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.

Modified electrodes with metal or metal oxides nanoparticles are particularly appealing to improve sensor performances and fabricate miniaturized devices, as required also in glucose detection. A Pt electrode modified by drop casting of a novel nanostructured film based on silver nanoparticles (Ag-NPs) capped in a commercial nontoxic polyvinyl alcohol (PVA) matrix is proposed here as a valid alternative to classical glucose (bio)sensors. The extensive electrochemical and spectroscopic characterization by X-ray Photoelectron Spectroscopy (XPS) of this advanced nanomaterial is presented to study its response to glucose and to investigate the chemical nature of deposited Ag.

A non-enzymatic amperometric sensor for glucose detection based on a Pt electrodemodified with Te microtubes (Te-MTs), by direct drop casting of Te-MTs dispersed in ethanol, is proposed. The spectroscopic characterization of as synthesized Te-MTs and Pt/Te-MTsmodified electrodes was performed by scanning electronmicroscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Moreover electrochemical characterization of Pt/Te-MTs modified electrodes was performed by Cyclic Voltammetry (CV) and Cronoamperometry (CA) in phosphate buffer (pH=7 I=0.2). Electrochemical results indicate that the proposed sensor exhibits very strong and sensitive amperometric responses to glucose and explains a good anti-interference ability.

The analysis reported in thiswork has been performed to characterise PM10concentrationmeasured in an urban background site in Lecce (Apulia region, Italy). PM10 concentration and its inorganic chemical composition have been studied using three procedures: a qualitative analysis of the correlation coefficients between the different species and of the crustal enrichment factor; the cluster analysis (CA) and the principal component analysis (PCA). The results of the three procedures are in good agreement. The five groups identified by the CA correspond to the five principal components obtained with the PCA and they reflect the results qualitatively inferred using the two-species correlation coefficients. The CA results helped in putting in evidence a correlation between Ni, V and sulphate that was less evident in the PCA. The relative abundance of V is larger with wind fromtheNNWdirectionswhere themain industrial sites of the region are located. This suggests the presence of anthropogenic inorganic secondary aerosol generated by a common source of V and SO2 that are likely the industrial releases and the ship emissions. The absolute PCA (APCA) allowed the quantitative apportionment of the five components observed: crustal matter (49.5%), secondary inorganic aerosol (24.1%), marine aerosol (6.3%), traffic (16.5%), and industrial (2.1%). Observed PM10 concentration clearly shows a seasonal pattern, opposite to the one observed in the northern and central Italy, with average PM10 larger in the warm season (spring and summer) with respect to the cold season as a consequence of the increase of crustal matter contribution likely due to the intrusion of African dust. These intrusions are more frequent in the warm season and have an influence on daily PM10 concentrations variable between 6% and 120% in this site. Correlation with meteorological data indicates that the more intense cases of intrusions of African dust happen with wind blowing from the SW direction. Average PM10 concentration decreases of about 23% during precipitation. The decrease ismainly due to the decrease in crustal matter contribution and secondary inorganic aerosol. The sum of the other three sources is almost not changing during precipitation.

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.

Abstract: This paper describes the evaluation of the oxidative potential of atmospheric aerosol, for the PM2.5 and PM10 size fractions, using the DTT assay. This is an indicator related with oxidative stress of particulate matter (PM) leading to potential health effects. Measured DTT activity has been correlated with aerosol concentrations and with the content of carbonaceous species on collected samples. The oxidative potential of PM associated to natural sources during Saharan Dust and sea-spray advection events is investigated and compared with non-event days.

The present work describes the preparation and the characterization of a composite nanomaterial obtained by the electrochemical deposition of copper nanoparticles (CuNPs) on an electrosynthesized film of poly-3-methylthiophene (P3MT). Copper electrodeposition was achieved by applying a potential pulse program both on Pt and on screen-printed electrodes (SPEs). The microscopic characterization of the composite film by scanning electron microscopy (SEM) suggested that the applied pulse width is correlated to the amount of the deposited particles but it does not influence CuNPs size. The nanocomposite was analyzed also by X-ray Photoelectron Spectroscopy (XPS) confirming the influence of the pulse width on the amount of electrodeposited copper and evidencing the presence of Cu(I) and Cu(II) species in each sample. For a comparison, CuNPs were prepared from solutions of both CuCl2 and Cu(ClO4)2. XPS analysis evidenced the stabilizing effect of Cl− ions on CuNPs promoting their entrapment in P3MT film also when the composite film is exposed to carrier solution in a flow system, contrarily to what observed in the presence of ClO4− ions. Performed electrochemical tests showed that CuNPs/P3MT exhibited a remarkable electrocatalytic activity for glucose oxidation. The composite film deposited on SPEs was successfully used for glucose electrochemical detection in a flow system. The effect of the applied potential and of the flow rate of carrier stream was evaluated: under the selected optimal condition the composite film exhibited a satisfactory response in terms of detection limit, linear range and repeatability. The sensitivity of CuNPs/P3MT to other compounds (ascorbic acid, uric acid, sorbitol, fructose, dopamine) was verified evidencing that the proposed system could be effectively used as an electrochemical detector coupled to a chromatographic system for the simultaneous detection of biomolecules.

ABSTRACT 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.

Abstract Deep eutectic solvents (DESs) are emerging as a new class of green solvents with the potential to replace organic solvents in several fundamental and applied processes. In this work, we offer an unprecedented characterization of the behavior of the bacterial photosynthetic reaction center (RC) from Rhodobacter sphaeroides in a series of choline chloride based DESs. RC is a membrane-spanning three-subunit pigment protein complex that, upon illumination, is capable of producing a stable charge-separated state. Thus, it represents the ideal model for carrying out basic studies of protein solvent interactions. Herein, we first report that, in many DES mixtures investigated, RC (a) is stable, (b) is capable of generating the charge-separated state, and (c) is even able to perform its natural photocycle. It proved, indeed, to be effective in reducing quinone molecules to quinol by withdrawing electrons from cytochrome c. As an example of biotechnological application, a photoelectrochemical cell based on DES-dissolved RC has also been designed and successfully employed to generate photocurrents arising from the reduction of the electron-donor ferrocenemethanol.

The development of an amperometric biosensor for herbicide detection, using bacterial reaction centers (RC) as biorecognition element, is presented. RC immobilization on gold screen printed electrodes was achieved by LIFT, a powerful physisorption-based immobilization technique that enhances the intimate contact between the protein and the electrode surface. As a result, stable photocurrents driven by direct electron transfer at the donor side were observed, both in the presence and in the absence of a quinone substrate in solution. The addition of quinone UQ(0) increased the photocurrents, while the UQ(0)-free system showed higher sensitivity to the herbicide terbutryn, a model inhibitor, acting as photocurrent attenuator. In spite of its simple design, the performances achieved by our mediatorless device are comparable or superior to those reported for analogous RC-based photoelectrochemical cells, in terms of both terbutryn sensing and photocurrent generation.

Abstract View references (51) Exposure to atmospheric particulate matter (PM) leads to adverse health effects although the exact mechanisms of toxicity are still poorly understood. Several studies suggested that a large number of PM health effects could be due to the oxidative potential (OP) of ambient particles leading to high concentrations of reactive oxygen species (ROS). The contribution to OP of specific anthropogenic sources like road traffic, biomass burning, and industrial emissions has been investigated in several sites. However, information about the OP of natural sources are scarce and no data is available regarding the OP during Saharan dust outbreaks (SDO) in Mediterranean regions. This work uses the a-cellular DTT (dithiothreitol) assay to evaluate OP of the water-soluble fraction of PM2.5 and PM10 collected at an urban background site in Southern Italy. OP values in three groups of samples were compared: standard characterised by concentrations similar to the yearly averages; high carbon samples associated to combustion sources (mainly road traffic and biomass burning) and SDO events. DTT activity normalised by sampled air volume (DTTV), representative of personal exposure, and normalised by collected aerosol mass (DTTM), representing source-specific characteristics, were investigated. The DTTV is larger for high PM concentrations. DTTV is well correlated with secondary organic carbon concentration. An increased DTTV response was found for PM2.5 compared to the coarse fraction PM2.5-10. DTTV is larger for high carbon content samples but during SDO events is statistically comparable with that of standard samples. DTTM is larger for PM2.5 compared to PM10 and the relative difference between the two size fractions is maximised during SDO events. This indicates that Saharan dust advection is a natural source of particles having a lower specific OP with respect to the other sources acting on the area (for water-soluble fraction). OP should be taken into account in epidemiological studies to evaluate the potential health risks associated to ROS in regions affected by high pollution events due to Saharan dust advection.

In this work a new original amperometric sensor forH2O2 detection based on a Pt electrode modified with Te-microtubes was developed. Te-microtubes, synthesized by the simple thermal evaporation of Te powder, have a tubular structure with a hexagonal cross-section and are open ended. Modified electrode was prepared by direct drop casting of the mixture of Te-microtubes dispersed in ethanol on Pt surface. The spectroscopic characterization of synthesized Te-microtubes and Pt/Te-microtubes modified electrodes was performed by scanning electron microscopy (SEM), energy-dispersive X-rays microanalysis (EDX), X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS). Moreover a complete electrochemical characterization of the new composite material Pt/Te-microtubes was performed by cyclic voltammetry (CV) and cronoamperometry (CA) in phosphate buffer solution (PBS) at pH 7. Electrochemical experiments showed that the presence of Te-microtubes on modified electrode was responsible for an increment of both cathodic and anodic currents in presence of H2O2 with respect to bare Pt. Specifically, data collected from amperometric experiments at −150mV vs. SCE in batch and −200mV vs. SCE in flow injection analysis (FIA) experiments show a remarkable increment of the cathodic current. The electrochemical performances of tested sensors make them suitable for the quantitative determination of H2O2 substrate both in batch and in FIA.

A simple and novel amperometric biosensor for glucose detection is proposed. It is based on the immobilization of glucose oxidase (GOx) in a poly(vinyl alcohol) (PVA) matrix directly drop casted on a platinum electrode surface (Pt/GOx-PVA). Glucose was determined in the absence of a mediator used to transfer electrons between the electrode and the enzyme. The correlation between peak current (ip) and scan rate has been verified and the effect of pH solution has been checked. Glucose detection has been performed amperometrically at 400 mV by using pulsed amperometric detection (PAD). Under the selected optimal conditions, the biosensor showed low detection limit (10 mM), wide dynamic range (0.1–37 mM) and high sensitivity. The biosensor amperometric response revealed it to be specific to glucose without significant interference from other sugars and electroactive species coexisting with glucose in biological fluids. Response stability was another interesting feature of the developed system as it was almost completely recovered when the biosensor was left in opportune storage conditions (i.e., a response decrease of only 13% after 35 days in air at room temperature). Finally, X-Ray Photoelectron Spectroscopy (XPS) characterization revealed a homogeneous film deposited on the Pt substrate whose structure is also preserved under operative conditions.

Aptamers are chemically produced oligonucleotides, able to bind a variety of targets such as drugs, proteins and pathogens with high sensitivity and selectivity. Therefore, aptamers are largely employed for producing label-free biosensors (aptasensors), with significant applications in diagnostics and drug delivery. In particular, the anti-thrombin aptamers are biomolecules of high interest for clinical use, because of their ability to recognize and bind the thrombin enzyme. Among them, the DNA 15-mer aptamer (TBA), has been widely explored around the possibility of using it in aptasensors. This paper proposes a microscopic model of the electrical properties of TBA and of the aptamer-thrombin complex, combining information from both structure and function, following the issues addressed in an emerging branch of electronics known as proteotronics. The theoretical results are compared and validated with measurements reported in the literature. Finally, the model suggests resistance measurements as a novel tool for testing aptamer-target affinity.

Abstract An electronic structure analysis of two nickel(II) tetrapyrrole complexes bearing beta-alkylthio substituents, NiOMTP and NiOETPz, has been carried out through a combination of high-resolution XPS experiments and DFT calculations. The Ni 2p XPS spectra show a 0.5 eV shift to higher energy of the Ni 2p(3/2) and Ni 2p(1/2) binding energies on going from the porphyrin to the porphyrazine complex. This shift, which is well-reproduced by relativistic spin-orbit ZORA calculations, is indicative of a depletion of electron density on the central metal. Such a depletion of electron density is related to the macrocycle-induced changes in the metal-ligand interactions. In the porphyrazine complex both the ligand to metal sigma donation and the metal to ligand p-back donation increase. The latter increases slightly more than the former, however, leading to a decrease of electron density on the central metal.

Abstract The kinetics of electrochemical deposition of copper particles from Cu2+ solution on platinum and poly-3-methylthiophene modified platinum electrode was studied in potentiostatic conditions in presence of Cl- anions. The complex behavior of current transients suggests that the deposition process involves several stages with different kinetics. Results obtained on platinum show that after an initial adsorption process, the copper deposition is accomplished through two different models: a three-dimensional nucleation and growth under diffusive control (3DPD model) and a progressive nucleation and two-dimensional growth (2DP model). The analysis of current transients recorded on platinum poly-3-methylthiophene modified electrode (Pt/PMT) shows a very different behavior. On Pt modified electrode a process of growth related to a semi-infinite diffusion to a planar surface was accompanied by two different mechanisms of nucleation and growth: a three-dimensional nucleation and growth with no diffusive control (3DP model) and an instantaneous nucleation with two-dimensional growth (2DP model)

Human olfactory 17-40 and Bacteriorhodopsin are two protein receptors that received particular attention in electronics, due to the possibility of implementing nano-biodevices able to detect odours and light and thus useful for medical and green energy harvesting applications. Some recent experiments concerning the electrical responses of these receptors are reviewed. Data are interpreted in the framework of a new science exploiting the complexity in biology and biomedical engineering called proteotronics. In particular, the single protein is modelled as an impedance network whose topological properties affect the electrical response as measured by experiments.

Abstract Reaction of octakis(ethylthio) porphyrazine (H(2)OESPz) with FeBr2 in ClCH2CH2OH at 135 degrees C affords the 2-chloroethoxy-iron(III)-(ethylthio)porphyrazine, (ClCH2CH2O)Fe(III)OESPz, (LFe(III)OESPz) in good yield. The spectroscopic, redox, and coordination properties of the complex and its mu-oxo dimer derivative, [Fe(III)OESPz](2)O, are investigated and compared to those of the iron(III) porphyrin analogs.

ABSTRACT 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 analysis 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 (R2 = 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 5 s and possessed good reproducibility. These results indicate that Pt/TeO2-NWs composite is suitable to be used as material for sensing applications.

A bstract The determination of the oxidation state and structural role of transition metals in minerals is a crucial challenge. XPS has proven to have a great potential in probing the site distribution and chemical states of Fe and Ti transition elements, provided that the right method to process the spectra is used. XPS spectra of these elements have the 2p core level region usually rich of features but the choice of the method for background removing can seriously affect the results of the quantitative analysis. Single crystals of brookite (TiO2) and natural micas (phlogopites) are investigated to examine the effect of background subtraction on Ti2p and Fe2p signals. The backgrounds used are: the “Linear” background; the traditional “Shirley” background; three different Tougaard-like backgrounds; and the more recent “shape parameter, κ” method. In the case of the studied natural micas, the Fe chemical state proportion (Fe2+/Fetot) obtained with the corrected spectra varies by 10%. It is shown that TiO2 oxides are not suitable as standard for octahedral Ti4+ signal in the studied micas. The “shape parameter, κ” method proves to provide supplementary information useful for a full interpretation of XPS signals.

A novel flow cell capable of improving piezoelectric response in system combining Electrochemical Quartz Crystal Microbalance (EQCM) and Flow Injection Analysis is presented. The original design of flow cell modified in shape and position of ports compared to other models for QCM is proposed. Electrochemical and viscoelastic experiments showed focusing of the sample in the central zone between ports and a remarkable enhancement of mass sensitivity compared to Sauerbrey value. Enhancement of mass sensitivity may allow piezoelectric device to be applied to the same concentration range of electrochemical ones and may be used as a tool to develop electrochemical sensors.

Abstract Surface chemical composition of particles has a key role in determining the reactivity and optical properties of atmospheric aerosol. This composition depend on the particles sources and formation processes and it influences human health and climate. In this work, the X-ray photoelectron spectroscopy (XPS) has been used for the systematic surface characterization of atmospheric particles of different sizes, collected using a 10-stage MOUDI-II rotating cascade impactor in an urban background site. The high resolution XPS spectra allowed to distinguish different organic functional groups (C-C/CC, -C-O, -CO/-C(O)N, -C(O)O, C-O3=) and to speciate the detectable hetero-elements, sulphur (S-O42-, sulphone and sulphide compounds), nitrogen (N-H4+, N-O3-, N-O2- and organic-nitrogen compounds), sodium (Na+) and chlorine (Cl-) species. Significant differences in particles belonging to accumulation (small particles) and coarse (large particles) modes were observed being due to the formation processes and sources from which particles originated. The oxygen concentrations is inversely correlated with carbon concentrations, however, the content of oxidized organic carbon is not correlated with oxygen content confirming that the oxygen increment observed in large particles can likely be attributed to the contribution of inorganic species (crustal origin). The speciation of nitrogen showed ammonium only in the accumulation mode and nitrate only in coarse mode excluding the presence of ammonium nitrate of secondary origin in the area studied. A correlation of Na and Cl was attributed to the marine contribution with an excess of Cl on the surface correlated with the depletion of Cl observed in the bulk of particles. © 2015 Elsevier Ltd.