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Hung TC, Godinez-Loyola Y, Steinbrecher M, Kiraly B, Khajetoorians AA, Doltsinis NL, Strassert CA, Wegner D. Activating the Fluorescence of a Ni(II) Complex by Energy Transfer. J Am Chem Soc 2024; 146:8858-8864. [PMID: 38513215 PMCID: PMC10996004 DOI: 10.1021/jacs.3c07716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 03/07/2024] [Accepted: 03/07/2024] [Indexed: 03/23/2024]
Abstract
Luminescence of open-shell 3d metal complexes is often quenched due to ultrafast intersystem crossing (ISC) and cooling into a dark metal-centered excited state. We demonstrate successful activation of fluorescence from individual nickel phthalocyanine (NiPc) molecules in the junction of a scanning tunneling microscope (STM) by resonant energy transfer from other metal phthalocyanines at low temperature. By combining STM, scanning tunneling spectroscopy, STM-induced luminescence, and photoluminescence experiments as well as time-dependent density functional theory, we provide evidence that there is an activation barrier for the ISC, which, in most experimental conditions, is overcome. We show that this is also the case in an electroluminescent tunnel junction where individual NiPc molecules adsorbed on an ultrathin NaCl decoupling film on a Ag(111) substrate are probed. However, when an MPc (M = Zn, Pd, Pt) molecule is placed close to NiPc by means of STM atomic manipulation, resonant energy transfer can excite NiPc without overcoming the ISC activation barrier, leading to Q-band fluorescence. This work demonstrates that the thermally activated population of dark metal-centered states can be avoided by a designed local environment at low temperatures paired with directed molecular excitation into vibrationally cold electronic states. Thus, we can envisage the use of luminophores based on more abundant transition metal complexes that do not rely on Pt or Ir by restricting vibration-induced ISC.
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Affiliation(s)
- Tzu-Chao Hung
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
- Institute
for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Yokari Godinez-Loyola
- Institut
für Anorganische und Analytische Chemie, University of Münster, 48149 Münster, Germany
- Center
for Nanotechnology (CeNTech), University
of Münster, 48149 Münster, Germany
| | - Manuel Steinbrecher
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
| | - Brian Kiraly
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
| | | | - Nikos L. Doltsinis
- Institut
für Festkörpertheorie and Center for Multiscale Theory
and Computation, University of Münster, 48149 Münster, Germany
| | - Cristian A. Strassert
- Institut
für Anorganische und Analytische Chemie, University of Münster, 48149 Münster, Germany
- Center
for Nanotechnology (CeNTech), University
of Münster, 48149 Münster, Germany
- Cells in
Motion Interfaculty Centre (CiMIC) and Center for Soft Nanoscience
(SoN), University of Münster, 48149 Münster, Germany
| | - Daniel Wegner
- Institute
for Molecules and Materials, Radboud University, 6500 GL Nijmegen, The Netherlands
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Adhikari S, Smit R, Orrit M. Future Paths in Cryogenic Single-Molecule Fluorescence Spectroscopy. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2024; 128:3-18. [PMID: 38229590 PMCID: PMC10788914 DOI: 10.1021/acs.jpcc.3c06564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/23/2023] [Accepted: 11/28/2023] [Indexed: 01/18/2024]
Abstract
In the last three decades, cryogenic single-molecule fluorescence spectroscopy has provided average-free understanding of the photophysics and of fundamental interactions at molecular scales. Furthermore, they propose original pathways and applications in the treatment and storage of quantum information. The ultranarrow lifetime-limited zero-phonon line acts as an excellent sensor to local perturbations caused either by intrinsic dynamical degrees of freedom, or by external perturbations, such as those caused by electric fields, elastic and acoustic deformations, or light-induced dynamics. Single aromatic hydrocarbon molecules, being sensitive to nanoscale probing at nanometer scales, are potential miniaturized platforms for integrated quantum photonics. In this Perspective, we look back at some of the past advances in cryogenic optical microscopy and propose some perspectives for future development.
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Affiliation(s)
| | - Robert Smit
- Huygens−Kamerlingh
Onnes Laboratory, Leiden University, 2300 RA Leiden, The Netherlands
| | - Michel Orrit
- Huygens−Kamerlingh
Onnes Laboratory, Leiden University, 2300 RA Leiden, The Netherlands
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Kaiser K, Lieske LA, Repp J, Gross L. Charge-state lifetimes of single molecules on few monolayers of NaCl. Nat Commun 2023; 14:4988. [PMID: 37591847 PMCID: PMC10435478 DOI: 10.1038/s41467-023-40692-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 08/02/2023] [Indexed: 08/19/2023] Open
Abstract
In molecular tunnel junctions, where the molecule is decoupled from the electrodes by few-monolayers-thin insulating layers, resonant charge transport takes place by sequential charge transfer to and from the molecule which implies transient charging of the molecule. The corresponding charge state transitions, which involve tunneling through the insulating decoupling layers, are crucial for understanding electrically driven processes such as electroluminescence or photocurrent generation in such a geometry. Here, we use scanning tunneling microscopy to investigate the decharging of single ZnPc and H2Pc molecules through NaCl films of 3 to 5 monolayers thickness on Cu(111) and Au(111). To this end, we approach the tip to the molecule at resonant tunnel conditions up to a regime where charge transport is limited by tunneling through the NaCl film. The resulting saturation of the tunnel current is a direct measure of the lifetimes of the anionic and cationic states, i.e., the molecule's charge-state lifetime, and thus provides a means to study charge dynamics and, thereby, exciton dynamics. Comparison of anion and cation lifetimes on different substrates reveals the critical role of the level alignment with the insulator's conduction and valence band, and the metal-insulator interface state.
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Affiliation(s)
- Katharina Kaiser
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803, Rüschlikon, Switzerland.
- Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000, Strasbourg, France.
| | | | - Jascha Repp
- Department of Physics, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Leo Gross
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803, Rüschlikon, Switzerland.
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Nian LL, Wang T, Lü JT. Plasmon Squeezing in Single-Molecule Junctions. NANO LETTERS 2022; 22:9418-9423. [PMID: 36449564 DOI: 10.1021/acs.nanolett.2c03371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Scanning tunneling microscope (STM)-induced luminescence provides an ideal platform for electrical generation and the atomic-scale manipulation of nonclassical states of light. However, despite its extreme importance in quantum technologies, squeezed light emission with reduced quantum fluctuations has hitherto not been demonstrated in such a platform. Here, we theoretically predict that the emitted light from the plasmon mode can be squeezed in an STM single molecular junction subject to an external laser drive. Going beyond the traditional paradigm that generates squeezing with the quadratic interaction of photons, our prediction explores the molecular coherence involved in an anharmonic energy spectrum of a coupled plasmon-molecule-exciton system. Furthermore, we show that, by selectively exciting the energy ladder, the squeezed plasmon can show either sub- or super-Poissonian statistical properties. We also demonstrate that, following the same principle, the molecular excitonic mode can be squeezed simultaneously.
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Affiliation(s)
- Lei-Lei Nian
- School of Physics and Astronomy, Yunnan University, 650091Kunming, People's Republic of China
| | - Tao Wang
- School of Physics, Institute for Quantum Science and Engineering, and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074Wuhan, People's Republic of China
| | - Jing-Tao Lü
- School of Physics, Institute for Quantum Science and Engineering, and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074Wuhan, People's Republic of China
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Single-Molecule Chemical Reactions Unveiled in Molecular Junctions. Processes (Basel) 2022. [DOI: 10.3390/pr10122574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022] Open
Abstract
Understanding chemical processes at the single-molecule scale represents the ultimate limit of analytical chemistry. Single-molecule detection techniques allow one to reveal the detailed dynamics and kinetics of a chemical reaction with unprecedented accuracy. It has also enabled the discoveries of new reaction pathways or intermediates/transition states that are inaccessible in conventional ensemble experiments, which is critical to elucidating their intrinsic mechanisms. Thanks to the rapid development of single-molecule junction (SMJ) techniques, detecting chemical reactions via monitoring the electrical current through single molecules has received an increasing amount of attention and has witnessed tremendous advances in recent years. Research efforts in this direction have opened a new route for probing chemical and physical processes with single-molecule precision. This review presents detailed advancements in probing single-molecule chemical reactions using SMJ techniques. We specifically highlight recent progress in investigating electric-field-driven reactions, reaction dynamics and kinetics, host–guest interactions, and redox reactions of different molecular systems. Finally, we discuss the potential of single-molecule detection using SMJs across various future applications.
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