Màster Oficial - Nanociència i Nanotecnologia

URI permanent per a aquesta col·leccióhttps://hdl.handle.net/2445/9802

Treballs Finals del Màster en Nanociència i Nanotecnologia de la Facultat de Física de la Universitat de Barcelona.

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Propelling magnetic colloidal carpets on a periodic structured landscape
(2019-07) Rodríguez Gallo, Carolina; Tierno, Pietro; Massana-Cid, Helena
Microswimmers are artificial microscopic entities able to propel in viscous fluids and have the ability to perform tasks at the microscale. This capacity allows to impact many scientific areas such as micromanipulation, lab-on-a-chip devices or targeted drug delivery. In this study, optical video microscopy was used to examine propelled paramagnetic colloidal carpets. First, previous results were reproduced by sliding carpets on top of a flat substrate. In order to investigate more complex situations as the one occurring in natural systems, a different substrate was used. We have slid carpets on top of a periodic structured landscape, namely a two-dimensional colloidal crystal, composed of silica particles. We observe the emergence of novel phenomena when external and time dependent magnetic fields are applied over a colloidal paramagnetic carpet driven across a periodic structured landscape. Stair-like trajectories, periodic oscillations and spontaneous reorientations of the carpet were observed. Also, the comparison of the average speed of the carpet on top of a flat substrate and on a patterned substrate is reported
EELS techniques towards characterizing and mapping iron valence states in iron oxide samples
(2019-07) Sospedra Ramírez, Joan; Estradé Albiol, Sònia; Blanco Portals, Javier
In this work a sample of iron oxide nanoparticles is studied with a variety of techniques. In order to map its oxidation states, a characterization through indexing its crystallographic structure is attempted, but it is an EELS big data treatment through model creation of individual components in conjunction with clustering what will ultimately reveal a distribution map of different oxidation states across the sample
Synthesis and functionalization of iron oxide nanoparticles for targeted cancer therapy
(2019-07) Gabarró Riera, Guillem; Sañudo Zotes, Eva Carolina; Ciudad i Gómez, Carlos Julián
Over the last decades, nanoparticles as drug carriers have attracted a lot of attention as potential systems for targeted drug delivery. Their tunable size and properties have opened a wide variety of possibilities to design future drug vehicles. On the other hand, Polypurine Reverse Hoogsteen Hairpins (PPRHs) molecules are DNA hairpins bound via Hoogsteen bonds. The PPRHs can bind by Watson-Crick bonds to the desired DNA sequence. In this particular case, the PPRHs are synthetized to act against the survivin production, which is an antiapoptotic protein, so its inhibition provokes cellular apoptosis, as it has already been proved and reported in literature. In this work, a new system for targeted cancer therapy is presented from the combination of superparamagnetic iron oxide nanoparticles (SPIONs) and the PPRHs. Monodisperse SPIONs are synthetized and functionalized with dopamine, hyaluronic acid and PPRHs. Dopamine acts as an anchor to the nanoparticle, whereas hyaluronic acid is a known ligand to the CD44 receptor, apart from preventing the SPIONs to agglomerate. The paramagnetic behavior of these nanoparticles, along with their tunable size, makes them a very promising system for future cancer treatments
Preparation and Characterisation of Self-Assembled Dye Fibers
(2019-07) Fruh, Maxime; Rodríguez Abreu, Carlos
Two types of fibers have been prepared by self-assembly. The first system is made of Astrophloxine hydrogel fibers, based on the stacking of molecules by π- π interactions. Various properties of the hydrogel have been characterized with UV-vis absorbance, Fluorescence spectroscopy, calorimetric profiles, and rheology. The hydrogel shows temperature-dependent fluorescence. Above the melting temperature T>44°C, fluorescence and hydrogel structure are lost, but they are recovered upon cooling, demonstrating that the process is reversible. The fibers also showed a temperature-dependent birefringency. The second system of fibers was formed by ionic self-assembly (ISA) of two oppositely charged dyes. This system was characterized by SEM and TEM, as well as X-Ray diffraction. The ISA fibers were able to encapsulate a drug, showing promise for controlled drug release
A Mathematical Model of an Angiogenic Process
(2019-07) Ferre Torres, Josep; Hernández Machado, Aurora
Tubular growth of blood vessels in 2-dimensional space is described in the present study by using a phase field model. In contrast with previous studies, we propose a biomechanical model based on Canham-Helfrich energy, coupled to an angiogenic agent through a spontaneous curvature term. The concentration of this angiogenic agent is static and non uniform, generating a wellde fined gradient through time. The model is very compact consisting of only one partial differential equation, and has the clear advantage of a reduced number of parameters. Following a phase-field methodology, this model allows us to relate sprout growth with the spontaneous curvature term from the Canham-Helfrich model. The importance of the capillary shape at the initial conditions has also been addressed. Additionally, capillaries grown on other growing capillaries have been obtained by combining multiple distributions of growth factor
Fabrication and characterization of carbon-based nanostructured electrodes for Microbial Fuel Cells (MFCs)
(2019-07) Fernández-Martín, Miguel; Amade Rovira, Roger; Bertrán Serra, Enric
Microbial Fuel Cells (MFCs) are bioelectrochemical systems that can produce bioelectricity from organic matter. Wastewater from urban, domestic or industrial origin can be used as a fuel to produce electricity. In addition, the amount of pollutants and contaminants decreases during the production of bioelectricity. Thus, such bioelectrochemical systems produce renewable energy and, simultaneously, can be used as a novel technology for wastewater treatment. However, the efficiencies obtained are still too low and the output voltage of the MFCs need to be increased. Furthermore, the overall cost of the cell must be reduced in order to promote this technology into the market. Here, we have studied the growth of graphene nanowalls (GNWs) on stainless-steel substrate 304 (SS), which can be used as electrodes in air-cathode MFCs. Growth parameters have been optimized to obtain dense carbon nanostructures on both SS foil and mesh. MFCs with different electrodes have been prepared to study the effect of different parameters and to determine whether the presence of carbon nanostructures results in an increase of the electrochemical efficiency. An oxygen plasma treatment has been performed to study its effect on the properties of the electrodes. Finally, MnO2 has been electrochemically deposited to determine its catalytic effect in the oxygen reduction reaction (ORR) that takes place on the cathode. Results show an increase in the output voltage and power density when GNWs electrodes are compared to MnO2 bare electrodes, with a maximum power density of 9 mW/m2. Moreover, the influence of the oxygen plasma post-treatment, performed on the nanostructures, over microbial communities developed as biofilm in the anode is demonstrated. Overall, this study shows the potential of GNWs to increase the yield of MFCs
Assessment of magnetic properties of iron oxide core/shell nanocubes through Electron Magnetic Circular Dichroism
(2019-01) Pozo Bueno, Daniel del; Estradé Albiol, Sònia; Peiró Martínez, Francisca
Electron magnetic circular dichroism (EMCD) is a novel technique used for the magnetic characterization at the nanoscale using the electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM). The EMCD is analogous to the X-ray magnetic circular dichroism technique (XMCD). However, this technique offers some bene ts in comparison with XMCD, such as the high spatial resolution at which the magnetic information of the sample is obtained, and magnetic depth sensitivity of the whole sample. In this master thesis, the EMCD technique was used to study magnetic nanocubes with a core/shell structure, formed by an iron II oxide core (FeO) covered by a magnetite shell (Fe3O4). The EMCD experiments were carried out using an intrinsic two-beam conditions as a scattering configuration to perform the experiment. In these Fe3O4/FeO nanocubes, it is imperative to probe the dichroic signal from the core and shell regions separately, in order to characterize the magnetic properties of the magnetite shell. For this purpose, EEL spectra were classified using data mining algorithms. Once both contributions were separated, the dichroic signal from both core and shell were obtained. Also, the spin magnetic moment ratio mL/mS is calculated for the magnetic shell. The difference in the dichroic signal between EMCD experiments carried out at room and low temperature are discussed
3D printing of hydrogels and nanoparticle containing bio-inks for bone tissue regeneration
(2019-01) Barakat, Abeer; García-Torres, José Manuel; Ginebra, Maria Pau
In tissue engineering, biomaterials paves the route for faster and less painful regeneration of tissues. In the present study, 2 set of scaffolds made of mixtures of different proportions of low and medium molecular weight alginates with and without hydroxyapatite nanoparticles (HA NPs) were prepared by 3D printing for bone regeneration. Different tests were done to characterize the scaffolds. Printability of scaffolds, SEM analysis were performed to characterize printed scaffolds of the desired design. Biodegradation studies of the scaffolds as well as cell viability in 3D culture were performed. All the formulations with different alginates proportions (with and without HA NPs) were printable. SEM showed the intact scaffold with well-defined filaments showing porous spongy structure with homogeneously distributed components. Biodegradation analyses showed complete degradation of the scaffolds within 14 to 21 days depending on the composition. Cell viability analysis revealed 95 to 100%viability of cells after 28 days
First-principles study of NOx and SO2 adsorption onto SnO2(110) and SnO2 nanoparticles
(2007-07) Prades García, Juan Daniel; Cirera Hernández, Albert
An ab initio study of the adsorption of NOx and SO2 onto SnO2(110) surfaces is presented and related to gas-sensing applications. Using first-principles calculations (DFT-GGA approximation) the most relevant NO and NO2 adsorptions are analyzed by estimating their adsorption energies and charge transfers. The resulting values are compared with experimental desorption temperatures for NO and NO2. The adsorption of the poisoning agent SO2 is also analyzed. Optimum SnO2 working temperatures for minimum SO2 poisoning in NO2 sensing applications are discussed from the perspective of adsorption. In all cases, we observe that the surface reduction state has noticeable consequences on adsorption strength. We also present an ab initio thermodynamics study to analyze the stability of several surface reduction configurations with respect to the ambient oxygen partial pressure and the temperature of the material. Finally, the interaction of NO2 with spherical SnO2 nanoparticles smaller than 2nm is considered.
Design, fabrication and characterization of Si nanopillars-based photonic crystal for mechanical sensing
(2018-11) López Aymerich, Elena; Romano Rodríguez, Albert
In this work the first results of the experimental implementation of silicon nanopillars hexagonal arrays acting as photonic crystals with the aim of their use as force sensors are presented. The starting point are two previous bachelor and master thesis that have shown the theoretical potentialities of such a structure acting as a photonic crystal and as a mechanical sensor due to deflection of the nanopillars. Here we present the optimization of the fabrication procedure of these nanostructures, based on a sequence of complex processes carried out in Clean-Room environment, and the support of simulations and morphological analysis via Scanning Electron Microscopy and the results obtained from Fourier Transform Infra-Red spectroscopy characterisation match the simulations of the photonic crystal, with bandgaps in the near infrared range, and pave the way in the use of such structures for mechanical testing in biomedical applications.
Magnetically actuated rod-shaped nanoswimmers
(2018-07) Vila Figueirido, Jordán; Tierno, Pietro; García-Torres, José
The idea of creating and controlling very small autonomous devices or nanorobots, which are able to move and operate at such very small scales looks like science fiction. However, this idea may not be that far, many nanoswimming devices are being developed and the challenges of the propulsion in liquid environments at low Reynolds conditions are being overcome. Here, two types of magnetic nanorod-shaped nanoswimmers are realized, one consists only on a nickel nanorod and the other is a nickel-polypyrrole bi-segment nanorod. These nanorods have been actuated using oscillating and rotating magnetic fields and two main types of propulsion mechanisms have been reported, surface walking and flexible undulatory propulsion. An effective control of their speed and direction has been demonstrated and high swimming velocities have been achieved (above 100 μm/s for Ni nanorods)
Phase behavior and formulation of structured drops in triphasic systems
(2018-07) Hervés Carrete, Carmen; Esquena Moret, Jordi; Rodríguez Abreu, Carlos
This work sets a first step towards the formulation of a two-domain drug carrier formed by an ATPS (Aqueous Two Phase System) of a solution of two biocompatible polymers, gelatin and poly(ethylene glycol) diacrylate (PEG-diAc), dispersed in an organic solvent. The main objectives of the work are the study of the phase behaviour and to achieve control over the morphology of the ATPS drops at micro and nanoscale by adjusting different parameters of the emulsification process, followed by optical microscopy
TEM characterization of advanced kesterite structures
(2018-07) Fonoll Rubio, Robert; Estradé Albiol, Sònia; Izquierdo Roca, Victor; Blanco Portals, Javier
In the present work, we study a kesterite Cu2ZnSnSe4 solar cell at the nanoscale level in order to analyze the defects that lower its energy conversion efficiency. First of all, current density{voltage characteristics, quan- tum effciency, photoluminiscence, and Raman spectroscopy are studied to obtain macroscopic and microscopic information about the device. Then, High Resolution Transmission Electron Microscopy (HRTEM) is performed to observe the cross-section and, for the first time, the front interface of the absorber with nanoscopic detail
Effect of rare earth on ZnO-based memristors
(2018-07) Bonet Isidro, Ferran; Hernández Márquez, Sergi; Blázquez Gómez, Josep Oriol
Memristors are electronic devices that present resistive switching. Their main application is the fabrication of digital memories. In this work Tb doped-ZnO based memristors are characterized and their properties are compared to the ones of undoped ZnO devices. The study shows that it is possible to obtain switching in doped ZnO-based devices at lower currents. Devices doped with rare earth ions also exhibit light emission, while preserving their resistive switching properties. This was not observed in the undoped devices and is an important advantage for developing optically read digital memories. Finally, the electrical conduction mechanisms present in the memristors are also analyzed
The role of cellular contractility in topography sensing on soft nanoporous polyacrylamide hydrogels
(2018-11) Rebollo Calderón, Beatriz; Comelles Pujadas, Jordi
Extracellular matrix physical characteristics have been shown to play an important role in cellular processes such as adhesion, migration, proliferation and differentiation. Of high importance are the stiffness and the topography of the extracellular matrix, which are believed to activate shared signalling pathways to cause a cellular response. In this work, we use polyacrylamide nanoporous hydrogels of different stiffness, both with and without microtopographical structures to see if these physical cues are truly sensed by the same mechanism, and an inhibitor of ROCK I to determine the role of cell contractility in the sensing of topography and stiffness
Synthesis and characterization of nanostructured and noble metal-based chalcogenide semiconductors
(2018-07) Lin, Mengxi; Figuerola i Silvestre, Albert
Platinum containing chalcogenides seem to have bright potential due to the special electrical and catalytic properties stemming from platinum combined with the semiconductor ones of chalcogenides. In this work, a set of synthesis were designed in order to know the influence of different reaction parameters such as temperature, amount of reactants and also different kinds of capping agents on the growth or formation of such nanostructures. The characterization results suggest that a ternary nanostructured chalcogenide system containing two noble metals (Platinum and Silver) was successfully synthesised by using OlAm as capping agent at 120ºC by means of cation exchange reactions. Furthermore, the composition of this ternary is assumed to be Ag3PtSe2. As described through this work, the variation on the previously mentioned reaction parameters allows modifying the morphology and composition of this ternary system. Additionally, the possibility of synthesizing nanostructured binary platinum selenide has also been explored
Optoelectronic device based on Rare Earths electroluminescence
(2017) Frieiro Castro, Juan Luis; Blázquez Gómez, Josep Oriol; Hernández Márquez, Sergi
In this Master Thesis, the fabrication and the structural, optical and electrical properties of Al/rare earth (RE)/Al/SiO2 and RE/SiO2 nanomultilayers have been studied. The nanomultilayers were deposited by means of e-beam evaporation on top of p-type Si substrates. Two different RE species were considered: Tb3+ and Eu3+ ions, as they exhibit a narrow and strong emission in the green and red spectral ranges, respectively. The main goal of the present work is achieving optical activation of those rare earth elements, and thus obtaining light emission from their intra-4f and 5d-to-4f shell transitions. Optical characterization indicates that optically active RE3+ ions had been successfully fabricated. The electrical and electroluminescence analysis yielded promising results to include this material in future applications of illumination and integrated emitting devices for optoelectronics.
High-pressure optical and vibrational properties of Ga2O3 nanocrystals
(2017) Moral Cejudo, Alberto del; Ibáñez i Insa, Jordi; Hernández Márquez, Sergi
In this project the optical and vibrational properties of monoclinic gallium oxide (β-Ga2O3) nanocrystals (NCs) are studied by Raman scattering spectroscopy under high-hydrostatic pressure conditions, from ambient pressure up to 21.6 GPa. Phonon pressure coefficients and Grüneisen parameters are obtained for different optical phonon modes of nanocrystalline β-Ga2O3. In the first part of the work, the investigated material is characterized by means of different techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman scattering. While XRD and SEM confirm the nanocrystalline nature of the investigated sample, from the Raman spectra we are able to properly identify the Raman-active modes of β-Ga2O3 at ambient pressure. By monitoring their peak position at different pressures, phonon pressure coefficients for several of the optical Raman-active modes of β-Ga2O3 have been successfully determined, with values significantly lower than those reported in previous works for bulk β-Ga2O3. This suggests that the compressibility of the NCs could be reduced with respect to the bulk material. In order to test the validity of the experimental data, density functional theory calculations of the structural properties of bulk β-Ga2O3 have also been performed as a function of pressure. From the ab initio calculations we obtain a bulk modulus of 160.7 ± 5.0 GPa for bulk β-Ga2O3, which is comparable, and even lower, than that measured in previous works for bulk material by means of synchrotron XRD as a function of pressure (~ 200 GPa). Our theoretical results thus confirm that the lower compressibility of the β-Ga2O3 NCs studied in this work may be a consequence of the nanocrystalline nature of the investigated material. The possible physical mechanisms giving rise to this observation are discussed in terms of similar results reported in the literature. It is concluded that more work dealing with the high-pressure structural and vibrational properties of β-Ga2O3 samples of different origin (i.e., bulk vs. NCs, and doped vs. undoped material) should be performed in order to fully understand the origin of the lower compressibility displayed by the nanocrystalline β-Ga2O3 sample studied in this work.
Resistive switching in Al/Tb/SiO2 nano-multilayers
(2017) Doblas Moreno, Albert; Garrido Fernández, Blas; Blázquez Gómez, Josep Oriol
Resistive switching mechanism in memristors offers wide novel properties for nanoelectronics devices. In this work, we report an Al/Tb/SiO2 nano-multilayer memristor. Our devices were fabricated in terms of electron beam evaporation with thicknesses in the order of nanometres. Our devices exhibit memristive behaviour with a high change in resistance which can be cycled up to 20 times at room temperature. The states can persist at least for 140 h. We report bipolar switching with set and reset voltages with a low dispersion during the cycling. We have also studied the impact of the compliance current. Additionally, we studied which conduction mechanism is carrying out the memristive behaviour of our samples, where an Ohmic conduction in the low resistance state is observed and a Schottky fit is applied at the high resistance state. Current-time characteristics of the devices is also shown, where fluctuations and the time of commutation are presented. Finally, we also report the structural characterization of another type of samples, where only the switching mechanism is the aim of study. We have supposed that valence change mechanism is the responsible for the switching mechanism
Non-coherent transport in serial/parallel quantum dots in self-consistent eld regime
(2011-02-17T10:27:14Z) Illera Robles, Sergio; Cirera Hernández, Albert
In this work we introduce a simple phe- nomenological model of the conduction between a couple of serial or parallel quantum dots. This model is extended to an arbitrary of number and to a square array of quantum dots. The local potential is computed taking into account the net charge at the quantum dot. Master equations are presented for total current and charge number N considering both the local potential and the local current. Interesting results are reported, namely the Negative Di erential Resistance for serial quantum dots as well as resonant conductance. A paradoxical asymmetric current appears for the parallel case due to the capacitive coupling.

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