectra of the liquid phase of the synthesis system indicate that AI(OH); species are incorporated into silicate species, and the polymeric silicate species are depolymerized into monomeric silicate species during the early stage of zeolite formation. An. intermediate species possessing Raman bands at 307, 503, 858 and 1020 cm(-1) is detected during the crystallization ill the solid phase transformation. The intermediate species is attributed to the beta cage, the secondary building unit of zeolite X. A model for the formation of zeolite X is proposed, which involves four-membered rings connecting to each other via six-membered ring to form beta cages, then the beta cages interconnect via double six-membered rings to form the framework of zeolite X. (C) 2001 Elsevier Science B.V. All rights reserved.

Characterization of aluminosilicate zeolites by UV Raman spectroscopy

A series of aluminosilicate zeolites are characterized by UV Raman spectroscopy for the first time, and UV Raman spectra of various zeolites give strong and clear bands with high resolution, while conventional Raman spectra of these zeolites are difficult to obtain because of a strong background fluorescence. Additionally, these zeolites show several new bands in UV Raman spectroscopy. A summary of these UV Raman spectra over various zeolites suggests that the bands at 470-530, 370-430, 290-410, and 220-280 cm(-1) can be assigned to the bending modes of 4-, 5-, 6-, and 8-membered rings of aluminosilicate zeolites, respectively. Furthermore, it is found that the band intensity of zeolites in UV Raman spectroscopy is dependent on the Si/Al ratio. Moreover, the UV Raman spectra of crystallization, for zeolite X at various times show that, in the initial stage of crystallization, the 4-membered rings (510 cm(-1)) interconnect each other to form beta -cages with 6-membered rings (390 cm(-1)), which further crystallize to zeolite X. (C) 2001 Elsevier Science B.V. All rights reserved.

Quantitative and qualitative analysis of flavonoids in leaves of Adinandra nitida by high performance liquid chromatography with UV and electrospray ionization tandem mass spectrometry detection

The extract of Adinandra nitida leaves, named as Shiyacha in China, was studied by high performance liquid chromatography (HPLC)-ultraviolet detection-electrospray ionisation (ESI) tandem mass spectrometry (MS). Under the optimized condition, the analysis could be finished in 45 min on a Hypersil C18 column combined with negative ion detection using information-dependent acquisition (IDA) mode of a Q TRAP (TM) instrument. Six flavonoids were identified as epicatechin, rhoifolin, apigenin, quercitrin, camellianin A, and camellianin B among which rhoifolin was for the first time found in Shiyacha. And the fragment pathways of these flavonoids were elucidated. Furthermore, with epicatechin, rhoifolin, and apigenin as markers, the quality control method for Shiyacha and its relevant product was firstly established. Calibration linearity was good (R-2 > 0.9992) over a three to four orders of magnitude concentration range with an S/N = 3 detection limit of 2.5 ng. (c) 2004 Elsevier B.V. All rights reserved.

Arctic microorganisms respond more to elevated UV-B radiation than CO2

David Johnson, Colin D. Campbell, John A. Lee, Terry V. Callaghan and Dylan Gwynn-Jones (2002). Arctic microorganisms respond more to elevated UV-B radiation than CO2. Nature, 416 (6876) pp.82-83 Sponsorship: NERC / EU / Swedish Academy of Sciences RAE2008

Searching the Sky with CONFIGR-STARS

SyNAPSE program of the Defense Advanced Projects Research Agency (HRL Laboratories LLC, subcontract #801881-BS under DARPA prime contract HR0011-09-C-0001); CELEST, a National Science Foundation Science of Learning Center (SBE-0354378)

Noninvasive monitoring of tissue hemoglobin using UV-VIS diffuse reflectance spectroscopy: a pilot study.

We conducted a pilot study on 10 patients undergoing general surgery to test the feasibility of diffuse reflectance spectroscopy in the visible wavelength range as a noninvasive monitoring tool for blood loss during surgery. Ratios of raw diffuse reflectance at wavelength pairs were tested as a first-pass for estimating hemoglobin concentration. Ratios can be calculated easily and rapidly with limited post-processing, and so this can be considered a near real-time monitoring device. We found the best hemoglobin correlations were when ratios at isosbestic points of oxy- and deoxyhemoglobin were used, specifically 529/500 nm. Baseline subtraction improved correlations, specifically at 520/509 nm. These results demonstrate proof-of-concept for the ability of this noninvasive device to monitor hemoglobin concentration changes due to surgical blood loss. The 529/500 nm ratio also appears to account for variations in probe pressure, as determined from measurements on two volunteers.

Rapid ratiometric determination of hemoglobin concentration using UV-VIS diffuse reflectance at isosbestic wavelengths.

We developed a ratiometric method capable of estimating total hemoglobin concentration from optically measured diffuse reflectance spectra. The three isosbestic wavelength ratio pairs that best correlated to total hemoglobin concentration independent of saturation and scattering were 545/390, 452/390, and 529/390 nm. These wavelength pairs were selected using forward Monte Carlo simulations which were used to extract hemoglobin concentration from experimental phantom measurements. Linear regression coefficients from the simulated data were directly applied to the phantom data, by calibrating for instrument throughput using a single phantom. Phantoms with variable scattering and hemoglobin saturation were tested with two different instruments, and the average percent errors between the expected and ratiometrically-extracted hemoglobin concentration were as low as 6.3%. A correlation of r = 0.88 between hemoglobin concentration extracted using the 529/390 nm isosbestic ratio and a scalable inverse Monte Carlo model was achieved for in vivo dysplastic cervical measurements (hemoglobin concentrations have been shown to be diagnostic for the detection of cervical pre-cancer by our group). These results indicate that use of such a simple ratiometric method has the potential to be used in clinical applications where tissue hemoglobin concentrations need to be rapidly quantified in vivo.

UV, visible and near-IR spectroscopy of atmospheric species

info:eu-repo/semantics/published