A5022938293- Quantum Dots Synthesis And Properties
- Perovskite Materials and Applications
- Spectroscopy and Quantum Chemical Studies
- RNA Research and Splicing
- Molecular Junctions and Nanostructures
- 2D Materials and Applications
- Lanthanide and Transition Metal Complexes
- Photosynthetic Processes and Mechanisms
- Luminescence Properties of Advanced Materials
- Gold and Silver Nanoparticles Synthesis and Applications
- Heat shock proteins research
- Protein Structure and Dynamics
- Molecular spectroscopy and chirality
- Chalcogenide Semiconductor Thin Films
- Photoreceptor and optogenetics research
- Conducting polymers and applications
- Atmospheric Ozone and Climate
- Photochemistry and Electron Transfer Studies
- ZnO doping and properties
- Advanced Chemical Physics Studies
- Organic Light-Emitting Diodes Research
- Carbon Nanotubes in Composites
- Spectroscopy and Laser Applications
- Machine Learning in Materials Science
- Optical properties and cooling technologies in crystalline materials
Northwestern University
2018-2022
California Institute of Technology
2022
Division of Chemistry
2022
International Institute for Nanotechnology
2021
University of California, Berkeley
2016
Fixing cells with paraformaldehyde (PFA) is an essential step in numerous biological techniques as it thought to preserve a snapshot of biomolecular transactions living cells. Fixed-cell imaging such immunofluorescence have been widely used detect liquid–liquid phase separation (LLPS) vivo. Here, we compared images, before and after fixation, expressing intrinsically disordered proteins that are able undergo LLPS. Surprisingly, found PFA fixation can both enhance diminish putative LLPS...
Colloidal semiconductor nanocrystals, or quantum dots (QDs), show great promise as light absorbers and emitters in next-generation optoelectronic devices, but deleterious charge energy-transfer processes that occur solid-state thin films of QDs hinder their wide-scale utilization. Several classes materials have been used previously to encapsulate the solid state failed fully prevent energy transfer densely packed relevant for device applications, necessitating exploration other materials....
This paper describes reversible "on–off" switching of the photoluminescence (PL) intensity CdSe quantum dots (QDs), mediated by photochromic furylfulgide carboxylate (FFC) molecules chemisorbed to surfaces QDs. Repeated cycles UV and visible illumination switch FFC between "closed" "open" isomers. Reversible QDs' PL >80% is enabled different rates yields PL-quenching photoinduced electron transfer (PET) from QDs respective difference consistent with cyclic voltammetry measurements density...
Lattice defects play an important role in determining the optical and electrical properties of monolayer semiconductors such as MoS2. Although structures various MoS2 are well studied, little is known about nature fluorescent defect species their interaction with molecular adsorbates. In this study, quenching low-temperature photoluminescence (PL) investigated following deposition metallophthalocyanines (MPcs). The found to significantly depend on identity phthalocyanine metal, efficiency...
The behavior of ions at aqueous interfaces influences vital processes in many fields but has long remained a subject controversy. Over the past decade, counterintuitive surface concentration enhancement several solution been demonstrated via nonlinear laser spectroscopy and mass spectrometry. While evidence for significant ion air–water interface is convincing, mechanism remains incompletely understood. Toward this end, we present full broadband DUV-SFG spectrum charge-transfer-to-solvent...
Mapping the multidimensional energy landscape of photosynthetic systems is crucial for understanding their high efficiencies. Multidimensional coherent spectroscopy well suited to this task but has difficulty distinguishing between vibrational and electronic degrees freedom. In pigment–protein complexes, differences vibrations within a single manifold are similar states, leading ambiguous assignments spectral features diverging physical interpretations. An important control experiment that...
Colloidal semiconductor nanoplatelets (NPLs) are a scalable materials platform for optoelectronic applications requiring fast and narrow emission, including spin-to-photon transduction within quantum information networks. In particular, three-particle negative trions of NPLs appealing emitters since, unlike excitons, they do not have an optically "dark" sublevel. CdSe NPLs, trion emission dominates the photoluminescence (PL) spectrum at low temperature but using them as single...
The study of coherence between excitonic states in naturally occurring photosynthetic systems offers tantalizing prospects for uncovering mechanisms efficient energy transport.
As the number of hybrid systems comprising quantum-confined semiconductor nanocrystals and molecules continues to grow, so does need accurately describe interfacial energy charge transfer in these systems. The earliest work often successfully captured at least qualitative trends rates processes using well-known results from Förster, Dexter, Marcus theories, but recent studies have showcased how unique properties drive (EnT) (CT) diverge familiar trends. This review first describes...
Cesium-halide perovskite quantum dots (QDs) have gained tremendous interest as emitters in information processing applications due to their optical and photophysical properties. However, engineering excitonic states requires a deep knowledge of the coherent dynamics excitons at single-particle level. Here, we use femtosecond time-resolved two-photon near-field scanning microscopy (NSOM) reveal coherences involving single cesium lead bromide QD (CsPbBr3) room temperature. We show that,...
Trivalent lanthanide ions (Ln3+) have electronically isolated f-orbitals that support excited states, which, due to their ultra-narrow emission and long spin coherence lifetimes, are potentially suitable as hosts for qubits. These states must however be generated through photosensitization the low-absorption cross sections of Ln3+. This paper describes mechanism Yb3+ Sm3+ by CsPbCl3 perovskite nanocrystal (NC) host matrices, examination photophysical processes in NCs doped with seven...
This study explores the mechanisms of long-range energy transfer (EnT) from a self-assembled film CdSe/ZnS core–shell quantum dots (QDs) to exfoliated black phosphorus (BP) nanoflakes through an AlOx encapsulation layer variable thickness. The dependence EnT rate on donor–acceptor distance, d, scales as ∼d–2.3, which is shallower than expected scaling for Förster-type zero-dimensional (0D) donor 2D or 3D acceptor. Electrodynamic simulations reveal that efficient primarily attributable high...
Photosynthetic organisms exploit interacting quantum degrees of freedom, namely intrapigment electron-vibrational (vibronic) and interpigment dipolar couplings (J-coupling), to rapidly efficiently convert light into chemical energy. These interactions result in wave function configurations that delocalize excitation between pigments pigment vibrations. Our study uses multidimensional spectroscopy compare two model photosynthetic proteins, the Fenna–Matthews Olson (FMO) complex harvesting 2...
Intermittent periods of low light emission ("blinking") and time-dependent spectra (spectral diffusion, SD) have proven to be major obstacles the adoption colloidal semiconductor nanocrystals as quantum emitters. One clue mechanisms behind these two phenomena is how they are related, which difficult determine at time scales faster than can captured using a spectrometer (∼100 ms). This work utilizes spectral correlations access range from 10 μs s determines that, for quasi-2D CdSe/CdS...
We demonstrate that high-dimensionality coherent spectroscopy yields "super-resolved" spectra whereby peaks may be localized far below their homogeneous line width by resolving them across multiple, coherently coupled dimensions. implement this technique using a fifth-order photon-echo called Gradient-Assisted Multidimensional Electronic–Raman Spectroscopy (GAMERS) combines resonant and nonresonant excitation to disperse the optical response three spectral dimensions: two involving excitonic...
A versatile approach for synthesizing Yb3+- and Er3+-doped NaYF4 upconversion nanoparticle (UCNP) arrays is presented. The nanoparticles are positioned at precisely defined locations through the tip-directed deposition of polyol nanoreactors subsequent thermal conversion. This method based on conducting a solution-phase synthesis in nanometer-scale reactors, which provide isolated confined reaction vessels decomposition fluoride precursor coarsening nanoparticles. When annealed 350 °C,...
Abstract Fixing cells with paraformaldehyde (PFA) is an essential step in numerous biological techniques as it thought to preserve a snapshot of biomolecular transactions living cells. Fixed cell imaging such immunofluorescence have been widely used detect liquid-liquid phase separation (LLPS) vivo . Here, we compared images, before and after fixation, expressing intrinsically disordered proteins that are able undergo LLPS. Surprisingly, found PFA fixation can both enhance diminish putative...
The excited states of lanthanide ions (Ln3+) exhibit ultranarrow emission and long spin dephasing lifetimes suitable for optoelectronic quantum applications but are not directly optically accessible. One effective strategy to excite Ln3+ is dope them into a semiconductor host lattice, which acts as photosensitizer. This work describes enhancement intensity by factor 19 with decreasing temperature (from 300 5 K) from Sm3+ in CsPbCl3 nanocrystal hosts. Structural characterization over the same...
Low energy vibrations in the excited state have been hypothesized to play an important role quickly and efficiently generating free charges bulk heterojunctions of some conjugated polymer systems. While time-resolved vibrational spectroscopies seemingly are well poised address relationship between kinetics motions after initial photoexcitation, uncertainty measurement arises due overlapping signals difficulties assigning observed oscillatory molecular response. Here, we demonstrate a high...
Nadia Korovina opened discussion of the paper by Emily Weiss: Can you rule out possibility singlet energy transfer from acene to nanoparticle, followed triplet nanoparticle as a possible explanation for faster growth population
Overlapping contributions from ground and excited state signals cloud interpretation of 2-Dimensional Electronic Spectroscopy. Using non-resonant interactions to suppress pathways, unambiguous assignment coherences is obtained for Light Harvesting Complex II.
Lanthanides are narrow-linewidth sources of intense emission, and their complex electronic structure allow for non-linear processes such as quantum cutting. Their extinction coefficients however extremely low, so emission needs to be sensitized by a neighboring chromophore or host matrix. This talk describes mechanism photosensitization lanthanide ions (Ln 3+ ) substitutionally doped into CsPbCl 3 colloidal dots (QDs). involves charge transfer intermediate state, QD + -Ln 2+ , resulting from...
Colloidal Semiconductor Nanocrystals offer a potential path forward to lowering the bar for access Quantum Emitters. While demonstrations of single photons from nanocrystals have existed two decades, intermittent periods low light emission ("blinking") and transient multiple emissive states ("spectral diffusion") limited usefulness these sources. One underlying clue mechanism causing phenomena is whether or not effects are related. evidence blinking at fast timescales (~10s us) observable...
The electronically isolated f-orbitals of Ln3+ ions endow these species ultranarrow (atom-like) emission with a long lifetime, which are suitable for the optical generation and propagation spin qubits, even after coordination inside semiconductor matrices. To overcome low extinction coefficient ions, indirect sensitization via energy transfer from perovskite quantum dots (QDs) is performed through partial substitution matrix ions. Here, we suggest charge type intermediate involved in...