Search results for "Infrared"

Synthesis of Uvarovite Garnet

1989

A garnet with interesting optical properties is synthesized by means of the ceramic method and the formation of gels. Colloidal silica or tetraethoxysilane (TEOS) is used as a starting reagent in the latter method of synthesis, together with nitrate and chloride salts of the remaining components. Use is made of ultraviolet-visible and infrared spectroscopy techniques and X-ray diffraction in studying the evolution of the system. Formation of the garnet phase at lower temperatures is observed when using the gel methods, as well as the absence of chromates during the process in the samples which contained chlorides.

Fourier transform infrared analysis of paint solvents

1991

Abstract The composition of solvent mixtures employed in the paint industry was determined by Fourier transform infrared spectrometry. A procedure based on the use of the ratio between the absorbance of characteristic bands of each component permits the ratio between two solvents in a binary mixture to be determined, independently of the thickness of the sample film. Typical mixtures of xylol with butan-1-ol and with butyl acetate (xylol=mixture of o-, m- and p-xylenes) were used as model systems to develop the proposed procedure and the accuracy was determined using synthetic formulations. Another possible application of the procedure is the characterization of azeotropic mixtures.

Preparation and structural studies on dibutyltin(IV) complexes with pyridine mono- and dicarboxylic acids

2004

Abstract A number of organotin(IV) complexes with pyridine mono- and dicarboxylic acids (containing ligating –COOH group(s) and aromatic {N} atoms) were prepared in the solid state. The bonding sites of the ligands were determined by means of FT-IR spectroscopic measurements. It was found that in most cases the –COO− groups form bridges between two central {Sn} atoms, thereby leading to polymeric (oligomeric) complexes. On this basis, the experimental 119Sn Mossbauer spectroscopic data were treated with partial quadrupole splitting approximations. The calculations predicted the existence of complexes with octahedral (oh) and trigonal-bipyramidal (tbp) structures, but the formation of comple…

ChemInform Abstract: Vibrational Spectroscopy of a Tetraureidocalix[4]arene Based Molecular Capsule.

2010

Investigation of water transfer across thin layer biopolymer films by infrared spectroscopy

2011

International audience; The investigation of the apparent diffusivity of water in thin layer iota-carrageenan-based films by FTIR-ATR spectroscopy clearly evidences the fundamental role of surface properties on water transfer. Water diffusivity in iota-carrageenan based biopolymer films ranges from 0.3 to 1.3 × 10−10 m2 s−1 and is thus 10–100 times lower than that in highly hydrated carrageenan gels. The surface heterogeneity and composition when fat is added strongly influence the diffusivity by modifying the liquid water absorption at the inner surface.This study of diffusing molecules in liquid state is particularly interesting to mimic situations where direct liquid water contact occurs…

Structure and luminescence of GaN layers

2001

Abstract GaN films grown on 〈1 1 1〉 Si substrate by means of low pressure MOCVD technique in a horizontal flow quartz reactor are characterized by different thin layer analysis methods. The polycrystalline hexagonal structure of the GaN layers has been checked by means of grazing incidence X-ray diffractometry and IR spectroscopy. Cathodoluminescence (CL) spectra and their time kinetics are studied. The mean decay time of the 3.44 eV UV bound exciton transition is below 1 ns, whereas the 3.26 eV violet band shows a slow hyperbolical decay over about 1 μs. A third yellow band appears at 2.12 eV due to transitions via localized states.

Adsorbed CO on group 10 metal fragments: A DFT study

2009

DFT calculations on the helicopter and cartwheel rotations of one CO molecule adsorbed at the bridge site on metal-surface fragments, characterized by two (M(8)) or three (M(14)) metal-atom layers (M = Ni, Pd, Pt) were performed by the B3LYP[LANL2DZ+6-31 g(d,p)] method, to rationalize the adsorption energetics and the steric hindrance characteristics of surface CO molecules. Potential Energy Surfaces were obtained, either fixing the C-O bond-length or allowing it to change. The behavior of the three metals, as obtained from the study of the configurational space characterizing the CO adsorption on the fragments was explained on the basis of the interaction energies involved in the different…

Photocatalytic degradation of 4-Nitrophenol by g-C3N4-MCy: Mechanism study and kinetic modeling

2021

Abstract A graphitic carbon nitride (g-C3N4-MCy) photocatalyst was prepared by thermal condensation of melamine and cyanuric acid with equal proportions. The photocatalyst was characterized by Fourier transform infrared spectroscopy (FTIR), Specific surface area (SSA), X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Transmission electron microscope (TEM), and DRS–UV–Vis spectroscopic methods. We studied the photo-degradation kinetics of 4-nitrophenol using a g-C3N4-MCy. Four parameters were applied including initial concentration of 4-nitrophenol, amount of catalyst, dissolved oxygen content, and photon flux. The reaction rate constant was shown to be correlate…

Porous materials as delivery and protective agents for Vitamin A

2016

The suitability of porous materials to immobilize and release under control bioactive molecules prompted us to design and study delivery systems of Vitamin A (VitA). This molecule, relevant in several physiological functions, is easily oxidized. Commercial VitA was immobilized in two different clays, montmorillonite K-10 (MMT) and sepiolite (SEP), and in MCM-41, by impregnation. Characterization of the resulting hybrid materials by XRD, FTIR and 13C and 29Si (MAS) NMR spectroscopies revealed its presence. The photo-stability tests showed decreased degradation of VitA in the clays, compared to MCM-41 and the pure VitA, while thermostability is observed until ∼100 °C. The kinetics of the rele…

The equilibrium structure of trans-glyoxal from experimental rotational constants and calculated vibration–rotation interaction constants

2003

A total of six high-resolution FT-IR spectra for trans-glyoxal-d2, trans-glyoxal-d1 and trans-glyoxal-13C2 were recorded with a resolution ranging from 0.003 to 0.004 cm−1. By means of a simultaneous ground state combination difference analysis for each of these isotopologues using the Watson Hamiltonian in A-reduction and Ir-representation the ground state rotational constants are obtained. An empirical equilibrium structure is determined for trans-glyoxal using these experimental ground state rotational constants and vibration–rotation interaction constants calculated at the CCSD(T)/cc-pVTZ level of theory. The least-squares fit yields the following structural parameters for trans-glyoxal…