Light-harvesting porphyrazines to enable intramolecular singlet fission

Nanoscale ◽  
2019 ◽  
Vol 11 (46) ◽  
pp. 22286-22292 ◽  
Author(s):  
Diana-Paola Medina ◽  
Ilias Papadopoulos ◽  
Giulia Lavarda ◽  
Henrik Gotfredsen ◽  
Parisa R. Rami ◽  
...  
Keyword(s):  
Light Harvesting ◽  
Quantum Yields ◽  
Singlet Fission ◽  
Triplet Quantum Yields

Quantitative intramolecular FRET from a porphyrazine to pentacene enhances singlet fission with triplet quantum yields up to 200% ± 20% in benzonitrile.

scholarly journals Singlet fission in pentacene dimers

2015 ◽  
Vol 112 (17) ◽  
pp. 5325-5330 ◽  
Author(s):  
Johannes Zirzlmeier ◽  
Dan Lehnherr ◽  
Pedro B. Coto ◽  
Erin T. Chernick ◽  
Rubén Casillas ◽  
...  
Keyword(s):  
Solar Energy ◽  
Energy Conversion ◽  
Ground State ◽  
Room Temperature ◽  
Quantum Yields ◽  
Compelling Evidence ◽  
Singlet Fission ◽  
Conversion Efficiencies ◽  
Triplet Quantum Yields ◽  
Conversion Scheme

Singlet fission (SF) has the potential to supersede the traditional solar energy conversion scheme by means of boosting the photon-to-current conversion efficiencies beyond the 30% Shockley–Queisser limit. Here, we show unambiguous and compelling evidence for unprecedented intramolecular SF within regioisomeric pentacene dimers in room-temperature solutions, with observed triplet quantum yields reaching as high as 156 ± 5%. Whereas previous studies have shown that the collision of a photoexcited chromophore with a ground-state chromophore can give rise to SF, here we demonstrate that the proximity and sufficient coupling through bond or space in pentacene dimers is enough to induce intramolecular SF where two triplets are generated on one molecule.

scholarly journals Similar chemical structures, dissimilar triplet quantum yields: a CASPT2 model rationalizing the trend of triplet quantum yields in nitroaromatic systems

2019 ◽  
Vol 21 (20) ◽  
pp. 10514-10522 ◽  
Author(s):  
Angelo Giussani ◽  
Graham A. Worth
Keyword(s):  
Quantum Yields ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Triplet Quantum Yields

S1/S0 accessibility strongly influences the triplet quantum yields of nitronaphthalenes.

Spectrofluorometric studies. VIII. The effect of CO2 and CHCl3 on the photochemistry of monofluorobenzene

1970 ◽  
Vol 48 (10) ◽  
pp. 1607-1613 ◽  
Author(s):  
M. E. MacBeath ◽  
I. Unger
Keyword(s):  
Quantum Yield ◽  
Quantum Yields ◽  
Vibrationally Excited ◽  
Excited Triplet ◽  
Improved Technique ◽  
Triplet Quantum Yields

The sensitized emission of biacetyl technique was used to study the effect of CHCl3 and CO2 on the triplet quantum yields of both benzene and monofluorobenzene.The monofluorobenzene was studied at λ excitation (λex) of 2470, 2590, and 2670 Å. At 2470 Å, the triplet yield increased by over 40% with both added gases; at λex 2590 Å, by around 30%; and at λex 2670 Å, about 20%. CHCl3 is slightly more effective than CO2 in enhancing the biacetyl phosphorescent yield. The quantum yield of fluorescence was unchanged with these added gases. Using a slightly improved technique, the comparison irradiation of a benzene–biacetyl mixture at λex 2540 Å with added CHCl3 was repeated. The results confirmed that the biacetyl phosphorescent yield decreased with increasing pressures of CHCl3, but suggest that the effect is not as great as previously reported. At the same wavelength, the triplet yield is unaffected by the addition of CO2. The quantum yield of fluorescence of benzene is virtually unaffected by the added gases. The data suggest that in the monofluorobenzene case the CO2 and CHCl3 are quenching vibrationally excited triplet fluorobenzene molecules.

scholarly journals A 3D Hierarchical Pancake-Like Porous Carbon Nitride for Highly Enhanced Visible-Light Photocatalytic H2 Evolution

Catalysts ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 77
Author(s):  
Xiaobin Qiu ◽  
Lingfang Qiu ◽  
Mengfan Ma ◽  
Yingying Hou ◽  
Shuwang Duo
Keyword(s):  
Visible Light ◽  
Porous Carbon ◽  
Carbon Nitride ◽  
Light Harvesting ◽  
Quantum Yields ◽  
Light Illumination ◽  
H2 Evolution ◽  
Photoelectric Properties ◽  
Polymeric Carbon ◽  
Photocatalytic H2 Evolution

Polymeric carbon nitride is a fascinating visible-light-response metal-free semiconductor photocatalyst in recent decades. Nevertheless, the photocatalytic H2 efficiency is unsatisfactory due to the insufficient visible-light harvesting capacity and low quantum yields caused by the bulky structure seriously limited its applications. To overcome these defects, in this research, a 3D hierarchical pancake-like porous carbon nitride (PPCN) was successfully fabricated by a facile bottom-up method. The as-prepared photocatalyst exhibit enlarged surface area, enriched reactive sites, improved charge carrier transformation and separation efficiency, and expanded bandgap with a more negative conduction band towardan enhanced reduction ability. All these features synergistically enhanced the photocatalytic H2 evolution efficiency of 3% Pt@PPCN (430 µmol g−1 h−1) under the visible light illumination (λ ≥ 420 nm), which was nine-fold higher than that of 3% Pt@bulk C3N4 (BCN) (45 µmol g−1 h−1). The improved structure and enhanced photoelectric properties were systematically investigated by different characterization techniques. This research may provide an insightful synthesis strategy for polymeric carbon nitride with excellent light-harvesting capacity and enhanced separation of charges toward remarkable photocatalytic H2 for water splitting.

scholarly journals Uncovering dark multichromophoric states in Peridinin–Chlorophyll–Protein

2020 ◽  
Vol 17 (164) ◽  
pp. 20190736
Author(s):  
Elliot J. Taffet ◽  
Francesca Fassioli ◽  
Zi S. D. Toa ◽  
David Beljonne ◽  
Gregory D. Scholes
Keyword(s):  
Crystal Structure ◽  
Excited States ◽  
Quantum Chemical ◽  
Light Harvesting ◽  
Singlet Fission ◽  
Chlorophyll Protein ◽  
Triplet Pair ◽  
A Charge ◽  
Hole Generation ◽  
Chemical Evidence

It has long been recognized that visible light harvesting in Peridinin–Chlorophyll–Protein is driven by the interplay between the bright (S 2 ) and dark (S 1 ) states of peridinin (carotenoid), along with the lowest-lying bright (Q y ) and dark (Q x ) states of chlorophyll- a . Here, we analyse a chromophore cluster in the crystal structure of Peridinin–Chlorophyll–Protein, in particular, a peridinin–peridinin and a peridinin–chlorophyll- a dimer, and present quantum chemical evidence for excited states that exist beyond the confines of single peridinin and chlorophyll chromophores. These dark multichromophoric states, emanating from the intermolecular packing native to Peridinin–Chlorophyll–Protein, include a correlated triplet pair comprising neighbouring peridinin excitations and a charge-transfer interaction between peridinin and the adjacent chlorophyll- a . We surmise that such dark multichromophoric states may explain two spectral mysteries in light-harvesting pigments: the sub-200-fs singlet fission observed in carotenoid aggregates, and the sub-200-fs chlorophyll- a hole generation in Peridinin–Chlorophyll–Protein.

Effect of aggregation of a cationic phthalocyanine in micelles and in the presence of human serum albumin

2006 ◽  
Vol 10 (01) ◽  
pp. 33-42 ◽  
Author(s):  
Myriam E. Rodriguez ◽  
Daniel A. Fernández ◽  
Josefina Awruch ◽  
Silvia E. Braslavsky ◽  
Lelia E. Dicelio
Keyword(s):  
Human Serum Albumin ◽  
Serum Albumin ◽  
Human Serum ◽  
Hydrophobic Interactions ◽  
Photophysical Properties ◽  
Sodium Dodecylsulfate ◽  
Water Soluble ◽  
Quantum Yields ◽  
Ionic Interactions ◽  
Triplet Quantum Yields

The photophysical properties of tetrakis(1,1-dimethyl-2-trimethylammonium)ethylphthalocyaninato zinc(II) tetraiodide (I) – a water-soluble cationic phthalocyanine – are presented in the presence of human serum albumin (HSA) and in micelles of sodium dodecylsulfate ( SDS ) and hexadecyltrimethylammonium chloride ( CTAC ). Spectrophotometric measurements showed that the surfactants SDS and CTAC induce monomerization of I, although the latter less efficiently than the former. This effect is less pronounced in the presence of HSA. The strength of this effect is evaluated through dimerization constants, which are Kd = (5 ± 1) × 105 m−1 in SDS , (1.5 ± 0.5) × 106 M −1 in CTAC , and (1.8 ± 0.9) × 106 M −1 in HSA. Fluorescence experiments confirm that aggregation of I drops as the concentration of surfactant is raised. Triplet quantum yields also decreased upon aggregation and were Φ T = 0.59, 0.16, and < 0.01 in SDS , CTAC , and HSA, respectively. These results indicate that the affinity of I for the environment is not just due to ionic interactions; hydrophobic interactions play an equally important role.

LASER INTENSITY AND THE COMPARATIVE METHOD FOR DETERMINATION OF TRIPLET QUANTUM YIELDS

1978 ◽  
Vol 28 (2) ◽  
pp. 277-281 ◽  
Author(s):  
R. Bensasson ◽  
C. R. Goldschmidt ◽  
E. J. Land ◽  
T. G. Truscott
Keyword(s):  
Laser Intensity ◽  
Comparative Method ◽  
Quantum Yields ◽  
Triplet Quantum Yields

Tetra and octa(2,6-di-iso-propylphenoxy)-substituted phthalocyanines: a comparative study among their photophysicochemical properties

2012 ◽  
Vol 16 (01) ◽  
pp. 163-174 ◽  
Author(s):  
Ahmad Tuhl ◽  
Wadzanai Chidawanayika ◽  
Hamada Mohamed Ibrahim ◽  
Nouria Al-Awadi ◽  
Christian Litwinski ◽  
...  
Keyword(s):  
Fine Tuning ◽  
Quantum Yields ◽  
Steric Interaction ◽  
Fluorescence Quantum Yields ◽  
H Nmr ◽  
Derivative Series ◽  
Uv Visible ◽  
Almost All ◽  
Triplet Quantum Yields ◽  
Triplet Lifetime

This work reports on the synthesis of novel metal free, zinc, aluminum, gallium and indium tetra and octa (2,6-di-iso-propylphenoxy)-substituted phthalocyanine derivatives. UV-visible and 1H NMR analyses confirm that a non-planar conformation, adapted by the phenoxy substituents due to steric interaction in both derivative series, perfectly discourage cofacial aggregation. Fluorescence quantum yields vary as a function of the number of substituents on the ring periphery, while the fluorescence lifetimes display no distinct trend. Triplet quantum yields are significantly larger for the tetra 2,6-di-iso-propylphenoxy- substituted derivatives relative to their corresponding octa-substituted species. However there was no overall trend in the triplet lifetime values. For almost all of the phthalocyanine derivatives, singlet oxygen was produced with relatively good quantum yields. This study explores the possibility of fine-tuning their physicochemical properties by simple structural modification.

Sign in / Sign up

Export Citation Format

Share Document