Quantum Yields of the Photochemical Reduction of Ceric Ions by Water and Evidence for the Dimerization of Ceric Ions

1948 ◽  
Vol 70 (7) ◽  
pp. 2476-2481 ◽  
Author(s):  
Lawrence J. Heidt ◽  
Maynard E. Smith
Keyword(s):  
Quantum Yields ◽  
Photochemical Reduction

Photocatalytic Effect of Fe(III) on Oxidation of Two-Carbon Substrates Related to Natural Waters

1994 ◽  
Vol 59 (5) ◽  
pp. 1066-1076 ◽  
Author(s):  
Šárka Klementová ◽  
Dana M. Wagnerová
Keyword(s):  
Mathematical Model ◽  
Natural Waters ◽  
Substrate Oxidation ◽  
Quantum Yields ◽  
Ferric Ions ◽  
Photochemical Reduction ◽  
Photocatalytic Effect ◽  
Carbon Substrates ◽  
Glyoxalic Acid ◽  
The Common

The influence of ferric ions on photoinitiated reaction of dioxygen with two carbon organic acids, aldehydes and alcohols related to natural waters was demonstrated. Photocatalytic effect of ferric ions, i.e. photochemical reduction of Fe(III) as the catalyst generating step, has been found to be the common principal of these reactions. The overall quantum yields of the reactions are in the range from 0.3 to 1.2. A mathematical model designed for the mechanism of cyclic generation of catalyst in the singlet substrate oxidation by O2 was applied to the system glyoxalic acid + Fe(III); a fair agreement between the simulated and experimental kinetic curves was obtained. The experimental rate constant is 4.4 .10-4 s -1.

Selective photochemical reduction of carbon-chlorine bond in fluoropropanoates and its quantum yields

1983 ◽  
Vol 48 (3) ◽  
pp. 766-771 ◽  
Author(s):  
Oldřich Paleta ◽  
Rudolf Ježek ◽  
Václav Dědek
Keyword(s):  
Ultraviolet Light ◽  
Quantum Yields ◽  
Reduction Mechanism ◽  
Photochemical Reduction ◽  
A Chain ◽  
Chlorine Bond

Ultraviolet light initiated reduction of methyl 2,2,3-trichlorodifluoropropanoate (I), methyl 2,3-dichlorotrifluoropropanoate (II) and methyl 2-chlorotetrafluoropropanoate (III) in 2-propanol afforded methyl 2,3-dichloro-3,3-difluoropropanoate (IV), methyl 3-chloro-2,3,3-trifluoropropanoate (V) and methyl 2,3,3,3-tetrafluoropropanoate (VI) in the respective yields 81%, 86% and 75%. Maximum quantum yields, φmax, of the reduction at 254 nm for the ester IV, V and VI are 225, 240 and 270, respectively, indicating thus a chain reduction mechanism.

Highly Luminescent 4-Pyridyl-Extended Dithieno[3,2-b:2′,3′-d]phospholes

2020 ◽  
Author(s):  
Thomas Baumgartner ◽  
Paul Demay-Drouhard
Keyword(s):  
Electrochemical Properties ◽  
Quantum Yields

The unexpectedly challenging synthesis of 4-pyridyl-extended dithienophospholes is reported. The optical and electrochemical properties of the phosphoryl-bridged species were studied experimentally and computationally, and their properties compared to their non-<i>P</i>-bridged congeners. The 4-pyridyl-extended dithieno-phospholes display quantitative luminescence quantum yields in solution.<br><br>

Highly Luminescent 4-Pyridyl-Extended Dithieno[3,2-b:2′,3′-d]phospholes

2020 ◽  
Author(s):  
Thomas Baumgartner ◽  
Paul Demay-Drouhard
Keyword(s):  
Electrochemical Properties ◽  
Quantum Yields

The unexpectedly challenging synthesis of 4-pyridyl-extended dithienophospholes is reported. The optical and electrochemical properties of the phosphoryl-bridged species were studied experimentally and computationally, and their properties compared to their non-<i>P</i>-bridged congeners. The 4-pyridyl-extended dithieno-phospholes display quantitative luminescence quantum yields in solution.<br><br>

High-Temperature Synthesis of CdSe-Based Core/Shell, Core/Shell/Shell, and Core/Graded-Shell Nanoplatelets for Stable and Efficient Narrowband Emitters

2019 ◽  
Author(s):  
Aurelio A. Rossinelli ◽  
Henar Rojo ◽  
Aniket S. Mule ◽  
Marianne Aellen ◽  
Ario Cocina ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Temperature ◽  
Equilibrium Shape ◽  
Size Variation ◽  
Crystal Defects ◽  
Atomic Scale ◽  
Quantum Yields ◽  
Core Shell ◽  
Compositional Gradient ◽  
High Quality

<div>Colloidal semiconductor nanoplatelets exhibit exceptionally narrow photoluminescence spectra. This occurs because samples can be synthesized in which all nanoplatelets share the same atomic-scale thickness. As this dimension sets the emission wavelength, inhomogeneous linewidth broadening due to size variation, which is always present in samples of quasi-spherical nanocrystals (quantum dots), is essentially eliminated. Nanoplatelets thus offer improved, spectrally pure emitters for various applications. Unfortunately, due to their non-equilibrium shape, nanoplatelets also suffer from low photo-, chemical, and thermal stability, which limits their use. Moreover, their poor stability hampers the development of efficient synthesis protocols for adding high-quality protective inorganic shells, which are well known to improve the performance of quantum dots. <br></div><div>Herein, we report a general synthesis approach to highly emissive and stable core/shell nanoplatelets with various shell compositions, including CdSe/ZnS, CdSe/CdS/ZnS, CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S, and CdSe/ZnSe. Motivated by previous work on quantum dots, we find that slow, high-temperature growth of shells containing a compositional gradient reduces strain-induced crystal defects and minimizes the emission linewidth while maintaining good surface passivation and nanocrystal uniformity. Indeed, our best core/shell nanoplatelets (CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S) show photoluminescence quantum yields of 90% with linewidths as low as 56 meV (19.5 nm at 655 nm). To confirm the high quality of our different core/shell nanoplatelets for a specific application, we demonstrate their use as gain media in low-threshold ring lasers. More generally, the ability of our synthesis protocol to engineer high-quality shells can help further improve nanoplatelets for optoelectronic devices.</div>

Symmetry Breaking and the Turn-On Fluorescence of Small, Highly Strained Carbon Nanohoops

2019 ◽  
Author(s):  
Terri Lovell ◽  
Curtis Colwell ◽  
Lev N. Zakharov ◽  
Ramesh Jasti
Keyword(s):  
Symmetry Breaking ◽  
Theoretical Work ◽  
P Systems ◽  
Quantum Yields ◽  
Size Dependent ◽  
New Class ◽  
Carbon Carbon Bond ◽  
Conjugated Macrocycles ◽  
Structural Manipulation ◽  
Highly Strained

<p>[<i>n</i>]Cycloparaphenylenes, or “carbon nanohoops,” are unique conjugated macrocycles with radially oriented p-systems similar to those in carbon nanotubes. The centrosymmetric nature and conformational rigidity of these molecules lead to unusual size-dependent photophysical characteristics. To investigate these effects further and expand the family of possible structures, a new class of related carbon nanohoops with broken symmetry is disclosed. In these structures, referred to as <i>meta</i>[<i>n</i>]cycloparaphenylenes, a single carbon-carbon bond is shifted by one position in order to break the centrosymmetric nature of the parent [<i>n</i>]cycloparaphenylenes. Advantageously, the symmetry breaking leads to bright emission in the smaller nanohoops, which are typically non-fluorescent due to optical selection rules. Moreover, this simple structural manipulation retains one of the most unique features of the nanohoop structures-size dependent emissive properties with relatively large extinction coefficents and quantum yields. Inspired by earlier theoretical work by Tretiak and co-workers, this joint synthetic, photophysical, and theoretical study provides further design principles to manipulate the optical properties of this growing class of molecules with radially oriented p-systems.</p>

Symmetry Breaking and the Turn-On Fluorescence of Small, Highly Strained Carbon Nanohoops

2019 ◽  
Author(s):  
Terri Lovell ◽  
Curtis Colwell ◽  
Lev N. Zakharov ◽  
Ramesh Jasti
Keyword(s):  
Symmetry Breaking ◽  
Theoretical Work ◽  
P Systems ◽  
Quantum Yields ◽  
Size Dependent ◽  
New Class ◽  
Carbon Carbon Bond ◽  
Conjugated Macrocycles ◽  
Structural Manipulation ◽  
Highly Strained

<p>[<i>n</i>]Cycloparaphenylenes, or “carbon nanohoops,” are unique conjugated macrocycles with radially oriented p-systems similar to those in carbon nanotubes. The centrosymmetric nature and conformational rigidity of these molecules lead to unusual size-dependent photophysical characteristics. To investigate these effects further and expand the family of possible structures, a new class of related carbon nanohoops with broken symmetry is disclosed. In these structures, referred to as <i>meta</i>[<i>n</i>]cycloparaphenylenes, a single carbon-carbon bond is shifted by one position in order to break the centrosymmetric nature of the parent [<i>n</i>]cycloparaphenylenes. Advantageously, the symmetry breaking leads to bright emission in the smaller nanohoops, which are typically non-fluorescent due to optical selection rules. Moreover, this simple structural manipulation retains one of the most unique features of the nanohoop structures-size dependent emissive properties with relatively large extinction coefficents and quantum yields. Inspired by earlier theoretical work by Tretiak and co-workers, this joint synthetic, photophysical, and theoretical study provides further design principles to manipulate the optical properties of this growing class of molecules with radially oriented p-systems.</p>

Synthesis and Biological Evaluations of Organoruthenium Scaffolds: A Comprehensive Update

2018 ◽  
Vol 15 (2) ◽  
pp. 179-207
Author(s):  
Ashaparna Mondal ◽  
Priyankar Paira
Keyword(s):  
Singlet Oxygen ◽  
Anticancer Agents ◽  
Ruthenium Complexes ◽  
Chemotherapeutic Agents ◽  
Quantum Yields ◽  
Ros Generation ◽  
Standard Drug ◽  
Cellular Environment ◽  
Theranostic Agents

Background: Currently ruthenium complexes are immerging as effective anticancer agents due to their less toxicity, better antiproliferative and antimetastatic activity, better stability in cellular environment and most importantly variable oxidation and co-ordination states of ruthenium allows binding this molecule with a variety of ligands. So in past few years researchers have shifted their interest towards organoruthenium complexes having good fluorescent profile that may be applicable for cancer theranostics. Nowadays, photodynamic therapy has become more acceptable because of its easy and effective approach towards killing cancer cells. Objective: Objective of this review article is to shed light on synthesis, characterization, stability and fluorescence studies of various ruthenium [Ru(II) and Ru(III)] complexes and different bioactivity studies conducted with the synthesized compounds to test their candidacy as potent chemotherapeutic agents. Methods: Various heterocyclic ligands containing N,O and S as heteroatom mainly were prepared and subjected to complexation with ruthenium-p-cymene moiety. In most cases [Ru(η6-p-cymene)(µ-Cl)Cl]2 was used as ruthenium precursor and the reactions were conducted in various alcohol medium such as methanol, ethanol or propanol. The synthesized complexes were characterized by 1H NMR and 13C NMR spectroscopy, GC-MS, ESI-MS, elemental analysis and single crystal X-ray crystallography methods. Fluorescence study and stability study were conducted accordingly using water, PBS buffer or DMSO. Stable compounds were considered for cell viability studies. To study the efficacy of the compounds in ROS generation as photosensitizers, in few cases, singlet oxygen quantum yields in presence of light were calculated. Suitable compounds were selected for in vitro & in vivo antiproliferative, anti-invasive activity studies. Result: Many newly synthesized compounds were found to have less IC50 compared to a standard drug cysplatin. Those compounds were also stable preferably in physiological conditions. Good fluorescence profile and ROS generation ability were observed for few compounds. Conclusion: Numerous ruthenium complexes were developed which can be used as cancer theranostic agents. Few molecules were synthesized as photosensitizers which were supposed to generate reactive singlet oxygen species in targeted cellular environment in presence of a particular type of light and thereby ceasing cancer cell growth.

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