Analysis and structural characterization of pigments and materials used in Nicolae Grigorescu heritage paintings.

The combination of various mobile, non-invasive techniques (IR reflectography technique, optical microscopy, XRF, Raman and NIR spectroscopies) and lab-based devices (FTIR and XPS spectroscopies, SEM-EDX microscopy) lead to the first exhaustive investigation of pigments and materials used by the famous Romanian painter Nicolae Grigorescu in three cultural heritage paintings. The study of a large number of spots and samples allowed a rigorous analysis and a far-reaching insight into his work.

Mild and selective oxidation of cellulose fibers in the presence of N-hydroxyphthalimide.

The oxidation reaction of regenerated cellulose fibers mediated by N-hydroxyphthalimide (NHPI) and various cocatalysts at room temperature for different time intervals and various amounts of low concentration sodium hypochlorite solution has been investigated to produce oxidized cellulose (OC), a biocompatible and bioresorbable polymer. The results revealed that the nonpersistent phthalimide-N-oxyl (PINO) radical generated in situ from NHPI in both, metallic or metal-free systems, is a powerful agent in this kind of transformation. Moreover, the reaction converts highly selectively C(6) primary hydroxyl groups to carboxylic groups under mild reaction conditions and shorter reaction times than previously reported. The amounts of negatively charged groups in OC were determined by means of potentiometric titration. Further characterization of the products were accomplished by using Fourier transform infrared spectroscopy/attenuated total internal reflection spectroscopy (FT-IR/ATR), environmental scanning electron microscopy (ESEM), and X-ray and energy-dispersive X-ray (EDX) spectroscopy. Notably, water retention values of the oxidized fibers increased by 30% in comparison with the original nonoxidized sample, as a result of the introduction of hydrophilic carboxylate groups.

Porphyrin-like compounds genesis under simulated abiotic conditions.

Experiments with gas mixtures intended to simulate the primaeval atmosphere of the Earth yielded many biologically important chemicals. Investigations into the synthesis of porphyrin-like compounds from methane, ammonia and water vapour were carried out by using high frequency discharges. Microanalyses of porphyrins showed that porphyrin-like pigments were formed in this way. The presence of divalent cations in the reaction system increased the yield of porphyrin-like pigments also involving the direct synthesis of their metal complexes. The ready formation of these compounds in abiotic conditions is significant, suggesting the possibility of their appearance during the early stage of chemical evolution.

[Preliminary results on the abiotic synthesis of metalloporphyrins]. / Résultats préliminaires sur la synthèse abiotique des métalloporphyrines.

The possibility of obtaining metalloporphyrins in abiotic conditions was investigated. The direct formation of zinc-porphyrins in the reaction product obtained by exposing a mixture of methane, ammonia and water vapor to electrical discharges is reported.