Cuneiform tablets tell the life and culture of Sumerian people in a sort of black and white tale ... more Cuneiform tablets tell the life and culture of Sumerian people in a sort of black and white tale because of the binary engraving technique. A leading question arises: did Mesopotamian people apply some kind of colour to decorate their tablets or to put emphasis on selected words? Some administrative and literary Sumerian cuneiform tablets of mid-third Millennium B.C. from the site of Kish (central Mesopotamia, modern Iraq) were dug up in twentieth-century and stored at the Ashmolean Museum of the Oxford University. Non-destructive micro-Raman spectroscopy is a powerful technique to detect the presence of residual pigments eventually applied to the engraving signs. Yellow, orange, red and white pigments have been detected and a possible identification has been proposed in this work.
... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czoch... more ... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czochralski method. ... the line broadening of the ZPL in the temperature range between 10 and 150 K. The FWHM was estimated by means of a deconvolution process with Voigt profiles23 ...
In this work we reveal the structure of a NaYO 2 compound solved from the X-ray diffraction powde... more In this work we reveal the structure of a NaYO 2 compound solved from the X-ray diffraction powder pattern using the " ab-initio " structure solution approach. The compound turned out to be of trigonal structure, S. G. R-3m isomorphous with α-NaFeO 2 layered compound. The lattice parameters are a = 3.404 and c = 16.602 Å, respectively, the atoms being located in Wickoff sites (cba) for O, Na and Y, respectively, leading to a calculated density of 4.31 g/cm 3. The ordering of sodium and yttrium atoms into alternate (111) planes of the cubic close-packed oxygen lattice of NaYO 2 is very regular. The octahedra are slightly distorted, the positive deviation of the O z parameter from 0.25 elongates the NaO 6 octahedra while compressing the YO 6 octahedra. Actually the Na-O and Y-O bond distances are 2.58 (1) and 2.25 (1) Å, respectively, as it is expected from their ionic radii values reported (1.16 vs 1.04 radii for both ion-species octahedral coordination). Finally, the Na-Y, Y-Y, and Na-Na next neighbor distances are close to 3.40 Å.
ABSTRACT The emission properties of mesoporous silica in the visible and ultraviolet range are af... more ABSTRACT The emission properties of mesoporous silica in the visible and ultraviolet range are affected by the reaction of the surface centers with different nonpolar and protic/aprotic polar solvents, that is, oxidized water, acetone, chloroform, and methanol. The samples were analyzed under wet conditions and after annealing above 60 °C, showing that the quantum efficiency of the emission is strongly reduced by the presence of residual solvent engulfed within the pores of the samples. The relative weight of the two main emission bands recorded at about 320 and 400 nm depends on the solvent, the contribution of the UV band being larger in the case of methanol treatment. The recorded changes in the emission spectrum are compared with the ones detected in samples with different pore diameters treated with oxidized water and annealed at 90 °C. The reported data are interpreted within the scenario of the emitting surface centers, and their models are discussed in view of the effects of the reaction with different solvents and the porosity of the samples: the reaction to oxygen pressure of methanol-treated samples is discussed in terms of adsorption and desorption from the emitting centers.
In this work we reveal the structure of a NaYO2 compound solved from the X-ray diffraction powder... more In this work we reveal the structure of a NaYO2 compound solved from the X-ray diffraction powder pattern using the “ab-initio” structure solution approach. The compound turned out to be of trigonal structure, S. G. R-3m isomorphous with α-NaFeO2 layered compound. The lattice parameters are a = 3.404 and c = 16.602 Å, respectively, the atoms being located in Wickoff sites (cba) for O, Na and Y, respectively, leading to a calculated density of 4.31 g/cm3. The ordering of sodium and yttrium atoms into alternate (111) planes of the cubic close-packed oxygen lattice of NaYO2 is very regular. The octahedra are slightly distorted, the positive deviation of the Oz parameter from 0.25 elongates the NaO6 octahedra while compressing the YO6 octahedra. Actually the Na-O and Y-O bond distances are 2.58 (1) and 2.25 (1) Å, respectively, as it is expected from their ionic radii values reported (1.16 vs 1.04 radii for both ion-species octahedral coordination). Finally, the Na-Y, Y-Y, and Na-Na nex...
ABSTRACT The light induced structural phase transition of TiO2 nanoparticles from anatase to ruti... more ABSTRACT The light induced structural phase transition of TiO2 nanoparticles from anatase to rutile structure is reported with different distribution of defect related surface states. Pristine, defective, and surface passivated samples were irradiated in vacuum condition by intragap visible wavelength to achieve the phase transformation. The surface states were studied by means of intragap excited steady state and time-resolved photoluminescence spectroscopy. Two bands were clearly observed, the first component centered at about 470 nm with time decay in the ns range and the second one peaked at 600 nm, with a lifetime in the order of µs. The bands are assigned to 5Ti3+ species and to 6Ti3+-OH species located at the surface of the anatase TiO2 nanoparticles. The transition mechanism to the rutile phase is interpreted in the framework of oxygen adsorption and desorption phenomena with the involvement of the surface defects.
ABSTRACT Silver thiogallate (AgGaS2) is a ternary semiconductor which crystallizes in the chalcop... more ABSTRACT Silver thiogallate (AgGaS2) is a ternary semiconductor which crystallizes in the chalcopyrite structure. Silver thiogallate has been widely used in different applications for its interesting physical properties: wide transparency range (from 0.5 to 12μm), high non-linear optical coefficient combined with good mechanical properties.The direct band gap in this compound is of about 2.7eV and emissions due to free and bound excitons had been observed. Photoluminescence spectrum is also characterized by a wide emission band centred at 496nm (2.50eV) due to donor–acceptor pairs recombination (DAP).We performed photoluminescence (PL) measurements exciting with the third harmonic (3.5eV) of a Nd:YAG laser from room temperature down to 10K at different excitation power.In this work, we report the dependence of the photoluminescence features of AgGaS2 on the excitation power at various temperatures: ionization energy of defects are estimated on the basis DAP theoretical model and of thermal quenching of the photoluminescence; evidences of non-radiative processes competitive to DAP is also presented.
The study of cultural heritage can take advantage of modern non-destructive analysis technique ab... more The study of cultural heritage can take advantage of modern non-destructive analysis technique able to identify, among the others, the composition of the investigated ancient artifacts. In the present paper we applied Raman spectroscopy to analyze selected Mesopotamian materials from Kish kept in the Ashmolean Museum of the University of Oxford to investigate the pottery technique of that ancient people, with particular reference to the painting procedure. Beside the use of hematite and gypsum as red and white pigment respectively, the use of a near infrared laser excitation allowed to detect the presence of specific compounds applied at the pottery surface. Residual traces of the used oil were detected thanks to the fingerprint vibration at 1870 cm- 1 which is ascribed to the C=C stretching of the cyclopropenoid compound of some fatty acids and, in particular, assignable to the use of oils derived by sterculiaceae and malvaceae plants. By using DFT calculations we simulated the degradation process of the hypothesized initial oil and we propose the attribution of the final compound revealed by Raman analysis. From the reported experimental results we propose that the oil was applied all over the surface of the pottery as a primer before the painting decoration with the use of the dry oil technique.
... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czoch... more ... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czochralski method. ... the line broadening of the ZPL in the temperature range between 10 and 150 K. The FWHM was estimated by means of a deconvolution process with Voigt profiles23 ...
Cuneiform tablets tell the life and culture of Sumerian people in a sort of black and white tale ... more Cuneiform tablets tell the life and culture of Sumerian people in a sort of black and white tale because of the binary engraving technique. A leading question arises: did Mesopotamian people apply some kind of colour to decorate their tablets or to put emphasis on selected words? Some administrative and literary Sumerian cuneiform tablets of mid-third Millennium B.C. from the site of Kish (central Mesopotamia, modern Iraq) were dug up in twentieth-century and stored at the Ashmolean Museum of the Oxford University. Non-destructive micro-Raman spectroscopy is a powerful technique to detect the presence of residual pigments eventually applied to the engraving signs. Yellow, orange, red and white pigments have been detected and a possible identification has been proposed in this work.
... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czoch... more ... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czochralski method. ... the line broadening of the ZPL in the temperature range between 10 and 150 K. The FWHM was estimated by means of a deconvolution process with Voigt profiles23 ...
In this work we reveal the structure of a NaYO 2 compound solved from the X-ray diffraction powde... more In this work we reveal the structure of a NaYO 2 compound solved from the X-ray diffraction powder pattern using the " ab-initio " structure solution approach. The compound turned out to be of trigonal structure, S. G. R-3m isomorphous with α-NaFeO 2 layered compound. The lattice parameters are a = 3.404 and c = 16.602 Å, respectively, the atoms being located in Wickoff sites (cba) for O, Na and Y, respectively, leading to a calculated density of 4.31 g/cm 3. The ordering of sodium and yttrium atoms into alternate (111) planes of the cubic close-packed oxygen lattice of NaYO 2 is very regular. The octahedra are slightly distorted, the positive deviation of the O z parameter from 0.25 elongates the NaO 6 octahedra while compressing the YO 6 octahedra. Actually the Na-O and Y-O bond distances are 2.58 (1) and 2.25 (1) Å, respectively, as it is expected from their ionic radii values reported (1.16 vs 1.04 radii for both ion-species octahedral coordination). Finally, the Na-Y, Y-Y, and Na-Na next neighbor distances are close to 3.40 Å.
ABSTRACT The emission properties of mesoporous silica in the visible and ultraviolet range are af... more ABSTRACT The emission properties of mesoporous silica in the visible and ultraviolet range are affected by the reaction of the surface centers with different nonpolar and protic/aprotic polar solvents, that is, oxidized water, acetone, chloroform, and methanol. The samples were analyzed under wet conditions and after annealing above 60 °C, showing that the quantum efficiency of the emission is strongly reduced by the presence of residual solvent engulfed within the pores of the samples. The relative weight of the two main emission bands recorded at about 320 and 400 nm depends on the solvent, the contribution of the UV band being larger in the case of methanol treatment. The recorded changes in the emission spectrum are compared with the ones detected in samples with different pore diameters treated with oxidized water and annealed at 90 °C. The reported data are interpreted within the scenario of the emitting surface centers, and their models are discussed in view of the effects of the reaction with different solvents and the porosity of the samples: the reaction to oxygen pressure of methanol-treated samples is discussed in terms of adsorption and desorption from the emitting centers.
In this work we reveal the structure of a NaYO2 compound solved from the X-ray diffraction powder... more In this work we reveal the structure of a NaYO2 compound solved from the X-ray diffraction powder pattern using the “ab-initio” structure solution approach. The compound turned out to be of trigonal structure, S. G. R-3m isomorphous with α-NaFeO2 layered compound. The lattice parameters are a = 3.404 and c = 16.602 Å, respectively, the atoms being located in Wickoff sites (cba) for O, Na and Y, respectively, leading to a calculated density of 4.31 g/cm3. The ordering of sodium and yttrium atoms into alternate (111) planes of the cubic close-packed oxygen lattice of NaYO2 is very regular. The octahedra are slightly distorted, the positive deviation of the Oz parameter from 0.25 elongates the NaO6 octahedra while compressing the YO6 octahedra. Actually the Na-O and Y-O bond distances are 2.58 (1) and 2.25 (1) Å, respectively, as it is expected from their ionic radii values reported (1.16 vs 1.04 radii for both ion-species octahedral coordination). Finally, the Na-Y, Y-Y, and Na-Na nex...
ABSTRACT The light induced structural phase transition of TiO2 nanoparticles from anatase to ruti... more ABSTRACT The light induced structural phase transition of TiO2 nanoparticles from anatase to rutile structure is reported with different distribution of defect related surface states. Pristine, defective, and surface passivated samples were irradiated in vacuum condition by intragap visible wavelength to achieve the phase transformation. The surface states were studied by means of intragap excited steady state and time-resolved photoluminescence spectroscopy. Two bands were clearly observed, the first component centered at about 470 nm with time decay in the ns range and the second one peaked at 600 nm, with a lifetime in the order of µs. The bands are assigned to 5Ti3+ species and to 6Ti3+-OH species located at the surface of the anatase TiO2 nanoparticles. The transition mechanism to the rutile phase is interpreted in the framework of oxygen adsorption and desorption phenomena with the involvement of the surface defects.
ABSTRACT Silver thiogallate (AgGaS2) is a ternary semiconductor which crystallizes in the chalcop... more ABSTRACT Silver thiogallate (AgGaS2) is a ternary semiconductor which crystallizes in the chalcopyrite structure. Silver thiogallate has been widely used in different applications for its interesting physical properties: wide transparency range (from 0.5 to 12μm), high non-linear optical coefficient combined with good mechanical properties.The direct band gap in this compound is of about 2.7eV and emissions due to free and bound excitons had been observed. Photoluminescence spectrum is also characterized by a wide emission band centred at 496nm (2.50eV) due to donor–acceptor pairs recombination (DAP).We performed photoluminescence (PL) measurements exciting with the third harmonic (3.5eV) of a Nd:YAG laser from room temperature down to 10K at different excitation power.In this work, we report the dependence of the photoluminescence features of AgGaS2 on the excitation power at various temperatures: ionization energy of defects are estimated on the basis DAP theoretical model and of thermal quenching of the photoluminescence; evidences of non-radiative processes competitive to DAP is also presented.
The study of cultural heritage can take advantage of modern non-destructive analysis technique ab... more The study of cultural heritage can take advantage of modern non-destructive analysis technique able to identify, among the others, the composition of the investigated ancient artifacts. In the present paper we applied Raman spectroscopy to analyze selected Mesopotamian materials from Kish kept in the Ashmolean Museum of the University of Oxford to investigate the pottery technique of that ancient people, with particular reference to the painting procedure. Beside the use of hematite and gypsum as red and white pigment respectively, the use of a near infrared laser excitation allowed to detect the presence of specific compounds applied at the pottery surface. Residual traces of the used oil were detected thanks to the fingerprint vibration at 1870 cm- 1 which is ascribed to the C=C stretching of the cyclopropenoid compound of some fatty acids and, in particular, assignable to the use of oils derived by sterculiaceae and malvaceae plants. By using DFT calculations we simulated the degradation process of the hypothesized initial oil and we propose the attribution of the final compound revealed by Raman analysis. From the reported experimental results we propose that the oil was applied all over the surface of the pottery as a primer before the painting decoration with the use of the dry oil technique.
... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czoch... more ... Yttrium aluminum garnet samples were grown by Scien-tific Materials Europe Italy by the Czochralski method. ... the line broadening of the ZPL in the temperature range between 10 and 150 K. The FWHM was estimated by means of a deconvolution process with Voigt profiles23 ...
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