Nanomateriales de carbono, síntesis, funcionalización y aplicaciones

Mención Internacional en el título de doctorLa presente tesis trata acerca del estudio y la búsqueda de aplicaciones de nanomateriales de carbono, principalmente enfocándonos en nanotubos de carbono y grafeno oxidado. La razón por la cual se eligieron estos nanomateriales es debido a su gran versatilidad, a sus excelentes propiedades tanto eléctricas, mecánicas, su gran aspecto superficial que en si engloban a todos estos materiales, haciéndolos candidatos para la era del postsilicio, que los hacen susceptibles a su uso en diferentes aplicaciones. Para tal efecto, en el primer capítulo se realizara un esbozo acerca del descubrimiento, propiedades y tipos de nanomateriales de carbono partiendo desde los que inicio de este boom nanotecnológico el cual fue el fullereno, seguido de los nanoconos a fin de dar al lector una visión de partida de cómo es que nacieron los nanomateriales de carbono, seguido de una explicación más detallada de lo que son los nanotubos de carbono así como los tipos existentes en la actualidad(de pared simple o pared múltiple, al igual que su tipo de dopaje) y a su vez también se hablara en términos generales del grafeno. Al estudiar los nanomateriales, una de sus principales áreas de mayor importancia es su síntesis. Cabe aquí hacer mención que esta tesis se centró en la síntesis de distintos tipos de nanotubos (puros, dopados con grupos oxigenados y dopados con nitrógeno) con la finalidad de alterar sus propiedades tanto reactivas, electrónicas y mecánicas; mientras que en el caso del grafeno se sintetizo el grafeno oxidado. En cuanto a la síntesis, se partieron de técnicas fáciles de emplear y con gran rendimiento del producto, usándose CVD para los nanotubos de carbono y el método Brodie debido a su tiempo de síntesis el cual es mucho menor en comparación con el método de Hummers. El requerimiento de innovar y proporcionar un mayor abanico de posibilidades con respecto a la mejora y adquisición de nuevas propiedades, se han investigado lo que se refiere a los materiales híbridos que son una nueva área en pleno crecimiento, centrándose principalmente en el desarrollo de materiales híbridos con nanopartículas en donde las nanopartículas logran incorporar a los nanotubos de otras grandes ventajas, como una mayor sensibilidad ante ciertos analitos o la incorporación de propiedades magnéticas, por mencionar tan solo algunos ejemplos, por lo que el capítulo 5 se centrara en la creación de estos materiales híbridos.This thesis deals about the study and research of carbon nanomaterials and their possibles applications, mainly focusing on carbon nanotubes and oxide graphene. We chose these nanomaterials due to their versatility such as excellent electrical, mechanical properties and their large surface-area relation, making them good candidates for the era of postsilicio and for different applications. For this purpose, in the first chapter a brief introduction of carbon nanomaterials will be dealt since their discovery, properties and kinds of nanomaterials from fullerene, nanocone as starting point following by a detail explanation about carbon nanotubes as single walled carbon nanotubes, multi-walled carbon nanotubes and doped carbon nanotubes, and finally a short description about graphene. Another main area of interest is their synthesis. It is worth mentioning here, that this thesis is focused on the synthesis of different types of nanotubes (pristine, doped with oxygen groups and nitrogen doped carbon nanotubes) in order to alter their reactivity, electronic and mechanical properties; while in the case of oxidized graphene was synthesized oxide graphene. It was chosen techniques of synthesis with a high yield product: CVD for carbon nanotubes and Brodie method for oxide graphene. In order to provide different types of synthesis, also some examples for creating carbon nanoribbons based on carbon nanotubes are outlined, this was done in order to induce to reader to the variety of structures that can be obtained from a starting material, wherein playing with the symmetry of carbon nanomaterials it is possible to obtain different structures. Between the aplications for carbon nanomaterials are electrophoresis, fillers for reinforcement matrices to obtain polymeric nanocomposites, films for sensors and photosensors, where a good dispersion can lead to a substantial improvement in results for this purpose. Functionalization is another priority part of this thesis to prevent aggregation of carbon nanotubes. Meanwhile oxide graphene with the presence of some oxygen groups has more solubility in comparison with carbon nanotubes. The requirement to innovate and provide a wider range of possibilities with regard to the improvement and acquisition of new properties, it has been investigated with hybrid materials focusing mainly on the development of hybrid materials with nanoparticles, where the nanoparticles are able to incorporate new properties to carbon nanotubes giving great benefits, such as increased sensitivity to certain analytes. With respect to polymeric nanocomposites this issue would be dealt during the Chapter 2.4 of this thesis, while Chapter 2.5 will be addresed to main applications that have been developed along my PhD work such as gas sensors, photosensors, electrophoresis, as field emission and improving of polimeric properties, ending with the general conclusions of my thesis.Programa Oficial de Doctorado en Ciencia e Ingeniería de MaterialesPresidente: Yadira Itzel Vega Cantu.- Secretario: Javier Pozuelo de Diego.- Vocal: Cesar Merino de Dieg

Rapid and efficient testing of the toxicity of graphene-related materials in primary human lung cells

Graphene and its derivative materials are manufactured by numerous companies and research laboratories, during which processes they can come into contact with their handlers' physiological barriers—for instance, their respiratory system. Despite their potential toxicity, these materials have even been used in face masks to prevent COVID-19 transmission. The increasingly widespread use of these materials requires the design and implementation of appropriate, versatile, and accurate toxicological screening methods to guarantee their safety. Murine models are adequate, though limited when exploring different doses and lengths of exposure—as this increases the number of animals required, contrary to the Three R's principle in animal experimentation. This article proposes an in vitro model using primary, non-transformed normal human bronchial epithelial (NHBE) cells as an alternative to the most widely used model to date, the human lung tumor cell line A549. The model has been tested with three graphene derivatives—graphene oxide (GO), few-layer graphene (FLG), and small FLG (sFLG). We observed a cytotoxic effect (necrosis and apoptosis) at early (6- and 24-h) exposures, which intensified after seven days of contact between cells and the graphene-related materials (GRMs)—with cell death reaching 90% after a 5 µg/mL dose. A549 cells are more resistant to necrosis and apoptosis, yielding values less than half of NHBE cells at low concentrations of GRMs (between 0.05 and 5 µg/mL). Indeed, GRM-induced cell death in NHBE cells is comparable to that induced by toxic compounds such as diesel exhaust particles on the same cell line. We propose NHBE as a suitable model to test GRM-induced toxicity, allowing refinement of the dose concentrations and exposure timings for better-designed in vivo mouse assays

Subchronic Graphene Exposure Reshapes Skin Cell Metabolism

In recent years, the toxicity of graphene-related materials (GRMs) has been evaluated in diverse models to guarantee their safety. In most applications, sublethal doses of GRMs contact human barriers such as skin in a subchronic way. Herein, the subchronic effect (30 day exposure) of three GRMs (GO 1, GO 2, and FLG) with different oxidation degrees and sizes was studied. The effects of these materials on human skin cells, HaCaTs, were assayed through high-throughput metabolic-based readout and other cell-based assays. A differential effect was found between the different GRMs. GO 2 induced a metabolic remodeling in epithelial cells, increasing the level of tricarboxylic acid components, mirrored by increased cell proliferation and changes in cell phenotype. The oxidation degree, size, and method of manufacture of GRMs dictated harmful effects on cell metabolism and behavior generated by nontoxic exposures. Therefore, a “safe by design” procedure is necessary when working with these nanomaterial

Interactions of airborne graphene oxides with the sexual reproduction of a model plant: When production impurities matter

The increasing use of graphene-related materials (GRMs) in everyday-life products raises concerns for their possible release into the environment and consequent impact on organisms. GRMs have widely varying effects on plants and, according to recent evidences, graphene oxide (GO) has the potential to interfere with the sexual reproduction owing to its acidic properties and production residues. Here, stigmas of the model plant Cucurbita pepo (summer squash) were subjected to simulated dry depositions of GO and GO purified from production residues (PGO). Stigmas were then hand-pollinated and GRM deposition was checked by ESEM and confocal microscopy. Analysis of stigma integrity, pH homeostasis and pollen-stigma interactions did not reveal negative effects. Fruit and seed production were not affected, but GO depositions of 22.1 ± 7.2 ng mm-2 affected the normal development of seeds, decreasing seed dimensions, seed germination and germination speed. The elemental analysis revealed that GO has significant quantities of production residues, such as strong acids and oxidants, while PGO has only traces, which justifies the differences observed in the effects caused by the two materials. Our results show that GO depositions of up to 11.1 ± 3.6 ng mm-2, which fall within the variation range of total dry particulate matter depositions reported in the literature, are safe for reproduction of C. pepo. This is the first "safety" limit ever recorded for depositions of "out-of-the-box" GO concerning the reproduction of a seed plant. If confirmed for wind-pollinated species, it might be considered for policymaking of GRMs emissions in the air

SERS-Based Methodology for the Quantification of Ultratrace Graphene Oxide in Water Samples

The extensive use of graphene materials in real-world applications has increased their potential release into the environment. To evaluate their possible health and ecological risks, there is a need for analytical methods that can quantify these materials at very low concentrations in environmental media such as water. In this work, a simple, reproducible, and sensitive method to detect graphene oxide (GO) in water samples using the surface-enhanced Raman spectroscopy (SERS) technique is presented. The Raman signal of graphene is enhanced when deposited on a substrate of gold nanoparticles (AuNPs), thus enabling its determination at low concentrations with no need for any preconcentration step. The practical limit of quantification achieved with the proposed method was 0.1 ng mL–1, which is lower than the predicted concentrations for graphene in effluent water reported to date. The optimized procedure has been successively applied to the determination of ultratraces of GO in water samples

Effect of nitrogen and oxygen doped carbon nanotubes on flammability of epoxy nanocomposites

To overcome the flammability of epoxy resins, novel nitrogen (CNₓ) and oxygen (COₓ) doped CNT were synthesized via CVD method and epoxy nanocomposites at 2 wt.%. constant loading were prepared by three roll milling and cured. The structures of the nanotubes were confirmed by XRD, XPS, SEM and Raman and it was found a very high aspect ratio especially for COₓ. Thermal degradation as well as glass transition temperatures and elastic moduli were measured by TGA, DSC and DMTA. The flammability of epoxy nanocomposites was studied by microscale combustion calorimetry (MCC) and limiting oxygen index (LOI) determination. Results showed that the fire retardant properties of nanocomposites improved significantly specially for COₓ, which presented a very high LOI (35%) and a homogeneous and uniform surface after burning. This effect was tentatively attributed to the very high aspect ratio of COₓ tubes.Authors wish to acknowledge financial support from Spanish Ministerio de Economía y Competitividad under grant MAT2014-57557-R. Authors also wish to thank Dr. Sofía M. Vega-Díaz for her invaluable help with XPS interpretatio

Easy and Versatile Synthesis of Bulk Quantities of Highly Enriched 13C-Graphene Materials for Biological and Safety Applications

The preparation of bulk quantities of 13C-labeled graphene materials is relevant for basic investigations and for practical applications. In addition, 13C-labeled graphene materials can be very useful in biological and environmental studies, as they may allow the detection of graphene or its derivatives in cells or organs. In this paper, we describe the synthesis of 13C-labeled graphene materials (few-layer graphene, FLG, and graphene oxide, GO) on a tens of mg scale, starting from 13C-labeled methane to afford carbon fibers, followed by liquid-phase exfoliation (FLG) or oxidation (GO). The materials have been characterized by several analytical and microscopic techniques, including Raman and nuclear magnetic resonance spectroscopies, thermogravimetric analysis, X-ray photoelectron spectroscopy, and X-ray powder diffraction. As a proof of concept, the distribution of the title compounds in cells has been investigated. In fact, the analysis of the 13C/12C ratio with isotope ratio mass spectrometry (IRMS) allows the detection and quantification of very small amounts of material in cells or biological compartments with high selectivity, even when the material has been degraded. During the treatment of 13C-labeled FLG with HepG2 cells, 4.1% of the applied dose was found in the mitochondrial fraction, while 4.9% ended up in the nuclear fraction. The rest of the dose did not enter into the cell and remained in the plasma membrane or in the culture media.La preparación de cantidades a granel de materiales de grafeno marcados con 13C es relevante para investigaciones básicas y para aplicaciones prácticas. Además, los materiales de grafeno marcados con 13C pueden ser muy útiles en estudios biológicos y medioambientales, ya que pueden permitir la detección de grafeno o sus derivados en células u órganos. En este trabajo describimos la síntesis de materiales de grafeno marcados con 13C (grafeno de pocas capas, FLG, y óxido de grafeno, GO) a escala de decenas de mg, partiendo de metano marcado con 13C para obtener fibras de carbono, seguidas de exfoliación en fase líquida (FLG) u oxidación (GO). Los materiales se han caracterizado mediante varias técnicas analíticas y microscópicas, como las espectroscopias Raman y de resonancia magnética nuclear, el análisis termogravimétrico, la espectroscopia de fotoelectrones de rayos X y la difracción de rayos X en polvo. Como prueba de concepto, se ha investigado la distribución de los compuestos del título en las células. De hecho, el análisis de la relación 13C/12C con espectrometría de masas de relación isotópica (IRMS) permite la detección y cuantificación de cantidades muy pequeñas de material en células o compartimentos biológicos con alta selectividad, incluso cuando el material se ha degradado. Durante el tratamiento de FLG marcado con 13C con células HepG2, el 4,1% de la dosis aplicada se encontró en la fracción mitocondrial, mientras que el 4,9% acabó en la fracción nuclear. El resto de la dosis no entró en la célula y permaneció en la membrana plasmática o en el medio de cultivo

Carbon nanotube-Cu hybrids enhanced catalytic activity in aqueous media

V. González, O. Martín and J. Baselga wish to thank Ministerio de Economía y Competitividad for funding through Grant MAT2010-17091. Authors also wish to thank to Sofía M. Vega for XPS measurements, Juan P. Fernández for TGA measurements and Lakshmy Pulickal Rajukumar for EDX measurements. C. Martín-Alberca thanks the University of Alcalá for his pre-doctoral Grant

Nanocomposites de titane et graphène pour le traitement d'eaux

[ES] La presente invención se refiere a un procedimiento para la fabricación de fotocatalizadores híbridos o nanocomposites constituidos por nanopartículas de óxido de titanio y grafeno de pocas capas (del inglés few-layer graphene, FLG), con propiedades catalíticas para fotodegradar contaminantes orgánicos en disoluciones acuosas. Esta invención se encuadra perfectamente dentro de los sectores de la química y la tecnología química, y pertenece el campo de la ingeniería ambiental, concretamente su aplicación consistirá en el tratamiento de efluentes acuosos contaminados con herbicidas y pesticidas.[EN] The present invention relates to a method for manufacturing hybrid photocatalysts or nanocomposites comprising titanium oxide and few-layer graphene nanoparticles with catalytic properties for the photodegradation of organic pollutants in aqueous solutions. Said invention fits perfectly in the chemical and chemical technology sectors and belongs to the field of environmental engineering; specifically, the application thereof will involve the treatment of aqueous effluents contaminated with herbicides and pesticides.[FR] La présente invention concerne un procédé pour la fabrication de photocatalyseurs hybrides ou de nanocomposites constitués de nanoparticules d'oxyde de titane et de graphène à faibles couches (de l'anglais few-layer graphene, FLG), présentant des propriétés catalytiques pour photodégrader des contaminants organiques dans des dissolutions aqueuses. L'invention s'inscrit parfaitement dans les secteurs de la chimie et de la technologie chimique, et appartient au domaine de l'ingénierie environnementale, concrètement son application consiste en le traitement d'effluents aqueux contaminés par des herbicides et des pesticides.NoConsejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid, Universidad de Castilla La ManchaA1 Solicitud de patente con informe sobre el estado de la técnic

Titanium and graphene nanocomposites for water treatment

[ES] Nanocomposites de titanio y grafeno para tratamiento de aguas. La presente invención se refiere a un procedimiento para la fabricación de fotocatalizadores híbridos o nanocomposites constituidos por nanopartículas de óxido de titanio y grafeno de pocas capas (del inglés few-layer graphene, FLG), con propiedades catalíticas para fotodegradar contaminantes orgánicos en disoluciones acuosas. Esta invención se encuadra perfectamente dentro de los sectores de la química y la tecnología química, y pertenece al campo de la ingeniería ambiental, concretamente su aplicación consistirá en el tratamiento de efluentes acuosos contaminados con herbicidas y pesticidas.[EN] Titanium and graphene nanocomposites for water treatment. The present invention relates to a process for the manufacture of hybrid photocatalysts or nanocomposites made up of nanoparticles of titanium oxide and few-layer graphene (FLG), with catalytic properties to photodegrade organic pollutants in aqueous solutions. This invention fits perfectly within the sectors of chemistry and chemical technology, and belongs to the field of environmental engineering, specifically its application will consist of the treatment of aqueous effluents contaminated with herbicides and pesticides.NoUniversidad de Castilla La Mancha, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de MadridA1 Solicitud de patente con informe sobre el estado de la técnic