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8. Nitrogen-Doped Carbon Quantum Dots for Biosensing Applications: The Effect of the Thermal Treatments on Electrochemical and Optical Properties

Author

Ghezzi, F, Donnini, R, Sansonetti, A, Giovanella, U, La Ferla, B, Vercelli, B, Ghezzi, Francesco, Donnini, Riccardo, Sansonetti, Antonio, Giovanella, Umberto, La Ferla, Barbara, Vercelli, Barbara, Ghezzi, F, Donnini, R, Sansonetti, A, Giovanella, U, La Ferla, B, Vercelli, B, Ghezzi, Francesco, Donnini, Riccardo, Sansonetti, Antonio, Giovanella, Umberto, La Ferla, Barbara, and Vercelli, Barbara

Abstract

The knowledge of the ways in which post-synthesis treatments may influence the properties of carbon quantum dots (CDs) is of paramount importance for their employment in biosensors. It enables the definition of the mechanism of sensing, which is essential for the application of the suited design strategy of the device. In the present work, we studied the ways in which post-synthesis thermal treatments influence the optical and electrochemical properties of Nitrogen-doped CDs (N-CDs). Blue-emitting, N-CDs for application in biosensors were synthesized through the hydrothermal route, starting from citric acid and urea as bio-synthesizable and low-cost precursors. The CDs samples were thermally post-treated and then characterized through a combination of spectroscopic, structural, and electrochemical techniques. We observed that the post-synthesis thermal treatments show an oxidative effect on CDs graphitic N-atoms. They cause their partially oxidation with the formation of mixed valence state systems, [CDs]0+, which could be further oxidized into the graphitic N-oxide forms. We also observed that thermal treatments cause the decomposition of the CDs external ammonium ions into ammonia and protons, which protonate their pyridinic N-atoms. Photoluminescence (PL) emission is quenched.

Published
2023

14. Proposal of a Testing Procedure to Qualify Iter Window Assemblies Exposed to High Microwave Stray Radiation

Author

Gelfusa, Michela, primary, Donnini, Riccardo, additional, Vila, Rafael, additional, Simonetto, Alessandro, additional, Bruschi, Alessandro, additional, Cucè, Daniela, additional, Lazzari, Anna, additional, Maquet, Philippe, additional, Mirizzi, Francesco, additional, Murari, Andrea, additional, Nobili, Matteo, additional, Peluso, Emmanuele, additional, Romanelli, Francesco, additional, Sirinelli, Antoine, additional, and Sozzi, Carlo, additional

Published
2022
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15. Nitrogen-Doped Carbon Quantum Dots for Biosensing Applications: The Effect of the Thermal Treatments on Electrochemical and Optical Properties.

Author

Ghezzi, Francesco, Donnini, Riccardo, Sansonetti, Antonio, Giovanella, Umberto, La Ferla, Barbara, and Vercelli, Barbara

Subjects
*QUANTUM dots, *OPTICAL properties, *DOPING agents (Chemistry), *AMMONIUM ions, *TREATMENT effectiveness, *CITRIC acid, *PHOTOTHERMAL effect
Abstract

The knowledge of the ways in which post-synthesis treatments may influence the properties of carbon quantum dots (CDs) is of paramount importance for their employment in biosensors. It enables the definition of the mechanism of sensing, which is essential for the application of the suited design strategy of the device. In the present work, we studied the ways in which post-synthesis thermal treatments influence the optical and electrochemical properties of Nitrogen-doped CDs (N-CDs). Blue-emitting, N-CDs for application in biosensors were synthesized through the hydrothermal route, starting from citric acid and urea as bio-synthesizable and low-cost precursors. The CDs samples were thermally post-treated and then characterized through a combination of spectroscopic, structural, and electrochemical techniques. We observed that the post-synthesis thermal treatments show an oxidative effect on CDs graphitic N-atoms. They cause their partially oxidation with the formation of mixed valence state systems, [CDs]0+, which could be further oxidized into the graphitic N-oxide forms. We also observed that thermal treatments cause the decomposition of the CDs external ammonium ions into ammonia and protons, which protonate their pyridinic N-atoms. Photoluminescence (PL) emission is quenched. [ABSTRACT FROM AUTHOR]

Published
2023
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16. Nitrogen-doped Carbon Quantum Dots Obtained Hydrothermally from Citric Acid and Urea: the Role of the Specific Nitrogen Centers in their Electrochemical and Optical Responses

Author

Vercelli, B, Donnini, R, Ghezzi, F, Sansonetti, A, Giovanella, U, La Ferla, B, Vercelli, Barbara, Donnini, Riccardo, Ghezzi, Francesco, Sansonetti, Antonio, Giovanella, Umberto, La Ferla, Barbara, Vercelli, B, Donnini, R, Ghezzi, F, Sansonetti, A, Giovanella, U, La Ferla, B, Vercelli, Barbara, Donnini, Riccardo, Ghezzi, Francesco, Sansonetti, Antonio, Giovanella, Umberto, and La Ferla, Barbara

Abstract

The knowledge of how the different types of nitrogen centers affect the electrochemical and optical properties of Nitrogen-doped carbon quantum dots (N-CDs) is of paramount importance in the design and synthesis of these nanostructures. In fact, from the knowledge of the redox centers of N-CDs it is possible tune their energetic levels in order to realize the suitable matches for the design of opto-electronic, photovoltaic or catalytic devices. Herein we present a study of the electrochemical and the optical responses of N-CDs, obtained by hydrothermal method from citric acid and urea. The main issue is to investigate the role played by the specific nitrogen centers in their redox processes. From the voltammetric responses we showed that the observed oxidation processes of N-CDs involve their graphitic and pyrrolic N-atoms, respectively, while the reduction process regards their protonated pyridinic N-atoms. Then, from spectro-electrochemical determinations, we explained that the oxidation of the graphitic N-atoms is a two electron process that gives an N-oxide form through the reaction with a molecule of water and the loss of two protons. Finally we discussed the observed pH-dependence of both the optical and the electrochemical responses of our N-CDs to explain the role played by their pyridinic N-atoms.

Published
2021

17. Effects of a nitrogen seeded plasma on nanostructured tungsten films having fusion-relevant features

Author

Uccello, Andrea, primary, Ghezzi, Francesco, additional, Laguardia, Laura, additional, Caniello, Roberto, additional, Dellasega, David, additional, dell’Era, Fabio, additional, Della Torre, Davide, additional, Donnini, Riccardo, additional, Granucci, Gustavo, additional, Mesto, Ernesto, additional, Minelli, Daniele, additional, Passoni, Matteo, additional, Pedroni, Matteo, additional, Pezzoli, Andrea, additional, and Ricci, Daria, additional

Published
2020
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19. The role of particle ripening on the creep acceleration of Nimonic 263 superalloy

Author

Angella Giuliano, Donnini Riccardo, Ripamonti Dario, and Maldini Maurizio

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

Physically based constitutive equations need to incorporate the most relevant microstructural features of materials to adequately describe their mechanical behaviour. To accurately model the creep behaviour of precipitation hardened alloys, the value and the evolution of strengthening particle size are important parameters to be taken into account. In the present work, creep tests have been run on virgin and overaged (up to 3500 h at 800 ∘C) Nimonic 263, a polycrystalline nickel base superalloy used for combustion chambers of gas turbines. The experimental results suggest that the reinforcing particle evolution is not the main reason for the creep acceleration that seems to be better described by a strain correlated damage, such as the accumulation of mobile dislocations or the grain boundary cavitation. The coarsened microstructure, obtained by overageing the alloy at high temperature before creep testing, mainly influences the initial stage of the creep, resulting in a higher minimum creep rate and a corresponding reduction of the creep resistance.

Published
2014
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30. Micro-chemical characterization of fibermatrix interface in TI6ALAV-SICF composite [Caratterizzazione microchimica dell interfaccia fibra-matrice nel composito TI6AL4V-SICf]

Author

Donnini, Riccardo, Kaciulis, S., Mezzi, Alessio, Montanari, Roberto, Tata, Maria Elisa, and Testani, Claudio

Subjects
Composite meterials, genetic structures, Heat treatments, Materials characterization, Electron microscopy, Titanium and alloys, Settore ING-IND/21 - Metallurgia
Abstract

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Published
2007

43. Comparison between Roll Diffusion Bonding and Hot Isostatic Pressing Production Processes of Ti6Al4V-SiCf Metal Matrix Composites

Author

Testani, Claudio, Ferraro, F., Deodati, Paolo, Donnini, Riccardo, Montanari, Roberto, Kaciulis, Saulius, and Mezzi, Alessio

Abstract

Titanium-metal-matrix composites (Ti-MMC) are materials with very large specific resistance and potential operative temperature up to 800° C. At present these composites are produced by Hot Isostatic Pressing (HIP), a reliable but expensive manufacturing method. To cut production costs, Centro Sviluppo Materiali SpA (CSM) has developed and patented an experimental plant for co-rolling at high temperature sheets of titanium alloy and silicon carbide monofilaments fabrics. The experimental Roll Diffusion Bonding (RDB) pilot plant permits a reduction of process costs of about 40% with respect to the HIP process. This work reports the results of microstructural and mechanical examinations carried out on composites realized by RDB and HIP. The comparison shows that the fibre-matrix interface is stable in both the composites while the mechanical properties of RDB composite are better due to its smaller grain size and high dislocation density.

Published
2011
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44. Micro-Chemistry and Mechanical Behaviour of Ti6Al4V-SiCf Composite Produced by HIP for Aeronautical Applications

Author

Deodati, Paolo, Donnini, Riccardo, Kaciulis, Saulius, Kazemian-Abyaneh, Majid, Mezzi, Alessio, Montanari, Roberto, Testani, Claudio, and Ucciardello, Nadia

Abstract

The paper reports the results of an extensive characterization of the Ti6Al4V-SiCf composite produced by hot isostatic pressing (HIP) to assess its capability to withstand the in-service conditions of turbine blades operating at middle temperatures in aeronautical engines. The microstructure of composite, in as-fabricated condition and after long-term heat treatments (up to 1,000 hours) in the temperature range 673-873 K, has been investigated by means of different techniques. Particular attention was paid to the micro-chemical evolution of fibre-matrix interface which is scarcely affected also by the most severe heat treatments examined here. This leads to stable mechanical properties as evidenced by hardness, tensile and FIMEC instrumented indentation tests. Therefore, the composite can operate at the maximum temperature (873 K) foreseen for its aeronautical applications without remarkable modifications of its microstructure and degradation of mechanical properties. The mechanical characterization has been completed by internal friction and dynamic modulus measurements carried out both at constant and increasing temperature, from 80 to 1173 K.

Published
2011
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45. Anelastic Phenomena at the Fibre-Matrix Interface of the Ti6Al4V-SiCf Composite

Author

Deodati, Paolo, Donnini, Riccardo, Kaciulis, Saulius, Mezzi, Alessio, Montanari, Roberto, Testani, Claudio, and Ucciardello, Nadia

Abstract

The composite, consisting of Ti6Al4V matrix reinforced by unidirectional SiC fibres (SCS-6), has been investigated by mechanical spectroscopy at temperatures up to 1,173 K. For comparison, the same experiments have been performed on the corresponding monolithic alloy. The internal friction (IF) spectrum of the composite exhibits a new relaxation peak superimposed to an exponentially increasing background. This peak, which is not present in the monolithic alloy, has an activation energy H = 186 kJ mol-1 and a relaxation time 0 = 2.3 x 10-15 s. The phenomenon has been attributed to a reorientation of interstitial-substitutional pairs in the  phase of Ti6Al4V matrix around the fibres. This explanation is supported by the results of micro-chemical characterization carried out by X-ray photoelectron spectroscopy (XPS) combined with Ar ion sputtering.

Published
2010
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46. Microstructural Characterization of Ti6Al4V-SiCf Composite Produced by New Roll-Bonding Process

Author

Deodati, Paolo, Donnini, Riccardo, Kaciulis, Saulius, Mezzi, Alessio, Montanari, Roberto, Testani, Claudio, and Ucciardello, Nadia

Abstract

Roll Diffusion Bonding (RDB) is a new process, developed at C.S.M., for producing Ti composites reinforced by long fibres. The prototypal “diffusion bonding” plant permits to co-roll at high temperature in superplastic rolling field (under temperature and strain rate control) foils of titanium alloy and fabrics made of SiC monofilaments. This study evidenced that the Ti6Al4V-SiCf composite produced by roll-bonding exhibits superior mechanical properties with respect the same material prepared by Hot Isostatic Pressing (HIP) owing to the smaller grain size and the higher dislocation density.

Published
2010
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47. The Role of Microstructure on the Tensile Plastic Behaviour of Ductile Iron GJS 400 Produced through Different Cooling Rates—Part II: Tensile Modelling.

Author

Angella, Giuliano, Donnini, Riccardo, Ripamonti, Dario, Górny, Marcin, and Zanardi, Franco

Subjects
NODULAR iron, DUAL-phase steel, PEARLITIC steel, MICROSTRUCTURE, GRAPHITE, GRAIN size, TENSILE tests
Abstract

Tensile testing on ductile iron GJS 400 with different microstructures produced through four different cooling rates was performed in order to investigate the relevance of the microstructure's parameters on its plastic behaviour. Tensile flow curve modelling was carried out with the Follansbee and Estrin-Kocks-Mecking approach that allowed for an explicit correlation between plastic behaviour and some microstructure parameters. In the model, the ferritic grain size and volume fraction of pearlite and ferrite gathered in the first part of this investigation were used as inputs, while other parameters, like nodule count and interlamellar spacing in pearlite, were neglected. The model matched very well with the experimental flow curves at high strains, while some mismatch was found only at small strains, which was ascribed to the decohesion between the graphite nodules and the ferritic matrix that occurred just after yielding. It can be concluded that the plastic behaviour of GJS 400 depends mainly on the ferritic grain size and pearlitic volume fraction, and other microstructure parameters can be neglected, primarily because of their high nodularity and few defects. [ABSTRACT FROM AUTHOR]

Published
2019
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