scholarly journals Time-Resolved Spectroscopy of Polymethine J-Aggregates

1991 ◽  
Vol 11 (1) ◽  
pp. 1-12 ◽  
Author(s):  
K.-H. Feller ◽  
R. Gadonas ◽  
V. Krasauskas ◽  
V. Fidler ◽  
S. Vajda
Keyword(s):  
Steady State ◽  
Transient Absorption ◽  
Decay Kinetics ◽  
Time Resolved ◽  
Absorption And Fluorescence Spectroscopy ◽  
Transient Absorption Spectra ◽  
J Aggregates ◽  
Exciton Annihilation ◽  
Deactivation Process ◽  
Aggregate Structures

The deactivation process of J-aggregates of DDEOCI (3,3'-diethyl-5,5'-diphenyl-9-ethyl-oxacarbocyanine iodide) was investigated by means of steady-state and time-resolved absorption and fluorescence spectroscopy. The decay kinetics as well as the transient absorption spectra have been analyzed including different aggregate structures and exciton-exciton annihilation.

scholarly journals Tracking Intrinsic Properties of CH3NH3PbI3 Perovskite Thin Films Grown by Spin Coating Technique at Ambient Temperature

2019 ◽  
Vol 6 (2) ◽  
pp. 59-68
Author(s):  
Cliff Orori Mosiori ◽  
John Maera
Keyword(s):  
Thin Films ◽  
Optical Constants ◽  
Transient Absorption ◽  
Large Fraction ◽  
Perovskite Solar Cells ◽  
Transient Absorption Spectrum ◽  
Decay Kinetics ◽  
Lead Iodide ◽  
Time Resolved ◽  
Optoelectronic Applications

Methyl ammonium lead iodide has become a burgeoning class of hybrid halide perovskites of solution-processed semiconductors. Advancements in its processing and characterization underscore structural, optical, and electronic properties. They have led to the development of perovskite solar cells, photo detectors, lasers, and photo diodes with power conversion efficiencies mature to be classified as first and second-generation technologies. Characterizing forms an integral understanding the operating principles and fundamental limitations for optoelectronics applications. Studies outlined in this paper covers CH3NH3PbI3 using time-resolved pump-probe spectroscopy, X-ray diffractometry, spectrophotometry and other measurements. Thus this investigatiosn may serve as principle tool in analyzing excited state decay kinetics and optical nonlinearities in CH3NH3PbI3 thin films. It is demonstrated herein that non-resonant photoexcitation yields a large fraction of free carriers on a sub-picosecond time scale. If applied in practical optoelectronic applications then any photogenerated carriers may travel long carrier lengths before they are extracted to realize large external quantum efficiencies and efficient charge extraction. The optical constants of CH3NH3PbI3 are interpreted using ab initio calculations through models. Findings show good agreement between the optical constants derived from QSGW and those from related literature. Transition from the highest valence band (VB) to the lowest conduction band (CB) was found to be responsible for almost all the optical responses between 1.2 and 5.5 eV. It was concluded that optical constants and energy band diagrams of CH3NH3PbI3 can be used to simulate the contributions from different optical transitions to a typical transient absorption spectrum for many optoelectronic applications.

Characterization of Plasma-Modified Fluoropolymer Surfaces Using Steady-State and Time-Resolved Fluorescence Spectroscopy

1994 ◽  
Vol 48 (5) ◽  
pp. 630-637 ◽  
Author(s):  
Ming Li ◽  
Michaeleen L. Pacholski ◽  
Frank V. Bright
Keyword(s):  
Steady State ◽  
Fluorescence Spectroscopy ◽  
Sulfonyl Chloride ◽  
Sodium Dodecylsulfate ◽  
Covalent Immobilization ◽  
Ambient Conditions ◽  
Time Resolved Fluorescence ◽  
Decay Kinetics ◽  
Time Resolved

Poly(hexafluoropropylene-co-tetrafluoroethylene) (FEP) has been widely used in biotechnology because of its unique surface properties and biocompatibility. Recent work from our group has shown that plasma discharge-modified FEP can be used as the substratum for development of a very stable immunosensor. This result has prompted us to study further this new surface under ambient conditions. In this paper, we report on the covalent immobilization of a pyrene residue (-Py) onto FEP-APS (FEP-aminopropyl silane) surfaces and the characterization of FEP-APS-Py using steady-state and time-resolved fluorescence spectroscopy. Among the immobilization schemes tested, we found that the covalent coupling of pyrene-sulfonyl chloride to FEP-APS is the easiest and yields the most photostable FEP-APS-Py derivative. Steady-state emission spectra of FEP-APS-Py in contact with H2O, β-cyclodextrin (β-CD), and sodium dodecylsulfate (SDS) aqueous solutions differ considerably from those of Py-SO3 in solution. Time-resolved fluorescence spectroscopy of FEP-APS-Py demonstrates that the decay kinetics are strongly affected by the presence of ionic quenchers and molecular oxygen, as well as β-CD and SDS. The results are consistent with the suggestion that the APS-Py moiety undergoes a slow time-dependent reconfiguration at the FEP/APS interface.

EMI Series Mechanistic Investigation of a Visible Light Mediated Dehalogenation/Cyclisation Reaction using Iron(III), Iridium(III) and Ruthenium(II) Photosensitizers

2021 ◽  
Author(s):  
Akin Aydogan ◽  
Rachel Bangle ◽  
Simon De Kreijger ◽  
John Dickenson ◽  
Michael L Singleton ◽  
...  
Keyword(s):  
Steady State ◽  
Visible Light ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Time Resolved ◽  
Femtosecond Transient Absorption ◽  
Mechanistic Investigation ◽  
Femtosecond Transient Absorption Spectroscopy ◽  
Visible Light Driven ◽  
Time Resolved Infrared Spectroscopy

The mechanism of a visible light-driven dehalogenation/cyclization reaction was investigated using ruthenium(II), iridium(III) and iron(III) photosensitizers by means of steady-state photoluminescence, time-resolved infrared spectroscopy, and nanosecond/femtosecond transient absorption spectroscopy. The...

Mapping of exciton–exciton annihilation in MEH-PPV by time-resolved spectroscopy: experiment and microscopic theory

2017 ◽  
Vol 19 (47) ◽  
pp. 31989-31996 ◽  
Author(s):  
Kilian Hader ◽  
Cristina Consani ◽  
Tobias Brixner ◽  
Volker Engel
Keyword(s):  
Transient Absorption ◽  
Laser Intensity ◽  
Microscopic Theory ◽  
Time Resolved ◽  
Time Resolved Spectroscopy ◽  
Spectroscopy Experiment ◽  
Exciton Annihilation

Transient absorption traces taken on samples of the polymer MEH-PPV are measured as a function of the laser intensity.

scholarly journals Identification of a Bridge-specific Intramolecular Exciton Dissociation Pathway in Donor-π-acceptor Alternating Conjugated Polymers 

2020 ◽  
Author(s):  
Zhaoyong Jiao ◽  
Tingting Jiang ◽  
Zhongpo Zhou ◽  
Chaochao Qin ◽  
Jinyou Long ◽  
...  
Keyword(s):  
Steady State ◽  
Conjugated Polymers ◽  
Organic Solar Cells ◽  
Transient Absorption ◽  
Dissociation Pathway ◽  
Relaxation Dynamics ◽  
Exciton Dissociation ◽  
Time Resolved ◽  
High Efficient ◽  
Conversion Efficiencies

Abstract Intramolecular exciton dissociation is critical for high efficient mobile charge carrier generations in organic solar cells. Yet despite much attention, the effects of π bridges on exciton dissociation dynamics in Donor-π-Acceptor (D-π-A) alternating conjugated polymers remain still unclear. Here, using a combination of femtosecond time-resolved transient absorption (TA) spectroscopy and steady-state spectroscopy, we track ultrafast intramolecular exciton relaxation dynamics in three D-π-A alternating conjugated polymers which were synthesized by Qin's group and named HSD-A, HSD-B, HSD-C. It is found that the addition of thiophene unit as π bridges will lead to the red shift of steady-state absorption spectrum. Importantly, we reveal the existence of a new intramolecular exciton dissociation pathway mediated by a bridge-specific charge transfer (CT') state with the TA fingerprint peak at 1200 nm in π-bridged HSD-B and HSD-C. This CT' state results in higher electron capture rates for HSD-B and HSD-C as compared to HSD-A. Depending on the proportion of CT' state and nongeminate recombination are important step for the understanding of high power conversion efficiencies in HSD-B than in HSD-C. We propose that this bridge-specific exciton dissociation pathway plays an important role in ultrafast intramolecular exciton dissociation of organic photovoltaic material D-π-A alternating conjugated polymers.

scholarly journals Photophysical properties of two novel tetraphenylporphyrins substituted by guanidiniocarbonyl and monocyclic guanidine groups

2001 ◽  
Vol 3 (3) ◽  
pp. 147-151 ◽  
Author(s):  
Pavel Kubát ◽  
Kamil Lang ◽  
Vladimír Král ◽  
Franz P. Schmidtchen
Keyword(s):  
Steady State ◽  
Quantum Yield ◽  
Singlet Oxygen ◽  
Electronic Absorption Spectra ◽  
Photophysical Properties ◽  
Soret Band ◽  
Monomeric Form ◽  
High Quantum Yield ◽  
Time Resolved ◽  
J Aggregates

Photophysical properties of two novel guanidiniocarbonyl (I) and monocyclic guanidine (II) tetraphenylporphyrins and their interaction with DNA were investigated by steady-state and time-resolved absorption and emission spectroscopies.Istays predominantly monomeric in aqueous solutions. It produces singlet oxygen with high quantum yield(ΦΔ=0.67)that is typical for monomeric porphyrins. The electronic absorption spectra ofIare not influenced by interaction with DNA. This is in contrast with monomeric tetratolylporphyrins bearing phosphonium,ammonium and pyridinium groups where the formation of stable complexes with DNA is accompanied by a characteristic red shift of the Soret band.IIextensively forms Hand J-aggregates,which do not produce singlet oxygen(ΦΔ<0.01). In the presence of DNA only a small fraction ofIIremains in monomeric form that is bound to DNA exterior.

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