| 1. |
- Ruseckas, Arvydas, et al.
(author)
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Luminescence quenching by inter-chain aggregates in substituted polythiophenes
- 2001
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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
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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
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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)
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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
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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
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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
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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)
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Photooxidation of an azo dye induced by visible light incident on the surface of TiO2
- 2001
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In: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY. - : ELSEVIER SCIENCE SA. - 1010-6030. ; 140:1, s. 87-92
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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
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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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