Temperature-Dependent Exciton Properties of Two Cylindrical J-Aggregates

2014 ◽  
Vol 118 (42) ◽  
pp. 24325-24334 ◽  
Author(s):  
Katie A. Clark ◽  
Emma L. Krueger ◽  
David A. Vanden Bout
Keyword(s):  
Temperature Dependent ◽  
J Aggregates

scholarly journals Quantum Beats in Transient Spectroscopy of J-Aggregates

1996 ◽  
Vol 16 (3) ◽  
pp. 179-196
Author(s):  
H. Glaeske ◽  
K.-H. Feller ◽  
E. Gaišaukas ◽  
L. Knöll
Keyword(s):  
Transient Absorption ◽  
Temporal Evolution ◽  
Quantum Beat ◽  
Quantum Beats ◽  
Level System ◽  
Temperature Dependent ◽  
Phase Relaxation ◽  
Experimental Conditions ◽  
J Aggregates ◽  
Transient Spectroscopy

Quantum beats in transient absorption of PIC-J-aggregates, modelled by a modified 3-level-system are calculated. Experimental conditions for the possibility of their observation are investigated. The influence of the temperature dependent phase relaxation on the temporal evolution of quantum beat signals is considered.

Temperature Dependent Radiative Lifetime of J-Aggregates

1996 ◽  
Vol 100 (21) ◽  
pp. 8640-8644 ◽  
Author(s):  
Valey F. Kamalov ◽  
Irina A. Struganova ◽  
Keitaro Yoshihara
Keyword(s):  
Radiative Lifetime ◽  
Temperature Dependent ◽  
J Aggregates

scholarly journals Bridging the Gap between H- and J-Aggregates: Classification and Supramolecular Tunability for Excitonic Band Structures in 2-Dimensional Molecular Aggregates

2021 ◽  
Author(s):  
Arundhati Deshmukh ◽  
Niklas Geue ◽  
Nadine Bardbury ◽  
Timothy Atallah ◽  
Chern Chuang ◽  
...  
Keyword(s):  
Photophysical Properties ◽  
Quantum Yields ◽  
Molecular Aggregates ◽  
Temperature Dependent ◽  
Excitonic Band ◽  
Spectral Shifts ◽  
Aggregate Properties ◽  
Higher Dimensional ◽  
J Aggregates ◽  
Shortwave Infrared

Molecular aggregates with long-range excitonic couplings have drastically different photophysical properties compared to their monomer counterparts. From Kasha’s model for 1-dimensional systems, positive or negative excitonic couplings lead to blue or red shifted optical spectra with respect to the monomers, labelled H-and J-aggregates respectively. The overall excitonic couplings in higher dimensional systems are much more complicated and cannot be simply classified from their spectral shifts alone. Here, we provide a unified classification for extended 2D aggregates using temperature dependent peak shifts, thermal broadening and quantum yields. We discuss the examples of six 2D aggregates with J-like absorption spectra but quite drastic changes quantum yields and superradiance. We find the origin of the differences is, in fact, a different excitonic band structure where the bright state is lower energy than the monomer but still away from the band edge. We call this an ‘I-aggregate’. Our results provide a description of the complex excitonic behaviors that cannot be explained solely on Kasha’s model. Further, such properties can be tuned with the packing geometries within the aggregates providing supramolecular pathways for controlling them. This will allow for precise optimizations of aggregate properties in their applications across the areas of optoelectronics, photonics, excitonic energy transfer, and shortwave infrared technologies.

scholarly journals Bridging the Gap between H- and J-Aggregates: Classification and Supramolecular Tunability for Excitonic Band Structures in 2-Dimensional Molecular Aggregates

2021 ◽  
Author(s):  
Arundhati Deshmukh ◽  
Niklas Geue ◽  
Nadine Bradbury ◽  
Timothy Atallah ◽  
Chern Chuang ◽  
...  
Keyword(s):  
Photophysical Properties ◽  
Quantum Yields ◽  
Molecular Aggregates ◽  
Temperature Dependent ◽  
Excitonic Band ◽  
Spectral Shifts ◽  
Aggregate Properties ◽  
Higher Dimensional ◽  
J Aggregates ◽  
Shortwave Infrared

Molecular aggregates with long-range excitonic couplings have drastically different photophysical properties compared to their monomer counterparts. From Kasha’s model for 1-dimensional systems, positive or negative excitonic couplings lead to blue or red shifted optical spectra with respect to the monomers, labelled H-and J-aggregates respectively. The overall excitonic couplings in higher dimensional systems are much more complicated and cannot be simply classified from their spectral shifts alone. Here, we provide a unified classification for extended 2D aggregates using temperature dependent peak shifts, thermal broadening and quantum yields. We discuss the examples of six 2D aggregates with J-like absorption spectra but quite drastic changes quantum yields and superradiance. We find the origin of the differences is, in fact, a different excitonic band structure where the bright state is lower energy than the monomer but still away from the band edge. We call this an ‘I-aggregate’. Our results provide a description of the complex excitonic behaviors that cannot be explained solely on Kasha’s model. Further, such properties can be tuned with the packing geometries within the aggregates providing supramolecular pathways for controlling them. This will allow for precise optimizations of aggregate properties in their applications across the areas of optoelectronics, photonics, excitonic energy transfer, and shortwave infrared technologies.

Temperature-Dependent Exciton Dynamics in J-Aggregates—When Disorder Plays a Role

2009 ◽  
Vol 113 (48) ◽  
pp. 15836-15842 ◽  
Author(s):  
Theo E. Kaiser ◽  
Ivan G. Scheblykin ◽  
Daniel Thomsson ◽  
Frank Würthner
Keyword(s):  
Temperature Dependent ◽  
Exciton Dynamics ◽  
J Aggregates

scholarly journals Designing Highly Luminescent Molecular Aggregates via Bottom-Up Nanoscale Engineering

2021 ◽  
Author(s):  
Ulugbek Barotov ◽  
Megan Klein ◽  
Lili Wang ◽  
Moungi Bawendi
Keyword(s):  
Quantum Yield ◽  
Long Range ◽  
High Speed ◽  
Cyanine Dye ◽  
High Quantum Yield ◽  
Temperature Dependent ◽  
Bottom Up ◽  
Organic Fluorophores ◽  
High Quantum ◽  
J Aggregates

Coupling of excitations between organic fluorophores in J-aggregates leads to coherent delocalization of excitons across multiple molecules, resulting in materials with high extinction coefficients, long-range exciton transport, and, in particular, short radiative lifetimes. Despite these favorable optical properties, uses of J-aggregates as high-speed light sources have been hindered by their low photoluminescence quantum yields. Here, we take a bottom-up approach to design a novel J-aggregate system with a large extinction coefficient, a high quantum yield and a short lifetime. To achieve this goal, we first select a J-aggregating cyanine chromophore and reduce its nonradiative pathways by rigidifying the backbone of the cyanine dye. The resulting conformationally-restrained cyanine dye exhibits strong absorbance at 530 nm and fluorescence at 550 nm with 90% quantum yield and 2.3 ns lifetime. We develop optimal conditions for the self-assembly of highly emissive J-aggregates. Cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) reveal micron-scale extended structures with 2D sheet-like morphology, indicating long-range structural order. These novel J-aggregates have a strong red-shifted absorption at 600 nm, resonant fluorescence with no Stokes shift, 50% quantum yield, and 220 ps lifetime at room temperature. We further stabilize these aggregates in a glassy sugar matrix and study their excitonic behavior using temperature-dependent absorption and fluorescence spectroscopy. These temperature- dependent studies confirm J-type excitonic coupling and superradiance. Our results have implications for the development of a new generation of organic fluorophores that combine high speed, high quantum yield and solution processing.

(111) Monocrystalline Nickel Films

1972 ◽  
Vol 30 ◽  
pp. 512-513
Author(s):  
T.E. Pratt ◽  
R.W. Vook
Keyword(s):  
Film Thickness ◽  
Deposition Rate ◽  
Room Temperature ◽  
Narrow Range ◽  
High Vacuum ◽  
Residual Pressure ◽  
Temperature Dependent ◽  
Deposition Parameters ◽  
Transmission Electron ◽  
Substrate Temperatures

(111) oriented thin monocrystalline Ni films have been prepared by vacuum evaporation and examined by transmission electron microscopy and electron diffraction. In high vacuum, at room temperature, a layer of NaCl was first evaporated onto a freshly air-cleaved muscovite substrate clamped to a copper block with attached heater and thermocouple. Then, at various substrate temperatures, with other parameters held within a narrow range, Ni was evaporated from a tungsten filament. It had been shown previously that similar procedures would yield monocrystalline films of CU, Ag, and Au.For the films examined with respect to temperature dependent effects, typical deposition parameters were: Ni film thickness, 500-800 A; Ni deposition rate, 10 A/sec.; residual pressure, 10-6 torr; NaCl film thickness, 250 A; and NaCl deposition rate, 10 A/sec. Some additional evaporations involved higher deposition rates and lower film thicknesses.Monocrystalline films were obtained with substrate temperatures above 500° C. Below 450° C, the films were polycrystalline with a strong (111) preferred orientation.

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