Design and optimization of new nanomaterials for the conservation of cultural heritage

Mención Internacional en el título de doctorEsta tesis contiene artículos de investigación en anexoThe degradation of the stone cultural heritage represents an irreversible loss; an issue that has become urgent since the increase of natural decay caused by climate change, the impact of atmospheric pollution and/or the current use of inappropriate treatments against stone weathering. Among different degradation processes, the loss of stone cohesion and the biodeterioration produced due to the biological colonization of stone heritage, are two of the most common issues that affect stone substrates. The present research work uses the application of nanotechnology to develop innovative strategies for improving these specific issues of crucial importance for the stone preservation. In this way, the research work consists of three main contributions: Firstly, the design, optimization and development of new nanomaterials based on brucite (Mg(OH)2) and portlandite (Ca(OH)2) nanoparticles (NPs) for the consolidation of carbonatic stones were treated. Pure Mg(OH)2, Ca(OH)2, and mixed formulations of Mg(OH)2 and Ca(OH)2 NPs were synthesized by hydrothermal method and sol-gel method. The changes in experimental parameters such as synthesis temperature, time reaction and/or precursor reactivity can determine the viability of a particular synthesis design. This is why firstly; studies of the optimal synthesis method and the influence of experimental parameters on the physico-chemical properties of the nanomaterials were carried out. After this, the application of these nanoparticles on carbonatic stones (dolostone, a sedimentary rock that contains high percentage of calcium and magnesium carbonate), widely used in the cultural heritage of Spain, was investigated. The selection of the type of nanoparticles according to the petrophysical properties and chemical composition of the stone substrate was achieved. In this sense, the designed inorganic nanomaterials based on brucite and portlandite NPs constituted stable products with enhanced chemical-physical affinities for natural stone. In the second part, the combination of the strong antimicrobial activity of ZnO, with the safe-to-use antimicrobial effectiveness and good compatibility of MgO with dolostone was taken as the starting point to develop new antifungal coatings highly compatible with the built-stone heritage. Thus, the photocatalytic and antifungal properties of Zn-doped MgO (Mg1-xZnxO) NPs obtained by sol-gel method, and their application as antifungal coatings for stone cultural heritage have been explored. The photocatalytic activity of the Zn-doped MgO NPs was comparatively studied with pure MgO and ZnO NPs. The antifungal activity was assessed against representative fungal species (Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans), which are especially active in the deterioration of stone heritage. The results showed that the development of a high surface defects content detected in the Zn-doped MgO nanoparticles changed its surface morphology, structural properties and defect density producing thus increased photocatalytic and antifungal effectiveness in comparison with pristine MgO and ZnO nanoparticles. The development of Zn-doped MgO nanoparticles by sol-gel synthesis method, with promising multifunctional photocatalytic and antifungal properties for carbonatic stone heritage was achieved. Finally, an additional research field was explored in the present research work with the use of different strategies to modify the cellulose surfaces and improve the interaction of adjacent fibers. The main results showed that Mg(OH)2 nanoparticles synthesized via hydrothermal method were successfully deposited onto pine cellulose fibers with different refining degrees and chemical compositions. These findings also showed for the first time that the physical and mechanical properties of the pine pulp fibers can be modified by the joint action of the presence of residual lignin and heteropolysaccharides in the pulp, the low consistency refining process and the application of brucite nanoparticles.La degradación del patrimonio cultural construido representa una pérdida irreversible. Este riesgo se ha convertido en un problema urgente gracias al incremento del propio deterioro natural de sus materiales constituyentes, causado por el cambio climático, el impacto de la contaminación atmosférica y/o el uso de tratamientos de conservación-restauración inadecuados. Entre los diferentes procesos de degradación, la pérdida de cohesión interna y el biodeterioro producido en el patrimonio cultural por su colonización por microorganismos, constituyen dos de los problemas más comunes que afectan a los sustratos pétreos. El presente trabajo de investigación lleva a cabo la aplicación de la nanotecnología para desarrollar estrategias innovadoras con el fin de aportar soluciones a estos problemas de importancia en la preservación del patrimonio cultural. De esta forma, la investigación ha dado lugar a tres principales contribuciones: Primeramente, el diseño, la optimización y el desarrollo de nuevos nanomateriales basados en nanopartículas de brucita (Mg(OH)2) y portlandita (Ca(OH)2) para la consolidación de rocas carbonatadas fue llevada a cabo. Así, nanopartículas de Mg(OH)2, Ca(OH)2 y formulaciones mixtas de Mg(OH)2 y Ca(OH)2 fueron sintetizadas mediante método hidrotermal y sol-gel. Los cambios en los parámetros experimentales tales como temperatura de síntesis, tiempo de reacción y/o reactividad de los materiales precursores representan un papel determinante en la viabilidad de un determinado diseño de síntesis. Por este motivo, el estudio del método de síntesis más óptimo, así como la influencia de los parámetros experimentales en las propiedades físico-químicas de los nanomateriales diseñados fue llevado a cabo. Posteriormente, se estudió la aplicación de estas nanopartículas como producto consolidante en dolomía. Esta roca sedimentaria, que contiene un alto porcentaje de carbonatos de calcio y magnesio, es de sumo interés dado que ha sido ampliamente utilizado en el patrimonio cultural de España. La selección del tipo de nanomaterial de acuerdo a las propiedades petrofísicas y la composición físico-química del sustrato pétreo fue alcanzado. De este modo, los nanomateriales inorgánicos diseñados basados en nanopartículas de brucita y portlandita constituyeron productos estables con mejorada afinidad físico-química con la piedra natural. La segunda parte de la presente investigación tomó como objetivo diseñar y desarrollar nuevos nanomateriales protectores antifúngicos altamente compatibles con el patrimonio pétreo. Para ello, se tomó como punto de partida la combinación de la actividad antimicrobiana del ZnO con la efectividad, baja toxicidad y buena compatibilidad del MgO con la dolomía. De esta forma, el estudio de las propiedades antifúngicas y fotocatalíticas de nanopartículas de MgO dopadas con Zn (Mg1-xZnxO) obtenidas mediante método sol-gel, además de su aplicación como capas protectoras antifúngicas para el patrimonio pétreo construido ha sido llevado a cabo. La actividad antifúngica ha sido estudiada frente a especies fúngicas representativas y especialmente activas en el deterioro del patrimonio pétreo (Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., y Pestalotiopsis maculans). Los principales resultados mostraron que el desarrollo de un alto contenido de defectos detectado en las nanopartículas de Mg1-xZnxO cambió su morfología superficial, propiedades estructurales y densidad de defectos produciendo así una incrementada actividad fotocatalítica y antifúngica, en comparación con las nanopartículas de MgO y ZnO. Así, el desarrollo de nanopartículas de Mg1-xZnxO mediante método sol-gel, con propiedades multifuncionales, tanto fotocatalíticas como antifúngicas, prometedoras para la preservación del patrimonio pétreo construido fue llevado a cabo. Finalmente, el presente trabajo exploró un campo adicional de investigación mediante el empleo de diferentes estrategias para modificar la superficie de celulosa y mejorar así, la interacción entre fibras adyacentes. Los principales resultados mostraron que las nanopartículas de Mg(OH)2 sintetizadas mediante método hidrotermal fueron satisfactoriamente depositadas en fibras de celulosa de pino con diferentes grados de refinamiento y composición química. Asimismo, estos resultados mostraron que las propiedades físico químicas y las propiedades mecánicas de las fibras de pulpa de pino pueden ser modificadas por la acción conjunta de la presencia de lignina residual y heteropolisacáridos, el proceso de refinamiento a baja consistencia y la aplicación de nanopartículas de brucita.Este trabajo no habría sido posible sin la financiación recibida por la Comunidad de Madrid y el Fondo Social Europeo a través de los programas GEOMATERIALES (2009/MAT-1585), GEOMATERIALES II (S2013/MIT-2914), CLIMORTEC (BIA2014-53911-R), ESTRUMAT (S2009/MAT-1585), MULTIMAT CHALLENGE (S2013/MIT-2862), así como al Grupo de Investigación de la Universidad Complutense de Madrid (UCM) Alteración y conservación de materiales pétreos del patrimonio (921349).Programa Oficial de Doctorado en Ciencia e Ingeniería de MaterialesPresidente: Mauro F. La Russa.- Secretario: Mª Asunción de los Ríos Murillo.- Vocal: Dusan K. Bozani

TEM-HRTEM study on the dehydration process of nanostructured Mg–Ca hydroxide into Mg–Ca oxide

The dehydration process from Mg0.97Ca0.03 (OH)2 nanoparticles (brucite type hexagonal structure) to Mg0.97Ca0.03O (periclase type cubic structure) was studied by Transmission Electron Microscopy (TEM-HRTEM), Electron Diffraction (SAED), Electron Energy Loss Spectroscopy (EELS) and image analysis. The transformation process was monitored in function of the reaction time applying 200 and 300 KV. Changes in porosity were possible to observe only during the irradiation with 200 KV. Depending on the irradiation time, the changes were gradual, producing an increase from the particle's edge towards the inner region. Different stages were observed, corresponding to the amount of water extracted from the particle, until finally a decrease in porosity and particle shrinkage occurs, coinciding with the formation of the Mg–Ca oxide. However, when samples were exposed to 300 KV, the dehydration process was much faster, and the pores structure was destroyed in a shorter time in comparison with lower doses of radiation. High resolution electron microscopy (HRTEM) applying 300 kV allowed identifying the progressive changes from brucite to periclase, including the formation of an intermediate dehydrated phase. The transformation along [0001]brucite and View the MathML sourcebrucite orientations was monitored determining differences in the kinetic of reaction related to the presence of point defects affecting the atomic lattice.This present research was funded by the Community of Madrid under the GEOMATERIALES 2 project (S2013/MIT-2914), by the Complutense University of Madrid’s Research Group: “The Alteration and Conservation of Stone Heritage” (921349), the Autonomous Region Program of Madrid, MULTIMAT-CHALLENGE (ref. S2013/MIT‐2862), the Innovation and Education Ministry ref. (MAT2013-47460-C5-5-P) and the Mat201019837/C06-05 projects.Peer reviewe

Ag&ZnO Obtained by Solvothermal Method for Photocatalytic Applications

In this work is reported the solvothermal synthesis of hybrid nanostructured ZnO&Ag systems starting from zinc nitrate hexahydrate (Zn(NO3)2•6H2O) and silver nitrate (Ag(NO3)2) as precursors. The structural and morphological properties of the obtained hybrid materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Subsequently, the photocatalytic behavior of prepared systems was evaluated. The results verify the viability of as-synthesized ZnO&Ag nanocomposites for its application in the removal of contaminants in water. The best results (percentage of pollutant removal > 99 %) are obtained for samples synthesized at low temperature, intermediate times, higher ratios Ag+/Zn2+ and in the presence of CTAB, which controls the final morphology of nanostructures and the dispersion thereof. These results prove that the system morphology is critical to the properties of the obtained material

Application of magnesium hydroxide nanocoatings on cellulose fibers with different refining degrees

Paper aging and protection are of crucial interest for improving the preservations of library collections and archives. Highly aging-resistant cellulose fiber sheets were obtained by treatment with magnesium hydroxide nanoparticles (Mg(OH)(2)). The procedure was tested on the sheets made of bleached (B) and refined unbleached (UB) pine cellulose fibers as well as their 50%/50% mixture (M). The mor and structural properties of the obtained sheets were studied by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) methods. Stress-strain, smoothness and pH measurements were employed to determine the changes in physical-chemical characteristics of the sheets after mixing two types of the fibers and subsequent treatment with Mg(OH)(2). It has been shown that the sheets made of the fiber mixture show a higher tensile index and smoothness. The modification with Mg(OH)(2) nanoparticles induces an increase in the pH of the sheets to slightly basic values (around pH 8), facilitates the inter-fiber bonding and additionally enhances the smoothness of the sheets. Finally, by exposing the sheets to thermo-hygrometric accelerated artificial ageing, it was found that the physical properties of the treated sheets were not significantly dependent on the environmental factors.This study was supported by the Geomaterials 2 Programme (S2013/MIT_2914),the Innovation and Education Ministry (ref. MAT2013-47460-C5-5-P) and the Autonomous Region Program of Madrid, MULTIMAT CHALLENGE (ref.S2013/MIT-2862

Synthesis and morpho-structural characterization of nanostructured magnesium hydroxide obtained by a hydrothermal method

Controlled magnesium hydroxide particles were successfully synthesized via a simple hydrothermal method. The influence of temperature and reaction time on the hydrothermal synthesis of Mg(OH)(2) was studied. The results provide new parameters to control the morphologies, particle sizes, agglomeration level and crystallographic structures of the brucite nanosized. The physic chemical properties of synthesized Mg(OH)(2) nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED), high resolution transmission electron microscopy (HR-TEM) and thermogravimetry/differential scanning calorimetry (TG/DSC). It has been shown that the prolongation of reaction time improves the crystalline degree of magnesium hydroxide particles. It was also possible to detect a relevant increase in the degree of crystallinity and a faster crystal growth with defined hexagonal morphologies in the samples obtained at higher temperature. Our results show that this simple hydrothermal route is highly interesting for the large scale production of these nanomaterials. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.This study has been supported by the Geomaterials Programme (S2009/MAT-1629) and the ESTRUMAT Programme (S2009/MAT-1585) and it has been carried out in the Department of Materials Science and Engineering and Chemical Engineering of the University Carlos III of Madrid, Spain. The authors are grateful to the National Center for Electron Microscopy (CNME) for its support with TEM

Atomic scale study of the dehydration/structural transformation in micro and nanostructured brucite (Mg(OH)(2)) particles: Influence of the hydrothermal synthesis conditions

Micro and nanostructured brucite (Mg(OH2)) particles synthesized by hydrothermal method from solutions with high content of hydrazine (0.14 M) and nitrate (0.24 g) were compared with samples obtained from low hydrazine content (0.0002 M) and nitrate (0.12 g). The samples were heated at 180 degrees C for 4 h, 6 h and 12 h. XRD, TEM-HRTEM, SAED and image analysis techniques were used for the morphological and structural characterization. The effect of electron beam irradiation on the brucite dehydration was observed in atomic resolution images at 300 kV. Hexagonal crystals show differences in crystallinity, strains and kinetic of reaction. High hydrazine/nitrate samples have slightly larger crystals with better crystallinity, showing a strong preferential orientation. Rietveld refinements show how unit cell parameters are bigger in samples obtained with higher hydrazine/nitrate content, confirming also the preferential orientation along the 0001 plane. Differences in the dehydration process show the rapid formation of a porous surface, the amorphised cortex or the presence of highly oriented strains in samples prepared from higher hydrazine/nitrate content. Conversely, crystals slightly smaller with randomly scattered defect surfaces showing the Mg(OH)(2)/MgO interphase in samples prepared with low hydrazine/nitrate content. Significant differences in the kinetic of reaction indicate how the dehydration process is faster in samples prepared with high hydrazine/nitrate content. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.This present research was funded by the Community of Madrid under the GEOMATERIALES II project (S2013/MIT-2914), by the Complutense University of Madrid’s Research Group: “The alteration and conservation of stone heritage” (921349), the Autonomous Region Program of Madrid, MULTIMAT-CHALLENGE (ref. S2013/MIT‐2862), the Innovation and Education Ministry ref. (MAT2013-47460-C5-5-P), the Mat201019837/C06-05 and the Ministry of Education, Science and Technological Development of Serbia (OI 1612046) projects. The authors are indebted to the Petrophysical Laboratory IGEO, affiliated with the Moncloa Campus of International Excellence CEI-09-009(UCM-UPM), the Heritage Laboratory Network in Science and Technology for Heritage Conservation (RedLabPat,) and the Materials Science Department (Carlos III University of Madrid)

Effect of temperature and reaction time of the synthesis of nanocrystalline brucite

Mg(OH)2 nanoparticles has been successfully synthesized by means of the hydrothermal method. The effect of the reaction time and the synthesis temperature on the nanoparticles obtained has also been studied. The physic-chemical properties of the synthesized brucite samples have been characterized by X-Ray-diffraction (XRD), scanning electron microscopy/energy dispersive X-rays analysis (SEM/EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetry/ differential scanning Calorimetry (TG-DSC) and in situ high-temperature X-ray diffraction (XRD). The influence of the synthesis parameters in the brucite samples has been discussed in detail. Furthermore, it has been shown that the increase of temperature from 180 to 200ºC improves the crystallinity degree of Mg(OH)2 nanostructured particles and also, promotes the formation of plates with bigger uniform size. As well, the increase in the time reaction induces the formation of bigger size brucite plates. So, this hydrothermal method has been shown to be a really promising method for the large scale production.Peer Reviewe

Nuevos avances en el diseño de nanomateriales para la consolidación del patrimonio pétreo: evaluación de su efectividad en la dolomía de Laspra

Actas del Congreso Nacional "Estudio y Conservación del Patrimonio Cultural". Málaga, 16-19 de noviembre de 2015La piedra constituye el principal representante del patrimonio arquitectónico, estando la caliza yla dolomía entre los materiales más empleados a lo largo de la historia. El deterioro que sufren estosmateriales genera una importante pérdida de cohesión interna que hace necesaria la aplicación deproductos consolidantes. No obstante, en muchos de los casos estos productos son inadecuados yprovocan importantes procesos de deterioro, constituyendo uno de los principales factores de degradacióndel patrimonio. En este contexto, el desarrollo de los nanomateriales constituye una importante vía deactuación en la conservación del patrimonio cultural. La manipulación de los materiales a escalananométrica permite el menor trastorno posible a la obra original, mientras que de manera eficiente luchacontra los efectos del tiempo y el medio ambiente. Así, la aplicación de la nanotecnología a la ciencia dela conservación del patrimonio supone un importante avance que puede resolver muchos de los problemasencontrados en las intervenciones tradicionales de consolidación. Uno de los requisitos más importantespara el uso de estos productos en el patrimonio pétreo es la compatibilidad física y química con el sustratopétreo a tratar. Por esta razón, la presente investigación se basa en el diseño y el estudio de estabilidad deun nuevo producto consolidante, basado en nanopartículas de hidróxido de magnesio (brucita) con el finde consolidar y proteger los sustratos de carbonato de calcio-magnesio.Programas Geomateriales 2 (S2013/MIT-2914) y MultimatChallenge (S2013/MIT-2862

Structural, optical and electrical properties of SnO2 and SnO2:F films deposited by ultrasonic spray pyrolysis

In this research, we report the preparation and characterization of SnO2thin films preparation by the Ultrasonic Spray Pyrolysis technique using different fluorine content dissolved in ethanol as precursor solution, for its possible application as TCO's. The structural, optical and electric properties of synthesized SnO2:F films have been characterized by X-ray Diffraction (XRD), Profilometer, UV - Vis-NIR spectroscopy and electrical measurements by Hall Effect. Also structural changes were studied by X-ray diffraction. The main results show that the electrical resistivity of the films decreased with the fluorine content. The best electro-optical properties (electrical resistivity of 4.14x10-4O-cm and average transmittance of 80 [%]) were achieved in a fluorine content in relative with tin of about 0.52. Furthermore, a systematic change was observed in the intensity of the lines of the diffraction maxima of X-rays in function of fluorine content. ©Sociedad Mexicana de Ciencia y Tecnología de Superficies y Materiales.En esta investigación, reportamos la preparación y caracterización de películas delgadas de SnO2 preparadas por la técnica de Rocío Pirolítico Ultrasónico con diferente contenido de flúor disuelto en etanol como solución precursora, para su posible aplicación como TCO´s. Las propiedades estructurales, ópticas y eléctricas de películas SnO2:F sintetizadas se caracterizaron mediante Difracción de Rayos-X (DRX), Perfilometria, Espectroscopia UV-Vis-NIR y mediciones eléctricas por Efecto Hall. Asimismo los cambios estructurales se estudiaron mediante Difracción de Rayos-X. Los principales resultados muestran que la resistividad eléctrica de las películas disminuyó con el contenido de flúor. Las mejores propiedades electro-ópticas (resistividad eléctrica de 4.14x10-4 Ω-cm y transmitancia media de 80 %) se alcanzaron en un contenido de flúor con relación de estaño de aproximadamente 0.52. Además, se observó un cambio sistemático en la intensidad de las líneas de los máximos de difracción de rayos-X en función del contenido de flúor

Seguridad de la ivermectina: toxicidad y reacciones adversas en diversas especies de mamíferos

La ivermectina es un fármaco antiparasitario muy utilizado en Medicina Veterinaria, dado su espectro de actividad que abarca tanto endo como ectoparásitos, elevada eficacia y amplio margen de seguridad. No obstante, su administración puede dar lugar a efectos tóxicos. La mayoría de ellos derivan de la sobredosificación del compuesto, aunque también se han descrito, a dosis terapéuticas, casos de susceptibilidad extrema a los efectos neurotóxicos del fármaco en determinadas razas o subpoblaciones de animales, así como reacciones anafilácticas por la destrucción masiva de parásitos