Characterization of lapis lazuli pigments using a multitechnique analytical approach: implications for identification and geological provenancing.

Many of the Raman spectra obtained from areas painted with ultramarine pigments in illuminated manuscript leaves from the 14th century Italian manuscript the Laudario of Sant'Agnese, in the collection of the J. Paul Getty Museum, also contain strong bands not typically associated with this pigment. The source of these features was investigated using a multitechnique analytical approach. Techniques employed include Raman microspectroscopy, scanning electron microscopy with energy-dispersive spectroscopy, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry. The results indicate the presence of diopside (CaMgSi(2)O(6)), a mineral commonly associated with lapis lazuli in nature, and suggest that transition metal dopants in the diopside may be responsible for the Raman features, likely the result of fluorescence with vibronic coupling. The implication of this result with respect to using Raman spectroscopy as a fast, noninvasive, and nondestructive method for determining the geological provenance of natural lapis lazuli pigments used in art is discussed.

Photochemistry of the indoor air pollutant acetone on Degussa P25 TiO2 studied by chemical ionization mass spectrometry.

We have used chemical ionization mass spectrometry (CIMS) to study the adsorption and photochemistry of several oxygenated organic species adsorbed to Degussa P25 TiO2, an inexpensive catalyst that can be used to mineralize volatile organic compounds. The molecules examined in this work include the common indoor air pollutant acetone and several of its homologs and possible oxidation and condensation products that may be formed during the adsorption and/or photocatalytic degradation of acetone on titanium dioxide catalysts. We report nonreactive uptake coefficients for acetone, formic acid, acetic acid, mesityl oxide, and diacetone alcohol, and results from photochemical studies that quantify, on a per-molecule basis, the room-temperature photocatalytic conversion of the species under investigation to CO2 and related oxidation products. The data presented here imply that catalytic surfaces that enhance formate and acetate production from acetone precursors will facilitate the photocatalytic remediation of acetone in indoor environments, even at room temperature.

Interaction of the indoor air pollutant acetone with Degussa P25 TiO2 studied by chemical ionization mass spectrometry.

Preventing a build-up of indoor pollutant concentrations has emerged as a major goal in environmental chemistry. Here, we have applied chemical ionization mass spectrometry to study the interaction of acetone, a common indoor air pollutant, with Degussa P25 TiO2, an inexpensive catalyst that is widely used for the degradation of volatile organic compounds into CO2 and water. To better understand the adsorption of acetone onto Degussa P25, the necessary first step for its degradation, the experiments were carried out at room temperature in the absence of UV light. This allowed for the deconvolution of the nonreactive and reactive thermal binding processes on Degussa P25 at acetone partial pressures (10(-7)-10(-4) Torr) commonly found in indoor environments. On average, 30% of the adsorbed acetone is bound irreversibly, resulting in a surface coverage of irreversibly bound acetone of approximately 1 x 10(12) molecules/cm2 at 3-4 x 10(-5) Torr. Equilibrium and dynamic experiments yield a sticking coefficient of approximately 1 x 10(-4) that is independent of the acetone partial pressures examined here. Equilibrium binding constants and free energies of adsorption are reported.

Nonlinear optical studies of the agricultural antibiotic morantel interacting with silica/water interfaces.

It is now known that the untreated discharge of pharmaceuticals into the environment can impact human health and development and lead to increased drug resistance in biota. Here, we present the first direct interface-specific studies that address the mobility of the widely used agricultural antibiotic morantel, which is commonly present in farm runoff. Surface-bound morantel was spectroscopically identified using second harmonic generation (SHG) via a two-photon resonance of its n-pi* transition and in the C-H stretching region by vibrational sum frequency generation (VSFG). Resonantly enhanced SHG adsorption isotherm measurements carried out at the silica/water interface between 6 x 10(-7) and 5 x 10(-5) M morantel concentration result in a free energy of adsorption of 42(2) kJ/mol at pH 7. Finally, real-time tracking of morantel interaction with the silica/water interface shows that the binding events are fully reversible, consistent with its high mobility in silica-rich soil environments. This work thus indicates that pharmaceuticals discharged into the environment can enter the groundwater supply of municipal water systems, at which point their removal is challenging. In addition, the high mobility of morantel in silica-rich soil environments could lead to developing increased interaction of this antibiotic with target organisms, which could respond by increased drug resistance.