Photostable fluorescent molecules on layered hexagonal boron nitride: Ideal single-photon sources at room temperature

Peri-Alkylated Terrylenes and Ternaphthalenes Building-Blocks Towards Multi-Edge Nanographenes

Since its first synthesis by Clar in 1948, terrylene - a fully connected ternaphthalene oligomer via naphthalene's peri-positions - has gained special focus within the rylene family, drawing interest for its unique chemical, structural, optoelectronic and single photon emission properties. In this study, we introduce a novel synthetic pathway that enhances the solubility of terrylene derivatives through complete peri-alkylation, while also facilitating extensions at the bay-positions. This approach not only broadens the scope of terrylene's chemical versatility but also opens new avenues for developing solution processable novel multi-edge nanographenes and tailoring electronic energy levels through topological edge structures. Our findings include a comprehensive structural and spectroscopic characterization along with transient absorption spectroscopy and photophysics of both the synthesized peri-alkylated terrylene and its phenylene-fused derivative.

Sharp zero-phonon lines of single organic molecules on a hexagonal boron-nitride surface

Single fluorescent molecules embedded in the bulk of host crystals have proven to be sensitive probes of the dynamics in their nano environment, thanks to their narrow (about 30-50 MHz or 0.1-0.2 μeV) optical linewidth of the 0-0 zero-phonon line (0-0 ZPL) at cryogenic temperatures. However, the optical linewidths of the 0-0 ZPL have been found to increase dramatically as the single molecules are located closer to a surface or interface, while no 0-0 ZPL has been detected for single molecules on any surface. Here we study single terrylene molecules adsorbed on the surface of hexagonal boron-nitride (hBN) substrates. Our low-temperature results show that it is possible to observe the 0-0 ZPL of fluorescent molecules on a surface. We compare our results for molecules deposited on the surfaces of annealed and non-annealed hBN flakes and we see a marked improvement in the spectral stability of the emitters after annealing.

Progress and perspectives in single-molecule optical spectroscopy

We review some of the progress of single-molecule optical experiments in the past 20 years and propose some perspectives for the coming years. We particularly focus on methodological advances in fluorescence, super-resolution, photothermal contrast, and interferometric scattering and briefly discuss a few of the applications. These advances have enabled the exploration of new emitters and quantum optics; the chemistry and biology of complex heterogeneous systems, nanoparticles, and plasmonics; and the detection and study of non-fluorescing and non-absorbing nano-objects. We conclude by proposing some ideas for future experiments. The field will move toward more and better signals of a broader variety of objects and toward a sharper view of the surprising complexity of the nanoscale world of single (bio-)molecules, nanoparticles, and their nano-environments.