Foto del docente

Alberto Credi

Professor

Department of Industrial Chemistry "Toso Montanari"

Academic discipline: CHIM/03 General and Inorganic Chemistry

Research

Keywords: nanoscience molecular motor binary logic dendrimer molecular machine catenane luminescence nanoparticle metal complex electrochemistry quantum dot molecular device nanotechnology rotaxane supramolecular chemistry photochemistry

The leitmotiv of the scientific activity of Alberto Credi is the design and photophysical, photochemical and electrochemical investigation of molecular and supramolecular systems capable of performing useful functions and that, as such, can be viewed as examples of devices and machines at the molecular level. Three main themes can be identified:

1. Artificial molecular machines and motors

This research line deals with the design, synthesis and study of multicomponent species (in most cases rotaxanes, catenanes and related species) capable of performing mechanical motions of their molecular components in response to external stimulation (addition of chemical reactants, application of electric potentials, light irradiation). The investigations are focussed on the use of light as an energy source, and on the possibility of developing systems that can operate autonomously far from equilibrium by dissipating the external energy input. The aim is the construction of mechanical nanodevices that can carry out useful functions such as control of membrane permeability, uptake and release of other molecules, up to mechanical actuation on the micro- and macroscopic scales (molecular muscles).

 

2. Molecular and supramolecular systems for information processing
The objective of this research line is the development of chemical sistems capable of gathering, processing and storing information. Such activities are part of the “bottom up” approach to miniaturization, which is expected to enable the costruction of nanoscale devices not achievable by the current “top down” technologies. The bottom up approach should not only lead to smaller and more powerful computers, but also to new technologies capable of revolutionizing medicine, producing a wealth of new materials, providing new energetic resources and solving environmental problems. Among the examined systems are molecular switches, wires, plug/socket devices, extension cables, memories and logic circuits.

 

3. Synthesis and study of the photophysical, photochemical and electrochemical properties of complex molecular species, nanoparticles and materials
The objective of this research line is to increase the basic knowledge on the physicochemical properties of molecules, supermolecules, and nanoparticles. The investigated topics are: thermodynamic and kinetic aspects of self-assembly reactions of host-guest systems, photoisomerization processes in azobenzene-type species, photophysical and redox behaviour of organic molecules and metal complexes, photocatalytic properties of titania nanostructured surfaces, photophysical and redox behaviour of inorganic nanoparticles and their interaction with molecular species, light-induced control of the physicochemical properties of photoreactive materials.



The research themes are devoted to the design and construction of supramolecular species capable of performing predetermined useful functions. These studies are of fundamental importance in the rapidly growing fields of nanoscience and nanotechnology, in reference to the “bottom-up” approach for the realization of functional structures of nanometer size.

The objectives of the presented research topics are:

1. Devise and characterize supramolecular species in which some molecular components can be moved with respect to others in response to suitable external stimulation. Devices of this kind are currently the subject of great interest and are referred to as molecular machines. The stimuli employed to make such machines work are of chemical, electrochemical, and photochemical nature. Promising supermolecules in this regard are pseudorotaxanes, rotaxanes, catenanes and related species, host-guest systems, dendrimers.

2. Devise and investigate molecular and supramolecular systems capable of delivering output signals in response to specific input signals, in order to mimick the binary logic functions performed in electronic circuits. Among the targeted systems are host-guest complexes, rotaxanes, dendrimers, metal complexes, electrochromic and photochromic species, multistate-multifunctional systems.

3. Design and realize supramolecular species that can collect, transmit, store and process light signals. Devices of this type are, e.g., molecular antennas, wires, plug-socket and extension systems, charge-separation devices, multistate-multifunctional species. Such studies are of crucial importance in view of the construction of devices for the conversion of solar energy into chemical energy, as well as ultraminiaturized devices for information processing (chemical computers). To this purpose, dendrimers, host-guest systems, rotaxanes, polynuclear metal complexes, photochromic systems can be identified as suitable chemical species.

A common objective of these research topics is to move from solution studies to the characterization of systems deposited on surfaces and at interfaces, in the attempt of realizing an “interfacement” between the molecular and the macroscopic world. Such aspect can be explored with the attachment of the investigated supramolecular species to nanostructured (e.g. nanoparticles) or macroscopic (e.g. electrodes) surfaces by exploiting, for example, the self-assembled monolayer and Langmuir-Blodgett techniques.

In order to obtain supramolecular species that can perform predetermined functions, that is, having desired chemical, photochemical and electrochemical properties, the strict cooperation between researchers in different branches of chemistry (synthetic chemists, physical chemists) and in other fields (materials science, physics, biochemistry, engineering, computer science) is of fundamental importance. The methods that will be most commonly employed for the characterization of the compounds, their components and model species are steady state absorption and luminescence spectroscopic techniques. Time resolved spectroscopic techniques (laser flash photolysis, phase-modulation shift, time-correlated single-photon counting, stopped-flow methods) will also be used with the purpose of investigating the dynamics of the processes induced by photonic, electrochemical or chemical stimulation. These measurements will be complemented by voltammetric and spectroelectrochemical experiments with both conventional and ultramicro-electrodes. Computer simulations of the experimental data (voltammetric curves, kinetic traces, titration data, etc.) will be performed in order to determine the mechanism and the relevant parameters of the examined processes.

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