Marilena Carbone

Carbon nanostructured materials for applications in nano-medicine, cultural heritage, and electrochemical biosensors

This review covers applications of pristine and functionalized single-wall carbon nanotubes (SWCNTs) in nano-medicine, cultural heritage, and biosensors. The physicochemical properties of these engineered nanoparticles are similar to those of ultrafine components of airborne pollution (UF) and might have similar adverse effects. UF may impair cardiovascular autonomic control (inducing a high-risk condition for adverse cardiovascular effects), cause mammalian embryo toxicity, and increase geno-cytotoxic risk. SWCNTs coated with a biopolymer, for example polyethylenimine (PEI), become extremely biocompatible, hence are useful for in-vivo and in-vitro drug delivery and gene transfection. It is also possible to successfully immobilize a human enteric virus on PEI/SWCNT composites, suggesting application as a carrier in non-permissive media. The effectiveness of carbon nanostructured materials in the cleaning, restoration, and consolidation of deteriorated historical surfaces has been widely shown by the use of carbon nanomicelles to remove black dendritic crust from stone surfaces. The nanomicelles, here, have the twofold role of delivery and controlled release of the cleaning agents. The high biocompatibility of functionalized SWCNTs with enzymes and proteins is a fundamental feature used in the assembly of electrochemical biosensors. In particular, a third-generation protoporphyrin IX-based biosensor has been assembled for amperometric detection of nitrite, an environmental pollutant involved in the biodeterioration and black encrustation of historical surfaces.

High-resolution photoemission study of ethanol on Si(100)2×1

The adsorption of ethanol on Si(100)2x1 has been investigated at room temperature by high-resolution synchrotron radiation photoemission, and a consistent picture has been obtained in favour of dissociative adsorption, rom a comparison of the valence band for pure and adsorbed ethanol, which shows the disappearance of sigma(O-H) orbital after adsorption, and from the identification of a Si-O-related component in the Si 2p core spectrum. A lineshape analysis of the Si 2p complex envelope corresponding to different ethanol exposures identifies a second component, which grows with the exposure at a different rate, and is assigned to Si-H bond. The values for relative quantitative ratios among the various components suggest an exposure-dependent adsorption mechanism for ethanol, characterized by the formation of stable Si-O bonds and a high hydrogen surface mobility. The analysis of the C 1s photoemission core-line suggests that no C-O bond rupture occurs, at variance with our previous findings for ethanol adsorption on Si(111)7x7

A low symmetry adsorption state of benzene on Si(111)7 × 7 studied by photoemission and photodesorption

Benzene adsorption on Si(111)7 × 7 has been studied by valuence band and Si2p photoemission and photodesorption. We hypothesize a molecular adsorption of benzene on Si(111)7 × 7, involving simultaneously an adatom and a rest atom in the adsorption process. The assignment of the benzene adsorption features has been made by comparison with gas-phase benzene and with ARUPS spectra of benzene on Si(100)2 × 1. We find that the degenerate orbitals of the e type lose their degeneracy with decrease of symmetry. We suppose that two opposite carbon atoms are involved in the adsorption process, leading to a partial rehybridization of the two carbon atoms from sp2 to sp3 that makes the adsorbate state intermediate between benzene and 1,4 cyclohexadiene. We also observed a high desorption rate of benzene from the silicon surface that shows a weak benzene-silicon bond. D+ is the only ion produced in the Si2p energy range, due to the enhanced production of secondary electrons in correspondence of the ionization threshold.

Palladium (II) and platinum (II) aqueous solutions. Evidence for the solvation of the [PdCl4]2− and [PtCl4]2− ions

Abstract The isomorphic substitution applied to solutions of NH4PtCl4 and NH4PdCl4 allows to show the existence of 2 bound water molecules at the apical sites of PtCl42− and PdCl42− ions. The Pt(Pd)-H2O distance results equal to 2.77 A.

Oxidized graphene in ionic liquids for assembling chemically modified electrodes: a structural and electrochemical characterization study.

Dispersions of graphene oxide (GO) nanoribbons in ionic liquids, ILs (either 1-butyl-3-methylimidazolium chloride (BMIM-Cl-) or 1-butylpyridinium chloride (-Bupy-Cl-)) have been used to assemble modified screen printed electrodes (SPEs). The graphene oxide/ionic liquid dispersions have been morphologically and structurally characterized by the use of several techniques: X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared (FT-IR) spectroscopy, high-resolution-transmission electron microscopy (HR-TEM). The assembled modified SPEs have then been challenged with various compounds and compared to several electro-active targets. In all cases high peak currents were detected, as well as significant potential shifts, especially in the detection of catecholamines and NADH, compared with the bare SPE and the conventional electrodes, such as glassy carbon (GC) and highly oriented pyrolitic graphite (HOPG). This opens the way to the assembly of new types of sensors and biosensors. The enhanced performances observed are attributed to electrocatalytic effects related to the high electrode surface area, to oxygen-assisted electron transfer, as well as to the disordering effect of the ILs, this latter related to the favorable π-π interactions with the ILs and the GO plane.

Graphene oxide nanoribbons (GNO), reduced graphene nanoribbons (GNR), and multi-layers of oxidized graphene functionalized with ionic liquids (GO–IL) for assembly of miniaturized electrochemical devices

In this critical review, new nanomaterials based on graphene (GN) are described, especially those used for the assembly of miniaturized electrochemical transducers. In particular, the physicochemical properties and mechanical features of few layers of graphene (FLGs) are described, as is their use for assembly of chemically modified sensors, biosensors, and immunosensors. The FLGs described here were functionalized by chemical treatment in solution, resulting in oxidized and/or reduced surfaces, edges, and sides. The presence of oxygenated functionality strongly affects the electrocatalysis and the electron-transfer properties of several molecular targets, not only in the solid phase (e.g. in field-effect transistors, FETs) but also in liquid matrices (chemically modified electrodes and biosensors). In addition, “green chemistry” reagents, for example ionic liquids (ILs) can be used for exfoliation and intercalation of graphene planes, to obtain stable and homogeneous nanodispersions. The assembled sensors, biosensors, and immunosensors are extremely useful for electrochemical detection of several electro-active targets of importance in food analysis, environmental monitoring, and clinical diagnosis. A detailed description of each analytical application has been given in this critical review and brief remarks on the emerging disciplines of nanomedicine and nanofoods are also discussed.

Kinetics of gypsum dehydration at reduced pressure : an energy dispersive X-ray diffraction study

Gypsum (CaSO4 center dot 2H(2)O) dehydration kinetics were investigated through energy dispersive X-ray diffraction (EDXD), under reduced pressure (100 Pa), in the temperature range 313-353 K. The process follows the JMAK (Johnson-Mehl-Avrami Kinetic) model. The fitting procedure of the Arrhenius expression provides an activation barrier of 18(2) kcal/mol. Under these experimental conditions, dehydration proceeds via a single-step conversion path gypsum --> gamma-anhydrite. Separate experiments of bassanite (CaSO4 center dot 0.5H(2)O) dehydration, carried out at similar conditions, indicate, as expected, a faster process gamma-anhydrite being the final product. According to the structural relationships between bassanite and gamma-anhydrite, dehydration should occur via the escape of water molecules along the axis of the channel (c axis) following a one-dimensional behaviour. Therefore, no Avrami model (which implies nucleation and growth of a new phase) can be applied.

Gellan hydrogel as a powerful tool in paper cleaning process: a detailed study.

HYPOTHESIS Wet cleaning of ancient papers is one of the most critical steps during a conservation treatment. It is used to improve the optical qualities of a graphic work and remove dust and by-products resulting from cellulose degradation. Nevertheless, washing treatment usually involves a substantial impact on the original morphological structure of paper and can sometimes be dangerous for water sensitive inks and pigments. EXPERIMENTS The use of rigid hydrogel of Gellan gum as an alternative paper cleaning treatment is developed. The application of a rigid hydrogel minimizes damages caused by the use of water, and therefore is much more respectful for the original integrity of ancient paper. FINDINGS Gellan hydrogel has been used to clean paper samples belonging to different centuries (from XVI to XIX) and therefore, characterized by a different story in terms of degradation condition and paper composition. Several techniques, such as high-performance liquid chromatography, Fourier transform infrared spectroscopy, scanning electron microscopy and pH measurements, has been employed to assess the effectiveness and safety of the proposed cleaning method.

Phenol adsorption on Si(111)7×7 studied by synchrotron radiation photoemission and photodesorption

Phenol adsorption on Si(111)7 x 7 has been studied by synchrotron radiation photoemission and photodesorption in the valence band Si 2p energy ranges both at room temperature and at approximate to 50 K. The assignment of the phenol adsorption features has been made by comparison of the gas-phase spectrum. At low exposures the surface rest atoms are selectively quenched, while the adatoms are involved in the adsorption process only for higher exposures. The comparison of the spectra at different temperatures allows us to infer that the adsorption on the rest atoms is molecular. However, the relative intensity of the spectral features changes when different sites are involved in the adsorption process. In particular, the feature attributed to the sigma(O-H) orbital does not increase in intensity. although the other features do, suggesting that the adsorption is dissociative. The photon-stimulated desorption pattern shows a D+ yield in the Si 2p energy range, due to the enhanced production of secondary electrons in correspondence with the ionization threshold, similarly to the system benzene-Si(111)7 x 7

Synchrotron radiation photoemission and photostimulated desorption of deuterated methanol on Si(111)7 × 7 and Si(100)2 × 1

Abstract Deuterated methanol adsorption on Si(111)7 × 7 and Si(100)2 × 1 surfaces has been investigated, at room temperature, by synchrotron radiation photoemission and photostimulated desorption. Photoemission experiments as a function of methanol coverage show that deuterated methanol adsorption is dissociative on both surfaces and occurs via б O-D bond breakage and б SiO bond formation. Site selectivity is displayed by the methoxy species on Si(111)7 × 7 surface, since t S2 surface state related to the rest atoms is quickly quenched upon low coverage adsorption. The S1 surface state is quenched only subsequently at much higher coverages. The photostimulated desorption pattern is similar for the two surfaces and strongly depends on the investigated energy range. D+ is always the most abundant ion produced, but higher mass fragments are present too in the energy range including the C 1s threshold, where multiple desorption processes are possibly taking place.