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In this work, low-Pt content nanocatalysts (≈ 5 wt. %) supported on Hollow Carbon Spheres (HCS) were synthesized by two routes: i) colloidal conventional polyol, and ii) surfactant-free Bromide Anion Exchange (BAE). The nanocatalysts were labelled as Pt/HCS-P and Pt/HCS-B for polyol and BAE, respectively. The physicochemical characterization of the nanocatalysts showed that by following both methods, a good control of chemical composition was achieved, obtaining in addition well dispersed nanoparticles of less than 3 nm TEM average particle size (d) on the HCS. Pt/HCS-B contained more Pt0 species than Pt/HCS-P, an effect of the synthesis method. In addition, the structure of the HCS remains more ordered after BAE synthesis, compared to polyol. Regarding the catalytic activity for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH, Pt/HCS-P and Pt/HCS-B showed a similar performance in terms of current density (j) at 0.9 V vs. RHE than the benchmark commercial 20 wt. % Pt/C. However, Pt/HCS-P and Pt/HCS-B demonstrated a 6 and 5-fold increase in mass catalytic activity compared to Pt/C, respectively. A positive effect of the high specific surface area of the HCS and its interactions with metal nanoparticles and electrolyte, which promoted the mass transfer, increased the performance of Pt/HCS-P and Pt/HCS-B. The high catalytic activity showed by Pt/HCS-B and Pt/HCS-P for the ORR, even with a low-Pt content, make them promising cathode nanocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC).

This work reports the synthesis and characterization of metal-free electrocatalysts made from Brosimum alicastrum waste as the carbon source. The residues were washed and grounded to a fine powder. The thermogravimetric analysis carried out on the raw sample showed that the optimal synthesis temperature is 700 °C. Thus, the raw sample was pyrolyzed at 700 °C and activated with potassium hydroxide (KOH) in a 2:1 ratio (KOH/fine power) to improve its properties. Afterwards, hydrazine was used as the nitrogen source for doping. The physicochemical characteristics of pyrolyzed, activated, and doped carbons were studied and their electrochemical properties were determined using cyclic and linear voltammetry techniques. The electrochemical measurements indicate that the sample doped at 140 °C has an acceptable onset potential (0.854 V vs. RHE), while the one doped at 160 °C shows the highest current density among the synthesized electrocatalysts (2.61 mA cm-2). Although the catalyst performance is lower compared to commercial 20% Pt/C, this biomass precursor favors the oxygen reduction reaction in alkaline media.

In the search of insight concerning the interaction of molecules of different complexity with the desulfurization and hydrogenation sites, a series of NiMo sulfided catalysts with active particles of different morphology were tested in the hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and in the hydrogenation of naphthalene and cyclohexene. The size and stacking of the NiMoS nanoparticles were modified both by increasing the Mo loading and by decreasing the metal-support interaction. The results show that not all the hydrogenation reactions take place at the same type of site, and that the hydrogenating sites at the top basal plane have greater hydrogenating power than those at the edge. The direct desulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene takes place at coordinatively unsaturated sites (CUS), whereas for the hydrogenation-desulfurization reaction route, the site where the rate controlling step takes place is influenced by the structure and reactivity of the reacting molecule. For dibenzothiophene, the rate controlling step takes place at hydrogenating sites at the top basal plane while for 4,6-dimethyldibenzothiophene it takes place at CUS. Therefore, to efficiently eliminate sulfur from molecules like 4,6-dimethyldibenzothiophene, as required in ultra-low sulfur fuels, the catalyst must have good hydrogenating capacity but more importantly, a high number of CUS.

Biodegradable films based on agar with glycerol (GLY) as a plasticizer were developed by incorporating hydroalcoholic garlic extract (HGE) on the film surface. The effect of GLY content (0, 15, or 30 wt%) and different concentrations of HGE (0, 0.5, 1, or 1.5 μg/mL) on the physicochemical and transport properties of the films was evaluated. The optical (color and transparency), mechanical (tensile test), transport (diffusion and water vapor transmission rate), thermal (thermogravimetric analysis) structural (infrared spectroscopy and X-ray diffraction), and morphological (scanning electron microscope) properties were analyzed. The impregnation of HGE increased the transparency values and decreased the luminosity, tensile strength, elastic modulus, and crystallinity of the agar films. The formulation of 30 wt% GLY with 1.5 μg/mL HGE, identified as 30 GLY [1.5], showed a similar thermal stability that of a neat agar film. The agar films with 30 wt% GLY showed the lowest diffusion coefficient and water vapor transmission rate, indicating that volatile compounds are slowly released. From the results the formulation 30 GLY [1.5] could be used as a film to transport and to release HGE which is supported by a biodegradable matrix and this system has a potential use as insect semiochemical for plague control.

An extensive range of spinel-like solid solutions was found in the system Zn7Sb2O12–Li3Zn3Sb3O12 with general formula Li3xZn7-4xSb2+xO12: 0.25 ≤ x ≤ 0.65. These solid solutions are isostructural with the spinel α-Zn7Sb2O12. The Li3Zn3Sb3O12 (LiZnSbO4) end-member shows two polymorphic forms: high-temperature α-Li3Zn3Sb3O12 with an orthorhombic cell and low-temperature β-Li3Zn3Sb3O12 with a monoclinic cell. These polymorphs show a reversible transformation at 1275 ± 25 °C. The α-Li3Zn3Sb3O12 was also prepared as a metastable phase by direct synthesis at low temperatures, 900 °C. The sub-solidus phase diagram of Li2O–ZnO–Sb2O5 has been determined. Additionally, the thermal and optical properties of Li3xZn7-4xSb2+xO12 (0.35 ≤ x ≤ 0.65) solid solutions were measured. The thermal properties of sintered samples iso-structural to α-Zn7Sb2O12 displayed a heat dissipation related to Li+ and Sb5+ content having a maximum at x = 0.55. The optical band-gap showed a linear shift toward higher energies as the Li+ and Sb5+ content increased.

The present work lies in the framework of designing polymeric fibre reinforced materials to be used in nanosatellite structures (CubeSat). In the design of any structural system for a space mission the balance between mass, stiffness and strength must be taken into account, also the used materials have to be appropriated for the space environmental conditions. The CubeSat are exposed to high radiation levels (because of the sun irradiance), and so, the accurate determination of the thermal and radiation properties are a key issue for the materials design used in such applications. This work reports the thermal and radiation performance of a biphasic epoxy resin system incorporating two types of ceramic nanoparticles: zinc oxide and graphene, chosen as potential fillers to improve the thermal properties of the epoxy system. Materials are exposed to Gamma and UV radiation at rates of 1 kGy and 10 kGy and characterized after exposure. Different characterization techniques (Thermogravimetric analysis - TGA, Scanning Electron Microscopy - SEM and Colorimetry) are performed to determine thermal properties and possible material degradation after radiation exposure. The influence of the different nanofiller in the thermal and radiation response of the epoxy system are discussed. Thermal properties found are also added to the Finite Element Analysis of a CubeSat composite structure to estimate more accurately its performance under the thermal load and service conditions during satellite life cycle.

In this work a first approximation to obtain non-noble metal electrocatalysts from onion skin wastes is reported. Biocarbon were obtained at a range of 600–800 °C of pyrolysis temperature activated by chemical treatment with HNO3. It was observed that the pyrolysis temperature has a direct effect on the structural and textural properties, besides the morphology of the onion skin waste-derived biocarbon, which shows to have influence on the catalytic activity for the oxygen reduction reaction ORR. AOB700 was the non-noble metal electrocatalyst with the best performance for the ORR evaluated in alkaline electrolyte (0.5 mol L−1 KOH), which had the highest surface area (242 m2g-1) and a current density of −2.35 mA cm−2 with an onset potential of 0.82 V/RHE. The chemical surface composition shows that N-pyridinic, N-amine, N-quaternary and N-pyrrolic nitrogen species are present on this electrocatalysts. The use of onion skin waste as raw material in the production of non-noble metal electrocatalysts is a sustainable solution to avoid the disposal of abundant biomass residues as onion skins.

In this work, high surface area N-doped carbon synthesis from Sargassum spp. is reported as a low cost alternative for electrocatalysts production for the oxygen reduction reaction (ORR). First, Sargassum spp. was activated with potassium hydroxide (SKPH) and then doped with hydrazine (SKPHD). As a result of the activation process, SKPH obtained a high surface area (2289 m2 g−1), 0.16% nitrogen and 2.63% sulfur content; it also showed four-electron-transfer mechanism when tested as electrocatalyst in alkaline medium. Besides, SKPHD presented 3.60% nitrogen content in the bulk and higher ORR activity (0.838 V onset potential vs. RHE and 4.59 mA cm−2 current density) very close to 20% Pt/C (5.25 mA cm−2). Results indicate that using seaweeds as a synthesis precursor is an alternative for the Sargassum spp. disposal in the Caribbean due to its high availability and efficiency towards ORR.

This study presents the synthesis and physicochemical characterization of functionalized carbon-based materials prepared from cassava residues (Manihot esculenta). Cassava residues were obtained from a local market, washed, dried and ground to small particle size. This powder was mixed with different aqueous media: diluted sulfuric acid (0.2 M), nejayote and deionized water. These mixtures were treated in an autoclave at 200 °C for 4 h. The physicochemical characteristics of samples were studied by SEM, TGA, FTIR, XPS and elemental analysis. The chemical composition of C:O was similar among groups, but TGA suggested that the hydrochar prepared with sulphuric acid presented a better thermal stability, with a decomposition peak at 435 °C, which was 80 °C higher than samples prepared with deionized water. The acid sample also had lower mass loss (47.3%). The SEM images showed that sulphuric acid promoted the formation of small needle-like structures, while samples prepared using nejayote and water showed agglomerates with a few spherical shapes. The proximate analysis indicated that there was a carbon enrichment from 41% from the original sample to 62% after the hydrothermal process.

This study was undertaken to evaluate the adsorption of Reactive Black 5 dye (RB5), in aqueous solution, onto MCM-41 mesoporous silica nanoparticles (MSNs) functionalized with 3-aminopropyltriethoxysilane (APTES) by two methods: co-condensation and post-synthesis. The morphological and surface properties of both functionalized materials were compared by SEM, SAXS, N2 sorption and XPS characterization techniques. Sorption experiments were performed in order to determine the effect of pH, contact period and initial concentration of aqueous RB5 on the adsorption properties of bare- and both types of amino-MSNs. The results show that there exist morphological changes in the nanoparticles according to the type of functionalization synthesis, i.e. loss of hexagonal structure in co-condensation method and more density of amino groups on the surface of post-synthesis functionalized materials. The adsorption of RB5 on both type of materials is independent of the pH since they present adsorptions close to 100% in the evaluated pH range. The best fit of the data from adsorption kinetic studies is a pseudo-second-order model, being the material functionalized by the co-condensation method, which presents a higher adsorption rate because of its greater pore volume. The adsorption isotherms fitted well to the Langmuir model, with the amino-MSNs functionalized via the post-synthesis method presenting a higher capacity of adsorption, due to a greater density of amino groups on its surface, thereby facilitating their interaction with the RB5 molecules. Altogether, the results indicate that the type of functionalization synthesis affects the morphological characteristics of the nanoparticles and these, in turn, modify their adsorption properties.

The establishment of microorganisms and particularly fungi on rock surfaces, which is favored by humid tropical climates, may accelerate the degradation of historical monuments and buildings and thereby cause the irreversible loss of rich cultural heritage. Therefore, it is urgent to search for new ways to preserve such buildings. The in vitro antifungal activity of calcium zinc hydroxide dihydrate [CaZn2(OH)6·2H2O] (CZ) synthesized via the sol–gel method has been previously reported for limestone. The present study reports for the first time, the minimum fungicidal concentration (MFC) of CZ obtained via mechanochemical processing, against diverse fungi involved in biodeterioration processes of limestone and dolostone. We found that CZ nanoparticles had a fungicidal effect on all evaluated fungi, at concentrations of 156–1250 μg/mL. The MFC depends on the number of cells in conidia and the presence of melanin in cell walls. For these reasons, Pestalotiopsis maculans and Curvularia lunata, which had more than four cells and melanin pigmentation, both required a greater CZ concentration (1250 μg/mL) for inhibition, compared with species from the genera Penicillium oxalicum and Aspergillus niger, which had one cell and were strongly inhibited. Thus, CZ nanoparticles are promising candidates for application in treatments to restore the cultural heritage.

This report describes the synthesis of a controlled drug delivery system that was obtained by coating mesoporous silica nanoparticles (MSNs) with poly(β-amino ester) (PbAE), which is a solid and stable material at physiological pH, but is dissolved at acidic pH values, such as those in tumor tissues (from 5.0 to 6.5). To synthesize the system, PbAE chains were grafted onto amino-functionalized MSNs through a reaction between the surface amino groups of MSNs and the ends of acrylate chains of a PbAE. The system was physicochemically characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectrometry, and X-ray diffraction analyses. In addition, the in vitro release of doxorubicin (DOX) and doxycycline (DXY) in acidic and physiological media was evaluated. It was observed that the PbAE modification did not affect the mesoporous structure of MSNs. When the amount of 3-aminopropyltriethoxysilane was increased during functionalization, the amount of PbAE binding to MSNs increased as well. With respect to drug release, the sample with the highest amount of PbAE showed better control in the delivery of DXY and DOX in acidic media, because at pH 5.5, the release of both drugs was 40% higher than that at pH 7.4. These results reveal two aspects about the presence of PbAE in MSNs: PbAE does not affect the mesoporous structure of the nanoparticles, and PbAE is the main factor controlling the delivery of drugs in acidic media.

Metal-free electrocatalysts for the oxygen reduction reaction (ORR) were synthesized from cassava residues through a thermal functionalization with sulfuric acid. Their electrocatalytic activities were tested through the ORR performance in basic media. Chemical composition in samples seems to play an important role in their electroactivity, more than textural properties, as the sulfur-treated high-temperature sample (Sy800) has the best performance with an onset potential of 0.69 V vs RHE (reversible hydrogen electrode) and a current of −2.32 mA cm−2 at 0.3 V vs RHE. These functionalized cassava residues are promising materials to be used like carbon-based metal-free electrocatalysts.

Churches in Yucatan region in Mexico are considered a built heritage legacy of great cultural interest. Some of these churches exhibit some pathologies with deformation mainly located at the stone masonry vaults. The churches are mostly built with ruble stone masonry walls and vaults in which limestone and lime mortar predominate. The design of any intervention on this type of structure requires the knowledge on the masonry materials, but very scarce information exist on the properties of limestone and lime mortar used in the construction of the churches. Therefore, the characterization of the existing materials, namely the limestone is considered to be of great interest. This research aims at the characterization of limestones found in masonry churches from sixteenth to eighteenth centuries located in Yucatan region in Mexico. To achieve the objectives, an experimental campaign was designed with the following steps: (1) identification of churches under ruins and in situ collection of stone specimens, (2) characterization of physical and mechanical properties on the collected specimens; (3) evaluation of the mineralogical composition of limestones and petrography description; (4) assessment of correlation between physical and mechanical properties. It was found that the limestones studied were mainly composed of calcium carbonate (CaCO 3 ) and based on the physical properties, it was possible to group them in three different groups. It was also found that different ranges for the compressive strength and modulus of elasticity were obtained for the limestone belonging to each group defined. The relation between physical and mechanical properties was analyzed by a set of statistic correlations, for which very reasonable coefficients of determination were found.

In this work, a new varistor with a high non-linear J-E electrical characteristic (α = 54; EB = 9753 V/cm) is reported, synthesized from the binary system Co7Sb2O12-LiCoSbO4 with general formula Li3xCo7–4xSb2+xO12. This new material is a single-phase iso-structural to Co7Sb2O12 spinel. It was shown that the electrical properties improved with increasing the x value in the solid solution. Li3xCo7–4xSb2+xO12 varistor behaviour is explained by the presence of defects in the crystal structure of Co7Sb2O12 when Li+ and Sb5+ are added, which appears to be responsible for the formation of Schottky type potential barriers at the grain boundaries. Also, it is reported the effect of the sintering temperature on the electrical properties of the varistors. In addition, sub-solidus compatibility relations on the ternary system of Li2O-CoO-Sb2O5, up to>50% Li2O, and the binary phase diagram Co7Sb2O12-LiCoSbO4 have been determined, where an extensive solid solution Li3xCo7–4xSb2+xO12: 0.2 ≤ x ≤ 0.7, was formed. The lattice parameter of Li3xCo7–4xSb2+xO12 solid solution exhibit a discontinuity indicating a change in the substitution mechanism or symmetry of the solid solution. XPS analysis showed how Co2p spectra change as Li+ substitutes Co2+ into the structure and how this affects the linearity of the lattice parameter a.

A series of poly[2-(dimethylamino)ethyl methacrylate]s (PDMAEMAs) of different molar mass were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were subsequently treated with two different alkyl halides (1-iodobutane (BuI) and iodomethane (MeI)) to obtain a library of 21 PDMAEMAs with different degree of quaternization (DQ). This is the first report where the antifungal activity of these polymers is assessed for different fungi relevant in biomineralization and aesthetic biodeterioration of stone surfaces. The antifungal activity was assessed with the minimum inhibitory concentration (MIC), the minimum fungicidal concentration (MFC) and the mycelia growth inhibition in plate for the most promising materials. The obtained results demonstrated that all evaluated polymers possess certain level of antifungal activity against the evaluated fungi (even unquaternized PDMAEMAs). However, polymers of low molar mass (series III) revealed predominantly fungicidal activity at low values of MFC (from 2500 to 9.7 μg mL−1). Unexpectedly, the performed mycelia growth inhibition tests showed that the DQ has a less significant effect on the antifungal properties of the polymers than the polymer molar mass. Hence, the antifungal activity of these polymers may depend to a great extent on the physiological and morphological characteristics of the fungi, wherein the best antifungal activity was observed in III-M2, III-B1 and III-B2. It is worth mentioning that this detailed screening contributes to a better understanding of PDMAEMA-based composites that can be utilized in the development and optimization of low-cost and accessible antimicrobial protective coatings for petrous surfaces in cultural heritage monuments or modern buildings.

In this work, the synthesis and characterization of novel metal-free electrocatalysts obtained from leather scraps is reported. The waste material has been subjected to simple thermochemical treatments (pyrolysis, chemical activation and doping), obtaining high performance electrocatalysts for the Oxygen Reduction Reaction (ORR) in KOH. The effect of pyrolysis temperature on the physicochemical properties and electrochemical performance is studied. The metal-free electrocatalysts possess mesoporous structure with high specific surface area (819–2100 m 2 g −1 ). A higher catalytic activity has been determined for the electrocatalyst treated at 700 °C (AB7), compared to samples pyrolyzed at higher temperatures. Furthermore, AB7 delivers a higher current density compared with commercial 20% Pt/C (j = 9.0 and 4.5 mA cm −2 , respectively), while its on-set potential shifts only 145 mV to more negative values. The metal-free catalysts are a promising eco-friendly and scalable alternative as cathode materials for alkaline fuel cells and other electrochemical energy devices.

{Pt, Ir}/Ce1-xRuxO2, catalysts were prepared to be used in the hydrogen production from the ethanol steam reforming reaction. Initially, the catalytic supports, Ce1-xRuxO2, were synthesized by the sol–gel process. Later, the Pt/Ce0.97Ru0.03O2 and Ir/Ce0.97Ru0.03O2 catalysts were produced through incipient wetness impregnation using high purity compounds as sources of Pt or Ir. These systems were characterized by means of SEM, XRD, TEM, and specific surface area measurements. The catalysts were tested in the ethanol steam reforming reaction at stoichiometric conditions (water/ethanol = 3) in a continuous flow fixed–bed quartz microreactor under atmospheric pressure in the temperature range of 300–600 °C. From the results, it follows that the support itself acts as a catalyst for the reaction. The catalytic support (Ce0.97Ru0.03O2) and the catalytic species (Pt, Ir) exhibit sustained conversion during the studied interval of temperature. It was observed that at 600 °C, Pt/Ce0.97Ru0.03O2 and Ir/Ce0.97Ru0.03O2 achieve a (5 H2/ethanol) molar ratio. Stability tests revealed that Pt/Ce0.97Ru0.03O2 and Ce0.97Ru0.03O2 compounds showed an outstanding performance in the ethanol steam reforming reaction for more than 10 h before being deactivated.

In the present work, the photocatalytic efficiency of a novel system based on ZnO doped with nitrogen (ZT) and supported on graphene oxide (GO) is investigated. ZnO synthesis and their N doping were carried out in a microwave reactor using thiourea as nitrogen source, while the GO was prepared through a variation of the Hummers' method. Structural, morphological and photochemical characterization of the developed material was performed by X-ray diffraction (XRD), UV–Vis spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), analysis by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The compounds were used to photodegrade the methylene blue molecule, which confirms the efficiency of nitrogen doped supported system compared to pristine ZnO. The degradation percentage of MB under UV energy using nitrogen-doped ZnO/GO, in a time of 35 min, reached 98% degradation; while using visible light 93% of degradation was reached.

This study synthesized and characterized composites of graphene oxide and TiO 2 (GO–TiO 2 ). GO–TiO 2 thin films were deposited using the doctor blade technique. Subsequently, the thin films were sensitized with a natural dye extracted from a Colombian source ( Bactris guineensis ). Thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements were used for physico-chemical characterization. All the samples were polycrystalline in nature, and the diffraction signals corresponded to the TiO 2 anatase crystalline phase. Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) verified the synthesis of composite thin films, and the SEM analysis confirmed the TiO 2 films morphological modification after the process of GO incorporation and sensitization. XPS results suggested a possibility of appearance of titanium (III) through the formation of oxygen vacancies (O v ). Furthermore, the optical results indicated that the presence of the natural sensitizer and GO improved the optical properties of TiO 2 in the visible range. Finally, the photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution, and pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation. These results indicated that the presence of GO has an important synergistic effect in conjunction with the natural sensitizer, reaching a photocatalytic yield of 33%.

Different aspect ratio nanostructures of pure ZnO and Zn(1−x)EuxO were produced through the application of a statistical factorial design 23. The procedure consisted of two stages. First, the growth of ZnO thin films by atomic layer deposition on silicon (111) substrates, by decomposition of the metal precursor, diethyl zinc, at 190 °C and 0.25 Torr. In the next stage, those films were processed using the microwave-assisted hydrothermal method to promote the growing of ZnO nanostructured compounds, using a precursor solution of Zn(NO3)2·6H2O and hexamethylene tetramine, acting as a bi-dentate ligand capable of bridging two Zn2+ ions in solution. In addition, europium-doped ZnO (Zn(1−x)EuxO) and ZnO nanostructures were produced using Zn(NO3)2·6H2O and Eu(NO3)3·5H2O. The experimental levels (values) considered for every factor were Eu3+ concentration (0.02 and 0.06, atomic, %), temperature (80° and 120 °C) and time (30 and 50 min). The synthesis products were characterized through X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and photoluminescence measurements. Our results demonstrate that it is possible to produce nanostructures with specific size, morphology and physical properties depending on the specific synthesis based on our proposed experimental design.

The process of biodeterioration is one of the main problems affecting historical monuments and buildings. On rock surfaces, different types of microorganisms establish in the most adequate niches and accelerate degradation, leading to the irreversible loss of cultural heritage. Therefore, new ways to preserve cultural heritage must be urgently studied to prevent such damage. In this study, the broad-spectrum antimicrobial activity of calcium zinc hydroxide dehydrate [Ca(Zn(OH)3)2·2H2O] (CZ) and zinc oxide (ZnO) nanoparticles synthesized by the sol–gel method is examined against fungal and bacterial model organisms. The selected microbes were inhibited by both nanoparticles, yet CZ was the most effective, with a bactericidal activity of 1.25 to 5 mg/mL and a fungicidal activity of 0.625 mg/mL. Both nanoparticles caused structural damage to the evaluated fungal cells, resulting in morphological changes and affecting the germination of conidia. For the first time in the literature, the antibacterial activity and the mode of action of CZ are reported. In conclusion, CZ nanoparticles are shown to be potential candidates for the treatment of rock surfaces of built cultural heritage., We are grateful for the financial support of the National Council for Science and Technology (Consejo Nacional de Ciencia y Tecnología [CONACyT]) of the “Fronteras de la Ciencia 138” project. Additional thanks are extended to CONACyT for the doctoral scholarship granted to MSC 282192.

The evaluation of the antifungal activity of Mg(OH)2 and Ca(OH)2 nanoparticles (NPs), synthesized by sol–gel method and their mixtures at different concentrations, is reported. The antifungal activity of the hydroxide NPs was studied using Aspergillus niger and Penicillium oxalicum isolated from stone surfaces. These model organisms were selected due to their ability to grow on outdoor and indoor climates and their significant impact on human health. Moreover, the antifungal activity of Mg(OH)2 and Ca(OH)2 NPs dispersed in positively charged polymeric matrices based on partially quaternized poly(2-(dimethylamino ethyl) methacrylate) (pDMAEMA) was studied. With respect to the morphology, particle size, and textural properties of the NPs, the mixtures of Mg–Ca hydroxides revealed a uniform and smaller particle size, along with a greater surface area, as compared to pristine Ca(OH)2 NPs. However, the Ca(OH)2 and a mixture of Mg(OH)2 and Ca(OH)2 (10:90 weight ratio) NPs, showed an enhanced growth inhibition of A. niger and P. oxalicum, suggesting that the effect of particle size on the antifungal activity would not be a preponderating factor. In addition, improved antifungal properties against A. niger and P. oxalicum were detected in composite coatings based on hydroxide NPs dispersed in quaternized p(DMAEMA-co-METAI). The use of these systems might provide promising composite materials with potential antifungal properties for various applications., This study was financially supported by the National Council for Science and Technology (Consejo Nacional de Ciencia y Tecnología [CONACYT, Mexico]) of the “Fronteras de la Ciencia No. 138” project and by the Community of Madrid under the “Climortec”, BIA2014−53911-R, “Geomaterials 2” Programme (S2013/MIT_2914), and Multimat Challenge (S2013/MIT-2862). A.S.-F. would like to gratefully acknowledge the financial support of Santander Universidades through “Becas Iberoamérica Jóvenes Profesores e Investigadores, España 2015” scholarship program. C.G.-S., R.Y.-M., and U.S.S. thank CONACYT and the Deutscher Akademischer Austauschdienst (DAAD, Germany) for financial support within the framework of the funding program for international mobility PROALMEX 2015 (CONACyT project: 267752 and DAAD project: 57271725). C.G.-S. and U.S.S. also thank the Deutsche Forschungsgemeinschaft (DFG, Germany) for financial support for this research under the scheme of the grant SFB-1278 “PolyTarget” project B02.

Biocomposites of polylactic acid, thermoplastic starch, chitosan powder, and chitosan lyophilized powder were prepared using an extrusion process. The color, thermal, structural, mechanical, morphology, and antimicrobial properties were evaluated. The addition of thermoplastic starch and chitosan (chitosan powder and chitosan lyophilized powder) produced significant changes in color and heterogeneous surface morphology of the polylactic acid biocomposites. The thermal, mechanical, and morphometric properties of the material showed changes with the addition of thermoplastic starch and chitosan (chitosan powder and chitosan lyophilized powder). The biocomposites formulated with chitosan powder and chitosan lyophilized powder showed antifungal activity when evaluating this property. The biocomposites produced could be used in packaging applications.

Mesoporous silica nanoparticles (MSNs) are frequently functionalized to be used for specific applications, including catalysis and biomedical engineering. In this research, MCM-41-MSNs were synthesized by the sol–gel method and were functionalized with different quantities of (3-aminopropyl) triethoxysilane (APTES) using a post-grafting method to determine the physicochemical and structural changes in the MSNs. The functionalized materials were assessed by different characterization techniques, namely, TGA, FTIR, BET, SEM, TEM, DLS, zeta potential, SAXS, XRD and XPS. The FTIR data confirmed the presence of amino groups on the MSN surfaces, and the results from the XPS, TGA and zeta potential demonstrated that the APTES concentration during post-grafting directly affects the quantity of amino groups bound to the MSNs. The SAXS, TEM and nitrogen adsorption–desorption analyses showed that as the amount of APTES in the MSNs increases, the mesoporous structure become more disordered.

Poly(lactic acid) (PLA) is a well-known biodegradable polymer with strong potential application in food packaging industry. In this paper, samples of PLA clamshell for tomatoes packaging were exposed with 60CO γ-ray's source (1.33 MeV) at different dose levels (0, 10, 60, 150, 300, and 600 kGy), at room temperature and in presence of air. The physicochemical properties of neat PLA and sample exposed to gamma irradiation were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and tensile measurements. Results show as the dose increases, the molecular weight (Mw), melting temperature (Tm), tensile strength and elongation at break decreased. However, the tensile modulus increased with increasing doses. The surface of PLA clamshells was degraded (scratches and minor cracks) when samples were exposed to doses greater than 60 kGy.

The antifungal and photocatalytic activity of mixed compounds of double hydroxide (CaZn2(OH)6•2H2O) with portlandite (Ca(OH)2) synthesized via sol-gel were evaluated. The compound was tested by in vitro assay to determine its antifungal activity using the agar diffusion and broth microdilution assays, applied to the fungal models: Aspergillus niger and Penicillium oxalicum. Also, these compounds were characterized by X-ray diffraction, infrared spectroscopy, dispersion light scattering, and its morphological structure was identified by HR-SEM and TEM-SAED which shows agglomerated particles formed by nanoparticle sizes between 100-500 nm, which are correlated whit hydrodynamic radio around 155 nm. Additionally, in the relation of microbiological assays, the outstanding minimum inhibitory concentration of unmixed calcium zincate hydroxide dihydrate (CZ) correspond to 156 μg/mL, however, when is mixed with 10% of Ca(OH)2 diminishes up to 78 μg/mL, indistinctively of the evaluated fungus. Likewise, a photocatalytic degradation test was carried out with methylene blue dye as a model organic pollutant, reaching an efficiency of ∼92%. Our results suggest that low concentrations of Ca(OH)2 improve the antifungal activity of CZ, without altering the solution stability, the photocatalytic and chemical properties of the compounds. Therefore, the compatibility with the limestone of both materials can be proposed as an excellent product to avoid fungal biodeterioration.

The main motivation of this work is to deposit two different metals (gold and silver) on titanium oxide nanoparticles surface in a one-step simple and fast physical process by applying a nitrogen plasma as the main source of nitrogen atoms to obtain nanostructured N-TiO2 − X/Au/Ag materials. The obtained nanomaterials were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. Based on the characterization results, we found that gold and silver nanoparticles were uniformly loaded on the titanium oxide nanocomposite surface, showing a surface plasmon absorption band due to the loading of the metal nanoparticles over titania samples. The results of this work have shown that nitrogen plasma technique is a more feasible and simple alternative to obtain the N-TiO2 − X/Au/Ag nanocomposite. Moreover, this plasma technique could be used to impregnate with other kind of metals over the surface of diverse nanomaterials.

Hybrid bionanocomposites based on cellulose matrix, with silica nanoparticles as reinforcers, were prepared by one-pot synthesis of cellulose surface modified by solvent exchange method to keep the biopolymer net void for hosting inorganic nanoparticles. Neither expensive inorganic-particle precursors nor crosslinker agents or catalysts were used for effective dispersion of reinforcer concentration up to 50 wt %. Scanning electron microscopy of the nanocomposites shows homogeneous dispersion of reinforcers in the surface modified cellulose matrix. The FTIR spectra demonstrated the cellulose features even at 50 weight percent content of silica nanoparticles. Such a high content of silica provides high thermal stability to composites, as seen by TGA-DSC. The fungi decay resistance to Trametes versicolor was measured by standard test showing good resistance even with no addition of antifungal agents. This one-pot synthesis of biobased hybrid materials represents an excellent way for industrial production of high performance materials, with a high content of inorganic nanoparticles, for a wide variety of applications.

This study presents a correlation between microstructure, atomic-scale observations and intrinsic cathodoluminescence (CL) emission from two types of brucite (Mg(OH)2) nanoparticles synthesized by hydrothermal and sol–gel methods, and a third one that was commercially acquired. It is reported, for the first time, spectral CL in an environmental scanning electron microscope, in the blue region (λ ∼300–660 nm). X-ray diffraction (XRD), environmental and field emission scanning electron microscopy (ESEM, FESEM) transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM)-electron diffraction were carried out for morpho-structural characterization. HRTEM observations allowed highlighting features at the atomic scale, including the different degrees of misfit inherent to each type of synthesis. Dislocations and stacking faults were oriented parallel to 0001 planes, giving rise to strain fields that explained the strongly preferred orientation observed by XRD in the commercial sample. In the same way, edge dislocations affected the 0001 planes of the hydrothermal sample. In the sol–gel sample, distortions produced by bent lattice planes affected the stacking sequence of 011–1 planes and confirmed the XRD results. CL showed strong dependence on particle orientation. Stable signals with peaks at 381 nm (3.25 eV), 409 nm (3.03 eV) and 466 nm (2.66 eV) were detected in the three samples along the (11–20) surface after applying 20 kV. Some differences in the intensity degree and peak position were detected in the (0001) surface. Additional signals at 425 (2.91 eV) and 488 (2.54 eV) detected in the sol–gel sample confirmed the presence of magnesite (MgCO3) due to carbonation processes. The intrinsic CL emissions were associated with differences in the development of lattice strains, which produced luminescence centers. Better understanding of intrinsic CL was achieved thanks to the correlation with microstructure and atomic-scale properties., This study was supported by the Autonomous Region Program of Madrid, Geomateriales 2 (S2013/MIT_2914), Multimat-Challenge (S2013/MIT-2862), Innovation and Education Ministry (Climortec, BIA2014-53911-R, MAT201347460-C5-5-P), MAT2016-80875-C3-3-R, S2013/MIT-2862 projects and the CONACYT project Fronteras de la Ciencia No. 138.

The degradation of stone cultural heritage represents an irreversible loss of rich cultural heritage, and seeking ways to preserve it is urgent. Among different degradation processes, the loss of stone cohesion and biodeterioration are two of the most common issues that affect stone substrates. To solve this, the introduction of nanotechnology in the cultural heritage preservation field has represented a great revolution. The reason is that a particle size reduction of materials to the nanoscale highly increases their effectiveness as stone treatments. Thereby, different nanomaterials have been developed and applied as consolidating products and protective coatings in stone artworks. Due to the increased compatibility of inorganic nanoparticles (NPs) with a large part of the built and sculptural heritage, this chapter accentuates the use of inorganic NPs for the consolidation and antifungal protection of stone heritage. Special focus is given to the factors that can influence the success of the treatment.

Avocado (Persea americana) and papaya (Carica papaya) are tropical fruits with high international demand. However, these commercially important crops are affected by the fungusColletotrichum gloeosporioides, which causes anthracnose and results in significant economic losses. The antifungal activity of metal oxide nanomaterials (zinc oxide (ZnO), magnesium oxide (MgO), and ZnO:MgO and ZnO:Mg(OH)2composites) prepared under different conditions of synthesis was evaluated against strains ofC. gloeosporioidesobtained from papaya and avocado. All nanoparticles (NPs) at the tested concentrations significantly inhibited the germination of conidia and caused structural damage to the fungal cells. According to the radial growth test, the fungal strain obtained from avocado was more susceptible to the NPs than the strain obtained from papaya. The effect of the tested NPs on the fungal strains confirmed that these NPs could be used as strong antifungal agents againstC.gloeosporioidesto control anthracnose in tropical fruits.

Microstructure and composition are factors determining heat transfer in ZnO ceramic materials, which define the performance of the material after Joule heating, generated by electron transport. In this study, photothermal radiometry was applied to investigate the influence of the sintering temperature, ranging from $$800\,{^{\circ }}\hbox {C}$$ to $$1300\,{^{\circ }}\hbox {C}$$ , by measuring the thermal diffusivity and thermal conductivity at room temperature, of commercial and sol–gel ZnO pellets. Our results show that the values of these thermal properties for both types of ZnO increase when the sintering temperature increases, displaying maximum energy dissipation at $$1200\,{^{\circ }}\hbox {C}$$ . Additionally, the role of the sintering temperature on the optical properties was also analyzed using diffuse reflectance spectroscopy, and from these data the optical band-gap was obtained.

Microwave hydrothermal synthesis, using an experimental 23 factorial design, was used to produce tunable ZnO nano- and microstructures, and their potential as photocatalysts was explored. Photocatalytic reactions were conducted in a microreactor batch system under UV and visible light irradiation, while monitoring methylene blue degradation, as a model system. The variables considered in the microwave reactor to produce ZnO nano- or microstructures, were time, NaOH concentration and synthesis temperature. It was found that, specific surface area and volume/surface area ratio were affected as a consequence of the synthesis conditions. In the second stage, the samples were plasma treated in a nitrogen atmosphere, with the purpose of introducing nitrogen into the ZnO crystalline structure. The central idea is to induce changes in the material structure as well as in its optical absorption, to make the plasma-treated material useful as photocatalyst in the visible region of the electromagnetic spectrum. Pristine ZnO and nitrogen-doped ZnO compounds were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET), XPS, and UV–Vis diffuse reflectance spectroscopy. The results show that the methodology presented in this work is effective in tailoring the specific surface area of the ZnO compounds and incorporation of nitrogen into their structure, factors which in turn, affect its photocatalytic behavior.

More recently, the biological colonization of stone heritage and consequently its biodeterioration has become the focus of numerous studies. Among all microorganisms, fungi are considered to be one of the most important colonizers and biodegraders on stone materials. This is why the development of new antifungal materials requires immediate action. ZnMgO nanoparticles (NPs) have several exciting applications in different areas, highlighting as an efficient antimicrobial agent for medical application. In this research, the application of Zn-doped MgO (Mg1–xZnxO, x = 0.096) NPs obtained by sol–gel method as antifungal coatings on dolomitic and calcitic stones has been explored as a means to develop effective protective coatings for stone heritage. Moreover, the photocatalytic and antifungal activity of Mg1–xZnxO NPs were comparatively studied with single ZnO and MgO NPs. Thus, compared to the MgO and ZnO nanomaterials, the Mg1–xZnxO NPs exhibited an enhanced photocatalytic activity. After UV irradiation for 60 min, 87% methylene blue was degraded over Zn-doped MgO NPs, whereas only 58% and 38% of MB was degraded over ZnO and MgO NPs, respectively. These nanoparticles also displayed a better antifungal activity than that of single pure MgO or ZnO NPs, inhibiting the growth of fungi Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans, which are especially active in the bioweathering of stone. The improved photocatalytic and antifungal properties detected in the Mg1–xZnxO NPs was attributed to the formation of crystal defects by the incorporation of Zn into MgO. The application of the MgO- and Zn-doped MgO NPs as protective coatings on calcareous stones showed important antifungal properties, inhibiting successfully the epilithic and endolithic colonization of A. niger and P. oxalicum in both lithotypes, and indicating a greater antifungal effectiveness on Zn-doped MgO NPs. The use of Zn-doped MgO NPs may thus represent a highly efficient antifungal protection for calcareous stone heritage., This research has been financially supported under projects FOMIX-Yuc 2008–108160, CONACYT LAB-2009-01-123913, 188345, Fronteras de la Ciencia No. 138, by the Community of Madrid under the Geomaterials 2 Programme (S2013/MIT_2914), Climortec, BIA2014–53911-R and MAT2013-47460-C5-5-P, and the Autonomous Region Program of Madrid, MULTIMAT CHALLENGE (S2013/MIT-2862). A.S.-F. would like to gratefully acknowledge the financial support of Santander Universidades through “Becas Iberoamérica Jóvenes Profesores e Investigadores, España 2015” scholarship program.

This work reports the synthesis of N-doped porous carbon (NPC) with a high surface area from Sargassum spp. as a low-cost alternative for electrocatalyst production for the oxygen reduction reaction (ORR). Sargassum spp. was activated with potassium hydroxide at different temperatures (700, 750, and 800 °C) and then doped with pyridine (N700, N750, and N800). As a result of the activation process, the 800 °C sample showed a high surface area (2765 m2 g−1) and good onset potential (0.870 V) and current density (4.87 mA cm−2). The ORR performance of the electrocatalysts in terms of their current density was N800 > N750 > N700 > 750 > 800 > 700, while the onset potential decreased in the following order: N800 > 800 > 750 > 700 > N700 > N750. The fuel cell performance of the membrane electrode assembly (MEA) prepared with electrocatalyst synthesized at 750 °C and doped with pyridine was 12.72 mW cm−2, which was close to that from Pt/C MEA on both the anode and cathode (14.42 mW cm−2). These results indicate that NPCs are an alternative to the problem of Sargassum spp. accumulation in the Caribbean due to their high efficiency as electrocatalysts for ORR.

Moisture is a critical control of chemical and physical processes leading to stone deterioration. These processes can be enhanced by microbial biofilms and associated exopolymers (EPS). There is limited current understanding of the water transport process across rocks covered by EPS. In the present work, we employed the photoacoustic technique to study the influence of three biopolymers (xanthan, microbactan and arabic gum) in the water transport process of two types of limestone rock of similar mineralogy but contrasting porosity. Both controls of RL (low porosity) and RP (high porosity) presented the higher values of water diffusion coefficient (D) than biopolymer-coated samples, indicating that biopolymer layers slowed down the transport of water. This trend was steeper for RP samples as water was transported seven times faster than in the more porous rock. Important differences of D values were observed among samples coated by different biopolymers. Scanning electron microscopy and optical microscopy showed that surface topography was different between both types of rocks; adherence of coatings was seen predominantly in the less porous rocks samples. FTIR and NMR analysis showed the presence of pyruvate and acetate in microbactan and xanthan gum, suggesting their participation on adherence to the calcareous surfaces, sealing surface pores. These results indicate that water transport at rock interfaces is dependent on the chemistry of biopolymer and surface porosity. The implications for reduced water transport in stone conservation under the influence of biopolymers include both enhanced and lower deterioration rates along with altered efficiency of biocide treatment of epilithic biofilms.

In this work, the development of a new crystallization technique is reported, using nitrogen plasma (AC) to obtain nanostructured anatase and rutile from amorphous titanium oxide (TiO2). This methodology increases throughput and minimizes thermal effects. Nanostructured amorphous TiO2 was obtained by the sol-gel method and subsequently subjected to AC treatment, at a controlled pressure, applying different powers and treatment times in order to obtain phase changes. The obtained samples were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The results show the crystallization in parallel with anatase and rutile phases with a proportion that is directly related to the applied power in the plasma and the treatment time. This technique allows us to obtain smaller crystals in comparison with those of classic thermal methodologies. It is also demonstrated that the application of plasma represents a novel and innovative method to obtain phase polymorphic changes in titanium oxide without needing to apply prolonged heat treatments at high temperatures and can therefore be taken into consideration as a technique with low energy costs, in comparison with conventional heat treatments.

Titanium oxide matrix was prepared by sol-gel adding fluoxetine [Prozac (C17H18NF3O)] during the reaction of gelation. This nanostructured material was studied by Fourier transform infrared (FTIR) spectroscopy, N2 adsorption, and x-ray diffraction to detect the interaction between the drug and the matrix. The complex nature of FTIR signals for the matrix and the drug did not allow observation of the interactions; however, using the density functional theory formalism, two stable complexes are suggested to be formed on the drug–matrix system. Both complexes are formed through H bond interactions involving the amine group in fluoxetine and the hydroxylated sites in titanium xerogel. They were found to be energetically stable and independent of the titanium model core cluster used in the calculations.

Silica gel and MCM-41 synthesized mesoporous materials were treated with either oxygen (O2), hexamethyldisiloxane (HMDSO) and organic vapors like ethanol (EtOH), and acrylonitrile (AN) inductive plasma. The radiofrequency power for the modification was fixed to 120 W and 30 min, assuring a high degree of organic ionization energy in the plasma. The surface properties were studied by infrared spectroscopy (FTIR), scanning electron microscopy, x-ray photoelectron spectroscopy and dynamic light scattering technique was used for characterizing size distributions. When the silica and MCM-41 particles were modified by AN and HMDSO plasma gases, the surface morphology of the particles was changed, presenting another color, size or shape. In contrast, the treatments of oxygen and EtOH did not affect the surface morphology of both particles, but increased the oxygen content at the surface bigger than the AN and HMDSO plasma treatments. In this study, we investigated the influence of different plasma treatments on changes in morphology and the chemical composition of the modified particles which render them a possible new adsorbent for utilization in sorptive extraction techniques for polar compounds.

The physical properties of aluminum thin films depend strongly on their microstructure, which can be characterized using different techniques. In the present work, aluminum thin films—grown with di...

Atomic layer deposition (ALD) followed by microwave hydrothermal processing was successfully employed for producing doped and vertically aligned ZnO nanorod arrays with different aspect ratio. Firstly, a textured ZnO layer with preferential orientation normal to the c-axis was formed on substrate (1 1 1) silicon single crystals by means of the ALD technique. This was achieved through the decomposition of diethylzinc at 190 °C and 3.289 × 10−4 atm, which provided an adequate template with nucleation sites, favoring further growth of vertical nanorods. Subsequently, nanorod array growth was produced on the same surfaces through solvothermal synthesis using as promoter a solution of Zn(NO3)2. In addition, growth of indium-doped ZnoO nanorods over the substrates was produced by using In(CH3COO)3 as a doping agent. The method presented allows good quality ZnO and Zn1−x In x O thin films to be obtained. Photoluminiscence spectra show clear evidence of the inclusion of indium in the ZnO matrix. The higher intensity ratio Zn0.96In0.4O/ZnO was increased 40-fold, demonstrating such an effect.