Synthetic Methods of CTS and CZTS Nanocrystals

The synthesis of various morphologies of copper zinc tin sulfide (Cu2ZnSnS4) and copper tin sulfide (Cu2SnS3) nanocrystals were explored to find a more energy efficient synthesis. Reactions were all carried out at 220°C under either inert atmospheres or normal conditions. Variations in synthetic methods included reaction time and solvents used. Products were analyzed with powder X-Ray diffraction and compared to simulated powder patterns of zincblende and wurtzite nanocrystals. The synthesis of CTS nanocrystals required the reaction to be heated to 220°C overnight under an inert atmosphere. The reaction used for the synthesis of CZTS nanocrystals required less energy and only required the reaction to be heated to 220°C for four hours. The effects of solvents were found to be that 1-octadecene (ODE) yielded predominantly a zincblende morphology, oleylamine (OAm) yielded predominantly a Wurtzite morphology, and the use of 1-dodecanethiol (DDT) as the only solvent yielded a mixture of zincblende and Wurtzite nanocrystals. The various nanocrystals produced assisted in achieving our overall goal by narrowing down an energy efficient and effective synthesis of CZTS and CTS nanocrystals using earth-abundant and low cost reagents.https://digitalcommons.morris.umn.edu/urs_2015/1001/thumbnail.jp

Enhanced functionality for donor-acceptor oligothiophenes via Inclusion of BODIPY : synthesis, electrochemistry, photophysics and model chemistry

We have synthesized several new push-pull oligothiophenes based on the BODIPY moiety as the electron acceptor and the well known oligothiophenes substituted with N,N-dialkylamino groups to enhance the electron donor ability. A complete characterization of the electronic properties has been done consisting of their photophysical, electrochemical and vibrational properties. The compounds have been studied after chemical treatment with acids and after oxidation. In this regard, they can be termed as NIR dyes and amphoteric redox electroactive molecules. We have described the presence of dual fluorescence in these molecules and fluorescence quenching either by energy transfer or, in the push-pull molecules, by the electron exchange. The combination of electrochemical and proton reversibility combined with the interesting optical properties of the new species offer an interesting platform for sensor and material applications.DGES, MEC (Spain) and Fundação para a Ciência e a Tecnologia (FCT

Fingerprints of Through-Bond and Through-Space Exciton and Charge π-Electron Delocalization in Linearly Extended [2.2]Paracyclophanes

New stilbenoid and thiophenic compounds terminally functionalized with donor–donor, acceptor–acceptor, or donor–acceptor moieties and possessing a central [2.2]­paracyclophane unit have been prepared, and their properties interpreted in terms of through-bond and through space π-electron delocalization (i.e., π-conjugations). Based on photophysical data, their excited-state properties have been described with a focus on the participation of the central [2.2]­paracyclophane in competition with through-bond conjugation in the side arms. To this end, two-photon and one-photon absorption and emission spectroscopy, as a function of temperature, solvent polarity, and pressure in the solid state have been recorded. Furthermore, charge delocalization through the [2.2]­paracyclophane in the neutral state and in the oxidized species (radical cations, dications and radical trications) has been investigated, allowing the elucidation of the vibrational Raman fingerprint of through-space charge delocalization. Thus, a complementary approach to both “intermolecular” excitation and charge delocalizations in [2.2]­paracyclophane molecules is shown which can serve as models of charge and exciton migration in organic semiconductors

Halogen Interactions in Halogenated Oxindoles: Crystallographic and Computational Investigations of Intermolecular Interactions

X-ray structural determinations and computational studies were used to investigate halogen interactions in two halogenated oxindoles. Comparative analyses of the interaction energy and the interaction properties were carried out for Br···Br, C-H···Br, C-H···O and N-H···O interactions. Employing Møller–Plesset second-order perturbation theory (MP2) and density functional theory (DFT), the basis set superposition error (BSSE) corrected interaction energy (Eint(BSSE)) was determined using a supramolecular approach. The Eint(BSSE) results were compared with interaction energies obtained by Quantum Theory of Atoms in Molecules (QTAIM)-based methods. Reduced Density Gradient (RDG), QTAIM and Natural bond orbital (NBO) calculations provided insight into possible pathways for the intermolecular interactions examined. Comparative analysis employing the electron density at the bond critical points (BCP) and molecular electrostatic potential (MEP) showed that the interaction energies and the relative orientations of the monomers in the dimers may in part be understood in light of charge redistribution in these two compounds