Amplified singlet oxygen generation in metallated-porphyrin doped conjugated polymer nanoparticles
Abstract We report on the mechanism and efficiencies of singlet oxygen O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) generation of nanoparticles (NP) of the conjugated polymer (CP) poly(9,9-dioctylfluorene- alt -benzothiadiazole) (F8BT) doped with platinum octaethylpor...
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| Autores principales: | , , , , , , , |
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| Formato: | Articulo |
| Lenguaje: | Inglés |
| Publicado: |
2018
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| Materias: | |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/124432 |
| Aporte de: |
| Sumario: | Abstract We report on the mechanism and efficiencies of singlet oxygen O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) generation of nanoparticles (NP) of the conjugated polymer (CP) poly(9,9-dioctylfluorene- alt -benzothiadiazole) (F8BT) doped with platinum octaethylporphyrin (PtOEP) suspended in water. A detailed study of the photophysics of these NP, using stationary and time-resolved absorption and emission techniques, indicates that O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) is generated by the triplet excited state of F8BT and not by that of PtOEP, as previously observed for other porphyrin doped CP NP. O<sub>2</sub> (<sup>1</sup>Δ<sub>g</sub>) quantum yields (Φ<sub>Δ</sub>) were measured by quantifying the characteristic phosphorescence of O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) in the NIR region (∼1268 nm). It was found that incorporation of relatively small amounts of PtOEP to F8BT NP results in a significant increase of Φ<sub>Δ</sub>. NP containing 10% PtOEP (w/w) show a Φ<sub>Δ</sub> ∼ 0.24, which is 3 times larger than that observed for undoped F8BT NP, and larger than the reported for most water-soluble porphyrins. Φ<sub>Δ</sub> were also calculated from the oxidation rates ( v 0 ) of 3-[10-(2-carboxyethyl)anthracen-9-yl]propanoic acid (ADPA), a well-known chemical O<sub>2</sub>(<sup>1</sup>Δ<sub>g</sub>) trap. Unexpectedly, this method was found to significantly overestimate the Φ<sub>Δ</sub> values due to the adsorption of ADPA on the surface of NP. The ADPA/NP adsorption process was characterized using a simple adsorption model yielding an (average) equilibrium constant of ∼8 × 10<sup>3</sup> M<sup>−1</sup> and an (average) number of NP-binding sites of ∼14000. These results necessarily caution about the use of ADPA as a probe to evaluate Φ<sub>Δ</sub> in these NP systems. In addition, the interaction of F8BT NP with other anionic, cationic and zwitterionic dyes (dissolved in water) was studied. It was found that even at nano-molar concentrations all the dyes efficiently adsorb on the NP surface. This general and simple self-assembly strategy can be used to prepare superficially-dye-doped CP NP with potentially interesting technological applications. |
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