The knowledge of the ways in which post-synthesis treatments may influence the properties of carbon quantum dots (CDs) is of paramount importance for their employment in biosensors. It enables the definition of the mechanism of sensing, which is essential for the application of the suited design strategy of the device. In the present work, we studied the ways in which post-synthesis thermal treatments influence the optical and electrochemical properties of Nitrogen-doped CDs (N-CDs). Blue-emitting, N-CDs for application in biosensors were synthesized through the hydrothermal route, starting from citric acid and urea as bio-synthesizable and low-cost precursors. The CDs samples were thermally post-treated and then characterized through a combination of spectroscopic, structural, and electrochemical techniques. We observed that the post-synthesis thermal treatments show an oxidative effect on CDs graphitic N-atoms. They cause their partially oxidation with the formation of mixed valence state systems, [CDs]0+, which could be further oxidized into the graphitic N-oxide forms. We also observed that thermal treatments cause the decomposition of the CDs external ammonium ions into ammonia and protons, which protonate their pyridinic N-atoms. Photoluminescence (PL) emission is quenched.

The mechanism, the effectiveness, and the potential damage during limewash removal from wall painting models were evaluated for agar gels and water-based pads constituted by Arbocel BWW 40 cellulosic fibre. Cleaning materials in different formulations were compared: pure and with additives (ethylenediaminetetraacetic acid, EDTA, and ammonium citrate tribasic, TAC) in different percentages (2% and 3%). The cleaning action was evaluated on laboratory model samples, prepared with hematite a fresco and an egg-based tempera with limewash overlayers. Calcium and iron extracted by cleaning materials were quantified by inductively coupled plasma-mass spectrometry (ICP-MS). The potential damage to the hematite painting layers was also studied by electron paramagnetic resonance (EPR) spectroscopy. A visual observation of the limewash detachment induced by the overall cleaning was also performed. Results suggest that limewash removal mainly occurs by aqueous solution release from the cleaning system, with subsequent layer wetting, probable layer swelling, weakening and complete or partial detachment. A stronger limewash adhesion on the hydrophilic fresco surface than on tempera, was observed. None of the used cleaning materials resulted harmful to the integrity of the hematite layer underneath the limewash. A small damage in terms of extracted iron was detected in the cleaning systems after direct contact with fresco and tempera hematite layers; a "protective" effect by the tempera layer was observed for the pigment, due to the organic binder and triggered by the hydrophobic content of the egg-based medium. Cleaning materials with additives are more harmful than pure materials, with a greater coordinating ability for EDTA than for TAC, which increases with chelator percentage. Data suggest a more efficient backward transportation of aqueous solutions containing calcium and iron ions towards gels with respect to cellulose, due to their smallest pore size. All these results lead to operative suggestions: for fresco painting layers, pure gel allows both a good limewash removal and a lack of damage on the hematite layers. Instead, for tempera layers a good limewash removal and a negligible damage on the pigment was shown by gel, both pure and additivated with TAC, and pure cellulose. Therefore, the present study allows to identify proper characterization methods for evaluating effectiveness and damage in limewash removal and to give useful suggestions for the planning of repeated cleaning operations on a real polychrome object.

In this study, the microstructure of mock-up mortar specimens for a historic environment, composed of different mixtures, was studied using mercury intrusion porosity (MIP) and micro-computed tomography (µCT), highlighting the advantages and drawbacks of both techniques. Po-rosity, sphericity, and pores size distribution were studied, evaluating changes according to mortar composition (aerial and hydraulic binders, quartz sand, and crushed limestone aggregate). The µCT results were rendered using 3D visualization software, which provides complementary information for the interpretation of the data obtained using 3D data-analysis software. Moreover, µCT contrib-utes to the interpretation of MIP results of mortars. On the other hand, MIP showed significant ink-bottle effects in lime and cement mortars samples that should be taken into account when interpret-ing the results. Moreover, the MIP results highlighted how gypsum mortar samples display a porosity distribution that is best studied using this technique. This multi-analytical approach provides important insights into the interpretation of the porosimetric data obtained. This is crucial in the characterization of mortars and provides key information for the study of building materials and cultural heritage conservation.

Copper complexes with different ligands (ethylenediaminetetraacetic acid, EDTA, ammonium citrate tribasic, TAC, and alanine, ALA) were studied in aqueous solutions and hydrogels with the aim of setting the optimal conditions for copper stain removal from marble by agar gels, with damage minimization. The stoichiometry and stability of copper complexes were monitored by ultraviolet-visible (UV-Vis) spectroscopy and the symmetry of Cu(II) centers in the different gel formulations was studied by electron paramagnetic resonance (EPR) spectroscopy. Cleaning effectiveness in optimized conditions was verified on marble laboratory specimens through color variations and by determining copper on gels by inductively coupled plasma-mass spectrometry (ICP-MS). Two copper complexes with TAC were identified, one having the known stoichiometry 1:1, and the other 1:2, Cu(TAC)2, never observed before. The stability of all the complexes at different pH was observed to increase with pH. At pH 10.0, the gel's effectiveness in removing copper salts from marble was the highest in the presence of ALA, followed by EDTA, TAC, and pure agar gel. Limited damage to the marble surface was observed when gels with added EDTA and TAC were employed, whereas agar gel with ALA was determined to be the most efficient and safe cleaning material.

The paper investigates the use of di-ammonium hydrogen phosphate (DAP) as a possible consolidation treatment for lime-based mortars. Different DAP concentrations are proposed, additional post-treatment limewater application is used on some specimens. The results of application were evaluated in terms of mechanical property modification (dynamic elastic modulus, weight loss due to the peeling test), penetration depth, consolidant's distribution, colour change and water transport properties. Newly-precipitated phosphate-based phases were detected after the treatment and the relation towards treatment modality (i.e. DAP solution molarity and further limewater application) was evaluated. In the case of mechanical improvement, the outcomes indicate that a phosphate-based treatment is highly promising for mortar consolidation. Some non-negligible colour change was detected as a result of DAP application.

The present paper investigates the effectiveness of di-ammonium hydrogen phosphate (DAP) as a con- solidation treatment for artificially weathered lime-based mortars. Laboratory prepared samples were exposed to repeated freeze-thaw cycles and then subjected to 2.0 M DAP solution via 24 h poultice. The microstructural variations due to freeze-thaw cycles and the effects induced by the subsequent DAP consolidation were assessed with the use of a multi-analytical approach combining optical observations, weight variations, dynamic elastic modulus change and peeling test outcomes. The results indicate that DAP treatment significantly restored the weathered mortars in terms of physical and cohesive properties. The correlation between the weight loss and surface degradation by the peeling test examination was projected. The new properties of weathered and consolidated mortars are critically discussed with an eye on their expected behaviour in the field of Built Heritage conservation. Lastly, as a chief outcome of this study, a novel protocol for the evaluation of surface cohesion through peeling tests combined with image analysis is proposed.

The knowledge of how the different types of nitrogen centers affect the electrochemical and optical prop- erties of Nitrogen-doped carbon quantum dots (N-CDs) is of paramount importance in the design and synthesis of these nanostructures. In fact, from the knowledge of the redox centers of N-CDs it is possi- ble tune their energetic levels in order to realize the suitable matches for the design of opto-electronic, photovoltaic or catalytic devices. Herein we present a study of the electrochemical and the optical re- sponses of N-CDs, obtained by hydrothermal method from citric acid and urea. The main issue is to investigate the role played by the specific nitrogen centers in their redox processes. From the voltam- metric responses we showed that the observed oxidation processes of N-CDs involve their graphitic and pyrrolic N-atoms, respectively, while the reduction process regards their protonated pyridinic N-atoms. Then, from spectro-electrochemical determinations, we explained that the oxidation of the graphitic N- atoms is a two electron process that gives an N -oxide form through the reaction with a molecule of water and the loss of two protons. Finally we discussed the observed pH-dependence of both the optical and the electrochemical responses of our N-CDs to explain the role played by their pyridinic N-atoms.

Iniziativa social di Istitito #ISPConAIR effettuato nei giorni 25 - 26 febbraio 2021 sulla piattaforma zoom. Attualmente riproducibile sul canale YouTube https://www.youtube.com/playlist?list=PLSNWzD2-V2ve_F1siwE_y5oaRIiERYe6V 25 febbraio 2021 Bonsanti - SCIENZA E CONSERVAZIONE: TESTIMONIANZE E VALUTAZIONI Sansonetti - LA RICERCA SCIENTIFICA E LA PULITURA DEI MONUMENTI Possenti, Colombo - PRODOTTI INORGANICI MINERALI PER LA CONSERVAZIONE DEI MATERIALI LAPIDEI CARBONATICI Sacchi - IL TRATTAMENTO FINALE DEL PIANO DI CONSERVAZIONE DELLE SUPERFICI: LA PROTEZIONE Calia - COATINGS NANOSTRUTTURATI CON FUNZIONE AUTOPULENTE PER LA PROTEZIONEDELLESUPERFICI STORICO-ARCHITETTONICHE IN AMBIENTE URBANO Cantisani - LE MALTE ANTICHE: DALLA CONOSCENZA ALLA COMPATIBILITÀ NEL RESTAURO. Della Torre - LA CONSERVAZIONE PROGRAMMATA Quarta, De Benedetto - STUDIO DELLE PRATICHE CONSERVATIVE DEL PASSATOMEDIANTETECNICHE MICROSCOPICHE INTEGRATE E METODOLOGIE FT-IR, GC-MS E Py-GC-MS Festa - LA RICERCA SCIENTIFICA APPLICATA: IL PUNTO DI VISTA DEL RESTAURATORE. TRE CASI STUDIO SU CONSOLIDAMENTO, PROTEZIONE E PREVENZIONE DEL BIODETERIORAMENTO DEI MATERIALI LAPIDEI

The effectiveness of Agar gels for copper stain removal from marble surfaces was systematically studied. Gels with different agar concentrations (1, 3, 5%) and different chelating agents used as additives (ethylenediaminetetraacetic acid, EDTA, and ammonium citrate tribasic, TAC) were tested on laboratory marble specimens for different contact times (30 and 60 min). For better characterization, hydrogels were lyophilised and cryogels were obtained. Systematic comparison of different formulations was feasible on cryogels and performed in terms of: (i) the morphological properties, by field-emission scanning electron microscopy (FE-SEM); (ii) the type of Cu(II)-complexes formed and their quantitative comparison by electron paramagnetic resonance (EPR) spectroscopy; (iii) the total amount of copper removed from marble surfaces, by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). AgarArt 1% with TAC exhibited the highest effectiveness for copper stain removal after 60 min contact (431 ?g/cm2). Such a good cleaning effectiveness can be ascribed to the co-presence of the following properties: efficient metal coordination, which is related to the additive presence, and favourable gel morphology, related both to the gel concentration and to the additive type. In fact, it was observed that both the low gel concentration and the presence of TAC are related to a narrow pore size distribution in gels, besides the possibility of copper coordination. The presence of EDTA results in a broader pore size distribution and in a lower gel strength, with respect to gels with TAC. Thus, a new procedure for studying gels was proposed, which allows to optimize the conditions for metal stain removal from built heritage.

L'articolo esamina la situazione attuale della normativa nazionale nel campo dei beni culturali.

This paper presents the study of four gypsum mixtures, focusing on the role of both inorganic and organic additives and on the micro-structural features and mechanical properties. Additives have been chosen among those most reported in historical recipes, for example magnesia, lime putty, rabbit glue. The selected mixes refer to gypsum-based materials used in artworks manufacture, such as plasters, mouldings, stuccoworks, pastiglia. Blank reference materials were prepared on purpose according to the specific recipe, in order to verify the final composition and to highlight the hardening mechanisms and the formation of setting compounds. The chemical composition was related to workability properties and final mechanical resistance and the action of additives as retardants was studied with interesting results. For instance, MgO imparts good properties to the mechanical features, especially with regard to the compressive strength characteristics.

The last conservation works at Milan Ca' Granda building, formerly hosting an hospital designed by Filarete, is proposed as a model to conceive a knowledge plan on architectural brick and terracotta surfaces. Conservation works were carried out in between 2008-2012, planning a characterization analytical campaign followed by an in situ evaluation of limits and benefits of conservation treatments. The ceramic substrates have been characterized in their main components; the state of conservation of the ceramic elements has been studied and several decay patterns have been individuated such as exfoliation, pulverization and scaling. Red finishes have been detected on the ceramic substrate. Their composition is different, basing on gypsum and lead white respectively, both pigmented with red ochre. Both of them are of extreme interest in reconstructing some elements of the building conservation history: for this main reason the cleaning approach ought to safeguard those residues of red finishes presents on the surface. Nd:YAG laser source proved to be fruitful at this aim. Moreover some conservation products, including both surface consolidants and water repellent treatments, have been evaluated. The study could be assumed as a overall knowledge model to serve as an example in approaching the conservation works of an important monument faced with brick and terracotta tiles.

During the 18th century architecture in Naples reached an extremely balanced synthesis between architectural spatiality and decorative apparatuses representing the most successful example of local inventiveness over history. Quite an impressive case dating back to that period is represented by the "Gabinetto of gilded stucco" in the Royal Palace in Portici. Located in the area of the palace known as Caramanico - from the name of the owner of the pre-existing building incorporated in the palace - the stucco was molded between 1752 and 1753 by the two stucco workers Angelo la Sala and Gennaro Bruscino, who also decorated the "Salotto di Porcellana" in Chinese style. Today the room, used as an academic department, is affected by quite a serious stucco decay majorly due to negligence and humidity and consisting in efflorescence, powdering and bursting, worsened by the corrosion of metal fixings. However, the present-day state of conservation of these stuccoworks represents a unique opportunity to carefully observe the original technique used to make such artworks at that time. Therefore by means of advanced surveying instruments and multi-analytical material characterization together with archival documents, the present research - set up in collaboration between University of Naples, Politecnico di Milano and CNR - aims at elaborating a thorough knowledge of an emblematic case of 18th century Neapolitan stucco with a view to its future conservation.

The paper presents the analytical campaign carried out on the Baroque stucco decorations by Italian artists known as Artists of the Lakes. Forty samples (from moldings, background, sculpture bas- and high- reliefs) from the churches of S. Lorenzo in Laino, S. Maria dei Ghirli in Campione d'Italia and S. Maria Assunta in Puria (Como, Italy) were analysed by chemical and mineralogical techniques and the data were discussed with a multi-disciplinary approach with art historians, in order to enlighten and compare the artistic techniques. Binders, aggregates, pigments and organic fractions were determined using optical microscopy, scanning electron microscopy with EDS microprobe, X-ray powder diffraction, Raman and Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry. The substrate is constituted by a mixture of magnesian lime, silicatic and/or carbonatic aggregate. Layers sequence varies from the simple pattern of S. Maria dei Ghirli, (1 or 2 layers), to the complexity of S. Lorenzo where up to 9 layers above the substrate were observed. Pigment particles were identified as ochres and as green earth in a single case. Three different gilding techniques are described, as the gold leaf is applied over a chrome yellow ground (a missione), over a layer composed by ochre and lead white or over a brass leaf. In some cases organic materials were recognized: oil in gilding preparations and egg mixed with ochre pigments. A carbon black based pigment was identified by Raman spectroscopy in some decorative motifs. The sequence and composition of the finishing layers, the accumulation of particulate matter and the use of gypsum on purpose depending on the decorations typology, enlightened the artist skills, showing how different needs and timing influenced the commissions in the buildings.

Cleaning an artwork is an extremely delicate and irreversible procedure in a conservation work. Art conservators constantly work to identify an appropriate and correct cleaning methods according to the requirements of different substrates and in order to solve different removal problems. In recent years, gels positively responded to the conservation requests becoming a valid help and, in several cases, the best alternative compared to traditional cleaning methods. This paper proposes a summary of the most recent results regarding agar gels and their applications in cleaning art surfaces; moreover, specific applications of agar gels formulated on purpose to address different conservation problems are also discussed. (C) 2020 Elsevier Masson SAS. All rights reserved.

Ancient rock reliefs in the necropolis of Naqsh-e Rustam are important testimonies of the development of an outstanding monumental art over the centuries, in close relationship with their natural context. The rock reliefs underwent natural and anthropic decay processes in the course of time, which caused dramatic changes affecting their aspect, leading to the loss of fragments and in some cases to severe structural instability. This paper focuses on the oldest group of rock reliefs, dating back to the Achaemenian period; due to their location on the top of a sloping cliff, they are less accessible and more challenging by a conservation point of view. The reliefs have been studied in field and by means of a multi-analytical laboratory procedure, in order to identify the decay patterns, along with an assessment of the state of conservation. In order to frame the problem in a proper historical context, archival material including photographs, drawings and descriptions - created on purpose by western scholars between the 17th and the 20th century - are also analyzed focusing on any indications as regards deterioration problems. Fragments were sampled from the upper bed rock, from layered formations, surface deposits, and from areas with biological growth. They were studied by means of optical microscopy, SEM-EDX and XRD analyses. The results show that the main decay features could be classified as Concretion, Deposit, Bio-film, Detachment, Crust, Oxalate film and Cracks. Among the main decay causes and mechanisms, the chemical dissolution of the stone substrate and the heavy microbiological subsurface growth play a major role. The layered aluminosilicate encrustations imply a continuous exposure of the limestone monument to the moisture ingress from the outer environment. Also, indications of the recent impact of atmospheric pollutants were observed, which is noteworthy, considering the distance of the monument from the urban areas.

A nymphaeum is a specially designed place - inside an Italianate garden, or in connection with it (artificial grotto) - to amaze. Artifice and constructive expertise are the things that characterize these pieces of architecture, rich in fountains, mosaics, waterworks, statues, murales, stuccos, works of art and automas; originally real Wunderkammern evidence of the culture of the time. However, in Lombardy (Northern Italy) many nymphaea located in private suburban villas are still unknown. This paper presents a wide overview, with the aim of listing grottoes and nymphaea around Lombardy and then classifying the stones used in the decorative mosaics, taking into account the lack of specific studies in this field. Through the 25 works found by census that go from the XVI to the XX century, the history, the stylistic and technique evolution of grottos and nymphaea in Lombardy is recreated. Thanks to the identification of the types of stones used in every garden and to the qualitative analysis of their diffusion, this study paves the way for considerations on the supply of the extraordinary variety of the Lombard stone materials over the centuries. The survey has the goal to promote a Catalogue of the materials used in the mosaics of artificial grottoes and nymphaea in Lombardy - provided with their damage pattern - with the aim of build up a knowledge tool to be used in next conservation and restoration works; accompanied by an online map aimed at interactive valorization

Hydration and dehydration processes constitute a crucial issue for the conservation of sandstones, where a certain amount of swelling clays is present. Very often flaking and micro-detaching are produced, when this mechanism act on sandstones. Nevertheless, the topic is quite neglected in recent literature. In order to prevent the clay swelling, hydrophobic treatments are usually applied. A comparative assessment among several products on decayed surfaces is carried out in this study. In particular, different combination between consolidants (CONSOLIDANTE DN - ethyl silicate; and VP 5035 - modified ethyl silicate, both by Chem Spec) and water-repellent products (Fluoline HY by CTS Europe - fluoroelastomer - and BSM40SKY - alkyl silane - by Chem Spec), with and without anti-swelling product (AntiHygro - Remmers) were tested in laboratory and in situ at the St.Prospero Tower in Reggio Emilia (Italy). The tower, currently under restoration because of a severe damage due to exfoliation, scaling and detaching, is constituted by sandstones quarried on the Apennines (Monte Cassio, Ranzano and Pantano). The laboratory tests were carried out on the same sandstone materials, sized on purpose. Ultra close-range photogrammetry technique was utilized to evaluate the effects of the anti-swelling product, both in laboratory and in situ on selected areas with different state of conservation and exposition. The monitoring of treated surfaces, with respect to the non-treated areas, was performed in order to evaluate variations of the surface morphology over time. The assessment of the products effectiveness was completed by colorimetric analyses, water absorption tests (capillarity and contact sponge method), static angle measurements and water vapour permeability tests

The present paper regards about the laser cleaning intervention on three plaster casts, the Flora Farnese, the Pallade di Velletri and the Fauno Barberini, in the framework of the pilot restoration for the conservation of the Plaster Casts Collection of the Brera Academy of Fine Arts. The three artefacts were objects of a severe decay that altered the plaster casts integrity and impeded a correct lecture of the surface. Before using the laser tecnology, preliminary wet and agar gel cleaning were carried out. This metodology didn't allow a complete deposits removal; in fact unwanted particles were partially penetrated in the gypsum matrix porosity and the traditional methods did not allow to eliminate the grey layer visible on the artefacts. Hence a Nd:YAG system operating in QS mode, was used as an alternative metodology. Several laser cleaning tests were carried out on plaster casts surface and instrumental analysis were carried out to evaluate the laser effects. Laser cleaning was completed at 532 nm wavelength. The possibility to calibrate continuously the operating parameters permitted to ensure selectivity, gradual cleaning and safety conditions needed to reach the desired cleaning level. The laser system allowed the treatment of a sensible, porous material like gypsum is, respecting at the best the surface morphology.

The cleaning of plasterworks could be often complicated by the presence of surface materials, originating from molding and patinas. Lasers allow dry cleaning with high selectivity, but guidelines for the cleaning of plasterworks finished with intentional patinations are unavailable. A set of tests was conducted to identify the range to perform a correct laser cleaning on plaster model samples patinated with beeswax, de-waxed shellac, Arabic gum and boiled linseed oil, using three laser systems: Nd: YAG devices at 1064 nm and 532 nm, both in Q-Switch, and a Er: YAG at 2940 nm, starting with the smallest values of fluence and repetition rate. The effects of laser cleaning on model samples were evaluated with colorimetric, gloss, contact angle measures and stereo-microscopic observations; considering the results obtained, damage was identified on the patina and/or on the plaster substrate with the Er: YAG system, starting at a minimum of 0.50 J/cm2 and a repetition rate of 1 Hz, with the exception of the shellac treatment, which showed neither morphological or optical variations, up to the fluence of 1.25 J/cm2 with repetition rate to 5 Hz. The shellac had variations in color with the Nd: YAG at 1064 nm @ 0.79 J/cm2 and a 2 Hz; no chromatic variations resulted for the remaining three patinas in the range of fluences tested, with values between 0.31 J/cm2 and 1.1 J/cm2, with repetition rate up to 3 Hz. No effects were detected when cleaning with the Nd: YAG at 532 nm, which was effective to 2.4 J/cm2 with increasing repetition rate, up to a maximum of 2 Hz.