Micro-Raman analysis of coloured lithographs

Raman micro-spectroscopy was chosen for analysis and identification of the pigments present in four nineteenth-century hand-coloured lithographs, as this technique has several advantages over others for this purpose. The possibility of performing completely non-destructive analysis without any sampling is probably one of its most favourable qualities for art analysis. Raman spectroscopy can also be used to determine some pigments that cannot be detected using FTIR, such as vermilion, carbon blacks, cadmium pigments, etc. Among others, Prussian blue, ultramarine blue, carbon black, chrome yellow, yellow ochre, red lead, red iron oxide, burnt Sienna, indigo blue, chrome orange, phthalocyanine green, and some other organic pigments, were determined in the specimens. The results obtained have led to doubts about the age of the lithographs.     

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).     

Characterization of Japanese color sticks by energy dispersive X-ray fluorescence,X-ray diffraction and Fourier transform infrared analysis

This work comprises the use of energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) techniques for the study of the composition of twentieth century traditional Japanese color sticks. By using the combination of analytical techniques it was possible to obtain information on inorganic and organic pigments, binders and fillers present in the sticks. The colorant materials identified in the sticks were zinc and titanium white, chrome yellow, yellow and red ochre, vermillion, alizarin, indigo, Prussian and synthetic ultramarine blue. The results also showed that calcite and barite were used as inorganic mineral fillers while Arabic gum was the medium used. EDXRF offered great potential for such investigations since it allowed the identification of the elements present in the sample preserving its integrity. However, this information alone was not enough to clearly identify some of the materials in study and therefore it was necessary to use XRD and FTIR techniques.     

铅铬黄粒子的微胶囊化及其表面形貌的表征

研究了铅铬黄粒子的微胶囊化及其机理；探讨了对粒子表面形貌的量化表征方法．结果表明，在油包水（Ｗ／Ｏ）乳液中对铅铬黄粒子进行无机微胶囊化是一提高其耐酸、碱性的有效方法．颜料粒子的表面形貌可用其表面分形维数（Ｄ）量化表征．     

超高效液相色谱-串联质谱法同时测定玩具中的16种致癌和致敏染料

建立了同时测定玩具中16种致癌和致敏染料(酸性红26、碱性红9、分散蓝1、酸性紫49、分散蓝3、溶剂黄1、分散蓝106、分散橙3、分散黄3、碱性紫1、碱性紫3、分散红1、溶剂黄3、分散蓝124、溶剂黄2、分散橙37)的超高效液相色谱-串联质谱分析方法。纺织品、皮革、纸张、木材、气球、造型黏土、贴纸、可接触液体等不同类型的玩具材料经超声提取后,以Waters ACQUITY UPLC BEH C18色谱柱(50mm×2.1mm,1.7μm)分离后进行UPLC/MS/MS多反应监测模式下的定性及定量分析。16种致癌和致敏染料的方法检出限为1.0～8.0μg/kg;在5～100μg/kg范围内的低、中、高3个添加水平的平均回收率为81.3%～98.6%;日内精密度均小于11%,日间精密度均小于14%。本方法准确、快速、灵敏度高,可用于玩具的实际检验工作。     

Naked-eye detection of fluoride using Zr(IV)-EDTA complex and pyrocatechol violet.

A method for the visual detection of fluoride is presented using an aqueous solution of Pyrocatechol Violet (PV), which changes its color from yellow to blue by the formation of a ternary complex with Zr(H2O)2EDTA; also, the blue color of PV-Zr-EDTA readily shifts to orange red upon the addition of a moderate concentration of fluoride. The mechanism has been interpreted by a ligand-exchange reaction of PV coordinated to Zr(IV) with fluoride. The effect of various factors, such as the pH, ratio of Zr(H2O)2EDTA and PV, and diverse ions were studied to optimize the conditions for the reaction of PV-Zr-EDTA with fluoride. The present naked-eye detection system provides a simple, quick, and sensitive method for the determination of fluoride in the concentration range 1.5 x 10(-5) to 1.5 x 10(-4) mol dm(-3). The detection limit of the method was observed to be 4.5234 x 10(-4) mol dm(-3) with a correlation coefficient of 0.9955. The developed chemosensor was applied to the detection of fluoride in industrial effluents.     

Occupancy of the sodalite cages in the blue ultramarine pigments

A quantitative EPR study of blue ultramarine pigments has been performed in order to determine the concentration of the S(3)(-) chromophore. Copper sulfate CuSO(4) x 5H(2)O has been used as a standard, while a ruby crystal was used as an inner standard to take into account the changes of the quality factor of the cavity. These experiments show that, in the most-colored pigments, less than half of the sodalite cages are occupied by a S(3)(-) radical. In other experiments, it has been shown that the blue ultramarine pigments can be significantly modified by heating under a dynamic vacuum. The concentrations of S(3)(-) and S(2)(-), as deduced from EPR and Raman experiments, are increased after this type of treatment. These changes imply that sulfur species are transformed into S(3)(-) or S(2)(-) during this treatment. It is discussed that these sulfur species could be S(2)(-).     

Intensely luminescent gold(I)-silver(I) cluster complexes with tunable structural features

A new series of isostructural, brilliantly luminescent gold-silver complexes having the formula [Au3(mu3-E)Ag(PPh2py)3](BF4)2 where E = O, S, Se and Ph2Ppy = 2-diphenylphosphinopyridine has been synthesized and characterized. The structural core of these complexes is a Au3Ag metallophilically linked tetrahedron with a group-16 atom functioning as a mu3-ligand capping the three gold atoms. In the solid state, pairs of clusters are joined by two unsupported aurophilic interactions. The emission energy changes strikingly in going from O (blue) to S (yellow) and Se (orange). The luminescence from the E = O system is the first to be reported for a gold(I) oxo system. Additionally, the luminescent 4-methylpyridyl analogue with E = S has been prepared and structurally characterized. For E = S, Se, the change in emission energy with mu3-bridging atom provides a sound basis for an LMMCT assignment of the excited state while lifetime measurements support its spin-forbidden nature. Frozen glass measurements indicate the presence of a higher-energy emitting state for these systems, and for the E = O system, either LMMCT or metal-centered cluster-based emission can be proposed.     

A non-invasive XRF study supported by multivariate statistical analysis and reflectance FTIR to assess the composition of modern painting materials

The palette used in two paintings by Paul Cézanne, L'étang des soeurs dated c. 1875 and La route tournante, made in the last year of his life (1902), were analyzed using non-invasive spectroscopic methods. X-ray fluorescence combined with principal components analysis (PCA) and supported by reflectance near- and mid-FTIR was shown to be a powerful analytical tool to draw conclusions about the chemical identification of inorganic materials in paintings. Pigments and fillers such us Thénard's blue, Prussian blue, red ochre, kaolin, vermilion, lead white, zinc white and barium sulphate, were identified. Evidence for three different pigments, namely a copper arsenite pigment, chrome green (a mixture of chrome yellow and Prussian blue) and viridian has been obtained by the PCA analysis of elemental compositions of green hues.     

Raman analysis of ancient pigments on a tile from the Citadel of Algiers

A micro-Raman spectroscopy study of a multi-coloured (yellow, blue, white, redish-brown and brown-black) tile shard from the Citadel of Algiers was undertaken. XRD and EDX were used as complementary techniques. The study shows that the heterogeneous three-shade yellow pigment on the tile is composed largely of the ancient ternary (Pb-Sn-Sb) pyrochlore oxide with a dominant Pb-O vibration at 127 cm(-1) consistent with the Pb2SnSbO6.5 structure as verified by XRD. The literature assignment of this band at 132 cm(-1) probably comes from a mixture of pigments. The redish-brown and the brown-black pigments are found to be Naples yellow (Pb2Sb2O7) and lead(II) stannate (Pb2SnO4), respectively, while cobalt blue (CoAl2O4) gives the blue colour and cassiterite (SnO2) is the origin of the white colour. The bulk of the tile body is composed mainly of hematite (alpha-Fe2O3), maghemite (gamma-Fe2O3), magnetite (Fe3O4) and Quartz (alpha-SiO2) with traces of calcite (CaCO3) and amorphous carbon. Micro-Raman spectroscopy proved to be very useful in the characterization of pigments as well as the tile body. These results further establish Raman spectroscopy as a technique of choice for the analysis of pigments on archaeological artifacts. The results obtained here could be used in the restoration and preservation programme of the Citadel itself which stands today as a symbol of pre-colonial Algerian heritage.     

不同供氢底物用于测定H2O2的酶催化动力学研究

研究了牛血红蛋白(hemoglobin,Hb)作为过氧化物模拟酶,以酸性铬蓝K、罗丹明B、亚甲基蓝不同供氢底物测定H2O2的酶催化反应体系的催化特性和反应条件。探讨了采用不同底物测定时的催化反应机理。用于雨水中H2O2含量的测定,结果满意。     

The resonance Raman spectrum of ultramarine blue

The resonance Raman spectrum of ultramarine blue has been observed by the use of 457.9, 488.0, 514.5, 568.2 and 647.1 nm excitation. With 457.9 nm excitation three progressions are observed; comparison of the results with earlier data from sulphur-doped alkali halide crystals indicates that ultramarine blue contains the S₂^? as well as the S₃^? anion.     

Novel luminescent mixed-metal Pt-Tl-alkynyl-based complexes: the role of the alkynyl substituent in metallophilic and eta2(pi...Tl)-bonding interactions

A novel series of [PtTl(2)(C[triple chemical bond]CR)(4)](n) (n = 2, R = 4-CH(3)C(6)H(4) (Tol) 1, 1-naphthyl (Np) 2; n = infinity, R = 4-CF(3)C(6)H(4) (Tol(F)) 3) complexes has been synthesized by neutralization reactions between the previously reported [Pt(C[triple chemical bond]CR)(4)](2-) (R = Tol, Tol(F)) or novel (NBu(4))(2)[Pt(C[triple chemical bond]CNp)(4)] platinum precursors and Tl(I) (TlNO(3) or TlPF(6)). The crystal structures of [Pt(2)Tl(4)(C[triple chemical bond]CTol)(8)]4 acetone, 14 acetone, [Pt(2)Tl(4)(C[triple chemical bond]CNp)(8)]3 acetone1/3 H(2)O, 23 acetone 1/3 H(2)O and [[PtTl(2)(C[triple chemical bond]CTol(F))(4)](acetone)S](infinity) (S = acetone 3 a; dioxane 3 b) have been solved by X-ray diffraction studies. Interestingly, whereas in the tolyl (1) and naphthyl (2) derivatives, the thallium centers exhibit a bonding preference for the electron-rich alkyne entities to yield crystal lattices based on sandwich hexanuclear [Pt(2)Tl(4)(C[triple chemical bond]CR)(8)] clusters (with additional Tlacetone (1) or Tlnaphthyl (2) secondary interactions), in the C(6)H(4)CF(3) (Tol(F)) derivatives 3 a and 3 b the basic Pt(II) center forms two unsupported Pt-Tl bonds. As a consequence 3 a and 3 b form an extended columnar structure based on trimetallic slipped PtTl(2)(C[triple chemical bond]CTol(F))(4) units that are connected through secondary Tl(eta(2)-acetylenic) interactions. The luminescent properties of these complexes, which in solution (blue; CH(2)Cl(2) 1,2; acetone 3) are very different to those in solid state (orange), have been studied. Curiously, solid-state emission from 1 is dependent on the presence of acetone (green) and its crystallinity. On the other hand, while a powder sample of 3 is pale yellow and displays blue (457 nm) and orange (611 nm) emissions, the corresponding pellets (KBr, solid) of 3, or the fine powder obtained by grinding, are orange and only exhibit a very intense orange emission (590 nm).     

X-ray absorption spectroscopy of ultramarine pigments: A new analytical method for the polysulfide radical anion S3 chromophore

Blue and mauve ultramarine artists' pigments and their heat-treated products have been investigated by sulfur K-edge X-ray absorption. X-ray absorption near-edge structure spectra are dominated by features of reduced sulfur and sulfate species. There is also a pre-peak at about 2468.0 eV which reflects the presence of the unpaired electron on the polysulfide radical anion (S₃⁻). Pre-peak intensity is directly proportional to the depth of blue coloration, and provides a new, independent method for estimating the proportion of ultramarine cage sites occupied by the blue chromophore. The occupancy of the polysulfide radical anion S₃⁻ is estimated to be 33% in an intense ultramarine blue pigment, 22% in a dark blue ultramarine pigment, and 1% in deep royal blue lazurite from Afghanistan. The more efficient development of color in lazurite is attributed to extensive annealing of the mineral structure in the natural environment.     

Thermal analysis of the interaction of inorganic pigments with p(nBA/MMA) acrylic emulsion before and after UV ageing

Differential scanning calorimetry (DSC) and thermogravimetry (TG) analyses were used to investigate the influence of inorganic pigments on the photo-oxidative stability of an acrylic emulsion binding medium. For this purpose, three different types of inorganic pigments such as ultramarine blue, cadmium red and hydrated chromium oxide green were selected and mixed with an acrylic emulsion binding medium of poly(n-butyl acrylate/methyl methacrylate). These laboratory mixed paints were analysed before and after UV exposure for different periods of time. In addition, three acrylic commercial paints such as ultramarine blue, cadmium red and chromium oxide green from Liquitex^® and Rembrandt^® companies were also analysed. The results obtained with both thermal techniques suggested that ultramarine blue has the strongest influence on the photo-oxidative stability of the binding medium. A higher increase of the glass transition temperature T _g was observed by DSC analysis on the UV aged binder mixed with ultramarine blue. This result was confirmed by the TG investigations that showed a gradual decrease of the initial temperature of degradation as well as the strongest decrease of the final mass% of the organic compounds. Similar results were measured from the Liquitex^® and Rembrandt^® blue paints.     

Improvements in the wallpaper industry during the second half of the 19th century: micro-Raman spectroscopy analysis of pigmented wallpapers

Scientific studies of the pigments used in the manufacturing process of some pigmented wallpapers are presented in this work. Non-destructive micro-Raman spectroscopy was selected for this purpose, and provides important information about how the 19th century wallpaper industry incorporated new materials in their works and designs. At the same time, analysis can help to date the samples of uncatalogued wallpapers. Chrome yellow, burnt Sienna, Prussian blue, ultramarine blue, red lead, carbon black, calcium carbonate, red iron oxide and a red organic pigment were identified. According to the palette used, as well as to the manufacturing process, the wallpapers in this study can be dated to the second half of the 19th century.     

Analytical contributions to the evaluation of painting authenticity from Princely church of Curtea de Arges

The present study contains the analyses performed for pigment samples taken from the Princely church of Curtea de Arges, one of the oldest churches in Romania. The results of our investigations have shown the source of these samples, thus being identified the pigments: natural ultramarine, cinnabar, red earth, and calcium carbonate in the painting from the 14th century, the pigments: lead white, zinc white, and Prussian blue in the repainting from the 19th century and the pigments zinc white, titanium dioxide white, bone white, yellow ochre, red ochre, green earth, artificial ultramarine, and mars red in the interventions carried out in the 20th century. The analyses consisted of light microscopy (LM) and microchemical tests, as well as energy dispersive X-ray (EDX) analysis. This system of analyses allows one to precisely determine the authenticity of certain pigments, thus avoiding the dating errors for different interventions carried out on the original mural painting from the Saint Nicholas Princely church of Curtea de Arges.     

Specific interaction between polyethylenimine and azo dyes carrying hydroxyl groups

The binding of acid azo dyes having phenolic hydroxyl groups such as orange I ( I ), orange II ( II ), chrome violet ( III ), 4-hydroxyazobenzene-4′-sulfonate ( IV ), and 2,4-dihydroxyazobenzene-4′-sulfonate ( V ) by polyethylenimine was studied by equilibrium dialysis and spectroscopic methods. The results obtained indicate that dyes ( III ) and ( V ) with two OH groups are bound much more strongly than dyes ( I ), ( II ), and ( IV ) with one OH group. Also polyethylenimine is far superior to any other polymers which have been examined, including bovine serum albumin, polyvinylpyrrolidone, and poly-L -lysine, in its ability to form complexes with these dyes ( III ) and ( V ). The OH groups involved participate preferentially in complex formation with polyethylenimine. The unusual affinity of polyethylenimine for the dyes carrying OH groups is discussed.     

Near-crater discoloration of white lead in wall paintings during laser induced breakdown spectroscopy analysis

During Laser-Induced Breakdown Spectroscopy (LIBS) analysis of white lead pigment (basic lead carbonate, 2PbCO₃·Pb(OH)₂), used in wall paintings of historical interest, a yellow–brown discoloration has been observed around the crater. This phenomenon faded after a few days exposure under ambient atmosphere. It was established that the mechanism of this discoloration consists in lead oxides (PbO) formation. It was verified by further experiments under argon atmosphere that recombination of lead with oxygen in the plasma plume produces the oxides, which settle around the crater and induce this discoloration. The impact of discoloration on the artwork's aesthetic aspect and the role of atmosphere on discoloration attenuation are discussed. The mechanism is studied on three other pigments (malachite, Prussian blue and ultramarine blue) and threshold for discoloration occurrence is estimated.