Mariam Kurashvili´s work on the multifunctional ligands for perovskite Quantum Dots was recently published in ACS Energy Letters!
Read about it here:
https://pubs.acs.org/doi/10.1021/acsenergylett.5c00881
" To enhance charge carrier extraction or injection, donor/acceptor molecules can be tethered to the pQD. This is achieved by using multifunctional ligands containing a quaternary ammonium binding group for strong pQD surface attachment, a long tail group for colloidal stability, and a functional group near the pQD surface. Such pQDs with ferrocene-functionalized ligands show fast photoexcited hole transfer with near-unity efficiency. This approach can also be extended to photoexcited electron and energy transfer processes with pQDs. Therefore, this strategy offers a blueprint for creating efficient pQD–molecular hybrids for applications like photocatalysis."
I recently presented our work titled "Perovskite Quantum Dots: From synthesis to their surface chemistry" on the International Conference on Metal Halide Perovskites 2024 at the National Institute of Science Education and Research, Bhubaneswar, India
Anja Barfüßer´s work on the biexcitonic optical gain in CsPbBr3 Quantum Dots was recently published in ACS Photonics!
Read about it here:
https://pubs.acs.org/doi/10.1021/acsphotonics.4c01659
"Here we study amplified spontaneous emission and optical gain of monodisperse spherical CsPbBr3 QDs and conclusively assign the gain to biexcitons. This is based on the gain threshold and its spectral position which we study via femtosecond transient absorption spectroscopy. Furthermore, the optical gain vanishes within 30 ps, matching the biexciton lifetime, demonstrating the strong correlation to the biexciton population. By identifying the intrinsic mechanism of optical gain in CsPbBr3 QDs and its limiting factors, our findings show the direction for future work on optimizing their gain threshold and lifetime."
Mariam Kurashvili´s work on the energy transfer between perovskite quantum dots and closely-bound dye molecules was recently published in Angewandte Chemie!
Read about it here:
https://doi.org/10.1002/anie.202420658
"This work designs a perovskite quantum dot (QD)-dye system for efficient energy transfer (ET) from QDs to dyes occurring via the Dexter exchange-type interaction, at minimal donor-acceptor spectral overlap. Dyes containing a dimethyl iminium binding group as part of their conjugated system are chosen for high binding affinity to QD surface, crucial for donor-acceptor spatial wavefunction overlap for efficient ET."
Mariam Kurashvili´s poster on Dexter Energy Transfer from Quantum Dots to Closely-Bound Dye Molecules (presented by Lena Stickel) just won a Poster Award at the 13th SolTech Conference in Nürnberg
"The 13th SolTech Conference is organized by FAU Erlangen-Nürnberg and will take place from Sept. 25 (noon) – 27, 2024 in Nürnberg in the conference center of IHK Nürnberg. During this event international experts will present the current research and discuss with all members of the SolTech keylabs."
Patrick von Schwerin´s work on Manganese Doped Spheroidal CsPbCl3 Quantum Dots was recently published in JPCL.
Read about it here:
https://pubs.acs.org/doi/full/10.1021/acs.jpclett.4c00049
"In this work, we demonstrate the synthesis of size-tunable spheroidal CsPbCl3:Mn2+ QDs, which can be obtained by a water–hexane interfacial combined anion and cation exchange strategy starting from CsPbBr3 QDs. Interestingly, the QDs exhibit a fast 0.2 ms Mn2+ photoluminescence (PL) lifetime and an energy transfer (ET) time of approximately 100 ps from the excitonic state of the QD to the atomic state of the Mn2+ ion."
Julian Mann´s poster on coherent phonons in double perovskite nanocrystals was recently awarded a poster prize at the PeroQuant24 symposium at the MATSUS24 conference in Barcelona!
Read about it here:
https://pubs.acs.org/doi/full/10.1021/acs.jpclett.3c03443
"Here, we report the detection of three modulation frequencies corresponding to coherent phonons in Ag-based double perovskite nanocrystals at distinct spectral positions at the bound exciton resonance."
Fei He´s work on the Silver-Nanoclusters and Vacancies Influence the Optical Properties of Spherical Cs2AgBiCl6 Nanocrystals was recently published in Advanced Optical Materials.
Read about it here:
https://onlinelibrary.wiley.com/doi/10.1002/adom.202302898
"We show that the presence of silver vacancies results in the redemission (650 nm) with an activated temperature dependence, whereas the blue emission (425 nm) stems from the lecithin lig-ands spectrally overlapping with the plasmon resonance of thesurface-attached Ag nanoclusters."
A small overview of some of our work onPerovskite Quantum Dots at the
we work at was pulished in latest edition of the Bunsen-Magazin of the Deutsche Bunsen-Gesellschaft fur der physikalischen Chemie.
It’s also OpenAccess so free for anyone who is interested!
https://bunsen.de/bmo/the-fascinating-chemistry-of-perovskite-quantum-dots
"The Bunsen Magazine is the members' magazine of the German Bunsen Society and also an important specialist publication on topics in physical chemistry. It has been published under this name since 1999 and reports on current and relevant developments in the fields of physical chemistry, the activities of the DBG, the job market and much more.."
Julian Mann´s work on the coherent phonons in double perovskite nanocrystals was recently published in JPCL.
Read about it here:
https://pubs.acs.org/doi/full/10.1021/acs.jpclett.3c03443
"Here, we report the detection of three modulation frequencies corresponding to coherent phonons in Ag-based double perovskite nanocrystals at distinct spectral positions at the bound exciton resonance."
We just won the CeNS Best junior scientist publication for our work on Quantum Dot Metal Salt Interactions Unraveled by the Sphere of Action Model!
https://www.cens.de/research/cens-publication-award/cens-award-2023/
"Every year, CeNS awards prizes for excellent publications of CeNS members which have been published during the past 12 months. With this award, remarkably successful cooperation projects within CeNS as well as outstanding research of an individual research group of CeNS were distinguished."
The Nobel Prize in Chemistry 2023 was awarded to Moungi G. Bawendi, Louis E. Brus and Alexei I. Ekimov "for the discovery and synthesis of quantum dots"
https://www.nobelprize.org/prizes/chemistry/2023/summary/
"The Nobel Prize in Chemistry 2023 rewards the discovery and development of quantum dots,nanoparticles so tiny that their size determines theirproperties. These smallest components of nanotechnology now spread their light from televisions andLED lamps, and can also guide surgeons when they remove tumour tissue, among many other things."
I recently joined the Solartechnologies go hybrid project as a PI.
https://www.soltech-go-hybrid.de/
"SolTech is an interdisciplinary project initiated by the government of Bavaria to explore innovative concepts for converting solar energy into electricity and non-fossil fuels. SolTech complements research by chemists and physicists at five different Bavarian Universities and is funded with 50 million Euro."
I recently was awarded the LMU excellent Junior Researcher Fund for "Heterostructured, hybrid perovskite quantum dots for the next generation of quantum and optoelectronic devices".
https://www.lmu.de/en/about-lmu/lmu-at-a-glance/awards/excellence-strategy/university-of-excellence/index.html
"The Junior Researcher Fund promotes the individual career development of junior academics by providing support for the independent procurement of externally funded and peer-reviewed research projects."
Our recent collaboration with Prof. Peter Müller-Buschbaum´s group on the fabrication of perovskite nanocrystal solar cells using slot-die coating is now online in Advanced Optical Materials!
"Here, a proof-of-concept study about slot-die coating (printing) the active layer of (Cs:FA)PbI3-based nanocrystal solar cells is presented."
I recently was awarded the CeNS investment fund for the "Watching perovskite nanocrystals crystals grow" project.
"To promote the scientific independence of postdoctoral researchers, CeNS is launching research grants up to € 8,000. With the CeNS Investment Fund, outstanding postdoctoral researchers at CeNS/LMU will be supported. Applications of female researchers are especially encouraged."
Our recent work on the quantum dot metal salt Interactions was fetuered on the front cover of the latest adition of JACS!
"A blueprint illustrates the sphere-of-action model for colloidal quantum dot solutions. This statistical model makes it possible to investigate quenching dynamics of quantum dots, described by an affinity factor. The model is used to pinpoint the role of corners for the structure-driven surface affinity and identify a single BiBr3 as an efficient quencher for CsPbBr3 quantum dots. "
Ilka Vinçon´s work on the interaction between CsPbBr3 quantum dots and BiBr3 salts was recently published in JACS. This is also my second work as leading corresponding author!
"Herein, we study this interaction based on the controlled PL quenching of CsPbBr3-QDs with BiBr3. Based on the so-called sphere of action model for the adsorption process, we show that already a single BiBr3 adsorption suffices to completely quench a QD’s luminescence. This approach is expanded to analyze size-, ligand-, and metal-dependent quenching dynamics. "
I recently joined the Center for NanoScience (CeNS) at the LMU.
"The mission of CeNS is to promote and coordinate interdisciplinary research in the field of nanoscience in the Munich area. CeNS is an association of junior and senior scientists from basic research and industry and is conceived as a network, joining people from various institutions (LMU, TU Munich, University of Augsburg and others)."
My second work, and follow up of the slow growth technique of CsPbBr3 quantum dots was, during my stay at the the KovalenkoLab at ETHZ was puplshed in Nano Letters!
"We report new insights into the nucleation, growth, and self-assembly in this reaction, obtained by in situ synchrotron-based small-angle X-ray scattering and optical absorption spectroscopy. We show that dispersed 3 nm Cs[PbBr3] agglomerates are the key intermediate species: first, they slowly nucleate into crystals, and then they release Cs[PbBr3] monomers for further growth of the crystals."
Anja Barfüßer just won the CeNS Scientific Breakthrough Publication Award with her Confined Excitons in Spherical-Like Halide Perovskite Quantum Dots puplication!
https://www.cens.de/research/cens-publication-award/cens-award-2022/
"Every year, CeNS awards prizes for excellent publications of CeNS members which have been published during the past 12 months. On Friday, November 25, the winners of this year's CeNS Publication Awards were announced online. Ten awards were presented in the categories "Best Interdisciplinary Publication", "Scientific Breakthrough" and "Best Junior Scientist Publication". With this award, remarkably successful cooperation projects within CeNS as well as outstanding research of an individual research group of CeNS were distinguished."
Amrita Dey just pulished her work on Fast electron and slow hole spin relaxation in CsPbI3 nanocrystals!
"Here, we introduce the soluble fullerene derivative PC60BM as an electron acceptor along with CsPbI3 to create an imbalance between the photoexcited electrons and holes in the NCs and, thus, affecting their spin-dependent carrier distribution. We ascribe the fast electron spin relaxation to the presence of strong spin–orbit coupling in the conduction band, which is ineffective for holes in the s-type valence band. "
Our recent work on the quantum dot metal salt Interactions has now been puplshied with a front cover in the latest adition of JACS!
"We show that for spherical-like CsPbBr3 QDs with diameters >6 nm, excitons are confined with respect to their center-of-mass motion leading to well-pronounced resonances in their absorption spectra. Optical pumping of the lowest-confined exciton not only bleaches all excitons but also reveals a series of distinct induced absorption resonances due to exciton-to-biexciton transitions. Our study provides the first insight into confined excitons in CsPbBr3 QDs and gives a detailed understanding of their linear and nonlinear optical spectra."
Anja Barfüßer´s work on Confined Excitons in Spherical-Like Halide Perovskite Quantum Dots was just puplished in Nano Letters!
"We show that for spherical-like CsPbBr3 QDs with diameters >6 nm, excitons confine with respect to their center-of-mass motion leading to well-pronounced resonances in their absorption spectra. The temporal dynamics of the bleached excitons further support our exciton confinement model. Our study provides the first insight into confined excitons in CsPbBr3 QDs and gives a detailed understanding of their linear and nonlinear optical spectra."
My first fully indepent work, which foccuses on CsPb(Cl:Br)3 quantum dots, was just puplished in Nano Letters!
"In this work, monodisperse spheroidal CsPb(Cl:Br)3 QDs are synthesized in the 4–10 nm range, at any Cl:Br ratio, with up to five excitonic absorption transitions. Furthermore, in situ spectroscopy was used to cross-correlate the size and composition of these QDs directly to the energy of the first two excitonic absorption transitions. "
My first author work during my stay at the the KovalenkoLab at ETHZ is now finally online at Science!
"Inorganic materials with more covalent bonding, such as cadmium selenide, form uniform nanoparticles under fast growth conditions, but perovskites such as cesium lead bromide (CsPbBr3) are more ionic and grow rapidly to form larger nanoparticles. Akkerman et al. controlled the nanoparticles’ growth kinetics by using trioctylphosphine oxide, which solubilized the PbBr2 precursor, bound to the cation-[PbBr3] monomer (solute), and weakly coordinated to the crystal nuclei surfaces. Nanoparticles with diameters from 3 to 13 nanometers were stabilized and isolated in high yield with lecithin, a long-chain zwitterion. Four well-resolved excitonic transitions with size-dependent confinement energies were seen for cesium as well as organic cations. "
After a long time, I decided to make a website that foccusses on scientific work. Here, you´ll find my work, my research intrest, as well as news and updates. Enjoy!
Dr. Q. A. Akkerman, Group Leader
Chair for Photonics and Optoelectronics
Nano-Institute Munich, Department of Physics
Ludwig-Maximilians-University Munich
80539 Munich, Germany
Q.Akkerman@lmu.de