4 research outputs found
Novel gas sensors and electronic noses for optical, electrical and hybrid sensing: development, properties and applications
Smell is one of the most important senses of man. It is used in everyday life, influencing our behaviour. Evaluation of the quality of food and beverages or the production control in industries that require specialised personnel, are some examples of its use. The Electronic Nose mimics the human nose, through the transduction of a chemical interaction between a sensitive layer and the volatile compounds, generating a measurable signal. Conducting polymers, doped with dodecylbenzenesulfonic acid, employed in electrical gas sensors and in an electronic nose showed their applicability in monitoring the circadian emissions of fragrance by the plant Madagascar Jasmin and in the discrimination and classification of different samples of flaxseed, respectively.
An innovative approach in the development of sensitive thin films based on organized liquid crystal micelles in an ionic liquid, encapsulated in a biopolymer matrix and used as sensitive layers for gas sensors, is the focus of this thesis. Liquid crystal micelles acting as sensitive elements that change reversibly their orientation in the presence of volatile compounds showed, as a proof of concept, their potential use in the classification of volatile solvents. They were also successfully tested for monitoring the quality of Tilapia fish. The combination of this optical system with the electrical system gave the so called "hybrid sensor" with dual response. Thus, a single sensor was efficient in the quantification of ethanol in gasoline. Polarized light microscopy, SEM and AFM techniques were used to study the morphology of these layers and have revealed that the formation of the micelles is closely influenced by the solvent where the liquid crystal molecules are arranged. QCM studies were conducted in order to learn more about the interaction of these films with volatile compounds, and to check the influence of parameters such as the exposure time, solvent nature, film composition and drying time, on the film. These biopolymer films were also used as immobilisation matrix for cytochrome c, forming electrochemical sensors having an additional optical response
Novel gas sensors and electronic noses for optical, electrical and hybrid sensing: development, properties and applications
Smell is one of the most important senses of man. It is used in everyday life, influencing our behaviour. Evaluation of the quality of food and beverages or the production control in industries that require specialised personnel, are some examples of its use. The Electronic Nose mimics the human nose, through the transduction of a chemical interaction between a sensitive layer and the volatile compounds, generating a measurable signal. Conducting polymers, doped with dodecylbenzenesulfonic acid, employed in electrical gas sensors and in an electronic nose showed their applicability in monitoring the circadian emissions of fragrance by the plant Madagascar Jasmin and in the discrimination and classification of different samples of flaxseed, respectively.
An innovative approach in the development of sensitive thin films based on organized liquid crystal micelles in an ionic liquid, encapsulated in a biopolymer matrix and used as sensitive layers for gas sensors, is the focus of this thesis. Liquid crystal micelles acting as sensitive elements that change reversibly their orientation in the presence of volatile compounds showed, as a proof of concept, their potential use in the classification of volatile solvents. They were also successfully tested for monitoring the quality of Tilapia fish. The combination of this optical system with the electrical system gave the so called "hybrid sensor" with dual response. Thus, a single sensor was efficient in the quantification of ethanol in gasoline. Polarized light microscopy, SEM and AFM techniques were used to study the morphology of these layers and have revealed that the formation of the micelles is closely influenced by the solvent where the liquid crystal molecules are arranged. QCM studies were conducted in order to learn more about the interaction of these films with volatile compounds, and to check the influence of parameters such as the exposure time, solvent nature, film composition and drying time, on the film. These biopolymer films were also used as immobilisation matrix for cytochrome c, forming electrochemical sensors having an additional optical response
Novel Conducting and Biodegradable Copolymers with Noncytotoxic Properties toward Embryonic Stem Cells
Electroactive biomaterials
that are easily processed as scaffolds
with good biocompatibility for tissue regeneration are difficult to
design. Herein, the synthesis and characterization of a variety of
novel electroactive, biodegradable biomaterials based on poly(3,4-ethylenedioxythiphene)
copolymerized with poly(d,l lactic acid) (PEDOT-<i>co</i>-PDLLA) are presented. These copolymers were obtained
using (2,3-dihydrothieno[3,4-<i>b</i>][1,4]dioxin-2-yl)methanol
(EDOT-OH) as an initiator in a lactide ring-opening polymerization
reaction, resulting in EDOT–PDLLA macromonomer. Conducting
PEDOT-<i>co</i>-PDLLA copolymers (in three different proportions)
were achieved by chemical copolymerization with 3,4-ethylenedioxythiophene
(EDOT) monomers and persulfate oxidant. The PEDOT-<i>co</i>-PDLLA copolymers were structurally characterized by <sup>1</sup>H NMR and Fourier transform infrared spectroscopy. Cyclic voltammetry
confirmed the electroactive character of the materials, and conductivity
measurements were performed via electrochemical impedance spectroscopy.
In vitro biodegradability was evaluated using <i>proteinase K</i> over 35 days, showing 29–46% (w/w) biodegradation. Noncytotoxicity
was assessed by adhesion, migration, and proliferation assays using
embryonic stem cells (E14.tg2a); excellent neuronal differentiation
was observed. These novel electroactive and biodegradable PEDOT-<i>co</i>-PDLLA copolymers present surface chemistry and charge
density properties that make them potentially useful as scaffold materials
in different fields of applications, especially for neuronal tissue
engineering