Search results for "Spectroscopy"
showing 10 items of 10293 documents
1H and13C NMR assignments and conformational analysis of some podocarpene derivatives
2000
This paper reports on the assignment of the 1 Ha nd 13 C NMR spectra of five podocarpene derivatives. Resonance assignments were made on the basis of one- and two-dimensional NMR techniques which included 1 H, 13 C, DEPT and HMQC and also 1D NOE difference spectroscopy. The ratio of the different conformers in the six- membered C-ring of the podocarpene system was determined by molecular mechanics calculations and analysis of proton spin-spin coupling constants. Copyright © 2000 John Wiley & Sons, Ltd.
Bidentate pyridyl‐NHC ligands: synthesis, ground and excited state properties of their iron(II) complexes and role of the fac/mer isomerism
2021
International audience; Iron complexes are promising candidates for the development of sustainable molecular photoactive materials as an alternative to those based on precious metals such as Ir, Pt or Ru. These compounds possess metal-ligand charge transfer (MLCT) transitions potentially of high interest for energy conversion or photocatalysis applications if the ultrafast deactivation via lower-lying metal-centred (MC) states can be impeded. Following an introduction describing the main design strategies used so far to increase the MLCT lifetimes, we review some of our latest contributions to the field regarding bidentate Fe(II) complexes comprising N-heterocyclic carbene ligands. The disc…
The partition sum of methane at high temperature
2008
11 pages, 4 Tables, 3 Figures Computer code on line at http://icb.u-bourgogne.fr/JSP/TIPS.jsp; International audience; The total internal partition function of methane is revisited to provide reliable values at high temperature. A multi-resolution approach is used to perform a direct summation over all the rovibrational energy levels up to the dissociation limit. A computer code is executable on line at the URL : http://icb.u-bourgogne.fr/JSP/TIPS.jsp to allow the calculation of the partition sum of methane at temperatures up to 3000 K. It also provides detailed information on the density of states in the relevant spectral ranges. The recommended values include uncertainty estimates. It is …
Acoustic spectral hole-burning in a two-level system ensemble
2020
AbstractMicroscopic two-level system (TLS) defects at dielectric surfaces and interfaces are among the dominant sources of loss in superconducting quantum circuits, and their properties have been extensively probed using superconducting resonators and qubits. We report on spectroscopy of TLSs coupling to the strain field in a surface acoustic wave (SAW) resonator. The narrow free spectral range of the resonator allows for two-tone spectroscopy where a strong pump is applied at one resonance, while a weak signal is used to probe a different mode. We map the spectral hole burnt by the pump tone as a function of frequency and extract parameters of the TLS ensemble. Our results suggest that det…
Continuous-flow tristimulus colorimetry: a new approach for gradient scanning techniques
1991
Abstract A flow-injection gradient scanning technique for colour evaluation by means of tristimulus colorimetry is described. Equipment and data acquisition requirements are discussed. The program CHROMA.FIA data the treatment and comparative chromatic analysis is presented. The chemical and flow conditions were optimized. Comparative studies using metallochromic indicators with both the flow-injection and the conventional batch procedures were made. The continuous-flow procedure provides good results and is more than fifteen times faster than the manual titrimetric procedure.
Challenges in the determination of engineered nanomaterials in foods
2016
Detection, characterization, and quantification of engineering nanomaterials (ENMs) in foods is still a pending issue that needs to be tackle to protect consumers and to fix some related aspects (e.g. labelling or control). The global challenge for the analytical sciences is that ENMs are a new sort of analytes, involving both chemical (composition, mass and number concentration) and physical information (e.g. size, shape, aggregation). In this critical review, we evaluate and compare the procedures involved in the analytical methods and studies developed thus far for the identification and quantification of ENMs in food. We discuss advantages and limitation as well as prospects. We pointed…
Nanomaterial-based molecularly imprinted polymers for pesticides detection: Recent trends and future prospects
2020
Abstract Pesticides have been widely used in agricultural and industrial production to prevent pests. So, sensing pesticides with high selectivity and sensitivity level plays a significant role in food safety management. Molecularly imprinted polymer (MIP) based sensors overcome the current restriction of traditional detection approaches and offer great potential for efficient, low-cost and low detection limit using smart miniaturized equipment. But some drawbacks could come from the lack of electrocatalytic activity and conductivity of MIPs that restrict their utilization in the sensing field. The integration of NPs with MIPs has opened new ways for rapid screening and monitoring of pestic…
Sorting of Single Biomolecules based on Fourier Polar Representation of Surface Enhanced Raman Spectra
2016
AbstractSurface enhanced Raman scattering (SERS) spectroscopy becomes increasingly used in biosensors for its capacity to detect and identify single molecules. In practice, a large number of SERS spectra are acquired and reliable ranking methods are thus essential for analysing all these data. Supervised classification strategies, which are the most effective methods, are usually applied but they require pre-determined models or classes. In this work, we propose to sort SERS spectra in unknown groups with an alternative strategy called Fourier polar representation. This non-fitting method based on simple Fourier sine and cosine transforms produces a fast and graphical representation for sor…
The Determination of Absorptive Properties of Atmospheric Aerosol Particles Using Photoacoustic Spectroscopy
1982
Chopped light produces an acoustic signal in a closed cell when it is absorbed by a sample of material within this cell. This effect is used to develop a method for measuring the absorption coefficient of aerosol particles. The possibilities and limits of the method are discussed.
Portable low-cost open-source wireless spectrophotometer for fast and reliable measurements
2020
This article is based upon COST Action CA16215 and supported by the ERDF , European-Union Project No.1.1.1.2/16/I/001.