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Amelia M.,University of Bologna | Lincheneau C.,University of Bologna | Silvi S.,University of Bologna | Silvi S.,Interuniversity Center for the Chemical Conversion of Solar Energy SolarChem | And 2 more authors.
Chemical Society Reviews | Year: 2012

Semiconductor nanocrystal quantum dots (QDs), owing to their unique opto-electronic properties determined by quantum confinement effects, have been the subject of extensive investigations in different areas of science and technology in the past two decades. The electrochemical behaviour of QDs, particularly for CdSe and CdTe nanocrystals, has also been explored, although to a lesser extent compared to the optical properties. Voltammetric measurements can be used to probe the redox levels available for the nanocrystals, which is an invaluable piece of information if these systems are involved in electron transfer processes. Electrochemical data can also foster the interpretation of the spectroscopic properties of QDs, and give insightful information on their chemical composition, dimension, and surface properties. Hence, electrochemical methods constitute in principle an effective tool to probe the quality of QD samples in terms of purity, size dispersion, and surface defects. The scope of this critical review is to discuss the results of electrochemical studies carried out on CdSe and CdTe core and core-shell semiconductor nanocrystals of spherical shape. Examples of emerging or potential applications that exploit electroactive quantum dot-based systems will also be illustrated. © The Royal Society of Chemistry 2012.

Monaco S.,University of Bologna | Semeraro M.,University of Bologna | Tan W.,East China University of Science and Technology | Tian H.,East China University of Science and Technology | And 4 more authors.
Chemical Communications | Year: 2012

Optical or electrochemical excitation of an Ir(iii) cyclometalated complex bearing photochromic and acid-sensitive dithienylethene ligands generates phosphorescence emission that can be switched on/off by light and chemical stimulation. © 2012 The Royal Society of Chemistry.

Ragazzon G.,University of Bologna | Baroncini M.,University of Bologna | Silvi S.,University of Bologna | Silvi S.,Interuniversity Center for the Chemical Conversion of Solar Energy SolarChem | And 5 more authors.
Beilstein Journal of Nanotechnology | Year: 2015

The realization of artificial molecular motors capable of converting energy into mechanical work is a fascinating challenge of nanotechnology and requires reactive systems that can operate away from chemical equilibrium. This article describes the design and construction of a simple, supramolecular ensemble in which light irradiation causes the directional transit of a macrocycle along a nonsymmetric molecular axle, thus forming the basis for the development of artificial molecular pumps. © 2015 Ragazzon et al.

Amelia M.,University of Bologna | Credi A.,University of Bologna | Credi A.,Interuniversity Center for the Chemical Conversion of Solar Energy SolarChem
Inorganica Chimica Acta | Year: 2012

Steady-state and time-resolved luminescence experiments show that, in CHCl 3, Zn(TPP) (TPP = meso-tetraphenylporphyrin) and CdTe nanocrystals of diameter 5.6 nm afford self-assembled complexes in which the fluorescence of the former is quenched and the bandgap luminescence of the latter is sensitized. These results indicate the occurrence of photoinduced energy transfer from the Zn(TPP) donors to the noncovalently bound CdTe acceptors, a phenomenon which is rarely observed for chemically functionalized semiconductor quantum dots. © 2011 Elsevier B.V. All rights reserved.

Di Motta S.,University of Bologna | Di Motta S.,Consortium for Science and Technology of Materials | Avellini T.,University of Bologna | Silvi S.,University of Bologna | And 9 more authors.
Chemistry - A European Journal | Year: 2013

The photophysical properties of a multicomponent [1]rotaxane bearing a β-cyclodextrin ring covalently connected to an axle comprising an azobenzene photoisomerisable moiety and a naphthalimide-type fluorescent stopper are investigated by a combined experimental and computational study. The absorption and fluorescence spectra, and particularly the induced circular dichroism (ICD) signal, are determined. The latter shows a sign relation that cannot be rationalised in terms of the simple general rules commonly employed to analyse the ICD spectra of achiral guests encircled by chiral hosts. To assist the interpretation of experimental results, DFT and time-dependent (TD) DFT calculations are performed to explore the availability of low-energy conformations and to model their spectroscopic response. Molecular dynamics simulations performed in water show the interconversion of a number of conformers, the contribution of which to the ICD signal is in agreement with the observation. The perfect host: Spectroscopic and computational techniques were used to investigate the absorption, luminescence and induced circular dichroism (ICD) spectra of a multicomponent [1]rotaxane. DFT calculations revealed the availability of low-energy conformations that contribute to the observed signal (see figure). The results were compared with those predicted on the basis of established ICD rules for cyclodextrin host-guest complexes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Marchi E.,University of Bologna | Baroncini M.,University of Bologna | Bergamini G.,University of Bologna | Van Heyst J.,University of Bonn | And 3 more authors.
Journal of the American Chemical Society | Year: 2012

A dendrimer bearing two cyclam units linked by an azobenzene moiety, and luminescent naphthalene units at the periphery performs three different functions (light-harvesting, photoisomerization and coordination of metal ions) which can cooperate or interfere depending on the nature of the metal ion. It is thus an example of light controlled molecular tweezers in which Zn(II) coordination allows 100% efficient photosensitization of azobenzene switching, while Cu(II) shuts down azobenzene isomerization. © 2012 American Chemical Society.

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