Search results for "Conjugated"

Observation of Very Narrow Linewidths in the Fluorescence Excitation Spectra of Single Conjugated Polymer Chains at 1.2 K

2007

Fluorescence emission and excitation spectra of single poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] polymer molecules embedded in poly(methylmethacrylate) have been recorded at 1.2 K. The ubiquitous spectral diffusion causes large variations in the spectral shape and apparent linewidth in the emission spectra. Nevertheless, we find very narrow (approximately 0.1 cm(-1)) purely electronic zero-phonon lines in the excitation spectra, which are 2 orders of magnitude smaller than previous estimates of the homogeneous linewidth. These results complement the molecular description of the low energy transitions in conjugated polymers.

New amphiphilic conjugates of mono- and bis(carboxy)-PEG(2,000) polymers with lipoamino acids as surface modifiers of colloidal drug carriers

2010

Effects of tannin-containing diets on small ruminant meat quality

2010

Tannins are phenolic compounds present in several forages, tree leaves and by-products used for small ruminant feeding in the Mediterranean area. Although the effects of dietary tannins on small ruminant growth performances have been largely studied, only in the last ten years researchers have started to study the effects of tannins on meat quality. Meat from small ruminants given tanniniferous diets is lighter in colour compared to meat from animals given the same diets but in which the effects of tannins have been eliminated by the supplementation of polyethylene glycol. This result has been obtained with tannins from different feeds (carob pulp, acacia leaves or sulla fresh herbage). Rec…

Non-linear optical spectra of excitons in polydiacetylene

1992

Abstract Adding long-range Coulomb interactions to the Su-Schrieffer-Heeger model makes it possible to investigate excitonic states in conjugated polymers. Various characteristic features due to these states as well as due to the electron-hole continuum can be found in the calculated non-linear optical susceptibilities. In particular the electroabsorption spectrum and the third harmonic generation intensity and its dependence on the system size are examined. Using only moderate interaction strength, various experiments in polydiacetylene can be interpreted in a consistent way.

Quinonoid π-extended tetrathiafulvalenes (TTFs)

2001

Publisher Summary Tetrathiafulvalene (TTF) is a fascinating planar πelectron-donor molecule with a broad range of potential applications. TTF and its derivatives play an important role in the field of organic conductors forming charge-transfer (CT) complexes and radical cation salts (Bechgaard salts) with a huge variety of electron-acceptor molecules and anions in the search for electrically conducting and superconducting materials. The chapter focuses on highly π-extended electron donors with p-quinodimethane structures as interesting precursors of materials with non-conventional properties. The first dimeric examples of π-extended TTF derivatives connected through an oxygen atom are also …

Conjugated Compounds Based on Vinylthiazole Units

2007

Conjugated oligomers attract increasing attention because of their interesting properties in materials science [1]. Moreover, they are model compounds for conjugated polymers. Molecules polarized by electronic effects, in particular push-pull systems having terminal donor-acceptor substitution represent a special class of such oligomers [2]. Their major applications are in the field of nonlinear optics (NLO), twophoton absorption (TPA), two-photon induced fluorescence (TPIF), and photorefractive materials (PR). Fig. 1 illustrates known 2,5-thienylenevinylenes with zwitterionic resonance structures 1 (D = NR2; A = NO2, CHO, SO2R; n = 1, 2) [3, 4]. The corresponding compounds 2 with thiazole …

Photoactive Hybrid Materials based on Conjugated Porous Polymers and Inorganic Nanoparticles

2021

This review explores the current state‐of‐the‐art for functional photoactive hybrids containing inorganic nanoparticles (magnetic and metal) and conjugated organic porous polymers (CPPs). Albeit new in the field, with the first hybrid material of this kind reported in 2012, those materials have gained increasing interest in applications such as sensing, heterogeneous catalysis, photocatalysis, and lithium‐ion batteries (LIBs). This review describes the two main synthetic strategies for those materials, namely, 1) using the chemical and morphological features (e.g., porosity and complexation sites) of CPPs to in situ form nanoparticles and 2) fabricating the nanoparticle for templating CPPs.…

π-Conjugated diimidazolium salts: rigid structure to obtain organized materials.

2015

Phenylene ethynylene based diimidazolium salts differing in the alkyl chain length borne on the imidazolium ion and anion nature were synthesized. Their properties were studied both in solution and in the solid state. Salts obtained were able to aggregate in organic solvent solution. Aggregate formation was studied by performing concentration dependent measurements using UV-vis, fluorescence and Resonance Light Scattering. Furthermore, features of the aggregates were also investigated in the solid state by means of fluorescence and Scanning Electron Microscopy measurements. Finally, Density Functional Theory calculations were performed to obtain insights into the interaction geometry in the…

Effective conjugation in conjugated polymers with strongly twisted backbones: A case study on fluorinated MEHPPV

2016

Conjugated polymers with strongly twisted backbones, such as MEHPPV with fluorinated vinylene units (F-MEHPPV), demand a redefinition of the all-important ‘effective conjugation length’ ECL, which we extract here by a facile graphical method. In MEHPPV (being essentially planar), the ECL coincides with the ‘maximum conducive chain length’ MCC and extends over about n ≈ 9 repetition units (RU). In F-MEHPPV, the MCC is similarly long with n ≈ 8, but the ECL localizes on just one RU. The strong twist in F-MEHPPV persists in the excited state, broadening the emission spectrum and quenching the fluorescence with reduced radiative and enhanced non-radiative rates.

Changes in ewe milk fatty acids following turning out to pasture

2008

Abstract Ten Comisana dairy ewes were selected to observe time of changing in milk fatty acids as a result of switching from stall to pasture feeding. At first, ewes were subjected to a stall-feeding period of 30 days (pre-experimental phase). After which, ewes were abruptly turned out to a vetch and oats pasture as their sole feed (experimental phase). Individual milk samples were collected on experimental days 0 (the last day of stall feeding), 1–4, 8, 11, 17 and 23. Milk and feeds fatty acid composition was determined by gas chromatography. The sudden passage from a stall to a pasture diet significantly modified the fatty acid profile of ewe milk. Medium- and long-chain fatty acids were …