Analysis of green copper pigments in illuminated manuscripts by micro-Raman spectroscopy

In the majority of the literature describing green coloured materials used on ancient painting layers (15th or 16th century), two copper greens are mainly cited: malachite [CuCOr3 x Cu(OH)2] and verdigris [Cu(CH3COO)2 x [Cu(OH)2]3 x 2H2O]. It is shown, by micro-Raman spectroscopy, that the artists were actually employing more than these two copper greens, in particular various copper sulfates, among which the most common pigment found is posnjakite [CuSO4 x 3Cu(OH)2 x H2O]. In contrast to the PIXE (particle induced X-ray emission) technique, Raman spectroscopy is a technique of choice, able to distinguish not only a copper sulfate from a carbonate or acetate but also the different sulfates themselves; in this respect, we found that the high wavenumber region (2800-4000 cm(-1)), characteristic of H2O vibrations, is of particular interest. It is also shown that numerous green areas were created with mixtures of a copper sulfate mixed with other pigments, for instance to enhance the colour depth. Finally, in some cases, no green pigment is actually employed but the colour is obtained by intimately mixing yellow and blue pigments. All these results led to a new look at the pigments which were in use on the palettes of the ancient artists.     

Byzantine wall paintings from Kastoria, northern Greece: spectroscopic study of pigments and efflorescing salts

This study concerns the investigation of pigments and efflorescence phenomena on the wall paintings of Kastoria, a rural, non-metropolitan Byzantine town. A large number of representative samples were collected from the murals of three churches, dated to post-Byzantine era (14th-17th c. AD). The identified pigments for the red colour were hematite (Fe2O3), cinnabar (HgS) and minium (Pb3O4), while brown and yellow colours were attributed to mixtures of ochres (Fe-oxides and hydroxides) and lime. The utilization of admixtures of iron, lead and mercury compounds was also attested in order to render specific tones on the painted surfaces. Black and dark blue hues were prepared using black carbon and Mn in some cases. Grey colours were assigned to a mixture of black carbon and lime. Green colour is rather attributed to admixtures of Fe-rich minerals and lime and not to the commonly used green earths. Baryte (BaSO4) was also evidenced as a filler or extender. Phosphorous was detected and connected to proteinaceous material and Mo and Sb were traced which are probably affiliated to Fe-oxides. Regarding efflorescing salts, the determined compounds are: calcite, dolomite, gypsum, halite, nitratine, natron and mirabilite, all of which are related to temperature and humidity changes and moisture fluctuations inside the wall paintings.     

Investigation of roman age pigments found on pottery fragments

This work deals with the study of the physico-chemical characteristics of pigments found on pottery fragments from an excavation in Vicenza (Contrà Pedemuro S. Biagio). The examined pigments were: a blue colour on a terracotta fragment; an olive green on a black pot bottom; yellow traces on a red depurated terracotta; an olive green plate bottom with an amaranth “a fresco” test; a deep red on a depurated terracotta; a white trace, again on a depurated terracotta. The techniques used were optical microscopy, scanning electron microscopy (SEM), equipped with an energy dispresive (EDS) microanalysis detector, X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Most of those techniques were non-destructive and able to provide the required results. All the pigments belonged to the group of basic colours, we did not find “precious” pigments. They have many similarities to those discovered in other European sites in France and Switzerland, witnessing the active trading exchange in which X^a Regio, Venetia et Histria played an important role.     

Raman fibre optic approach to artwork dating

Raman micro-probe spectroscopy has been applied to the analysis of a non catalogued hand-crafted wallpaper during its restoration process. The analysis has been totally non-destructive without the necessity of taking any sample. The artwork showed a great chromatic palette having been detected the presence of calcium carbonate, Prussian blue, ultramarine blue, gypsum (CaSO4.2H2O), minium (Pb3O4), vermilion (HgS), chrome orange (CaCO3), chrome yellow (PbCrO4), barium sulphate and carbon black (C). From the spectroscopic analysis the date of its manufacturing has been set between 1828 and 1830, introduction of chrome yellow and orange, as well as artificial ultramarine blue, and 1840, when continuous industrial wallpapers were extensively manufactured in Europe.     

In situ investigations of vault paintings in the Antwerp cathedral

X-ray fluorescence spectroscopy (XRF) and Raman spectroscopy have been used to examine 15th century mediaeval and 16th century renaissance vault paintings in the Our Lady's Cathedral (Antwerp, Belgium) in view of their restoration. The use of mobile instruments made it possible to work totally non-destructively. This complementary approach yields information on the elemental (XRF) and on the molecular composition (Raman) of the pigments. For the 15th century vault painting the pigments lead–tin yellow (Pb₂SnO₄), lead white (2PbCO₃·Pb(OH)₂), vermilion (HgS), massicot (PbO) and azurite (2CuCO₃·Cu(OH)₂) could be identified. The pigments used for the 16th century vault painting could be identified as red lead (Pb₃O₄), hematite (Fe₂O₃), lead white (2PbCO₃·Pb(OH)₂) and azurite (2CuCO₃·Cu(OH)₂). For both paintings the presence of the strong Raman scatterer calcite (CaCO₃) resulted in a difficult identification of the pigments by Raman spectroscopy. The presence of gypsum (CaSO₄·2H₂O) on the mediaeval vault painting probably indicates that degradation took place.     

Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products

The Raman spectra of plattnerite [lead(IV) oxide, PbO2] and of the lead pigments red lead (Pb3O4), lead monoxide [PbO, litharge (tetragonal) and massicot (orthorhombic)], lead white [basic lead carbonate, 2PbCO3.Pb(OH)2] and of their laser-induced degradation products were recorded using a range of different excitation lines, spectrometer systems and experimental conditions. The degradation of PbO2 is more extensive along the pathway PbO2-->Pb3O4-->PbO (litharge)-->PbO (massicot) the shorter the wavelength of the excitation line and the higher its power. The Raman spectrum of PbO2, which is black and of the rutile structure, is particularly difficult to obtain but three bands, at 653, 515 and 424 cm-1, were identified as arising from the b2g, a1g and e(g) modes respectively, by analogy with the corresponding modes of isostructural SnO2 (776, 634 and 475 cm-1). A further oxide was identified, PbO1.55, the Raman spectrum of which does not correspond to that of any of the laser-induced degradation products of PbO2 at any of the wavelengths used. The Raman results are critical to the future use of Raman microscopy for the identification of lead pigments on artworks.     

Structural study of ternary iron-lead-germanate glass ceramics

Glass ceramics with the composition xFe(2)O(3)·(100-x)[7GeO(2)·3PbO(2)] where 0≤x≤60 mol% were obtained and studied using XRD, FTIR and UV-vis spectroscopy investigations. Heat treatment of glass samples at 400°C for 8 h led to the formation of α, γ-PbGe(4)O(9), Pb(3)Fe(2)Ge(4)O(14) and PbO(1.44) crystalline phases. The content of these crystalline phases depends of Fe(2)O(3) concentration. FTIR spectroscopy data suggest that the lead ions have a pronounced affinity towards [GeO(5)] structural units containing non-bridging oxygens and [FeO(4)] anions producing formation of the Pb(3)Fe(2)Ge(4)O(14) crystalline phase. The introduction of low concentrations of Fe(2)O(3) into the host matrix results in the formation of new absorption UV bands between 320 and 450 nm. These bands arise from to the d-d transitions of the Fe(+3) ions. The light absorption in the range from 250 to 600 nm increases with increasing iron oxide content in matrix network, accompanied with the changes on color from white to brown yellow and darker brown.     

Analysis of pigments from Roman wall paintings found in Vicenza

The analysis of about 60 samples of wall paintings was carried out using different chemicophysical techniques: optical microscopy, scanning electron microscopy (SEM) equipped with an EDS microanalysis detector, X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The identified pigments were cinnabar, hematite, red ochre, celadonite, cuprorivaite (Egyptian blue), yellow ochre, goethite and carbon. Only in one case some lead white was found instead. In general, the mortar preparation did not correspond to the complex structure suggested by Vitruvius (De Architectura), but it generally showed a porous layer, with crushed grains under the pigment layer. In certain cases two superposed pigment layers were found: yellow superimposed on both red and pink, black on pink, green on black.     

钛基二氧化铅电极电沉积制备过程中的立体生长机理

采用恒电位的方法在涂有SnO2＋Sb2O5中间层的Ti基体上电沉积制备了不同颗粒尺度的Ti/PbO2电极, 利用XPS, XRD和SEM等方法对Ti/PbO2电极电沉积制备过程中电极的结构、表面形貌等物理化学性能进行了研究. 结果表明, Ti/PbO2电极涂层中Pb元素在138.2～138.4 eV之间有明显的Pb4f7/2峰, 表明电极表面上主要得到的是PbO, XRD和XPS分析结果证明电极涂层体相生成的是PbO2. 基于Ti/PbO2涂层的形成是不同晶面生长过程的事实, 提出Ti/PbO2电极的立体生长机理.     

阳极电沉积条件对Ti/SnO2-Sb2O5/PbO2+Nano-Co3O4复合电极组成、形貌和结构的影响

本文在涂有中间层SnO2-Sb2O5的Ti基体上,采用阳极复合电沉积法制备了Ti/SnO2-Sb2O5/PbO2+Nano-Co3O4复合电极材料,借助于X射线衍射（XRD）、X射线光电子能谱（XPS）、扫描电镜（SEM）等分析方法研究了制备条件对该复合电极材料的组成、结构和形貌的影响。结果表明,纳米Co3O4的掺杂可提高PbO2电极表面的粗糙度和空隙率;沉积电位、镀液中Co3O4粒子浓度及有机溶剂的添加均对镀层中Co3O4的嵌入量有很大影响。     

Growth Mechanism and Characterization of Single-crystalline Ga-doped SnO2 Nanowires and Self-organized SnO2/Ga2O3 Heterogeneous Microcomb Structures

Single-crystalline Ga-doped SnO2 nanowires and SnO2:Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). FE-SEM images showed that the products consisted of nanowires and microcombs that represent a novel morphology. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnO2. The influence of experimental conditions on the morphologies of the products is discussed. The morphology of the product showed a ribbon-like stem and nanoribbon array aligned evenly along one or both side of the nanoribbon. It was found that many Ga2O3 nanoparticles deposited on the surface of the microcombs. The major core nanoribbon grew mainly along the 110 direction and the self-organized branching nanoribbons grew epitaxially along 1110 or 1110 orientation from the (110) plane of the stem. A growth process was proposed for interpreting the growth of these remarkable SnO2:Ga2O3 heterogeneous microcombs. Due to the heavy doping of Ga, the emission peak in photoluminescence spectra has red-shifted as well as broadened significantly.     

Identification of the EPR signal of S₂⁻ in green ultramarine pigments

Green and blue ultramarine pigments are characterized by the sodalite structure Na(6)(Al(6)Si(6)O(24)) and colored inserted species. These chromophores are sulfur species: S(3)(-) (blue) and S(2)(-) (yellow). Both radicals are encapsulated inside the β-cages. They contribute to the EPR spectrum of ultramarine pigments. The well-known strong EPR signal observed in all ultramarine pigments Continuous-Wave (CW) spectra has long been assigned to S(3)(-) (g = 2.029). In contrast, the S(2)(-) contribution is still subject to controversy because its signal in ultramarine pigments was not resolved even at low temperature in CW-EPR experiments. In this study, we identify unambiguously for the first time by CW-EPR and field sweep-echo detected (FS-ED) EPR the signal of S(2)(-) in ultramarine pigments and we determine its tensor components: g(1) = 2.69(6), g(2) = 2.03(4) and g(3) = 1.86(4).     

Raman microscopy of Greek icons: identification of unusual pigments

Five Greek icons, made between the 15th and 18th centuries and now belonging to the Victoria and Albert Museum collections, were analysed by energy-dispersive X-ray fluorescence (EDXRF), optical microscopy and Raman microscopy in order to determine the stratigraphy of the artworks and the identity of the pigments used. Together with common pigments, such as red lake, vermilion, red lead, red iron oxide, orpiment, yellow ochre, lead white, chalk, gypsum, anhydrite, Prussian blue, indigo and a copper-containing green, a few unusual materials were identified, specifically pararealgar (a yellow arsenic sulphide, As4S4), its precursor the chi-phase, and lead tin yellow type II (PbSn(1-x)SixO3). Attention is drawn to the complementarity of the techniques used for the pigment identifications.     

掺杂TiO2纳米粉的合成、表征及催化性能研究

 考察了制备方法对掺杂Fe2O3,ZrO2或SnO2的TiO2纳米粉的XRD谱及催化性能的影响．结果表明,用共沉淀法制备的Fe2O3·TiO2对其XRD谱强度的影响较大,而负载法制备Fe2O3／TiO2对其XRD谱的强度无影响;两种方法制备的掺杂ZrO2或SnO2的TiO2样品对XRD谱均无影响．TEM结果表明,TiO2纳米粉的晶粒均匀,粒径为14～18nm．苯酚水溶液的光催化氧化分解反应结果表明,与TiO2样品相比,负载型Fe2O3／TiO2的催化活性明显较高,但ZrO2／TiO2,SnO2／TiO2和共沉淀型Fe2O3·TiO2的催化活性变化不大．可以认为,对掺杂Fe2O3的TiO2催化剂,负载法是较好的制备方法．     

CO oxidation on nanostructured SnO(x)/Pt(111) surfaces: unique properties of reduced SnO(x)

We have investigated surface CO oxidation on "inverse catalysts" composed of SnO(x) nanostructures supported on Pt(111) using X-ray photoelectron spectroscopy (XPS), low-energy ion scattering spectroscopy (LEISS) and temperature-programmed desorption (TPD). Nanostructures of SnO(x) were prepared by depositing Sn on Pt(111) pre-covered by NO(2) layers at low temperatures. XPS data show that the SnO(x) nanoparticles are highly reduced with Sn(II)O being the dominant oxide species, but the relative concentration of Sn(II) in the SnO(x) nanoparticles decreases with increasing Sn coverage. We find that the most active SnO(x)/Pt(111) surface for CO oxidation has smallest SnO(x) coverage. Increasing the surface coverage of SnO(x) reduces CO oxidation activity and eventually suppresses it altogether. The study suggests that reduced Sn(II)O, rather than Sn(IV)O(2), is responsible for surface CO oxidation. The occurrence of a non-CO oxidation reaction path involving reduced Sn(II)O species at higher SnO(x) coverages accounts for the decreased CO oxidation activity. From these results, we conclude that the efficacy of CO oxidation is strongly dependent on the availability of reduced tin oxide sites at the Pt-SnO(x) interface, as well as unique chemical properties of the SnO(x) nanoparticles.     

A solution-phase, precursor route to polycrystalline SnO2 nanowires that can be used for gas sensing under ambient conditions

This paper describes a solution-based, precursor method for the facile synthesis of uniform nanowires containing rutile SnO2 nanocrystallites. In a typical procedure, nanowires of approximately 50 nm in diameters and up to 30 mum in length were obtained as a white precipitate by refluxing SnC2O4.2H2O and poly(vinylpyrrolidone) in ethylene glycol. Structural analyses by XRD, FT-IR, and TGA indicate that these highly anisotropic nanostructures were formed in an isotropic medium through the aggregation of chainlike precursors that were, in turn, formed via polyol-mediated oligomerization. These nanowires could be further converted to polycrystalline SnO2 by calcination in air at 500 degrees C. The resultant nanowires of SnO2 were highly porous and could be used for gas sensing with improved sensitivity and reversibility under ambient conditions. We have also demonstrated that this new approach could be extended to generate polycrystalline nanowires of other metal oxides such as In2O3 and anatase TiO2.     

Argentinean prehistoric pigments’ study by combined SEM/EDX and molecular spectroscopy

Composition of the prehistoric pigments’ (from Carriqueo rock shelter, Rio Negro province, Argentina) has been analysed by means of molecular spectroscopy (Fourier transform infrared (FTIR) and micro-Raman) and scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDS). Red and yellow pigments were recognized as red and yellow ochre. The matrix of the pigments is composed of one or more substances. According to the matrix composition yellow and red pigments were also divided into two groups—i.e. those containing kaolinite or sulphates. Green pigment was detected as green earth, made up of celadonite as a chromophore.     

纳米SnO_2@TiO_2的制备及其光催化性能

SnCl4和 Ti(OBu)4为原料,采用活性层包覆法制备了 SnO2@TiO2包覆型复合光催化剂,并用 XPS、 IR、 XRD、 TEM和 BET等手段进行了表征,以二甲基二氯乙烯基磷酸酯（简称 DDVP）稀释液为模拟废水,考察了 SnO2@TiO2的光催化活性及降解液初始浓度对反应动力学的影响 .结果表明：包覆粒子由锐钛矿型 TiO2和金红石型 SnO2组成;与纯 SnO2、 TiO2相比, SnO2@TiO2包覆粒子的光催化活性明显提高, DDVP稀释液被光催化降解属于零级反应,但反应表观速率常数与降解液初始浓度成正比 .