Article
Chemistry, Physical
Dongmei Xiang, Yulu Li, Lifeng Wang, Tao Ding, Junhui Wang, Kaifeng Wu
Summary: In this study, the electron and hole spin dynamics in CdSe colloidal nanoplatelets of varying thicknesses were investigated using circularly polarized transient absorption spectroscopy. The results showed that hole spin-flip occurred within 200 fs, while the electron spin lifetime decreased as the platelet thickness was reduced. The findings suggest an exchange interaction between the electron and the hole, and/or surface dangling bond spins enhanced by quantum confinement.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Lifeng Wang, Dongmei Xiang, Kaimin Gao, Junhui Wang, Kaifeng Wu
Summary: Colloidal n-doped CdSe and CdSe/ZnS nanoplatelets have been achieved through a photochemical doping method, demonstrating successful additional electron doping at the conduction band edge. The key to successful doping lies in a high surface ligand coverage, while unpassivated surface cations may lead to depletion of the doped electrons.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Tom Galle, Daniel Spittel, Nelli Weiss, Volodymyr Shamraienko, Helena Decker, Maximilian Georgi, Rene Huebner, Nadia Metzkow, Christine Steinbach, Dana Schwarz, Vladimir Lesnyak, Alexander Eychmueller
Summary: The research transforms CdSe NPLs into PbSe NPLs suitable for optoelectronic applications through cation exchange, ligand exchange, and electronic coupling, successfully fabricating a photodetector with fast light response at low operational voltages on a commercial substrate.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Alexandra Brumberg, Nicolas E. Watkins, Benjamin T. Diroll, Richard D. Schaller
Summary: Colloidal semiconductor nanocrystals, such as CdSe nanoplatelets and quantum dots, offer advantages in optoelectronics but are affected by rapid nonradiative Auger recombination at high excitation intensities. This study investigates the temperature dependence of excited state lifetime and fluence-dependent emission, revealing fundamental differences between CdSe nanoplatelets and core-only quantum dots, and highlighting the increased utility of photogenerated excitons and multiexcitons at low temperatures.
Article
Chemistry, Physical
Benjamin T. Diroll, Richard D. Schaller
Summary: This study investigates the giant oscillator strength effect in CdSe nanoplatelets through temperature-dependent spectroscopy measurements. The results show that although lowering the temperature increases the oscillator strength of excitons, there remains a significant difference between the area of coherent exciton motion and the entire nanoplatelet area, indicating localization of excitons to much smaller regions than the whole nanoplatelet.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Arman Najafi, Manoj Sharma, Savas Delikanli, Arinjoy Bhattacharya, Joseph R. Murphy, James Pientka, Ashma Sharma, Alexander P. Quinn, Onur Erdem, Subash Kattel, Yusuf Kelestemur, Maksym Kovalenko, William D. Rice, Hilmi Volkan Demir, Athos Petrou
Summary: This study investigates light-induced magnetism in Ag+-doped CdSe nanoplatelets using magnetic circularly polarized luminescence and magnetic circular dichroism spectroscopy, confirming the presence of paramagnetism. The observed magnetism is attributed to the transformation of nonmagnetic Ag+ ions into Ag2+ with a nonzero magnetic moment, suggesting potential applications in spintronic devices.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Optics
Pieter Geiregat, Carmelita Roda, Ivo Tanghe, Shalini Singh, Alessio Di Giacomo, Delphine Lebrun, Gianluca Grimaldi, Jorick Maes, Dries Van Thourhout, Iwan Moreels, Arjan J. Houtepen, Zeger Hens
Summary: In this study, the researchers analyzed the oscillator strength of exciton transitions in 2D CdSe nanoplatelets using the optically induced Stark effect. They found that the actual oscillator strengths were 50 times smaller than expected based on linear absorption coefficients, suggesting that the exciton absorption line is a sum of low oscillator strength transitions. The authors propose that this discrepancy is due to strong exciton center-of-mass localization and suggest that thermal effects may contribute to exciton localization.
LIGHT-SCIENCE & APPLICATIONS
(2021)
Article
Chemistry, Physical
Da-Eun Yoon, Juho Lee, Hyeonwoo Yeo, Junga Ryou, Young Kuk Lee, Yong-Hoon Kim, Doh C. Lee
Summary: Shape anisotropy in colloidal zincblende CdSe nanoplatelets directly affects their optical and electronic properties. The lateral aspect ratio of NPLs provides a way to control their optical characteristics, such as polarized emission, by varying the shape while keeping the thickness constant. Experimental and simulation studies have shown that the growth behavior of CdSe NPLs can be altered by adjusting the Cd(ac)(2)-to-Se precursor ratio, leading to different growth directions. The mechanism for the lateral growth of zincblende NPLs has been explained at the atomic level, shedding light on the transition processes of NPL morphology and growth direction.
CHEMISTRY OF MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Sergey R. Meliakov, Vasilii V. Belykh, Ina V. Kalitukha, Aleksandr A. Golovatenko, Alessio Di Giacomo, Iwan Moreels, Anna V. Rodina, Dmitri R. Yakovlev
Summary: The coherent spin dynamics of electrons in CdSe colloidal nanoplatelets were investigated at different temperatures. The measurements revealed the g-factors of the nanoplatelets and the electron spin precession in a magnetic field. The results showed weak dependence of the spin dephasing time on temperature and the longitudinal spin relaxation time exceeding 10 ns even at room temperature. The observations also confirmed the negative charge of the nanoplatelets and revealed g-factor anisotropy.
Article
Chemistry, Physical
Arun Ashokan, Paul Mulvaney
Summary: Solution-phase spectroelectrochemistry was used to study electron injection into colloidal CdSe quantum dots in THF. The results showed reversible optical changes on a time-scale of minutes, with the injection of electrons leading to quenching of photoluminescence. The number of electrons injected into the QDs depended on the electrode potential and QD size, with most injection occurring below the band edge.
CHEMISTRY OF MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Carmelita Roda, Pieter Geiregat, Alessio Di Giacomo, Iwan Moreels, Zeger Hens
Summary: In this study, we used cross-polarized pump-probe spectroscopy to measure the absorption coefficient spectrum of the exciton-biexciton transition in colloidal CdSe nanoplatelets (NPLs) and determined the biexciton oscillator strength (fBX). We found that fBX is independent of the NPL area and agrees with predictions of a short-range interaction model.
Article
Chemistry, Physical
Clyde Midelet, Gaetan Petit, Simon Raffy, Yannick Hallez, Stephanie Mendes Marinho, Marc Pousthomis, Michele D'Amico, Francois Guerin, Etienne Palleau, Laurence Ressier
Summary: Combining experimental results and numerical simulations, we found that advection plays a major role in the directed trapping of nanoparticles. A deep understanding of the involved mechanisms and tuning of experimental parameters enable the fabrication of high-resolution quantum nanoplatelet-based micro-pixels with fine control of their lateral and vertical dimensions.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Alexander M. Smirnov, Anastasia D. Golinskaya, Vladimir N. Mantsevich, Maria Kozlova, Kseniia V. Ezhova, Bedil M. Saidzhonov, Roman B. Vasiliev, Vladimir S. Dneprovskii
Summary: Experimental investigations were conducted on the transient absorption of colloidal heterostructured CdSe/CdS nanoplatelets under high-intensity nanosecond laser pulses, revealing a strong dependence on nanoplatelets concentration and pump intensities. Nonlinear transmission changes in nanoplatelets solutions were explained by various factors, and the identification of conditions for optical gain in colloidal solutions was a significant result.
RESULTS IN PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
David F. Macias-Pinilla, Josep Planelles, Juan Climente
Summary: The biexciton properties in semiconductor nanostructures are influenced by quantum confinement, electron-hole masses, dielectric environment, and Coulomb correlations. A variational Quantum Monte Carlo model coupled to effective mass Hamiltonians is used to analyze the biexciton ground state properties in colloidal CdSe nanoplatelets. The results show that the thickness of the nanoplatelets leads to a distorted tetrahedral shape of the biexciton, and the strong dielectric confinement affects both Coulomb attractions and repulsions. The ratio of biexciton-to-exciton binding energy is reduced, but the biexciton can still be stable at room temperature. The ratio of biexciton-to-exciton radiative rates decreases as the platelet area increases.
Article
Chemistry, Multidisciplinary
Alexandra Brumberg, Matthew S. Kirschner, Benjamin T. Diroll, Kali R. Williams, Nathan C. Flanders, Samantha M. Harvey, Ariel A. Leonard, Nicolas E. Watkins, Cunming Liu, Eli D. Kinigstein, Jin Yu, Austin M. Evans, Yuzi Liu, Shelby A. Cuthriell, Shobhana Panuganti, William R. Dichtel, Mercouri G. Kanatzidis, Michael R. Wasielewski, Xiaoyi Zhang, Lin X. Chen, Richard D. Schaller
Summary: Time-resolved X-ray diffraction study reveals that photoexcitation induces greater out-of-plane disordering in 4 and 5 monolayer NPLs, while 3 ML NPLs display the opposite behavior. In comparison, disordering in zero-dimensional CdSe nanocrystals is isotropic and recovery is faster. These findings support the superior performance of NPLs in optoelectronic applications.
Article
Chemistry, Multidisciplinary
Hoang Long Nguyen, Thanh Nhut Do, Emek G. Durmusoglu, Merve Izmir, Ritabrata Sarkar, Sougata Pal, Oleg V. Prezhdo, Hilmi Volkan Demir, Howe-Siang Tan
Summary: In this study, the ultrafast spectral diffusion, vibronic dynamics, and energy relaxation of CdSe colloidal quantum wells (CQWs) at room temperature were measured using two-dimensional electronic spectroscopy (2DES). The energy relaxation from light-hole (LH) excitons to heavy-hole (HH) excitons was observed to occur within a time scale of approximately 210 fs. Equilibration dynamics between the spectroscopically accessible HH excitonic state and a dark state were found to take place within a time scale of approximately 160 fs. The spectral diffusion dynamics in HH excitons were analyzed using center line slope analysis, revealing a sub-200 fs decay and oscillatory features resolved at 4 and 25 meV. Quantum calculations were performed to replicate and explain the observed dynamics. The 4 meV mode was found to be in the near-critically damped regime and may mediate the transition between the bright and dark HH excitons. These findings demonstrate the capability of 2DES to comprehensively and detailedly characterize the ultrafast spectral properties in CQWs and similar nanomaterials.
Article
Materials Science, Multidisciplinary
Dmitry A. Tatarinov, Sergey S. Anoshkin, Ivan A. Tsibizov, Volodymyr Sheremet, Furkan Isik, Alexey Y. Zhizhchenko, Artem B. Cherepakhin, Aleksandr A. Kuchmizhak, Anatoly P. Pushkarev, Hilmi Volkan Demir, Sergey V. Makarov
Summary: A protocol to deposit large-grain and smooth CsPbBr3 thin films is developed, achieving high optical gain and excellent lasing characteristics. The critical roles of thickness and grain size for CsPbBr3 films with extremely high optical gain are revealed, opening up possibilities for low-threshold lasers and integrated photonic chips.
ADVANCED OPTICAL MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Resul Ozdemir, Hannes Van Avermaet, Onur Erdem, Pieter Schiettecatte, Zeger Hens, Tangi Aubert
Summary: Quantum dots (QDs) are extensively used as light emitters in photonic and optoelectronic applications. To prevent degradation of their optical properties, QDs must be encapsulated between barrier layers to shield them from oxygen and water vapor. A new approach for direct patterning of QDs through maskless lithography has been developed.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Roman A. Babunts, Yulia A. Uspenskaya, Nikolai G. Romanov, Sergei B. Orlinskii, Georgy V. Mamin, Elena V. Shornikova, Dmitri R. Yakovlev, Manfred Bayer, Furkan Isik, Sushant Shendre, Savas Delikanli, Hilmi Volkan Demir, Pavel G. Baranov
Summary: Semiconductor colloidal nanoplatelets based on CdSe with magnetic Mn2+ ions show modified magneto-optical and spin-dependent properties. High-frequency electron paramagnetic resonance techniques were used to study the spin structure and dynamics of Mn2+ ions in core/shell CdSe/(Cd,Mn)S nanoplatelets. Two sets of resonances were observed, indicating different spin dynamics between surface and inner Mn2+ ions. The interaction between surface Mn2+ ions and 1H nuclei was measured using electron nuclear double resonance, providing information on the distances between Mn2+ ions and 1H nuclei.
Article
Chemistry, Multidisciplinary
M. A. Masharin, A. K. Samusev, A. A. Bogdanov, I. V. Iorsh, H. V. Demir, S. V. Makarov
Summary: Excitons in lead bromide perovskites have a high binding energy and high oscillator strength, which enables strong light-matter coupling in perovskite-based cavities at the nanoscale. In this study, a perovskite metasurface fabricated with nanoimprint lithography is used to demonstrate room-temperature polariton lasing. The observed lasing emission has a high directivity and compatibility with various planar photonic platforms.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Chemistry, Physical
Farzan Shabani, Muhammad Ahmad, Satish Kumar, Savas Delikanli, Furkan Isik, Arinjoy Bhattacharya, Athos Petrou, Hilmi Volkan Demir
Summary: Two-dimensional (2D) core/shell nanoplatelets (NPLs) synthesized via the hot-injection method provide excellent thermal and chemical stability for high-temperature doping. A thermodynamic approach toward silver doping of these NPLs is proposed and demonstrated. The distribution of silver ions in the lattice of the NPLs directly affects the recombination dynamics and enables fine-tuning of the near-infrared emission.
CHEMISTRY OF MATERIALS
(2023)
Article
Chemistry, Physical
Merve Izmir, Emek G. Durmusoglu, Manoj Sharma, Farzan Shabani, Furkan Isik, Savas Delikanli, Vijay Kumar Sharma, Hilmi Volkan Demir
Summary: In this study, ytterbium (Yb) was successfully doped into cadmium selenide (CdSe) nanoplatelets (NPLs) using a modified seeded-growth method. The Yb-doped NPLs exhibited additional near-infrared (NIR) emission apart from their excitonic emission. By optimizing the dopant concentration, an impressive photoluminescence quantum yield (PL QY) of approximately 55% was achieved. Detailed elemental and optical characterizations were performed to understand the emerging photophysical properties of these Yb-doped NPLs. These lanthanide-doped CdSe NPLs emitting in the NIR range could find applications in next-generation bioimaging, night vision, and photodetection.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Optics
Yi Tian Thung, Rui Duan, Emek G. Durmusoglu, Yichen He, Lian Xiao, Calvin Xiu Xian Lee, Wen Siang Lew, Lin Zhang, Hilmi Volkan Demir, Handong Sun
Summary: Colloidal quantum wells (CQWs) are a promising gain material for optical feedback due to their unique excitonic features from 1D confinement, but current integration methods result in low laser quality. To address this, a liquid-interface kinetically driven self-assembly method is proposed to coat ultrathin CQWs onto silica microsphere cavities, achieving high-quality microlasers with a Q-factor of 13,000 at room temperature. Stable single-mode lasing output is demonstrated through evanescent field coupling in a 2D-3D microcavity configuration, highlighting the potential for future miniaturized colloidal optoelectronic and photonic applications.
LASER & PHOTONICS REVIEWS
(2023)
Article
Optics
Ahmet Tarik Isik, Farzan Shabani, Furkan Isik, Satish Kumar, Savas Delikanli, Hilmi Volkan Demir
Summary: Micro/nanoscale semiconductor multicolor lasers have great potential for improved photonic circuits. This work proposes and demonstrates multicolor optical gain and lasing from colloidal quantum wells (CQWs) in an all-solution processed optical cavity. A layered architecture with a transparent low refractive index colloidal spacing layer is designed to suppress nonradiative energy transfer and enable simultaneous amplified spontaneous emission in two colors. This architecture is adapted to a whispering-gallery-mode cavity, resulting in dual-color multimode lasing at 569 and 648 nm.
LASER & PHOTONICS REVIEWS
(2023)
Review
Chemistry, Physical
Joanna Dehnel, Adi Harchol, Yahel Barak, Itay Meir, Faris Horani, Arthur Shapiro, Rotem Strassberg, Celso de Mello Donega, Hilmi Volkan Demir, Daniel R. Gamelin, Kusha Sharma, Efrat Lifshitz
Summary: Incorporating magnetic ions into semiconductor nanocrystals is a promising research field for manipulating spin-related properties. Various host materials and magnetic ions have been studied, and the impact of nanostructure engineering and ion selection in carrier-magnetic ion interactions is emphasized. The use of optically detected magnetic resonance spectroscopy provides valuable insights into the spin dynamics and physical parameters of the carrier-magnetic ion interactions.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Manpreet Kaur, Ashma Sharma, Onur Erdem, Akshay Kumar, Hilmi Volkan Demir, Manoj Sharma
Summary: Doping of alloyed colloidal quantum dots (QDs) has gained attention for their tunable and Stokes-shifted emission. High-quality Cu and Mn-doped ZnxCd1-xS alloyed QDs were synthesized, and the addition of a ZnS shell significantly improved their quantum yield (QY).
Article
Chemistry, Multidisciplinary
Zeynep Dikmen, Ahmet Tarik Isik, Iklim Bozkaya, Hamed Dehghanpour Baruj, Betul Canimkurbey, Farzan Shabani, Muhammad Ahmad, Hilmi Volkan Demir
Summary: We propose and demonstrate the vertical self-assembly of colloidal quantum wells (CQWs) for amplified spontaneous emission (ASE) and random lasing. The CQWs are stacked in films using liquid-air interface self-assembly (LAISA) and controlled hydrophilicity/lipophilicity balance (HLB). By adjusting HLB with a more lyophilic subphase, large micron-sized areas of monolayer CQW stacks can be obtained. ASE and random lasing are achieved by depositing multi-layered CQW stacks onto a substrate using the Langmuir-Schaefer transfer method.
Article
Chemistry, Multidisciplinary
Taylan Bozkaya, Furkan Isik, Iklim Bozkaya, Savas Delikanli, Emre Unal, Hilmi Volkan Demir
Summary: A new class of light-sensitive nanocrystal skins (LS-NS) utilizing a monolayer of face-down orientation-controlled self-assembled CQWs as the active absorbing layer in the UV-visible range is developed, enabling non-conventional photosensing operation and self-powered operation.
