Fabrication And Biological Applications Of Graphene-Based Nanostructures

Graphene received increasing attention for sensing and biomedical applications due to its properties. However, the current production methods are resource consuming, struggle to integrate these films into devices, and hardly produce graphene nanostructures (GN) that improve desired film properties like surface area and reactivity. This thesis aims to use a plasma-enhanced technique to produce GN and to explore their potential biological applications. The control of GN using the plasma-enhanced chemical vapour deposition (PECVD) was investigated. Growth parameters were related with the nanostructures properties as well as to the occurrence of the chemical-free transfer (CFT). The ability of GN to induce cellular response was investigated. The biocompatibility of GN was tested and found to be able to support fibroblasts viability at or above 70%. Cell proliferation was correlated to the density of different GN. While the density of horizontal GN had no influence on cell viability, a higher density of vertical GN yielded higher levels of cell viability. Furthermore, proliferation assays showed the ability of the GN surfaces to support bone-cells adhesion and growth. We also demonstrated improvement on mineral deposition that indicates the capability of GN to induce cell differentiation via morphological cues. The GN were also used for biosensing, where different morphologies were optimized to provide extras binding. Horizontal and vertical GN were produced by PECVD and assembled into electrodes via the CFT. The electrochemical sensing shows that both nanostructures perform highly selective measurements with a low limit of detection (picomolar) in a complex biological environment. Furthermore, the sensitivity relied on the density of the GN. This work suggests that plasma techniques are a feasible solution for the production challenges and graphene-based nanostructures are promising for biological applications

Mid-infrared surface sensing based ontTwo-dimensional materials

(English) Mid-infrared (mid-IR) spectroscopy in the wavelength region between 2 and 20 µm is a powerful technique to identify vibrational absorption signatures of molecules, finding in this way extensive applications in healthcare, environmental monitoring, and chemical analysis. Enhanced IR light-molecules interactions can be achieved by exploiting nanostructured surfaces supporting polaritons – hybrid excitations of light and dipolar elements of matter. Recently, polaritons of two-dimensional van der Waals (2D-vdW) materials unveiled a vibrant playground for mid-IR spectroscopy as they possess remarkable properties such as light trapping at deep nanoscale. This dissertation aims to investigate 2D-vdW materials for technological sensing applications. Hence, we explore the mid-IR sensing performance of nanostructures of widely studied 2D-vdW crystals: graphene (the pioneering vdW material with tunable plasmon polaritons) and hexagonal boron nitride (hBN, sustaining ultralow-loss phonon polaritons). Relevant functionalization layers, such as polymer adsorber and antibodies, are combined with the 2D-vdW nanostructures to create gas and for bio-molecular sensors, respectively. Here, we present three main experimental works of 2D-vdW-based mid-IR molecular sensing. First, we investigate the CO2 detection using graphene nanoribbons functionalized with ultrathin CO2-chemisorbing polyethylenimine (PEI). The localized surface plasmon resonance (LSPR) of graphene is modulated by varying CO2 gas concentration, whose substantial shifts are influenced by the reversible PEI-induced doping of graphene. Second, we examine the phonon-enhanced CO2 detection of hBN nanoresonators functionalized with thin PEI layer. The phonon-polariton resonance is modulated by varying CO2 levels with high signal-to-noise ratio signals. Third, we present a quantitative bioassay by transducing different vitamin B12 target concentrations into LSPR shifts of bio-functionalized graphene nanostructures (subsequent addition of pyrene linkers and recombinant anti-vB12 antibody fragments). Additionally, we observed the same result-trends for the same bioassay using graphene nanostructures fabricated both by small-scale (i.e., electron beam lithography) and large-scale (i.e., nanoimprint lithography) methods. Our proof-of-concept mid-IR sensing experiments show quantitative results for the detection of gas and biomarker with functionalized 2D-vdW nanostructures. The opportunity of combining the mid-IR spectroscopy with industrially large-scale 2D-vdW nanostructures (e.g., nanoimprinted GNH in this dissertation) would enable cost-effective technologies in future developments. This dissertation contributes to the field of 2D-vdW-based mid-IR spectroscopic sensors towards exploring novel designs and improved sensitivity, which eventually could lower the limit of detection for molecular analytes in various applications.(Español) La espectroscopia infrarroja de onda media (mid-IR en inglés) en el rango óptico entre 2 y 20 µm es una potente técnica para identificar las huellas vibracionales de las moléculas, permitiendo así su uso en múltiples aplicaciones como salud, monitoreo medioambiental y análisis químico. Aumentar las interacciones luz-molécula en el IR es posible explotando superficies nano-estructuradas que soportan polaritones – excitaciones hibridas entre la luz y dipolos en la materia. Recientemente, polaritones en materiales bidimensionales de van der Waals (2D-vdW) han revelado un escenario interesante para la espectroscopia en el mid-IR, ya que poseen propiedades remarcables como la de confinar la luz a escala nanométrica. Esta tesis pretende investigar materiales 2D-vdW para su uso tecnológico en aplicaciones de detección. De esta manera, exploramos el rendimiento de la detección en el mid-IR de nanoestructuras de cristales 2D-vdW ampliamente estudiados: grafeno (el material vdW pionero con plasmones-polaritones sintonizables) y el nitruro de boro hexagonal (hBN, que soporta fonones-polaritones con muy bajas perdidas). Capas adicionales para la funcionalización, como polímeros absorbentes y anticuerpos, son combinadas con las nanoestructuras 2D-vdW para crear sensores de gas y biomoleculares, respectivamente. Aquí presentamos tres principales trabajos experimentales para la detección de moléculas con materiales 2D-vdW en el mid-IR. Primero, investigamos la detección de CO2 usando nanoribons de grafeno funcionalizado con una capa ultrafina de polietilenimina (PEI), dada su quimisorción de CO2. La resonancia de plasmón de superficie localizada (LSPR) del grafeno es modulada variando la concentración del CO2, cuyos desplazamientos dependen de un efecto de dopaje quimico reversible inducido por el PEI. Después, examinamos la detección realzada de CO2 con fonones a partir de nanoresonadores de hBN funcionalizados con una capa fina de PEI. La resonancia fonón-polaritón es modulada variando los niveles de CO2 con una gran relación señal/ruido. Finalmente, presentamos un bioensayo cuantitativo a partir de la transducción de distintas concentraciones de vitamina B12 a desplazamientos de LSPR con nanoestructuras bio-funcionalizadas de grafeno (con la posterior adición de enlazadores de pireno y anticuerpos fragmentos de recombinante anti-vB12) Adicionalmente, observamos la misma tendencia de resultados para el mismo bioensayo usando nanoestructuras de grafeno fabricadas con métodos no escalables (i.e., litografía por haz de electrones) y escalable (i.e., litografía por nanoimpresión). Nuestras pruebas de concepto con experimentos de detección con luz mid-IR muestran resultados cuantitativos para la detección de gas y biomarcadores con nanoestructuras 2D-vdW funcionalizadas. La oportunidad de poder combinar la espectroscopia mid-IR con nanoestructuras de materiales 2D-vdW industrialmente escalables (ej., GNH via nanoimpresión en esta tesis) podrían permitir desarrollar tecnologías rentables en el futuro. Esta tesis pretende contribuir en el campo de los sensores para espectroscopia mid-IR basados en materiales 2D-vdW, explorando novedosos diseños y mejorando su sensibilidad, los cuales podrían eventualmente reducir el límite de detección para analitos moleculares en varias aplicaciones.Fotònic

Mid-infrared surface sensing based ontTwo-dimensional materials

(English) Mid-infrared (mid-IR) spectroscopy in the wavelength region between 2 and 20 µm is a powerful technique to identify vibrational absorption signatures of molecules, finding in this way extensive applications in healthcare, environmental monitoring, and chemical analysis. Enhanced IR light-molecules interactions can be achieved by exploiting nanostructured surfaces supporting polaritons – hybrid excitations of light and dipolar elements of matter. Recently, polaritons of two-dimensional van der Waals (2D-vdW) materials unveiled a vibrant playground for mid-IR spectroscopy as they possess remarkable properties such as light trapping at deep nanoscale. This dissertation aims to investigate 2D-vdW materials for technological sensing applications. Hence, we explore the mid-IR sensing performance of nanostructures of widely studied 2D-vdW crystals: graphene (the pioneering vdW material with tunable plasmon polaritons) and hexagonal boron nitride (hBN, sustaining ultralow-loss phonon polaritons). Relevant functionalization layers, such as polymer adsorber and antibodies, are combined with the 2D-vdW nanostructures to create gas and for bio-molecular sensors, respectively. Here, we present three main experimental works of 2D-vdW-based mid-IR molecular sensing. First, we investigate the CO2 detection using graphene nanoribbons functionalized with ultrathin CO2-chemisorbing polyethylenimine (PEI). The localized surface plasmon resonance (LSPR) of graphene is modulated by varying CO2 gas concentration, whose substantial shifts are influenced by the reversible PEI-induced doping of graphene. Second, we examine the phonon-enhanced CO2 detection of hBN nanoresonators functionalized with thin PEI layer. The phonon-polariton resonance is modulated by varying CO2 levels with high signal-to-noise ratio signals. Third, we present a quantitative bioassay by transducing different vitamin B12 target concentrations into LSPR shifts of bio-functionalized graphene nanostructures (subsequent addition of pyrene linkers and recombinant anti-vB12 antibody fragments). Additionally, we observed the same result-trends for the same bioassay using graphene nanostructures fabricated both by small-scale (i.e., electron beam lithography) and large-scale (i.e., nanoimprint lithography) methods. Our proof-of-concept mid-IR sensing experiments show quantitative results for the detection of gas and biomarker with functionalized 2D-vdW nanostructures. The opportunity of combining the mid-IR spectroscopy with industrially large-scale 2D-vdW nanostructures (e.g., nanoimprinted GNH in this dissertation) would enable cost-effective technologies in future developments. This dissertation contributes to the field of 2D-vdW-based mid-IR spectroscopic sensors towards exploring novel designs and improved sensitivity, which eventually could lower the limit of detection for molecular analytes in various applications.(Español) La espectroscopia infrarroja de onda media (mid-IR en inglés) en el rango óptico entre 2 y 20 µm es una potente técnica para identificar las huellas vibracionales de las moléculas, permitiendo así su uso en múltiples aplicaciones como salud, monitoreo medioambiental y análisis químico. Aumentar las interacciones luz-molécula en el IR es posible explotando superficies nano-estructuradas que soportan polaritones – excitaciones hibridas entre la luz y dipolos en la materia. Recientemente, polaritones en materiales bidimensionales de van der Waals (2D-vdW) han revelado un escenario interesante para la espectroscopia en el mid-IR, ya que poseen propiedades remarcables como la de confinar la luz a escala nanométrica. Esta tesis pretende investigar materiales 2D-vdW para su uso tecnológico en aplicaciones de detección. De esta manera, exploramos el rendimiento de la detección en el mid-IR de nanoestructuras de cristales 2D-vdW ampliamente estudiados: grafeno (el material vdW pionero con plasmones-polaritones sintonizables) y el nitruro de boro hexagonal (hBN, que soporta fonones-polaritones con muy bajas perdidas). Capas adicionales para la funcionalización, como polímeros absorbentes y anticuerpos, son combinadas con las nanoestructuras 2D-vdW para crear sensores de gas y biomoleculares, respectivamente. Aquí presentamos tres principales trabajos experimentales para la detección de moléculas con materiales 2D-vdW en el mid-IR. Primero, investigamos la detección de CO2 usando nanoribons de grafeno funcionalizado con una capa ultrafina de polietilenimina (PEI), dada su quimisorción de CO2. La resonancia de plasmón de superficie localizada (LSPR) del grafeno es modulada variando la concentración del CO2, cuyos desplazamientos dependen de un efecto de dopaje quimico reversible inducido por el PEI. Después, examinamos la detección realzada de CO2 con fonones a partir de nanoresonadores de hBN funcionalizados con una capa fina de PEI. La resonancia fonón-polaritón es modulada variando los niveles de CO2 con una gran relación señal/ruido. Finalmente, presentamos un bioensayo cuantitativo a partir de la transducción de distintas concentraciones de vitamina B12 a desplazamientos de LSPR con nanoestructuras bio-funcionalizadas de grafeno (con la posterior adición de enlazadores de pireno y anticuerpos fragmentos de recombinante anti-vB12) Adicionalmente, observamos la misma tendencia de resultados para el mismo bioensayo usando nanoestructuras de grafeno fabricadas con métodos no escalables (i.e., litografía por haz de electrones) y escalable (i.e., litografía por nanoimpresión). Nuestras pruebas de concepto con experimentos de detección con luz mid-IR muestran resultados cuantitativos para la detección de gas y biomarcadores con nanoestructuras 2D-vdW funcionalizadas. La oportunidad de poder combinar la espectroscopia mid-IR con nanoestructuras de materiales 2D-vdW industrialmente escalables (ej., GNH via nanoimpresión en esta tesis) podrían permitir desarrollar tecnologías rentables en el futuro. Esta tesis pretende contribuir en el campo de los sensores para espectroscopia mid-IR basados en materiales 2D-vdW, explorando novedosos diseños y mejorando su sensibilidad, los cuales podrían eventualmente reducir el límite de detección para analitos moleculares en varias aplicaciones.Postprint (published version

Sustainable Devices by Design: Thermal- and Plasma-Enabled Nanofabrication of Hierarchical Carbon Nanostructures for Bioelectronics and Supercapacitors

Graphene is promising to enable diverse technological advancements. However, major technical challenges arise in its fabrication and integration as active functional materials. This body of work exemplifies a host of thermal- and plasma-enabled techniques, designed to realize sustainable and controlled methodologies for nano-assembly. Importantly, these techniques may be tailored and broadly incorporated to harness the unique functional properties of graphene, and a host of other hierarchical nanomaterials. Together, these concepts may pave the realization of next-generation nanotechnologies which hold promise for a sustainable future

Nanomaterials for Healthcare Biosensing Applications

In recent years, an increasing number of nanomaterials have been explored for their applications in biomedical diagnostics, making their applications in healthcare biosensing a rapidly evolving field. Nanomaterials introduce versatility to the sensing platforms and may even allow mobility between different detection mechanisms. The prospect of a combination of different nanomaterials allows an exploitation of their synergistic additive and novel properties for sensor development. This paper covers more than 290 research works since 2015, elaborating the diverse roles played by various nanomaterials in the biosensing field. Hence, we provide a comprehensive review of the healthcare sensing applications of nanomaterials, covering carbon allotrope-based, inorganic, and organic nanomaterials. These sensing systems are able to detect a wide variety of clinically relevant molecules, like nucleic acids, viruses, bacteria, cancer antigens, pharmaceuticals and narcotic drugs, toxins, contaminants, as well as entire cells in various sensing media, ranging from buffers to more complex environments such as urine, blood or sputum. Thus, the latest advancements reviewed in this paper hold tremendous potential for the application of nanomaterials in the early screening of diseases and point-of-care testing

Self-Assembling Peptides and Carbon Nanomaterials Join Forces for Innovative Biomedical Applications

Self-assembling peptides and carbon nanomaterials have attracted great interest for their respective potential to bring innovation in the biomedical field. Combination of these two types of building blocks is not trivial in light of their very different physico-chemical properties, yet great progress has been made over the years at the interface between these two research areas. This concise review will analyze the latest developments at the forefront of research that combines self-assembling peptides with carbon nanostructures for biological use. Applications span from tissue regeneration, to biosensing and imaging, and bioelectronics

Electrochemical CO₂ Reduction to CO Catalyzed by 2D Nanostructures

Electrochemical CO₂ reduction towards value-added chemical feedstocks has been extensively studied in recent years to resolve the energy and environmental problems. The practical application of electrochemical CO₂ reduction technology requires a cost-effective, highly efficient, and robust catalyst. To date, vigorous research have been carried out to increase the proficiency of electrocatalysts. In recent years, two-dimensional (2D) graphene and transition metal chalcogenides (TMCs) have displayed excellent activity towards CO₂ reduction. This review focuses on the recent progress of 2D graphene and TMCs for selective electrochemical CO₂ reduction into CO

Graphene-Paper Based Electrochemical Sensors

Graphene paper as a new form of graphene-supported nanomaterials has received worldwide attention since its first report in 2007. Due to their high flexibility, lightweight and good electrical conductivity, graphene papers have demonstrated the promising potential for crucial applications in electrochemical sensors and energy technologies among others. In this chapter, we present some examples to overview recent advances in the research and development of two-dimensional (2D) graphene papers as new materials for electrochemical sensors. The chapter covers the design, fabrication, functionalization and application evaluations of graphene papers. We first summarize the mainstream methods for fabrication of graphene papers/membranes, with the focus on chemical vapour deposition techniques and solution-processing assembly approaches. A large portion of this chapter is then devoted to the highlights of specific functionalization of graphene papers with polymer and nanoscale functional building blocks for electrochemical-sensing purposes. In terms of electrochemical-sensing applications, the emphasis is on enzyme-graphene and nanoparticle-graphene paper-based systems for the detection of glucose. We finally conclude this chapter with brief remarks and outlook

Recent Progress in Optical Sensors for Biomedical Diagnostics

In recent years, several types of optical sensors have been probed for their aptitude in healthcare biosensing, making their applications in biomedical diagnostics a rapidly evolving subject. Optical sensors show versatility amongst different receptor types and even permit the integration of different detection mechanisms. Such conjugated sensing platforms facilitate the exploitation of their neoteric synergistic characteristics for sensor fabrication. This paper covers nearly 250 research articles since 2016 representing the emerging interest in rapid, reproducible and ultrasensitive assays in clinical analysis. Therefore, we present an elaborate review of biomedical diagnostics with the help of optical sensors working on varied principles such as surface plasmon resonance, localised surface plasmon resonance, evanescent wave fluorescence, bioluminescence and several others. These sensors are capable of investigating toxins, proteins, pathogens, disease biomarkers and whole cells in varied sensing media ranging from water to buffer to more complex environments such as serum, blood or urine. Hence, the recent trends discussed in this review hold enormous potential for the widespread use of optical sensors in early-stage disease prediction and point-of-care testing devices.DFG, 428780268, Biomimetische Rezeptoren auf NanoMIP-Basis zur Virenerkennung und -entfernung mittels integrierter Ansätz

Exfoliation solvent dependent plasmon resonances in two-dimensional sub-stoichiometric molybdenum oxide nanoflakes

Few-layer two-dimensional (2D) molybdenum oxide nanoflakes are exfoliated using a grinding assisted liquid phase sonication exfoliation method. The sonication process is carried out in five different mixtures of water with both aprotic and protic solvents. We found that surface energy and solubility of mixtures play important roles in changing the thickness, lateral dimension, and synthetic yield of the nanoflakes. We demonstrate an increase in proton intercalation in 2D nanoflakes upon simulated solar light exposure. This results in substoichiometric flakes and a subsequent enhancement in free electron concentrations, producing plasmon resonances. Two plasmon resonance peaks associated with the thickness and the lateral dimension axes are observable in the samples, in which the plasmonic peak positions could be tuned by the choice of the solvent in exfoliating 2D molybdenum oxide. The extinction coefficients of the plasmonic absorption bands of 2D molybdenum oxide nanoflakes in all samples are found to be high (Îμ > 109 L mol-1 cm-1). It is expected that the tunable plasmon resonances of 2D molybdenum oxide nanoflakes presented in this work can be used in future electronic, optical, and sensing devices