An electronic nose based on coated piezoelectric quartz crystals to certify ewes' cheese and to discriminate between cheese varieties

An electronic nose based on coated piezoelectric quartz crystals was used to distinguish cheese made from ewes' milk, and to distinguish cheese varieties. Two sensors coated with Nafion and Carbowax could certify half the ewes' cheese samples, exclude 32 cheeses made from cow's milk and to classify half of the ewes' cheese samples as possibly authentic. Two other sensors, coated with polyvinylpyrrolidone and triethanolamine clearly distinguished between Flamengo, Brie, Gruyère and Mozzarella cheeses. Brie cheeses were further separated according to their origin, and Mozzarella grated cheese also appeared clearly separated from non-grated Mozzarella.publishe

Design and characterization of molecular fluorescent architectures for potential applications as sensors and logic switches

The increasing complexity of information technology and the therewith connected demands for miniaturization have alimented the need for alternative small-scale approaches to computing and data processing. Molecules can be one solution for this problem. However, they must be taught to integrate the functions of computing such as logic gates and circuits. Molecular switches can be converted from one state to another by a wide range of external stimuli, such as chemical species, light, temperature etc. This switching action can be translated into binary codes and in some cases (as shown in this thesis) also into multivalued coding. Beside their potential for computing, applications in object coding, intelligent materials, pro¬drug activation, and diagnostics/actuation are widely pursued with molecular switches nowadays. The global objective of this research is to develop new molecular systems, based on molecular logics. Particular attention is given here to aminonaphthalimides and arylisoquinoline dyes with boronic ester groups. The aminonaphthalimide fluorophore, integrated in a receptorrfluorophore-receptor2 architecture, is able to switch its fluorescence upon application of acid input in an off-on-off manner. Thereby the characteristics of a T-latch function are mimicked with a molecular system. Furthermore, a new class of arylisoquinoline fluorophores with boronic ester groups was extensively investigated. The intemal-charge-transfer (ICT) fluorescence emission of these dyes can be fine-tuned in an ample spectral window. These fluorophores can be switched by protonation of the isoquinoline moiety or the formation of fluoroboronate complexes with the boronic acid ester. Borylated arylisoquinoline dyes with pH-dependent fluorescence are also discussed. These dyes feature aromatic amino substitution with appended lateral aliphatic amino groups and the isoquinoline proton receptor. The photophysical properties of the ICT dyes were studied and the fluorescence modulation upon multiple and orthogonal protonation with acid led to the interpretation of multi-level switching including off-on-off, ternary, and quaternary responses.La creciente complejidad de las tecnologías de información y las demandas relacionadas con las mismas con respecto a la miniaturización han aumentado la necesidad de enfoques a pequeña escala alternativos para la computación y el procesamiento de datos. Las moléculas pueden ser una solución para este problema. Sin embargo, deben ser “enseñados” a integrar las fiinciones de computación, tales como puertas lógicas y circuitos lógicos. El estado de los interruptores moleculares se puede modificar, intercambiar de ON a OFF, por medio de una amplia gama de estímulos externos, tales como especies químicas, la luz, la temperatura, etc. Esta acción de conmutación se puede traducir en códigos binarios y en algunos casos (como se muestra en esta tesis), también en codificación de varios valores. Junto a su potencial para aplicaciones de computación en la codificación de objetos, en la actualidad, también se consiguen con éxito otros sistemas por medio de interruptores moleculares, como son materiales inteligentes, activación pro-fármacos y diagnóstico/actuación. El objetivo general de esta investigación es desarrollar nuevos sistemas moleculares, basados en la lógica molecular. Se presta especial atención a los derivados de aminonaftalimida con diferentes receptores amino y colorantes arilisoquinolina borilados con grupos éster borónico. El fluoróforo aminonaftalimida, integrado en una arquitectura receptorrfluoróforo-receptor2, es capaz de cambiar su fluorescencia, tras la aplicación de un ácido, de una manera off-on-off. De este modo se llegan a imitar las características de una función T-latch con un sistema molecular. Además, se investigó extensamente una nueva clase de fluoróforos arilisoquinolina con grupos éster borónico. La transferencia interna de carga (TIC) de emisión de fluorescencia de los colorantes puede ser ajustada en una amplia ventana espectral. Estos fluoróforos se pueden conmutar por protonación de la fracción de isoquinolina o por la formación de complejos fluoroboronados con el éster de ácido borónico utilizando iones fluoruro. También se discute sobre colorantes arilisoquinolina borilados con fluorescencia dependiente del pH. Estos colorantes cuentan con una sustitución amino aromático con grupos amino alifáticos laterales adjuntos y el receptor isoquinolina de protones. Se estudiaron las propiedades fotofísicas de la TIC y, la modulación de la fluorescencia tras la protonación múltiple y ortogonal con ácido, dio lugar a unos cambios en las señales que permitieron la interpretación de múltiples niveles incluyendo off-on-off, y respuestas ternarias y cuaternarias. También se discuten colorantes arilisoquinolina borilados con fluorescencia dependiente del pH. Estos colorantes cuentan con una sustitución amino aromático con grupos amino alifáticos laterales adjuntos y el receptor isoquinolina de protones. Las propiedades fotofísicas de la transferencia interna de carga se estudiaron y la modulación de la fluorescencia tras la  protonación múltiple y ortogonal con ácido llevó a una interpretación de conmutación de múltiples niveles incluyendo off- on-off, y respuestas ternarias y cuaternarias

Análise de circuitos osciladores com sensores SAW para a utilização em narizes eletrônicos

This dissertation consists in analyzing different oscillator circuit topologies designed to work with SAW (surface acoustic wave) sensors, in order to be applied in electronic noses, for chemical sensing of volatile substances. Research has been done about some of the most common types of electronic nose sensors found on the market, where the pros and cons are revealed, as well as the wide range of applicability of this type of device. Radiofrequency concepts were discussed, which are important for elaboration and construction of oscillator circuits. Results of simulations and experimental tests of the three oscillator configurations studied (common base Colpitts, series resonant Colpitts and with an RFIC amplifier) are found. As a result, it was concluded that, in general, the common base Colpitts oscillator circuit presented the best performances, with peak-to-peak 800mV amplitude voltage, 10,58mA current consumption (5V DC input), the fastest stabilization time – with 8µs – and output signal with the least harmonic interference.Essa dissertação consiste em analisar diferentes topologias de circuitos osciladores projetados para trabalhar com sensores SAW (sensores de ondas acústicas de superfície), no intuito de serem aplicados em narizes eletrônicos, para o sensoriamento químico de substâncias voláteis. Foi feita uma pesquisa sobre alguns dos tipos de sensores para narizes eletrônicos mais comuns encontrados no mercado, onde são revelados os prós e os contras, assim como a ampla gama de aplicabilidade desse tipo de dispositivo. Foram abordados conceitos de radiofrequência, que são importantes para a elaboração e construção de circuitos osciladores. São encontrados os resultados das simulações e testes experimentais das três configurações de osciladores estudadas (Colpitts de base comum, Colpitts ressonante série e com um amplificador RFIC). Com isto, concluiu-se que, de maneira geral, o circuito oscilador Colpitts de base comum apresentou as melhores performances, com tensão de amplitude em 800mV pico a pico, consumo de corrente em 10,58mA (5V DC de entrada), o mais rápido tempo de estabilização – com 8µs – e o sinal de saída com a menor interferência de harmônicos

Polymer sorbent materials for the extraction of organic compounds

This thesis describes how modifying PDMS can influence the polymer’s sorbent properties towards organic compounds in aqueous matrices. Where each new sorbent’s extraction performance was measured through TD-GC-MS and characterized through various analytical techniques. Chapter 1: Gives a brief introduction to the analytical techniques used within the thesis whilst outlining the current state-of-the-art PDMS modification techniques reported in recent literature. Chapter 2: Provides the detailed design of experiment and the corresponding materials used for each results chapter. Chapter 3: This chapter shows the results and discussions section for the encapsulation of amines with PDMS. In which each PDMS-based material demonstrated variable sorptive extraction properties towards organic compounds in aqueous solutions compared to PDMS. However, each material presented thermal instability and extraction performance dropped over time. Chapter 4: Highlights how bonding amines to PDMS improved the thermal stability of the sorbent material. However, the TD-GC-MS results showed little variance in extraction performance compared to that of the currently used PDMS, unlike that of the encapsulated method. Chapter 5: This section looked at how a novel preparation technique aimed to incorporate established commercially available sorbents within the PDMS. These bi-phasic sorbents were tested for organic compound extraction via TD-GC-MS. The results showed that the PDMS-Tenax GR outperformed all other sorbents for most of the tested organic compounds. Whilst demonstrating both chemical and thermal robustness. The main issue around this section was how to scale-up the material preparation step. Chapter 6: This chapter provides an overview of the results obtained during the thesis while highlighting the areas of improvement. Future works state the direction this research should move based on the result obtained