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When exposed to air, silver artifacts undergo an unpleasant darkening and shiny loss, commonly known as tarnishing. At the present, the development of protective coatings by using eco-friendly and biocompatible materials, able to ensure high transparency and to hinder the degradation of silver objects, remains a huge challenge. In this study, chitosan was used for the first time to realize sustainable coatings for silver protection. Both pure and benzotriazole-containing chitosan coatings were prepared and applied on sterling silver disks. A commercial product based on acrylic resin was used as a reference. The aesthetic features and protective properties of these coatings were evaluated by performing two different types of aging treatments. In particular, the assessment of the protective efficacy was carried out by reproducing both highly aggressive polluted environments and real-like museums’ storage conditions. In the first case, chitosan-based coatings with benzotriazole performed better, whereas in storage conditions all the chitosan films showed comparable efficacy. Compositional, morphological and structural analyses were used to evaluate the protective properties of the coatings and to detect any physical or chemical modifications after the aging treatments. Our findings reveal that the two different testing methods provide complementary information. Moreover, chitosan coatings can achieve protective efficacy comparable with that of the commercial product but using non-toxic solvents and a renewable biopolymer. Chitosan coatings, designed for cultural heritage conservation, are thus promising for the protection of common sterling silver objects.

The outcomes of adhesion and ecotoxicity tests carried out on metal specimens faithfully representing the surface of real ships, including the primer and tie coat layers typically applied on ship hull prior to deposition of the antifouling paint, show the practical applicability of "AquaSun" antifouling sol-gel coatings. Newly developed AquaSun coatings share superhydrophicity (contact angle >115) and exceptionally high scratch resistance (ASTM 5B). Coupled to the ecofriendly antifouling mechanism based on continuous H2O2 formation upon exposure to solar light and foul release due to low surface energy, these results open the route to the practical utilization of these novel marine coatings.

The recycling of plastic waste is undergoing fast growth due to environmental, health and economic issues, and several blends of post-consumer and post-industrial polymeric materials have been characterized in recent years. However, most of these researches have focused on plastic containers and packaging, neglecting hard plastic waste. This study provides the first experimental characterization of different blends of hard plastic waste and virgin polypropylene in terms of melt index, differential scan calorimetry (DSC), thermogravimetric analysis (TGA), mechanical properties (tensile, impact and Shore hardness) and Vicat softening test. Compared to blends based on packaging plastic waste, significant differences were observed in terms of melt flow index (about 10 points higher for hard plastic waste). Mechanical properties, in particular yield strain, were instead quite similar (between 5 and 9%), despite a higher standard deviation being observed, up to 10%, probably due to incomplete homogenization. Results demonstrate that these worse performances could be mainly attributed to the presence of different additives, as well as to the presence of impurities or traces of other polymers, other than incomplete homogenization. On the other hand, acceptable results were obtained for selected blends, the optimal blending ratio was identified as 78% post-consumer waste and 22% post-industrial waste, meeting the requirement for injection molding and thermoforming.

The long-term interaction between Cu-based alloys and environmental species gives rise to the formation of different and sometimes unusual compounds (i.e., the patina) with distinctive chemical and structural features as a function of the peculiar characteristics of the context. In this paper, we describe some representative case studies concerning degraded bronze Roman valuable or common use objects, and we show that an attentive study at a microscale level, as for forensic analysis, allows one to understand the chemical processes that underlie the formation of the surface alteration products. The achieved information describe fragments of chemical life and disclose the complex chemical changes suffered by the artifacts, allowing one to write their chemical biography. This challenging approach expands the panorama of available information and demonstrates that it is possible to reconstruct the different modes through which the bronze surfaces and interfaces have interacted with environmental species, organic matter, and microorganisms, opening up a new possibility to describe complex environmental chemical stories, in certain cases interrelated.

Lynch syndrome is a hereditary cancer-predisposing syndrome caused by germline defects in DNA mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2. Carriers of pathogenic mutations in these genes have an increased lifetime risk of developing colorectal cancer (CRC) and other malignancies. Despite intensive surveillance, Lynch patients typically develop CRC after 10 years of follow-up, regardless of the screening interval. Recently, three different molecular models of colorectal carcinogenesis were identified in Lynch patients based on when MMR deficiency is acquired. In the first pathway, adenoma formation occurs in an MMR-proficient background, and carcinogenesis is characterized by APC and/or KRAS mutation and IGF2, NEUROG1, CDK2A, and/or CRABP1 hypermethylation. In the second pathway, deficiency in the MMR pathway is an early event arising in macroscopically normal gut surface before adenoma formation. In the third pathway, which is associated with mutations in CTNNB1 and/or TP53, the adenoma step is skipped, with fast and invasive tumor growth occurring in an MMR-deficient context. Here, we describe the association between molecular and histological features in these three routes of colorectal carcinogenesis in Lynch patients. The findings summarized in this review may guide the use of individualized surveillance guidelines based on a patient’s carcinogenesis subtype.

The prognosis of locally advanced colorectal cancer (CRC) is currently unsatisfactory. This is mainly due to drug resistance, recurrence, and subsequent metastatic dissemination, which are sustained by the cancer stem cell (CSC) population. The main driver of the CSC gene expression program is Wnt signaling, and previous reports indicate that Wnt3a can activate p38 MAPK. Besides, p38 was shown to feed into the canonical Wnt/β-catenin pathway. Here we show that patient-derived locally advanced CRC stem cells (CRC-SCs) are characterized by increased expression of p38α and are “addicted” to its kinase activity. Of note, we found that stage III CRC patients with high p38α levels display reduced disease-free and progression-free survival. Extensive molecular analysis in patient-derived CRC-SC tumorspheres and APCMin/+ mice intestinal organoids revealed that p38α acts as a β-catenin chromatin-associated kinase required for the regulation of a signaling platform involved in tumor proliferation, metastatic dissemination, and chemoresistance in these CRC model systems. In particular, the p38α kinase inhibitor ralimetinib, which has already entered clinical trials, promoted sensitization of patient-derived CRC-SCs to chemotherapeutic agents commonly used for CRC treatment and showed a synthetic lethality effect when used in combination with the MEK1 inhibitor trametinib. Taken together, these results suggest that p38α may be targeted in CSCs to devise new personalized CRC treatment strategies.

The protection of metals from atmospheric corrosion is a task of primary importance for many applications and many different products have been used, sometimes being toxic and harmful for health and the environment. In order to overcome drawbacks due to toxicity of the corrosion inhibitors and harmful organic solvents and to ensure long-lasting protection, new organic compounds have been proposed and their corrosion inhibition properties have been investigated. In this work, we describe the use of a new environment-friendly anticorrosive coating that takes advantage of the synergism between an eco-friendly bio-polymer matrix and an amino acid. The corrosion inhibition of a largely used Copper-based (Cu-based) alloy against the chloride-induced indoor atmospheric attack was studied using chitosan (CH) as a biopolymer and l-Cysteine (Cy) as an amino acid. To evaluate the protective efficacy of the coatings, tailored accelerated corrosion tests were carried out on bare and coated Cu-based alloys, further, the nature of the protective film formed on the Cu-based alloy surface was analyzed by Fourier-transformed infrared spectroscopy (FTIR) while the surface modifications due to the corrosion treatments were investigated by optical microscopy (OM). The evaluation tests reveal that the Chitosan/l-Cysteine (CH/Cy) coatings exhibit good anti-corrosion properties against chloride attack whose efficiency increases with a minimum amount of Cy of 0.25 mg/mL.

The photodegradation kinetics of 2‐mercaptobenzothiazole (MBT), a corrosion inhibitor for copper‐based alloys, is studied in high amorphous polyvinyl alcohol coatings subjected to either UV irradiation or indoor light exposure. The photodegradation process proceeds rapidly, thus compromising the anticorrosion ability of the coating. The encapsulation of MBT into layered double hydroxide (LDH) nanocarriers slows down its decomposition kinetics by a factor of three. Besides preserving the corrosion inhibitor, such a strategy allows a controlled release of MBT triggered by corrosion‐related stimuli, for example, presence of chloride species and acid pH. The developed coating guarantees long‐lasting corrosion protection even at low amounts of inhibitor‐loaded LDH nanocarriers (ca. 5 wt %). This also reflects in a high transparency, which makes the protective coating suitable for demanding applications, such as the conservation of high‐value metal works of art.

Solvent- (SB) and water-borne (WB) fluoropolymer coatings were produced for the outdoor protection of bronze. The coatings were prepared from commercially available resins with alternating fluoroethylene/vinylether copolymers. Because any application of protective coatings on works of art requires that they be removable in accordance with conservation ethics, various approaches to achieve removability of coatings were tested. The influence of modifications was verified through comparisons of hydrophobic, compact and irremovable protective coatings. Consequently, we prepared four types of coatings: two SB coatings and two WB coatings. The first SB coating was designed to have a hydrophobic compact structure (SB-c coating), and the second SB coating was modified with the addition of agents that impart strippability (SB-h coating). The same approach was used for the preparation of the two WB coatings: a compact (WB-c) coating vs. a hydrophilic (WB-h) coating, the latter being prepared through the addition of hydrophilic polyisocyanate. The surface properties of the coatings were compared using scanning electron (SEM) and atomic force (AFM) microscopy. WB coatings were found to be more homogeneous in comparison with SB coatings and to have lower surface roughness. Contact angles confirmed the more hydrophobic nature of SB coatings. Potentiodynamic polarisation measurements and accelerated corrosion tests (exposure to acid vapours) revealed that protection efficiency not only increased with thickness but significantly depended on the coating structure. The structure of coatings depended on the rheological parameters of the formulations simulating their behaviour during storage, deposition, and formation of the dry coating. Combined electrochemical and vibrational spectroscopic experiments were used to simulate long-term outdoor exposure of the protective coatings. Ex situ IR RA spectroelectrochemical measurements showed that hydration was more prevalent with WB coatings, and oxidation of bronze at the interface eventually occurred (656 cm −1 band). WB coatings with more free C O groups were more prone to degradation. In situ Raman spectroelectrochemistry confirmed the better protection efficiency of SB over WB coatings. The optical properties of the coatings on glass showed higher transmittance for WB coatings compared to SB coatings.

The corrosion products naturally formed on archaeological Cu-based artefacts during their long-term exposure to seawater have been investigated in details by means of X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectrometry (SEM + EDS), optical microscopy (OM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential thermal analysis-thermogravimetry (DTA-TG), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS). The bronze artefacts include fragments of valuable statues and objects that were retrieved some decades ago from different seabeds along the Italian coast of the Mediterranean basin including the so called “Punta del Serrone” area (Apulia), the Sicilian channel (Sicily) and the Arburese coast (Sardinia). Our findings show that the alloy matrix is often heavily corroded also in the bulk and reveal the dangerous presence of chlorine from seawater as main dangerous corrosive agent. Chlorine is present as copper nantokite (CuCl) in the inner layers of the patina and is potentially inducing with oxygen and moisture the cyclic and often relentless copper degradation phenomenon commonly called “bronze disease”. The most common corrosion products are also lead carbonate (cerussite, PbCO3) and aragonite (CaCO3), likely related to the large abundance of CO2 in the seawater where is assimilated much more than in fresh water. Furthermore, the results reveal that other environmental elements contributing to the composition of the patina are sulphur, magnesium and phosphorous thus giving rise to a patina with a chemically and structurally complex structure. The results reveal also the contribution of bio-organism to the formation of the patina as supported by the presence of vanadium and copper sulphides. These information allow, as a whole, to propose a tentative correlation between the patina’s nature, the chemical composition and metallurgical features of the alloys and the marine environment where the objects lived for about two thousands years. From a conservation point of view, the findings reported in this work can provide some insights useful to tailor more efficient conservation strategies with the purpose to ensure a long-term chemical-physical stability to the bronze artefacts.

Two-component solvent-born polyurethane coatings for the protection of bronze from corrosion were prepared. Trisilanol-heptaisooctyl polyhedral oligomeric silsesquixane (POSS) nanoparticles were exploited to increase the coating protective efficiency. Its improvement was confirmed through a combination of characterisation techniques. In particular, the POSS addition caused an increase of the water contact angle, and an enhancement of the elastic connotation and abrasion resistance of the polyurethane coating. Potentiodynamic polarisation measurements also indicated that the coating containing POSS nanoparticles has an improved protection efficiency. Impedance spectroscopy revealed that the magnitude of low-frequency impedance of polyurethane coatings decreased more for the coating without POSS during exposure in electrolyte for thirty days. Ex situ IR reflection-absorption spectroelectrochemistry was exploited to get insight into the degradation of coatings during chronocoulometric charging at anodic potentials. IR reflection-absorption technique was also used to evaluate any possible effect of different stripper solutions on the bronze substrate.

The attractive physicochemical properties of chitosan make its derived materials promising candidates for the reliable and sustainable corrosion protection of metallic substrates. In this work, chitosan-based coatings embedding different corrosion inhibitors, i.e. benzotriazole (BTA) and mercaptobenzothiazole (MBT), were investigated for the protection of copper-based alloys, with the aim to extend their application to the preservation of works of art exposed to indoor atmosphere. The composition of the formulations was optimized paying particular attention to their potential application in the field of cultural heritage. To assess the efficacy of the coatings, tailored accelerated corrosion tests were carried out on bare and coated bronze substrates. Coated and uncoated alloy disks were characterized before and after corrosion treatments by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Moreover, an image analysis protocol was defined to evaluate the extent of surface modifications after degradation treatments. The obtained results revealed that the chitosan-based coatings containing BTA and MBT fulfil the aesthetic criteria required in the field of cultural heritage and are able to inhibit the corrosion of bronze alloys. It is worth noting that a synergic effect between the chemical protection provided by the inhibitors and the physical one provided by the polymer matrix was observed. Our findings demonstrate that the developed systems are suitable for a reliable and more sustainable protection of indoor bronze artefacts, thus representing a promising alternative to commercial products and particularly taking advantage from the use of non-harmful solvents for their application and removal.

In this work, the absorption of N719 dye on titania films with significantly different morphologies has been investigated. By changing the synthetic approach, we have prepared sol-gel titania films with a flat surface (TiSG), mesoporous films with an ordered porous structure (TiMS) and a reference film from commercial titania P25 using the well-known doctor-blade technique (TiDB). The surface roughness and grain size distribution of titania films has been explored by atomic force microscopy. The effectiveness of the various type of titania films to absorb the N719 dye has been investigated by UV-vis spectroscopy, whereas the dye-titania interaction was examined by Raman spectroscopy. Further information on the structural and morphological properties of titania films were obtained by small angle X-ray diffraction and scanning electron microscopy. Both sol-gel and mesoporous titania films were deposited by spin-coating the solution of titania precursor, which produces films of about 300 nm, much thinner than those afforded by the doctor-blade technique (similar to 6.8 mu m). When the thickness of TiMS film was increased up to 1 mu m, the absorbance of dye-sensitized titania became also higher, reaching levels similar to those of the reference N719-TiDB film in spite of its lower thickness. Our findings show that the morphological properties of titania substrates affect their ability to adsorb the N719 dye and, in particular, it was observed an enhanced dye adsorption onto meso-structured titania. N719 absorbance normalized to titania film thickness reveals that both the roughness and porosity of titania promote the dye adsorption. The much higher ability of meso-structured photoanodes to adsorb the dye can be attributed to the ordered and highly porous structure of TiMS. The photocurrent-voltage measurements of TiMS and TiDB dye sensitized films with similar thickness (similar to 500 nm) have shown the superiority of N719-TiMS thus suggesting the key role of the mesoporous structure.

Protective coatings based on polymers synthesized from renewable sources (chitosan or an amorphous vinyl alcohol based polymer) have been prepared for the protection of bronze artifacts from corrosion. Besides acting as an effective barrier against corrosive species present in the environment, the efficiency of the coatings has been improved by adding corrosion inhibitor compounds (benzotriazole or mercaptobenzothiazole) to the formulations. The liquid medium of the formulations has been carefully selected looking at maximizing the wettability on the bronze substrate and optimizing the solvent evaporation rate. The minimum amount of inhibitor compounds has been optimized by performing accelerated corrosion tests on coated bronze substrates. The inhibitors have been directly dissolved in the coating-forming solutions and/or introduced by means of nanocarriers, which allow to control the release kinetics. The free dissolved inhibitor molecules immediately provide a sufficient protection against corrosion. On the other hand, the inhibitor molecules contained in the nanocarriers serve as long-term reservoir, which can be activated by external corrosion-related stimuli in case of particularly severe conditions. Particular attention has been paid to other features which affect the coating performances. Specifically, the adhesion of the protective polymer layer to the bronze substrate has been assessed, as well as its permeability properties and transparency, the latter being a fundamental feature of protective coating for cultural heritages. Finally, the protective efficiency of the produced smart coatings has been assessed through accelerated corrosion tests.

Twenty five years ago, close to the northern Peruvian town of Lambayeque (Huaca Rajada) beneath two large and eroded pyramids, built of adobe mud bricks, Professor Alva discovered the world-famous unlooted pre-Columbian burial chambers of the Royal Tombs of Sipan. The tombs contained a large amount of objects of exceptional artistic and historical value including the greatest intact number of gold and silver artefacts in the Americas to be considered one of the most important archaeological discoveries of the last century. Some copper based objects coated with thin layers of gold have been studied by means of the combined use of analytical techniques such as optical microscopy (OM), scanning electron microscopy coupled with energy dispersive X-ray micro-analysis (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) in order to identify the chemical composition and the manufacturing processes of the gold layer as well as the corrosion products formed during the long-term burial. The micro-chemical and structural results give useful information about the manufacturing techniques used by the Moche metalsmiths to modify the surface chemical composition of the coated artefacts likely based on the depletion gilding process carried out by oxidising the surface copper containing the noble metal and etching away the copper oxides. Furthermore, the results reveal that the main degradation agent is the ubiquitous chlorine and that copper has been almost completely transformed during the burial into mineral species giving rise to the formation of stratified structures constituted by different mineral phases such as cuprous oxide (Cu2O) and copper carbonates [azurite (Cu3(CO3)2(OH)2 and malachite (CuCO3Cu(OH)2)] as well as dangerous chlorine-based compounds such as nantokite (CuCl) and atacamite (Cu2(OH) 3Cl) polymorphs. These information evidence the strict interaction of the alloying elements with the soil components as well as the occurrence of the copper cyclic corrosion as post-burial degradation phenomenon. The present study confirms that the combined use of micro-chemical and micro-structural investigation techniques such as SEM-EDS, XPS, XRD, and OM can be successfully used to investigate the technological manufacturing processes of the ancient coated artefacts and to achieve information about degradation agents and mechanisms useful to define tailored conservation strategies possibly including new, more reliable, and safer materials.

Improving the electrical and thermal properties of conductive adhesives is essential for the fabrication of compact microelectronic and optoelectronic power devices. Here we report on the addition of a commercially available conductive resin with double-wall carbon nanotubes and graphene nanoplatelets that yields simultaneously improved thermal and electrical conductivity. Using isopropanol as a common solvent for the debundling of nanotubes, exfoliation of graphene, and dispersion of the carbon nanostructures in the epoxy resin, we obtain a nanostructured conducting adhesive with thermal conductivity of similar to 12 W/mK and resistivity down to 30 mu Omega cm at very small loadings (1% w/w for nanotubes and 0.01% w/w for graphene). The low filler content allows one to keep almost unchanged the glass-transition temperature, the viscosity, and the curing parameters. Die shear measurements show that the nanostructured resins fulfill the MIL-STD-883 requirements when bonding gold-metalized SMD components, even after repeated thermal cycling. The same procedure has been validated on a high-conductivity resin characterized by a higher-viscosity, on which we have doubled the thermal conductivity and quadrupled the electrical conductivity. Graphene yields better performances with respect to nanotubes in terms of conductivity and filler quantity needed to improve the resin. We have finally applied the nanostructured resins to bond GaN-based high electron-mobility transistors in power-amplifier circuits. We observe a decrease of the GaN peak and average temperatures of, respectively, similar to 30 degrees C and similar to 10 degrees C, with respect to the pristine resin. The obtained results are important for the fabrication of advanced packaging materials in power electronic and microwave applications and fit the technological roadmap for CNTs, graphene, and hybrid systems.

Gold-chitosan nanocomposite is successfully proposed for assembling a sensitive and selective electrochemical sensor for the determination of an antioxidant such as caffeic acid, which has recently attracted much attention due to its benefits on human health. In this paper, taking advantage of the peculiar sensing performance of the nanocomposite, an analytical method based on differential pulse voltammetry for determination of polyphenol index in wines was proposed.

Bronze is a metal alloy that is commonly used for statuary, but also as decorative element in architecture. Naturally, the surface of bronze monuments tends to passivation and formation of patina. This acts as protection, but can also have a decorative value. Anyhow, in certain conditions an artificial protection of bronze sculptures is also desired. Waxes and polymeric protection (Incralac, Sotter, …), also in combinations of layers, are mostly used nowadays. However, in order to prepare more effective solutions for protection, there have been performed some studies on possibilities for application of organic coatings (benzotriazole [1,2]) and various polymeric protective coatings like acrylate/methacrylate [3], fluoropolymers [1], polyurethanes [4] and sol-gel [5,6]. Since conservators demand that the coatings have to be removable, sol-gel coatings are often overlooked. Various strippers, for example on the basis of benzyl alcohol, can be applied to remove polymeric coatings from bronze surfaces. From environmental point of view, the studies of polymeric coatings are not prepared only from solvent-born formulations, but are shifted also to water-born formulations and comparison of both types of coatings [3]. Herein is reported the investigation of fluoropolymer and polyurethane protective coatings for bronze. The characterization of these coatings was made by using different analytical techniques. For structural determination, infrared (IR) and Raman vibrational spectroscopies were applied. Surface characteristics were determined by scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements. Protective efficiency was analyzed using electrochemical techniques like potentiodynamic polarization and electrochemical impedance spectroscopy. As more advanced analytical techniques, there were applied ex situ IR reflection-absorption (IR RA) and in situ Raman spectroelectrochemistry. The analyzed coating is in both spectroelectrochemical techniques gradually chronocoulometrically charged at more and more positive anodic potentials to follow the eventual degradation processes that are analyzed spectroscopically after each charging. IR RA spectra are measured in near grazing incidence angle assembly using an angle of 80° and P polarized IR radiation. In such spectra longithudinal optical (LO) modes appear that are commonly shifted towards higher wavenumbers compared to usual transversal optical (TO) modes from absorbance IR spectra. The disadvantage is the contact of electrochemically treated protective coating with atmosphere. This circumstance is overcome in in situ Raman spectroelectrochemical technique. The coating on bronze is mounted in a custom-made Tephlon in situ three-electrode cell. The counter electrode is platinum grid and the reference electrode Ag/AgCl. All electrochemical experiments are performed in 0.5 M sodium chloride. Fluoropolymer coatings are prepared from resins on the basis of fluoroethylene/vinyl ether (FEVE) alternating copolymers (Asahi Glass Company, Japan). The building unit of FEVE compounds is -CF2-CFX-. Solvent- and water- born formulations are made from appropriate resins, by applying corresponding poly(isocyanate) hardener, defoamer, light stabilizers, surfactants and co-solvents. Results confirm that the higher contact angles for water are achieved for solvent-born coatings (> 100°) than for water-born coatings (< 80°). Potentiodynamic polarization measurements are in accordance with these values, suggesting higher protective effectivity of solvent-born coatings. The use of water-born coatings for outside long-term protection of bronze is questionable, since the ex situ IR RA measurements showed that after treatment at high anodic potential the coating becomes much thinner. Consequently, the band at 565 cm-1 appeared in the IR RA spectrum and can be assigned to Cu2O of the bronze substrate. Similarly, also the in situ Raman spectra showed that after application of long anodic chronocoulometric pulse the coating burned and detached from the bronze substrate. Solvent-born coatings reveal more stable behavior through in situ Raman spectroelectrochemical measurements. Solvent-born polyurethane protective coatings show hydrophobic properties and the contact angle of 110°. Relatively good protective properties are confirmed through potentiodynamic polarization curves, impedance spectroscopy and ex situ IR RA measurements. The latter technique shows quite stable response during forced degradation at high anodic potentials. The activity is carried out within the framework of the NANORESTART project which has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 646063. References: [1] G. Bierwagen, T.J. Shedlosky, K. Stanek, Prog. Org. Coat. 48 (2003) 289-296. [2] G. Brunoro, A. Frignani, A. Colledan, C. Chiavari, Corros. Sci. 45 (2003) 2219-2231. [3] N.A. Swartz, T.L. Clare, Electrochim. Acta 62 (2012) 199-206 [4] T.J. Shedlosky, A. Huovinen, D. Webster, G. Bierwagen, Proceedings of Metal 2004, National museum of Australia Canberra ACT, pp. 400-412. [5] E. Bescher, J.D. Mackenzie, J. Sol-Gel Sci. Technol. 26 (2003) 1223-1226. [6] E. Kiele, J. Senvaitiene, A. Griguceviciene, R. Ramanauskas, R. Raudonis, A. Kareiva, Microchem. J. 124 (2016) 623-628.

Cobalt nanostructures with different size and morphology, i.e., spherical nanoparticles, nanorods, and particles arranged into elongated structures, were prepared using micelles and microemulsions as confined reaction media. The syntheses were carried out using three types of systems: aqueous surfactant solutions, oil-in water (O/W), and water-in-oil (W/O) microemulsions. The influence of the surfactant and the precipitating agent used for synthesis was also investigated. For this purpose, cobalt nanostructures were prepared using different non-ionic surfactants, namely Synperonic® 10/6, Pluronic® P123 and a mixture of SPAN 20–TWEEN 80. Three different precipitating agents were used: sodium borohydride, sodium hydroxide, and oxalic acid. Our findings revealed that by changing the type of reaction media as well as the precipitating agent it is possible to modify the shape and size of the cobalt nanostructures. Moreover, the use of O/W microemulsion generates better results in terms of colloidal stability and uniformity of particle size with respect to W/O microemulsion. The different cobalt nanostructures were supported on commercial and mesoporous silica, transmission electron microscopy (TEM) images showed that after deposition the Co nanocrystals remain well dispersed on the silica supports. This behavior suggests their great potential in catalytic applications.

Given the importance of nanomaterials and nanostructures in modern technology, in the past decades much effort has been directed to set up efficient protocols for nanoparticle synthesis. Since nanoparticles tend to spontaneously grow and their properties are critically size/shape/composition-dependent, a useful synthetic route should allow fine size, shape and chemical composition control and, more importantly, should permit to govern their spontaneous or directed assembling and interconnections to form structures at higher level of complexity with designed properties and functionalities. The aim of this contribution is to furnish to the reader a panoramic view of this exciting problematic and of the recently developed methods employed for obtaining complex nanostructure-based systems

In this work, the redox behaviour of structurally related antioxidants, such as catechol, hydroxycinnamic acid and flavonoid derivatives, has been investigated at electrode surfaces modified with different gold nanoparticles (AuNPs)–chitosan films. Our findings demonstrate that the chemical structural features of the antioxidants play a key role in the interaction with modified electrodes that strongly affect the electrochemical response. In particular, a better response was observed for molecules with two hydroxyl groups in ortho position of the catechol ring and with a low steric hindrance. However, the redox behaviour cannot be explained only on these bases, since the nanostructure and surface functional groups of AuNPs–chitosan modified electrodes have also to be considered. The presence of interconnected metal nanoparticles into chitosan film strongly affects the electron transfer properties, whereas the surface functional groups can promote the interaction with selected antioxidants acting as scavenger. The understanding of the key factors that affect the electrochemical response of antioxidants at electrode surface modified with nanostructured hybrid films is a key issue and could significantly contribute to the development of highly efficient electrochemical sensors.

Fire gilding and silvering are age-old mercury-based processes used to coat thesurface of less precious substrates with thin layers of gold or silver. In ancient times, these methods were used to produce and decorate different types of artefacts, such as jewels, statues, amulets, and commonly-used objects. Gilders performed these processes not only to decorate objects but also to simulate the appearance of gold or silver, sometimes fraudulently. From a technological point of view, the aim of these workmen over 2000 years ago was to make the precious metal coatings as thin and adherent as possible. This was in order to save expensive metals and to improve the resistance to the wear caused by continued use and circulation. Without knowledge about the chemical-physical processes, the ancient crafts-men systematically manipulated these metals to create functional and decorative artistic objects. The mercury-based methods were also fraudulently used in ancient times to produce objects such as jewels and coins that looked like they were made of silver or gold but actually had a less precious core. These coins were minted by counterfeiters but also by the official issuing authorities. The latter was probably because of a lack of precious metals, reflecting periods of severe economic conditions. In this Account, we discuss some representative cases of gold- and silver-coatedobjects, focusing on unique and valuable Roman and Dark Ages period works of art, such as the St. Ambrogio's altar (825 AD), and commonly used objects. We carried out the investigations using surface analytical methods, such as selected area X-ray photoelectron spectroscopy and scanning electron microscopy combined with energy-dispersive spectroscopy. We used these methods to investigate the surface and subsurface chemical features of these important examples of art and technology, interpreting some aspects of the manufacturing methods and of disclosing degradation agents and mechanisms. These findings may contribute to cultural heritage preservation, thus extending the applicability of the surface analytical techniques.

The Samnite bronze belts and the chest disk cuirasses (VIII-IV BC) are the distinctive defensive weapons of the Samnite warriors having likely also a symbolic relevance. These artefacts were mainly found during the archaeological excavations of warriors' graves from ancient Abruzzo (central Italy). Their chemical composition, metallurgical features and corrosion products formed during the long-term burial have been studied by means of the combined use of analytical techniques such as optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray micro-analysis (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The micro-chemical and structural results show that the bronze belts have often been produced by using unusual high-tin bronze alloys achieving a silver-like appearance and by performing tailored cycles of thermal treatments under reducing conditions and hot mechanical working aimed to shape the high-tin alloys in the form of a thin bronze sheet. Furthermore, the investigation has shown that the main alloying elements have been transformed during the burial into mineral species giving rise to the formation of stratified structures constituted by different mineral phases such as tin oxides, cuprous oxide (Cu2O) and copper carbonates (azurite (Cu-3(CO3)(2)(OH)(2) and malachite (CuCO3Cu(OH)(2))) as well as dangerous chlorine-based compounds such as nantokite (CuCl) and atacamite (Cu-2(OH)(3)Cl) polymorphs. This information evidences the strict interaction of the alloying elements with the soil components as well as the occurrence of the copper cyclic corrosion as a post-burial degradation phenomenon. The present study confirms that the combined micro-chemical and micro-structural investigation techniques such as SEM-EDS, XPS, XRD and OM can be successfully used to investigate the technological production processes of the ancient artefacts and to achieve the detailed micro-chemical and structural description of the corrosion products useful for the identification of degradation agents and mechanisms and, thereafter, to propose a reliable tailored strategy for the conservation.

An engineered bi-layered photoelectrode fordyesolar cells has been developed which profitably employs two synergistic meso-ordered components, namely a thin meso-ordered TiO2film and a main microparticles-based photoelectrode. The former has been deposited as an interfacial layer at the FTO-coated substrate and suppresses the back-transport reaction by blocking direct contact between the electrolyte and conductiveoxide. The latter is made of hierarchical micro- and nano-structured building blocks prepared by template synthesis, which permits efficient light scattering without sacrificing the internal surface area. The optimization of light harvesting and charge recombination dynamics allowed us to achieve as high energy conversion efficiency as 9.7%.

The microstructure and chemical composition of blue cakes, found during the archaeological excavation of the Ayanis fortress (Eastern Anatolia, Turkey), have been investigated by means of scanning electron microscopy combined with energy dispersive spectrometry (SEM–EDS), X-ray diffraction (XRD), micro-Raman (μ-Raman) and optical microscopy (OM) techniques. The analysis of the Ayanis cakes has shown the presence of Egyptian blue (i.e. CuCaOSi 4 O 10 , cuprorivaite), as the major component, intermixed with minor amount of other phases such as partially reacted quartz grains, an adherent glass phase and copper oxides. Since the finding of Egyptian Blue in Turkey has been never reported so far, great attention has been paid to its characterisation. The micro-chemical and micro-structural investigations of the Ayanis cakes have allowed a further insight into the manufacturing process and into the sources of the starting materials. The results of the characterisation have revealed some significant differences with respect to Egyptian blue cakes found in Egypt and Mesopotamia, as for instance the absence of tin excluded the use of bronze scraps or filings in their preparation differently from those produced in Egypt and Mesopotamia. Furthermore, some peculiarities of Egyptian blue found in Ayanis, as the detection of zinc in the cakes, allow to put forward the hypothesis of a local production considering that a large part of the bronze artefacts found at the Ayanis fortress is characterised by the presence of zinc as minor alloying element.

Different mesoporous SBA-15 supports doped with Ti and Al at 5 and 10 wt% have been synthesized by means of direct synthesis. The supports have been characterized by N2-adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), NH3-temperature programmed desorption (NH3-TPD), H2-chemisorption, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM). Titanium doped materials showed to have much shorter channels than the pristine SBA-15, while aluminum addition did not have a significant effect on channel length. After impregnation with 12 wt% Co, the catalysts were further characterized and tested in the Fischer-Tropsch synthesis at industrially relevant process conditions (483 K, 20 bar, H2/CO ratio = 2.1, pellet size: 53-90 ?m) with and without external water addition. The SC5+ values of the different SBA-supported catalysts were low, especially at low conversion levels (i.e. low water partial pressure), suggesting that CO diffusion limitations increased the H2/CO ratio inside the 1-dimensional (1D) porous network. The selectivity data showed a correlation between the channel length and the extent of CO-diffusion limitations at much shorter diffusion distances than those for conventional 3D porous supports. Water partial pressure showed to increase the syngas diffusion rate (i.e. removal of diffusion limitations on reactants' arrival), to have a positive kinetic effect on the rate and to favor longer chain hydrocarbons.

In this work, colloidal gold nanoparticles (AuNPs) stabilized into a chitosan matrix were prepared using a green route. The synthesis was carried out by reducing Au(III) to Au(0) in an aqueous solution of chitosan and different organic acids (i.e., acetic, malonic, or oxalic acid). We have demonstrated that by varying the nature of the acid it is possible to tune the reduction rate of the gold precursor (HAuCl(4)) and to modify the morphology of the resulting metal nanoparticles. The use of chitosan, a biocompatible and biodegradable polymer with a large number of amino and hydroxyl functional groups, enables the simultaneous synthesis and surface modification of AuNPs in one pot. Because of the excellent film-forming capability of this polymer, AuNPs-chitosan solutions were used to obtain hybrid nanocomposite films that combine highly conductive AuNPs with a large number of organic functional groups. Herein, Au-chitosan nanocomposites are successfully proposed as sensitive and selective electrochemical sensors for the determination of caffeic acid, an antioxidant that has recently attracted much attention because of its benefits to human health. A linear response was obtained over a wide range of concentration from 5.00 × 10(-8) M to 2.00 × 10(-3) M, and the limit of detection (LOD) was estimated to be 2.50 × 10(-8) M. Moreover, further analyses have demonstrated that a high selectivity toward caffeic acid can be achieved without interference from catechin or ascorbic acid (flavonoid and nonphenolic antioxidants, respectively). This novel synthesis approach and the high performances of Au-chitosan hybrid materials in the determination of caffeic acid open up new routes in the design of highly efficient sensors, which are of great interest for the analysis of complex matrices such as wine, soft drinks, and fruit beverages.

A series of four cobalt-based catalysts (two of which promoted with ruthenium) supported on SiO2 or SBA-15 were prepared and tested in the Fischer–Tropsch synthesis at industrially relevant process conditions (483 K, 20 bar, H2/CO ratio = 2.1, pellet size: 53–90 μm). The catalysts were characterized by N2-adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), H2-chemisorption and transmission electron microscopy (TEM). Ru as promoter enhanced the activity but not the selectivity to long-chain hydrocarbons ( $$ {\text{S}}_{{{\text{C}}_{ 5+ } }} $$ ). The $$ {\text{S}}_{{{\text{C}}_{ 5+ } }} $$ values of the SBA-supported catalysts were very low, especially at low conversion levels (i.e. low water partial pressure), suggesting that CO diffusion limitation increased the H2/CO ratio inside the 1-dimensional (1-D) porous network. A superimposition of the selectivity results on the correlations found in our recent study, derived for Co-based catalysts supported on γ-Al2O3, α-Al2O3 and TiO2 free from diffusion limitations, was made. While the SiO2-supported catalysts with a 3-D porous structure followed the correlations, the SBA-catalysts deviated significantly at low conversions, giving a further indication that the selectivity results of these catalysts were affected by CO diffusion limitations. Hence, it may be concluded that the kinetically significant diffusion distances (i.e. those long enough to cause an intrapore H2/CO ratio higher than that of the bulk gas phase) are probably much shorter for 1-D porous networks than for conventional 3-D supports. This is explained by a significantly lower effective diffusivity in 1-D porous networks. The potential of using the correlations between non-ASF distributed hydrocarbons and C5+, to give insight on the occurrence of diffusion limitations, was confirmed by superimposing data from the literature that were anticipated to be influenced by CO diffusion limitations.

Gold catalysts with loading 1 and 10 wt % were-prepared by deposition precipitation method with urea over mesoporous manganese oxide, obtained through a surfactant-assisted procedure by using cetyltrimethylammonium bromide (CTAB), followed by treatment with sulphuric acid. For comparison, Au(10 wt %) was also deposited over commercial CeO2 and SiO2 supports. The materials were characterized by XRD and EXAFS at the Mn K and Au L-III edges and XPS. Moreover, the analyses were performed on the samples treated under 1%CO/He, at 250 degrees C for 90 min. The structural and surface results of the as prepared manganese oxide confirmed the formation of gamma-MnO2 along with some amorphous Mn3O4 upon treatment of the precursor oxide with sulphuric acid. The CO treatment induces the formation of reduced phases, Mn3O4 (Hausmannite) and Mn2O3 (Bixbyite). Gold particles have a positive effect in promoting the reduction of manganese oxide and this effect is more pronounced in the Au(10 wt %) catalyst, which exhibits an enhanced CO oxidation activity with respect to both the Au(1 wt %) sample and the metal-free manganese oxide. The higher efficiency of Au(10 wt %) catalyst is attributed to a strong metal-support interaction between gold nanoparticles and support, as demonstrated by the presence of a component Au-O at 2.1 angstrom in the Fourier transform of the EXAFS signal of both the fresh and the CO-treated samples.