A5016779525- Molecular Junctions and Nanostructures
- Advanced biosensing and bioanalysis techniques
- DNA and Nucleic Acid Chemistry
- 2D Materials and Applications
- Quantum Dots Synthesis And Properties
- Perovskite Materials and Applications
- Chalcogenide Semiconductor Thin Films
- Photonic and Optical Devices
- Terahertz technology and applications
- Organic Electronics and Photovoltaics
- Spectroscopy and Quantum Chemical Studies
- Microwave Engineering and Waveguides
- Semiconductor materials and interfaces
- Plasmonic and Surface Plasmon Research
- Spectroscopy and Laser Applications
- Graphene research and applications
- Strong Light-Matter Interactions
- Semiconductor Quantum Structures and Devices
- Thermal Radiation and Cooling Technologies
- Photochemistry and Electron Transfer Studies
- RNA Interference and Gene Delivery
- MXene and MAX Phase Materials
- Photonic Crystals and Applications
- Semiconductor materials and devices
- Fullerene Chemistry and Applications
United States Naval Research Laboratory
2016-2025
Chalmers University of Technology
2018
Space Information Laboratories (United States)
2018
North Carolina State University
2018
The Aerospace Corporation
2016
George Washington University
2016
K Lab (United States)
2012-2014
University of Maryland, Baltimore County
2006-2011
University of Washington
2009
University of Maryland, Baltimore
2007-2009
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Paul D. Cunningham, Nestor N. Valdes, Felipe A. Vallejo, L. Michael Hayden, Brent Polishak, Xing-Hua Zhou, Jingdong Luo, Alex K.-Y. Jen, Jarrod C. Williams, Robert J. Twieg; Broadband terahertz characterization of the refractive index absorption some important polymeric organic electro-optic materials. Appl....
Strong Coulomb attraction in monolayer transition metal dichalcogenides gives rise to tightly bound excitons and many-body interactions that dominate their optoelectronic properties. However, this interaction can be screened through control of the surrounding dielectric environment as well applied voltage, which provides a potential means tuning bandgap, exciton binding energy, emission wavelength. Here, we directly show bandgap energy optically tuned by intensity incident light. Using...
We report subpicosecond carrier dynamics in photoexcited solid films of regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) and a blend P3HT/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) using optical-pump terahertz-probe spectroscopy for excitations well above below the generally accepted energy gap P3HT. Both 400 nm excitation 800 yield similar results, suggesting same photoproduct results from these two different energies. The time evolution frequency-dependent complex conductivity...
The creation of a single electron-hole pair (i.e., exciton) per incident photon is fundamental limitation for current optoelectronic devices including photodetectors and photovoltaic cells. prospect multiple exciton generation great interest to science the improvement solar cell technology. Multiple known occur in semiconductor nanostructures with increased efficiency reduced threshold energy compared their bulk counterparts. Here we report significant enhancement PbSe quasi-one-dimensional...
There is keen interest in monolayer transition metal dichalcogenide films for a variety of optoelectronic applications due to their direct band gap and fast carrier dynamics. However, the mechanisms dominating dynamics are poorly understood. By combining time-resolved terahertz (THz) spectroscopy transient absorption, we able shed light on properties large area CVD grown mono- multilayer MoS2 determine origins characteristic two-component excited state The photoinduced conductivity shows...
Reduced dimensionality and strong Coulombic interactions in monolayer semiconductors lead to enhanced many-body interactions. Here, we report Auger recombination, i.e., exciton-exciton annihilation, large-area chemical vapor deposition-grown WS2. Using ultrafast spectroscopy, experimentally determine the rate be 0.089 ± 0.001 cm2/s at room temperature, which is an order of magnitude greater than bulk value. This nonradiative recombination pathway dominates, regardless excitation energy, for...
We report the far-infrared properties of organic crystal DAST, a popular terahertz emitter, from 0.6-12 THz through use spectrometer incorporating air-plasma generation and electro-optic (EO) sampling in poled EO polymer. identify absorption features at 1.1, 3.1, 5.2, 7.1, 8.4, 11, 12.3 1.3, 1.6, 2.2, 3, 7.2, 9.6 11.7 for a-axis b-axis polarized radiation respectively. These results allow more accurate prediction optimum thickness broadband emission via optical rectification difference...
Abstract Breaking the valley degeneracy in monolayer transition metal dichalcogenides through valley-selective optical Stark effect (OSE) can be exploited for classical and quantum valleytronic operations such as coherent manipulation of superposition states. The strong light-matter interactions responsible OSE have historically been described by a two-level dressed-atom model, which assumes noninteracting particles. Here we experimentally show that this works well semiconductors far from...
We examine the effect of electronic coupling on optical properties Cy3 dimers attached to DNA duplexes as a function base pair (bp) separation using steady-state and time-resolved spectroscopy. For close Cy3-Cy3 separations, 0 1 bp between dyes, intermediate strong is revealed by modulation absorption fluorescence including spectral band shape, peak wavelength, excited-state lifetime. Using vibronic exciton model, we estimate strengths 150 266 cm-1 for respectively, which are comparable...
Because of their ease design and assembly, DNA scaffolds provide a valuable means for organizing fluorophores into complex light harvesting antennae. However, as the size complexity DNA–fluorophore network grows, it can be difficult to fully understand energy transfer properties because large number dipolar interactions between fluorophores. Here, we investigate simple networks that represent elements more insight Förster Resonance Energy Transfer (FRET) processes in presence multiple...
We review recent research using organic materials for generation and detection of broadband terahertz radiation (0.3 THz-30 THz).The main focus is on amorphous electrooptic (EO) polymers, with semiconducting molecular salt EO crystals, solutions briefly discussed.The advantages polymers over other THz (via optical rectification) sampling) include a lack phonon absorption (good transparency) in the regime, high coefficient good phase-matching properties, and, course, easy fabrication (low...
The growing maturity of DNA-based architectures has raised considerable interest in applying them to create photoactive light harvesting and sensing devices. Toward optimizing efficiency such structures, resonant energy transfer was systematically examined a series dye-labeled DNA duplexes where donor-acceptor separation incrementally changed from 0 16 base pairs. Cyanine dyes were localized on the using double phosphoramidite attachment chemistry. Steady state spectroscopy, single-pair...
Photocurrent in an organic solar cell is generated by a charge transfer reaction between electron donors and acceptors. Charge expected to proceed from thermalized states, but this picture has been challenged recent studies that have investigated the role of hot excitons. Here we show direct link excess excitation energy photocarrier mobility. excited donor molecules generates photocarriers with coming offset lowest unoccupied molecular orbital acceptor. Hot manifest themselves through...
Abstract DNA‐based photonic wires that exploit Förster resonance energy transfer (FRET) between pendant fluorophores to direct and focus excitonic have high research interest due their potential applications in light harvesting, biocomputing, biosensing. One important goal with these structures is increase ability harvest then it over multiple steps both across extended portions of the spectra physical space. Toward goals, incorporating homogeneous or homoFRET sections into three unique FRET...
Femtosecond (fs) laser pulsed excitation of plasmonic nanoparticle (NP)–biomolecule conjugates is a promising method to locally heat biological materials. Studies have demonstrated that fs pulses light can modulate the activity DNA or proteins when attached NPs; however, precision over subsequent function remains largely undetermined. Specifically, temperature localized biomolecules "experience" unknown. We used 55 nm gold nanoparticles (AuNPs) displaying double-stranded (ds) examine how,...
Molecular excitons, which propagate spatially via electronic energy transfer, are central to numerous applications including light harvesting, organic optoelectronics, and nanoscale computing; they may also benefit such as photothermal therapy photoacoustic imaging through the local generation of heat rapid excited-state quenching. Here we show how tune between transfer quenching for heterodimers same pair cyanine dyes by altering their spatial configuration on a DNA template. We assemble...
Bismuth has been investigated as a potential n-type dopant in hybrid lead halide perovskites, but its behavior all-inorganic perovskites such CsPbBr3 not thoroughly characterized. We show that Bi behaves deep defect and gives rise to broad near-infrared emission, similar phenomenon previously reported CsPbBr3. Using inverse temperature crystallization, we synthesized series of Bi-doped crystals quantified their concentrations by inductively coupled plasma optical emission spectroscopy....
While coupling between optical, electronic, and mechanical domains is paramount for high-frequency acoustic devices, materials that offer tunability in the degree of such can be crucially enabling expanding device functionality. Here, we show interaction photons with coherent phonons confined 2D layered semiconducting cavities controlled through either modifying material state via a thermally induced electronic bandgap shift (EBS) or altering polarization incoming when optical birefringence...
The engineering and manipulation of delocalized molecular exciton states is a key component for artificial biomimetic light harvesting complexes as well alternative circuitry platforms based on propagation. Here we examine the consequences strong electronic coupling in cyanine homodimers DNA duplex scaffolds. most closely spaced dyes, attached to positions directly across double-helix from one another, exhibit pronounced Davydov splitting due coupling. We demonstrate that scaffold...
There has been significant interest in using DNA origami nanostructures as scaffolds to organize dye molecules into networks for a variety of applications. Such rely on having efficient energy—and/or electron—transport processes, and these turn depend sensitively the relative distance orientation molecules. In scaffold, crucial question is what extent can it control position orientation? The ability dictate reasonably well addressed literature, but much less known about potential controlling...
Dyes coupled to DNA display distance-dependent vibronic couplings that prolongs quantum coherences detected with 2D spectroscopy.
DNA-scaffolded molecular photonic wires (MPWs) displaying prearranged donor–acceptor chromophore pairs that engage in extended Förster resonance energy transfer (FRET) cascades represent an emerging nanoscale material with numerous potential applications data storage, encryption, and communications. For translation to such applications, these devices must first demonstrate robust performance high efficiencies over distances. Here, we report the optimization of FRET a 6-helix DNA origami...
Controlling exciton coupling in DNA templated dye aggregates is achieved by modifying sterics and hydrophobicity of Cy5-R dyes (varying the 5,5′-substituents). We conclude that play main role orientation strength.
We elucidate photoexcitation dynamics in ${\mathrm{C}}_{60}$ and zinc phthalocyanine (ZnPc) from picoseconds to milliseconds by transient absorption time-resolved terahertz spectroscopy. Autoionization of is a precursor photocarrier generation. Decay the signal due decreasing mobility over first 20 ps thereafter reflects recombination dynamics. Singlet diffusion rates are determined modeling rise ground state bleaching ZnPc following excitation. Recombination transform bimolecular...