First chemical evidence of royal purple as a material used for funeral treatment discovered in a Gallo�CRoman burial (Naintr��, France, third century AD)

Violet-purple residues collected from a Gallo-Roman burial dated back to the second half of the third century A.D. and excavated at Naintré (France) were chemically investigated by multi-analytical methodology involving the use of Raman spectroscopy, direct exposure-mass spectrometry (DE-MS) and high-performance liquid chromatography (HPLC-UV-visible). Little is known about funeral treatment and rituals during Roman times. Retrieving valuable information on these by chemical analysis of organic residues was thus a key aspect of this work. Analyses demonstrated the presence of the very precious purple colorant obtained from shellfish glands commonly known as Tyrian or royal purple and its exceptional preservation. Chemical investigation and archaeological evidence have shown that purple was widely spread after the deposition of the body for burial. These results are the earliest chemical evidence of purple colorant used during funeral rituals (not as textile dye) and enabled us to highlight new aspects of funeral practices in Roman times.     

Vibrational spectroscopy of oh-defects in sol-gel Ce 3+ and Gd 3+ -doped silicate glasses

Vibrational modes of OH, as stretching, bending, combination, and overtones, were monitored by means of FTIR spectroscopy in Ce 3+ - and Gd 3+ -doped silicate glasses, prepared by means of the sol-gel technique, submitted to different thermal treatments, and aimed to applications as scintillators. The dopant concentration was varied in a wide range (10 m 3 -8% m.f.) and co-doped samples were also investigated. In this framework, the effects of OH and of rare-earth (RE) clustering, i.e. two possible non-radiative decay channels, on the IR spectra in the 500-14 v 000 v cm m 1 were examined. OH was detected as belonging either to water and to silanol in samples densified at 450 and 750 v C, while in those treated at 1050 v C only Si-OH groups were present in a concentration of the order of 1% m.f., nearly regardless of the RE amount. An absorption peaking at 4250 v cm m 1 was identified as related to an OH combination mode (bending+stretching) perturbed by a Gd cluster on the basis of its amplitude dependence on the Gd concentration and rapid thermal treatment.     

Dual path mechanism in the thermal reduction of graphene oxide

Graphene is easily produced by thermally reducing graphene oxide. However, defect formation in the C network during deoxygenation compromises the charge carrier mobility in the reduced material. Understanding the mechanisms of the thermal reactions is essential for defining alternative routes able to limit the density of defects generated by carbon evolution. Here, we identify a dual path mechanism in the thermal reduction of graphene oxide driven by the oxygen coverage: at low surface density, the O atoms adsorbed as epoxy groups evolve as O(2) leaving the C network unmodified. At higher coverage, the formation of other O-containing species opens competing reaction channels, which consume the C backbone. We combined spectroscopic tools and ab initio calculations to probe the species residing on the surface and those released in the gas phase during heating and to identify reaction pathways and rate-limiting steps. Our results illuminate the current puzzling scenario of the low temperature gasification of graphene oxide.     

NO adsorption on the Rh(110) surface: kinetics and composition of the adlayer studied by fast XPS

The adsorption and dissociation of NO on the Rh(110) surface were studied by synchrotron radiation X-ray photoemission spectroscopy at temperatures in the range 210–370 K. The O 1s or N 1s spectra were collected every 14 s while the surface was continuously exposed to a steady NO gas pressure. The difference in the binding energies for the atomic oxygen (O 1s ≤530.2 eV), atomic nitrogen (N 1s 397.2 eV) and molecular upright bonded NO molecules (O 1s ≥531.0 eV and N 1s 400 eV) allowed us to distinguish these surface species and to follow the evolution of the adsorbate layer. In addition to these dominating surface species a new species, characterized by O 1s binding energy of 530.7 eV and N 1s binding energy similar to that of the atomic nitrogen, was detected within a narrow coverage range. This state is tentatively assigned to a “lying down” NO bonding configuration, detectable at the timescale of the measurements. The uptake plots, constructed using the integrated intensity of the deconvoluted O 1s and N 1s spectra, are used to elucidate the effect of the reaction temperature and surface coverage and composition on the kinetics of dissociative and molecular NO adsorption of Rh(110).     

Analysis of cannabinoids in fiber hemp plant varieties (Cannabis sativa L.) by high-performance liquid chromatography

Summary An analytical procedure was developed for the detection of neutral and acidic cannabinoids in herbal cannabis without the need of any preliminary derivatization. The method was used to assay cannabinoid content of over one hundred fiber hemp samples grown in different Italian localities and harvested at different maturation level degrees during the summer. No interferences were observed due to the vegetal matrix. The influence of genetic factors and environmental conditions on cannabinoid content is discussed; the results may be of interest to enhance potential of fiber hemp in compliance with law enforcement purposes. Part of this work was presented at the 7^th Meeting on Recent Developments in Pharmaceutical Analysis, September 16–20, 1997, Island of Elba, Italy.     

2,3a,5,6,7,7a-Hexahydro-3h,4h-benzothiophene-3,4-dione and cyclopenta [b]-tetrahydrothiophene-3,4-dione enolate anions as synthetic equivalents to cyclohex-2-enone and cyclopent-2-enone c-2-carbanions.

An efficient procedure for α-alkylation of cyclohex-2-enone and cyclopent-2-enone involving a base-promoted tandem of retrograde Dieckmann-Michael reactions of the C-alkylated derivatives of the title heterocycles is presented.     

Monitoring super- and subsurface oxygen on Ag(210) by high energy resolution X-ray photoelectron spectroscopy: subsurface diffusion and segregation

We report on a high energy resolution X-ray photoelectron spectroscopy plus supersonic molecular beam investigation of O/Ag(210). Two components are detected in the O1s spectra upon O2 adsorption, at binding energies EB=527.7 and 529.6 eV. The former peak persists up to 470 K, while the latter one decreases abruptly above 280 K. Comparison with a previous vibrational spectroscopy investigation on the same system (L. Vattuone, et al. Phys. Rev. Lett. 2003, 90, 228302) allows to assign both features to atomic oxygen. The low-energy peak is identified with adatoms, while the other is correlated to O atoms in subsurface sites. A minor contribution at the same binding energy, due to carbonates, is quantified by inspection of the C1s region and shows a different temperature behavior with respect to oxygen. Oxygen segregation into the subsurface region is observed when heating the crystal in the presence of supersurface oxygen.     

Gd-incorporation and luminescence properties in sol-gel silica glasses

A thorough study was performed on Gd-doped sol-gel silica glasses, in the concentration range 0-8 mol% Gd. The analyses were carried out as a function of Gd content, before and after a post-densification thermal treatment. Different results concerning optical, vibrational, magnetic, and structural features were gathered in correlated experiments. The presence of Gd-rich nanoclusters was revealed. The size of nanoclusters increases by increasing the dopant concentration and by performing a rapid thermal treatment (RTT) at 1800 °C in air, which causes also a remarkable intensity increase of the ⁶P_7/2 → ⁸S_7/2 radioluminescence transition of Gd³⁺. Nanoclusters are amorphous, possibly close to a Gd₂SiO₅ stoichiometry as suggested by fast Fourier transform infrared spectroscopy (FTIR). FTIR studies revealed also the presence of Gd-dimers interacting with OH⁻ groups. Moreover, the presence of isolated Gd³⁺ ions was detected by electron paramagnetic resonance investigations. Based on the results obtained with different techniques, the Gd-incorporation in silica glass host and the resulting optical properties are discussed.     

Regarding enumeration of molecular isomers

In this paper, a simple theoretical approach to counting of substitution isomers is described. It is based on Polya's theorem and on point groups as recently described by us [Baraldi, I.; Fiori, C.; Vanossi, D. J. Math. Chem. 1999, 25, 23-30] and extended in this paper. Several applications are developed that range from molecules without symmetry to molecules with icosahedral symmetry (Ih). The problem of the appearance of stereoisomers is also analyzed.