The Dependence of Quantum Yield on Wavelength and Growth Irradiance

1987 ◽  
Vol 14 (1) ◽  
pp. 69 ◽  
Author(s):  
JR Evans
Keyword(s):  
Quantum Yield ◽  
Oxygen Evolution ◽  
Narrow Band ◽  
Red Light ◽  
Leaf Disc ◽  
Wavelength Dependence ◽  
Oxygen Electrode ◽  
Quantum Yields ◽  
Growth Irradiance ◽  
Spinach Leaves

The wavelength dependence of photosynthetic quantum yield was measured in a leaf disc oxygen electrode using narrow-band interference filters. Photorespiration was suppressed by measuring oxygen evolution in air containing ~ 1% CO2. Rates of oxygen evolution were determined as a function of absorbed irradiances between 0 and 100 �mol quanta m-2 s-1 and the slope was taken as the quantum yield. The wavelength-dependence previously observed in many species was confirmed for pea and spinach leaves. The maximum quantum yields obtained here and by others are close to 0.111 mol O2 mol-1 quanta for red light. Given the wavelength dependence of quantum yield and the spectral distribution of light, the quantum yields for various white lights were calculated to be around 85% of the red maximum. The quantum yields in white light were the same for plants grown at different irradiances. It is argued that the wavelength dependence of quantum yield reflects the distribution of quanta between the two photosystems with the quantum yield dropping at wavelengths strongly absorbed by chlorophyll b as this is mainly associated with photosystem II.

Measurement of photosynthesis in vivo with a leaf disc electrode: correlations between light dependence of steady-state photosynthetic O 2 evolution and chlorophyll a fluorescence transients

1986 ◽  
Vol 227 (1248) ◽  
pp. 267-280 ◽  
Keyword(s):  
Quantum Yield ◽  
Oxygen Evolution ◽  
Leaf Disc ◽  
Light Flux ◽  
Photon Flux ◽  
Photosynthetic Oxygen Evolution ◽  
Disc Electrode ◽  
Excitation Light ◽  
Blue Excitation ◽  
Photosynthetic Oxygen

The application of a leaf disc electrode to the measurement of the quantum yield of photosynthetic oxygen evolution (in saturating carbon dioxide concentrations) is described. The technique was also used to characterize the light-saturation curves for photosynthesis in leaves of spinach plants grown in relatively low (‘shade’) and high (‘sun’) light intensities. It was found that the flux of a blue excitation light required to elicit oscillations in chlorophyll a fluorescence corresponded, approximately, to the flux of (white) light required to saturate photosynthetic oxygen evolution. The requirement was higher for leaves of sun-grown plants (approximately 800 μmol m -2 s -1 ) than for shade-grown plants (approximately 200 μmol m -2 s -1 ). Brief pretreatment of leaf discs from sun-grown plants with D-mannose did not change the quantum yield, but lowered the light saturated rate and the photon flux density required to saturate photosynthesis. Oscillations in fluorescence could then be observed at lower fluxes of blue excitation light, similar to those required by leaves from shade-grown plants. Photoinhibition of shade-grown plants (exposed to full sunlight for 5 h) reduced quantum yield and increased the light flux required for saturation of photosynthesis. Oscillations in fluorescence, normally observed at low fluxes of blue light in these leaves, could not be detected after photoinhibition. These correlations are interpreted and applications of the techniques described are discussed.

scholarly journals Ruthenium-based PACT agents based on bisquinoline chelates: synthesis, photochemistry, and cytotoxicity

2021 ◽  
Author(s):  
Anja Busemann ◽  
Ingrid Flaspohler ◽  
Xue-Quan Zhou ◽  
Claudia Schmidt ◽  
Sina K. Goetzfried ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Cancer Cells ◽  
Cellular Uptake ◽  
Ruthenium Complex ◽  
Human Cancer ◽  
Light Irradiation ◽  
Quantum Yields ◽  
Light Activation ◽  
Human Cancer Cells

AbstractThe known ruthenium complex [Ru(tpy)(bpy)(Hmte)](PF6)2 ([1](PF6)2, where tpy = 2,2’:6’,2″-terpyridine, bpy = 2,2’-bipyridine, Hmte = 2-(methylthio)ethanol) is photosubstitutionally active but non-toxic to cancer cells even upon light irradiation. In this work, the two analogs complexes [Ru(tpy)(NN)(Hmte)](PF6)2, where NN = 3,3'-biisoquinoline (i-biq, [2](PF6)2) and di(isoquinolin-3-yl)amine (i-Hdiqa, [3](PF6)2), were synthesized and their photochemistry and phototoxicity evaluated to assess their suitability as photoactivated chemotherapy (PACT) agents. The increase of the aromatic surface of [2](PF6)2 and [3](PF6)2, compared to [1](PF6)2, leads to higher lipophilicity and higher cellular uptake for the former complexes. Such improved uptake is directly correlated to the cytotoxicity of these compounds in the dark: while [2](PF6)2 and [3](PF6)2 showed low EC50 values in human cancer cells, [1](PF6)2 is not cytotoxic due to poor cellular uptake. While stable in the dark, all complexes substituted the protecting thioether ligand upon light irradiation (520 nm), with the highest photosubstitution quantum yield found for [3](PF6)2 (Φ[3] = 0.070). Compounds [2](PF6)2 and [3](PF6)2 were found both more cytotoxic after light activation than in the dark, with a photo index of 4. Considering the very low singlet oxygen quantum yields of these compounds, and the lack of cytotoxicity of the photoreleased Hmte thioether ligand, it can be concluded that the toxicity observed after light activation is due to the photoreleased aqua complexes [Ru(tpy)(NN)(OH2)]2+, and thus that [2](PF6)2 and [3](PF6)2 are promising PACT candidates. Graphic abstract

Effects of electron-withdrawing groups in imidazole-phenanthroline ligands and their influence on the photophysical properties of EuIII complexes for white light-emitting diodes

2017 ◽  
Vol 41 (18) ◽  
pp. 9826-9839 ◽  
Author(s):  
Boddula Rajamouli ◽  
Rachna Devi ◽  
Abhijeet Mohanty ◽  
Venkata Krishnan ◽  
Sivakumar Vaidyanathan
Keyword(s):  
Thin Film ◽  
Quantum Yield ◽  
White Light ◽  
Light Emitting Diode ◽  
Photophysical Properties ◽  
Red Light ◽  
Europium Complexes ◽  
Light Emitting ◽  
White Light Emitting Diodes ◽  
Phenanthroline Ligands

The red light emitting diode (LED) was fabricated by using europium complexes with InGaN LED (395 nm) and shown digital images, corresponding CIE color coordinates (red region) as well as obtained highest quantum yield of the thin film (78.7%).

Quantum yield of solution photolysis of bicyclo[3.1.0]hexan-3-one and derivatives

1981 ◽  
Vol 59 (11) ◽  
pp. 1607-1609 ◽  
Author(s):  
Karl R. Kopecky ◽  
Rodrigo Rico Gomez
Keyword(s):  
Quantum Yield ◽  
Quantum Yields

The quantum yields for photolysis of 0.25 M solutions of bicyclo[3.1.0]hexan-3-one, 1,5-dimethylbicyclo[3.1.0]hexan-3-one, and tricyclo[4.3.1.0]decan-8-one in pentane or cyclohexane with 313 nm light are 0.44, 0.52, and 0.32, respectively.

New soluble 4-(4-formyl-2,6-dimethoxyphenoxy) substituted phthalocyanines: Synthesis, characterization, photophysical and photochemical properties

2021 ◽  
pp. 1-10
Author(s):  
Ibrahim Erden ◽  
Betül Karadoğan ◽  
Fatma Aytan Kılıçarslan ◽  
Göknur Yaşa Atmaca ◽  
Ali Erdoğmuş
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Fluorescence Quantum Yield ◽  
Metal Ion ◽  
Mass Spectra ◽  
Quantum Yields ◽  
Therapeutic Outcomes ◽  
Ft Ir ◽  
Photochemical Properties ◽  
New Compounds

This work describes the synthesis, spectral and fluorescence properties of bis 4-(4-formyl-2,6-dimethoxyphenoxy) substituted zinc (ZnPc) and magnesium (MgPc) phthalocyanines. The new compounds have been characterized by elemental analysis, UV-Vis, FT-IR, 1H-NMR and mass spectra. Afterward, the effects of including metal ion on the photophysicochemical properties of the complexes were studied in biocompatible solvent DMSO to analyze their potential to use as a photosensitizer in photodynamic therapy (PDT). The fluorescence and singlet oxygen quantum yields were calculated as 0.04–0.15 and 0.70–0.52 for ZnPc and MgPc, respectively. According to the results, MgPc has higher fluorescence quantum yield than ZnPc, while ZnPc has higher singlet oxygen quantum yield than MgPc. The results show that the synthesized complexes can have therapeutic outcomes for cancer treatment.

Terminology, relative photonic efficiencies and quantum yields in heterogeneous photocatalysis. Part II: Experimental determination of quantum yields

1999 ◽  
Vol 71 (2) ◽  
pp. 321-335 ◽  
Author(s):  
Angela Salinaro ◽  
Alexei V. Emeline ◽  
Jincai Zhao ◽  
Hisao Hidaka ◽  
Vladimir K. Ryabchuk ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Visible Region ◽  
Heterogeneous Photocatalysis ◽  
Quantum Yields ◽  
Yield Data ◽  
Normal Absorption ◽  
The One ◽  
Solid Liquid ◽  
Photonic Efficiency

In the preceding article [Serpone and Salinaro, Pure Appl. Chem., 71(2), 303-320 (1999)] we examined two principal features of heterogeneous photocatalysis that demanded scrutiny: (i) description of photocatalysis and (ii) description of process efficiencies. For the latter we proposed a protocol relative photonic efficiency which could subsequently be converted to quantum yields. A difficulty in expressing a quantum yield in heterogeneous photochemistry is the very nature of the system, either solid/liquid or solid/gas, which places severe restrictions on measurement of the photon flow absorbed by the light harvesting component, herein the photocatalyst TiO2, owing to non-negligible scattering by the particulates. It was imperative therefore to examine the extent of this problem. Extinction and absorption spectra of TiO2 dispersions were determined at low titania loadings by normal absorption spectroscopy and by an integrated sphere method, respectively, to assess the extent of light scattering. The method is compared to the one reported by Grela et al. [J. Phys. Chem., 100, 16940 (1996)] who used a polynomial extrapolation of the light scattered in the visible region into the UV region where TiO2 absorbs significantly. This extrapolation underestimates the scattering component present in the extinction spectra, and will no doubt affect the accuracy of the quantum yield data. Further, we report additional details in assessing limiting photonic efficiencies and quantum yields in heterogeneous photocatalysis.

scholarly journals Bis[Pyrrolyl Ru(II)] Triads: a New Class of Photosensitizers for Metal-Organic Photodynamic Therapy

2020 ◽  
Author(s):  
Deborah A. Smithen ◽  
Susan Monro ◽  
Mitch Pinto ◽  
John A. Roque III ◽  
Roberto M. Diaz-Rodriguez ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Visible Light ◽  
Red Light ◽  
Visible Region ◽  
Hl60 Cell ◽  
Quantum Yields ◽  
Human Leukemia ◽  
New Family ◽  
Hl60 Cell Line

A new family of ten dinuclear Ru(II) complexes based on the bis[pyrrolyl Ru(II)] triad scaffold, where two Ru(bpy)<sub>2</sub> centers are separated by a variety of organic linkers, was prepared to evaluate the influence of the organic chromophore on the spectroscopic and in vitro photodynamic therapy (PDT) properties of the compounds. The bis[pyrrolyl Ru(II)] triads absorbed strongly throughout the visible region, with several members having molar extinction coefficients (e) ≥10<sup>4</sup> at 600–620 nm and longer. Phosphorescence quantum yields were generally less than 0.1% and in some cases undetectable. The singlet oxygen quantum yields ranged from 5% to 77% and generally correlated with their photocytotoxicities toward human leukemia (HL-60) cells regardless of the wavelength of light used. Dark cytotoxicities varied ten-fold, with EC<sub>50</sub> values in the range of 10–100 µM and phototherapeutic indices (PIs) as large as 5,400 and 260 with broadband visible (28 J cm<sup>-2</sup>, 7.8 mW cm<sup>-2</sup>) and 625-nm red (100 J cm<sup>-2</sup>, 42 mW cm<sup>-2</sup>) light, respectively. The bis[pyrrolyl Ru(II)] triad with a pyrenyl linker (5h) was especially potent, with an EC50 value of 1 nM and PI >27,000 with visible light and subnanomolar activity with 625-nm light (100 J cm<sup>-2</sup>, 28 mW cm<sup>-2</sup>). The lead compound 5h was also tested in a tumor spheroid assay using the HL60 cell line and exhibited greater photocytotoxcicity in this more resistant model (EC<sub>50</sub>=60 nM and PI>1,200 with 625-nm light) despite a lower dark cytotoxicity. The in vitro PDT effects of 5h extended to bacteria, where submicromolar EC<sub>50</sub> values and PIs >300 against <i>S. mutans</i> and <i>S. aureus </i>were obtained with visible light. This activity was attenuated with 625-nm red light, but PIs were still near 50. The ligand-localized <sup>3</sup>ππ* state contributed by the pyrenyl linker of 5h likely plays a key role in its phototoxic effects toward cancer cells and bacteria.<br><br>

scholarly journals Synthesis of New Antibiotics Derivatives by the Photocatalytic Method: A Screening Research

Catalysts ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1102
Author(s):  
Wojciech Baran ◽  
Ewa Masternak ◽  
Dominika Sapińska ◽  
Andrzej Sobczak ◽  
Ewa Adamek
Keyword(s):  
Quantum Yield ◽  
Biologically Active ◽  
Quantum Yields ◽  
Photocatalytic Process ◽  
Experimental Conditions ◽  
New Antibiotics ◽  
Photocatalytic Reactions ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Uva Radiation

The aim of our study was to assess the possibility of using the photocatalytic process conducted in the presence of TiO2 to obtain new stable derivatives of antibacterial drugs. The possibility of introducing hydroxyl, chlorine, or bromide groups into antibiotics molecules was investigated. The experiments were conducted in aqueous solutions in the presence of TiO2-P25 as a photocatalyst, Cl− and Br- ions, and antibiotics belonging to eight different chemical classes. All experiments were initiated by UVa radiation. The kinetics of photocatalytic reactions and their quantum yield were determined, and the stable products were identified. All of the antibiotics used in the experiments underwent a photocatalytic transformation, and the quantum yields were in the range from 0.63 to 22.3%. The presence of Br- or FeCl3 significantly increased the efficiency of the photocatalytic process performed in the presence of TiO2, although Br- ion also acted as an inhibitor. Potentially biologically active chlorine derivatives from Trimethoprim, Metronidazole, Chloramphenicol, and bromine derivatives from Trimethoprim, Amoxicillin were obtained under experimental conditions. The potentially inactive halogen derivatives of Sulfamethoxazole and hydroxyl derivatives described in the literature were also identified.

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