Glancing-incidence X-ray diffraction of Ag nanoparticles in gold lustre decoration of Italian Renaissance pottery

Lustre is known as one of the most significant decorative techniques of Medieval and Renaissance pottery in the Mediterranean basin, characterized by brilliant gold and red metallic reflections and iridescence effects. Previous studies by various techniques (SEM-EDS and TEM, UV-VIS, XRF, RBS and EXAFS) demonstrated that lustre consists of a heterogeneous metal-glass composite film, formed by Cu and Ag nanoparticles dispersed within the outer layer of a tin-opacified lead glaze. In the present work the investigation of an original gold lustre sample from Deruta has been carried out by means of glancing-incidence X-ray diffraction techniques (GIXRD). The study was aimed at providing information on structure and depth distribution of Ag nanoparticles. Exploiting the capability of controlling X-ray penetration in the glaze by changing the incidence angle, we used GIXRD measurements to estimate non-destructively thickness and depth of silver particles present in the first layers of the glaze. PACS 61.10.Nz; 61.10.Eq; 81.70.-q; 61.46.+w     

XAFS study of copper and silver nanoparticles in glazes of medieval middle-east lustreware (10th–13th century)

It has recently been shown that lustre decoration of medieval and Renaissance pottery consists of silver and copper nanoparticles dispersed in the glassy matrix of the ceramic glaze. Here the findings of an X-ray absorption fine structure (XAFS) study on lustred glazes of shards belonging to 10th and 13rd century pottery from the National Museum of Iran are reported. Absorption spectra in the visible range have been also measured in order to investigate the relations between colour and glaze composition. Gold colour is mainly due to Ag nanoparticles, though Ag⁺, Cu⁺ and Cu²⁺ ions can be also dispersed within the glassy matrix, with different ratios. Red colour is mainly due to Cu nanoparticles, although some Ag nanoparticles, Ag⁺ and Cu⁺ ions can be present. The achievement of metallic Cu and the absence of Cu²⁺ indicate a higher reduction of copper in red lustre. These findings are in substantial agreement with previous results on Italian Renaissance pottery. In spite of the large heterogeneity of cases, the presence of copper and silver ions in the glaze confirms that lustre formation is mediated by a copper- and silver-alkali ion exchange, followed by nucleation and growth of metal nanoparticles.     

The use of small angle X-ray scattering (SAXS) for the characterisation of lustre surfaces in Renaissance majolica

In this work some Renaissance lustre decorated ceramics have been examined. Our attention was directed to lustre which is a thin decorative metallic film applied on the surfaces of previously glazed ancient pottery.Some 16th century lustre ceramics shards from Deruta, Umbria (Italy) have been analysed by small angle X-ray scattering (SAXS) in order to characterise the dimension of the metal nanocrystals forming the thin lustre layer. This technique appeared to be a powerful tool to characterise lustre films nanostructure and may be successfully used for this purpose together with transmission electron microscopy (TEM). Furthermore, SAXS measurements are extremely suitable for the determination of polydispersity and average interparticle distance.The lustre surfaces have been also analysed by scanning electron microscopy plus X-ray energy dispersive spectrometry (SEM–EDX) in order to identify the metals present (silver, copper or both of them) and to establish copper/silver ratios. From the comparison between SAXS results and compositional data, it was possible to conclude that copper particles are smaller than the silver ones. We have evidenced how the microtexture as well as the chemical composition of the lustre layers are responsible for the gold or red colour typical of the lustre films.     

How the masters in Umbria,Italy, generated and used nanoparticles in art fabrication during the Renaissance period

Lustre was one of the most sophisticated techniques for the decoration of majolicas during the Renaissance period. Lustre consists of a thin metallic film containing silver, copper and other substances like iron oxide and cinnabar applied in a reducing atmosphere on a previously glazed ceramic. In this way, beautiful iridescent reflections of different colours (in particular gold and ruby-red) are obtained. The characterisation and the study of lustre-decorated majolicas is of great interest for archaeologists, but also offers possibilities for producing pottery with outstanding decoration today, following ancient examples, since nowadays Italian artisans are interested in the reproduction of the ancient recipes and procedures. Moreover, it can even suggest new procedures for obtaining uniform thin metallic films for technological applications. A study has been carried out on ancient lustre layers using numerous different analytical techniques such as XRD, SEM–EDX, TEM–EDX–SAED, ETAAS, ICP–OES, UV–vis reflectance spectroscopy and SAXS. Lustre films were shown to be formed by copper and silver clusters of nanometric dimension. The colour and the properties of the lustre films depend on the elemental composition of the impasto applied to the ceramic surface as well as on other factors like the metallic nanocluster dimension, the firing conditions, the underlying glaze composition and the procedure used. Received: 12 August 2002 / Accepted: 14 August 2002 / Published online: 8 January 2003 RID="*" ID="*"Corresponding author. Fax: +39-6/9067-2445, E-mail: pad@mlib.cnr.it     

Heterogeneous distribution of metal nanocrystals in glazes of historical pottery

It has been recently shown that lustre decoration of medieval and renaissance pottery consists of silver and copper nanocrystals, dispersed within the glassy matrix of the ceramic glaze. Lustre surfaces show peculiar optical effects such as metallic reflection and iridescence. In many cases, lustre appears overlapped to colored drawings. Here we report the findings of a study on glazes, pigments and lustre of several shards belonging to Deruta and Gubbio pottery of XVI century. The components of glazes and pigments have been identified. Lustre is confirmed to be characterised by silver and copper metal nanocrystals inhomogeneously dispersed in the glassy matrix of the glaze. In the case of lustre overlapped to colored decorations, we found two contradictory cases. The first consists of a lustre surface successfully applied over a blue smalt geometrical drawing. The second consists of a lustre surface, unsuccessfully applied over a yellow lead-antimonate pigment. The yellow pigment hinders the formation of lustre and removes crystals of tin dioxide, normally present in the glaze as opacifier.     

A study of many-body phenomena in metal nanoclusters (Au, Cu) close to their transition to the nonmetallic state

The results of a study of many-body phenomena in gold and copper nanoclusters are presented. The measured conductivity as a function of nanocluster height h was found to have a minimum at h ≈ 0.6 nm. Conductivity was local in character at nanocluster sizes l ≤ l _c ≈ 2.5 nm. Changes in core hole screening and an anomalous increase in the Anderson singularity index α in gold and copper nanoclusters could be caused by changes in permittivity from metallic (? → ∞) to nonmetallic (? ∝ l ²). The many-body phenomenon characteristics observed in the X-ray photoelectron and tunnel spectra of gold and copper nanoclusters as the size of the nanoclusters changed led us to suggest changes in the band structure of the nanoclusters and, therefore, their possible transition from the metallic to nonmetallic state.     

Some aspects of the characterization of decorations on ceramic glazes

From antiquity, glazes have been one of the techniques used for decorating ceramics. Potters took advantage of the optical properties of these glazes to improve the quality of the object, especially to obtain an appearance or some characteristics that had commercial success. This is why it is important to know the reasons of the visual appearance of glazes. In this paper we present some aspects of the characterization of lustre, one of the on-glaze decorations that results in a more spectacular visual effect, as a microstructure, its composition, its raw materials and some technological aspects of its production. Lustre is a three-dimensional heterogeneous structure, where copper and silver nanoparticles play the most important role, but also alkali elements in the glaze and other components of raw lustre pigments. Lustre properties are determined by copper and silver composition and by distribution and dimension of these metallic nanocrystals in the decoration layer. PACS 61.46.+w; 68.37.Hk; 68.37.Lp; 81.05.-t; 79.60.-i; 81.07.-b ; 78.67.Bf; 81.05.Kf; 81.05.Je     

Characterisation of decorations on Iranian (10th–13th century) lustreware

It has been recently shown that lustre decoration of Medieval and Renaissance pottery consists of silver and copper nanoparticles, dispersed within the glassy matrix of the ceramic glaze. Lustre surfaces show peculiar optical effects, such as metallic reflection and iridescence. Here we report the findings of a study on lustred glazes of several shards belonging to Iranian pottery of the 10th and 13th centuries, decorated on both sides. Two different glazes, depending on the side of the sample, have been identified. Different lustre chromatic effects are characterised by the relative presence of silver- and copper-metal nanoparticles dispersed in the glassy matrix. PACS 61.46.+w     

Metal nanocluster formation in silica films prepared by rf-sputtering: an experimental study

Composite silica films containing metal nanoclusters were prepared by the rf- sputtering technique, in which SiO₂ was co-deposited with gold+copper, gold+silver, or copper+silver. The formation of either pure or alloy clusters was studied by extended X-ray absorption fine structure spectroscopy and transmission electron microscopy. For all systems, the presence of alloy aggregates was evidenced. Moreover, small amounts of pure metal aggregates as well as dispersed or oxidized dopants were observed. 61.46.+w Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals – 61.10.Ht X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc. – 81.05.Pj Glass-based composites, vitroceramics Received 29 June 2001     

Luster decoration of ceramics: mechanisms of metallic luster formation

Luster is a metallic decoration produced since early Islamic times (9th century AD in Iraq). Different studies have shown that medieval lusters are a metal-glass nanocomposite (metal nanoparticles embodied in a silica glassy matrix) obtained from the reaction of a copper and/or silver containing paint with a glaze. The mechanisms of formation of these metallic-like layers are investigated by laboratory reproductions of Medieval luster. Copper and silver lusters are obtained based on different thermal paths and atmospheres, and by using different glaze compositions. The ionic exchange between Cu⁺ and Ag⁺ ions from the luster paint with Na⁺ and K⁺ of the glaze, is demonstrated in either oxidizing or inert atmospheres and at firing temperatures between 500 °C and 600 °C. The reduction of copper and silver to their metallic state is obtained by introducing a reducing gas afterwards. The lusters are non-metallic red ruby copper or green with brown spots silver when developed over alkaline glazes, while they appear coppery and golden metallic when developed over mixed alkaline-lead glazes. SR-XRD, optical absorption and microprobe chemical analysis of the lusters indicate that the total amount of copper and silver, and the nature and size of the nanoparticles, are similar in both cases. Further work is needed to clarify the origin of these differences. PACS 81.05.Pj; 81.07.b; 81.16.Be; 78.67.Bf; 42.50.Fx     

Roman coloured and opaque glass: a chemical and spectroscopic study

This work reports the results of an archaeometrical investigation of opaque Roman glass and is mainly focussed on the role of configuration and oxidation state of copper on the colour and opacity of red and green opaque finds (mosaic tesserae, game counters, and glass artefacts) from Sicily and Pompeii excavations. The glass fragments were characterised by EMPA, SEM-EDS, TEM, and XRPD analyses and the copper local environment was investigated using X-ray absorption spectroscopy. The analyses of high-resolution Cu-K edge XANES and EXAFS spectra suggest that, in red samples, copper is present as monovalent cations coordinated to the oxygen atoms of the glass framework, accompanied by metallic clusters. In green samples all the copper cations are incorporated in the glass matrix. PACS 61.10.Ht; 61.43.Fs; 61.46.+w     

Modelization of the optical and colorimetric properties of lustred ceramics

The lustre decoration is one of the most famous decorations of glazed ceramics in the Mediterranean basin. Unfortunately, the recipes and fabrication techniques used during medieval times have been lost and that is why these objects have been widely studied. But until now, little was known on their optical properties. In this work it is shown that, despite the common belief, the chemical composition of the decoration (copper and/or silver nanoparticles) is not the only relevant parameter in order to explain the optical properties of lustres. By the use of optical characterization and the elaboration of a model – based on the Maxwell Garnett theory and the Abeles matrices theory for interferences –, simulated reflection spectra have been obtained in good agreement with the measured reflection spectra, confirming that the concentration of metal, the size of the metallic nanoparticles as well as the optical index of the glaze play a key-role in order to explain the coloured metallic shine exhibited by the lustres. PACS 70; 78; 78.20-e; 78.20.Bh; 78.20.Ci; 78.40.-q; 78.66-w; 78.67.Bf; 78.67.-n; 78.67.Pt     

Colouration mechanism of underglaze copper‐red decoration porcelain (AD 13th–14th century), China

Underglaze copper‐red decoration, i.e. the copper colourant used to paint diversified patterns on the surface of a body and then covered by transparent glaze and fired at high temperature in a reductive firing environment, is famous all over the world. However, the red colouration mechanism generated by underglaze copper remains unclear. In particular, the fact that the edges of the red patterns are orange has been ignored in previous research. Here, non‐destructive analysis has been carried out on a precious fragment of early underglaze red porcelain using synchrotron radiation X‐ray fluorescence, X‐ray absorption near‐edge spectroscopy (XANES) and reflection spectrometry techniques. The results suggest that the copper content in the red region is higher than that in the orange region, and other colour generation elements do not have obvious content difference, indicating that the colour generation effect of the underglaze red product is related to the copper content. XANES analysis shows that the valence states of copper in the red and orange regions are similar and metal copper contributes to their hues. The results of reflection spectrometry demonstrate that tiny orange hues could be attributed to the Mie scatting effect. Therefore, light‐scattering effects should be considered when researching the colouration mechanism of underglaze red.     

Size-controlled Pd nanocluster grown by plasma gas-condensation method

Syntheses of palladium (Pd) nanoclusters by sputtering gas-condensation technique are reported in this work. The Pd nanocluster size distribution and number of nanoclusters are found to depend on several factors which include the inert gas flow rate (f), sputtering discharge power, and growth region length. The discharge power and the length of the growth region are optimized to produce high nanocluster yield. It is found that low f produces small number of large nanoclusters which can be attributed to the formation of nanoclusters via the two-body collision mechanism. For high f, nanocluster size decreases and the number of nanocluster increases with f. This phenomenon can be assigned to nanocluster formation through three-body collision mechanism.     

Disorder effect on heat capacity,self-diffusion coefficient,and choosing best potential model for melting temperature,in gold–copper bimetallic nanocluster with 55 atoms

Molecular dynamics simulation has been implemented for doping effect on melting temperature, heat capacity, self-diffusion coefficient of gold–copper bimetallic nanostructure with 55 total gold and copper atom numbers and its bulk alloy. Trend of melting temperature for gold–copper bimetallic nanocluster is not same as melting temperature copper–gold bulk alloy. Molecular dynamics simulation of our result regarding bulk melting temperature is consistence with available experimental data. Molecular dynamics simulation shows that melting temperature of gold–copper bimetallic nanocluster increases with copper atom fraction. Semi-empirical potential model and quantum Sutton–Chen potential models do not change melting temperature trend with copper doping of gold–copper bimetallic nanocluster. Self-diffusion coefficient of copper atom is greater than gold atom in gold–copper bimetallic nanocluster. Semi-empirical potential within the tight-binding second moment approximation as new application potential model for melting temperature of gold–copper bulk structure shows better result in comparison with EAM, Sutton–Chen potential, and quantum Sutton–Chen potential models.     

Effect of a thioalkane capping layer on the first hyperpolarizabilities of gold and silver nanoparticles

We have measured the first hyperpolarizabilities of thioalkane capped silver and gold metallic nanoparticles. The values found are β(AgC 12-10 nm) = (2.10 ± 0.23) × 10(-26) esu for 10 nm diameter silver nanoparticles and β(AuC 18-18 nm) = (3.37 ± 0.08) × 10(-26) esu for 18 nm diameter gold nanoparticles at the fundamental wavelength of 784 nm. By comparison to the corresponding values reported for citrate capped silver and gold metallic nanoparticles, after size corrections, decreases by factors of 4.3 and 6.5 respectively are observed. These decreases are tentatively attributed to the bonds formed between the gold and silver surface atoms and the sulfur atoms of the capping layer.     

Structure of metal nanowires in nanoporous alumina membranes studied by EXAFS and X-ray diffraction

The structure of nanowires of different metals grown within nanoporous alumina membranes has been studied by EXAFS, WAXS and high energy X-ray diffraction. Nanowires of gold, silver, copper and iron adopt the lattice structure and bond distances of the bulk metals. Cobalt nanowires on the other hand were composed of a mixture of hcp phase, stable at room temperature, and fcc phase, which in bulk cobalt is normally stable only at high temperatures, in a ratio depending on the pore size. The nanowires are non-continuous but are made of nanocrystallites whose shape and size was found to depend strongly on the metal. All the metals except gold showed the presence of a preferred orientation which was slight in the case of Ag and Cu but much stronger in the case of iron and cobalt nanowires. Received 30 November 2000     

Synthesis of Atom‐Precise Chiral Ag14 Clusters Protected by Penicillamine Ligands

A pair of atom‐precise chiral silver(I) nanocluster enantiomers ( Ag₁₄‐d and Ag₁₄‐l ) protected by d ‐ and l ‐penicillamine ligands is reported. Crystallographic structures reveal that the nanoclusters consist of a S^2? template and a chiral Ag₁₄ core stabilized by 12 penicillamine ligands. The penicillamine ligands show two binding fashions: (i) only thiolate coordination, and (ii) thiolate and carboxylate co‐coordination. Meanwhile, the two enantiomers show strong circular dichroism with opposite signals (mirror image relationship) owing to the chiral metallic core induced by chiral ligands, suggesting that the nanoclusters have well‐defined stereostructures as common chiral molecules do. The proton conductivity is also explored due to the existence of both amino groups and carboxylate groups from the penicillamine ligands, which is beneficial to construct H‐bond network for proton transfer.     

Modelling the size of red-colouring copper nanoclusters in archaeological glass beads

The origin of a red colour in ancient soda-lime glasses has been attributed either to the presence of both copper clusters and cuprous oxide or to copper alone. As a contribution to this question, a non-destructive X-ray absorption study at the [ _Cu]K-edge was undertaken on the red layer from a singular “rosette”-type archaeological glass bead dated as pre-XVII century. On comparing with data collected from metallic copper and the mineral cuprite, cubic Cu₂O, XANES spectra of the red glass are identical to the first. Theoretical modelling of Cu 1s XANES spectra was undertaken using the FEFF code based on a multiple scattering formalism. A hypothetical tetragonal structure was simulated for Cu₂O in order to remove the constraints arising from linear O–Cu–O bonds, unstable within the silica glass matrix, and an ideal body-centred array was considered on the basis of real metallic Cu–Cu distances in the metal. Calculations were performed for atom clusters of variable size within real and hypothetical structures. A spherical cluster of about 5 Å radius, capped by 24 copper atoms already provides a calculated Cu 1s XANES spectrum that compares well with data collected from the red glass. Post-edge details are noted in relation to the oxide, considering ionic states and effective valences of copper. The possibility of estimating the size of copper clusters through simulated structures is discussed.