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1.
Perfluoropolyethers (PFPEs) are a class of high performance materials used in a wide range of applications (refrigeration, lubrication, semiconductor industry, etc.). PFPEs containing peroxidic units are intermediate materials for the preparation of commercial end products. In this work we study the spectroscopic properties of ether and peroxides linkages in this class of compounds; nuclear magnetic resonance (NMR) spectra are discussed, FT-Raman data presented. Quantum chemical calculations on model molecules were used as a tool for the interpretation of the Raman experimental data and physical-chemical properties. 相似文献
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Rodolfo G. Figueroa Mauro Valente Jaime Guarda Jorge Leiva Eduardo Quilaguilque Bryan Casanelli Fernando Leyton 《X射线光谱测定》2022,51(3):251-261
A novel and suitable energy-dispersive X-ray fluorescent (EDXRF) device, currently at the prototype stage, the Project OXIRIS (Orthovoltage X-Ray–Induced Radiation System), is presented for the simultaneous detection and treatment of cancer diseases. Monte Carlo simulation and experimental results of EDXRF signals from a small deep artificial tumor consisting of a solution of gold nanoparticles bio-targeted and immersed in a tissue-bioequivalent matrix are presented and compared. Briefly, the device consists of a dynamic orthovoltage X-ray fluence concentration coupled to confocal with an EDXRF system along with a sample holder for 3D scanning; all integrated and controlled by a dedicated software capable of controlling the whole operation functionalities: the X-ray source, the rotating arm, the sample holder, and the detection system. The software also includes dedicated subroutines for X-ray fluorescent spectra processing to correlate K-lines signal at each acquisition position with the corresponding high atomic number elements' concentration to produce a 3D distribution according to the user-defined grid. The confocal configuration ensures that the detected signal comes exclusively from the excited volume as defined by the bulk of the focal spot. Hence, the 3D image is achieved by scanning the sample holder through the movement of the sample-carrier stretcher moved by step motors in the 3 coordinated axes. The feasibility of the proposed methodology and the design of the prototype have been successfully demonstrated experimentally, targeting gold nanoparticles in water-equivalent phantoms. 相似文献
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A. ButtafavaP.A. Guarda G. MarchionniR. Ronconi A. Faucitano 《Journal of fluorine chemistry》2002,114(1):9-16
The rate constants and activation parameters for the self-coupling of perfluoroperoxy radicals of structure A and B: C7F15OO (A) and RFOCF2OO (B) have been determined in perfluorohexane solution in the temperature range 228-258 K. The magnitude of the rate constants obtained ranks between 6.6×108 and 2.5×109 l mol−1 s−1 and are therefore, among the largest rate values so far reported in the literature for primary peroxy radicals couplings. The activation energy is positive and lower for the peroxy radicals (A) with respect to the peroxy radicals (B) (10.5 and 23.0 kJ mol−1, respectively).Analysis by kinetic modeling has shown that the peroxy radicals decay curves are compatible with the participation of peroxy radicals↔tetroxide equilibria to the reaction mechanism.Upper limit values of kbs<10 and <20 s−1 were inferred for the β-scission reactions of the perfluoroalkylperoxy radicals at 228 and 258 K, respectively. 相似文献
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S. Radice G. Canil P. Toniolo P.A. Guarda S. Petricci A. Milani M. Tommasini C. Castiglioni G. Zerbi 《Macromolecular Symposia》2008,265(1):218-224
Summary: Functionalized perfluoropolyethers are investigated by infrared spectroscopy with the aim to give a quantitative estimate of the carboxylic acid groups species; since hydrogen bonded moieties have been observed, also the relative distribution of the associated species has been determined. The study is based both on measured and on theoretically predicted infrared intensities, as obtained by density functional theory (DFT) calculations on model systems. 相似文献
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Emerson A. Guarda Mara R.B. Marzari Clarissa P. Frizzo Patrícia M. Guarda Nilo Zanatta Helio G. Bonacorso Marcos A.P. Martins 《Tetrahedron letters》2012,53(2):170-172
Synthesis of 4-alkoxy-1,1-dichloro-3-alken-2-ones [CHCl2C(O)C(R2)C(R1)-OR, where R, R1, R2 = Et, H, H; Me, Me, H; Et, H, Me; Me, –(CH2)2–; Me, –(CH2)3–; Et, Et, H; Et, Bu, H; Et, i-Pr, H; Et, i-Bu, H; Me, Ph, H; Me, thien-2-yl, H] from acylation of enol ethers and acetals with dichloroacetyl chloride, in ionic liquid ([BMIM][BF4] or [BMIM][PF6]) is reported. The synthesis of alkenones [R3–C(O)C(R2)C(R1)-OR], where R/R1/R2/R3 = Et/H/H/Ph, t-Bu/H/H/Ph, Me/-(CH2)4/Ph, Me/-(CH2)4/Me] from the reaction of enol ethers with benzoyl chloride or acetyl chloride, in ionic liquid [BMIM][BF4], is also reported. Last products are described for the first time. 相似文献
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Robson Santana Lima Arnaud Victor dos Santos Fabiano Vargas Pereira Marluce Oliveira da Guarda Souza 《Journal of Thermal Analysis and Calorimetry》2010,100(1):83-87
The thermal decomposition process of La2O3/MgO (La/Mg = 2, 1 and 0.5) supported nickel (15% mass/mass Ni) precursor was investigated. Thermal analysis results show
distinct processes of decomposition of the samples in accordance with the composition. The mass loss at higher temperature
is associated to distinct stages of decomposition of lanthanum precursors. The thermal analysis results agree with the FTIR
spectra showing change in the band corresponding to carbonates and nitrates species. XRD results also confirmed the precursor’s
decomposition. It can be concluded that the thermal decomposition of La2O3–MgO-nickel precursor depends on the La/Mg ratio and of the residual species. 相似文献
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Marco Vincenti Francesca Fasano Maria Carmen Valsania Pierantonio Guarda Susan D. Richardson 《Analytical and bioanalytical chemistry》2010,397(1):43-54
A novel derivatizing agent, 5-chloro-2,2,3,3,4,4,5,5-octafluoropentyl chloroformate (ClOFPCF), was synthesized and tested
as a reagent for direct water derivatization of highly polar and hydrophilic analytes. Its analytical performance satisfactorily
compared to a perfluorinated chloroformate previously described, namely 2,2,3,3,4,4,5,5-octafluoropentyl chloroformate (OFPCF).
The chemical properties (reactivity, selectivity, derivatization products, and their chromatographic and spectral features)
for ClOFPCF were investigated using a set of 39 highly polar standard analytes, including, among others, hydroxylamine, malic
and succinic acids, resorcinol, hydroxybenzaldehyde, and dihydroxybenzoic acid. Upon derivatization, the analytes were extracted
from the aqueous solvent and analyzed by gas chromatography (GC)-mass spectrometry (MS) in the electron-capture negative ionization
(ECNI) mode. Positive chemical ionization (PCI)-MS was used for confirming the molecular ions, which were virtually absent
in the ECNI mass spectra. ClOFPCF showed good reaction efficiency, good chromatographic and spectroscopic properties (better
than with OFPCF), good linearity in calibration curves, and low detection limits (0.3–1 μg/L). A unique feature of the derivatizations
with ClOFPCF, and, in general, highly fluorinated chloroformates, is their effectiveness in reacting with carboxylic, hydroxylic,
and aminic groups at once, forming multiply-substituted non-polar derivatives that can be easily extracted from the aqueous
phase and determined by GC-ECNI-MS. The entire procedure from raw aqueous sample to ready-to-inject hexane solution of the
derivatives requires less than 10 min. Another benefit of this procedure is that it produced stable derivatives, with optimal
volatility for GC separation, and high electron affinity, which allows their detection as negative ions at trace level. In
addition, their mass spectra exhibits chlorine isotopic patterns that clearly indicate how many polar hydrogens of the analyte
undergo derivatization. Finally, derivatization with ClOFPCF was used successfully to identify 13 unknown highly polar disinfection
byproducts (DBPs) in ozonated fulvic and humic acid aqueous solutions and in real ozonated drinking water. 相似文献
10.
Alexandre B. Schneider Paulo C. Nascimento Denise Bohrer Leandro M. de Carvalho Ananda Guarda Daiane Dias Andrea Koschinsky 《Electroanalysis》2013,25(7):1628-1634
A voltammetric method was developed for zirconium determination as Zr(IV)‐cupferron‐oxalate‐diphenylguanidine complex based on adsorptive accumulation at the HMDE (Epeak=?0.95 V). The supporting electrolyte was a mixture of acetate/acetic acid (pH 4.6) and ammonium acetate (pH 5.7) solutions. Eads=?0.6 V (vs. Ag/AgCl), tads=400 s, 10 mV s?1 scan rate, and DP mode were the main parameters. The linear range was 0.033 to 3.3×10?9 mol L?1, and the LOD and LOQ (tads=400 s) were 0.77 and 1.6×10?11 mol L?1, respectively. The method was adequate for seawater samples, although not sufficiently sensitive for surface waters. 相似文献