Photoluminescence properties

The light-emitting properties of thiophene oligomers and polymers have recently been reviewed and the structural modifications for the tuning of the emission properties of these materials analyzed and discussed in detail [28]. 

The presence of oxidized thienyl groups in the conjugated chain of oligo- and polythiophenes deeply modifies their optical and photophysical properties with respect to their fully aromatic counterparts. Absorption and emission wavelengths are red shifted by several nanometers, owing to increased n-electron 

It is seen that on going from unsubstituted quinquethiophene 1 to the dialkylated derivative 2, the PLQY in solution decreases remarkably, probably due to distortion from planarity, whereas the PLQY in the solid state remains unaltered and very low. After oxidation of the inner ring, i.e. on going from pentamer 2 to pentamer 3, the PLQY value in solution drops by more than one order of magnitude whereas that in the solid state increases by a similar amount. Further functionalization of the thienyl groups with head-to-head methyl substituents, leading to pentamer 4, does not modify the PLQY value in solution, but further enhances that in the solid state, which reaches the remarkable value of 37 %. 

Several studies of the trend of variation in PL intensity of oligothiophene-5,5-dioxides with solvent properties (including viscosity) confirm this assumption [42-44, 52-54], 

In the table absorption wavelengths (nm) and PL quantum yields (%) of compounds 4 and 6-10 before and after room-temperature nanoimprint lithography (RT-NIL). (a) AFM two-dimensional view of a 400 nm periodic grating transferred into the non-thermoplastic oligothiohene-S,S-dioxide 9, and correponding cross-section (b). The height of the features is about 30 nm. 

---

The introduction of bulky side chains that contain adamantyl groups to poly(p-phenylenevinylene) (PPV), a semiconducting conjugated polymer, decreases the number of interchain interactions. This action will reduce the aggregation quenching and polymer photoluminescence properties would be improved [93]. 

Assefa, Z Forward, J.M., Grant T.A., Staples, R.J., Hanson, B.E., Mohamed, A.A. and Fackler, J.P. Jr (2003) Three-coordinate, luminescent, water-soluble gold(l) phosphine complexes structural characterization and photoluminescence properties in aqueous solution. Inorganica Chimica Acta, 352, 31 5. 

Lu, W., Li, Y, Chan, M.C.W., Che, C.-M., Cheung, K.-K and Zhu, N. (2002) Organic triplet emissions of arylacetylide moieties harnessed through coordination to [Au(PCy3)]. Effect of molecular structure upon photoluminescent properties. Journal of the American Chemical Society, 124,14696-14706 (c) Lu, W., Zhu, N. and Che, C.M. (2003) Polymorphic forms of a gold(I) arylacetylide complex with contrasting phosphorescent characteristics. Journal of the American Chemical Society, 125, 16081—16088 ... 

This chapter presents an overview of the synthesis, ensemble photoluminescence properties and blinking of single CdSe quantum dots. The stress is on (i) widely accepted methods of synthesis, (ii) the origin of photoluminescence and variations of photoluminescence as functions of surface-coating, surface-passivating molecules, chemical environment, and thermal- and photo-activations, and (iii) photolumines-... 

Table 3 Photoluminescence properties of substituted A1Q3 complexes.

Poly(l,4-naphthylenevinylenes) have been prepared by metathesis polymerization of benzobarrelenes [181,182] and the photoluminescence properties of homopolymers and block-copolymers have been studied in some detail [183]. PPV also has been prepared via ROMP of [2.2]paracyclophane-l,9-diene [184] and ROMP of a paracyclophene that contains a solubilizing leaving group [185]. The resulting polymer is converted to PPV upon acid catalysis at room temperature. ADMET of 2,5-dialkyl-l,4-divinylbenzenes using Mo or W catalysts has... 

Q.D. Ling, E.T. Kang, K.G. Neoh, and W. Huang, Synthesis and nearly monochromatic photoluminescence properties of conjugated copolymers containing fluorene and rare earth complexes, Macromolecules, 36 6995-7003, 2003. 

W.-S. Li, D.-L. Jiang, and T. Aida, Photoluminescence properties of discrete conjugated wires wrapped within dendrimeric envelopes "dcndrimer effects on -ir-electronic conjugation, Angew. Chem. Int. Ed., 43 2943-2947, 2004. 

Nonprobability sampling, 26 1001 Nonproduct contact utilities, 11 45-46 Nonprotein amino acids, 2 554 Nonprotein nitrogen (NPN), 10 865 Nonquenching photoluminescence properties, 26 804-805... 

It is noteworthy that fluorescence detection is a very specific technique, especially when excitation and emission wavelengths can be selected. In addition to this, sensitivity for compounds with photoluminescence properties can be higher by factors of 100 to 1000 when compared with that of other detectors. 

It is reported that the band structure of ZnS doped with transition metal ions is remarkably different from that of pure ZnS crystal. Due to the effect of the doped ions, the quantum yield for the photoluminescence of samples can be increased. The fact is that because more and more electron-holes are excited and irradiative recombination is enhanced. Our calculation is in good correspondence with this explanation. When the ZnS (110) surface is doped with metal ions, these ions will produce surface state to occupy the valence band and the conduction band. These surface states can also accept or donate electrons from bulk ZnS. Thus, it will lead to the improvements of the photoluminescence property and surface reactivity of ZnS. 

Kim D, Miyamoto M, Nakayama M (2005) Photoluminescence properties of CdS and CdMnS quantum dots prepared by a reverse-micelle method. J Electron Microsc 54 131-134... 

The compound P-Ga203 Dy, which has photoluminescence properties but no commercial significance, is described in [5.386],... 

Abstract We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(/ -phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex. 

As mentioned in the introduction section, the photoluminescent properties of molecular assemblies depend on the assembled structures of photoluminescent moieties [11, 21-34]. If assembled structures of photoluminescent moieties are changed by external stimuli, stimuli-responsive photoluminescent materials can be prepared. Recently, we have reported on anthracene, pyrene and naphthalene derivatives 1-3 having dendritic moieties which contain amide moieties to form intermolecular hydrogen bonds (Fig. 2) [28-30]. These dendritic moieties are known to be... 

Compounds 1-3 exhibit mechano- and/or thermochromic photoluminescent properties accompanied by cubic-columnar LC phase transitions. Table 1 shows the LC properties of compounds 1-3. Compounds 1 and 3 show cubic phases and columnar phases on rapid cooling and slow cooling, respectively. A columnar phase is not observed for compound 2 on cooling. The differential scanning calorimetry (DSC) measurements of compounds 1-3 show that the cubic phases of compounds 1-3 are metastable phases, while the columnar phases are stable. The X-ray diffraction patterns indicate that compounds 2 and 3 form Pmhn cubic phases and PH a rectangular columnar phases. 

---