Photoluminescence polymer film

Photoluminescence intensity of the amorphous polymers was generally much larger than that of the more crystalline polymers. The energy level of the lowest singlet excited state Es was evaluated to be 2.5-2.7 eV for the amorphous polymer pristine films, and 2.0 eV for the more crystalline polymers. The Stokes shifts were also observed to be much larger for the amorphous polymer films compared with those of the more crystalline polymer films. This indicates a larger structural relaxation of the amorphous polymers following photoexcitation. 

TABLE 8.1. Photoluminescence Quantum Yields of Selected Para-phenylene-Type Oligomer and Polymer Films and Solutions. 

Martini IB, Smith AD, Schwartz BJ (2004) Exciton-exciton annihilation and the production of interchain species in conjugated polymer films Comparing the ultrafast stimulated emission and photoluminescence dynamics of MEH-PPV. Phys Rev B 69(3)... 

Figure 1. Photoluminescence emission spectra (PL) and photoluminescence excitation spectra (PLE) of CdSiMn nanocrystals embedded in a polymer film.

Incorporation in polysiloxane film Fixed amounts of polysiloxane containing carboxyl groups at side chains (prepared by the author, refer to reference [32]), Ru(bpy)3 7 and 8 were dissolved in ethanol to obtain a concentration of the total solutes of 0.02 gmL". The solution was cast on a glass plate and allowed to dry under vacuum at 35 °C to prepare a polymer film. The film thickness was estimated to be 1 pm. The Ru complex concentration in the film was fixed at 0.05 mol dm (estimated by using a film density of 1.3 g mL) to minimize the concentration quenching of the photoluminescence from Ru(bpy)3. At this concentration only 10% of the photoexcited Ru complex is subject to concentration quenching. The concentration of in the film was ifom 0.04 to 0.20 mol dm . ... 

The complexation of Fe(i/ -C5H5) groups to ca. 60% of the main-chain arene moieties in low molecular weight samples (Afn=1700) of poly(n-hexylphenylene) to yield 4.41 has also been reported [88]. Interchain cross-linking appears to be induced by electrochemical reduction, resulting in the formation of an insoluble polymer film on the electrode. Attachment of the FeCp group also leads to a modification of the photoluminescence intensity and emission wavelength. 

FIGURE 5.4 Absorption, photoluminescence emission, and photoinduced absorption spectrum of a typical poly(pflrfl-phenylene)-type polymer film. The inset shows a poly(2,5-disubstituted-l,4-phenylene). 

FIGURE 5.6 Absorption, photoluminescence emission, and photoinduced absorption spectrum of a typical polyindenofluorene-type polymer film. The inset shows the actual chemical structure with R being a linear alkyl chain (from Setayesh, S., Marsitzky, D., and Mullen, K., Macromolecules, 33,2016,2000) or an aryl-substituted group (from Jacob, J., Sax, S., Piok, T, List, E.J.W., Grimsdale, A.C., and Mullen, K., /. Am. Chem. Soc., 126, 6987, 2004). 

Lauerhaas JM, Sailor MJ (1993) The effects of halogen exposure on the photoluminescence of porous silicon. Mater Res Soc Symp Proc (USA) 298 259-263 Lees IN, Lin H, Canaria CA, Miskelly GM et al (2003) Chemical stability of porous silico surfaces electrochemically modified with functional alkyl species. Langmuir 19 9812-9817 Li K, Diaz DC, He Yet al (1994) Electroluminescence Ifom porous silicon with conducting polymer film contacts. Appl Phys Lett 64(18) 2394-2396... 

Potyrailo and Leach (2006) used the same approach. They evaluated the response of the luminescence from CdSe nanoparticles incorporated into a polymer film to the exposure of polar and nonpolar vapors. It was found that different size nanocrystals provided individual photoluminescence response patterns when the sensor film was exposed to methanol and toluene. Ma et al. (2009) have shown that under optimal conditions the PL intensity of CdTe QDs incorporated in poly(dimethyldiallylammonium chloride) decreased linearly with the increase of formaldehyde concentration in the range 5-500 ppb. The detection limit for formaldehyde was 1 ppb. Other examples of QD-based gas sensors are presented in Table 5.1. 

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