619 research outputs found
Silica shelling of Quantum Dots and gold film development
No full textColloidal Quantum Dots (QDs) are an established class of optoelectronic materials thanks to their tunable and highly efficient emission. The encapsulation of QDs in silica shells is a well-known procedure to protect them from the external environment and obtain dispersibility in polar solvents. Here, we have coated different types of QDs (CdSe@CdS [1] and InP@ZnS [2]) with silica shells of controlled thickness. The silica shells were obtained exploiting the Reverse Microemulsion reaction combined with an experimental design approach [3,4]. In addition to this, we deposited a uniform gold film over the silica shell. The combination of the QDs emission with the gold plasmon resonance enables an improvement in the optical properties, as already demonstrated [5]. As a first step to achieve this goal, the functionalization of the silica shell for further gold seeds attachment is required. With such aim, we employed (3-Aminopropyl)trimethoxysilane (APTMS), with an amino group binding to the gold seed, helping in the development of the film. Instead, the silicon of the APTMS binds strongly to the silica surface through a covalent bond. Thanks to the 1H and two-dimensional NOESY (Nuclear Overhauser Effect Spectroscopy) NMR analyses, we assessed the bonding of the APTMS to the silica surface and determined the best ratio of injected molecules to the surface area of the nanoparticle to obtain complete coverage. Then, we attached gold seeds to the silica surface, and we merged them by adding gold precursor through a slow injection, employing a syringe pump. In this way, we avoided self-nucleation of gold nanoparticles in the chemical environment, achieving uniform gold coverage. As a further development, by exploiting the variable thickness of the silica shell, the gold film could also be employed to build an optical microcavity around the QD (increasing the QD-gold film distance through a thicker silica shell). In general, silica shells around QDs can be used as a template to colloidally grow more sophisticated optical structures able to impart additional effects to tune the emitter properties.
Bibliography
(1) Carbone, L.; Nobile, C.; De Giorgi, M.; Sala, F. D.; Morello, G.; Pompa, P.; Hytch, M.; Snoeck, E.; Fiore, A.; Franchini, I. R.; Nadasan, M.; Silvestre, A. F.; Chiodo, L.; Kudera, S.; Cingolani, R.; Krahne, R.; Manna, L. Nano Lett. 2007, 7 (10), 2942–2950.
(2) Tessier, M. D.; Dupont, D.; De Nolf, K.; De Roo, J.; Hens, Z. Chem. Mater. 2015, 27 (13), 4893–4898.
(3) Fiorito, S.; Silvestri, M.; Cirignano, M.; Marini, A.; Di Stasio, F. ACS Appl. Nano Mater. 2024, 7 (4), 3724–3733
(4) Leardi, R. Analytica Chimica Acta 2009, 652 (1), 161–172.
(5) Ji, B.; Giovanelli, E.; Habert, B.; Spinicelli, P.; Nasilowski, M.; Xu, X.; Lequeux, N.; Hugonin, J.-P.; Marquier, F.; Greffet, J.-J.; Dubertret, B. Nature Nanotech 2015, 10 (2), 170–175
Matrimonio. Art. 29 - Rapporti personali fra coniugi. (Legge 31 maggio 1995, n. 218 - Riforma del sistema italiano di diritto internazionale privato)
No full textMatrimonio. Art. 30 - Rapporti patrimoniali fra coniugi, (Legge 31 maggio 1995, n. 218 - Riforma del sistema italiano di diritto internazionale privato)
No full textII edizion
Matrimonio. Art. 30 - Rapporti patrimoniali fra coniugi, (Legge 31 maggio 1995, n. 218 - Riforma del sistema italiano di diritto internazionale privato)
No full text
Matrimonio. Art. 29 - Rapporti personali fra coniugi. (Legge 31 maggio 1995, n. 218 - Riforma del sistema italiano di diritto internazionale privato)
No full textEncapsulation of Quantum Dots in Tunable-Diameter Silica Shells Functionalized with a Gold Coating
No full textColloidal Quantum Dots (QDs) are an established class of optoelectronic materials thanks to their tunable and highly efficient emission. The encapsulation of QDs in silica shells is a well-known procedure to protect them from the external environment and obtain dispersibility in polar solvents. We have coated different types of QDs (CdSe@CdS [1] and InP@ZnS [2]) with silica shells of different thickness and develop a gold film over them.
First, silica shells were synthesized using reverse microemulsion reaction in combination with an experimental design approach [3,4]. By varying the number of reverse microemulsion reactions performed, shells with diameters ranging from 40 nm to 70 nm were obtained. To further increase the nanoparticle size (80 – 110 nm), a Stöber reaction was employed [5]. In this case, to prevent self-nucleation of empty silica particles, the silica precursor (tetraethyl orthosilicate) was slowly injected using a syringe pump. Finally, we deposited a uniform gold film over the 50 nm diameter silica shells to combine the QDs emission with the gold plasmon resonance, thus imparting a variety of effects on the optical properties of the QDs, as already demonstrated [6]. To grow an Au film, preliminary steps are required as functionalization of silica with aminosilane and subsequent addition of gold seeds. We employed (3-Aminopropyl)trimethoxysilane (APTMS), which has an amino group that can coordinate the gold while the silicon binds strongly to the silica surface through a covalent bond. Thanks to the 1H and two-dimensional NOESY (Nuclear Overhauser Effect Spectroscopy) NMR analyses, we assessed the bonding of the APTMS to the silica surface and determined the best ratio of injected molecules to the surface area of the nanoparticle to obtain complete coverage. Then, we attached gold seeds to the silica surface, and we merged them by adding gold precursor through a slow injection, employing a syringe pump. Through this approach, we avoided self-nucleation of gold nanoparticles, achieving uniform gold coverage. Given the tunable thickness of the SiO2 shell, one can imagine employing the gold film to build an optical microcavity around the QD. In general, silica shells around QDs can be used as a template to build more sophisticated optical structures and consequently to impart additional optical features to the emitter.
Bibliography
(1) Carbone, L.; Nobile, C.; De Giorgi, M.; Sala, F. D.; Morello, G.; Pompa, P.; Hytch, M.; Snoeck, E.; Fiore, A.; Franchini, I. R.; Nadasan, M.; Silvestre, A. F.; Chiodo, L.; Kudera, S.; Cingolani, R.; Krahne, R.; Manna, Nano Lett. 2007, 7 (10), 2942–2950.
(2) Tessier, M. D.; Dupont, D.; De Nolf, K.; De Roo, J.; Hens, Z. Chem. Mater. 2015, 27 (13), 4893–4898.
(3) Fiorito, S.; Silvestri, M.; Cirignano, M.; Marini, A.; Di Stasio, F. ACS Appl. Nano Mater. 2024, 7 (4), 3724–3733.
(4) Leardi, R. Anal Chim Acta 2009, 652 (1–2), 161–172.
(5) Stöber, W.; Fink, A.; Bohn, E. J. Colloid Interface Sci. 1968, 26 (1), 62–69.
(6) Ji, B.; Giovanelli, E.; Habert, B.; Spinicelli, P.; Nasilowski, M.; Xu, X.; Lequeux, N.; Hugonin, J.-P.; Marquier, F.; Greffet, J.-J.; Dubertret, B. Nature Nanotech 2015, 10 (2), 170–175
La Convenzione europea di Lussemburgo del 20.5.1980 sul riconoscimento e l’esecuzione delle decisioni in materia di affidamento dei minori e di ristabilimento dell’affidamento (artt. 1-5, 12, 7-10, 11, 13-15)
No full textIl punto di vista delle insegnanti. Report sull'analisi della realizzazione del progetto “Coding e robotica”
No full textQuando si parla di coding e robotica educativa, argomenti da alcuni anni di estrema attualità nel campo dell’educazione, è impossibile prescindere da due aspetti tra loro complementari: la tecnologia, che comprende le competenze algoritmiche, di programmazione nonché la scelta ponderata degli strumenti; e l’inserimento di tali attività nel curricolo e in contesti interdisciplinari per integrare la complessità dei saperi con metodologie proprie della didattica laboratoriale. Il volume descrive l’impianto di ricerca, la cornice metodologica e le considerazioni tecniche del progetto PON “Coding e Robotica” sviluppato dagli autori e sperimentato nella scuola dell’infanzia e del primo ciclo nell’anno scolastico 2019-20. L’analisi delle esperienze dei docenti coinvolti non presenta solo i risultati del progetto, ma fornisce agli insegnanti interessati anche delle linee guida per inserire il coding e la robotica educativa nel loro lavoro in class
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