Daniela Chirizzi

A novel nonenzymatic amperometric hydrogen peroxide sensor based on CuO@Cu2O nanowires embedded into poly(vinyl alcohol).

A new, very simple, rapid and inexpensive nonenzymatic amperometric sensor for hydrogen peroxide (H2O2) detection is proposed. It is based on the immobilization of cupric/cuprous oxide core shell nanowires (CuO@Cu2O-NWs) in a poly(vinyl alcohol) (PVA) matrix directly drop casted on a glassy carbon electrode surface to make a CuO@Cu2O core shell like NWs PVA embedded (CuO@Cu2O-NWs/PVA) sensor. CuO nanowires with mean diameters of 120-170nm and length in the range 2-5μm were grown by a simple catalyst-free thermal oxidation process based on resistive heating of pure copper wires at ambient conditions. The oxidation process of the copper wire surface led to the formation of a three layered structure: a thick Cu2O bottom layer, a CuO thin intermediate layer and CuO nanowires. CuO nanowires were carefully scratched from Cu2O layer with a sharp knife, dispersed into ethanol and sonicated. Then, the NWs were embedded in PVA matrix. The morphological and spectroscopic characterization of synthesized CuO-NWs and CuO@Cu2O-NWs/PVA were performed by transmission electron microscopy (TEM), selected area diffraction pattern (SAD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. Moreover a complete electrochemical characterization of these new CuO@Cu2O-NWs/PVA modified glassy carbon electrodes was performed by Cyclic Voltammetry (CV) and Cronoamperometry (CA) in phosphate buffer (pH=7; I=0.2) to investigate the sensing properties of this material against H2O2. The electrochemical performances of proposed sensors as high sensitivity, fast response, reproducibility and selectivity make them suitable for the quantitative determination of hydrogen peroxide substrate in batch analysis.

Te oxide nanowires as advanced materials for amperometric nonenzymatic hydrogen peroxide sensing.

A new nonenzymatic platinum Te oxide nanowires modified electrode (Pt/TeO2-NWs) for amperometric detection of hydrogen peroxide (H2O2) is proposed. The modified electrode has been developed by direct drop casting, with TeO2 nanowires (TeO2-NWs), synthesized by thermal evaporation of Te(0) in an oxygen atmosphere. The morphological and spectroscopic characterization of the TeO2-NWs as synthesized on Pt foil was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. XPS and XRD analyses are especially involved to gain information on the chemical environment of TeO2-NWs in contact with Pt surface. Moreover electrochemical characterization of these new modified Pt/TeO2-NWs modified electrodes was performed by Cyclic Voltammetry (CV) and Cronoamperometry (CA) in phosphate buffer (pH=7; I=0.2) to investigate the sensing properties of this material against H2O2. The proposed sensor exhibits a wide linear and dynamic range from 2 µM to 16 mM (R(2)=0.9998) and the detection limit is estimated to be 0.6 µM (S/N=3). Moreover, this sensor shows a rapid amperometric response time of less than 5s and possessed good reproducibility. These results indicate that Pt/TeO2-NWs composite is suitable to be used as material for sensing applications.

Development and characterization of a novel bioactive polymer with antibacterial and lysozyme-like activity

The development and characterization of a novel bioactive polymer based on the immobilization of glucose oxidase enzyme (GOx) in a polyvinyl alcohol (PVA) film showing antibacterial activity is presented. The PVA‐GOx composite material was extensively characterized by UV‐vis, X‐ray Photoelectron (XPS) spectroscopy and by Fourier Transform Infrared (FTIR) spectroscopy to verify the preservation of enzyme structural integrity and activity. The antimicrobial activity of this composite material against Escherichia coli and Vibrio alginolyticus was assessed. Furthermore the lysozyme‐like activity of PVA‐GOx was highlighted by a standard assay on Petri dishes employing Micrococcus lysodeikticus cell walls. The findings from this study have implications for future investigations related to the employment of PVA‐GOx system as a composite material of pharmaceutical and technological interest.

Phosphate Modified Screen Printed Electrodes by LIFT Treatment for Glucose Detection

The design of new materials as active layers is important for electrochemical sensor and biosensor development. Among the techniques for the modification and functionalization of electrodes, the laser induced forward transfer (LIFT) has emerged as a powerful physisorption method for the deposition of various materials (even labile materials like enzymes) that results in intimate and stable contact with target surface. In this work, Pt, Au, and glassy carbon screen printed electrodes (SPEs) treated by LIFT with phosphate buffer have been characterized by scanning electron microscopy and atomic force microscopy to reveal a flattening effect of all surfaces. The electrochemical characterization by cyclic voltammetry shows significant differences depending on the electrode material. The electroactivity of Au is reduced while that of glassy carbon and Pt is greatly enhanced. In particular, the electrochemical behavior of a phosphate LIFT treated Pt showed a marked enrichment of hydrogen adsorbed layer, suggesting an elevated electrocatalytic activity towards glucose oxidation. When Pt electrodes modified in this way were used as an effective glucose sensor, a 1–10 mM linear response and a 10 µM detection limit were obtained. A possible role of phosphate that was securely immobilized on a Pt surface, as evidenced by XPS analysis, enhancing the glucose electrooxidation is discussed.

Electrocatalytic Activity of α-MoO 3 Plates Synthesized Through Resistive Heating Route

Characterization and electrochemical application of α-MoO3 hierarchical plates achieved through direct resistive heating of molybdenum foils, at ambient pressure and in absence of templates or catalysts, has been reported. The plates with an orthorhombic single-crystalline structure, as observed by SEM, TEM, SAD and Raman-scattering techniques. They are about 100–200 nm in thickness and a few tens micrometers in length. Electrochemical characterization of α-MoO3 plates casted on Pt electrodes was performed by Cyclic Voltammetry in phosphate buffer to investigate the properties of this material against methanol oxidation. Reported results indicate that α-MoO3/Pt devices were suitable to promote the electroxidation of methanol in sensing and/or fuel cell anodes development applications.

Characterization of hierarchical α-MoO3 plates toward resistive heating synthesis: electrochemical activity of α-MoO3/Pt modified electrode toward methanol oxidation at neutral pH

The growth of MoO3 hierarchical plates was obtained by direct resistive heating of molybdenum foils at ambient pressure in the absence of any catalysts and templates. Plates synthesized after 60 min resistive heating typically grow in an single-crystalline orthorhombic structure that develop preferentially in the [001] direction, and are characterized by high resolution transmission electron microscopy, selected area diffraction pattern and Raman-scattering measurements. They are about 100-200 nm in thickness and a few tens of micrometers in length. As heating time proceeds to 80 min, plates of α-MoO3 form a branched structure. A more attentive look shows that primary plates formed at until 60 min could serve as substrates for the subsequent growth of secondary belts. Moreover, a full electrochemical characterization of α-MoO3 plates on platinum electrodes was done by cyclic voltammetric experiments, at pH 7 in phosphate buffer, to probe the activity of the proposed composite material as anode to methanol electro-oxidation. Reported results indicate that Pt MoO3 modified electrodes are appropriate to develop new an amperometric non-enzymatic sensor for methanol as well as to make anodes suitable to be used in direct methanol fuel cells working at neutral pH.

Development and Characterization of a Novel Antibacterial Material Based on GOx Immobilized in a PVA Film

The development and characterization of a novel antibacterial material based on glucose oxidase (GOx) immobilized in a polyvinyl alcohol (PVA) film was proposed. This system acts in the presence of glucose to generate by-products as oxygen species (H2O2, ·O2 −, OH) that are well-known endogenous and exogenous toxic products for microbes in vivo (Miller and Britigan, Clin Microb R10: 1–18, 1997). The PVA/GOx composite material has been extensively characterized by X-ray photoelectron (XPS) spectroscopy, Fourier transform infrared (FTIR), and UV-visible spectroscopy (UV–vis) to verify the preservation of the enzyme structural integrity and of the enzymatic activity in PVA membrane. The antibacterial lysozyme-like activity of PVA/GOx was evaluated by a standard assay on Petri dishes employing Micrococcus lysodeikticus dried cell walls.

Spectroscopic Characterization of a New Antibacterial Material for Sensing Applications

A novel antibacterial system based on immobilization of glucose oxidase enzyme (GOx) in a poly(vinyl alcol) (PVA) film was proposed. The GOx/PVA composite material has been extensively characterized by UV-vis and X-ray photoelectron (XPS) spectroscopy to verify the preservation of the enzyme structural integrity and of the enzymatic activity in PVA membrane. Moreover, XPS characterization was used to analyze the chemistry of GOx/PVA composite film. The antibacterial lysozyme-like activity of GOx/PVA was evaluated by a standard assay on Petri dishes employing Micrococcus luteus cell walls. Thus the findings from this study have implications for future investigations related to employment of GOx/PVA as a compound of pharmaceutical and technological interest.

A New Potentiometric Urea Biosensor Based on Urease Immobilized in Electrosyntesised Poly( O -Phenylenediamine)

A potentiometric urea biosensor based on urease (Ur) electrochemical immobilisation by poly(o-phenylenediamine) (PPD) is proposed. Polymer films have been grown by cyclic voltammetry on a glassy carbon (GC) electrode, using an unconventional “upside-down” (UD) geometry. GC/Ur-PPD electrodes exhibit a rapid (5–10 s) and sensitive response to urea concentration and lifetime of at least 5 weeks. Work is in progress to optimise the sensor and study its behaviour in the presence of possible interferences.