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.

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 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.

The electrochemical behavior of bisphenol A (BPA) was studied on poly(3,4-ethylenedioxythiophene) (PEDOT)-modified glassy carbon electrodes by cyclic voltammetry. It was observed that BPA oxidation on PEDOT film produced a BPA polymer (pBPA) showing excellent redox activity with anodic and cathodic peaks at 0.15 and 0.01 V, respectively; the former being evaluated for BPA electrochemical sensing. The amount of deposited pBPA has been estimated by electrochemical and spectroscopic analysis by X-ray photoelectron spectroscopy. The effect of scan rate and pH on the oxidation of pBPA film has been studied. The oxidation current was found to vary linearly with BPA concentration in the range 90–410 μM, and a detection limit of 55 μM was evaluated. Results of BPA amperometric detection have also been collected by using a repetitive potential step program to give a linear response to BPA in the concentration range 40–410 μM with a detection limit of 22 μM and a sensitivity of 1.57 μAμM−1cm−2. The developed sensor showed satisfactory reproducibility and anti-interference properties and was successfully applied to BPA determination in mineral water samples.

The electrochemical synthesis of a metal complex based molecularly imprinted polymer (MIP) has been applied to the development of an electrochemical sensor for a chlorophenoxy carboxylic acid (4-(2,4- dichlorophenoxy)butyric acid (2,4-DB)) commonly used as pesticide. MIP has been electrosynthesized on a platinum electrode by using a Co-porphyrin (Co(III)tetrakis(o-aminophenyl) porphyrin) as functional monomer. The entrapment of the template in polymeric matrix after polymerization was verified by FTIR experiments. Washing protocol has been investigated by studying the effect of different solvents as well as of the exposure time to washing mixture by XPS analysis. Under selected conditions almost the total amount of the withdrawn template was removed. An interaction mechanism between MIP and template was hypothesized on the basis of XPS data. The imprinting effect was verified by comparing electrochemical responses of MIP and not-imprinted polymer (NIP) tested by cyclic voltammetry between −0.1 and −1.7V (vs Ag/Ag+ 0.1M in ACN) and at a constant potential (−1.8V vs Ag/Ag+ 0.1M in ACN). In both cases MIP revealed an enhanced electrocatalytic activity towards 2,4-DB reduction. Amperometric MIP response revealed to be particularly satisfactory in terms of linear range (200M–2mM), sensitivity (5.89AmM−1), reproducibility (RSD 17%) and time-stability. Moreover, MIP-based electrodes evidenced a good selectivity against both pesticides and structurally related compounds with a total removal of interference coming from chlorophenols.

A novel imprinting scheme, combining for the first time electropolymerization with metal-ion coordination, has been proposed. A MIP for a pesticide (4-(2,4-dichlorophenoxy)butyric acid (2,4-DB)) has been prepared from a Co-porphyrin (Co(III)tetrakis(o-aminophenyl) porphyrin (CoTAPP)) as functional monomer. Such an approach aims to combine advantages of electropolymerization with ones related to the use of metal complexes in imprinting procedures. After verification of template entrapment and subsequent removal by XPS spectroscopy, the imprinting effect was verified by comparing electrochemical responses of MIP and not-imprinted polymer (NIP) tested by Cyclic Voltammetry (CV). MIP revealed an enhanced electrocatalytic activity towards 2,4-DB reduction as well as a good selectivity against both pesticides and structurally related compounds.

The development of an electrosynthesized imprinted polypyrrole (PPY) film onto a platinum sheet as sorbent phase for a fluoroquinolone antibiotic (levofloxacin) is described. Experimental conditions for the electropolymerization of PPY in the presence of the template were optimized. The molecularly imprinted polymer (MIP) film was characterized by X-Ray Photoelectron Spectroscopy (XPS) to verify the template entrapment in the polymeric matrix. After being subject to washing procedures, MIP was analyzed by XPS and a very satisfactory template removal was estimated being equal to 83%. The effectiveness of washing protocol was assessed also by UV–vis and High Performance Liquid Chromatography (HPLC) analysis of corresponding washing solutions. Rebinding experiments were performed by exposing the imprinted PPY film to levofloxacin solutions, subsequently analyzed by HPLC. The effect of solvent and time of exposure was investigated. The imprinting effect was verified by comparing recognition abilities of both MIP and not imprinted polymer (a polymer prepared in the same conditions but in the absence of the template).

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.

This review highlights the importance of coupling molecular imprinting technology with methodology based on electrochemical techniques for the development of advanced sensing devices. In recent years, growing interest in molecularly imprinted polymers (MIPs) in the preparation of recognition elements has led researchers to design novel formats for improvement of MIP sensors. Among possible approaches proposed in the literature on this topic, we will focus on the electrosynthesis of MIPs and on less common hybrid technology (e.g. based on electrochemistry and classical MIPs, or nanotechnology). Starting from the early work reported in this field, an overview of the most innovative and successful examples will be reviewed.

A simple synthesis was applied and tested for the preparation of boron-doped titanium dioxide [TiO2(B)] nanocrystals using titanium tetraisopropoxide (TTIP) together with boric acid (H3BO3) and benzyl alcohol as reaction solvent. Changes in the TTIP/H3BO3 molar ratio allowed a scalable synthetic protocol with a significant B-dopant control. In particular, this approach does not need surfactants or a final calcination step. X-ray diffractometry (XRD), low- and high-resolution transmission electron microscopy (TEM and HRTEM), and micro Raman spectroscopy revealed that the TiO2 nanocrystals produced have diameters up to about 10 nm and are mainly of the anatase phase but that a brookite phase was progressively formed with increased dopant level. The amount of boron was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the presence of boron inside the crystals was determined by 11B cross-polarized magic-angle spinning nuclear magnetic resonance (11B CP-MAS NMR) spectroscopy. X-ray photoelectron spectroscopy (XPS) revealed the presence of boron on the nanocrystal surfaces, confirming the trend in the dopant concentration already observed with ICP-AES elemental analysis. Microphotoluminescence studies indicated the formation of three different typical luminescent defect states in correlation with the amount of added boron in the titania. UV/Vis absorption spectra showed a boron-dependent redshift of the absorption edge.

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)

A simple and novel potentiometric biosensor for urea detection was prepared by employing an electrosynthesized polymer with buffering capability. It was obtained by deposition of a weighed amount of urease (Ur) at a glassy carbon (GC) electrode followed by immobilization by an electrosynthesized poly-o-phenylenediamine (PPD) film. An unconventional “upside-down” (UD) geometry was employed for the electrochemical cell. The response of GC/Ur/PPD sensor is linear with urea concentration in the range 10 microM to 1 mM (15 mV/mM, R2 = 0.9999) due to buffering capability of PPD film, which represents a novel role of electrosynthesized polymers in their application to biosensors. At higher concentrations, the more common Nernstian response (28 mV/decade, R2 = 0.9987) is observed. The sensor exhibits a sufficient sensitivity for practical determinations, rapid response and long term stability.

We have developed a novel and straightforward approach for the green synthesis of reduced graphite oxide (rGO). First, graphite oxide (GO) was prepared by the Hummers' oxidation method, starting from high-surface-area graphite. Then, rGO was generated from GO in aqueous suspension through a UV-irradiation treatment. The influence of different process parameters (including type of UV source, irradiation time and atmosphere) on the GO reduction efficiency was explored and evaluated on the basis of the data acquired by several experimental techniques, such as infrared spectroscopy in attenuated total reflectance mode, X-ray diffraction, UV-vis absorption spectrophotometry, X-ray photoelectron spectroscopy and thermogravimetry. The acquired results allowed identifying appropriate sets of reaction conditions under which GO reduction yield could be maximized. In particular, the highest reduction degree was obtained by exposing GO to UV light in a UV oven for 48 h under inert atmosphere. The reduction strategy developed by us represents an innovative low-cost and easy route to graphene-based nanomaterials, which does not require any stabilizer, photocatalyst or reducing agent. For this reason, our method represents an attractive environmentally friendly alternative approach for the preparation of stable rGO dispersions in large-scale amounts, to be utilizable in disparate engineering applications.

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.

The present work describes a novel technology for microstructuring polypyrrole based on the photoelectropolymerization of PPy films on micromachined ntype silicon (n-Si) substrates. The proposed approach conjugates the flexibility of micromachining techniques in fabricating three-dimensional (3D) microstructures with conducting polymers technology leading to the development of novel PPy films whose features at the microscale can be tailored to the specific applications. Photoelectropolymerization process has been previously studied on flat n-Si substrates and, under selected experimental conditions, on micromachined n-Si containing regular array of ordered macropores with pitch of 8 μm, size (s) of 5 μm and depth (d) of 10 μm. Scanning Electron Microscopy (SEM) analysis of both flat and microstructured PPy films evidenced an isotropic polymers deposition uniformly covering the silicon substrates and perfectly replicating micromachined silicon features. The electrochemical response of photogenerated PPy films to selected probe has been observed and the role of micrometer-scale morphology in enhancing film recognition properties has been verified.

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.

Inthis paper, we have investigated the possibility to realize a nanocomposite buffer layer for perovskite solar cells, based on polyelectrolyte poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) PEDOT:PSS and graphene oxide (GO). To this aim, GO, prepared by a modified Hummers method, was mixed with PEDOT: PSS by solvent swelling method and reduced in situ into the polymer matrix through a green and simple method, by using UV radiation. Thin nanocomposite layers were spin coated on different substrates and characterized by several techniques. GO reduction was first analyzed by XPS analyses, monitoring the decrease of the intensity of the peak of the oxygen groups linked to carbon. The grade of the dispersion of GO into PEDOT: PSS was also analyzed by scanning electron microscopy. Sheet resistance measurements of the films with and without GO before and after UV treatment was performed. The thermal stability of the nanocomposites was then evaluated by thermogravimetric analyses. The nanocomposite layer was finally employed in a perovskite solar cell to evaluate the effect of GO reduction on power conversion efficiency. The interface interaction between the nanocomposite and the perovskite precursors was analyzed by contact angle measurements.