539 research outputs found
Attualità e storia delle circostanze del reato. Un istituto al bivio tra legalità e discrezionalità
No full textM. PIFFERI, Accidentalia delicti e criteri di commisurazione della pena. Una lettura
storica delle circostanze alla ‘periferia’ del codice . . . 1; R. BARTOLI, Le circostanze ‘al bivio’ tra legalità e discrezionalità. . . . 19; L. GARLATI, Radici antiche per problemi attuali: le circostanze nella legislazione
asburgica . . . 51; F. COLAO, Il problema delle circostanze del reato. Dall’arbitrium al ‘potere
discrezionale del giudice’ nell’individualizzazione della pena. Un percorso
italiano tra Otto e Novecento . . 79; S. MARTÍN, Modelos de circunstancias del delito en la codificación penal española
(1822-1944) . . . 109; M. N. MILETTI, Elemosina giudiziaria o trionfo dell’ equità? Il ripristino delle
attenuanti generiche nella penalistica italiana del secondo dopoguerra. . . . 165; G. DE VERO, Le circostanze del reato tra determinazione legale e commisurazione giudiziale delle pene. . . . 213; A. MELCHIONDA, La disciplina italiana delle circostanze del reato, tra ambiguità storiche, disarmonie funzionali e prospettive di ricostruzione. . . 251; F. BASILE, L’enorme potere delle circostanze sul reato; l’enorme potere dei giudici sulle circostanze. . . 303
Electroanalysis with modified electrodes: from the use of simple nanomaterials to engineered nanohybrids
No full textIn recent years, electroanalysis has witnessed a great growth in the employment of nanomaterials and/or in the use of polymer films to develop smart “modified electrodes”, particularly suitable for trace analysis of contaminants of emerging concern [1-2]. High surface to volume ratio, analyte adsorptive preconcentration capability and appropriate nano-dimensions enormously increase the availability of interaction sites for the analyte, enhancing the sensitivity and lowering the detection limits. Moreover, the small dimensions may allow controlling the sensing process locally, in terms of change in the mass transport regime (e.g. from planar to convergent or to thin-layer), improving sensors performances. These effects are particularly maximized in the case of well-ordered structures. Furthermore, the use of appropriately tailored nanohybrids, characterized by synergistic functionalities based on the generation of heterojunctions has paved the way towards promising applications, obtaining “brave new materials”, with physico-chemical properties which are not only the sum of the precursors’ ones.
In this presentation, experimental results obtained by our group, working with different nanomaterials and nanohybrids for the modification of the electrodes for electroanalytical applications are presented and discussed:
- electrodes modified with appropriately functionalized Carbon NanoTubes (CNT) [3];
- electrodes modified with Sulphonated Poly (Aryl Ether Sulphones), a new class of polymers, ad hoc tailored for electroanalytical applications [4];
- electrodes modified with bimetallic Au/Pd and Au/Pt systems [5];
- photorenewable electrodes based on silver nanoparticles and titania [6];
- (photo)electrochemically active functional hybrids of multilayer CVD graphene decorated with colloidal TiO2 nanocrystals [7];
- (photo)electrochemically active functional hybrids of graphene decorated with colloidal gold nanoparticles.
References
[1] D.T. Pierce, J.X. Zhao, Trace Analysis with Nanomaterials. Wiley-VCH, 2010.
[2] “Electroanalysis at the Nanoscale”, Faraday Discuss., vol. 164, 2013.
[3] V. Pifferi, G. Cappelletti, C. Di Bari, D. Meroni, F. Spadavecchia, L. Falciola, “Multi-Walled Carbon Nanotubes (MWCNTs) modified electrodes: Effect of purification and functionalization on the electroanalytical performances”, Electrochimica Acta, vol. 146, pp. 403-410, 2014.
[4] L. Falciola, S. Checchia, V. Pifferi, H. Farina, M. A. Ortenzi, V. Sabatini, “Electrodes modified with sulphonated poly(aryl ether sulphone): effect of casting conditions on their enhanced electroanalytical performance”, Electrochimica Acta, vol. 194, pp. 405-412, 2016.
[5] V. Pifferi, C. E. Chan-Thaw, S. Campisi, A. Testolin, A. Villa, L. Falciola, L. Prati, “Au based catalysts: electrochemical characterization for structural insights”, Molecules, vol. 21(3), pp. 261, 2016.
[6] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, “Self-cleaning properties in engineered sensors for dopamine electroanalytical detection,“ Analyst, vol. 140, pp. 1486-1494, 2015.
[7] C. Ingrosso, G.V. Bianco, V. Pifferi, P. Guffanti et al., “Enhanced Photoactivity and Conductivity in Transparent TiO2 Nanocrystals/Graphene Hybrid Anode”, J. Mat. Chem. A, in press, 2017
Multiwalled carbon nanotubes decorated with gold or silver nanoparticles for trace electroanalysis
No full textAlbeit very challenging, in the last years trace analysis (Pierce and Zhao, 2010) (i.e. the analysis of analytes in concentration low enough to cause difficulty, generally under 1 ppm) has shown a tremendous growth, prompted by the urgent need of many International Organizations (US Environmental Protection Agency EPA, U.S. Food and Drug Administration FDA, European Food Safety Authority EFSA, World Health Organization WHO) looking for new analytical techniques for the detection of different molecules in different and increasingly more complex matrixes.
Trace analytes determination requires reliable and robust analytical methodologies characterized by high level of sensitivity, accuracy (in terms of precision and trueness), selectivity and specificity. In this context, electroanalytical techniques, particularly those based on pulsed voltammetry with modified electrodes, seem to be a promising independent alternative, combining the previously sought properties with other important characteristics: simplicity of use, low costs, portability, easy automation and possibility of on-line and on-site monitoring without tedious sample pre-treatments.
Among different possible modifying materials, nanosized and/or nanostructured materials are growing in importance and use, with the aim of increasing the affinity for the analyte and the sensitivity, lowering the limits of detection and minimizing or completely avoiding interferences, increasing the selectivity. In this field, unique peculiar properties dependent on metal nanoparticle size and shape are demonstrated by carbon nanomaterials coupled with metal nanoparticles (Rassaei et al., 2011 and Pifferi et al., 2013). For this reason, these materials are now extensively employed in electroanalysis for electrode modification.
In this framework, the electroanalytical application of modified electrodes based on carbon nanotubes decorated with gold or silver nanoparticles are here presented. The modified electrode were previously electrochemically characterized (by Cyclic Voltammetry and Electrochemical Impedance Spectroscopy). In particular, the synergic effect of both metal and carbon nanomaterials was investigated. Moreover, the use of PVA as protective polymer for metal NPs, has demonstrated its role in enhancing the electroanalytical performances due to the protection from oxidation, fouling products and interferences.
The optimized electrodes were finally tested for the determination of relevant or toxic analytical substances for environmental monitoring such as glycerol and chlorinated compounds, with interesting results (Pifferi et al., 2014).
Pierce D.T., Zhao J.X. (2010). “Trace Analysis with Nanomaterials” Wiley-VCH, Weinheim.
Pifferi V., Facchinetti G., Villa A., Prati L., Falciola L. (2014). Electrocatalytic activity of multiwalled carbon nanotubes decorated by silver nanoparticles for the detection of halothane. Catalysis Today, in press.
Pifferi V., Marona V., Longhi M., Falciola L. (2013). Characterization of polymer stabilized silver nanoparticles modified glassy carbon electrodes for electroanalytical applications. Electrochimica Acta, 109, 447-453.
Rassaei L., Marken F., Sillanpaa M., Amiri M., Cirtiu C.M., Sillanpaa M. (2011). Nanoparticles in electrochemical sensors for environmental monitoring. Trends in Analytical Chemistry, 30(11), 1704-1715
Permeation Mechanisms in the TMEM16B Calcium-Activated Chloride Channels.
No full textTMEM16A and TMEM16B encode for Ca2+-activated Cl- channels (CaCC) and are expressed in many cell types and play a relevant role in many physiological processes. Here, I performed a site-directed mutagenesis study to understand the molecular mechanisms of ion permeation of TMEM16B. I mutated two positive charged residues R573 and K540, respectively located at the entrance and inside the putative channel pore and I measured the properties of wild-type and mutant TMEM16B channels expressed in HEK-293 cells using whole-cell and excised inside-out patch clamp experiments. I found evidence that R573 and K540 control the ion permeability of TMEM16B depending both on which side of the membrane the ion substitution occurs and on the level of channel activation. Moreover, these residues contribute to control blockage or activation by permeant anions. Finally, R573 mutation abolishes the anomalous mole fraction effect observed in the presence of a permeable anion and it alters the apparent Ca2+-sensitivity of the channel. These findings indicate that residues facing the putative channel pore are responsible both for controlling the ion selectivity and the gating of the channel, providing an initial understanding of molecular mechanism of ion permeation in TMEM16B
Gold or silver-decorated multiwalled carbon nanotubes modified electrodes for trace electroanalysis
No full textTrace analysis [1] (i.e. the analysis of analytes in concentration low enough to cause difficulty, generally under 1 ppm) albeit very challenging, in the last years has shown a tremendous growth, prompted by the urgent need of many International Organizations (US Environmental Protection Agency EPA, U.S. Food and Drug Administration FDA, European Food Safety Authority EFSA, World Health Organization WHO) looking for new analytical techniques for the detection of different molecules in different and increasingly more complex matrixes.
The determination of trace analytes requires reliable and robust analytical methods characterized by high level of sensitivity, precision, accuracy, selectivity and specificity. Among different analytical techniques electroanalytical ones and particularly those based on pulsed voltammetry, seem to be a promising independent alternative in terms of very high precision, accuracy and sensitivity. Advantages in using these latter systems lie on simplicity of use, portability, easy automation and possibility of on-line and on-site monitoring without sample pre-treatments and low costs.
In this context, the use of nanosized and/or nanostructured materials for the modification of electrodes is growing in importance, with the aim of increasing the affinity for the analyte, increasing sensitivity, lowering the limits of detection and minimizing or completely avoiding interferences, i.e. increasing their selectivity. Carbon nanomaterials coupled with metal nanoparticles [2, 3] present unique peculiar properties, dependent on metal nanoparticle size and shape and therefore are extensively employed in electroanalysis as tunable materials.
In this communication, we will present the electrochemical characterization (by Cyclic Voltammetry and Electrochemical Impedance Spectroscopy) and the electroanalytical application of modified electrodes based on carbon nanotubes decorated with gold or silver nanoparticles. In particular, the synergic effect of both metal and carbon nanomaterials was investigated. Moreover, the use of PVA protective polymer for metal NPs allows better electroanalytical performances due to the protection from oxidation, fouling products and interferences. The optimized electrodes were then tested for the determination of relevant or toxic analytical substances for environmental monitoring such as glycerol and chlorinated compounds, with interesting results [4].
[1] D.T. Pierce, J.X. Zhao, Trace Analysis with Nanomaterials, Wiley-VCH, Weinheim (Germany), (2010).
[2] L. Rassaei, M. Amiri, C.M. Cirtiu, M. Sillanpaa, F. Marken, M. Sillanpaa, Trends in Analytical Chemistry 30(11) (2011) 1705-1715.
[3] V. Pifferi, V. Marona, M. Longhi, L. Falciola, Electrochimica Acta 109 (2013) 447-453.
[4] V. Pifferi, G. Facchinetti, A. Villa, L. Prati, L. Falciola, Catalysis Today, (2014), in press, doi:10.1016/j.cattod.2014.10.00
Photo-renewable engineered sensor based on silica, silver nanoparticles and titania
No full textElectrode surface passivation and fouling are important challenges in electroanalysis when using modified electrodes in complex matrices, especially in the biomedical and environmental fields [1-2].
In order to overcome such problems, the production of highly engineered ad hoc designed devices could provide really effective sensors [2]. In particular, a reliable and reusable sensor, that could be cleaned by a simple irradiation with UV or solar light, could be perfect for this purpose.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer is developed [3-4]. Such structure confers to the device multifunctional properties which can be conveniently used in the detection and quantification of some neurotransmitters: dopamine, norepinephrine and serotonin.
The sensor is thoroughly investigated by structural, morphological and electrochemical characterizations in order to understand the role of each component with the aim to improve the robustness and efficiency of the electroanalytical system. In particular, the size distribution of silver nanoparticles, the device architecture and surface homogeneity are inspected by electron microscopy. As confirmed by X-ray diffraction the overlayer is made of anatase (the active polymorph of titanium dioxide), capable of photodegrading model contaminants. Furthermore, electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that a highly ordered distribution of silver nanoparticles constitutes the active analytical core of the device, allowing easier electron transfer and better quantification of the analytes.
The system presents good sensing performances, reaching low detection limits even in the presence of typical interferents such as ascorbic and uric acids. Moreover, the titania photoactive top layer allows the complete recovery of the device performance in terms of sensitivity after a fast and simple UV-A cleaning step, affordable with different UV sources. In particular, three lamps (different in terms of power and wavelength) were tested, reaching the total removal of the contaminants in 10-15 minutes [5]. This “self-cleaning” property, combined with a remarkable resistance against aging and ease of use, allows to employ the sensor also for detection in real matrixes, such as liquor and serum.
ACKNOWLEDGEMENTS
The Authors would like to thank MIUR (Ministero dell’Istruzione, dell’Università e della Ricerca) for the fundings in the framework of the PRIN 2012 Project (20128ZZS2H)
REFERENCES
[1] C.M.A. Brett, Pure Appl. Chem. 73, 2001, pp 1969–1977.
[2] C.M. Welch, R.G. Compton, Anal. Bioanal. Chem. 384, 2006, pp 601–619.
[3] G. Maino, D. Meroni, V. Pifferi, L. Falciola, G. Soliveri, G. Cappelletti, S. Ardizzone, J. Nanoparticle Res. 15, 2013, pp 2087.
[4] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst 140, 2015, 1486-1494.
[5] V. Pifferi, G. Soliveri, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, L. Falciola, RSC Advances, 5, 2015, 71210-71214
Electrodes modified by sulphonated Poly (Aryl Ether Sulphone) (S-PES) for electroanalytical applications
No full textThe use of polymeric materials for electrodes modification, with the aim of increasing the affinity for the analyte, increasing sensitivity, lowering the limits of detection and minimizing or completely avoiding interferences is becoming an interesting challenge in recent electroanalytical methods. Although scarcely characterized or appropriately designed for the modification of electrodes, thanks to its large use in fuel cell devices, Nafion® is one of the most popular polymer also in electroanalytical applications [1].
Poly (Aryl Ether Sulphones), commonly called PES, are well-known engineered thermoplastic materials [2], with excellent properties thanks to their aromatic skeleton and charged groups, such as thermal and mechanical strength, resistance to oxidation and acid catalyzed hydrolysis. Moreover, they present high glass transition temperature, good solubility in polar aprotic and halogenated solvents, radiation stability, low flammability and toughness, together with low costs.
In this context, sulphonated Poly (Aryl Ether Sulphone) (S-PES) was studied as a new material for the production of modified electrodes in comparison with Nafion®.
The modified electrodes are fully characterized by cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS).
Different parameters have been studied: the quantity and the form (acidic, salt, linear, branched,...) of the polymer, different IECs, its method of drying, the casting solvent, its stability in air or solution.
In particular, as the Figure shows, 1 % linear PES in the acidic form, dried at 25 °C in a oven, after deposition from a N-Methylpyrrolidone solution, appears to present the best performances in terms of higher voltammetric peak currents, more stability and less resistive behaviour, superior to Nafion®, maintaining the partial electrochemical and chemical reversibility and the diffusive control.
[1] V. Pifferi, V. Marona, M. Longhi, L. Falciola, Electrochimica Acta, 109, (2013), 447-453. [2] R.T.S. Muthu Lakshmi, J. Meier-Haack, K. Schlenstedt, H. Komber, V. Choudhary and I.K. Varma, Reactive and Functional Polymers, 66 (6), (2006), 634–644
Self-cleaning features of an innovative engineered sensor based on silica, silver nanoparticles and titania
No full textPassivation of the electrode surface and fouling are important challenges in electroanalysis during the use of modified electrodes in complex matrices, especially in the biomedical and environmental fields [1-2].
In order to overcome such problems, the production of highly engineered ad hoc designed devices could access really effective sensors [2]. In particular, a performing, reliable and reusable sensor, that could be cleaned by a simple irradiation with UV or solar light, would be perfect for this purpose.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer was developed [3-4]. Such structure confers to the device multifunctional properties for a complex biomedical challenge: the detection and quantification of catecholamine neurotransmitters. The sensor was thoroughly investigated by structural, morphological and electrochemical characterizations in order to understand the role of each component with the aim to improve the robustness and efficiency of the electroanalytical system.
The overlayer was made of anatase (the active polymorph of titanium dioxide) as confirmed by X-ray diffraction and by measuring the photodegradation of model contaminants. The size distribution of silver nanoparticles, the device architecture and surface homogeneity were inspected by electron microscopy. Electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that a highly ordered distribution of silver nanoparticles constitutes the active core of the device, allowing easier electron transfer and better quantification of the analytes even in the presence of conventional interferents, e.g. ascorbic and uric acid. Titania photoactive top layer allowed total recovery of the device performance in terms of sensitivity after a fast and simple UV-A cleaning step, affordable with different UV sources. This self-cleaning property, combined with a remarkable resistance against aging and ease of use, allows to employ the sensor also in on-field and remote applications.
References
1. C.M.A. Brett, Pure Appl. Chem. 73, 2001, pp 1969–1977.
2. C.M. Welch, R.G. Compton, Anal. Bioanal. Chem. 384, 2006, pp 601–619.
3. G. Maino, D. Meroni, V. Pifferi, L. Falciola, G. Soliveri, G. Cappelletti, S. Ardizzone, J. Nanoparticle Res. 15, 2013, pp 2087.
4. G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst 140, 2015, 1486-1494
Innovative engineered sensors based on silica, silver nanoparticles and titania with self-cleaning features
No full textPassivation of the electrode surface and fouling are important challenges in electroanalysis during the use of modified electrodes in complex matrices, especially in the biomedical and environmental fields (Soliveri et al., 2015). The production of highly engineered devices, ad hoc designed for specific applications, could overcome such problems, accessing really effective sensors. A performing, reliable and reusable sensor, that could be cleaned by a simple irradiation with UV or solar light, would perfectly match this goal.
In this context, a three-layered transparent electrode, in which silver nanoparticles are embedded between a bottom silica and a top titania layer (Maino et al., 2013 and Welch and Compton, 2006), was developed. Such structure confers to the device multifunctional properties for a complex biomedical challenge: the detection and quantification of catecholamine neurotransmitters. The sensor was thoroughly investigated in order to understand the role of each component with the aim of making the device a robust and efficient electroanalytical system.
The overlayer was made of anatase (the active polymorph of titanium dioxide) as confirmed by X-ray diffraction and by measuring the photodegradation of model contaminants. The size distribution of silver nanoparticles, the device architecture and surface homogeneity were inspected by electron microscopy. Electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that a highly ordered distribution of silver nanoparticles constitutes the active core of the device, allowing easier electron transfer and better quantification of the analytes even in the presence of conventional interferents, e.g. ascorbic and uric acid. Titania photoactive top layer allowed total recovery of the device performance in terms of sensitivity after a fast and simple UV-A cleaning step, affordable with different UV sources. This self-cleaning property, combined with a remarkable resistance against aging and ease of use, allows to employ the sensor also in on-field and remote applications.
Maino G., Meroni D., Pifferi V., Falciola L., Soliveri G., Cappelletti G., Ardizzone S. (2013). Electrochemically assisted deposition of transparent, mechanically robust TiO2 films for advanced applications. J. Nanoparticle Res., 15, 2087.
Soliveri G., Pifferi V., Panzarasa G., Ardizzone S., Cappelletti G., Meroni D., Sparnacci K., Falciola L. (2015). Self-cleaning properties in engineered sensors fordopamine electroanalytical detection. Analyst, 140, 1486-1494.
Welch C. M., Compton R. G. (2006). The use of nanoparticles in electroanalysis: a review. Anal. Bioanal. Chem., 384, 601–619
Sulphonated Poly (Aryl Ether Sulphone) as electrode modifier in electroanalytical applications
No full textA general problem encountered during the use of solid electrodes is the lowering of the electroanalytical response, caused by partial blocking of the surface by adsorbable reaction products. The use of polymeric materials to modify and protect the electrodes can minimize such alteration, allowing the detection of different species also in complex matrixes. Among different polymers, Nafion® is one of the most used [1-3], although scarcely studied and not appropriately designed for electrode modification.
Sulphonated Poly (Aryl Ether Sulphones), commonly called S-PES, are engineered thermoplastic materials [4] that, due to their aromatic skeleton and charged sulphonic groups, present interesting properties: thermal and mechanical strength, resistance to oxidation and acid catalyzed hydrolysis, high glass transition temperature, good solubility in polar aprotic and halogenated solvents, radiation stability, low flammability and toughness, together with low costs.
In this work, sulphonated Poly (Aryl Ether Sulphones) (S-PES), prepared by copolymerization with sulphonated monomers, have been studied as new materials for the production of modified electrodes for electroanalytical applications. A comparison with the use of Nafion® has been also made.
After a complete characterization by Cyclic Voltammetry and Electrochemical Impedance Spectroscopy (EIS), the electroanalytical performances of the modified electrodes (sensitivity, LOD, LOQ, stability in air and solvent, ...) have been evaluated in function of different morphological and preparative parameters: the quantity and the form of the polymer (acidic, salt, with different macromolecular architecture, ...), different IECs, the method of drying, the casting solvent.
The results demonstrate that 1 % linear PES in the acidic form, dried at 25 °C in a oven, after deposition from a N-Methylpyrrolidone solution presents the best performances in terms of higher voltammetric peak currents, more stability and less resistive behaviour, superior to Nafion®, maintaining the partial electrochemical and chemical reversibility and the diffusive control.
[1] V. Pifferi, V. Marona, M. Longhi, L. Falciola, Electrochimica Acta, 109, (2013), 447-453.
[2] L.M. Moretto, F. Montagner, R. Ganzerla, P. Ugo, Anal Bioanal Chem, 405, (2013), 3603-3610.
[3] C.M.A. Brett, V.A. Alves, D.A. Fungaro, Electroanalysis, 13(3), (2001), 212-218.
[4] R.T.S. Muthu Lakshmi, J. Meier-Haack, K. Schlenstedt, H. Komber, V. Choudhary and I.K. Varma, Reactive and Functional Polymers, 66 (6), (2006), 634–644
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