The scientific activity has been reported in 170 papers on International Journals, about 80 Invited Lectures at International Conferences and Schools (see paragraph 3 below), about 250 oral and poster presentations in International Conferences (separate lists available). G.Marletta has lectured in Academic and Industrial Institutions in many Countries, including USA, Germany, France, UK, Japan, Spain, Sweden, Belgium, Hungary, Brasil, China, India, Mexico, Canada and Italy. G.Marletta has coedited 11 volumes on topics including Materials for Photonics, Ion Beam effects in Materials, Current Trends in Nanotechnology, Biofunctional Surfaces, etc…
Particle Beams-Matter Interactions (keV-MeV ions in polymers) (1981 – 2002)
The study of the interaction of energetic particles with materials has formed the first phase of the scientific activity of G.Marletta. The research activity in this field was launched under the leading idea that fast particles would produce a non-conventional chemistry, due to the presumably non-thermodynamical fragmentation of molecular compounds occurring when fast particles interact with (covalently bonded) matter. Thus, following an interdisciplinary approach between chemistry and physics, the work of G.Marletta demonstrated that the energy deposition mechanisms, schematically consisting in mostly collisional or mostly electronic energy-deposition events, more than the total dose of released energy, are the main driving factor for the particle-induced chemistry. The basic works of G.Marletta in this field also demostrated that the non-thermodynamical fragmentation of molecular systems is basically associated to the collisional events (i.e., cascades of impulse-transfer events), and that irradiation performed optimizing this energy deposition regime promotes the formation of new non-conventional phases with unusual chemical and physical properties. Last, but not least, G.Marletta could set a general framework for the analysis of the radiation-matter interaction, showing that all the possible events occur between the two limiting situations of the non-thermodynamical collision cascades and the “photochemical” conventional regime. These achievements have formed the basis for the development of Surface Engineering methodologies, based on the use of low-energy particles, of very wide application to modify relevant properties of surfaces and thin films, such as insulator-semiconducting and –conducting transitions in polymers, polymer/polymer and polymer/metal adhesion switch-on, membrane properties of polymers, biocompatibility and cell adhesion, etc… The results have been widely recognized by the concerned communities of materials scientists, as it is demonstrated, among the others, by the cooptation of G.Marletta in the International Steering Boards of several International Conferences. Finally, more than 40 Invited Lectures have been asked to G.Marletta on his results in the field of Radiation-Polymer Interactions.
Interaction of biological systems with synthetic surfaces (1996 – present)
The interest for biologically relevant systems was boosted by collaborations focusing the role of living tissues in the degradation of polymer prosthesis . The achievements obtained by G.Marletta in the understanding and driving the interaction of biosystems with surfaces were initially originated by the original approach based on the use of low energy (inert) ion beams to directly patterning micrometric regions of polymer surfaces, inducing a spatially resolved enhanced cell adhesion as well as specific protein adsorption and reorientation processes. The success of the proposed methodology has been pervasive and the dramatic enhancement of biocompatibility has been demonstrated for several irradiated polymeric surfaces. Moreover, the cell behavior on polymeric surfaces undergoing many different irradiation conditions has been extensively studied, allowing also to shed light on the cell response to specific changes in surface properties. The initial approach, focusing on the nature and properties of the irradiation-induced surface phases, has further prompted the development of a number of new ideas on the role of specific surface factors that may affect the organization of protein adsorbed layers, including clustering at surfaces, as well as their “orientation”, i.e., the topological facts of their biological functionality. A combined experimental and computational approach has been employed to unravel the basic features of the processes at surfaces. Also in this case, a largely interdisciplinary research effort has been necessary to elucidate the role of biomolecule adsorbing processes in promoting specific cellular response. Thus, the role of factors like surface free energy, including the balance between dispersive and polar terms, presence of electrical domains and specific chemical groups has been studied in some detail and the relationship with the phenomenological cell response has been identified. The trend of development of this line implies both the increase of the interdisciplinary approach, as far as more focused cellular biology skills are needed to relate the expression of specific messengers (proteins, enzymes and RNA) in view of the surface factors, as well as the development of nanoscale structured surfaces, the last point taking profit of the researches developed under line 3, summarized below.
Nanotechnology, molecular surfaces and thin films (1999 – present)
The development of this research line is the natural follow-up of the concepts of specificity/selectivity of the interactions developed in the research line dealing with the biosystem response to the surfaces, interpreted as stimuli-provider systems. Thus, the line has been self-developing, expanding the current views on surface nanopatterning, setting a general methodology to create nanopores in polymeric films, studying the potentialities of Langmuir-Blodgett films as self-patterning systems and focusing the problem of the organization of thin and ultrathin polymeric films as a function of the substrate properties. A library of nanoscale methodology has been developed, as the enabling step to achieve nano-organised functional and biofunctional systems. Thus, also new functionalization methodologies have also been developed, based on selective coordination-based anchoring processes onto inorganic surfaces an, the functional properties of hybrid nanocomposites, formed by polymer-metal multilayers, with typical thicknesses between 4-6 nm, or polymer/fullerene nanostructures are being focused.