November 30th, 2021 Webinar Speakers

Our next webinar will take place via the internet on Tuesday November 30th at 11 AM EST/ 4 PM GMT. Sign up on our mailing list to receive the Zoom link!

We hope to see/hear from you all at one of our sessions or as one of the next speakers. If you are an early career scientist and would like to present your research, don't hesitate to submit an abstract today! For now, please learn more about our current speakers and their research below. We also thank the generous support from Cell Reports Physical Science, Merck, and the Royal Society of Chemistry.

Our featured speakers this week are Gerardo M. Ojeda-Carralero (graduate student, KU Leuven, Belgium and the University of Havana, Cuba), and Dr Lea Nienhaus (assistant professor, Florida State University, USA).


GERARDO M. OJEDA-CARRALERO (on Twitter @OjedaCarralero)

Biography: Gerardo M. Ojeda is a fourth-year PhD candidate in chemistry at KU Leuven, Belgium, under the advisory of Prof. Dr. Erik Van der Eycken and Prof. Dr. Daniel G. Rivera. He is developing methods for the covalent modification of peptides. His research experience includes isocyanide-based multicomponent reactions, transition metal catalysis, photoredox reactions and heterocyclic chemistry. He completed his BS at the in 2014 and his Master in organic chemistry in 2016, at the University of Havana. He is also coordinator of the Cuban chemistry olympiad.

Title of Talk: Using convertible isonitriles and metal catalysis for the modification of peptides and peptidomimetics

Abstract: The growing interest on peptide research have motivated the constant demand for new reliable methodologies for their covalent modification. Herein we discuss the use of convertible isonitriles as efficient tools to achieve ligation and macrocyclization of peptides via multicomponent reactions. Our protocol relies on the activation of the C-terminal carboxamide derived from the multicomponent step in the form of acyl indoles or pyrroles under acidic media. Further nucleophilic substitution allows the generation of (cyclic) N-substituted peptides and depsipeptides in good yields under mild conditions. We also describe a methodology for grafting peptides and peptidomimetic with isoquinolone and pyridine moieties using metal catalysis. Benzoylated peptides at the N-terminal position readily reacts with acetylenes in good to excellent yields in the presence of ruthenium(II). The metal promotes C(sp2)-H activation on the phenyl ring and the amide bond, which acts as directing group. The process is highly chemioselective and a great tolerance for the usual aminoacid protecting groups is observed. Similarly, a sequence based on the Ugi-azide reaction followed by a rhodium(III)-catalyzed intermolecular annulation allows to synthesize tetrazole-isoquinolones/pyridones hybrids. All procedures are simple, reproducible and do not require inert conditions.

DR LEA NIENHAUS (on Twitter @NienhausFSU)

Biography: Professor Nienhaus began her independent career at Florida State University in the Fall of 2018. She obtained her PhD from the University of Illinois at Urbana-Champaign working with Professor Gruebele on optical absorption detected by scanning tunneling microscopy with nanometer resolution. Following her PhD, she moved to MIT to work with Professor Bawendi on nanocrystal-sensitized solid-state photon upconversion. The Nienhaus Group has pioneered the application of bulk perovskite sensitizers in photon upconversion, and is currently working on unraveling the complex photophysical processes occurring in these devices. In addition, research emphasis in the Nienhaus Lab is placed on beating the diffraction limit by advancing optical scanning tunneling microscopy.

Title of Talk: Photon Transformers: Upconversion via Triplet-Triplet Annihilation

Abstract: Photon upconversion describes the process of shortening the wavelength of the light emitted upon irradiation, resulting in a gain in photon energy. To comply with energy conservation laws, this occurs by combining two or more low energy photons through triplet states. Since triplet states are ‘spin-forbidden’, so-called sensitizers are required to indirectly populate the triplet state. Triplet sensitizers span a broad range of material classes including from metal-organic complexes, nanomaterials and bulk perovskite films. Understanding the energy transfer mechanism is crucial for the advancement of optoelectronic devices based on this process. In particular, the role of trap states in the sensitizer is key to further increase the device efficiency.

The exact triplet sensitization mechanism varies depending on several factors including: (i) the absolute alignments of the sensitizer and acceptor energy levels. (ii) The exciton binding energy in the sensitizer, resulting in excited states in form of excitons or free carriers. (iii) Energetic polydispersity of a sample, which varies the energetic driving force for triplet transfer.

I present the current understanding of the triplet sensitization mechanism based on sensitizer materials with different dimensionalities ranging from 0D-3D and highlight the differences of each upconversion system. We obtain upconversion efficiencies exceeding 15% for quantum dot based green-to-blue upconversion, 5% for nanoplatelet-based green-to-blue upconversion and 4.3% for nanorod-sensitized red-to-blue upconversion.

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