Formation and characterization of ultra-sensitive surface plasmon resonance sensor based upon a nano-scale corrugated multi-layered coated D-shaped optical fiber

We present experimental results on the performance of a series of coated, D-shaped optical fiber sensors that display high spectral sensitivities to external refractive index. Sensitivity to the chosen index regime and coupling of the fiber core mode to the surface plasmon resonance (SPR) is enhanced by using specific materials as part of a multi-layered coating. We present strong evidence that this effect is enhanced by post ultraviolet radiation of the lamellar coating that results in the formation of a nano-scale surface relief corrugation structure, which generates an index perturbation within the fiber core that in turn enhances the coupling. We have found reasonable agreement when we modeling the fiber device. It was found that the SPR devices operate in air with high coupling efficiency in excess of 40 dB with spectral sensitivities that outperform a typical long period grating, with one device yielding a wavelength spectral sensitivity of 12000 nm/RIU in the important aqueous index regime. The devices generate SPRs over a very large wavelength range, (visible to 2 mu m) by alternating the polarization state of the illuminating light.

Nano-scale morphological and electrical characterization of nc-SiOxNy thin layers for photovoltaic applications

Il presente lavoro di tesi propone uno studio approfondito di proprietà morfologiche e di trasporto di carica di film sottili di SiOxNy amorfi (a-SiOxNy) e nanocristallini (nc-SiOxNy), che trovano importanti applicazioni in celle fotovoltaiche ad eterogiunzione in silicio, ad alta efficienza. Lo studio è condotto mediante caratterizzazione elettrica e morfologica attraverso tecniche di microscopia a forza atomica (AFM). Sono stati studiati campioni di a-SiOxNy cresciuti con tecnica PECVD (Plasma Enhanced Chemical Vapor Deposition), in cui è stata variata unicamente la distanza tra gli elettrodi durante la deposizione. Sono stati inoltre studiati campioni di nc-SiOxNy, cresciuti con PECVD con una differente percentuale di N2O come gas precursore e un differente tempo di annealing. In entrambi i casi si tratta di un materiale innovativo, le cui proprietà fisiche di base, nonostante le numerose applicazioni, sono ancora poco studiate. L'analisi morfologica, condotta mediante AFM e successiva analisi statistica delle immagini, ha permesso di determinare alcune proprietà morfologiche dei campioni. L’analisi statistica delle immagini è stata validata, dimostrandosi stabile e consistente per lo studio di queste strutture. Lo studio delle proprietà di trasporto è stato condotto mediante acquisizione di mappe di corrente con tecnica conductive-AFM. In questo modo si è ottenuta una mappa di conducibilità locale nanometrica, che permette di comprendere come avviene il trasporto nel materiale. L'analisi di questo materiale mediante tecniche AFM ha permesso di evidenziare che l'annealing produce nei materiali nanocristallini sia un clustering della struttura, sia un significativo aumento della conducibilità locale del materiale. Inoltre la distanza tra gli elettrodi in fase di deposizione ha un leggero effetto sulle dimensioni dei grani. È da notare inoltre che su questi campioni si sono osservate variazioni locali della conducibilità alla nanoscala. L’analisi delle proprietà dei materiali alla nanoscala ha contribuito alla comprensione più approfondita della morfologia e dei meccanismi di trasporto elettronico.

An integrated nano-scale approach to profile miRNAs in limited clinical samples

Profiling miRNA expression in cells that directly contribute to human disease pathogenesis is likely to aid the discovery of novel drug targets and biomarkers. However, tissue heterogeneity and the limited amount of human diseased tissue available for research purposes present fundamental difficulties that often constrain the scope and potential of such studies. We established a flow cytometry-based method for isolating pure populations of pathogenic T cells from bronchial biopsy samples of asthma patients, and optimized a high-throughput nano-scale qRT-PCR method capable of accurately measuring 96 miRNAs in as little as 100 cells. Comparison of circulating and airway T cells from healthy and asthmatic subjects revealed asthma-associated and tissue-specific miRNA expression patterns. These results establish the feasibility and utility of investigating miRNA expression in small populations of cells involved in asthma pathogenesis, and set a precedent for application of our nano-scale approach in other human diseases. The microarray data from this study (Figure 7) has been submitted to the NCBI Gene Expression Omnibus (GEO; http://ncbi.nlm.nih.gov/geo) under accession no. GSE31030.

Generation and performance of localised surface plasmons utilising nano-scale structured multi-layered thin films deposited upon D-shaped optical fiber

A new generation of surface plasmonic optical fibre sensors is fabricated using multiple coatings deposited on a lapped section of a single mode fibre. Post-deposition UV laser irradiation using a phase mask produces a nano-scaled surface relief grating structure, resembling nano-wires. The overall length of the individual corrugations is approximately 14 μm with an average full width half maximum of 100 nm. Evidence is presented to show that these surface structures result from material compaction created by the silicon dioxide and germanium layers in the multi-layered coating and the surface topology is capable of supporting localised surface plasmons. The coating compaction induces a strain gradient into the D-shaped optical fibre that generates an asymmetric periodic refractive index profile which enhances the coupling of the light from the core of the fibre to plasmons on the surface of the coating. Experimental data are presented that show changes in spectral characteristics after UV processing and that the performance of the sensors increases from that of their pre-UV irradiation state. The enhanced performance is illustrated with regards to change in external refractive index and demonstrates high spectral sensitivities in gaseous and aqueous index regimes ranging up to 4000 nm/RIU for wavelength and 800 dB/RIU for intensity. The devices generate surface plasmons over a very large wavelength range, (visible to 2 μm) depending on the polarization state of the illuminating light. © 2013 SPIE.

Physical characteristics of localized surface plasmons resulting from nano-scale structured multi-layer thin films deposited on D-shaped optical fiber

Novel surface plasmonic optical fiber sensors have been fabricated using multiple coatings deposited on a lapped section of a single mode fiber. UV laser irradiation processing with a phase mask produces a nano-scaled surface relief grating structure resembling nano-wires. The resulting individual corrugations produced by material compaction are approximately 20 μm long with an average width at half maximum of 100 nm and generate localized surface plasmons. Experimental data are presented that show changes in the spectral characteristics after UV processing, coupled with an overall increase in the sensitivity of the devices to surrounding refractive index. Evidence is presented that there is an optimum UV dosage (48 joules) over which no significant additional optical change is observed. The devices are characterized with regards to change in refractive index, where significantly high spectral sensitivities in the aqueous index regime are found, ranging up to 4000 nm/RIU for wavelength and 800 dB/RIU for intensity. © 2013 Optical Society of America.

The influence of nano-scale second-phase particles on deformation of fine grained calcite mylonites

Grey and white carbonate mylonites were collected along thrust planes of the Helvetic Alps. They are characterised by very small grain sizes and non-random grain shape (SPO) and crystallographic preferred orientation (CPO). Presumably they deformed in the field of grain size sensitive flow by recrystallisation accommodated intracrystalline deformation in combination with granular flow. Both mylonites show a similar mean grain size, but in the grey mylonites the grain size range is larger, the grain shapes are more elongate and the dynamically recrystallised calcite grains are more often twinned. Grey mylonites have an oblique CPO, while the CPO in white mylonites is symmetric with respect to the shear plane. Combustion analysis and TEM investigations revealed that grey mylonites contain a higher amount of highly structured kerogens with particle sizes of a few tens of nanometers, which are finely dispersed at the grain boundaries. During deformation of the rock, nano-scale particles reduced the migration velocity of grain boundaries by Zener drag resulting in slower recrystallisation rates of the calcite aggregate. In the grey mylonites, more strain increments were accommodated by individual grains before they became refreshed by dynamic recrystallisation than in white mylonites, where grain boundary migration was less hindered and recrystallisation cycles were faster. Consequently, grey mylonites represent ‘deformation’ microfabrics while white mylonites are characterised by ‘recrystallisation’ microfabrics. Field geologists must utilise this different deformation behavior when applying the obliquity in CPO and SPO of the respective mylonites as reliable shear sense indicators.

Active site engineering for heterogeneous catalysis using emerging nano-structured materials

The growing concern about the depletion of oil has spurred worldwide interest in finding alternative feedstocks for important petrochemical commodities and fuels. On the one hand, the enormous re-serves found (208 trillion cubic feet proven1), environmental sustainability and lower overall costs point to natural gas as the primary source for energy and chemicals in the near future.2 Nowadays the transformation of methane into useful chemicals and liquid fuels is only feasible via synthesis gas, a mixture of molecular hydrogen and carbon monoxide, that is further transformed to methanol or to hydrocarbons under moderate reaction conditions (150-350 °C and 10-100 bar).3 For a major cost reduction and in order to valorize small natural gas sources, either more efficient "syngas to products" catalysts should be produced or the manner in which methane is initially activated should be changed, ideally by developing catalysts able to directly oxidize methane to interesting products such as methanol. On the other hand, from the point of view of CO2 emissions, the use of the re-maining fossil resources will further contribute to global warming. In this scenario, the development of efficient routes for the transformation of CO2 into useful chemicals and fuels would represent a considerable step forward towards sustainability. Indeed, the environmental and economic incen-tives to develop processes for the conversion of CO2 into fuels and chemicals are great. However, for such conversions to become economically feasible, considerable research is necessary. In this lecture we will summarize our recent efforts into the design of new catalytic systems, based on MOFs and COFs, to address these challenges. Examples include the development of new Fe based FTS catalysts, electrocatalysts for the selective conversion of CO2 into syngas, the development of efficient catalysts for the utilization of formic acid as hydrogen storage vector and the development of new enzyme inspired systems for the direct transformation of methane to methanol under mild reaction conditions. References (1) http://www.clearonmoney.com/dw/doku.php?id=public:natural_gas_reserves. (2) Derouane, E. G.; Parmon, V.; Lemos, F.; Ribeiro, F. R. Sustainable Strategies for the Up-grading of Natural Gas: Fundamentals, Challenges, and Opportunities; Springer, 2005. (3) Rofer-DePoorter, C. K. Chemical Reviews. ACS Publications 1981, pp 447–474.

Highly localized accelerating beams using nano-scale metallic gratings

Spatially accelerating beams are non-diffracting beams whose intensity is localized along curvilinear trajectories, also incomplete circular trajectories, before diffraction broadening governs their propagation. In this paper we report on numerical simulations showing the conversion of a high-numerical-aperture focused beam into a nonparaxial shape-preserving accelerating beam having a beam-width near the diffraction limit. Beam shaping is induced near the focal region by a diffractive optical element that consists of a non-planar subwavelength grating enabling a Bessel signature.

Production and characterization of novel thermoplastic (nano)composite materials for additive manufacturing applications

The increasing environmental global regulations have directed scientific research towards more sustainable materials, even in the field of composite materials for additive manufacturing. In this context, the presented research is devoted to the development of thermoplastic composites for FDM application with a low environmental impact, focusing on the possibility to use wastes from different industrial processes as filler for the production of composite filaments for FDM 3D printing. In particular carbon fibers recycled by pyro-gasification process of CFRP scraps were used as reinforcing agent for PLA, a biobased polymeric matrix. Since the high value of CFs, the ability to re-use recycled CFs, replacing virgin ones, seems to be a promising option in terms of sustainability and circular economy. Moreover, wastes from different agricultural industries, i.e. wheat and rice production processes, were valorised and used as biofillers for the production of PLA-biocomposites. The integration of these agricultural wastes into PLA bioplastic allowed to obtain biocomposites with improved eco-sustainability, biodegradability, lightweight, and lower cost. Finally, the study of novel composites for FDM was extended towards elastomeric nanocomposite materials, in particular TPU reinforced with graphene. The research procedure of all projects involves the optimization of production methods of composite filaments with a particular attention on the possible degradation of polymeric matrices. Then, main thermal properties of 3D printed object are evaluated by TGA, DSC characterization. Additionally, specific heat capacity (CP) and Coefficient of Linear Thermal Expansion (CLTE) measurements are useful to estimate the attitude of composites for the prevention of typical FDM issues, i.e. shrinkage and warping. Finally, the mechanical properties of 3D printed composites and their anisotropy are investigated by tensile test using distinct kinds of specimens with different printing angles with respect to the testing direction.

Non-linear modelling of microwave devices embedding nano-ferroelectric materials for real-time reconfigurable transmitarray

In this thesis work a nonlinear model for Interdigitated Capacitors (IDCs) based on ferroelectric materials, is proposed. Through the properties of materials such as Hafnium-Zirconium Oxide (HfZrO2), it is possible to realize tunable radiofrequency (RF) circuits. In particular, the model proposed in this thesis describes the use of an IDC, realized on a High-Resistivity silicon substrate, as a phase shifter for beam-steering applications. The model is obtained starting from already present experimental measurements, through which it is possible to identify a circuit model. The model is tested for both low power values and other power values using Harmonic Balance simulations, which show an excellent convergence of the model up to 40 dBm of input power. Furthermore, an array composed by two patches operating both at 2.55 GHz, which exploits the tunable properties of the HfZrO-based IDC is proposed. At 0dBm the model shows a 47° phase shift with polarization -1 V and 1 V which leads to a 11° steering of the main lobe of the array.

Monitorization of alveolar deposited surface area of nanoparticles and ultrafine particles in different environments

Nanotechnology is an important emerging industry with a projected annual market of around one trillion dollars by 2015. It involves the control of atoms and molecules to create new materials with a variety of useful functions. Although there are advantages on the utilization of these nano-scale materials, questions related with its impact over the environment and human health must be addressed too, so that potential risks can be limited at early stages of development. At this time, occupational health risks associated with manufacturing and use of nanoparticles are not yet clearly understood. However, workers may be exposed to nanoparticles through inhalation at levels that can greatly exceed ambient concentrations. Current workplace exposure limits are based on particle mass, but this criteria could not be adequate in this case as nanoparticles are characterized by very large surface area, which has been pointed out as the distinctive characteristic that could even turn out an inert substance into another substance exhibiting very different interactions with biological fluids and cells. Therefore, it seems that, when assessing human exposure based on the mass concentration of particles, which is widely adopted for particles over 1 μm, would not work in this particular case. In fact, nanoparticles have far more surface area for the equivalent mass of larger particles, which increases the chance they may react with body tissues. Thus, it has been claimed that surface area should be used for nanoparticle exposure and dosing. As a result, assessing exposure based on the measurement of particle surface area is of increasing interest. It is well known that lung deposition is the most efficient way for airborne particles to enter the body and cause adverse health effects. If nanoparticles can deposit in the lung and remain there, have an active surface chemistry and interact with the body, then, there is potential for exposure. It was showed that surface area plays an important role in the toxicity of nanoparticles and this is the metric that best correlates with particle-induced adverse health effects. The potential for adverse health effects seems to be directly proportional to particle surface area. The objective of the study is to identify and validate methods and tools for measuring nanoparticles during production, manipulation and use of nanomaterials.

Morphological modifications and surface amorphization in ZnO sonochemically treated nanoparticles

Application of nanoscale materials in photovoltaic and photocatalysis devices and photosensors are dramatically affected by surface morphology of nanoparticles, which plays a fundamental role in the understanding of the physical and chemical properties of nanoscale materials. Zinc oxide nanoparticles with an average size of 20 nm were obtained by the use of a sonochemical technique. X-ray diffraction (XRD) associated to Rietveld refinements and transmission electron microscopy (TEM) were used to study structural and morphological characteristics of the samples. An amorphous shell approximately 10 nm thick was observed in the ultrasonically treated sample, and a large reduction in particle size and changes in the lattice parameters were also observed. © 2012 Elsevier B.V. All rights reserved.

Síntese e imobilização de nanopartículas de ouro em fibras regeneradas via exaustão para potencial aplicação biomédica

The advancement of nanotechnology in the synthesis and characterisation of nanoparticles (NP's) has played an important role in the development of new technologies for various applications of nano-scale materials that have unique properties. The scientific development in the last decades in the field of nanotechnology has sought ceaselessly, the discovery of new materials for the most diverse applications, such as biomedical areas, chemical, optical, mechanical and textiles. The high bactericidal efficiency of metallic nanoparticles (Au and Ag), among other metals is well known, due to its ability to act in the DNA of fungi, viruses and bacteria, interrupting the process of cellular respiration, making them important means of study, in addition to its ability to protect UVA and UVB. The present work has as its main objective the implementation of an innovative method in the impregnation of nanoparticles of gold in textile substrate, functionalized with chitosan, by a dyeing process by exhaustion, with the control of temperature, time and velocity, thus obtaining microbial characteristics and UV protection. The exhausted substrates with colloidal solutions of NPAu's presented the colours, lilac and red (soybean knits) due to their surface plasmon peak around 520-540 nm. The NPAu's were synthesized chemically, using sodium citrate as a reducing agent and stabilizer. The material was previously cationised with chitosan, a natural polyelectrolyte, with the purpose of functionalising it to enhance the adsorption of colloid, at concentrations of 5, 7, 10 and 20 % of the bonding agent on the weight of the material (OWM). It was also observed, through an experimental design 23 , with 3 central points, which was the best process of exhaustion of the substrates, using the following factors: Time (min.), temperature (OC) and concentration of the colloid (%), having as a response to variable K/S (ABSORBÂNCIA/ Kubelka-Munk) of the fibres. Furthermore, it was evidenced as the best response, the following parameters: concentration 100%, temperature 70 ºC and time 30 minutes. The substrate with NPAu was characterised by XRD; thermal analysis using TGA; microstructural study using SEM/EDS and STEM, thus showing the NP on the surface of the substrate confirming the presence of the metal. The substrates showed higher washing fastness, antibacterial properties and UV radiation protection.

Multi-scale modeling of the mechanical behavior of polymer-based materials

Polymers have become the reference material for high reliability and performance applications. In this work, a multi-scale approach is proposed to investigate the mechanical properties of polymeric based material under strain. To achieve a better understanding of phenomena occurring at the smaller scales, a coupling of a Finite Element Method (FEM) and Molecular Dynamics (MD) modeling in an iterative procedure was employed, enabling the prediction of the macroscopic constitutive response. As the mechanical response can be related to the local microstructure, which in turn depends on the nano-scale structure, the previous described multi-scale method computes the stress-strain relationship at every analysis point of the macro-structure by detailed modeling of the underlying micro- and meso-scale deformation phenomena. The proposed multi-scale approach can enable prediction of properties at the macroscale while taking into consideration phenomena that occur at the mesoscale, thus offering an increased potential accuracy compared to traditional methods.

Predicting the mechanical behavior of amorphous polymeric materials under strain through multi-scale simulation

Polymeric materials have become the reference material for high reliability and performance applications. However, their performance in service conditions is difficult to predict, due in large part to their inherent complex morphology, which leads to non-linear and anisotropic behavior, highly dependent on the thermomechanical environment under which it is processed. In this work, a multiscale approach is proposed to investigate the mechanical properties of polymeric-based material under strain. To achieve a better understanding of phenomena occurring at the smaller scales, the coupling of a finite element method (FEM) and molecular dynamics (MD) modeling, in an iterative procedure, was employed, enabling the prediction of the macroscopic constitutive response. As the mechanical response can be related to the local microstructure, which in turn depends on the nano-scale structure, this multiscale approach computes the stress-strain relationship at every analysis point of the macro-structure by detailed modeling of the underlying micro- and meso-scale deformation phenomena. The proposed multiscale approach can enable prediction of properties at the macroscale while taking into consideration phenomena that occur at the mesoscale, thus offering an increased potential accuracy compared to traditional methods.