1,721,036 research outputs found
Toward the Development of Combined Artificial Sensing Systems for Food Quality Evaluation: A Review on the Application of Data Fusion of Electronic Noses, Electronic Tongues and Electronic Eyes
Full text linkDevices known as electronic noses (ENs), electronic tongues (ETs), and electronic eyes (EEs) have been developed in recent years in the in situ study of real matrices with little or no manipulation of the sample at all. The final goal could be the evaluation of overall quality parameters such as sensory features, indicated by the “smell”, “taste”, and “color” of the sample under investigation or in the quantitative detection of analytes. The output of these sensing systems can be analyzed using multivariate data analysis strategies to relate specific patterns in the signals with the required information. In addition, using suitable data-fusion techniques, the combination of data collected from ETs, ENs, and EEs can provide more accurate information about the sample than any of the individual sensing devices. This review’s purpose is to collect recent advances in the development of combined ET, EN, and EE systems for assessing food quality, paying particular attention to the different data-fusion strategies applied
PEDOT modified microelectrodes. Preparation, characterisation and analytical performances
No full textPoly(3,4-ethylenedioxythiophene) (PEDOT) modified microelectrodes were prepared by electropolymerisation of therelevant monomer from CH3CN and H2O solutions. The electrochemical behaviour of the obtained coatings wasinvestigated by cyclic voltammetry in both organic and aqueous media. The anodic responses obtained for a typicalbenchmark analyte such as ascorbic acid have been chosen in order to test the different coatings; calibration curves havebeen built up in order to evaluate the repeatability of the response and reproducibility of the realised sensing system.Moreover, the ability of the modified microelectrodes to work in low conductivity media has been studied, and exploratorytests in dense food matrix have been performe
Recent advances in the direct electrochemical detection of drugs of abuse
No full textIn the last decade, the trafficking and use of illicit drugs showed a continuous incremental trend, remaining worldwide a challenging problem for the consequences on society, health, criminality and environment. The introduction on the market of new products and of illicit synthetic compounds represents a new challenging task for analytical chemistry, looking for rapid and accurate methods for the detection of illicit substances in seized street samples, biological fluids and wastewater. In this context, electrochemical sensors have shown promising results as an alternative to standard chromatographic and spectroscopic methods. This review aims at highlighting the most recent progresses in the use of electrochemistry for the detection of drugs of abuse, mainly including well consolidated substances like cannabinoids, cocaine, opioids, ecstasy and methamphetamine as well as new psychoactive molecules widely diffused at the present time. Different strategies have been described particularly consisting in the direct electrochemical oxidation of the target analyte. The implementation of tailored-made portable instruments with electrochemical detection methods constitutes an added value to improve the effectiveness of electrochemical sensors for the identification of psychoactive substances when performing large-scale sampling tests
Study of ultrathin Prussian Blue films using in situ electrochemical surface plasmon resonance
No full textCharacterisation of ultrathin Prussian Blue films has been performed using in situ electrochemical surface plasmon resonance technique. Prussian Blue films have been prepared by potentiostatic method on a gold-coated glass surface plasmon resonance sensor. The electrochemical reduction of Prussian Blue to Prussian White and oxidation to Berlin Green are accompanied by a change of the refractive index; the system shows repeating voltammetric responses over subsequent potential cycles. The surface plasmon resonance signal is capable of evidencing minute electrochemically induced changes in the inorganic film coating the electrode
Electrochemical, Spectroscopic and Microscopic Characterisation of Novel Poly(3,4-ethylenedioxythiophene)/Gold Nanoparticles Composite Materials.
No full textComposite materials consisting of poly(3,4-ethylenedioxithiophene) including Au nanoparticles encapsulatedby bulky anionic species have been electrogenerated and characterised through spectroscopic andmicroscopic techniques. The properties of electrodes modified by similar materials have been studiedwith respect to the oxidation of different benchmark electroactive species, such as negatively chargedascorbic and uric acids, and positively charged dopamine. The responses obtained evidence the dependenceof sensitivity and selectivity of the electrochemical responses on the presence and density of thenanoparticles and on the nature of the relevant encapsulating agent. In particular, the insertion of negativelycharged NPs activates a sort of electrostatic shield toward negatively charged molecules; however,also positively charged species result to be conditioned in accessing the redox active centres, locatedeither on the nanoparticle’s surface or on the conducting polymer’s molecules
Influence of the nature of the supporting electrolyte on the formation of poly[4,4'-bis(butylsulphanyl)-2,2'-bithiophene] films. A role for both counter-ion and co-ion in the polymer growth and p-doping processes
No full textElectrode deposits of a polythiophene with particularly interesting characteristics, i.e., poly[4,40-bis(butylsulphanyl)-2,20-bithiophene],have been generated in the presence of different supporting electrolytes. The formation of the coatings has been studied bycoupling conventional electrochemical techniques with quartz crystal microbalance measurements. The results of simultaneousvoltammetric or chronoamperometric and microgravimetric experiments allow us to show the influence exerted by the nature of thesupporting electrolyte on the polymerisation and concomitant charging–discharging processes of the conducting polymer
Sensori Amperometrici. Nuoivi materiali elettrodici
No full textThe article concerns the development of new materials for electrode systems. A complete characterisation of the materials and of the electrochemical systems is obtained by combiningthe results from different spectroscopic and electrochemical techniques. The resulting modified electrodes are tested as amperometric sensors. A particularly attractive applicationof these devices, even using (ultra)microelectrodes, is in the field of “blind analysis”, as elements of electronic tongues for the classification of real matrices
P- and n-doping of electrochemically formed poly(4,4 '-bisbutylsulfanyl-2,2 '-bithiophene). A novel material with reduced bandgap
No full textElectrodes covered by stable electron conducting polymer films which exhibit easy p- and relatively easy n-doping have been successfully prepared by electrochemical polymerisation of symmetrical 4,4'-bisbutylsulfanyl-2,2'-bithiophene. The whole of the cyclic voltammetric behaviour has been explained based on the concept of 'electrostatically stabilised polarons'
EQCM study of the p- and n-doping processes of a poly[4,4’-bis(alkylsulphanyl)-2,2’-bithiophene]
No full textElectrogenerated deposits of poly[4,40-bis(butylsulphanyl)-2,20-bithiophene] have been characterised in the presence of differentsupporting electrolytes, by coupling current (charge) to microgravimetric measurements from the electrochemical quartz crystal microbalance (EQCM). The simultaneous collection of voltammetric measurements and of data relative to mass changes shows the influence exerted by the nature of the supporting electrolyte on the charge-discharge steps of both p- and n-doping processes. Interestingly, the microgravimetric data collected corresponding to the pre-peaks of both doping processes suggest the occurrence of two opposite motions of ions (ingress into and exit out from the polymer) in the relevant potential region, giving a contribution to the study of the ‘residual charge’ phenomenon
Impedance Characteristics of Poly(4,4’- Bis(butylsulfanyl)-2,2’-bithiophene) Film Electrode as a Function of Different Oxidation Levels
No full textThe impedance characteristics of poly[4,4 ' -bis(butylsulfanyl)-2,2 ' -bithiophene] film electrode are studied at different p-doping levels. The impedance features can be coherently described modeling the polymer deposit by a 'generalized transmission line circuit', using different simplifications when dealing with different oxidation states. Through these simplifications, the parameters of the equivalent circuit can be calculated The deviation of the impedance plots of the oxidized state from the Warburg-impedance 45 degrees slope in the mid-frequency domain is attributed to a non-uniform ionic conductivity profile within the polymer film. The analysis of the plots suggests the high-frequency semicircle, detectable in the case of both the neutral and the p-doped polymer to be due to the ion transfer barrier at the polymer/solution interface
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