| 1. |
- Ruseckas, Arvydas, et al.
(author)
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Luminescence quenching by inter-chain aggregates in substituted polythiophenes
- 2001
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - 1873-2666 .- 1010-6030. ; 144:1, s. 3-12
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Journal article (peer-reviewed)abstract
- Time-resolved photo luminescence spectra measured in solid films of two polythiophene derivatives with different chain packing allow to distinguish emission of intra-chain excitations from the luminescence of inter-chain aggregates. Aggregate luminescence is red shifted by about 0.1 eV relative to intra-chain emission and shows vibronic coupling to the C=C bond stretch with the Huang-Phys factor of S approximate to 1.5, which is twice bigger than that of the intra-chain emission. Combining time resolved luminescence data with femtosecond transient absorption, we show that the dynamic quenching of the luminescence in films with dense chain packing is mainly due to excitation energy transfer to aggregates. The radiative lifetime of the lowest excited state of the aggregate with the optical gap of 1.84-1.9 eV is estimated to be about 20 ns. The aggregate contribution to the total luminescence in the polythiophene films with dense chain packing is about 50% and does not change significantly with temperature. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 2. |
- Beermann, N., et al.
(author)
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Trapping of electrons in nanostructured TiO2 studied by photocurrent transients
- 2002
-
In: Journal of Photochemistry and Photobiology A. - 1010-6030 .- 1873-2666. ; 152:03-jan, s. 213-218
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Journal article (peer-reviewed)abstract
- The electron transport in nanostructured TiO2 has been investigated in an electrochemical system using laser flash induced photocurrent transient measurements with additional continuous monochromatic bias light. Significant effects are found on the photocurrent transient depending on the wavelength of the bias light (360-480 nm). The electron transport time is shorter and the total collected charge is higher when the bias light is in the UV region, while increased transport times and a decreased charge is found with visible light bias. These effects can be explained by trap filling by the UV bias light in the first case and by emptying of traps by visible bias light in the latter.
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| 3. |
- Boschloo, Gerrit, et al.
(author)
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Optimization of dye-sensitized solar cells prepared by compression method
- 2002
-
In: Journal of Photochemistry and Photobiology A. - 1010-6030 .- 1873-2666. ; 148:03-jan, s. 11-15
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Journal article (peer-reviewed)abstract
- Nanostructured TiO2 films have been deposited onto conducting glass and on flexible conducting plastic substrates using a compression technique. Dye-sensitized solar cells prepared from Degussa P25 TiO2 powder, red dye (Ru(dcbpy)(2)(SCN)(2)) or black dye (Ru(tcterpy)(SCN)(3)) and an electrolyte containing LiI and I-2 in 3-methoxypropionitrile were tested using standard photoelectrochemical techniques. The average overall efficiency of small open cells sensitized with the red dye on plastic substrates was 4.5% (100W m(-2)). In a direct comparison, red and black dye gave about the same efficiencies. For both dyes, addition of 4-tert-butylpyridine to the electrolyte resulted in a decreased IPCE response in the whole spectral range, with a specific decrease in the red region, which is attributed to a shift in the conduction band edge of the nano structured TiO2.
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| 4. |
- Keis, K., et al.
(author)
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Nanostructured ZnO electrodes for dye-sensitized solar cell applications
- 2002
-
In: Journal of Photochemistry and Photobiology A. - 1010-6030 .- 1873-2666. ; 148:03-jan, s. 57-64
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Journal article (peer-reviewed)abstract
- Dye-sensitized photoelectrochemical solar cells constitute a promising candidate in the search for cost-effective and environment-friendly solar cells. The most extensively studied, and to date the most efficient systems are based on titanium dioxide. In this paper, the possibilities to use nanostructured ZnO electrodes in photoelectrochemical solar cells are investigated. Various experimental techniques (e.g. infrared, photoelectron, femtosecond and nanosecond laser spectroscopies, laser flash induced photocurrent transient measurements, two and three-electrode photoelectrochemical measurements) show that the thermodynamics, kinetics and charge transport properties are comparable for ZnO and TiO2. The preparation techniques of ZnO provide more possibilities of varying the particle size and shape compared to TiO2. However, the dye-sensitization process is more complex in case of ZnO and care needs to be taken to achieve an optimal performance of the solar cell.
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| 5. |
- Abiodun Daramola, Olamide, et al.
(author)
-
Biocompatible liposome and chitosan-coated CdTe/CdSe/ZnSe multi-core-multi-shell fluorescent nanoprobe for biomedical applications
- 2024
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier. - 1010-6030 .- 1873-2666. ; 454
-
Journal article (peer-reviewed)abstract
- Cadmium telluride (CdTe) semiconductor quantum dots (QDs) are brightly luminescent nanocrystals that have emerged as a new class of fluorescent probes for in vivo bioimaging and theranostic applications. CdTe QDs toxicity to normal human cells is minimized by coating with a less toxic ZnS and ZnSe shell forming a core–shell nanostructure. However, coating with ZnS or ZnSe shell is insufficient to prevent the leaching of toxic Cd metal ions. To further minimize toxicity, thiol dual capped CdTe/CdSe/ZnSe multi-core-multi-shell quantum dots were coated with nanoliposome or liposome vesicles (CdTe/CdSe/ZnSe@liposome) and chitosan nanoparticles (CdTe/CdSe/ZnSe@ChitNPs) and their biocompatibility on HeLa and Vero cells were investigated. Different spectroscopic and microscopic techniques were used to elucidate nanocomposites' optical, morphological, and physicochemical properties. The coating of CdTe/CdSe/ZnSe multi-core-multi-shell quantum dots were conducted at different formulations (F1, F2 and F3) and results from the fluorescence studies show that F3 demonstrated the best interaction for both liposome and ChitNPs composite. Exposure to 12 h UV illumination studies also reveals that CdTe/CdSe/ZnSe@liposome shows an enhancement in fluorescence compared to CdTe/CdSe/ZnSe@ChitNPs. The cytotoxicity of the formulations towards HeLa and Vero cells also depicted minimal toxicity compared to CdTe/CdSe/ZnSe QDs that shows much higher toxicity (IC50 = 0.09381 mg/ml). It was further observed that liposome coated multi-core-multi-shell QDs@F2 demonstrated lower toxicity (IC50 = 0.4364 mg/ml) compared to ChitNPs coated multi-core-multi-shell QDs@F2 (IC50 = 0.1618 mg/ml). Results from the florescence imaging studies reveal that CdTe/CdSe/ZnSe-multi-core-multi-shell QDs liposomes and ChitNPs composite retained most of their fluorescence and properties and could easily be tracked in cells and visualized around the nucleus. This indicates the successful internalization of the QDs in the cytosol. Therefore, these results shows that coating CdTe multi-core-mutli-shell QDs with liposomes and ChitNPs produce better biocompatibility compared to uncoated multi-core–shell QDs. However, liposome coated CdTe/CdSe/ZnSe multi-core-multi-shell quantum dots show better optical properties, photostability and biocompatibility compared to CdTe/CdSe/ZnSe multi-core-multi-shell quantum dots with ChitNPs coating. These particles therefore show good promise in cell-labelling and drug delivery studies.
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| 6. |
- Abrahamsson, Maria, et al.
(author)
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Meta-substituted Ru(II) rigid rods for sensitization of TiO(2)
- 2009
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 206:2-3, s. 155-163
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Journal article (peer-reviewed)abstract
- Abstract in Undetermined Ruthenium polypyridyl rigid-rod compounds with phenylene-ethynelene (OPE) spacers and an isophthalic acid (Ipa) binding group were synthesized and characterized for sensitization of nanocrystalline TiO(2) (anatase) thin films. Density functional theory predicted that the most stable structure oriented the isophthalic group about 45 degrees from normal to the TiO(2) surface. Comparative experimental studies of meta- and para-isomers revealed small changes in the ground state absorption spectra and very similar excited state and redox properties. The excited state injection yields (inj = 0.15 +/- 0.03)into nanocrystalline TiO(2) and the subsequent charge recombination rates were found to be insensitive to the isomer utilized. Meta-substitution enabled the synthesis of sensitizers with two Ru(II) sensitizers that displayed enhanced sunlight absorption relative to the monomeric compound.
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| 7. |
- Ahmad, Tausif, et al.
(author)
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Controllable phytosynthesis of gold nanoparticles and investigation of their size and morphology-dependent photocatalytic activity under visible light
- 2020
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier. - 1010-6030 .- 1873-2666. ; 392, s. 1-11
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Journal article (peer-reviewed)abstract
- Plants mediated synthesis of gold nanoparticles (AuNPs) containing desired characteristics for their suitable potential applications has been a challenging task, which is causing a major hindrance towards its commercialization. Therefore, herein phytosynthesis of AuNPs with required size and morphology has been achieved through manipulating the reaction conditions including reaction temperature and volume of Elaeis guineensis leaves (EGL) extract. Furthermore, photocatalytic potential of EGL mediated AuNPs having different size and shape has also been explored for the removal of methylene blue (MB) under visible light irradiation. The reaction temperature and volume of EGL strongly influenced the size and morphology of AuNPs, which are directly associated with the photocatalytic activities. The experimental results revealed that predominantly spherical and ultra-smaller size AuNPs with particle size of 16.26 ± 5.84 nm, formed at 70 °C showed the highest removal efficiency up to 92.55 % in 60 min. This highest photocatalytic activity of AuNPs could be attributed to the availability of higher number of low-coordinated gold (Au) atoms in the MB aqueous solution, which might have boosted the adsorption of the MB on the surface of particles and accelerated the degradation phenomenon. The proposed photocatalytic degradation mechanism of AuNPs for MB was also explained. The highly photoactive EGL mediated AuNPs with controllable morphology and size could be an advance step in future in chemical and biomedical applications.
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| 8. |
- Aung, Su Htike, et al.
(author)
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Kinetic study of carminic acid and santalin natural dyes in dye-sensitized solar cells
- 2016
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 325, s. 1-8
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Journal article (peer-reviewed)abstract
- The performance of natural dyes in dye-sensitized solar cells is usually worse than that of purpose-built organic dyes. Here, we set out to investigate the underlying origins. Two natural dyes, carminic acid and santalin, were selected as potential sensitizers for dye-sensitized solar cells. They were compared to a state-of-the-art organic sensitizer, LEG4, in devices using relatively thin (5 mu m), transparent mesoporous TiO2 electrodes and iodide/triiodide redox electrolyte in the low-volatile solvent 3-methoxypropionitrile. All dyes adsorbed well onto mesoporous TiO2 electrodes, giving it bright red colors. The power conversion efficiency of the natural dyes, about 0.5%, was poor compared to that of LEG4 under identical conditions (5.6%), due to both lower open circuit potentials and photocurrent densities. The origin of low efficiencies was investigated using a wide range of experimental techniques, such as (spectro)electrochemistry, ns-laser transient absorption spectroscopy and transient photocurrent and photovoltage measurements. The kinetics for regeneration of the oxidized natural dyes by iodide was found to about ten times slower than that of LEG4. This is probably due to the lower driving force for this reaction. Significant electron recombination to oxidized dye molecules and possibly poor electron injection efficiency caused the poor performance of the two natural dyes in dye-sensitized solar cells. In addition, for carminic acid electron injection into the conduction band of TiO2 appears to be poor. (C) 2016 Published by Elsevier B.V.
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| 9. |
- Bauer, C, et al.
(author)
-
Photooxidation of an azo dye induced by visible light incident on the surface of TiO2
- 2001
-
In: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY. - : ELSEVIER SCIENCE SA. - 1010-6030. ; 140:1, s. 87-92
-
Journal article (peer-reviewed)abstract
- Oxidation of Acid Orange 7 (AO7) induced by visible light on TiO2 surfaces has been probed by FT-IR spectroscopy for identification and kinetic studies of degradation products. The tautomerism has been considered for this type of azo dye. The hydrazone fo
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| 10. |
- Boonyavong, Narumon, et al.
(author)
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Synthesis, electrochemistry and photo-induced electron transfer of unsymmetrical dinuclear ruthenium osmium 2,2 '-bipyridine complexes
- 2014
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 287, s. 40-48
-
Journal article (peer-reviewed)abstract
- Four unsymmetric dinuclear ruthenium and osmium complexes, Os(bpy)(3)-viologen-Ru(bpy)(3) (1; bpy= 2,2'-bipyridyl), Ru(bpy)(3)-viologen-Ru(bpy)(dcbpy)(2) (2; dcbpy= 4,4'-dicarboxy1-2,2-bipyridyl), Os(bpy)(3)-viologen-Ru(bpy)(dcbpy)(2) (3) and rotaxane 1 subset of CB[7] (CB[7] = cucurbit[7]uril), were successfully synthesized. The NMR, electrochemistry and photochemistry studies of these complexes were performed in non-aqueous solutions. The results show that the CB[7] host mainly locates at the butyl linker part of the osmium side in an acetonitrile solution. This binding lowers the oxidation potential of osmium whereas the oxidation potential of ruthenium does not change. The oxidation potential of ruthenium in complexes 2 and 3 is higher due to the electron withdrawing property of carboxylic anchor groups. Analysis with UV-vis spectra shows the viologen radical formation and reversed process of these complexes in non-aqueous solutions.
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| 11. |
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| 12. |
- Brüggemann, Ben, et al.
(author)
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Laser pulse control of exciton dynamics in a biological
- 2007
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 190:2-3, s. 372-377
-
Journal article (peer-reviewed)abstract
- Femtosecond laser pulse control of exciton dynamics in a biological chromophore complex is studied theoretically. The computations use the optimal control theory specified to open quantum systems and formulated in the framework of the rotating wave approximation. Based on the laser pulse induced formation of an excitonic wave packet the possibility to localize excitation energy at a certain chromophore within a photosynthetic antenna system (FMO complex of green bacteria) is investigated. Details of exciton dynamics driven by a polarization shaped pulse are discussed. (c) 2007 Elsevier B.V. All rights reserved.
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| 13. |
- Brüggemann, Ben, et al.
(author)
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Laser pulse control of exciton dynamics in the FMO complex: Polarization shaping versus effects of structural and energetic disorder
- 2006
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 180:3, s. 322-327
-
Journal article (peer-reviewed)abstract
- Femtosecond laser pulse control of exciton dynamics in biological chromophore complexes is studied theoretically using the optimal control theory specified to open quantum systems. Based on the laser pulse induced formation of an excitonic wave packet the possibility to localize excitation energy at a certain chromophore within a photosynthetic antenna system (FMO complex of green bacteria) is investigated both for linearly polarized and polarization shaped pulses. Results are presented for an ensemble of N energetically disordered and randomly oriented FMO complexes. Here, the optimized control pulse represents a compromise with respect to the solution of the control task for any individual complex of the ensemble. For the case of an ensemble with N = 10 members the polarization shaped control pulse leads to a higher control yield compared with a linearly polarized pulse. This difference becomes considerably smaller for an ensemble with N = 120 members. The respective optimized pulses are used to drive excitation energy in a different ensemble with M >> N complexes to simulate the usual experimental condition in solution. For the case with N = 120, the relative control yield coincides with the resulting control yield "in solution", giving a slightly higher control yield for polarization shaped pulses. (c) 2006 Elsevier B.V. All rights reserved.
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| 14. |
- Buyukeksi, Sebile Isik, et al.
(author)
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Electron/energy transfer studies on hybrid materials based on dinuclear coordination compounds of twisted perylene diimide
- 2019
-
In: Journal of Photochemistry and Photobiology A: Chemistry. - : Elsevier BV. - 1010-6030. ; 372, s. 226-234
-
Journal article (peer-reviewed)abstract
- To understand the influence of transition metal ion coordination on the properties and performance of the triads, the symmetric bridging ligand, 1,10-phenanthroline-perylene diimide-1,10-phenanthroline, 1,10-Phen-PDI-1,10-Phen (1) comprising four electron-donating 4-methoxyphenoxy bulky groups at bay-positions and its corresponding square-planar coordination compounds with dichloroplatinum(II), [{PtCl2}(2)-1] (2) and palladium(II) [{PdCl2}(2)-1] (3) were prepared in order to tune the photochemical and optical properties of these hybrid materials. These triads show strong electronic absorption bands attributed to the PDI and M(II)(1,10-Phen)Cl-2 moieties in DMSO. UV-vis absorption spectra of the compounds were calculated using Time-Dependent Density Functional Theory (TDDFT) for the ground state optimized structures in DCM. Current results indicate that 2 has the lowest HOMO-LUMO gap (2.29 eV in DCM) among the investigated molecules. The energy and charge transfer processes with tailoring molecular structures are one of the important strategies for the design of future functional triads based on donor and acceptor moieties for hybrids optoelectronic devices. Thus, we studied linear absorption, fluorescence, and ultrafast transient absorption spectra measurements for the triads in DCM to investigate the impact of different functionalization strategies on the optical characteristics, photo-stability, and photo-induced charge-transfer (CT) processes. The observed ultrafast intramolecular charge transfer from donor units to acceptor part of 1-3 is related to fluorescence quenching and faster singlet state decay on transient absorption measurements. The intramolecular charge transfer mechanism was also compared with the unsymmetrical counterparts that were investigated previously. Symmetrical compounds exhibit faster charge transfer in comparison with the unsymmetrical compounds.
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| 15. |
- Chen, Ruikui, et al.
(author)
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Tetrahydroquinoline dyes with different spacers for organic dye-sensitized solar cells
- 2007
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 189:03-feb, s. 295-300
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Journal article (peer-reviewed)abstract
- Novel organic dyes (C1-1, C1-5 and C2-1) with a tetrahydroquinoline moiety as the electron donor, different thiophene-containing electron spacers and a cyanoacrylic acid moiety as the electron acceptor have been designed and synthesized for the application in dye-sensitized solar cells (DSSCs). An interesting relationship between the dye structures, properties, and the performance of DSSCs based on these tetrahydroquinoline dyes is obtained. Although C2-1 dye, which has a rigid electron spacer, has the narrowest action spectrum among these dyes, it gives the highest solar-to-electricity conversion efficiency (eta) of 4.49% (V-oc = 600 mV, J(sc) = 11.20 mA/cm(2), ff = 0.67) of a DSSC under simulated AM 1.5 irradiation (100 mW/cm(2)). Under the same conditions, the eta value of a DSSC based on N3 dye is 6.16%.
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| 16. |
- Delices, Annette, et al.
(author)
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Experimental and theoretical study of organic sensitizers for solid-state dye-sensitized solar cells (s-DSSCs)
- 2022
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier. - 1010-6030 .- 1873-2666. ; 428
-
Journal article (peer-reviewed)abstract
- The effect of a series of triarylamine based D-pi-A organic dyes, namely RK1, BA504, BA741 and the simple L1 reference dye on solid-state dye sensitized solar cells (s-DSSCs) performances was studied. The solid hole transporting material (HTM) was obtained by in-situ photoelectrochemical polymerization (in-situ PEP) process applied in two different media (water and acetonitrile) to produce the poly-3,4 ethylenedioxythiophene (PEDOT) conducting polymer (CP). A joint experimental and theoretical (density functional theory and time-dependent density functional theory) study is conducted to correlate the dye molecular structure containing different donor, pi-bridge or acceptor with several physicochemical characteristics such as optical (absorption and emission), electronic and redox properties of dyes in organic and aqueous medium; in-situ PEP process and charge transfer kinetics at the DSSC interfaces (Dye/TiO2 and Dye/HTM) through the alignment of the different energy levels of the dyes and electrodes. These properties are considered since they govern the performance of s-DSSCs denoted by the short-circuit current (J(sc)), open circuit cell potential (V-oc) and fill factor (FF). Among the four studied dyes, the s-DSSCs based on RK1, shows the best power conversion efficiency of 1.75% resulting from highest FF (0.57), V-oc (550 mV) and J(sc) (5.6 mA/cm(2)). The large differences in experimental photovoltaic performances of the obtained s-DSSCs have been well outlined and provide the guidelines for future development of more efficient solar-cell sensitizers.
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| 17. |
- Di Mauro, Alessandro, et al.
(author)
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Visible Light Photodegradation of Dyes and Paracetamol by Direct Sensitization Mechanism onto Metallic MoO2 Nanocrystals
- 2021
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier. - 1010-6030 .- 1873-2666. ; 413
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Journal article (peer-reviewed)abstract
- MoO2 nanocrystals were prepared by solvothermal treatment of a Mo chloromethoxide at 250 °C in oleic acid. The monoclinic MoO2 phase, with a mean crystallite size of 29 nm, formed through reduction of molybdenum bronzes. The as-prepared MoO2 nanocrystals were free from organics, allowing their use in photodegradation tests of organic pollutants (methylene blue, rhodamine B, paracetamol), without any preliminary purification treatment of the nanocrystals. It was found that MoO2 was an efficient adsorbent of methylene blue (43 mg g-1 for 1.5 × 10−4 M concentration) in the dark and an efficient photodegradation catalyst under visible light (all methylene blue removed from the solution after 240 min). From the analysis of the combined photodegradation tests of rhodamine B and paracetamol, it was clarified that direct sensitization was responsible for photodegradation. This finding was related to the work function value of metallic MoO2, placed at more negative values if compared with other metallic materials.
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| 18. |
- Dissanayake, M. A. K. L., et al.
(author)
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A novel multilayered photoelectrode with nitrogen doped TiO2 for efficiency enhancement in dye sensitized solar cells
- 2017
-
In: Journal of Photochemistry and Photobiology A: Chemistry. - : Elsevier BV. - 1010-6030. ; 349, s. 63-72
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Journal article (peer-reviewed)abstract
- Nitrogen doped TiO2 powder samples were synthesized by a modified wet chemical method using aqueous ammonia and nitrogen gas purged on titanium tetra isopropoxide (TTIP). Photolectrodes with different combinations of layers of nitrogen − doped TiO2, undoped TiO2 and Degussa P25 TiO2 powders were used in dye sensitized solar cells (DSSCs). The highest conversion efficiency of 8.00% was achieved by the cells fabricated with compact layer/P25/N-doped TiO2 multilayer photoelectrode. This is an impressive enhancement in efficiency close to 89% with respect to a similar multilayer electrode made with undoped TiO2 which showed a conversion efficiency of 4.22%. The enhancement in the efficiency appears to be due to the increased photocurrent density of the DSSCs resulting mainly from energy band gap narrowing due to N-doping with some contribution from increased dye uptake by the novel multilayer electrode. These results have been substantiated by the reduced charge transfer resistance obtained from Electrochemical Impedance Spectra and the enhanced IPCE spectra of the DSSCs with N-doped TiO2 based multilayer electrode. © 2017 Elsevier B.V.
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| 19. |
- Dissanayake, M.A.K.L., et al.
(author)
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Efficiency enhancement by mixed cation effect in dye-sensitized solar cells with PAN based gel polymer electrolyte
- 2012
-
In: Journal of Photochemistry and Photobiology A: Chemistry. - : Elsevier BV. - 1010-6030. ; 246, s. 29-35
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Journal article (peer-reviewed)abstract
- Dye-sensitized solar cells based on nano-porous TiO2 photo-anode and quasi-solid polymer (or gel) electrolytes are emerging as low cost alternatives to conventional inorganic photovoltaic devices. Although many attempts have been made in order to improve the relatively low power conversion efficiencies of these solar cells, to our knowledge there are very few reports aimed at using a binary system of two different iodide salts toward efficiency enhancement in these cells. In this paper we report for the first time in detail, the effect of using a binary iodide salt mixture with different size cations on the efficiency enhancement in dye sensitized solar cells with polyacrylonitrile (PAN) based gel polymer electrolyte and suggest a possible mechanism for this enhancement, based on short circuit photocurrent which is directly related to the iodide ion concentration [I-]. The gel electrolyte was made of PAN, ethelene carbonate (EC), Propylene carbonate (PC), salt mixture and I-2. The binary iodide salt mixture consists of potassium iodide (KI) and Tetra propyl ammonium iodide (Pr4NI). Although the gel electrolyte with 100% (w/w) KI exhibited the highest overall ionic conductivity at room temperature, it showed the lowest iodide ion (I-) contribution to conductivity. On the other hand, the electrolyte with 100% (w/w) Pr4NI exhibited the lowest overall ionic conductivity but had the highest iodide ion(I-) contribution. The dye-sensitized solar cells of configuration Glass/FTO/TiO2/N-719 Dye/electrolyte/Pt/FTO/glass were fabricated using the gel electrolytes of different salt ratios and with nanoporous TiO2 electrode sensitized with Ruthenium dye (N719). With identical electrolyte compositions, the solar cell with 100% (w/w) KI showed an efficiency of 4.98% and the cell with 100% (w/w) Pr4NI showed an efficiency of 4.47%. However, the cell with the mixed iodide system, 16.6% (w/w) KI + 83.4%(w/w) Pr4NI showed the highest efficiency of 5.36% with maximum short circuit current density (J(SC)) of 13.79 mA cm(-2), open circuit voltage (V-OC) of 679.10 mV and a fill factor of 57.25%. The variation of efficiency (eta) with iodide ion concentration [I-] follows the same trend as the J(SC) which appears to be governed by the iodide ion conductivity of the gel electrolyte. The dependence of the short circuit photocurrent and the open circuit photovoltage on the cation type generally agrees with reported data for related systems. However, the occurrence of a maximum in the solar cell efficiency and short circuit photocurrent at 16.6% (w/w)10 + 83.4% (w/w) Pr4NI salt composition is an important finding. The efficiency enhancement of about 8% achieved by employing the binary iodide mixture in the gel electrolyte instead of a single iodide salt, could be utilized for achieving efficiency enhancement in many dye sensitized solar cell systems based on polymeric, gel or solvent electrolytes.
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| 20. |
- Dissanayake, Makl, et al.
(author)
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Solid-state solar cells co-sensitized with PbS/CdS quantum dots and N719 dye and based on solid polymer electrolyte with binary cations and nanofillers
- 2021
-
In: Journal of Photochemistry and Photobiology a-Chemistry. - : Elsevier BV. - 1010-6030. ; 405
-
Journal article (peer-reviewed)abstract
- Co-sensitized solar cells have gained more attention due to the ability of energy conversion process by absorbing photons from wide range of the solar spectrum including visible and near-infrared region. TiO2 electrodes were co-sensitized with PbS/CdS core-shell quantum dots and N719 dye. PbS/CdS/N719 dye-sensitized solar cells were fabricated with poly(ethylene oxide) based solid polymer electrolyte consisting iodide/triiodide redox couple. The iodide ion conductivity of the electrolyte was enhanced by incorporating a binary iodide salt mixture of different size cations, tetrapropylammonium iodide and potassium iodide. The performance of the solar cell was further enhanced by the incorporating TiO2 P90 nanofiller in the electrolyte. The best solid-state solar cell showed a significantly higher efficiency of 4.41 % with a short-circuit current density of 8.41 mA cm(-2), open circuit voltage of 748.3 mV and a high fill factor of 70.16 % under the simulated light of 100 mW cm(-2) with AM 1.5 filter. This is the first report describing the efficiency enhancement in a solid-state dye sensitized solar cell based on a solid polymer electrolyte incorporating a binary cation iodide salt and TiO2 nanofiller and a photoanode co-sensitized with PbS/CdS quantum dots and N719 dye demonstrating the cumulative effect by the mixed cation effect and co-sensitization.
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| 21. |
- Durbeej, Bo, et al.
(author)
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Reaction mechanism of thymine dimer formation in DNA induced by UV light
- 2002
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier. - 1010-6030 .- 1873-2666. ; 152:1-3, s. 95-101
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Journal article (peer-reviewed)abstract
- The formation of thymine dimers in DNA is investigated by means of density functional theory (DFT) techniques. While it is found that a thermally induced [2 + 2] cycloaddition reaction proceeds via a very high energy transition state (80–88 kcal/mol above the reactant complex), the energy barrier for UV light induced formation – explored within the time-dependent DFT formalism – is only a few kilocalories per mol. As such, these results serve as an illustrative example of how UV radiation may induce DNA lesions. For the reactant complex, the calculated vertical excitation energy corresponding to the S1 S0 transition ( *) lies in the far-UV region, in accordance with experimental data.
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| 22. |
- Fernandes, Daniel L. A., et al.
(author)
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Novel photo-reactor for fast screening of photo-catalytic systems
- 2017
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 335, s. 36-39
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Journal article (peer-reviewed)abstract
- Photo-catalysis is an emerging technology for clean energy production, organic synthesis and environmental protection, etc. While there is a hydrogen of systems and schemes to attain these objectives, there is a paucity of photo-reactors capable of determine catalytic abilities in real time with reduce amounts of samples, i.e., fast-screening of catalyst and reaction parameters. Herein, we report a novel photo-reactor for simultaneous online monitoring of gaseous products with quadrupole mass spectrometry and photo-physics with fibre optic UV/Vis with millisecond time resolution on 4 mL cuvettes.
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| 23. |
- Greijer Agrell, Helena, et al.
(author)
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Coordinative interactions in a dye-sensitized solar cell
- 2004
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In: Journal of Photochemistry and Photobiology A: Chemistry. - : Elsevier BV. ; 164:1-3, s. 23-27
-
Journal article (peer-reviewed)abstract
- Resonance Raman scattering studies of a complete dye-sensitized solar cell (DSC) including iodine and lithium iodide in the electrolyte indicate that triiodide (I3-) exchange the SCN- ligand of the dye bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2'-bipyridine-4-carboxylic acid, 4'-carboxylate)ruthenium(II). The choice of cation in the iodide salt influenced the ligand stability of the dye. It was proposed that an ion pair Li+...I3- formation occurred which by a reduced electrostatic repulsion between I3- and SCN- facilitated the exchange of these anions at Ru(II) of the dye. The additive 1-methylbenzimidazole (MBI) suppressed the SCN /Ij ligand exchange by forming a complex with Li+. The concentrations of Li+ and MBI have to be carefully balanced due to the SCN ligand exchange with the use of characterization methods with which complete devices can be studied is necessary.
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| 24. |
- Guo, Wei, et al.
(author)
-
Highly efficient dye-sensitized solar cells based on nitrogen-doped titania with excellent stability
- 2011
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 219:2-3, s. 180-187
-
Journal article (peer-reviewed)abstract
- A series of nitrogen-doped and undoped TiO2 nanocrystals was prepared by several simple methods. Needle-like N-doped TiO2 nanocrystals and nanoparticles were obtained from commercial TiO2 powders. Several dye-sensitized solar cells (DSCs) were fabricated based on N-doped and undoped TiO2 electrodes. The N-doped DSCs achieved a high conversion efficiency of 10.1% and 4.8% using an organic electrolyte and an ionic liquid electrolyte, respectively. Systemic investigations were carried out on the properties of N-doped and undoped TiO2 powders, films, and DSCs. The electron transport time and electron lifetime were investigated by intensity-modulated photocurrent and photovoltage spectroscopy (IMPS/IMVS). Moreover, the electron injection of N-doped DSCs was studied by surface photovoltage spectroscopy (SPS). The synergetic effect of higher dye uptake, faster electron transport and higher photovoltage contributes to a higher conversion efficiency of N-doped DSCs. The stability test also demonstrated that the photodegradation of the DSCs was not accelerated and the DSC system was stabilized by the introduction of nitrogen into the TiO2 photoelectrode. These results indicate that the N-doped TiO2 nanocrystals prepared by our approach from commercial TiO2 are ideal semiconductor materials for DSCs.
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| 25. |
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| 26. |
- Jonstrup, Maria, et al.
(author)
-
Comparison of anaerobic pre-treatment and aerobic post-treatment coupled to photo-Fenton oxidation for degradation of azo dyes
- 2011
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 224:1, s. 55-61
-
Journal article (peer-reviewed)abstract
- Photo-Fenton oxidation was used for treatment of synthetic textile wastewater as stand alone treatment, as pre-treatment before aerobic biological treatment and as post-treatment after anaerobic biological treatment. The processes were compared with regards to decolorization, chemical oxygen demand (COD) reduction and chemical consumption. When applying photo-Fenton alone for treatment of Remazol Red RR (100 mg/l), optimal conditions were 3.0 mM H2O2 and 0.25 mM Fe2+. These conditions resulted in complete decolorization and a residual COD of 2.9 mg/l. When reducing the H2O2 dose to 1 mM, residual COD was 22 mg/l. In the combined photo-Fenton/aerobic treatment complete decolorization and COD removal was achieved at 3 mM H2O2 and 0.25 mM Fe2+, while 9 mg/l of residual COD remained at the H2O2 concentration 1 mM. When applying photo-Fenton as post-treatment after the anaerobic step, the residual COD was 14 mg/l independent of the H2O2 concentration being set to 1 or 3 mM, however the Fe2+ concentration needed to be increased to 2 mM, due to complex formation with the phosphate added as a macronutrient. Phytotoxicity tests showed higher residual toxicity after the photo-Fenton treatment alone than after the combined processes. Our results thereby show that incorporation of a biological step leads to improved mineralization and reduced residual toxicity at lower H2O2 doses. (C) 2011 Elsevier B.V. All rights reserved.
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| 27. |
- Karlsson, Daniel, et al.
(author)
-
Photodissociation of bromochlorobenzenes
- 2008
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 195:2-3, s. 242-246
-
Journal article (peer-reviewed)abstract
- The photodissociation kinetics of 2-, 3- and 4-bromochlorobenzene (BrClPh) and bromo-3,5-dichlorobenzene (Br-diClPh) have been studied in a molecular beam following excitation at 270 nm using femtosecond pump-probe spectroscopy. The kinetics and the dissociation dynamics in the BrClPhs were found to resemble the BrFPhs much more than the BrBrPhs. In 2- and 3-BrClPh two dissociation channels were observed, whereas 4-BrCIPh and Br-3,5-diClPh dissociates via only one channel. The time constant for channel one, present in all molecules, depends on the number of chlorine atoms and their position. The absence of a second channel in 4-BrCIPh is a general property among mixed Br-(Br, Cl or F)-Phs and is likely to be due to a dissociation channel involving a triplet excitation.
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| 28. |
- Karlsson, Martin, 1982-, et al.
(author)
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Phenoxazine dyes in solid-state dye-sensitized solar cells
- 2012
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 239, s. 55-59
-
Journal article (peer-reviewed)abstract
- Several structural modifications have been made to a sensitizer dye based on the phenoxazine core. which was tested in a solid-state dye-sensitized solar cell configuration based on the hole transporting material 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9'-spirofluorene. Light-to-power conversion efficiencies between 2.5% and 4.1% are reported herein. The difference in device performance is significantly related to the variations of dye molecular structure, with dye molecules having surface protecting alkoxy-groups yielding better solar cell devices. The phenoxazine dyes were characterized by their light harvesting capabilities and electronic properties such as electron recombination lifetime and chemical dipole moment.
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| 29. |
- Kiselev, A., et al.
(author)
-
Adsorption and photocatalytic degradation of diisopropyl fluorophosphate and dimethyl methylphosphonate over dry and wet rutile TiO2
- 2006
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 184:1-2, s. 125-134
-
Journal article (peer-reviewed)abstract
- Nanosized, crystalline rutile TiO2 was synthesized at room temperature using a microemulsion-mediated system followed by hydrothermal treatment. The formed rutile had a specific surface area of about 40 m(2) g(-1) and the rutile crystals had dimensions of about 10 nm x 150 nm, which aggregated into 200-1000nm sized bundles. The adsorption and photocatalytic degradation of diisopropyl fluorophosphate (DFP) and dimethyl methylphosphonate (DMMP) over these rutile TiO2 nanoparticles in dry and wet synthetic air was investigated by in situ diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy during simulated solar light illumination. The methyl and isopropyl groups do not dissociate upon adsorption on either dry or humidified rutile nanoparticles. The F atom in DFP is, however, easily hydrolyzed and is readily dissociated upon interaction with hydroxyls on the TiO2 surfaces and leads to a destabilization of the DFP molecule. The initial solar light induced photodegradation rate for DFP and DMMP is 5.9 x 10(-4) and 1.0 x 10(-4) s(-1) in dry conditions and 8.1 x 10(-4) and 0.7 x 10(-4) s(-1) in wet conditions (corresponding to 2-3 monolayers (ML) water coverage), respectively. The main intermediate partial oxidation surface products are found to be surface bound formate-carboxylate-carbonate (R-COO-) and phosphate (R-POO-) species. Among them eta(1)-coordinated acetone and mu-formate, bicarbonate, and bidentate R-POO- moieties are detected. These surface species accumulate on the surface during the entire illumination period (60 min), and lead to a decreased total oxidation rate. Controlled humidification of the rutile surface leads to a reduction of the concentration of R-COO- intermediates, while at the same time maintaining approximately the same rate of DFP and DMMP photooxidation. The latter is due to blocking of Ti surface cation sites, which prevents the formation of strongly bonded surface compounds, in particular mu-coordinated R-COO- and R-POO- species. The findings show that, it is possible to optimize the sustained photocatalytic degradation of organic phosphorous compounds by controlled humidification of the reaction gas. (c) 2006 Elsevier B.V. All rights reserved.
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| 30. |
- Kong, Zhixia, et al.
(author)
-
A new class of organic dyes based on acenaphthopyrazine for dye-sensitized solar cells
- 2010
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 213:2-3, s. 152-157
-
Journal article (peer-reviewed)abstract
- A new class of organic dyes based on acenaphthopyrazine derivatives, containing pyrazine group as the electron acceptor and o-dicarboxyl acids as the anchoring groups were designed and synthesized for application in dye-sensitized solar cells (DSCs). These dyes have short synthesis routes and are easily adsorbed on the surface of TiO2. Under illumination of simulated AM1.5 solar light (100 mW cm(-2)), a total solar energy conversion efficiency (eta) of 4.04% was obtained for the 3-(diphenylamino)acenaphtho[1,2-b] pyrazine-8,9-dicarboxylic acid (AP-1) in the preliminary tests, in comparison with the conventional N719 dye (eta=7.05%) under the same conditions.
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| 31. |
- Kumar, Pushpendra, et al.
(author)
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Global analysis of quenching of the time-resolved emission of ZnO nanocrystals by adsorbed rhodamine B on the basis of Tachiya theory
- 2015
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 296, s. 35-39
-
Journal article (peer-reviewed)abstract
- Normally dye molecules are adsorbed onto the nanocrystal (NC) surface in dye-NC mixed solution, but it is very unlikely that all dye molecules present in the solution will be attached to NCs. The distribution of dye molecules on the NC surface is an important factor to take into account while investigating the quenching of NC emission via energy transfer to adsorbed dye molecules. Here, we analysed time-resolved fluorescence data of ZnO NCs in the presence of rhodamine B (RhB) using Tachiya theory, which assumes the Poisson distribution of dye molecules among the NCs. Energy transfer rate from NC to a dye molecule was found to be much faster than the intrinsic fluorescence decay rate of NCs and fluorescence quenching rate due to intrinsic trap states present in the NC. The association constant was also calculated to acquire information on the nature of association of dye molecules with NCs. (C) 2014 Elsevier B.V. All rights reserved.
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| 32. |
- Leandri, Valentina, et al.
(author)
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Incorporation of a fluorophenylene spacer into a highly efficient organic dye for solid-state dye-sensitized solar cells
- 2016
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 328, s. 59-65
-
Journal article (peer-reviewed)abstract
- A new efficient organic dye LEG4F, incorporating a fluorine-substituted phenylene unit in the π-spacer, has been synthesized and tested in dye-sensitized solar cells. Direct comparison with the parent dye LEG4 shows very similar performances in case of liquid electrolyte devices based on iodide/triiodide, yielding a power conversion efficiency of 6.8% under 1 sun and 8.0–8.2% under 0.5 sun illumination. However, LEG4F outperforms its fluorine-free analogue when the liquid electrolyte is replaced by the solid-state hole-transport material Spiro-OMeTAD, reaching 5.3% efficiency compared to 4.8% achieved by LEG4. We show that this improvement is due to the enhancement of the electron lifetime, which reduces recombination at the TiO2/dye/Spiro-OMeTAD interfaces.
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| 33. |
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| 34. |
- Liao, Haidong, et al.
(author)
-
Study of Indigo carmine as radical probe in photocatalysis
- 2009
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 202:2-3, s. 86-91
-
Journal article (peer-reviewed)abstract
- The feasibility of using Indigo carmine (IC) as a probe of free radical production in photocatalysis was elucidated by comparative studies of its bleaching by gamma radiolysis and TiO2 photocatalysis. The gamma radiation result from pH 3 to 10 shows that both (OH)-O-center dot and HO2 center dot can bleach IC and that the bleaching yields of (OH)-O-center dot is pH independent at similar to 0.7 molecules per (OH)-O-center dot. The quantum yields (phi) of (OH)-O-center dot from Degussa p25 TiO2 photocatalysis from pH 3 to 10 was determined. It was found that phi was about 4% at pH 10 and dropped to below 1% at pH 3. This agrees well with the result of photocatalysis of Fricke dosimetry at pH 1. The effects of some common inorganic anions that may affect photocatalytic systems in technical applications (Cl-, SO42-, Br-, HPO42-, B4O72-, HCO3-/CO32-) was also investigated, showing that these ions does not inhibit the photocatalytic bleaching efficiency of IC.
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| 35. |
- Liu, Ya-Jun, et al.
(author)
-
Ab initio investigation on the chemical origin of the firefly bioluminescence
- 2008
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 194, s. 261-267
-
Journal article (peer-reviewed)abstract
- The chemical origin of the firefly bioluminescence has been investigated by means of density functional and multireference theoretical methods. Different hypotheses on the mechanism of multicolour emission have been investigated: twisting around the central carbon–carbon bond, polarizability of the oxyluciferin microenvironment and presence of resonance structures. The calculated results indicated that the higher the polarizability of the microenvironment is, the larger the red shift of the bioluminescence is. Moreover, a quite flat potential energy surface should allow the easy shifting of the anion minimum between different pseudo-resonance structures. The possible effects of a tight or loose protein pocket has also been considered.
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| 36. |
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| 37. |
- Musa, Klefah A.K., et al.
(author)
-
Photochemical and photophysical properties, and photodegradation mechanism, of the non-steroid anti-inflammatory drug Flurbiprofen
- 2009
-
In: Journal of Photochemistry and Photobiology A. - Amsterdam : Elsevier. - 1010-6030 .- 1873-2666. ; 202:1, s. 48-56
-
Journal article (peer-reviewed)abstract
- The photodegradation mechanism of the widely used non-steroidal anti-inflammatory drug 2-(4-phenyl-3-fluorophenyl) propanoic acid, Flurbiprofen, and its photochemical and photophysical properties have been investigated by means of computational quantum chemistry at the DFT-B3LYP/6-31G(d,p) level. Comparison of computed and experimental singlet and triplet–triplet absorption spectra point to that most experiments, using a range of different solvents, are conducted on the neutral, protonated form of Flurbiprofen. The deprotonated acid, which should dominate at physiological pH, shows no sign of decarboxylation from the lowest singlet excited states, whereas from its first excited triplet state this should readily occur by passing over an energy barrier of <0.5 kcal/mol. Further reactions in the proposed photodegradation mechanism, after decarboxylation, as well as the probability for reactive oxygen species formation are discussed in detail. The generation of the corresponding peroxyl radical from the decarboxylated radical and molecular oxygen is strictly exergonic and occurs without barrier under aerobic conditions. The thus formed peroxyl radical will in turn be capable of initiating propagating lipid peroxidation processes.
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| 38. |
- Nemec, Hynek, et al.
(author)
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Charge transport in nanostructured materials for solar energy conversion studied by time-resolved terahertz spectroscopy
- 2010
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 215:2-3, s. 123-139
-
Journal article (peer-reviewed)abstract
- Spectra of far-infrared conductivity contain useful information on charge transport at nanoscopic length scales. However. decrypting the mechanisms and parameters of charge transport from the measured spectra is a complex task in nanostructured systems in particular, the conductivity is strongly influenced by charge carrier interaction with surfaces or interfaces between constituents of the composite material as well as by local field effects Here we review our work on transient far-infrared conductivity in polymer fullerene bulk heterojunctions and in bare and dye-sensitized semiconductor nanoparticles Measurements performed by time-resolved terahertz spectroscopy are complemented by Monte-Carlo calculations which clearly link the charge transport properties and the terahertz conductivity spectra. (C) 2010 Elsevier B.V. All rights reserved
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| 39. |
- Nielsen, Lisbeth Munksgaard, et al.
(author)
-
Effect of introducing thymine spacers into an adenine strand : Electronic decoupling?
- 2011
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 220:1, s. 1-3
-
Journal article (peer-reviewed)abstract
- Electronic coupling between DNA bases governs the deexcitation pathways after light absorption as well as the ability of the DNA strand to conduct charge. UV excitation of single strands of adenine bases involves two adjacent bases while the spatial extent of the excited state wavefunction following VUV excitation is over eight bases. In this work, we have recorded synchrotron radiation circular dichroism spectra for a series of DNA strands on the form A(n)T(m)A(n), n = 1-5 and m = 1-3, in aqueous solution to study the effect of introducing thymine spacers on the electronic coupling between the adenines. We find that a single thymine spacer is enough to eliminate the strong coupling between the adenine bases for all excitation wavelengths between 175 nm and 330 nm.
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| 40. |
- Nour-Mohammadi, Farahnaz, et al.
(author)
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An investigation of the photosubstitution reaction between N719-dyed nanocrystalline TiO2 particles and 4-tert-butylpyridine
- 2007
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 187:03-feb, s. 348-355
-
Journal article (peer-reviewed)abstract
- The effect of high concentrations of the solar cell additive 4-tert-butylpyridine (4-TBP) on the stability and lifetime of the sensitizer [Ru(Hdcbpy)(2)(NCS)(2)](2-), 2(n-C4H9)(4)N+, (H(2)dcbpy = 2,2'-bipyridine-4,4'-dicarboxylic acid), known as N719, has been evaluated based on kinetic data obtained from simple model experiments. In these experiments, colloidal solutions of N719-dyed nanocrystalline TiO2 particles in acetonitrile were irradiated with 532-nm laser light in the presence of 0-1 mol/l of 4-TBP. Five degradation products were identified using LC-ESIMS: the 4-tert-butylpyridine substitution product [Ru(H(2)dcbpy)(Hdcbpy)(NCS)(4-TBP)] (SP) and the products [Ru(H(2)dcbPY)(2)(NCS)(CN)], [Ru(H(2)dcbpy)(Hdcbpy)(NCS)(CH3CN)], [Ru(H(2)dcbpy)(Hdcbpy)(NCS)(H2O)] and [Ru(H(2)dcbpy)(2)(CN)(2)] (3-6). The sum of the quantum yields of the five products, Phi(deg) = (1.3 +/- 0.2) x 10(-4), was found to be independent of 4-TBP concentration. Based on this observation, a degradation mechanism was proposed, in which the reaction proceeds through the rate-determining formation of a common intermediate complex, I = [Ru-II(H(2)dcbpy)(2)(NCS)(NCS.)](+). An average degradation rate of k(deg) = 6 x 10(-3) s(-1) was obtained from the value Of Phi(deg) and the back electrontransfer rate, k(back) of the reaction TiO2 + e(-) vertical bar N719(+) -> TiO2 vertical bar N719, obtained by means of photo-induced absorption (PIA) measurements. The lifetime of the solar cell sensitizer N719 was estimated to be between 34 years, based on k(deg) and an average literature value of the regeneration rate, k(reg) = 2 x 10(6) M-1 s(-1), of the reaction between TiO2 vertical bar N719(+) and iodide. We conclude that the addition of 4-TBP to dye-sensitized solar cells (DSSC) does not decrease the lifetime of the N719 dye during normal solar cell operation at room temperature.
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| 41. |
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| 42. |
- Osella, S., et al.
(author)
-
Exhibiting environment sensitive optical properties through multiscale modelling : A study of photoactivatable probes
- 2022
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 425
-
Journal article (peer-reviewed)abstract
- To assess a tumor biomarker like the cyclooxygenase-2 enzyme (COX-2), non-invasive imaging techniques are powerful tools. The (non-) linear optical properties of activatable fluorescent probes which are selectively bound to the biomarker can therefore be exploited. The here presented molecular modelling results based on multi-scale modelling techniques highlight the importance of the conformational versatility and of changes in the electronic interactions of such probes when they are embedded in water or in the COX-2 homodimer enzyme. The ANQIMC-6 probe, which combines the binding domain/scaffold of indomethacin (IMC) on COX-2 with the optical properties of acenaphtho[1,2-b]quinoxaline (ANQ), is found to be folded in the solvent and unfolded in the enzyme. A concerted movement of the probe and the protein is seen, while the rotational autocorrelation function exhibits also the intrinsic properties of the probe. Hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) calculations are used to simulate the one-photon and two-photon absorption spectra along with the first hyperpolarizability. The transition has a local character in vacuum, but changes to a charge transfer one in the presence of the microenvironment of the enzyme. This is also visible through a change of the shape of the absorption spectrum, while at the same time the simulated signals of second harmonic generation experiments are strongly enhanced. The results of this work prove that an environment sensitive probe with an anchoring group and an optical active part can be constructed for use in absorption spectroscopy, without the need to revert to fluorescence experiments.
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| 43. |
- Punzi, Marisa, et al.
(author)
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Treatment of synthetic textile wastewater by homogeneous and heterogeneous photo-Fenton oxidation
- 2012
-
In: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 248, s. 30-35
-
Journal article (peer-reviewed)abstract
- The efficiencies of homogeneous and heterogeneous photo-Fenton oxidation were compared for treatment of azo dye containing synthetic textile wastewater. The influence of parameters such as the presence of NaCl and starch was evaluated and optimal iron and H2O2 dosage determined. Complete decolorization of Remazol Red RR was achieved at all investigated NaCl and starch concentration. Mineralization, in terms of COD reduction, was 96% in the homogeneous and 93% in the heterogeneous reaction, but decreased with increasing NaCl and starch concentrations. The homogeneous oxidation showed the highest efficiency in treating synthetic wastewater containing Remazol Blue RR or a mixture of Remazol Red RR and Remazol Blue RR. Nevertheless, the mineralization was significantly lower than for Remazol Red RR, which shows the dependence on dye structure. Similar amounts of iron-containing sludge were produced in the two processes, while the release of iron ions was reduced by 50% when using heterogeneous photo-Fenton. Promising results were obtained when reusing the iron powder as catalyst; complete decolorization was achieved during 20 batches. (C) 2012 Elsevier B.V. All rights reserved.
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| 44. |
- Quintana, Maria, et al.
(author)
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Organic chromophore-sensitized ZnO solar cells : Electrolyte-dependent dye desorption and band-edge shifts
- 2009
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 202:2-3, s. 159-163
-
Journal article (peer-reviewed)abstract
- An organic chromophore D5 (3-(5-(4-(diphenylamino)styryl)thiophene-2-yl)-2-cyanoacrylic acid) was tested as a sensitizer in photoelectrochemical mesoporous ZnO solar cells. Using thin (similar to 3 mu m) mesoporous ZnO electrodes, high incident photon-to-current conversion efficiencies of up to 70% were obtained, while power conversion efficiencies up to 2.4% were found in simulated sunlight (100 mWcm(-2)). Long dye adsorption times (16h) could be used without aggregation or precipitation of the dye. The composition of the iodide/triiodide-based electrolyte was found to be crucial in optimization of the ZnO-based dye-sensitized solar cell. A high concentration of Li+ ions was found to be shift the ZnO conduction band edge to more negative potential, whereas opposite behavior is found for mesoporous TiO2 cells. It was also found to be detrimental for solar cell performance and stability. Electrolyte-dependent and photoinduced dye desorption from the ZnO electrode was identified as a major stability problem in D5-sensitized ZnO solar cells.
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| 45. |
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| 46. |
- Raudonyte-Svirbutaviciene, Eva, et al.
(author)
-
Two-step photochemical inorganic approach to the synthesis of Ag-CeO2 nanoheterostructures and their photocatalytic activity on tributyltin degradation
- 2018
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 351, s. 29-41
-
Journal article (peer-reviewed)abstract
- Herein, we report a simple, sustainable and low-cost approach to design Ag-CeO2 nanoheterostructures in pure aqueous and ethanol containing aqueous solutions via photochemical UV-light driven process with no capping agents nor stabilizers required. To this end, photochemically synthesized CeO2 nanoparticles were applied as photoactive compounds in order to generate formation of metallic silver nanoparticles. Irradiation of deaerated CeO2 suspensions in the presence of Ag+ resulted in the rise of a strong surface plasmon resonance band with a maximum at 393-422 nm in the absorption spectra of the solutions, indicating formation of small metallic silver particles. Faster formation of Ag nanoparticles with the lower amount of silver precursor being required was observed when ethanol was introduced to the reaction solution before the irradiation. This implies that oxidative reactions can be strongly suppressed in deaerated ethanol containing solutions with respect to the pure aqueous media. Not only was the overall efficiency of the process remarkably increased by the use of alcohol, but also smaller and more uniform silver nanoparticles with a size comparable to that of ceria nanoparticles (around 15 nm) were formed when compared to those synthesized without radical scavengers as revealed by TEM analysis. The proposed photochemical approach enables the production of silver-semiconductor system without employing organic stabilizers, thus resulting in formation of nanoparticles with clean, highly reactive metal surface. The as-synthesized silver-ceria nanoheterostructures demonstrated enhanced visible light driven photocatalytic activity on tributyltin (TBT) degradation if compared to pure ceria nanoparticles.
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| 47. |
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| 48. |
- Rubio Pons, Oscar, et al.
(author)
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A butterfly like motion as a clue to the photophysics of thioxanthone
- 2006
-
In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 179:3, s. 298-304
-
Journal article (peer-reviewed)abstract
- A theoretical, quantum-chemical study of the thioxanthone (TX) molecule has been performed at the MP2 and CASPT2 levels of theory. Geometries, absorption energies, and transition and state properties have been investigated. Two conformers have been found very close in energy with planar (P) and non-planar (NP) structures, the latter characterized by a dihedral angle theta = 173.3 degrees representing the bend of the side benzene rings and an out-of-plane angle theta=4 degrees of the C=O bond. Large changes in the relative positions and properties of the two low-lying electronic absorption bands, pi pi* and n pi*, are computed when changing the conformation. As a consequence of the analysis of the TX absorption spectrum it is suggested that TX should be viewed as dynamically changing its conformation between the planar and the non-planar conformations. We coined such behavior as a "butterfly like motion". This dynamic view of the TX structure enables a plausible explanation of the photophysical properties observed for the system.
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| 49. |
- Singh, Aadesh P., 1982, et al.
(author)
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Improved Water Oxidation Performance of Ultra-thin Planar Hematite Photoanode: Synergistic Effect of In/Sn doping and an Overlayer of Metal Oxyhydroxides
- 2020
-
In: Journal of Photochemistry and Photobiology A: Chemistry. - : Elsevier BV. - 1010-6030. ; 401
-
Journal article (peer-reviewed)abstract
- Hematite is a promising photoanode candidate with many favorable material properties, such as stability and suitable band-gap. However, there are some severe challenges, including high losses due to charge recombination and slow oxidation kinetics, which can be addressed by doping and addition of co-catalysts. Here, the effects of temperature driven diffusion of substrate impurities (doping) and subsequent surface modification by metal oxy-hydroxides (co-catalysts) have been studied for enhanced water-oxidation performance in photoelectrochemical (PEC) measurements. Diffusion of indium and tin from the indium-doped tin oxide (ITO) substrate into planar films of α-Fe2O3 photoanodes results in a photocurrent density (Jph) of 0.09 mA/cm2, corresponding to an approximate 9-fold enhancement over the control pristine α-Fe2O3 (0.01 mA/cm2) at 1.23 VRHE. A thin amorphous FeOOH coating over the In/Sn co-doped α-Fe2O3 photoanode improves the water oxidation performance further, with a 211 % enhancement in Jph at 1.23 VRHE and a 0.21 V cathodic shift in onset potential. Thin layers of NiOOH and FeNiOOH co-catalysts exhibit 100 and 155 % enhancement in Jph, respectively. Characterization and electrochemical measurements reveal that the enhanced performance is a result of reduced bulk recombination by temperature driven In/Sn substrate impurity doping and improved surface oxidation kinetics by the metal oxy-hydroxide overlayer. Especially deposition of FeOOH onto In/Sn co-doped α-Fe2O3 significantly reduces resistance at the semiconductor/electrolyte interface, leading to the shift in onset potential. Further, the results indicate that all the samples exhibit a quantitative correlation between the cathodic shift in photocurrent onset potential (Vonset) and flat band potential (Vfb).
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| 50. |
- Tian, Haining, 1983-, et al.
(author)
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Hydrogen evolution by a photoelectrochemical cell based on a Cu2O-ZnO-[FeFe] hydrogenase electrode
- 2018
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In: Journal of Photochemistry and Photobiology A. - : Elsevier BV. - 1010-6030 .- 1873-2666. ; 366, s. 27-33
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Journal article (peer-reviewed)abstract
- A Cu2O-ZnO-hydrogenase photocathode possessed enzyme/semiconductor junction has been constructed by immobilizing a biological protein catalyst, hydrogenase-CrHydA1 enzyme on the ZnO protected Cu2O electrode. With light illumination, a photocurrent of 0.8 mA/cm2 at 0.15 V vs. RHE was obtained and hydrogen was successfully detected from the photocathode in photoelectrochemical measurements with Faradaic efficiency of ca. 1%. The construction as well as the stability of the system are also reported. The result shows that this biohybrid photocathode is capable of photocatalytic proton reduction under mild conditions.
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