Spectroscopic Characterization and Modeling of Quadrupolar Charge-Transfer Dyes with Bulky Substituents

Joint experimental and theoretical work is presented on two quadrupolar D-π-A-π-D chromophores characterized by the same bulky donor (D) group and two different central cores. The first chromophore, a newly synthesized species with a malononitrile-based acceptor (A) group, has a V-shaped structure that makes its absorption spectrum very broad, covering most of the visible region. The second chromophore has a squaraine-based core and therefore a linear structure, as also evinced from its absorption spectra. Both chromophores show an anomalous red shift of the absorption band upon increasing solvent polarity, a feature that is ascribed to the large, bulky structure of the molecules. For these molecules, the basic description of polar solvation in terms of a uniform reaction field fails. Indeed, a simple extension of the model to account for two independent reaction fields associated with the two molecular arms quantitatively reproduces the observed linear absorption and fluorescence as well as fluorescence anisotropy spectra, fully rationalizing their nontrivial dependence on solvent polarity. The model derived from the analysis of linear spectra is adopted to predict nonlinear spectra and specifically hyper-Rayleigh scattering and two-photon absorption spectra. In polar solvents, the V-shaped chromophore is predicted to have a large HRS response in a wide spectral region (approximately 600–1300 nm). Anomalously large and largely solvent-dependent HRS responses for the linear chromophores are ascribed to symmetry lowering induced by polar solvation and amplified in this bulky system by the presence of two reaction fields

Att skapa läroplan för de yngsta barnen i förskolan. Barns perspektiv och nuets didaktik

This thesis takes as one point of departure the concept of the expanded curriculum where curricula encompass both the formal steering documents, as well as that which goes on within the framework of preschool education and through the actors in preschools. The overarching purpose is therefore to generate knowledge about what conditions for learning the work of teachers make possible when curricula are created in preschool settings for children aged between 1 and 3. The purpose is also to contribute with knowledge about what these created curricula would mean for children’s agency, and the importance they can have for children’s opportunities for learning and development. The three empirical studies consist of digitally recorded interviews with teachers and video observations with a focus on teachers’ communication with children in preschool. The discussion in the overarching text is constructed around three aspects that emerge in the overall results of the studies. First, the studies reveal how teachers’ work can be likened to a limiting curriculum which, on the one hand, is entirely child-centered, with the children as seen actors, but, on the other, can be interpreted as entirely teacher-centered. Secondly, there is the discussion about the affirmative curriculum, where children are presented as affirmed actors. In other words, content becomes those things that children are interested in, and their modes of expression are seen, affirmed and often repeated. Finally there is the discussion about the possibilities and dilemmas related to an expanding curriculum where children are regarded and treated as real actors in the sense that their intentions and expressions are taken seriously as relevant challenges. The current curriculum text for Swedish preschool can, in this sense, be seen as an obstacle in that its formulations are extremely broad-based, as discussed related to the results of this thesis

Synthesis and Self-Assembly of Donor–Acceptor–Donor Based Oligothiophenes and Their Optoelectronic Properties

In this work, the synthesis of an oligothiophene having a donor acceptor donor (D-A-D) chromophore with hydrogen bonding groups is described. The D-A-D molecule was demonstrated to self-organize via intermolecular H-bonding between barbituric acid units. Interactions between the oligothiophene subunits were also found to be important, affording nanoribbons that could be observed by atomic force and transmission electron microscopy. The applicability of the oligothiophene for organic electronic applications was investigated by fabricating organic field-effect transistors (OFETs) and organic photovoltaic devices. The OFET measurements yielded p-type mobility of 7 x 10(-7) cm(2)/(Vs), and when blended with C(60)-PCBM, the photovoltaic efficiency was observed to be 0.18%