Electron paramagnetic resonance samples

X-ray powder diffraction data of the zeolite samples were collected before and after the catalytic reactions with a Diano-XRD 8000 X-ray powder diffraction apparatus. Electron paramagnetic resonance samples were sealed off in quartz tubes on a vacuum line after various treatments and analyzed with a Varian E-3 spectrometer at room temperature. 

Other magnetic measurements of catalysts include electron paramagnetic resonance and magnetic susceptibility. Although those are not as common as NMR, they can be used to look at the properties of paramagnetic and ferromagnetic samples. Examples of these applications can be found in the literature [87. 

Electron paramagnetic resonance (EPR) spectroscopy is yet another diagnostic tool for the detection of isomorphous substitution of Ti. Its sensitivity is very high, and investigations can be performed with samples even with very low contents of paramagnetic species. The spectra and g parameters are sensitive to the local structure and associated molecular distortions. Hence, it is an ideal tool to characterize Ti in titanosilicates. Ti in the + 4 oxidation state in titanosilicates is diamagnetic and hence EPR-silent. Upon contacting with CO or H2 at elevated... 

Registration of ROS was carried out by electron paramagnetic resonance (EPR) technique using spin trap l-hydroxy-2,2,6,6-tetramethyl-piperidine-4-OH (2 x 10 3 M). EPR spectra in the samples were registered at room temperature in quartz cuvette with the volume of 200 pi (Burlaka et al., 1994). 

Electron paramagnetic resonance (EPR), also known as electron spin resonance (ESR), has rightly been called the NMR of unpaired electrons . A sample of a radical (generally in solution) is irradiated with a beam of microwave radiation and the proportion of the radiation that is absorbed is then determined. 

The electron paramagnetic resonance experiments on the yttrium ceramics, on the other hand, are ambiguous. In the study by Murrieta et al. [55], the EPR signal of YBa2Cu307 sample was interpreted as a superposition of two different lines attributed to the Cul and Cu2 sites. In some other studies of yttrium ceramics, the EPR signal was not detected or was attributed to an impurity phase [56]. Thus, Ilirther more refined EPR experiments are needed to confirm the location of the unpaired spin in the cluster. 

Analysis of antioxidant properties relative to the DPPH" radical involves observation of colour disappearance in the radical solution in the presence of the solution under analysis which contains antioxidants. A solution of extract under analysis is introduced to the environment containing the DPPH radical at a specific concentration. A methanol solution of the DPPH radical is purple, while a reaction with antioxidants turns its colour into yellow. Colorimetric comparison of the absorbance of the radical solution and a solution containing an analysed sample enables one to make calculations and to express activity as the percent of inhibition (IP) or the number of moles of a radical that can be neutralised by a specific amount of the analysed substance (mmol/g). In another approach, a range of assays are conducted with different concentrations of the analysed substance to determine its amount which inactivates half of the radical in the test solution (ECso). The duration of such a test depends on the reaction rate and observations are carried out until the absorbance of the test solution does not change [4]. If the solution contains substances whose absorbance disturbs the measurement, the concentration of DPPH radical is measured directly with the use of electron paramagnetic resonance (EPR) spectroscopy. 

The problem of bringing a large magnet into the field for ambient measurements has been overcome in electron paramagnetic resonance (EPR, also called electron spin resonance, ESR) by Mihelcic, Helten, and coworkers (93-99). They combined EPR with a matrix isolation technique to allow the sampling and radical quantification to occur in separate steps. The matrix isolation is also required in this case because EPR is not sensitive enough to measure peroxy radicals directly in the atmosphere. EPR spectroscopy has also been used in laboratory studies of peroxy radical reactions (100, 101). 

Spectroelectrochemical cells that permit redox titrations of precious biological samples, require exclusion of oxygen, and allow acquisition of data from multiple spectroscopic domains have been described. A recent example of these cell designs combines electron paramagnetic resonance spectroscopy with UV-visible absorption spectroscopy [71] for studies of flavoproteins. 

Kucherov and Slinkin reported solid-state reactions of H-mordenite and HZSM-5 zeolites with metallic oxides such as CuO (13), Cr2O-, Mo03, and V205 (14-17). The resulting samples were studied by EPR (electron paramagnetic resonance) spectrometry. The authors have shown that the metal cations migrate to cationic sites, where they are coordinately unsaturated. 

In this section we report the first study of the micro-SQUID response of a low-spin molecular system, V15, to electromagnetic radiation. The advantages of our micro-SQUID technique in respect to pulsed electron paramagnetic resonance (EPR) techniques consist in the possibility to perform time-resolved experiments (below 1 ns) [59] on submicrometer sizes samples (about 1000 spins) [22] at low temperature (below 100 mK). Our first results on Vi5 open the way for time-resolved observations of quantum superposition of spin-up and spin-down states in SMMs. Other results obtained in similar systems but with large spins concern for example EPR measurements [10], resonant photon-assisted tunneling in a Feg SMM [60]. 

It is a common practice to seal a sample in a closed glass tube for storage or for further study by means of EPR (electron paramagnetic resonance) or NMR (nuclear magnetic resonance). Although it is not difficult to tip off a sample, if done poorly, the NMR tube will spin very badly. If done badly, the sample may be destroyed along with hours, weeks, or months of work. 

Electron Paramagnetic Resonance (EPR) Spectrometer [43-4 6]. When a paramagnetic or ferromagnetic sample (solid or liquid) of molecules or ions with total spin S and magnetization M is placed in an external DC magnetic field H0, the frequency v (Hz, or cycles per second) for spin transitions A mg = 1 is... 

The X-ray powder diffraction data reveal that for the Fe(CO) and the Scherzer-Fort preparations that bulk a-Fe is present. Electron paramagnetic resonance experiments indicate in all cases that ferromagnetic iron is present in these reduced samples. The X-ray data also reveal that these samples are crystalline after each of these synthetic procedures and that crystallinity is not lost when these samples are photolyzed or thermally treated. 

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