Venerdì 3 Marzo 2023 alle ore 12 presso l’Aula Seminari, Piano I, Edificio U5 – via Roberto Cozzi 55
Relatore: Dott.ssa Sara Mattiello
Titolo: Conjugated materials from and into interface rich microheterogeneous environments
Abstract: Organic conjugated materials have been at the centre of intense investigation for decades. Their mechanical flexibility, lightness, tunability of (opto)electrochemical properties, and compatibility with solution processing make them advantageous for a variety of applications. On the downside, their hydrophobicity makes necessary the use of toxic organic solvents instead of the preferable aqueous media for their synthesis and processing. The fact that suitable surface-active molecules (surfactants) enables the preparation of stable colloids of lipophilic molecules in a water environment is a long-known cornerstone of formulation chemistry. In this seminar, I will show examples of both conjugated materials preparation (“from”) and use (“into”) in specifically engineered microheterogeneous aqueous environments. Firstly, I will demonstrate how the use of association colloids in water enables the synthesis of hydrophobic established derivatives with improved efficiency and sustainability. Then, I will show how such strategies allows the synthesis of materials that do not form at all in organic solvents.[1,2] Finally, I will discuss the use of aqueous formulations of hydrophobic conjugated molecules and polymers in anti-Stokes bio-imaging,[3] and in the manufacturing of organic thin film transistors (OTFTs) using waters as the only solvent for both synthesis and processing.[4]
[1] S. Mattiello et.al., Mater. Adv. 2, 7369 (2021)
[2] C.Ceriani et al., J. Organomet. Chem. 962, 122267 (2022)
[3] S. Mattiello et.al., Adv. Funct. Mater. 26, 8447–8454 (2016)
[4] C.Ceriani et al., Adv. Electr. Mater., accepted for publication (2023)
Relatore: Dott. Jacopo Pedrini
Titolo: Light-matter interaction for advanced photonic devices
Abstract: Group-IV semiconductors are at the center of research on optoelectronics, photonics and photovoltaics thanks to their CMOS compatibility that allows for the fabrication of devices through well-developed industrial processes. Considerable efforts are aimed at overcoming some of their limitations, such as the mediocre light emission efficiency, or the lattice mismatch that restricts heteroepitaxy. Self-assembled microcrystals grown on patterned Si seeds [1] have shown to possess exceptional optical properties [2], making them interesting for the development of optoelectronic devices such as low-intensity light detectors. However, their interaction with light has not been extensively studied until now. Recently, the combined analysis of optical techniques with finite elements simulations allowed us to gather a better understanding of the photonic properties of such microcrystal structures, which were shown to be flexible antireflective lattices ideal for high efficiency absorbers [3]. Moreover, they were shown to possess a full photonic bandgap that can be further exploited to reroute light emission, thereby increasing photoluminescence efficiency [4]. Finally, the manipulation of symmetry breaking in these periodic structures indicates that microcrystals form an intriguing platform also for future topological photonic circuits.
[1] C. V. Falub et al., Science 335, 1330 (2012))
[2] F. Pezzoli et al., Phys. Rev. Applied 1, 044005 (2014)
[3] J. Pedrini et al., Optics Express 28, 17, 24981 (2020)
[4] J. Pedrini et al., Phys. Rev. Applied 16, 064024 (2021)