Papers by Ligia Maria MORETTO
Journal of Archaeological Science: Reports
Powder Technology, Feb 1, 2019
Despite the importance of carbonation in many processes, still the reaction needs investigation. ... more Despite the importance of carbonation in many processes, still the reaction needs investigation. The reaction is essential for the effectiveness of consolidants, based on CaCO 3 forming products, used in stone conservation. Research on carbonation of two calcium alkoxides products, developed during the Nanomatch project, is presented in this paper and the results discussed and compared with those reported with the most used nanolimes. Calcium tetrahydrofurfuryloxide (Ca(OTHF) 2), dissolved in four different solvents, and calcium ethoxide (Ca(OEt) 2), diluted in ethanol, were applied on glass slides and their carbonation kinetics investigated together with their coatings after being kept in uncontrolled and controlled RH conditions (50% and 90%). This allowed to understand the evolution and the phases formed along the process. Carbonation follows the two pathways already reported for alkoxides; it is a quick process and eventually leads to the formation of the most stable crystalline phase (calcite), with high humidity favouring this final step. Alkoxides resulted thus to
Abstract It has been recently demonstrated that chicken egg-yolk immunoglobulin Y (IgY) has many ... more Abstract It has been recently demonstrated that chicken egg-yolk immunoglobulin Y (IgY) has many immunological properties not only on avian, but also on mammalians, such as human [1]. Since it is easy to insulate (directly from egg yolk \u2013 where it is present at a concentration of 10 mg/mL), recently scientists proposed new immunotherapies based on the addiction of IgY to medicine or food both for animals and humans [1]. In addition, eggs are very common ingredients in all diets, so it is important to understand if it is possible to obtain such immunological properties from every day foods, or if IgY degrades during cooking procedures and temperature changes. For this reason, we developed an electrochemical immunosensors based on Au-nanoelectrodes ensemble (NEE) as transducer, able to identify IgY in different matrices. NEEs are prepared via template electroless deposition of gold in a polycarbonate (PC) membrane. Polycarbonate is affine to proteins and antibodies and, for these reason NEEs are very suitable to be used both as electrodes and as protein-receiver material [2]. IgY, the biological molecular recognition element, is immobilized directly on the PC surface of the electrode. It is recognized by the secondary antibody anti-IgY labelled with HRP, an electroactive enzyme that reacts with his substrate (H2O2) and a redox mediator (methylene blue), originating the electrocatalytic cycle. Only the reduction of the oxidated form of methylene blue is an electrochemical reaction, so it is possible to observe an electrocatalytic peak. The proposed immunosensor was tested on different samples, starting from standard IgY, then on analytes collected from yolk or egg-white, and following from more complex food samples containing egg yolk or full cooked eggs. In this communication, the obtained results are presented and discussed
Electrochemistry Communications, 2018
This paper presents a previously unexplored biosensing strategy for detecting gliadin which explo... more This paper presents a previously unexplored biosensing strategy for detecting gliadin which exploits the crosslinking of gliadin with collagen, catalyzed by transglutaminase at the interfacial electron transfer rate, on a modified electrode. The process is monitored by electrochemical impedance spectroscopy using a glassy carbon electrode coated with a collagen layer. To validate the specificity of the response as well as to eliminate possible interferences from other proteins, such as soy protein or casein, the captured gliadin is further reacted with a specific anti-gliadin antibody. Changes in charge transfer resistance, measured from the Nyquist plots, scale linearly with the gliadin concentration in the range 5-20 mg/L, a range suitable for testing the gliadin concentration in glutenfree food commodities.
Chemistry International, Jul 1, 2010
Journal of Nanoscience and Nanotechnology, 2015
3D-ensembles of gold nanowires electrodes (3D-NEEs) are produced by electroless gold deposition i... more 3D-ensembles of gold nanowires electrodes (3D-NEEs) are produced by electroless gold deposition in track-etched polycarbonate (PC) membranes, followed by partial etching (plama or chemical) of the polymeric membrane. These electrodes are applied to the anodic stripping voltammetric determination of inorganic As. The controlled etching of the PC template increased the gold surface area, widening the linear range of the analytical response with respect to ensembles of gold nanodisk electrodes (2D-NEEs). 3D-NEEs prepared using a chemical etching time of 10 s allows the anodic stripping determination of As(III) with a detection limit of 0.08 μg/L and a linear range extended up to 20 μg/L. The speciation of inorganic As (As(III) and (As(V)) in river water is possible by difference between As(III) and total inorganic As, determined after reduction of As(V) with cysteine. The proposed method is successfully validated by comparison with lCP-MS determination.
Lecture Notes in Electrical Engineering, 2015
Pyrolyzed photoresist carbon electrodes (PPCEs) fabricated by photolithographic micro-fabrication... more Pyrolyzed photoresist carbon electrodes (PPCEs) fabricated by photolithographic micro-fabrication and pyrolysis of the epoxy-based photoresist named SU-8 are applied to electroanalysis. Bismuth-modified PPCEs (Bi-PPCEs) are used in the adsorptive cathodic stripping voltammetry (AdCSV) of Ni(II) and in the speciation of inorganic Cr, while PPEs are used in the cyclic voltammetric (CV) study of bilirubin (BR) in dimethyl sulfoxide.
Journal of Electroanalytical Chemistry, 2000
Gold nanoelectrode ensembles (NEEs) have been prepared by using an electroless plating method to ... more Gold nanoelectrode ensembles (NEEs) have been prepared by using an electroless plating method to deposit disk-shaped Au electrode elements (diameter = 38 nm) within the pores of a microporous polycarbonate template membrane. The electrochemistry of three electron-transfer mediators used for biosensors based on reductase enzymes-two phenothiazines (Azure A and B) and methylviologen-were investigated at these NEEs. As has been observed previously, detection limits obtained at the NEE are lower than corresponding detection limits for a Au disk electrode of conventional dimensions (diameter = 3.2 mm, called a macro electrode here). However, the enhancement in the detection limit at the NEE depends on the E 1/2 value of the mediator used. All three of these mediators have more negative E 1/2 values than the redox couples investigated previously at such NEEs. As such, their voltammetric waves are close to the negative limit for Au in the pH 7.4 buffer used as the electrolyte. The effects of background currents, associated with proton reduction, on the detection limits were investigated. At the macro electrode, the voltammograms for the phenothiazines are distorted by adsorption of the reduced forms to the electrode surface. This adsorption process is concentration dependent. The lower detection limits obtained at the NEE allow for the use of lower mediator concentrations, and this unwanted adsorption process can be eliminated at the NEE. Finally, we report here the first use of the NEEs for the determination of standard heterogeneous rates constants.
Electroanalysis, 1995
This review describes principles and analytical applications of ion‐exchange voltammetry (IEV) at... more This review describes principles and analytical applications of ion‐exchange voltammetry (IEV) at polymer modified electrodes. Results of mechanistic studies which are relevant to the development and optimization of IEV methods are discussed. Useful examples of IEV determinations of traces of inorganic and organic electroactive ions of interest for environmental, biomedical or pharmaceutical analysis are given along with future prospects for this technique.
Electroanalysis, 2001
Na®on coated glassy carbon electrodes (NCE) are employed for preconcentrating and detecting Fe 2 ... more Na®on coated glassy carbon electrodes (NCE) are employed for preconcentrating and detecting Fe 2 and Fe 3 cations from aqueous solutions. The in¯uence of the supporting electrolyte composition and of the redox state on the analyte partitioning within the Na®on coating are examined. By using cyclic voltammetry, the ion-exchange voltammetric determination of iron in the mM concentration range is achieved from voltammetric peak currents relevant to the reversible redox process: Fe 3 e @ C Fe 2. Depending on the starting potential of the voltammetric scan, all the iron is initially converted to the Fe(III) or Fe(II) redox state, so that, from the voltammogram, the overall concentration of iron is always obtained. However, the simple measurement of the open circuit potential at the NCE before starting the scan allows one to get information on the ratio between Fe(III) and Fe(II) incorporated in the Na®on coating. From relevant ion-exchange distribution coef®cients, open circuit potential values can be related to the Fe(III)aFe(II) concentration ratio in the sample. The use at the NCE of a new electroanalytical technique named multiple square-wave voltammetry in the double differential mode allows the signi®cative lowering of detection limits pushing the operative range of the method in the nM range. Application to analysis of Fe(II) in the pore-waters of sediments of the lagoon of Venice (Italy) is presented.
Electroanalysis, 1997
Glassy carbon electrodes modified with coatings of poly‐[1‐methyl‐3‐(pyrrol‐1‐ylmethyl)pyridinium... more Glassy carbon electrodes modified with coatings of poly‐[1‐methyl‐3‐(pyrrol‐1‐ylmethyl)pyridinium], poly‐MPP, were prepared by electrochemical oxidation of the suitable monomer in acetonitrile solutions. The anion exchange properties of the coated electrode were exploited in aqueous solutions for preconcentrating and detecting the anionic complex HgCl42−, which is the prevailing inorganic HgII species in seawater and other chloride media. The partition coefficients for the ion‐exchange equilibrium involved were calculated from voltammetric data and compared with those obtained at electrodes coated with Tosflex, a perfluorinated anion exchanger, and poly(vinylpyridine). The selectivity of the poly‐MPP coated electrodes towards the rejection of copper interference was also studied. The optimization of experimental conditions allowed the development of a differential pulse voltammetric method for the determination of submicromolar mercury concentrations with a detection limit of 0.1 nM...
Electroanalysis, 1998
Abstract The results of a study on the determination of trace levels of mercury in natural saltwa... more Abstract The results of a study on the determination of trace levels of mercury in natural saltwaters using screen-printed carbon electrodes modified with Sumichelate Q10R, a chelating resin containing dithiocarbamate groups, which binds mercury strongly and ...
Biosensors and Bioelectronics, 2002
The incorporation and electrochemical behaviour of cytochrome c (Cyt C) at glassy carbon electrod... more The incorporation and electrochemical behaviour of cytochrome c (Cyt C) at glassy carbon electrodes modified with the polyestersulfonated ionomer Eastman AQ 55 are examined. The presence of the polyelectrolytic coating allows the preconcentration of the protein within the polymer and the observation of the direct electrochemistry of Cyt C at the modified electrode without addition of promoters or mediators in the solutions. The dependence of voltammetric signals on typical parameters such as solution pH and nature or concentration of the supporting electrolyte supports the ion-exchange nature of the incorporation process. The relevant role of the permselectivity of the polymeric modifier is highlighted also by the study of electrocatalytic processes which take place at the modified electrode loaded with Cyt C. No electrocatalytic effect is observed when the electrogenerated dication (ferricenylmethyl)trimethylammonium is present as possible oxidant. On the contrary, electrocatalytic current enhancements are observed for anionic substrates such as Fe(CN) 6 3((oxidant) and ascorbate (reductant). Catalytic currents increase with the substrate concentration, with higher sensitivity for Fe(CN) 6 3(. Due to ionic repulsion, the reaction with anions occurs at the polymer Á/ solution interface. In the case of chemically unstable substrates, such as superoxide anion, ionic repulsion slow down the approach rate of the substrate so that spontaneous decomposition can prevail over the reaction with Cyt C incorporated in the coating.
Uploads
Papers by Ligia Maria MORETTO