The performance of polyacrylic coatings as barrier films against corrosion of titanium-based orth... more The performance of polyacrylic coatings as barrier films against corrosion of titanium-based orthopaedic implants was investigated. In particular, poly(methyl methacrylate) (PMMA) was electrosynthesized on titanium substrates by electro-reductive processes from aqueous monomer solutions. The obtained PMMA coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of an annealing treatment on the morphology of coatings with respect to uniformity and porosity of films was assessed by scanning electron microscopy (SEM). An inductively coupled plasma-mass spectrometry (ICP-MS) technique was used for ion concentration measurements in ion release tests performed on TiAlV sheets modified with PMMA coatings (annealed and unannealed). Results indicated that the annealing process produces coatings with considerable anticorrosion performances.
Direct on-target plate processing of small (ca. 100 μg) fragments of paint samples for MALDI-MS i... more Direct on-target plate processing of small (ca. 100 μg) fragments of paint samples for MALDI-MS identification of lipid-and protein-based binders is described. Fragments were fixed on a conventional stainless steel target plate by colloidal graphite followed by in situ fast tryptic digestion and matrix addition. The new protocol was first developed on paint replicas composed of chicken egg, collagen, and cow milk mixed with inorganic pigments and then successfully applied on historical paint samples taken from a fifteenth century Italian panel painting. The present work contributes a step forward in the simplification of binder identification in very small paint samples since no conventional solvent extraction is required, speeding up the whole sample preparation to 10 min and reducing lipid/protein loss.
A matrix-assisted laser desorption ionization time-of-flight mass spectrometry-based approach was... more A matrix-assisted laser desorption ionization time-of-flight mass spectrometry-based approach was applied for the detection of various lipid classes, such as triacylglycerols (TAGs) and phospholipids (PLs), and their oxidation by-products in extracts of small (50-100 μg) samples obtained from painted artworks. Ageing of test specimens under various conditions, including the presence of different pigments, was preliminarily investigated. During ageing, the TAGs and PLs content decreased, whereas the amount of diglycerides, short-chain oxidative products arising from TAGs and PLs, and oxidized TAGs and PLs components increased. The examination of a series of model paint samples gave a clear indication that specific ions produced by oxidative cleavage of PLs and/or TAGs may be used as markers for egg and drying oil-based binders. Their elemental composition and hypothetical structure are also tentatively proposed. Moreover, the simultaneous presence of egg and oil binders can be easily and unambiguously ascertained through the simultaneous occurrence of the relevant specific markers. The potential of the proposed approach was demonstrated for the first time by the analysis of real samples from a polyptych of Bartolomeo Vivarini (fifteenth century) and a "French school" canvas painting (seventeenth century).
Mass transfer in catalyst supports"and "reactive sites"are two critical factors for supported thi... more Mass transfer in catalyst supports"and "reactive sites"are two critical factors for supported thin film catalysts. Based on such considerations, paper composed of cellulose fibers (CFs) is chosen as a competent nano-catalyst carrier because its broad porous structure is conducive to mass transfer. Then a facile aquatic synergistic synthesis is developed to decorate polypyrrole (PPy) encapsulated palladium nano-composites onto the CF paper structures. The pyrrole monomers (Py) reduce Pd 2þ to Pd nanoparticles in aqueous solution, and meanwhile the Pd 2þ initiates the polymerization of Py to PPy. In the as-prepared composite paper catalysts, the broad pores constructed by the microfibers facilitate the reactant diffusion and the Pd/PPy nanoparticles supported on the fibers provide more reactive sites for catalysis. As a result, the catalytic activity for hydrolysis of ammonia borane is improved. The H 2 turnover frequency is 21.1 mol H 2 mol Pd À1 min À1 , surpassed most other Pd based film catalysts. Importantly, excellent stability and reproducibility are also realized by the immobilization of Pd NPs by PPy layers onto fibers.
With the aim of developing a polymeric multilayer film for application in advanced biomaterials, ... more With the aim of developing a polymeric multilayer film for application in advanced biomaterials, as a first step poly(pyrrole-3-carboxylic acid) films (abbreviated as PPy-3-carbox) were electropolymerised from pyrrole-3-carboxylic acid solutions by cyclic voltammetry and chronoamperometry on platinum, titanium and Ti90Al6V4 substrates and characterised both electrochemically (cyclic voltammetry) and spectroscopically (X-Ray Photoelectron Spectroscopy, XPS). Electrochemical experiments showed that the potential range adopted for electropolymerization affects the polymer electroactivity, by analogy with unsubstituted polypyrrole. The combination of conventional and chemical derivation-XPS provided information on PPy-3-carbox surface structure, showing no significant difference between films grown on different substrates and an increase of the COOH groups amount (one group over three pyrrole rings, as an average) with respect to unsubstituted polypyrrole (PPy), as expected. Finally, a preliminary Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) investigation was performed in order to get further information on the polymer structure and electroactivity.
A stony sculptural composition of the Nativity Scene is preserved in Altamura’s Cathedral (Apulia... more A stony sculptural composition of the Nativity Scene is preserved in Altamura’s Cathedral (Apulia, Italy). This commonly called Apulian “presepe”, attributed to an unknown stonemason, is composed of polychrome carbonate white stone sculptures. While earlier stratigraphic tests have unveiled a complex superimposition of painting layers—meaning that several editions of the sculptures succeeded from the 16th to 20th century—a chemical investigation intended to identify the organic binding media used in painting layers was undertaken. Drawing on current literature, two strategies were exploited: a non-invasive in situ digestion analysis and an approach based on micro-removal of painting film followed by the Bligh and Dyer extraction protocol. Both peptide and lipid mixtures were analyzed by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and reversed-phase liquid chromatography coupled to mass spectrometry by electrospray ionization (RPLC-ESI-MS). Attenuated tot...
A Functional Bio-Interlayer Organic Field-Effect Transistor (FBI-OFET) sensor, embedding a strept... more A Functional Bio-Interlayer Organic Field-Effect Transistor (FBI-OFET) sensor, embedding a streptavidin protein capturing layer, capable of performing label-free selective electronic detection of biotin at 3 part per trillion (mass fraction) or 15 pM, is proposed here. The response shows a logarithmic dependence spanning over 5 orders of magnitude of analyte concentration. The optimization of the FBI analytical performances is achieved by depositing the capturing layer through a controllable Layer-by-Layer (LbL) assembly, while an easy processable spin-coating deposition is proposed for potential low-cost production of equally highly performing sensors. Furthermore, a Langmuirian adsorption based model allows rationalizing the analyte binding process to the capturing layer. The FBI-OFET device is shown to operate also with an antibody interlayer as well as with an ad hoc designed microfluidic system. These occurrences, along with the proven extremely high sensitivity and selectivity, open to FBI-OFETs consideration as disposable electronic strip-tests for assays in biological fluids requiring very low detection limits.
With the aim of developing a polymeric multilayer film for application in advanced biomaterials, ... more With the aim of developing a polymeric multilayer film for application in advanced biomaterials, as a first step poly(pyrrole-3-carboxylic acid) films (abbreviated as PPy-3-carbox) were electropolymerised from pyrrole-3-carboxylic acid solutions by cyclic voltammetry and chronoamperometry on platinum, titanium and Ti90Al6V4 substrates and characterised both electrochemically (cyclic voltammetry) and spectroscopically (X-Ray Photoelectron Spectroscopy, XPS). Electrochemical experiments showed that the potential range adopted for electropolymerization affects the polymer electroactivity, by analogy with unsubstituted polypyrrole. The combination of conventional and chemical derivation-XPS provided information on PPy-3-carbox surface structure, showing no significant difference between films grown on different substrates and an increase of the COOH groups amount (one group over three pyrrole rings, as an average) with respect to unsubstituted polypyrrole (PPy), as expected. Finally, a preliminary Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) investigation was performed in order to get further information on the polymer structure and electroactivity.
Proceedings of the National Academy of Sciences, 2012
Biosystems integration into an organic field-effect transistor (OFET) structure is achieved by sp... more Biosystems integration into an organic field-effect transistor (OFET) structure is achieved by spin coating phospholipid or protein layers between the gate dielectric and the organic semiconductor. An architecture directly interfacing supported biological layers to the OFET channel is proposed and, strikingly, both the electronic properties and the biointerlayer functionality are fully retained. The platform bench tests involved OFETs integrating phospholipids and bacteriorhodopsin exposed to 1-5% anesthetic doses that reveal drug-induced changes in the lipid membrane. This result challenges the current anesthetic action model relying on the so far provided evidence that doses much higher than clinically relevant ones (2.4%) do not alter lipid bilayers' structure significantly. Furthermore, a streptavidin embedding OFET shows label-free biotin electronic detection at 10 parts-per-trillion concentration level, reaching state-of-the-art fluorescent assay performances. These examples show how the proposed bioelectronic platform, besides resulting in extremely performing biosensors, can open insights into biologically relevant phenomena involving membrane weak interfacial modifications.
Ir,(CO),, is deposited on silica by wet impregnation. Upon a subsequent thermal treatment, redist... more Ir,(CO),, is deposited on silica by wet impregnation. Upon a subsequent thermal treatment, redistribution on the surface and physisorption of the cluster occur. This species is thoroughly characterised and used as catalyst for isomerisation of 1,s cyclooctadiene (I,5 cod) to the I,4 and 1,3 isomers.
Copperpolypyrrole (CuPPy) composites have been synthesised following an all-electrochemical pro... more Copperpolypyrrole (CuPPy) composites have been synthesised following an all-electrochemical procedure comprising the deposition of a thin PPy film and the subsequent pulsed potentiostatic deposition of copper from a CuCl 2 solution. Surface and bulk characterisation of the ...
Journal of Electron Spectroscopy and Related Phenomena, 1995
Polypyrrole electrosynthesised from aqueous solutions has been investigated by XPS, both in the c... more Polypyrrole electrosynthesised from aqueous solutions has been investigated by XPS, both in the conducting (PPY) and in the so-called overoxidised (PPYox) state. An accurate analysis of high resolution spectra, including cross-checking between the independent ...
Journal of Electron Spectroscopy and Related Phenomena, 1999
The paper reviews some significant pieces of work carried out in the authors' laboratory in the c... more The paper reviews some significant pieces of work carried out in the authors' laboratory in the course of about three decades and concerned with the development of market oriented devices, which exploit the singular characteristics of electrosynthesised polymers. The strategic role of X-Ray Photoelectron Spectroscopy is underlined not only as a powerful technique for the characterization of these thin films, but mainly as an unvaluable tool to feedback optimization procedures both in film synthesis and modification. Case studies relevant to the development of permselective membranes for biosensors, of biocompatible coatings and active layers for gas sensors have been selected and reviewed. Future trends and prospects of the work in progress are also described.
Palladium-polypyrrole nanostructured composite films can be easily synthesised using a two-step p... more Palladium-polypyrrole nanostructured composite films can be easily synthesised using a two-step procedure comprising the electrochemical synthesis of palladium nanoparticles (Pd-NPs) that are subsequently potentiostatically deposited onto a polypyrrole thin film electrosynthesised from an acetonitrile solution. The composite thin films have good conductivity and their transmission electron micrographs show that the metallic inclusions have a mean diameter of about 5 nm with a homogeneous size distribution. X-ray photoelectron spectroscopy (XPS) analysis reveals the presence of two surface oxidation states for the as-synthesised Pd-NPs as well as for those deposited on the films. On the basis of experimental findings, a structural model for the Pd-NPs is proposed.
A low-density lipoprotein (LDL) modified gold electrode was designed as an evaluation model of an... more A low-density lipoprotein (LDL) modified gold electrode was designed as an evaluation model of antioxidative properties of two phenol-like compounds: a-tocopherol (a-toc) and t-butyl-hydroxyanisole (BHA). Two sources of free radicals [2,2'-azobis(2-amidinopropane) dihydrochloride and H 2 O 2 ] were used to induce the lipoprotein oxidation and the ™antioxidant potentiality∫ of the phenol-like compounds on LDL oxidative process is reported. Two series of experiments were performed by using antioxidants either in solution or co-immobilized on the gold electrode within the LDL layer. When dissolved in solution, a-toc ensures a better LDL preservation than BHA; when coimmobilized, a-toc shows a prooxidant behavior, while BHA exhibits an efficient antioxidant action.
ABSTRACT A systematic spectroscopic and morphological characterization of gold−fluoropolymer (CFx... more ABSTRACT A systematic spectroscopic and morphological characterization of gold−fluoropolymer (CFx(Au)) nanocomposites, deposited by ion beam cosputtering, is presented. These composites are technologically relevant, since they exhibit vapor-sensing properties based on swelling phenomena. Analysis by X-ray photoelectron spectroscopy (XPS) allows us to assess that gold codeposition induces a progressive defluorination of the polymeric chains, leading to a significant increase of the polymer chains' branching and of the concentration of unsaturated fluorinated carbons. The presence of a fluoride peak in the F 1s spectrum proves the formation of polar gold fluorides. Transmission electron microscopy reveals the presence of in-plane homogeneously distributed nanosized gold domains, while angle-resolved X-ray photoelectron spectroscopy indicates a nonhomogeneous in-depth distribution of the gold particles, with the outer surface being less rich in nanoparticles. Results derived from the analytical characterization allow a deeper understanding of the swelling phenomena involved in the sensing processes.
Titanium and its alloys are widely used in load-bearing implants as a result of their excellent m... more Titanium and its alloys are widely used in load-bearing implants as a result of their excellent mechanical properties and corrosion resistance. In order to improve their performances with respect to osseointegration, the use of bioactive coatings has been suggested. Polypyrrole (PPy) has been chosen as coating polymer because of its ability to be electrochemically grown directly onto metallic substrates, of any shape and dimension, leading to remarkably adherent overlayers. This polymer, in addition to protecting the metal implant against corrosion, could be surface modified with biologically active molecules able to stimulate positive interactions with bone tissue. In this work, PPy electrosynthesis on both titanium and Ti-Al-V substrates has been investigated. The chemical composition and the morphology of the polymeric films, deposited under different conditions, were evaluated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively.
The performance of polyacrylic coatings as barrier films against corrosion of titanium-based orth... more The performance of polyacrylic coatings as barrier films against corrosion of titanium-based orthopaedic implants was investigated. In particular, poly(methyl methacrylate) (PMMA) was electrosynthesized on titanium substrates by electro-reductive processes from aqueous monomer solutions. The obtained PMMA coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of an annealing treatment on the morphology of coatings with respect to uniformity and porosity of films was assessed by scanning electron microscopy (SEM). An inductively coupled plasma-mass spectrometry (ICP-MS) technique was used for ion concentration measurements in ion release tests performed on TiAlV sheets modified with PMMA coatings (annealed and unannealed). Results indicated that the annealing process produces coatings with considerable anticorrosion performances.
Direct on-target plate processing of small (ca. 100 μg) fragments of paint samples for MALDI-MS i... more Direct on-target plate processing of small (ca. 100 μg) fragments of paint samples for MALDI-MS identification of lipid-and protein-based binders is described. Fragments were fixed on a conventional stainless steel target plate by colloidal graphite followed by in situ fast tryptic digestion and matrix addition. The new protocol was first developed on paint replicas composed of chicken egg, collagen, and cow milk mixed with inorganic pigments and then successfully applied on historical paint samples taken from a fifteenth century Italian panel painting. The present work contributes a step forward in the simplification of binder identification in very small paint samples since no conventional solvent extraction is required, speeding up the whole sample preparation to 10 min and reducing lipid/protein loss.
A matrix-assisted laser desorption ionization time-of-flight mass spectrometry-based approach was... more A matrix-assisted laser desorption ionization time-of-flight mass spectrometry-based approach was applied for the detection of various lipid classes, such as triacylglycerols (TAGs) and phospholipids (PLs), and their oxidation by-products in extracts of small (50-100 μg) samples obtained from painted artworks. Ageing of test specimens under various conditions, including the presence of different pigments, was preliminarily investigated. During ageing, the TAGs and PLs content decreased, whereas the amount of diglycerides, short-chain oxidative products arising from TAGs and PLs, and oxidized TAGs and PLs components increased. The examination of a series of model paint samples gave a clear indication that specific ions produced by oxidative cleavage of PLs and/or TAGs may be used as markers for egg and drying oil-based binders. Their elemental composition and hypothetical structure are also tentatively proposed. Moreover, the simultaneous presence of egg and oil binders can be easily and unambiguously ascertained through the simultaneous occurrence of the relevant specific markers. The potential of the proposed approach was demonstrated for the first time by the analysis of real samples from a polyptych of Bartolomeo Vivarini (fifteenth century) and a "French school" canvas painting (seventeenth century).
Mass transfer in catalyst supports"and "reactive sites"are two critical factors for supported thi... more Mass transfer in catalyst supports"and "reactive sites"are two critical factors for supported thin film catalysts. Based on such considerations, paper composed of cellulose fibers (CFs) is chosen as a competent nano-catalyst carrier because its broad porous structure is conducive to mass transfer. Then a facile aquatic synergistic synthesis is developed to decorate polypyrrole (PPy) encapsulated palladium nano-composites onto the CF paper structures. The pyrrole monomers (Py) reduce Pd 2þ to Pd nanoparticles in aqueous solution, and meanwhile the Pd 2þ initiates the polymerization of Py to PPy. In the as-prepared composite paper catalysts, the broad pores constructed by the microfibers facilitate the reactant diffusion and the Pd/PPy nanoparticles supported on the fibers provide more reactive sites for catalysis. As a result, the catalytic activity for hydrolysis of ammonia borane is improved. The H 2 turnover frequency is 21.1 mol H 2 mol Pd À1 min À1 , surpassed most other Pd based film catalysts. Importantly, excellent stability and reproducibility are also realized by the immobilization of Pd NPs by PPy layers onto fibers.
With the aim of developing a polymeric multilayer film for application in advanced biomaterials, ... more With the aim of developing a polymeric multilayer film for application in advanced biomaterials, as a first step poly(pyrrole-3-carboxylic acid) films (abbreviated as PPy-3-carbox) were electropolymerised from pyrrole-3-carboxylic acid solutions by cyclic voltammetry and chronoamperometry on platinum, titanium and Ti90Al6V4 substrates and characterised both electrochemically (cyclic voltammetry) and spectroscopically (X-Ray Photoelectron Spectroscopy, XPS). Electrochemical experiments showed that the potential range adopted for electropolymerization affects the polymer electroactivity, by analogy with unsubstituted polypyrrole. The combination of conventional and chemical derivation-XPS provided information on PPy-3-carbox surface structure, showing no significant difference between films grown on different substrates and an increase of the COOH groups amount (one group over three pyrrole rings, as an average) with respect to unsubstituted polypyrrole (PPy), as expected. Finally, a preliminary Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) investigation was performed in order to get further information on the polymer structure and electroactivity.
A stony sculptural composition of the Nativity Scene is preserved in Altamura’s Cathedral (Apulia... more A stony sculptural composition of the Nativity Scene is preserved in Altamura’s Cathedral (Apulia, Italy). This commonly called Apulian “presepe”, attributed to an unknown stonemason, is composed of polychrome carbonate white stone sculptures. While earlier stratigraphic tests have unveiled a complex superimposition of painting layers—meaning that several editions of the sculptures succeeded from the 16th to 20th century—a chemical investigation intended to identify the organic binding media used in painting layers was undertaken. Drawing on current literature, two strategies were exploited: a non-invasive in situ digestion analysis and an approach based on micro-removal of painting film followed by the Bligh and Dyer extraction protocol. Both peptide and lipid mixtures were analyzed by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and reversed-phase liquid chromatography coupled to mass spectrometry by electrospray ionization (RPLC-ESI-MS). Attenuated tot...
A Functional Bio-Interlayer Organic Field-Effect Transistor (FBI-OFET) sensor, embedding a strept... more A Functional Bio-Interlayer Organic Field-Effect Transistor (FBI-OFET) sensor, embedding a streptavidin protein capturing layer, capable of performing label-free selective electronic detection of biotin at 3 part per trillion (mass fraction) or 15 pM, is proposed here. The response shows a logarithmic dependence spanning over 5 orders of magnitude of analyte concentration. The optimization of the FBI analytical performances is achieved by depositing the capturing layer through a controllable Layer-by-Layer (LbL) assembly, while an easy processable spin-coating deposition is proposed for potential low-cost production of equally highly performing sensors. Furthermore, a Langmuirian adsorption based model allows rationalizing the analyte binding process to the capturing layer. The FBI-OFET device is shown to operate also with an antibody interlayer as well as with an ad hoc designed microfluidic system. These occurrences, along with the proven extremely high sensitivity and selectivity, open to FBI-OFETs consideration as disposable electronic strip-tests for assays in biological fluids requiring very low detection limits.
With the aim of developing a polymeric multilayer film for application in advanced biomaterials, ... more With the aim of developing a polymeric multilayer film for application in advanced biomaterials, as a first step poly(pyrrole-3-carboxylic acid) films (abbreviated as PPy-3-carbox) were electropolymerised from pyrrole-3-carboxylic acid solutions by cyclic voltammetry and chronoamperometry on platinum, titanium and Ti90Al6V4 substrates and characterised both electrochemically (cyclic voltammetry) and spectroscopically (X-Ray Photoelectron Spectroscopy, XPS). Electrochemical experiments showed that the potential range adopted for electropolymerization affects the polymer electroactivity, by analogy with unsubstituted polypyrrole. The combination of conventional and chemical derivation-XPS provided information on PPy-3-carbox surface structure, showing no significant difference between films grown on different substrates and an increase of the COOH groups amount (one group over three pyrrole rings, as an average) with respect to unsubstituted polypyrrole (PPy), as expected. Finally, a preliminary Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) investigation was performed in order to get further information on the polymer structure and electroactivity.
Proceedings of the National Academy of Sciences, 2012
Biosystems integration into an organic field-effect transistor (OFET) structure is achieved by sp... more Biosystems integration into an organic field-effect transistor (OFET) structure is achieved by spin coating phospholipid or protein layers between the gate dielectric and the organic semiconductor. An architecture directly interfacing supported biological layers to the OFET channel is proposed and, strikingly, both the electronic properties and the biointerlayer functionality are fully retained. The platform bench tests involved OFETs integrating phospholipids and bacteriorhodopsin exposed to 1-5% anesthetic doses that reveal drug-induced changes in the lipid membrane. This result challenges the current anesthetic action model relying on the so far provided evidence that doses much higher than clinically relevant ones (2.4%) do not alter lipid bilayers' structure significantly. Furthermore, a streptavidin embedding OFET shows label-free biotin electronic detection at 10 parts-per-trillion concentration level, reaching state-of-the-art fluorescent assay performances. These examples show how the proposed bioelectronic platform, besides resulting in extremely performing biosensors, can open insights into biologically relevant phenomena involving membrane weak interfacial modifications.
Ir,(CO),, is deposited on silica by wet impregnation. Upon a subsequent thermal treatment, redist... more Ir,(CO),, is deposited on silica by wet impregnation. Upon a subsequent thermal treatment, redistribution on the surface and physisorption of the cluster occur. This species is thoroughly characterised and used as catalyst for isomerisation of 1,s cyclooctadiene (I,5 cod) to the I,4 and 1,3 isomers.
Copperpolypyrrole (CuPPy) composites have been synthesised following an all-electrochemical pro... more Copperpolypyrrole (CuPPy) composites have been synthesised following an all-electrochemical procedure comprising the deposition of a thin PPy film and the subsequent pulsed potentiostatic deposition of copper from a CuCl 2 solution. Surface and bulk characterisation of the ...
Journal of Electron Spectroscopy and Related Phenomena, 1995
Polypyrrole electrosynthesised from aqueous solutions has been investigated by XPS, both in the c... more Polypyrrole electrosynthesised from aqueous solutions has been investigated by XPS, both in the conducting (PPY) and in the so-called overoxidised (PPYox) state. An accurate analysis of high resolution spectra, including cross-checking between the independent ...
Journal of Electron Spectroscopy and Related Phenomena, 1999
The paper reviews some significant pieces of work carried out in the authors' laboratory in the c... more The paper reviews some significant pieces of work carried out in the authors' laboratory in the course of about three decades and concerned with the development of market oriented devices, which exploit the singular characteristics of electrosynthesised polymers. The strategic role of X-Ray Photoelectron Spectroscopy is underlined not only as a powerful technique for the characterization of these thin films, but mainly as an unvaluable tool to feedback optimization procedures both in film synthesis and modification. Case studies relevant to the development of permselective membranes for biosensors, of biocompatible coatings and active layers for gas sensors have been selected and reviewed. Future trends and prospects of the work in progress are also described.
Palladium-polypyrrole nanostructured composite films can be easily synthesised using a two-step p... more Palladium-polypyrrole nanostructured composite films can be easily synthesised using a two-step procedure comprising the electrochemical synthesis of palladium nanoparticles (Pd-NPs) that are subsequently potentiostatically deposited onto a polypyrrole thin film electrosynthesised from an acetonitrile solution. The composite thin films have good conductivity and their transmission electron micrographs show that the metallic inclusions have a mean diameter of about 5 nm with a homogeneous size distribution. X-ray photoelectron spectroscopy (XPS) analysis reveals the presence of two surface oxidation states for the as-synthesised Pd-NPs as well as for those deposited on the films. On the basis of experimental findings, a structural model for the Pd-NPs is proposed.
A low-density lipoprotein (LDL) modified gold electrode was designed as an evaluation model of an... more A low-density lipoprotein (LDL) modified gold electrode was designed as an evaluation model of antioxidative properties of two phenol-like compounds: a-tocopherol (a-toc) and t-butyl-hydroxyanisole (BHA). Two sources of free radicals [2,2'-azobis(2-amidinopropane) dihydrochloride and H 2 O 2 ] were used to induce the lipoprotein oxidation and the ™antioxidant potentiality∫ of the phenol-like compounds on LDL oxidative process is reported. Two series of experiments were performed by using antioxidants either in solution or co-immobilized on the gold electrode within the LDL layer. When dissolved in solution, a-toc ensures a better LDL preservation than BHA; when coimmobilized, a-toc shows a prooxidant behavior, while BHA exhibits an efficient antioxidant action.
ABSTRACT A systematic spectroscopic and morphological characterization of gold−fluoropolymer (CFx... more ABSTRACT A systematic spectroscopic and morphological characterization of gold−fluoropolymer (CFx(Au)) nanocomposites, deposited by ion beam cosputtering, is presented. These composites are technologically relevant, since they exhibit vapor-sensing properties based on swelling phenomena. Analysis by X-ray photoelectron spectroscopy (XPS) allows us to assess that gold codeposition induces a progressive defluorination of the polymeric chains, leading to a significant increase of the polymer chains' branching and of the concentration of unsaturated fluorinated carbons. The presence of a fluoride peak in the F 1s spectrum proves the formation of polar gold fluorides. Transmission electron microscopy reveals the presence of in-plane homogeneously distributed nanosized gold domains, while angle-resolved X-ray photoelectron spectroscopy indicates a nonhomogeneous in-depth distribution of the gold particles, with the outer surface being less rich in nanoparticles. Results derived from the analytical characterization allow a deeper understanding of the swelling phenomena involved in the sensing processes.
Titanium and its alloys are widely used in load-bearing implants as a result of their excellent m... more Titanium and its alloys are widely used in load-bearing implants as a result of their excellent mechanical properties and corrosion resistance. In order to improve their performances with respect to osseointegration, the use of bioactive coatings has been suggested. Polypyrrole (PPy) has been chosen as coating polymer because of its ability to be electrochemically grown directly onto metallic substrates, of any shape and dimension, leading to remarkably adherent overlayers. This polymer, in addition to protecting the metal implant against corrosion, could be surface modified with biologically active molecules able to stimulate positive interactions with bone tissue. In this work, PPy electrosynthesis on both titanium and Ti-Al-V substrates has been investigated. The chemical composition and the morphology of the polymeric films, deposited under different conditions, were evaluated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively.
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Papers by L. Sabbatini