Search results for "Spectroscopy"

1H, 13C and 17O NMR spectral study of chlorinated 3,4-dihydroxybenzaldehydes (protocatechualdehydes)

1995

Abstract Chlorinated 3,4-dihydroxybenzaldehydes have been studied by means of 1 H, 13 C and 17 O NMR spectroscopy. The 1 H and 13 C NMR spectral assignments are based on 2-dimensional 13 C- 1 H chemical shift correlation spectroscopy (COSY). The 17 O NMR measurements at natural isotope content in organic solvents are problematic owing to the poor solubility of the compounds and/or broadness of the resonance lines. In aqueous alkaline solutions, however, all protocatechualdehydes exhibit “easy-to-detect” 17 O NMR spectral characteristics. The 17 O NMR chemical shifts in the range of 140–480 p.p.m. are interpreted as arising from the different canonical structures of formyl substituted phenol…

13C and15N NMR study of substituted 1,2,4-triazines

1995

13C and 15N NMR spectra of eight substituted 1,2,4-triazines were measured and assigned. The assignments of the 13C NMR spectra were based on the substituent chemical shifts and nJ(C,H) coupling constants. 15N NMR chemical shifts generally showing well separated ranges were assigned by the proton coupled 15N NMR spectra. 15N NMR chemical shifts of N-4 in 3- and 5-methoxy or -thiomethyl-substituted 1,2,4-triazines were found to be related significantly (confidence level >99%) with the π-charge at N-4 calculated by a semi-empirical molecular orbital (AM1) procedure. For the 15N NMR chemical shifts of N-1 and N-2, no reliable correlations with the molecular electronic properties such as AM1 π-…

?-Phenylsulfonyl-N-arylacetamides (?-phenylsulfonylacetanilides):1H,13C and15N NMR spectral characterization

2000

3-Diazopyrroles—IV. Structure determination using 13C NMR spectroscopy

1990

Abstract On the basis of the 13 C NMR chemical shifts, it is proposed that, although b is the major canonical structure, structure c , in which a negative charge resides at C-3, provides an important contribution to the resonance stabilization of the 3-diazopyrroles, 1–4 .

Nuclear Magnetic Resonance and Electron Spin Resonance Spectroscopy

2001

The article contains sections titled: 1. Introduction 2. Principles of Magnetic Resonance 2.1. Nuclear and Electronic Properties 2.2. Nuclei and Electrons in a Stationary Magnetic Field 2.3. Basic Principles of the NMR and ESR Experiments 2.4. Relaxation 3. High-Resolution Solution NMR Spectroscopy 3.1. The NMR Experiment 3.1.1. Continuous Wave Methodology 3.1.2. Fourier Transform Methodology 3.2. Spectral Parameters 3.2.1. Chemical Shift 3.2.2. Spin - Spin Coupling 3.2.3. Signal Intensity 3.2.4. Relaxation Times 3.3. NMR and Structure 3.3.1. Hydrogen (1H and 2H) 3.3.2. Carbon (13C) 3.3.3. Fluorine (19F) 3.3.4. Phosphorus (31P) 3.3.5. Nitrogen (14N and 15N) 3.3.6. Oxygen (17O) 3.3.7. Silico…

Klimt artwork: red-pigment material investigation by backscattering Fe-57 Mössbauer spectroscopy, SEM and p-XRF

2017

Material tests were performed on a rediscovered Klimt-artwork "Trompetender Putto". We performed studies on the red colored spots, mainly taken from non-restored parts. MIMOS II Fe-57 Mossbauer spectroscopy (novelty in art-pigment analysis) mainly reveals haematite and crystallized goethite in red colors. Electron microscopy can identify various layers of the original and overpainting of an artwork. The number of layers fluctuates between three and four chemically painted areas. The portable X-ray fluorescence analysis enables to reduce the pigment list to containing mercury (cinnabar), lead, zinc, iron and titanium. Infrared-light-irradiation visualizes the different age of the pigments.

High spatial resolution analysis of the iron oxidation state in silicate glasses using the electron probe

2018

The iron oxidation state in silicate melts is important for understanding their physical properties, although it is most often used to estimate the oxygen fugacity of magmatic systems. Often high spatial resolution analyses are required, yet the available techniques, such as μrXANES and μMössbauer, require synchrotron access. The flank method is an electron probe technique with the potential to measure Fe oxidation state at high spatial resolution but requires careful method development to reduce errors related to sample damage, especially for hydrous glasses. The intensity ratios derived from measurements on the flanks of FeLα and FeLβ X-rays (FeLβf/FeLαf) over a time interval (time-depend…

Combined proton NMR wideline and NMR relaxometry to study SOM-water interactions of cation-treated soils

2013

Abstract Focusing on the idea that multivalent cations affect SOM matrix and surface, we treated peat and soil samples by solutions of NaCl, CaCl2 or AlCl3. Water binding was characterized with low field 1H-NMR-relaxometry (20 MHz) and 1H wideline NMR spectroscopy (400 MHz) and compared to contact angles. From 1H wideline, we distinguished mobile water and water involved in water molecule bridges (WaMB). Large part of cation bridges (CaB) between SOM functional groups are associated with WaMB. Unexpectedly, 1H NMRrelaxometry relaxation rates suggest that cross-linking in the Al-containing peat is not stronger than that by Ca. The relation between percentage of mobile water and WaMB water in…

Multifunctional two-photon active silica-coated Au@MnO Janus particles for selective dual functionalization and imaging.

2014

Monodisperse multifunctional and nontoxic Au@MnO Janus particles with different sizes and morphologies were prepared by a seed-mediated nucleation and growth technique with precise control over domain sizes, surface functionalization, and dye labeling. The metal oxide domain could be coated selectively with a thin silica layer, leaving the metal domain untouched. In particular, size and morphology of the individual (metal and metal oxide) domains could be controlled by adjustment of the synthetic parameters. The SiO2 coating of the oxide domain allows biomolecule conjugation (e.g., antibodies, proteins) in a single step for converting the photoluminescent and superparamagnetic Janus nanopar…

Fast nosological imaging using canonical correlation analysis of brain data obtained by two-dimensional turbo spectroscopic imaging.

2007

A new fast and accurate tissue typing technique has recently been successfully applied to prostate MR spectroscopic imaging (MRSI) data. This technique is based on canonical correlation analysis (CCA), a statistical method able to simultaneously exploit the spectral and spatial information characterizing the MRSI data. Here, the performance of CCA is further investigated by using brain data obtained by two-dimensional turbo spectroscopic imaging (2DTSI) from patients affected by glioblastoma. The purpose of this study is to investigate the applicability of CCA when typing tissues of heterogeneous tumors. The performance of CCA is also compared with that of ordinary correlation analysis on s…