scholarly journals Excitation energy migration processes in various multi-porphyrin assemblies

2012 ◽  
Vol 370 (1972) ◽  
pp. 3802-3818 ◽  
Author(s):  
Jaesung Yang ◽  
Dongho Kim
Keyword(s):  
Excitation Energy ◽  
Single Molecule ◽  
Coherence Length ◽  
Radiative Decay ◽  
Transient Absorption ◽  
Excitation Energy Transfer ◽  
Building Blocks ◽  
Linear Arrays ◽  
Single Molecule Level ◽  
Structural Distortions

The electronic interactions and excitation energy transfer (EET) processes of a variety of multi-porphyrin arrays with linear, cyclic and box architectures have been explored. Directly meso – meso linked linear arrays ( Z N ) exhibit strong excitonic coupling with an exciton coherence length of approximately 6 porphyrin units, while fused linear arrays ( T N ) exhibit extensive π -conjugation over the whole array. The excitonic coherence length in directly linked cyclic porphyrin rings ( CZ N ) was determined to be approximately 2.7 porphyrin units by simultaneous analysis of fluorescence intensities and lifetimes at the single-molecule level. By performing transient absorption (TA) and TA anisotropy decay measurements, the EET rates in m -phenylene linked cyclic porphyrin wheels C12ZA and C24ZB were determined to be 4 and 36 ps −1 , respectively. With increasing the size of C N ZA , the EET efficiencies decrease owing to the structural distortions that produce considerable non-radiative decay pathways. Finally, the EET rates of self-assembled porphyrin boxes consisting of directly linked diporphyrins, B1A , B2A and B3A , are 48, 98 and 361 ps −1 , respectively. The EET rates of porphyrin boxes consisting of alkynylene-bridged diporphyrins, B2B and B4B , depend on the conformation of building blocks (planar or orthogonal) rather than the length of alkynylene linkers.

Single-molecule spectroscopy and femtosecond transient absorption studies on the excitation energy transfer process in ApcE(1–240) dimers

2015 ◽  
Vol 17 (20) ◽  
pp. 13387-13396 ◽  
Author(s):  
Saran Long ◽  
Meng Zhou ◽  
Kun Tang ◽  
Xiao-Li Zeng ◽  
Yingli Niu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Single Molecule ◽  
Transfer Process ◽  
Transient Absorption ◽  
Energy Transfer Process ◽  
Excitation Energy Transfer ◽  
Single Molecule Spectroscopy ◽  
Femtosecond Transient Absorption ◽  
Absorption Studies

The red-shifted absorption of ApcE dimers results from extending chromophore conformation, which does not depend on strong exction coupling.

scholarly journals Microsecond and millisecond dynamics in the photosynthetic protein LHCSR1 observed by single-molecule correlation spectroscopy

2019 ◽  
Vol 116 (23) ◽  
pp. 11247-11252 ◽  
Author(s):  
Toru Kondo ◽  
Jesse B. Gordon ◽  
Alberta Pinnola ◽  
Luca Dall’Osto ◽  
Roberto Bassi ◽  
...  
Keyword(s):  
Correlation Function ◽  
Single Molecule ◽  
Conformational Changes ◽  
Protein Function ◽  
Light Harvesting ◽  
Building Blocks ◽  
Complex Stress ◽  
Correlation Spectroscopy ◽  
Light Harvesting Complex ◽  
Single Molecule Level

Biological systems are subjected to continuous environmental fluctuations, and therefore, flexibility in the structure and function of their protein building blocks is essential for survival. Protein dynamics are often local conformational changes, which allows multiple dynamical processes to occur simultaneously and rapidly in individual proteins. Experiments often average over these dynamics and their multiplicity, preventing identification of the molecular origin and impact on biological function. Green plants survive under high light by quenching excess energy, and Light-Harvesting Complex Stress Related 1 (LHCSR1) is the protein responsible for quenching in moss. Here, we expand an analysis of the correlation function of the fluorescence lifetime by improving the estimation of the lifetime states and by developing a multicomponent model correlation function, and we apply this analysis at the single-molecule level. Through these advances, we resolve previously hidden rapid dynamics, including multiple parallel processes. By applying this technique to LHCSR1, we identify and quantitate parallel dynamics on hundreds of microseconds and tens of milliseconds timescales, likely at two quenching sites within the protein. These sites are individually controlled in response to fluctuations in sunlight, which provides robust regulation of the light-harvesting machinery. Considering our results in combination with previous structural, spectroscopic, and computational data, we propose specific pigments that serve as the quenching sites. These findings, therefore, provide a mechanistic basis for quenching, illustrating the ability of this method to uncover protein function.

scholarly journals Control over size, shape, and photonics of self-assembled organic nanocrystals

2020 ◽  
Author(s):  
Chen Shahar ◽  
Yaron Tidhar ◽  
Yunmin Jung ◽  
Haim Weissman ◽  
Sidney R Cohen ◽  
...  
Keyword(s):  
Self Assembly ◽  
Transient Absorption ◽  
Aqueous Media ◽  
Excitation Energy Transfer ◽  
Building Blocks ◽  
Transient Absorption Spectroscopy ◽  
Organic Nanocrystals ◽  
Femtosecond Transient Absorption ◽  
Transmission Electron ◽  
And Function

Facile fabrication of free-floating organic nanocrystals (ONCs) was achieved via kinetically controlled self-assembly of simple amphiphilic perylene diimide building blocks in aqueous media. The ONCs have a thin rectangular shape, with the aspect ratio that is controlled via organic co-solvent (THF) content. The nanocrystals were characterized in solution by cryogenic transmission electron microscopy (cryo-TEM) and small angle X-ray scattering (SAXS); the ONCs retain their structure upon drying as was evidenced by TEM and AFM. Photophysical studies, including femtosecond transient absorption spectroscopy, revealed a distinct influence of the ONC morphology on their photonic properties (excitation energy transfer was observed only in the high aspect ONCs). Convenient control over structure and function of organic nanocrystals can enhance their utility in new and developed technologies.

Plasmonic gas and chemical sensing

Nanophotonics ◽  
2014 ◽  
Vol 3 (3) ◽  
pp. 157-180 ◽  
Author(s):  
Andreas Tittl ◽  
Harald Giessen ◽  
Na Liu
Keyword(s):  
Single Molecule ◽  
Local Environment ◽  
Building Blocks ◽  
Industrial Applications ◽  
Noble Metal Nanoparticles ◽  
Sensor Technology ◽  
Plasmonic Nanostructures ◽  
Robust Detection ◽  
Single Molecule Level ◽  
Plasmonic Particles

AbstractSensitive and robust detection of gases and chemical reactions constitutes a cornerstone of scientific research and key industrial applications. In an effort to reach progressively smaller reagent concentrations and sensing volumes, optical sensor technology has experienced a paradigm shift from extended thin-film systems towards engineered nanoscale devices. In this size regime, plasmonic particles and nanostructures provide an ideal toolkit for the realization of novel sensing concepts. This is due to their unique ability to simultaneously focus light into subwavelength hotspots of the electromagnetic field and to transmit minute changes of the local environment back into the farfield as a modulation of their optical response. Since the basic building blocks of a plasmonic system are commonly noble metal nanoparticles or nanostructures, plasmonics can easily be integrated with a plethora of chemically or catalytically active materials and compounds to investigate processes ranging from hydrogen absorption in palladium to the detection of trinitrotoluene (TNT). In this review, we will discuss a multitude of plasmonic sensing strategies, spanning the technological scale from simple plasmonic particles embedded in extended thin films to highly engineered complex plasmonic nanostructures. Due to their flexibility and excellent sensing performance, plasmonic structures may open an exciting pathway towards the detection of chemical and catalytic events down to the single molecule level.

Determination of the Superradiance Coherence Length of Directly Linked Linear Porphyrin Arrays at the Single-Molecule Level

2009 ◽  
Vol 121 (24) ◽  
pp. 4387-4391 ◽  
Author(s):  
Jaesung Yang ◽  
Hyejin Yoo ◽  
Naoki Aratani ◽  
Atsuhiro Osuka ◽  
Dongho Kim
Keyword(s):  
Single Molecule ◽  
Coherence Length ◽  
Single Molecule Level

scholarly journals Beads on a Chain (BoC) Fluorescent Oligomeric Materials: Interactions of Conjugated Organic Cross-Linkers with Silsesquioxane Cages

2021 ◽  
Author(s):  
Shahrea Mahbub ◽  
Sukanya Saha ◽  
Ramakrishna Guda ◽  
Joseph Furgal
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Electronic Materials ◽  
Field Effect Transistors ◽  
Single Photon ◽  
Photophysical Properties ◽  
Excitation Energy Transfer ◽  
Transient Absorption Spectroscopy ◽  
Gravimetric Analysis

<div> <div> <div> <p>Organic electronic materials have advantages over inorganics in terms of versatility, cost and processability. Recent advancements in organic materials for light emitting diodes (OLED), field effect transistors (OFET), and photovoltaics have engendered extensive innovation potential on this field. In this research, we focus on synthesizing SQ (silsesquioxane) based oligomers cross- linked by di-bromo-aromatic linkers and explore how the cross-linker and oligomer length influence their photophysical properties. Bis-tri-alkoxy silyl (linker) model compounds were synthesized to compare non-cage photophysical properties with the oligomers. Several techniques such as UV/Vis, fluorescence, FTIR, thermal gravimetric analysis (TGA) have been used to characterize the systems. Time-resolved fluorescence and femtosecond transient absorption spectroscopy are used to understand the excited state dynamics of these materials. Studies are carried out to understand the differences between monomers and oligomers and potential energy transfer and charge transfer between the cages and cross-linking chromophores. Transient absorption showed lower energy absorption from the excited states, suggesting short range communication between moieties. Single photon counting studies have shown distinct lifetime differences between most linkers and cages showing possible excitation energy transfer through these materials. Transient absorption anisotropy measurements have shown signatures for excitation energy transfer between linker chromophores for oligomeric compounds. The silsesquioxane (SQ) backbone of the oligomers gives substantial thermal stability as well as solution processability, giving better flexibility for achieving energy transfer between linking chromophores. </p> </div> </div> </div>

scholarly journals Chlorophyll–carotenoid excitation energy transfer and charge transfer in Nannochloropsis oceanica for the regulation of photosynthesis

2019 ◽  
Vol 116 (9) ◽  
pp. 3385-3390 ◽  
Author(s):  
Soomin Park ◽  
Collin J. Steen ◽  
Dagmar Lyska ◽  
Alexandra L. Fischer ◽  
Benjamin Endelman ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Excitation Energy Transfer ◽  
Excited State Absorption ◽  
Thermal Dissipation ◽  
Live Cells ◽  
Nannochloropsis Oceanica

Nonphotochemical quenching (NPQ) is a proxy for photoprotective thermal dissipation processes that regulate photosynthetic light harvesting. The identification of NPQ mechanisms and their molecular or physiological triggering factors under in vivo conditions is a matter of controversy. Here, to investigate chlorophyll (Chl)–zeaxanthin (Zea) excitation energy transfer (EET) and charge transfer (CT) as possible NPQ mechanisms, we performed transient absorption (TA) spectroscopy on live cells of the microalga Nannochloropsis oceanica. We obtained evidence for the operation of both EET and CT quenching by observing spectral features associated with the Zea S1 and Zea●+ excited-state absorption (ESA) signals, respectively, after Chl excitation. Knockout mutants for genes encoding either violaxanthin de-epoxidase or LHCX1 proteins exhibited strongly inhibited NPQ capabilities and lacked detectable Zea S1 and Zea●+ ESA signals in vivo, which strongly suggests that the accumulation of Zea and active LHCX1 is essential for both EET and CT quenching in N. oceanica.

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