Recently developed all-organic emitters used in display applications achieve high brightness by h... more Recently developed all-organic emitters used in display applications achieve high brightness by harvesting triplet populations via thermally activated delayed fluorescence. The photophysical properties of these emitters therefore involve new inherent complexities and are strongly affected by interactions with their host material in the solid state. Ensemble measurements occlude the molecular details of how host−guest interactions determine fundamental properties such as the essential balance of singlet oscillator strength and triplet harvesting. Therefore, using time-resolved fluorescence spectroscopy, we interrogate these emitters at the single-molecule level and compare their properties in two distinct glassy polymer hosts. We find that nonbonding interactions with aromatic moieties in the host appear to mediate the molecular configurations of the emitters, but also promote nonradiative quenching pathways. We also find substantial heterogeneity in the time-resolved photoluminescence of these emitters, which is dominated by static disorder in the polymer. Finally, since singlet−triplet cycling underpins the mechanism for increased brightness, we present the first room-temperature measurement of singlet−triplet equilibration dynamics in this family of emitters. Our observations present a molecular-scale interrogation of host−guest interactions in a disordered film, with implications for highly efficient organic light-emitting devices. Combining a single-molecule experimental technique with an emitter that is sensitive to triplet dynamics, yet read out via fluorescence, should also provide a complementary approach to performing fundamental studies of glassy materials over a large dynamic range of time scales.
Bulletin of the American Physical Society, Mar 2, 2015
The migration of Frenkel excitons, tightly-bound electron-hole pairs, in polymeric organic semico... more The migration of Frenkel excitons, tightly-bound electron-hole pairs, in polymeric organic semiconducting films is critical to the efficiency of bulk heterojunction solar cells. While these materials exhibit a high degree of structural heterogeneity on the nanoscale, traditional measurements of exciton diffusion lengths are performed on bulk samples. Since both the characteristic length scales of structural heterogeneity and the reported bulk diffusion lengths are smaller than the optical diffraction limit, we adapt far-field super-resolution fluorescence imaging to uncover the correlations between the structural and energetic landscapes that the excitons explore.
In solid state semiconducting molecular materials used in electro-optical applications, relativel... more In solid state semiconducting molecular materials used in electro-optical applications, relatively long exciton diffusion lengths hold the promise to boost device performance by relaxing proximity constraints on the locations for light absorption and interfacial charge separation. The architecture of such materials determines their optical and electronic properties as a result of spacing-and orientation-dependent Coulomb couplings between adjacent molecules. Exciton character and dynamics are generally inferred from bulk optical measurements, which can present a severe limitation on our understanding of these films because their constituent molecules are not perfectly ordered. Rather, films of small organic molecules are composed of multiple microcrystalline domains, and this deposition-dependent microstructure can have profound impacts on transport properties. Using ultrafast transient absorption microscopy, we track the time evolution of excitons, domain by domain, in solid state thin films of TIPS-pentacene, a small soluble molecule that has recently been used in organic semiconducting devices because of its high hole mobility. The results from this spatially-resolved nonlinear optical spectroscopy support our hypothesis that bulk optical measurements deleteriously average over heterogeneities in both spatial and electronic structure; we have revealed significant inhomogeneity in exciton dynamics. Domains that appear homogeneous in linear optical microscopy are shown to have spatial variation and defects, and notable differences in exciton character and behavior are observed at domain boundaries. To interpret the contrast we observe with ultrafast dynamics, we correlate our data to local linear absorption, polarization analysis, profilometry, and atomic force microscopy. With this combined approach, we aim to ultimately understand fundamental structure-function relationship in molecular materials to provide predictive power to material development and device efficiency.
Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials f... more Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials for photovoltaic applications, have been made into atomically thin two-dimensional (2D) sheets. We report the solution-phase growth of single- and few-unit-cell-thick single-crystalline 2D hybrid perovskites of (C4H9NH3)2PbBr4 with well-defined square shape and large size. In contrast to other 2D materials, the hybrid perovskite sheets exhibit an unusual structural relaxation, and this structural change leads to a band gap shift as compared to the bulk crystal. The high-quality 2D crystals exhibit efficient photoluminescence, and color tuning could be achieved by changing sheet thickness as well as composition via the synthesis of related materials.
We present experimental and theoretical methods for and results of manipulating Bose-Einstein con... more We present experimental and theoretical methods for and results of manipulating Bose-Einstein condensates (BECs) with spatially compressed slow light pulses. These involve investigations into both the superfluid and coherent natures of the condensates. A detailed description of the phenomenon of ultra-slow light (USL) is provided. This includes a semi-classical picture of the dynamics of a three-level A atomic system coupled
By spatially resolving the polarized ultrafast optical transient absorption within several tens o... more By spatially resolving the polarized ultrafast optical transient absorption within several tens of individual domains in solution-processed polycrystalline smallmolecule organic semiconducting films, we infer the domains' extents of structural and orientational heterogeneity. As metrics, we observe variations in the time scales of ultrafast excited state dynamics and in the relative strength of competing resonant probe transitions. We find that films of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) exhibit a much higher degree of both structural and orientational heterogeneity among their domains than do films of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn), despite the apparent structural similarity between these two small molecules. Since both molecules feature prominently in solution-processed organic transistors, correlating the extent of heterogeneity to bulk transport using our approach will be highly valuable toward determining the underlying design principles for creating high-performing devices. Furthermore, our ability to characterize such variation in heterogeneity will enable fundamental studies of the interplay between molecular dynamics and driving forces in controlling emergent unequilibrated structures.
The journal of physical chemistry letters, Jan 16, 2015
We demonstrate that subdiffraction resolution can be achieved in fluorescence imaging of function... more We demonstrate that subdiffraction resolution can be achieved in fluorescence imaging of functional materials with densely packed, endogenous, electronically coupled chromophores by modifying stimulated emission depletion (STED) microscopy. This class of chromophores is not generally compatible with STED imaging due to strong two-photon absorption cross sections. Yet, we achieve 90 nm resolution and high contrast in images of clusters of conjugated polymer polyphenylenevinylene-derivative nanoparticles by modulating the excitation intensity in the material. This newfound capability has the potential to significantly broaden the range of fluorophores that can be employed in super-resolution fluorescence imaging. Moreover, solution-processed optoelectronics and photosynthetic or other naturally luminescent biomaterials exhibit complex energy and charge transport characteristics and luminescence variations in response to nanoscale heterogeneity in their complex, physical structures. Ou...
We reveal substantial luminescence yield heterogeneity among individual subdiffraction grains of ... more We reveal substantial luminescence yield heterogeneity among individual subdiffraction grains of high-performing methylammonium lead halide perovskite films by using high-resolution cathodoluminescence microscopy. Using considerably lower accelerating voltages than is conventional in scanning electron microscopy, we image the electron beam-induced luminescence of the films and statistically characterize the depth-dependent role of defects that promote nonradiative recombination losses. The highest variability in the luminescence intensity is observed at the exposed grain surfaces, which we attribute to surface defects. By probing deeper into the film, it appears that bulk defects are more homogeneously distributed. By identifying the origin and variability of a surface-specific loss mechanism that deleteriously impacts device efficiency, we suggest that producing films homogeneously composed of the highest-luminescence grains found in this study could result in a dramatic improvemen...
Manipulating the photophysical properties of light-absorbing units is a crucial element in the de... more Manipulating the photophysical properties of light-absorbing units is a crucial element in the design of biomimetic light-harvesting systems. Using a highly tunable synthetic platform combined with transient absorption and time-resolved fluorescence measurements and molecular dynamics simulations, we interrogate isolated chromophores covalently linked to different positions in the interior of the hydrated nanoscale cavity of a supramolecular protein assembly. We find that, following photoexcitation, the time scales over which these chromophores are solvated, undergo conformational rearrangements, and return to the ground state are highly sensitive to their position within this cavity and are significantly slower than in a bulk aqueous solution. Molecular dynamics simulations reveal the hindered translations and rotations of water molecules within the protein cavity with spatial specificity. The results presented herein show that fully hydrated nanoscale protein cavities are a promis...
We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy ... more We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy electron beam in an ultrathin scintillator are used as a noninvasive, near-field optical scanning probe of an underlying sample. We obtain optical images of Al nanostructures with 46 nm resolution and validate the noninvasiveness of this approach by imaging a conjugated polymer film otherwise incompatible with electron microscopy due to electron-induced damage. The high resolution, speed, and noninvasiveness of this "cathodoluminescence-activated" platform also show promise for super-resolution bioimaging.
The Electron Microscopy DataBank (EMDB) is growing rapidly, accumulating biological structural da... more The Electron Microscopy DataBank (EMDB) is growing rapidly, accumulating biological structural data obtained cryo-electron microscopy (cryo-EM). Cryo-EM is an emerging technique for determining large biomolecular complexes and subcellular structures. Together with the Protein Data Bank (PDB), EMDB is becoming a fundamental resource of the tertiary structures of biological macromolecules. To take full advantage of this indispensable resource, the ability to search the database by structural similarity is essential. However, unlike high-resolution structures stored in PDB, methods for comparing lowresolution EM density maps are not well established. Here, we developed a novel computational method for efficiently searching EM maps. The method uses a compact fingerprint representation of EM maps based on the 3D Zernike descriptor, which is a mathematical series expansion for representing isosurface shape of EM maps. The method was implemented in a web server, named EM-SURFER (http://kiharalab.org/em-surfer/), which allows users to search against the entire EMDB with over 2400 entries in a few seconds. By combing with map segmentation, the method can also identify corresponding local regions in EM maps. Examples of search results from different types of query structures are discussed. The unique capability of EM-SURFER to detect 3D shape similarity of low-resolution EM maps should prove invaluable in structural biology.
Single molecule (SM) fluorescence microscopy provides non-invasive means to localize biomolecules... more Single molecule (SM) fluorescence microscopy provides non-invasive means to localize biomolecules and characterize their diffusion in cells with a subresolution precision. Extending SM imaging techniques to live animals is an exciting, yet challenging endeavor that can potentially reveal how pathological processes affect the nanoscale mobility and the function of biomolecules in their native three-dimensional tissue environment. Here we used Complementation Activated Light Microscopy (CALM) to target, image and track individual voltage-dependent Ca2þ channels (VDCC) with a precision of 30 nm on muscle cells and within neuromuscular synapses of normal and dystrophin-mutant Caenorhabditis elegans worm models of Duchenne muscular dystrophy. Through diffusion and spatial pattern analyses, we show that dystrophin is a load-bearing apparatus and a tension transducer that modulates the confinement of VDCC within sarcolemmal membrane nanodomains in response to varying muscle tonus. SM imaging by CALM opens new avenues to explore the basic principles of homeostatic controls and the molecular basis of diseases at the nanometer scale in intact living animals.
Two-dimensional femtosecond broadband electronic spectroscopy was used to simultaneously probe pa... more Two-dimensional femtosecond broadband electronic spectroscopy was used to simultaneously probe parallel pathways of energy transfer in the major light harvesting complex of Photosystem II from plants. Sub-100 femtosecond relaxation between delocalized excitonic states on highly coupled clusters of chlorophylls and several hundred femtosecond to picosecond components of relaxation between clusters were observed.
Frontiers in Optics 2009/Laser Science XXV/Fall 2009 OSA Optics & Photonics Technical Digest, 2009
Two-dimensional electronic spectroscopy experiments on the major light harvesting complex of phot... more Two-dimensional electronic spectroscopy experiments on the major light harvesting complex of photosystem II, the most abundant light harvester, monitor ultrafast dynamics and reveal the design principles behind the functionality of this pigment protein complex.
order provide an opportunity to understand many fundamental physical properties relevant to solar... more order provide an opportunity to understand many fundamental physical properties relevant to solar energy conversion. Additionally, organic crystals are promising in their own right due to the effi cient carrier and energy transport properties associated with their long-range order. In particular, crystalline and polycrystalline fi lms of pentacene (PEN) and its derivatives have high carrier mobility for charge transport (≈1−10 cm 2 /Vs hole mobility) [ 1 ] and signifi cant photoconductivity. [ 2,3 ] Moreover, PEN and many of its derivatives display a propensity for singlet fi ssion (SF), [ 4,5 ] a phenomenon that results in greater than 100% internal quantum effi ciency in organic photovoltaics. Numerous possible molecular functionalizations may modify solid-state structural and optoelectronic properties. [ 6 ] Therefore, elucidating the structure-property relation is important for the design of new functional molecular materials. 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN), [ 7 ] shown in Figure 1 , has recently attracted much interest. The bulky groups functionalizing PEN enable solubility in organic solvents and allow for solution-processing of polycrystalline TIPS-PEN thin fi lms with high carrier mobility and photoconductivity. [ 2,3,7 ] While TIPS-PEN apparently retains optical properties similar to PEN, its enhanced carrier mobility [ 8 ] and
International Conference on Ultrafast Phenomena, 2010
Polarized, broadband two-dimensional electronic spectroscopy is performed on light harvesting com... more Polarized, broadband two-dimensional electronic spectroscopy is performed on light harvesting complex II. The results both reveal spectral features which can experimentally test site energies for the first time and also isolate quantum coherence signals.
... Naomi S.Ginsberg, Sean R.Garner, Christopher Slowe, Zachary Dutton*, and Lene Vestergaard Hau... more ... Naomi S.Ginsberg, Sean R.Garner, Christopher Slowe, Zachary Dutton*, and Lene Vestergaard Hau Cruft Laboratory, Harvard ... The ability to create, observe, and manipulate these micrometer-sized structures inside a BEC demonstrates the current ... 5. Transforming light in BECs ...
Recently developed all-organic emitters used in display applications achieve high brightness by h... more Recently developed all-organic emitters used in display applications achieve high brightness by harvesting triplet populations via thermally activated delayed fluorescence. The photophysical properties of these emitters therefore involve new inherent complexities and are strongly affected by interactions with their host material in the solid state. Ensemble measurements occlude the molecular details of how host−guest interactions determine fundamental properties such as the essential balance of singlet oscillator strength and triplet harvesting. Therefore, using time-resolved fluorescence spectroscopy, we interrogate these emitters at the single-molecule level and compare their properties in two distinct glassy polymer hosts. We find that nonbonding interactions with aromatic moieties in the host appear to mediate the molecular configurations of the emitters, but also promote nonradiative quenching pathways. We also find substantial heterogeneity in the time-resolved photoluminescence of these emitters, which is dominated by static disorder in the polymer. Finally, since singlet−triplet cycling underpins the mechanism for increased brightness, we present the first room-temperature measurement of singlet−triplet equilibration dynamics in this family of emitters. Our observations present a molecular-scale interrogation of host−guest interactions in a disordered film, with implications for highly efficient organic light-emitting devices. Combining a single-molecule experimental technique with an emitter that is sensitive to triplet dynamics, yet read out via fluorescence, should also provide a complementary approach to performing fundamental studies of glassy materials over a large dynamic range of time scales.
Bulletin of the American Physical Society, Mar 2, 2015
The migration of Frenkel excitons, tightly-bound electron-hole pairs, in polymeric organic semico... more The migration of Frenkel excitons, tightly-bound electron-hole pairs, in polymeric organic semiconducting films is critical to the efficiency of bulk heterojunction solar cells. While these materials exhibit a high degree of structural heterogeneity on the nanoscale, traditional measurements of exciton diffusion lengths are performed on bulk samples. Since both the characteristic length scales of structural heterogeneity and the reported bulk diffusion lengths are smaller than the optical diffraction limit, we adapt far-field super-resolution fluorescence imaging to uncover the correlations between the structural and energetic landscapes that the excitons explore.
In solid state semiconducting molecular materials used in electro-optical applications, relativel... more In solid state semiconducting molecular materials used in electro-optical applications, relatively long exciton diffusion lengths hold the promise to boost device performance by relaxing proximity constraints on the locations for light absorption and interfacial charge separation. The architecture of such materials determines their optical and electronic properties as a result of spacing-and orientation-dependent Coulomb couplings between adjacent molecules. Exciton character and dynamics are generally inferred from bulk optical measurements, which can present a severe limitation on our understanding of these films because their constituent molecules are not perfectly ordered. Rather, films of small organic molecules are composed of multiple microcrystalline domains, and this deposition-dependent microstructure can have profound impacts on transport properties. Using ultrafast transient absorption microscopy, we track the time evolution of excitons, domain by domain, in solid state thin films of TIPS-pentacene, a small soluble molecule that has recently been used in organic semiconducting devices because of its high hole mobility. The results from this spatially-resolved nonlinear optical spectroscopy support our hypothesis that bulk optical measurements deleteriously average over heterogeneities in both spatial and electronic structure; we have revealed significant inhomogeneity in exciton dynamics. Domains that appear homogeneous in linear optical microscopy are shown to have spatial variation and defects, and notable differences in exciton character and behavior are observed at domain boundaries. To interpret the contrast we observe with ultrafast dynamics, we correlate our data to local linear absorption, polarization analysis, profilometry, and atomic force microscopy. With this combined approach, we aim to ultimately understand fundamental structure-function relationship in molecular materials to provide predictive power to material development and device efficiency.
Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials f... more Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials for photovoltaic applications, have been made into atomically thin two-dimensional (2D) sheets. We report the solution-phase growth of single- and few-unit-cell-thick single-crystalline 2D hybrid perovskites of (C4H9NH3)2PbBr4 with well-defined square shape and large size. In contrast to other 2D materials, the hybrid perovskite sheets exhibit an unusual structural relaxation, and this structural change leads to a band gap shift as compared to the bulk crystal. The high-quality 2D crystals exhibit efficient photoluminescence, and color tuning could be achieved by changing sheet thickness as well as composition via the synthesis of related materials.
We present experimental and theoretical methods for and results of manipulating Bose-Einstein con... more We present experimental and theoretical methods for and results of manipulating Bose-Einstein condensates (BECs) with spatially compressed slow light pulses. These involve investigations into both the superfluid and coherent natures of the condensates. A detailed description of the phenomenon of ultra-slow light (USL) is provided. This includes a semi-classical picture of the dynamics of a three-level A atomic system coupled
By spatially resolving the polarized ultrafast optical transient absorption within several tens o... more By spatially resolving the polarized ultrafast optical transient absorption within several tens of individual domains in solution-processed polycrystalline smallmolecule organic semiconducting films, we infer the domains' extents of structural and orientational heterogeneity. As metrics, we observe variations in the time scales of ultrafast excited state dynamics and in the relative strength of competing resonant probe transitions. We find that films of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) exhibit a much higher degree of both structural and orientational heterogeneity among their domains than do films of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn), despite the apparent structural similarity between these two small molecules. Since both molecules feature prominently in solution-processed organic transistors, correlating the extent of heterogeneity to bulk transport using our approach will be highly valuable toward determining the underlying design principles for creating high-performing devices. Furthermore, our ability to characterize such variation in heterogeneity will enable fundamental studies of the interplay between molecular dynamics and driving forces in controlling emergent unequilibrated structures.
The journal of physical chemistry letters, Jan 16, 2015
We demonstrate that subdiffraction resolution can be achieved in fluorescence imaging of function... more We demonstrate that subdiffraction resolution can be achieved in fluorescence imaging of functional materials with densely packed, endogenous, electronically coupled chromophores by modifying stimulated emission depletion (STED) microscopy. This class of chromophores is not generally compatible with STED imaging due to strong two-photon absorption cross sections. Yet, we achieve 90 nm resolution and high contrast in images of clusters of conjugated polymer polyphenylenevinylene-derivative nanoparticles by modulating the excitation intensity in the material. This newfound capability has the potential to significantly broaden the range of fluorophores that can be employed in super-resolution fluorescence imaging. Moreover, solution-processed optoelectronics and photosynthetic or other naturally luminescent biomaterials exhibit complex energy and charge transport characteristics and luminescence variations in response to nanoscale heterogeneity in their complex, physical structures. Ou...
We reveal substantial luminescence yield heterogeneity among individual subdiffraction grains of ... more We reveal substantial luminescence yield heterogeneity among individual subdiffraction grains of high-performing methylammonium lead halide perovskite films by using high-resolution cathodoluminescence microscopy. Using considerably lower accelerating voltages than is conventional in scanning electron microscopy, we image the electron beam-induced luminescence of the films and statistically characterize the depth-dependent role of defects that promote nonradiative recombination losses. The highest variability in the luminescence intensity is observed at the exposed grain surfaces, which we attribute to surface defects. By probing deeper into the film, it appears that bulk defects are more homogeneously distributed. By identifying the origin and variability of a surface-specific loss mechanism that deleteriously impacts device efficiency, we suggest that producing films homogeneously composed of the highest-luminescence grains found in this study could result in a dramatic improvemen...
Manipulating the photophysical properties of light-absorbing units is a crucial element in the de... more Manipulating the photophysical properties of light-absorbing units is a crucial element in the design of biomimetic light-harvesting systems. Using a highly tunable synthetic platform combined with transient absorption and time-resolved fluorescence measurements and molecular dynamics simulations, we interrogate isolated chromophores covalently linked to different positions in the interior of the hydrated nanoscale cavity of a supramolecular protein assembly. We find that, following photoexcitation, the time scales over which these chromophores are solvated, undergo conformational rearrangements, and return to the ground state are highly sensitive to their position within this cavity and are significantly slower than in a bulk aqueous solution. Molecular dynamics simulations reveal the hindered translations and rotations of water molecules within the protein cavity with spatial specificity. The results presented herein show that fully hydrated nanoscale protein cavities are a promis...
We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy ... more We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy electron beam in an ultrathin scintillator are used as a noninvasive, near-field optical scanning probe of an underlying sample. We obtain optical images of Al nanostructures with 46 nm resolution and validate the noninvasiveness of this approach by imaging a conjugated polymer film otherwise incompatible with electron microscopy due to electron-induced damage. The high resolution, speed, and noninvasiveness of this "cathodoluminescence-activated" platform also show promise for super-resolution bioimaging.
The Electron Microscopy DataBank (EMDB) is growing rapidly, accumulating biological structural da... more The Electron Microscopy DataBank (EMDB) is growing rapidly, accumulating biological structural data obtained cryo-electron microscopy (cryo-EM). Cryo-EM is an emerging technique for determining large biomolecular complexes and subcellular structures. Together with the Protein Data Bank (PDB), EMDB is becoming a fundamental resource of the tertiary structures of biological macromolecules. To take full advantage of this indispensable resource, the ability to search the database by structural similarity is essential. However, unlike high-resolution structures stored in PDB, methods for comparing lowresolution EM density maps are not well established. Here, we developed a novel computational method for efficiently searching EM maps. The method uses a compact fingerprint representation of EM maps based on the 3D Zernike descriptor, which is a mathematical series expansion for representing isosurface shape of EM maps. The method was implemented in a web server, named EM-SURFER (http://kiharalab.org/em-surfer/), which allows users to search against the entire EMDB with over 2400 entries in a few seconds. By combing with map segmentation, the method can also identify corresponding local regions in EM maps. Examples of search results from different types of query structures are discussed. The unique capability of EM-SURFER to detect 3D shape similarity of low-resolution EM maps should prove invaluable in structural biology.
Single molecule (SM) fluorescence microscopy provides non-invasive means to localize biomolecules... more Single molecule (SM) fluorescence microscopy provides non-invasive means to localize biomolecules and characterize their diffusion in cells with a subresolution precision. Extending SM imaging techniques to live animals is an exciting, yet challenging endeavor that can potentially reveal how pathological processes affect the nanoscale mobility and the function of biomolecules in their native three-dimensional tissue environment. Here we used Complementation Activated Light Microscopy (CALM) to target, image and track individual voltage-dependent Ca2þ channels (VDCC) with a precision of 30 nm on muscle cells and within neuromuscular synapses of normal and dystrophin-mutant Caenorhabditis elegans worm models of Duchenne muscular dystrophy. Through diffusion and spatial pattern analyses, we show that dystrophin is a load-bearing apparatus and a tension transducer that modulates the confinement of VDCC within sarcolemmal membrane nanodomains in response to varying muscle tonus. SM imaging by CALM opens new avenues to explore the basic principles of homeostatic controls and the molecular basis of diseases at the nanometer scale in intact living animals.
Two-dimensional femtosecond broadband electronic spectroscopy was used to simultaneously probe pa... more Two-dimensional femtosecond broadband electronic spectroscopy was used to simultaneously probe parallel pathways of energy transfer in the major light harvesting complex of Photosystem II from plants. Sub-100 femtosecond relaxation between delocalized excitonic states on highly coupled clusters of chlorophylls and several hundred femtosecond to picosecond components of relaxation between clusters were observed.
Frontiers in Optics 2009/Laser Science XXV/Fall 2009 OSA Optics & Photonics Technical Digest, 2009
Two-dimensional electronic spectroscopy experiments on the major light harvesting complex of phot... more Two-dimensional electronic spectroscopy experiments on the major light harvesting complex of photosystem II, the most abundant light harvester, monitor ultrafast dynamics and reveal the design principles behind the functionality of this pigment protein complex.
order provide an opportunity to understand many fundamental physical properties relevant to solar... more order provide an opportunity to understand many fundamental physical properties relevant to solar energy conversion. Additionally, organic crystals are promising in their own right due to the effi cient carrier and energy transport properties associated with their long-range order. In particular, crystalline and polycrystalline fi lms of pentacene (PEN) and its derivatives have high carrier mobility for charge transport (≈1−10 cm 2 /Vs hole mobility) [ 1 ] and signifi cant photoconductivity. [ 2,3 ] Moreover, PEN and many of its derivatives display a propensity for singlet fi ssion (SF), [ 4,5 ] a phenomenon that results in greater than 100% internal quantum effi ciency in organic photovoltaics. Numerous possible molecular functionalizations may modify solid-state structural and optoelectronic properties. [ 6 ] Therefore, elucidating the structure-property relation is important for the design of new functional molecular materials. 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN), [ 7 ] shown in Figure 1 , has recently attracted much interest. The bulky groups functionalizing PEN enable solubility in organic solvents and allow for solution-processing of polycrystalline TIPS-PEN thin fi lms with high carrier mobility and photoconductivity. [ 2,3,7 ] While TIPS-PEN apparently retains optical properties similar to PEN, its enhanced carrier mobility [ 8 ] and
International Conference on Ultrafast Phenomena, 2010
Polarized, broadband two-dimensional electronic spectroscopy is performed on light harvesting com... more Polarized, broadband two-dimensional electronic spectroscopy is performed on light harvesting complex II. The results both reveal spectral features which can experimentally test site energies for the first time and also isolate quantum coherence signals.
... Naomi S.Ginsberg, Sean R.Garner, Christopher Slowe, Zachary Dutton*, and Lene Vestergaard Hau... more ... Naomi S.Ginsberg, Sean R.Garner, Christopher Slowe, Zachary Dutton*, and Lene Vestergaard Hau Cruft Laboratory, Harvard ... The ability to create, observe, and manipulate these micrometer-sized structures inside a BEC demonstrates the current ... 5. Transforming light in BECs ...
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Papers by Naomi Ginsberg