A Highly Fluorescent Dinuclear Aluminium Complex with Near-Unity Quantum Yield

The high natural abundance of aluminium makes the respective fluorophores attractive for various optical applications, but photoluminescence quantum yields above 0.7 have yet not been reported for solutions of aluminium complexes. In this contribution, a dinuclear aluminium(III) complex featuring enhanced photoluminescence properties is described. Its facile one-pot synthesis originates from a readily available precursor and trimethyl aluminium. In solution, the complex exhibits an unprecedented photoluminescence quantum yield near unity (Φabsolute 1.0 ± 0.1) and an excited-state lifetime of 2.3 ns. In the solid state, J-aggregation and aggregation-caused quenching are noticed, but still quantum yields of 0.6 are observed. Embedding the complex in electrospun nonwoven fabrics yields a highly fluorescent fleece possessing a quantum yield of 0.9 ± 0.04.

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Fluorescence quantum yield and excited state lifetime determination by phase sensitive photoacoustics: concept and theory

Optics Letters ◽

10.1364/ol.43.005074 ◽

2018 ◽

Vol 43 (20) ◽

pp. 5074 ◽

Cited By ~ 2

Author(s):

Gregor Langer ◽

Thomas Berer

Keyword(s):

Excited State ◽

Quantum Yield ◽

Fluorescence Quantum Yield ◽

Excited State Lifetime ◽

Phase Sensitive

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Morphology control and photoluminescence properties of Eu3+-activated Y4Al2O9 nanophosphors for solid state lighting applications

CrystEngComm ◽

10.1039/c8ce00289d ◽

2018 ◽

Vol 20 (18) ◽

pp. 2540-2552 ◽

Cited By ~ 15

Author(s):

Antika Das ◽

Subhajit Saha ◽

Karamjyoti Panigrahi ◽

Anuradha Mitra ◽

Rituparna Chatterjee ◽

...

Keyword(s):

Excited State ◽

Solid State ◽

Morphology Control ◽

Solid State Lighting ◽

Color Purity ◽

Photoluminescence Properties ◽

Excited State Lifetime

Spherical Eu3+:Y4Al2O9 nanophosphors exhibit brilliant PL behavior with enhanced color purity and excited state lifetime.

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Hinged and Wide: A New P^P Ligand for Emissive [Cu(P^P)(N^N)][PF6] Complexes

Molecules ◽

10.3390/molecules24213934 ◽

2019 ◽

Vol 24 (21) ◽

pp. 3934 ◽

Cited By ~ 1

Author(s):

Sarah Keller ◽

Matthias Bantle ◽

Alessandro Prescimone ◽

Edwin C. Constable ◽

Catherine E. Housecroft

Keyword(s):

Mass Spectrometry ◽

Excited State ◽

Quantum Yield ◽

Delayed Fluorescence ◽

Ionization Mass ◽

Thermally Activated Delayed Fluorescence ◽

Thermally Activated ◽

Single Crystal Structures ◽

Photoluminescence Quantum Yield ◽

Deaerated Solution

Heteroleptic [Cu(BIPHEP)(N^N)][PF6] complexes (BIPHEP = 1,1′-biphenyl-2,2′-diylbis(diphenylphosphane)), in which N^N is 2,2′-bipyridine (bpy), 6-methyl-2,2′-bipyridine (6-Mebpy), 6-ethyl-2,2′-bipyridine (6-Etbpy), or 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy), have been synthesized and characterized using multinuclear NMR spectroscopies and electrospray ionization mass spectrometry. The single crystal structures of [Cu(BIPHEP)(bpy)][PF6]∙CH2Cl2, [Cu(BIPHEP)(5,5′-Me2bpy)][PF6]∙CH2Cl2, [Cu(BIPHEP)(6-Mebpy)][PF6]∙Et2O∙0.5H2O and [Cu(BIPHEP)(6-Etbpy)][PF6] confirm distorted tetrahedral {Cu(P^P)(N^N)} coordination environments. Each compound shows a quasi-reversible Cu+/Cu2+ process. In deaerated solution, the compounds are weak emitters. Powdered samples are yellow emitters (λemmax in the range 558–583 nm) and [Cu(BIPHEP)(5,5′-Me2bpy)][PF6] exhibits the highest photoluminescence quantum yield (PLQY = 14%). On cooling to 77 K (frozen 2-methyloxolane), the emission maxima are red-shifted and the excited state lifetimes increase from τ1/2 < 8 μs, to τ1/2 values of up to 53 μs, consistent with the compounds with N^N = 6-Mebpy, 6-Etbpy and 5,5′-Me2bpy exhibiting thermally activated delayed fluorescence (TADF).

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ZnO nanocrystals derived from organometallic approach: Delineating the role of organic ligand shell on physicochemical properties and nano-specific toxicity

Scientific Reports ◽

10.1038/s41598-019-54509-z ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Małgorzata Wolska-Pietkiewicz ◽

Katarzyna Tokarska ◽

Anna Wojewódzka ◽

Katarzyna Wójcik ◽

Elżbieta Chwojnowska ◽

...

Keyword(s):

Quantum Yield ◽

Physicochemical Properties ◽

Semiconductor Nanocrystals ◽

Organic Ligand ◽

Tail Length ◽

Hydrodynamic Diameter ◽

One Pot ◽

Core Diameter ◽

Photoluminescence Quantum Yield ◽

Toxicological Profile

AbstractThe surface organic ligands have profound effect on modulation of different physicochemical parameters as well as toxicological profile of semiconductor nanocrystals (NCs). Zinc oxide (ZnO) is one of the most versatile semiconductor material with multifarious potential applications and systematic approach to in-depth understand the interplay between ZnO NCs surface chemistry along with physicochemical properties and their nano-specific toxicity is indispensable for development of ZnO NCs-based devices and biomedical applications. To this end, we have used recently developed the one-pot self-supporting organometallic (OSSOM) approach as a model platform to synthesize a series of ZnO NCs coated with three different alkoxyacetate ligands with varying the ether tail length which simultaneously act as miniPEG prototypes. The ligand coating influence on ZnO NCs physicochemical properties including the inorganic core size, the hydrodynamic diameter, surface charge, photoluminescence (quantum yield and decay time) and ZnO NCs biological activity toward lung cells was thoroughly investigated. The resulting ZnO NCs with average core diameter of 4-5 nm and the hydrodynamic diameter of 8-13 nm exhibit high photoluminescence quantum yield reaching 33% and a dramatic slowing down of charge recombination up to 2.4 µs, which is virtually unaffected by the ligand’s character. Nano-specific ZnO NCs-induced cytotoxicity was tested using MTT assay with normal (MRC-5) and cancer (A549) human lung cell lines. Noticeably, no negative effect has been observed up to the NCs concentration of 10 µg/mL and essentially very low negative toxicological impact could be noticed at higher concentrations. In the latter case, the MTT data analysis indicate that there is a subtle interconnection between inorganic core-organic shell dimensions and toxicological profile of ZnO NCs (strikingly, the NCs coated by the carboxylate bearing a medium ether chain length exhibit the lowest toxicity level). The results demonstrate that, when fully optimized, our organometallic self-supporting approach can be a highly promising method to obtain high-quality and bio-stable ligand-coated ZnO NCs.

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The mechanism of the photochemical cycloaddition reaction of N-benzoylindole with cyclopentene

Canadian Journal of Chemistry ◽

10.1139/v90-262 ◽

1990 ◽

Vol 68 (10) ◽

pp. 1685-1692 ◽

Cited By ~ 10

Author(s):

Bimsara W. Disanayaka ◽

Alan C. Weedon

Keyword(s):

Excited State ◽

Quantum Yield ◽

Ground State ◽

Mechanistic Model ◽

Cycloaddition Reaction ◽

Intersystem Crossing ◽

Triplet Excited State ◽

Excited State Lifetime ◽

Yield Data ◽

Counting Procedure

The mechanism of the photochemical cycloaddition reaction between N-benzoylindole, 1, and cyclopentene to give cyclobutane adducts 2 and 3 has been examined. The triplet excited state lifetime and quantum yield of intersystem crossing were determined for 1 as (2.8 ± 0.3) × 10−8 s and 0.39 ± 0.01, respectively, using the triplet counting procedure. In addition, the dependence of the quantum yield of cycloadduct formation upon the concentration of cyclopentene and upon the concentration of excited state quenchers has been determined. The results are used to propose a mechanistic model in which the triplet excited state of 1 reacts with cyclopentene to give a triplet 1,4-biradical intermediate. Following spin inversion the biradical intermediate reverts to the ground state starting materials or proceeds to the products 2 and 3; this partitioning, along with the quantum yield of intersystem crossing, gives rise to a limiting quantum yield of cycloaddition at infinite alkene concentration of 0.061. It is calculated that 84% of the biradical intermediates revert to the starting materials and 16% proceed to cycloadducts. The quantum yield data are also used to calculate two independent values of the rate constant for reaction of the triplet excited 1 with alkene; the values are (1.8 ± 0.1) × 107M−1 s−1 and (4.0 ± 0.8) × 106 M−1 s−1'. Some evidence for self quenching of the triplet excited state of 1 by ground state 1 was also observed. The quantum yield of intersystem crossing and the triplet excited state lifetime of 1 were found to vary with the solvent used; this is discussed in terms of the possible existence of a charge transfer triplet excited state. Keywords: indole, photocycloaddition, mechanism.

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Quantification of Anisotropy-Related Uncertainties in Relative Photoluminescence Quantum Yield Measurements of Nanomaterials – Semiconductor Quantum Dots and Rods

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2014-0626 ◽

2015 ◽

Vol 229 (1-2) ◽

Cited By ~ 6

Author(s):

Christian Würth ◽

Daniel Geißler ◽

Ute Resch-Genger

Keyword(s):

Quantum Dots ◽

Quantum Yield ◽

Semiconductor Quantum Dots ◽

Quantum Yields ◽

Photoluminescence Quantum Yield

AbstractIn order to assess the anisotropy-related uncertainties of relatively determined photoluminescence quantum yields (

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Towards Prediction of Non-Radiative Decay Pathways in Organic Compounds I: The Case of Naphthalene Quantum Yields

10.26434/chemrxiv.7689092 ◽

2019 ◽

Cited By ~ 1

Author(s):

Alexander Kohn ◽

Zhou Lin ◽

Troy Van Voorhis

Keyword(s):

Machine Learning ◽

Excited State ◽

Quantum Yield ◽

Quantum Dynamics ◽

Density Functional ◽

Rational Design ◽

Radiative Decay ◽

Quantum Yields ◽

Equilibrium Geometry ◽

Radiative Loss

<div>Many emerging technologies depend on human’s ability to control and manipulate the excited-state properties of molecular systems. These technologies include fluorescent</div><div>labeling in biomedical imaging, light harvesting in photovoltaics, and electroluminescence in light-emitting devices. All of these systems suffer from non-radiative loss pathways that dissipate electronic energy as heat, which causes the overall system efficiency to be directly linked to quantum yield (Φ) of the molecular excited state. Unfortunately, Φ is very difficult to predict from first principles because the description of a slow non-radiative decay mechanism requires an accurate description of long-timescale excited-state quantum dynamics. In the present study, we introduce an efficient semiempirical method of calculating the fluorescence quantum yield (Φfl) for molecular chromophores, which, based on machine learning, converts simple electronic energies computed using time-dependent density functional theory (TDDFT) into an estimate of Φfl. As with all machine learning strategies, the algorithm needs to be trained on fluorescent dyes for which Φfl’s are known, so as to provide a black-box method which can later predict Φfl’s for chemically similar chromophores that have not been studied experimentally. As a first illustration of how our proposed algorithm can be trained, we examine a family of 25 naphthalene derivatives. The simplest application of the energy gap law is found to be inadequate to explain the rates of internal conversion (IC) or intersystem crossing (ISC) – the electronic properties of at least one higher-lying electronic state (Sn or Tn) or one far-from-equilibrium geometry are typically needed to obtain accurate results. Indeed, the key descriptors turn out to be the transition state between the Franck–Condon minimum a distorted local minimum near an S0/S1 conical intersection (which governs IC) and the magnitude of the spin–orbit coupling (which governs ISC). The resulting Φfl’s are predicted with reasonable accuracy (±22%), making our approach a promising ingredient for high-throughput screening and rational design of the molecular excited states with desired Φ’s. We thus conclude that our model, while semi-empirical in nature, does in fact extract sound physical insight into the challenge of describing non-radiative relaxations.</div>

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Fluorescence Enhancement of a Microbial Rhodopsin via Electronic Reprogramming

10.26434/chemrxiv.7083257.v2 ◽

2018 ◽

Author(s):

Maria del Carmen Marin ◽

Damianos Agathangelou ◽

Yoelvis Orozco-González ◽

Alessio Valentini ◽

Yoshitaka Kato ◽

...

Keyword(s):

Excited State ◽

Quantum Yield ◽

Excited States ◽

Fluorescence Quantum Yield ◽

Fluorescence Enhancement ◽

Energy Surface ◽

Wild Type ◽

Excited State Lifetime ◽

State Potential ◽

Microbial Rhodopsin

The manuscript reports on two mutations of the photo-sensory protein Anabaena Sensory Rhodopsin and how these mutations modify the fluorescence quantum yield with respect to the wild-type protein. Experimental results are presented and explained theoretically on the basis of mixing of the S1 and S2 excited states. This mixing modulated by electrostatic and steric effects, tunes the excited state potential energy surface, and thereby the excited state lifetime and the fluorescence quantum yield.

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