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38 results on '"Chasse, Thomas"'

1. Impact of the Ligand Shell on Structural Changes and Decomposition of All-Inorganic Mixed-Halide Perovskite (CsPbX3) Nanocrystals under X-Ray Illumination

Author

Wahl, Jan, Haizmann, Philipp, Kirsch, Christopher, Frecot, Rene, Mukharamova, Nastasia, Assalauova, Dameli, Kim, Young Yong, Zaluzhnyy, Ivan, Chassé, Thomas, Vartanyants, Ivan A., Peisert, Heiko, and Scheele, Marcus

Subjects
Condensed Matter - Materials Science
Abstract

We show that the decomposition of caesium lead halide perovskite nanocrystals under continuous X-ray illumination depends on the surface ligand. For oleic acid/oleylamine, we observe a fast decay accompanied by the formation of elemental lead and halogen. Upon surface functionalization with a metal porphyrin derivate, the decay is markedly slower and involves the disproportionation of lead to Pb0 and Pb3+. In both cases, the decomposition is preceded by a contraction of the atomic lattice, which appears to initiate the decay. We find that the metal porphyrin derivative induces a strong surface dipole on the nanocrystals, which we hold responsible for the altered and slower decomposition pathway. These results are important for application of lead halide perovskite nanocrystals in X-ray scintillators., Comment: 31 pages, 14 Figures

Published
2021

2. Overcoming the challenges in controlled thermal deposition of organic diradicals

Author

Junghoefer, Tobias, Gallagher, Nolan M., Kolanji, Kubandiran, Giangrisostomi, Erika, Ovsyannikov, Ruslan, Chassé, Thomas, Baumgarten, Martin, Rajca, Andrzej, Calzolari, Arrigo, and Casu, Maria Benedetta

Subjects
Condensed Matter - Materials Science, Condensed Matter - Soft Condensed Matter
Abstract

We have demonstrated that it is possible to evaporate diradicals in a controlled environment obtaining thin films in which the diradical character is preserved. However, evaporation represents a challenge. The presence of two radical sites makes the molecules more reactive, even in case of very stable single radicals. We have explored the parameters that play a role in this phenomenon. Bulk formation thermodynamics and delocalisation of the unpaired electrons play the major role. The higher the formation energies of the crystal, the more difficult is the evaporation of intact radicals. The larger the delocalization, the more stable is the film exposed to air. The evaporation of different radicals, also with a larger number of radical sites can be successfully addressed considering our findings.

Published
2020

3. Stability of radical-functionalized gold surfaces by self-assembly and on-surface chemistry

Author

Junghoefer, Tobias, Nowik-Boltyk, Ewa Malgorzata, de Sousa, J. Alejandro, Giangrisostomi, Erika, Ovsyannikov, Ruslan, Chassé, Thomas, Veciana, Jaume, Mas-Torrent, Marta, Rovira, Concepció, Crivillers, Núria, and Casu, Maria Benedetta

Subjects
Condensed Matter - Materials Science
Abstract

We have investigated the radical functionalization of gold surfaces with a derivative of the perchlorotriphenylmethyl (PTM) radical, using two methods: by chemisorption from the radical solution and by on surface chemical derivatization from a precursor. We have investigated the obtained self-assembled monolayers by photon-energy dependent X-ray photoelectron spectroscopy. Our results show that the molecules were successfully anchored on the surfaces. The monolayers are characterized by air and beam stability unprecedented for films of organic radicals. Over very long beam exposure we observed a dynamic nature of the radical-Au complex. The results clearly indicate that (mono)layers of PTM; radical derivatives have the necessary stability to stand device applications.

Published
2020

10. Fingerprint of fractional charge transfer at metal/organic interface

Author

Savu, Sabine-A., Biddau, Giulio, Pardini, Lorenzo, Bula, Rafael, Bettinger, Holger F., Draxl, Claudia, Chassé, Thomas, and Casu, M. Benedetta

Subjects
Condensed Matter - Materials Science, Condensed Matter - Soft Condensed Matter
Abstract

Although physisorption is a widely occurring mechanism of bonding at the organic/metal interface, contradictory interpretations of this phenomenon are often reported. Photoemission and X-ray absorption spectroscopy investigations of nanorods of a substituted pentacene, 2,3,9,10-tetrafluoropentacene, deposited on gold single crystals reveal to be fundamental to identify the bonding mechanisms. We find fingerprints of a fractional charge transfer from the clean metal substrate to the physisorbed molecules. This phenomenon is unambiguously recognizable by a non-rigid shift of the core-level main lines while the occupied states at the interface stay mostly unperturbed, and the unoccupied states experience pronounced changes. The experimental results are corroborated by first-principles calculations.

Published
2015

31. Stability of radical-functionalized gold surfaces by self-assembly and on-surface chemistry

Author

Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, Consejo Superior de Investigaciones Científicas (España), Helmholtz-Zentrum Berlin for Materials and Energy, German Research Foundation, Junghoefer, Tobias, Nowik-Boltyk, Ewa Malgorzata, Sousa, J. Alejandro de, Giangrisostomi, Erika, Ovsyannikov, Ruslan, Chasse, Thomas, Veciana, Jaume, Mas Torrent, Marta, Rovira, Concepció, Crivillers, Núria, Casu, Maria Benedetta, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, Consejo Superior de Investigaciones Científicas (España), Helmholtz-Zentrum Berlin for Materials and Energy, German Research Foundation, Junghoefer, Tobias, Nowik-Boltyk, Ewa Malgorzata, Sousa, J. Alejandro de, Giangrisostomi, Erika, Ovsyannikov, Ruslan, Chasse, Thomas, Veciana, Jaume, Mas Torrent, Marta, Rovira, Concepció, Crivillers, Núria, and Casu, Maria Benedetta

Abstract

We have investigated the radical functionalization of gold surfaces with a derivative of the perchlorotriphenylmethyl (PTM) radical using two methods: by chemisorption from the radical solution and by on-surface chemical derivation from a precursor. We have investigated the obtained self-assembled monolayers by photon-energy dependent X-ray photoelectron spectroscopy. Our results show that the molecules were successfully anchored on the surfaces. We have used a robust method that can be applied to a variety of materials to assess the stability of the functionalized interface. The monolayers are characterized by air and X-ray beam stability unprecedented for films of organic radicals. Over very long X-ray beam exposure we observed a dynamic nature of the radical–Au complex. The results clearly indicate that (mono)layers of PTM radical derivatives have the necessary stability to withstand device applications.

Published
2020

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