Roberto Fusco

Syndiotactic Polymerization of Propylene: Single‐Site Vanadium Catalysts in Comparison with Zirconium and Nickel

The syndiotactic-specific polymerization of propylene can be promoted by single-site catalysts based on vanadium, nickel and group IV metals. The polymerization mechanisms are reasonably well established for nickel and group IV metals. For vanadium catalysts the polymerization mechanisms reported in the literature are still debatable, since the stereochemistry of the monomer insertion is well known, but the active species have never been isolated. In this paper the mechanisms concerning Ni and group IV metal catalysts are briefly summarized and proposed mechanisms concerning vanadium are compared within one another.

Enhanced energy transport in genetically engineered excitonic networks

One of the challenges for achieving efficient exciton transport in solar energy conversion systems is precise structural control of the light-harvesting building blocks. Here, we create a tunable material consisting of a connected chromophore network on an ordered biological virus template. Using genetic engineering, we establish a link between the inter-chromophoric distances and emerging transport properties. The combination of spectroscopy measurements and dynamic modelling enables us to elucidate quantum coherent and classical incoherent energy transport at room temperature. Through genetic modifications, we obtain a significant enhancement of exciton diffusion length of about 68% in an intermediate quantum-classical regime.

Ethylene polymerization catalyzed by metallocene/ methylaluminoxane systems : quantum-mechanical study on the role of olefin separated ion pairs (OSIP) in the polymerization mechanism

DFT (density-functional theory) calculations were performed to investigate the thermodynamics of formation of Olefin Separated Ion Pairs (OSIP) Cp2MtCH3+/C2H4/Cl2Al[O(AlMe3)AlHMe] (Cp = η5-C5H5, Mt = Ti, Zr, Me = CH3) from ethylene and Cp2MtMe · Cl2Al[O(AlMe3)AlHMe]2, a model of adduct produced by metallocence/methylaluminoxane (MAO) systems for olefin polymerization. The results account for the high cocatalytic activity of MAO and show that titanium complexes are potentially more active than zirconium homologues, as confirmed by low temperature polymerization tests.

Cascade luminescent solar concentrators

We propose a luminescent solar concentrator (LSC) characterized by a strong enhancement of the concentration factor in which the area covered by photovoltaic cells is independent of the area over which sunlight is collected. We name this device cascade-LSC (c-LSC), as sunlight is both geometrically and spectrally concentrated by cascading absorption and emission into different LSCs. We demonstrate a prototype and measure the generated photocurrent. The results are in good agreement with those predicted by our numerical model based on Monte Carlo simulations.

Enhanced downconversion of UV light by resonant scattering of aluminum nanoparticles

Metallic nanoparticles are known to enhance nonlinear optical processes due to a local enhancement of the optical field. This strategy has been proposed to enhance downconversion in thin film solar cells, but has various disadvantages, among which is the fact that the enhancement occurs only in a tiny volume close to the particles. We report on a very different physical mechanism that can lead to significant downconversion enhancement, namely, that of resonant light scattering, and which is a large volume effect. We show that only a tiny amount of resonantly scattering metallic (aluminum) nanoparticles is enough to create a significant enhancement of the fluorescence of dye molecules in the visible wavelength range. The strategy can be applied in general to increase the emission of UV-absorbing constituents, and is of particular use for solar energy.

Comparison of photochromic behaviour between spiroxazines and spiropyrans: theoretical calculations of ground and excited states

MOPAC/AM1 and CNDO/S calculations have been performed on a spiro[indoline-naphthoxazine], a spiro[indoline-naphthopyran] and their open merocyanine(s) form. The energies were fully optimized and the bond orders, charge distribution and energies of both ground and excited states evaluated. The theroretical absorption spectra were calculated and found in good agreement with the experimental ones.

Molecular conformations of methotrexate

Abstract The molecular conformations of methotrexate were studied in detail by force field techniques. A large number of low-energy minima were detected by mean