No abstract

Various properties of (CdSe) 3n clusters (n = 1−9) were obtained using computational techniques. Using a simple force field, a simulated annealing technique was employed to explore the potential energy landscape and identify the isomers available at low temperatures. The lowest energy isomer was then optimized using density functional theory, and the quantities associated with their stability and optoelectronics were calculated. The possibility of fluxionality for a given range of temperatures and solvents was characterized by computing thermodynamic properties and inherent structure energies. All studied systems give rise to energetically stable hollow structures composed of six-and fourmembered rings that changed from spherical to tubular as the number of atoms increased. For a solvent of dielectric constant equal to three, fluxionality was observed at 300 K for almost all clusters considered. The corresponding band gap was found to be ∼3 eV and relatively independent of the size of the clusters in this size range. The absorption coefficients (as calculated from the dielectric functions) obtained from fluxionality effects are in agreement with the experimental absorption profiles.

With the world population expected to reach 8.5 billion by 2030, demand for access to electricity and clean water will grow at unprecedented rates. Municipal solid waste combusted at waste to energy (WtE) facilities decreases waste volume and recovers energy, but yields ash as a byproduct, the beneficial uses of which are actively being investigated. Ash is intrinsically hydrophobic, highly oxidized, and exhibits high melting points and low conductivities. The research presented here explores the potential of ash to be used as an electrode material for a microbial fuel cell (MFC). This application requires increased conductivity and hydrophilicity, and a lowered melting point. Three ash samples were investigated. By applying an electric potential in the range 50-125 V across the ash in the presence of water, several key property changes were observed: lower melting point, a color change within the ash, evidence of changes in surface morphologies of ash particles, and completely wetting water-ash contact angles. We analyzed this system using a variety of analytical techniques including sector field inductively coupled plasma mass spectrometry, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and tensiometry. Ability to make such surface modifications and significant property changes could allow ash to become useful in an application such as an electrode material for a MFC.

The kinetics of the synthesis of noncommercially available quantum dot (QD) solvent N-oleoylmorpholine (NOM) was investigated in a semibatch reactor system to enable scale up. Morpholine was injected into excess oleic acid (OA) at rates of 250 and 500 μL/h at 110, 140, and 170 °C. The reaction was found to be zero order in morpholine, first order in OA, and first order overall for temperatures ≥140 °C. At < 140 °C, the reaction does not follow elementary kinetics with respect to OA. Thermodynamic calculations using the Eyring−Polyani equation determined that the entropy change from the reagents to the transition state was negative, suggesting an associative complex intermediate species. The reaction mechanism was further analyzed via IR and NMR, revealing a carboxyl−amino intermediate, which was long lived (>1 h) at 110 °C but short lived (<30 min) at 170 °C. Conversions of 85% to near completion are achievable for OA, and excess morpholine was removed via rotary evaporation, thus yielding NOM with 70−98% purity.