Periodic Reporting for period 2 - MONOCLE (Emission Control of Rare-Earth Nanoparticles)
Reporting period: 2023-04-01 to 2024-03-31
Project MONOCLE (Logo 1) explores the optical properties of rare-earth doped nanoparticles (RENPs) envisioned to be used in various biomedical and technological applications. RENPs have a unique ability to convert invisible near-infrared light to visible colors via a process of upconversion. Such upconverting RENPs are researched for disease detection, drug delivery, and cell-level temperature sensing and are used as super-resolution optical probes. Successful implementation of these practices, though, depends on our ability to generate upconversion emissions effectively and controllably.
It is challenging to maximize upconversion properties of RENPs because of a large number of variables that influence the final performance of RENPs. Compositionally, a vast space of explorable parameters is determined by the choice of nanocrystal host and rare-earth dopants, their concentrations, and placement within the nanocrystal (so-called core/shell engineering). Furthermore, the photoluminescence of RENPs is affected by the wavelength, power, and temporal modulations (pulsing) of laser excitation that, in turn, can serve as a means to control RENP emission deliberately. Thus, to effectively cover these parameter spaces and create application-targeted RENPs in a timely fashion, high-throughput numerical and experimental approaches have to be combined with the rational design of RENPs.
This project aims to explore different RENP architectures, including highly nonlinear photon avalanching nanoparticles (ANPs) and their excitation pathways to aid in creating a set of specialized nanotools for future biomedical and technological applications. To reach different milestones of the project, numerical simulations, high-throughout robotic synthesis, and complete optical characterization are combined to create and investigate state-of-the-art RENPs. In turn, these approaches and guiding principles were successfully applied in the course of project MONOCLE, yielding 1) the synthesis method for a new class of host material for RENPs, 2) the development of a generalized approach to tune the color of photon avalanches and imprint photon avalanches on virtually any linear emitter, and 3) the discovery of an extremely nonlinear photoactivation dynamic that transforms ANPs into bistable ANPs - having two distinct steady-state responses under identical excitation conditions, contingent on the history of excitation intensity.
These research accomplishments have been successfully published in the highest-impact chemical and physical journals and presented at international conferences, thus garnering interest and acclaim from the scientific community. The disseminated results are expected to impact and advance the fields of super-resolution imaging, sensing, and general-purpose optical data handling. Furthermore, this project had a valuable impact on the career development of the beneficiary, aiding in strengthening existing collaborations, forging new ones, and allowing to establish the beneficiary as an independent and goal-oriented researcher.
It is challenging to maximize upconversion properties of RENPs because of a large number of variables that influence the final performance of RENPs. Compositionally, a vast space of explorable parameters is determined by the choice of nanocrystal host and rare-earth dopants, their concentrations, and placement within the nanocrystal (so-called core/shell engineering). Furthermore, the photoluminescence of RENPs is affected by the wavelength, power, and temporal modulations (pulsing) of laser excitation that, in turn, can serve as a means to control RENP emission deliberately. Thus, to effectively cover these parameter spaces and create application-targeted RENPs in a timely fashion, high-throughput numerical and experimental approaches have to be combined with the rational design of RENPs.
This project aims to explore different RENP architectures, including highly nonlinear photon avalanching nanoparticles (ANPs) and their excitation pathways to aid in creating a set of specialized nanotools for future biomedical and technological applications. To reach different milestones of the project, numerical simulations, high-throughout robotic synthesis, and complete optical characterization are combined to create and investigate state-of-the-art RENPs. In turn, these approaches and guiding principles were successfully applied in the course of project MONOCLE, yielding 1) the synthesis method for a new class of host material for RENPs, 2) the development of a generalized approach to tune the color of photon avalanches and imprint photon avalanches on virtually any linear emitter, and 3) the discovery of an extremely nonlinear photoactivation dynamic that transforms ANPs into bistable ANPs - having two distinct steady-state responses under identical excitation conditions, contingent on the history of excitation intensity.
These research accomplishments have been successfully published in the highest-impact chemical and physical journals and presented at international conferences, thus garnering interest and acclaim from the scientific community. The disseminated results are expected to impact and advance the fields of super-resolution imaging, sensing, and general-purpose optical data handling. Furthermore, this project had a valuable impact on the career development of the beneficiary, aiding in strengthening existing collaborations, forging new ones, and allowing to establish the beneficiary as an independent and goal-oriented researcher.
Despite COVID restrictions at the start of the project (started April 2021), significant progress was made using numerical simulations that aided in uncovering ways to modulate the emission of upconverting nanoparticles, particularly that of ANPs, using pulsed excitation. Simulation results allowed the identification of nanoparticle compositions (dopants and doping percentages), excitation wavelengths, and pulsing parameters (pulse width and period) that would result in an enhancement of photon avalanche emission nonlinearity - a crucial factor in the use of these nanoparticles as super-resolution imaging probes. In addition, simulation results were used to devise a strategy for photon avalanche spectral tuning, which has the potential to unlock ANPs for multicolor imaging and multiplexed sensing applications.
Informed by numerical simulations, ANPs that combine photon avalanching and energy migration upconversion were created (Figure 1). The spectral tuning of ANPs, in which virtually any Ln3+ ion could be excited in a highly nonlinear fashion, was achieved by utilizing a Tm3+ → Gd3+ → Ln3+ energy transfer cascade initiated under a 1064 nm laser pump. A library of core/multishell ANPs was successfully synthesized, with Er3+, Ho3+, Tb3+, Eu3+, Nd3+, or Dy3+ dopants as visible light emitters. This approach allowed to generate upconversion emission from different Ln3+ ions, including the non-upconverting ones (i.e. Tb3+, Dy3+, and Eu3+), with upconversion nonlinearities, s, up to 17 (compared to s = 2-5 for classic upconversion). All the synthesis, structural characterization, and spectroscopy results have been published (Nano Letters, 23, 15, 7100–7106, 2023).
Furthermore, novel low-phonon-energy upconverting RENPs were developed during this project in collaboration with Dr. Zhuolei Zhang at the Partner Organization (Figure 2). Reducing the phonon energies of host material can potentially boost the upconversion emission intensity, yet it is challenging to synthesize low-phonon-energy upconverting nanocrystals. Different compositions of KPb2X5 (X = Cl, Br) RENPs with the lowest phonon energies available were synthesized and characterized by developing a new synthesis approach. Successful development of these RENPs facilitated lowering the host matrix's phonon energies to the extent that photon avalanching emission in Nd3+-doped KPb2Cl5 under 1064 nm excitation could be observed for the first time. Photon avalanching with Nd3+ has been predicted theoretically, however, previous attempts to detect it in the stat-of-the-art hosts (e.g. NaYF4 or NaGdF4) have been unsuccessful. Results of this study were published in Angewandte Chemie International Edition, 62, e202212549, 2023. The published manuscript was also deemed a "Hot Paper" and highlighted by a frontispiece graphic.
Overall, this project's results have been published in 5 high-impact peer-reviewed journals, and 2 more articles are under peer review for publication. Furthermore, the beneficiary disseminated the results at 8 international meetings/seminars, 4 of which were invited talks.
Informed by numerical simulations, ANPs that combine photon avalanching and energy migration upconversion were created (Figure 1). The spectral tuning of ANPs, in which virtually any Ln3+ ion could be excited in a highly nonlinear fashion, was achieved by utilizing a Tm3+ → Gd3+ → Ln3+ energy transfer cascade initiated under a 1064 nm laser pump. A library of core/multishell ANPs was successfully synthesized, with Er3+, Ho3+, Tb3+, Eu3+, Nd3+, or Dy3+ dopants as visible light emitters. This approach allowed to generate upconversion emission from different Ln3+ ions, including the non-upconverting ones (i.e. Tb3+, Dy3+, and Eu3+), with upconversion nonlinearities, s, up to 17 (compared to s = 2-5 for classic upconversion). All the synthesis, structural characterization, and spectroscopy results have been published (Nano Letters, 23, 15, 7100–7106, 2023).
Furthermore, novel low-phonon-energy upconverting RENPs were developed during this project in collaboration with Dr. Zhuolei Zhang at the Partner Organization (Figure 2). Reducing the phonon energies of host material can potentially boost the upconversion emission intensity, yet it is challenging to synthesize low-phonon-energy upconverting nanocrystals. Different compositions of KPb2X5 (X = Cl, Br) RENPs with the lowest phonon energies available were synthesized and characterized by developing a new synthesis approach. Successful development of these RENPs facilitated lowering the host matrix's phonon energies to the extent that photon avalanching emission in Nd3+-doped KPb2Cl5 under 1064 nm excitation could be observed for the first time. Photon avalanching with Nd3+ has been predicted theoretically, however, previous attempts to detect it in the stat-of-the-art hosts (e.g. NaYF4 or NaGdF4) have been unsuccessful. Results of this study were published in Angewandte Chemie International Edition, 62, e202212549, 2023. The published manuscript was also deemed a "Hot Paper" and highlighted by a frontispiece graphic.
Overall, this project's results have been published in 5 high-impact peer-reviewed journals, and 2 more articles are under peer review for publication. Furthermore, the beneficiary disseminated the results at 8 international meetings/seminars, 4 of which were invited talks.
The aforementioned photon avalanche spectral tuning within RENPs was also generalized to imprint photon avalanching on other fluorophores, as showcased by extremely nonlinear QD upconversion in an ANP+QD avalanching complex. This is an important discovery since various highly nonlinear emitters can now be created with the help of RENPs, fostering the combination of unique properties between different nanostructures for augmented and enhanced performance. These results may impact the biomedical community, as spectrally discrete ANPs and avalanching complexes can be used in multicolor super-resolution imaging, high-sensitivity multiplex bioassays, and long-range molecular sensors.
Furthermore, the low-phonon-energy Nd3+-doped KPb2Cl5 nanocrystals were discovered to exhibit intrinsic optical bistability, namely, having two distinct steady-state outputs under identical input condition, dependent only on the history of the input (arXiv:2403.04098 2024). These nanocrystals represent the first demonstration of non-thermal intrinsic optical bistability at the nanoscale, having far-reaching implications in building optical networks for cost and energy-efficient data manipulation and storage.
Furthermore, the low-phonon-energy Nd3+-doped KPb2Cl5 nanocrystals were discovered to exhibit intrinsic optical bistability, namely, having two distinct steady-state outputs under identical input condition, dependent only on the history of the input (arXiv:2403.04098 2024). These nanocrystals represent the first demonstration of non-thermal intrinsic optical bistability at the nanoscale, having far-reaching implications in building optical networks for cost and energy-efficient data manipulation and storage.