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This article is the first to investigate respondents' ease of understanding and answering valuation questions related to the Becker–DeGroot–Marschak (BDM) and multiple price list mechanisms. Using a between‐subjects design, we elicit willingness to pay (WTP) for healthy snack bars using two mechanisms, ask questions about ease of understanding and answering the valuation questions, and record the response times to the valuation questions. We do not find significant differences in estimated WTP and response times between the two methods. However, the respondents in the multiple price list (MPL) sessions found it easier to understand this mechanism and decide on a response than those in the BDM sessions. As a result of our findings, we recommend that MPL is adopted over BDM when there is limited opportunity to explain or learn the method before the valuation or when one is concerned that a complicated design can affect the willingness to participate and thereby create selection bias. Both concerns will often apply when small and medium size agribusinesses conduct market testing of their products in stores or field markets. [EconLit Citations: C18, C19, D44, Q13].

Self-supporting membranes built entirely of carbon nanotubes have been prepared by wet methods and characterized by Raman spectroscopy. The membranes are used as supports for the electrodeposition of Pt nanoparticles without the use of additional additives and/or stabilizers. The Pt precursor is an ad hoc synthesized ammonium-ethylimidazolium chloroplatinate(IV) salt, [NH3(CH2)2MIM)][PtCl6]. The Pt complex was characterized using NMR spectroscopy, XRD, ESI-MS, and FTIR spectroscopy. The interaction between the Pt-carbon nanotubes nanocomposites and hydrogen is analyzed using electrochemical and quartz microbalance measurements under near-ambient conditions. The contribution of the Pt phase to the hydrogen adsorption on nanotube is found and explained by a kinetic model that takes into account a spillover event. Such a phenomenon may be exploited conveniently for catalysis and electrocatalysis applications in which the hybrid systems could act as a hydrogen transfer agent in specific hydrogenation reactions. Adsorption advantage: Self-supporting membranes of carbon nanotubes are prepared and used as supports for the electrodeposition of Pt nanoparticles by using an ad hoc synthetized ammonium-ethylimidazolium chloroplatinate(IV) salt as Pt precursor. The hydrogen adsorption on Pt-carbon nanotubes nanocomposites is studied experimentally by electrochemical and quartz microbalance measurements and explained by a kinetic model that takes into account a spillover event.

A fully regioregular poly(3-alkylthiophene) displaying only head-to-head/tail-to-tail connections between thiophene rings has been prepared by oxidative chemical or electrochemical polymerization starting from a symmetrical bithiophene monomer bearing at the β positions the optically active S -(+)-2-methylbutyl group. The polymeric product has been fully characterized as far as its spectroscopic, solvatochromic, chiroptical, thermal, electrochemical and morphological properties are concerned. In particular, the solvatochromic, chiroptical and thermal properties have been compared to those of the related, well known, head-to-tail regioregular polymeric derivative possessing the same side-chain substituent in order to elucidate the structural features characterizing the head-to-head regioregular derivative.

Indium tin oxide (ITO) substrates were functionalized with fluoroalkylsilanes (FAS) having formula RFC(O)N(R)(CH2)3Si(OMe)3 (1, R = H, RF = C5F11; 2, R = CH3, RF = C5F11; 3, R = H, RF = C3F7) and containing embedded amide moieties between the perfluoroalkyl chain and the syloxanic moiety. Subsequently, Au nanoparticle deposition (AuNP) onto the ITO-FAS functionalized surfaces was carried out by immersion into a solution of citrate-stabilized AuNP. The ITO-FAS and AuNP/ITO-FAS modified systems were characterized by various complementary techniques and compared with AuNP/ITO modified with RF(CH2)2Si(OEt)3 (4, RF = C6F13), free from functional groups between the fluorinated tail and the syloxanic moiety. The results showed that only ITO glasses modified with 1, 2 and 3 displayed an oleophobic, as well as hydrophobic, behaviour and that the AuNP Surface Coverage (SC %) directly depended on the fluoroalkylsilane nature with the following trend: 60% ITO-2 > 16% ITO-3 > 9% ITO-1 > 3% ITO-4. The obtained results revealed that, in organosilane 2, the presence of a methyl group on the amide nitrogen increases the steric hindrance in the rotation around the N CO bond, resulting in the co-presence of two stable conformers in comparable amounts. Their co-presence in solution, combined with the lack of intermolecular N H⋯OC N hydrogen bonds among the anchored molecules, has dramatic influences on the functionalized ITO, yielding a disorderedly packed coating able to accommodate a large quantity of AuNP. These results indicate that AuNP can act as excellent probes to evaluate the coating layer quality but, at the same time, it is possible to tune the gold loading on electroactive surfaces depending on the chemical structure of the used fluorinated silane.

Nanostructures based on copper (Cu NSs ) are promising materials in different fields of application. To this end, in this work we have studied a simple one-step electrosynthesis of Cu NSs directly onto ITO electrode surface starting from an aqueous solution of copper sulphate. We have investigated the effects of the presence of electrolyte salts such as K 2 SO 4 , Na 2 SO 4 and (NH 4 ) 2 SO 4 and we have found that they gave rise to the formation of a number of remarkably different forms of nanostructures. In particular, when the electrodeposition was conducted in presence of K 2 SO 4 fractal-like or dendritic structures consisting of a long central backbone and sharp side branches were observed. The resulting Cu NSs were characterized by SEM, XRD and by electrochemical techniques. Studies on the electrocatalytic behaviour of dendritic Cu NSs modified electrodes towards the oxidation of L-tyrosine in 0.05 M NaOH solution showed a 1.0 10 −6 ÷ 7.0 10 −5 M linear range and a detection limit of ca. 6.0 10 −7 M.

We present an innovative device based on a nanoporous Ge electrode decorated by gold nanoparticles (AuNPs). A study aimed at obtaining the best AuNP deposition conditions, which allow the decoration of Ge walls with AuNPs, avoiding particles aggregation is reported.The performance of the electrode has been evaluated by the electrocatalytic reduction of iodoethane in acetonitrile solution, a model reaction in organic electrocatalysis. Keywords: Nanoporous Ge, Gold nanoparticles, Electrodeposition, Electrocatalysis

Herein we report a new, simple, low cost and one step way to obtain silica-supported silver nanoparticles (AgNPs) on commercial polyethyleneimine-functionalized silica beads (SiO2-PEI) under mild experimental conditions. The novel AgNPs/(SiO2-PEI) material has been thoroughly analyzed using FE-SEM, BET, XRD, XPS and XE-AES analysis. The reduction of Methylene Blue (MB) to Leuco Methylene Blue (LMB) in the presence of NaBH4 was chosen for testing the catalytic properties of AgNPs/(SiO2-PEI) towards dyes decoloration. Moreover, the prepared supported nanocatalyst was also found to exhibit excellent catalytic activity towards decoloration of some azo dyes such as E110 and E122.

The fabrication of silane-based fluorinated self-assembled monolayers (FSAMs) on indium tin oxide (ITO, a transparent electrode) was carried out making use of the following fluoroalkylsilanes (FAS): 2,2,3,3,4,4,5,5,6,6,6-undecafluoro-N-[3-(trimethoxysilyl]propyl]hexanamide (1; R-F = C5F11) and 1,1,2,2,3,3,4,4,4-nonafluoro-N-[3-(trimethoxysilyl)-propyl]butane-1-sulfonamide (2; R-F = C4F9), containing an embedded amide and a sulfonamide group, respectively, between the short perfluoroalkyl chain (R-F with C < 6) and the syloxanic moiety. The obtained FSAM-modified/ITO systems were characterized by X-ray photoelectron spectroscopy (XPS), contact angle (CA), surface energy measurements, and electrochemical impedance spectroscopy (EIS) and compared to ITO modified with a 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluor-ooctyltriethoxysilane (3; R-F = C6F13), with the perfluoroalkyl group linked to the syloxanic moiety through a simple hydrocarbon chain. The results obtained show that the presence of the -NHCO- and -NHSO2- groups have a different mode of action and, with the former, despite the short perfluoroalkyl chain, the ITO-1 system presents a CA (Theta(water) = 113.5 degrees) and surface energy (gamma(1) = 14.0 mJ m(-2)) typical of amphiphobic materials. These properties can be exploited in a variety of applications, such as self-cleaning, anti-fouling, and anti-fingerprint coatings, and in advanced microelectronic components.

Gold nanoparticles (AuNPs) were anchored on alkynyl carbamate-functionalized support materials having the suitable features for application as catalysts in continuous-flow packed bed reactors. The functionalization step was carried out by grafting with the difunctional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) three commercial micrometer-sized oxide supports, i.e. silica, alumina, and titania. The alkynyl-carbamate moieties were capable of straightforwardly reducing the gold precursor HAuCl4 yielding the supported AuNPs systems Au/SiO2@Yne, Au/Al2O3@Yne, and Au/ TiO2@Yne. A comparison among the three materials revealed that silica allowed the highest organic functionalization (12 wt %) as well as the highest gold loading (3.7 wt %). Moreover, a TEM investigation showed only for Au/SiO2@Yne the presence of homogeneously distributed spherically shaped AuNPs (average diameter 15 nm). Au/ SiO2@Yne is an efficient catalyst, both in batch and flow conditions, in the oxidation of a large variety of alcohols using H2O2 as the oxidizing agent at a temperature of 90 °C. Furthermore, under flow conditions, the catalyst worked for over 50 h without any significant decrease in the catalytic activity. The catalytic activity of the three catalysts was evaluated and compared in the oxidation of 1-phenylethanol as a model substrate. We found that the flow approach plays a strategic role in preserving the physical and chemical integrity of the solid catalysts during its use, with remarkable consequences for the reaction conversion (from 2% in batch to 80% in flow) in the case of Au/TiO2@Yne.

A polymeric membrane-based ion-selective electrode (ISE) for the determination of l -ascorbic acid ( l -AA) was developed. The sensor was fabricated by modifying glassy carbon electrodes with molecularly imprinted polypyrrole (PPy) synthesized by electropolymerization of the monomer in the presence of ascorbate. A comparison between the non-imprinted modified electrode (PPy-NIP) and the molecularly imprinted polymer (PPy-MIP) is reported. The molecularly imprinted polymer improves the performances of the sensor, especially if the PPy film has been submitted to an oxidation treatment. The PPy-MIPox electrode shows near-Nernstian response (approx. −57 mV/decade) to the ascorbate over the concentration range between 5 × 10−6 M and 2 × 10−3 M and it can be used for more than 3 weeks without any considerable change in the measured response. The potentiometric sensor has been successfully applied to the determination of ascorbate in food and pharmaceutical samples (recoveries of about 100%).

In this work, a Ni/Al hydrotalcite (HT) was used as glucose oxidase (GOx) immobilizer. Small-area and angle-resolved X-ray photoelectronspectrawererecordedonHTselectrosynthesizedonPtintheabsenceandinthepresenceofGOx,andcompared with those obtained for a Pt surface, modified with the electrosynthesized HT, on which a drop of GOx solution was deposited. Thesimultaneouselectrodeposition ofHT +GOxresultedinacompactdeposit,thickerthantheXPSsamplingdepth(>10 nm), that is not homogeneous in the lateral and in-depth composition. The presence of GOx can be deduced comparing the N1s spectra of HT and HT + GOx: in the latter, the N1s component at 400 eV binding energy (BE) is predominant whilst, depending on the analyzed point, a small or no contribution from the component at 407.2 eV, due to nitrate, is revealed. Angle-resolved XPS provides evidence on the in-depth composition of anions, cations and GOx. The results highlight the crucial role played by nickel in GOx immobilization. On the basis of the results, it can be suggested that enzyme activity is unevenly distributed and is localized in small areas, where Ni concentration is higher. Copyright c � 2010 John Wiley & Sons, Ltd.

The majority of the amperometric glucose biosensors employs stabilization membranes to prevent enzyme release and to improve selectivity. Here, we describe a comparative study between some of the most common membranes and two more innovative systems based on titania and Pd hexacyanoferrate hydrogels. The study has been carried out on electrodes modified by a Ni/Al hydrotalcite electrochemically deposited on Pt surfaces together with the enzyme glucose oxidase. The effect of the different membranes on the selectivity, stability and sensitivity of the biosensors has been described and the best ones have been successfully applied to the analysis of real matrices. To further improve biosensor selectivity a pre-oxidizing enzyme membrane containing also horseradish peroxidase was employed.

A novel, convenient method for the preparation of gold nanoparticles supported on alkyne-functionalized nanosilica is presented. Silica nanoparticles functionalized with alkynyl carbamate moieties (SiO2@Yne) were synthetized by co-condensation of the di-functional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) with tetraethoxysilane (TEOS) in alkaline medium. The alkynyl-carbamate functionalities present on silica are able to capture the gold precursor HAuCl4, spontaneously reduce it, and stabilize the resulting supported AuNPs, having an average size of ca. 11 nm. The prepared Au-SiO2@Yne was thoroughly analyzed by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS), FT-IR and UV-Vis spectroscopy. The catalytic activity of Au-SiO2@Yne was investigated for the reduction of 4-nitrophenol to 4-aminophenol by NaBH4 and kinetic constants k in the order of magnitude of about 10-2 s-1 were found.

Metal/organosilane/oxide sandwich structures were prepared via a two-step self-assembly method. First, indium tin oxide (ITO) substrates were functionalized with the following fluoroalkylsilanes (FAS): RFC(O)N(H)(CH2)3Si(OMe)3 (1, RF = C5F11), containing an embedded amide between the perfluoroalkyl chain and the syloxanic moiety, and RF(CH2)2Si(OEt)3 (2, RF = C6F13). Subsequently, Au nanoparticles (AuNPs) introduction in the obtained systems was carried out by controlled immersion into a solution of citrate-stabilized AuNPs. The physico-chemical properties of the target materials were thoroughly investigated by using various complementary techniques. Finally, the application of such systems as catalysts for methanol electro-oxidation under alkaline conditions was investigated, revealing the synergistical role played by FAS and AuNPs in promoting a remarkable electrocatalytic activity.

none 10 no This work proposes a preparation route to heterogeneous catalysts based on gold nanoparticles (AuNPs) supported on chemically modified silica. More specifically, the latter is functionalized with amino-sulfide branches (Au-SiO2@AeThio) through a thiol-yne radical coupling performed between cysteamine hydrochloride and an alkynyl-substituted triethoxysilane, followed by co-condensation with tetraethoxysilane (TEOS). The target procedure, involving only a gold precursor without any need of additional reducing and/or stabilizing agents, is straightforward, controllable, reproducible, and particularly appealing from a “green” point of view. The supported AuNPs, with an average diameter of 10 nm, possess a remarkable catalytic activity (specific rate constants of the order of 102 s1 mgcat 1) in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride (NaBH4) in aqueous media. The higher performances with respect to previous literature work, along with the possibility of successfully recycling the catalyst, shows the developed materials as attractive functional platforms. mixed Barbara Ballarin; Davide Barreca; Elisa Boanini; Elisa Bonansegna; Maria Cristina Cassani; Giorgio Carraro; Silvia Fazzini; Adriana Mignani; Daniele Nanni; Davide Pinelli Barbara Ballarin; Davide Barreca; Elisa Boanini; Elisa Bonansegna; Maria Cristina Cassani; Giorgio Carraro; Silvia Fazzini; Adriana Mignani; Daniele Nanni; Davide Pinelli

International audience; Operando XANES and EXAFS spectra on the newly prepared Fe hexacyanocobaltate active material for positive electrodes in lithium batteries have been recorded at the XAFS beamline of Elettra using a suitable in situ cell. In this way, it was possible to follow in detail the main structural and electronic changes during the charge and discharge processes of the battery. The use of a chemometric approach for data analysis is also underlined.

An amperometric glucose biosensor was developed using an anionic clay matrix (layered double hydroxide (LDH), Ni/Al–NO 3 ) for the immobilization of glucose oxidase (GOx). The biofilm was prepared by electrodeposition of the clay and GOx and subsequent cross-linking with glutaraldeyde. The Pt surface modified with the Ni/Al–NO 3 shows a much reduced noise, giving rise to a better signal to noise ratio for the currents relative to H 2 O 2 oxidation, and a linear range for H 2 O 2 determination wider than the one observed for bare Pt electrodes. Under the optimised operative conditions, the performances of the biosensor have been evaluated by measuring the steady-state currents (at +0.45 V versus SCE) to increasing concentrations of glucose in “air saturated” 0.1 M phosphate buffer (pH 7.0). Both batch and flow injection modes were explored. The response to glucose was linear up to 8.0 and 12.0 mM, and the sensitivities were 7.7 ± 0.1 and 19.1 ± 0.2 mA M −1 cm −2 , respectively. The current response of the biosensors does not significantly change for 15 consecutive days in batch and for 10 days in flow, at least, if stored at 4 °C in phosphate buffer, when not in use. The effects of interferants and applicability to fruit juices and soft drinks analysis of the biosensor were also investigated.

The reactivity of vanadyl pyrophosphate, catalyst for the selective oxidation of n -butane to maleic anhydride, was examined under n -butane-rich conditions, simulating a feed in which oxygen is the limiting reactant, and a process in which the unconverted n -butane is recycled. A lower selectivity to maleic anhydride was found with respect to the hydrocarbon-lean conditions, due to the higher selectivity to carbon oxides and to the formation of C 8 by-products: tetrahydrophthalic and phthalic anhydrides. The latter compounds formed by a consecutive reaction of maleic anhydride with the unsaturated C 4 intermediates. This occurred under conditions of total oxygen conversion, due to the decreased catalyst oxidizing property. A relevant contribution of radicalic, homogeneous reactions was also observed, which mainly led to the formation of carbon oxides and olefins. This contribution decreased in the presence of the catalyst, which acted as a radical scavenger, but nevertheless remained important at temperatures higher than 400 °C. When conditions were used under which the conversion of oxygen was not total, olefins generated in the gas phase reacted at the catalyst surface yielding maleic anhydride. This homogeneously initiated heterogeneous process led to an unusual effect, of a relevant increase of maleic anhydride yield over 400 °C.

A simple method to prepare a hybrid material (ZnAl–AgNPs) based on silver nanoparticles and ZnAl layered double hydroxides (ZnAl LDHs), for possible use in a cosmetic formulation as deodorant, was reported. ZnAl–AgNPs, include the high adsorption capacity, the biocompatibility, the antacid properties of LDH and the antibacterial activity of AgNPs. According to the characterization with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM), it was possible to confirm that interaction of AgNPs with ZnAl LDH occurs by adsorption rather than intercalation of AgNPs in LDH. The deodorant activity of ZnAl–AgNPs was tested using the headspace solid phase micro-extraction gas chromatography (HS-SPME-GC) and the antibacterial property was monitored on gram-negative bacteria. For comparison raw ZnAl LDH was also investigated. The results showed that both raw ZnAl LDH and ZnAl–AgNPs have deodorant activity higher than that of zinc ricinoleate, normally used in commercial formulations.

A heterostructure based on gold nanoparticles (AuNPs) and NiAl layered double hydroxide (LDH) was prepared by one-step electrosynthesis, directly onto the electrode surface. The resulting material (AuNPs–NiAl LDH) was characterized by SEM, TEM, UV–vis, XRD, EXAFS, and XANES spectroscopy and by electrochemical techniques. The deposition process of the heterostructure on the Pt electrode was investigated by the electrochemical quartz crystal microbalance (EQCM). The electrocatalytic behavior of AuNPs–NiAl LDH toward the oxidation of methanol in basic media was compared with those of individual AuNPs and NiAl LDH, and an enhancement of the catalytic efficiency over a wide methanol concentration range was pointed out.

International audience; This work describes a new one-step method for the preparation of AuNP/LDH nanocomposites via the polyol route. The novelty of this facile, simple synthesis is the absence of additional reactants such as reductive agents or stabilizer, which gives the possibility to obtain phase-pure systems free of undesiderable effect. The AuNP formation is confirmed by SEM,TEM, PXRD, and XAS; moreover, the electrochemical characterization is also reported. The electrocatalytic behavior of AuNP/LDH nanocomposites has been investigated with respect to the oxidation of methanol in basic media and compared with that of pristine NiAl-Ac. The 4-fold highest catalytic efficiency observed with AuNP/LDH nanocomposites suggests the presence of a synergic effect between Ni and AuNP sites. The combination of these experimental findings with the low-cost synthesis procedure paves the way for the exploitation of the presented nanocomposites materials as catalysts for methanol fuel cells.

The electrochemical polymerization of the monomer 3,3’’-di[(S)-(+)-2-methylbutyl]-2,2’:5’,2’’-terthiophene (DMBTT) was carried out potentiodinamically on indium tin oxide (ITO), Pt or glassy carbon (GC) electrodes in anhydrous CH3CN with TBAPF6 as supporting electrolyte. The films of poly(DMBTT) were characterized by various analytical techniques including UV-Vis-NIR absorption spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM), and gel permeation chromatography (GPC). The most outstanding properties of the polymer electrochemically synthesized were compared with those of the same polymer obtained by a chemical method. The major difference lay in the length of the polymeric chain, which resulted much shorter for the electrochemically generated product. The film obtained on ITO displayed a reversible electrochromic behavior under potential switching between -0.50 and +1.00 V vs. SCE.

Department of Physical and Inorganic Chemistry, University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italyphone: +390512093256*e-mail: erika.scavetta2@unibo.itReceived: February 1, 2011;&Accepted: April 7, 2011AbstractA glassy carbon electrode has been coated by electrodeposition with a thin film of cobalt based layered double hy-droxide (LDH) and used as a pH sensor. The developed electrode displays a linear super-Nernstian response( 76.2 0.6 mV/pH) in the pH range between 2 and 14 and it is particularly suitable to operate in strongly alkalinesolution. The reproducibility of the sensor construction is good with a relative standard deviation of the calibrationcurve slopes of 2.5% (n=4). The electrode has a response time comparable to that exhibited by commercial glasselectrodes in the pH range examined and is not affected by interference from the most common anions and cations.Keywords: Co/Al layered double hydroxide, pH sensor, Electrodeposition, Potentiometric sensorDOI: 10.1002/elan.201100058

Ni hydroxide and Ni/Al layered double hydroxide (LDH) were electrochemically deposited on Pt electrodes in the presence of glucose oxidase in the electrolytic solution, in order to verify if the performances of the two biosensors were dependent on the Ni content of the inorganic matrix used to entrap the enzyme. The comparative study was conducted by recording the current response due to the oxidation of H 2 O 2 , produced enzymatically after glucose additions, at +0.45 V versus SCE, pH 7.0 and T = 25 °C. A higher sensitivity and a narrower linearity range were observed for nickel hydroxide based biosensor (up to 5 mM against 15 mM exhibited when LDH was the immobilizing matrix). These results suggested that the amount of the enzyme entrapped on the electrode surface was higher when the matrix was Ni(OH) 2 and they were confirmed by EQCM measurements. On the contrary, the selectivity displayed by the two biosensors in the presence of interfering compounds, such as acetaminophen, citric, uric and ascorbic acids, was almost the same.

An amperometric biosensor based on Pt electrodes modified with a thin film of a Ni, Al layered double hydroxide (LDH), submitted to a preliminary oxidative treatment in order to have the nickel centers at the oxidation state þ 4, and glucose oxidase (GOx) is presented. The oxidized LDH acts both as a system to support the enzyme and as a barrier to anions since it acquires an overall negative charge, as demonstrated by electrochemical impedance spectroscopy. Even if the biosensor response is due to the detection of H2O2 at anodic potentials, glucose can be accurately determined in the presence of ascorbic acid or other interferences, commonly present in real matrices in anionic form, since they can not reach the electrode surface. The effectiveness of the developed biosensor has been demonstrated by measuring glucose in samples of fruit juices containing ascorbic acid at high levels.

An amperometric glucose biosensor was developed using an anionic clay matrix of hydrotalcitic nature (Ni/Al–NO3 HT) as enzyme support, which was electrochemically synthesized at −0.90 V versus SCE, using a rotating disk Pt electrode to assure homogeneity of the electrodeposition suspension. The biorecognition element was glucose oxidase (GOx) immobilized on HT during the electrosynthesis, which was followed by cross-linking with glutaraldehyde vapours to avoid the enzyme release. The performances of the biosensor, in terms of sensitivity to glucose calculated from the slope of the calibration curve, are dependent on parameters related to the electrodeposition. An experimental design was applied to detect the optimal conditions of electrosynthesis in order to optimize the glucose biosensor performance. The factors taken into account were enzyme concentration and Ni/Al molar ratio. A full factorial design was performed to study linear interactions between factors and their quadratic effects and the optimal setup was evaluated by the isoresponse curves. The significant factors were enzyme concentration (linear and quadratic terms) and the interaction between enzyme concentration and Ni/Al molar ratio. Under the optimized electrodeposition conditions, the reproducibility of the biosensor fabrication was very good, being the RSD of the sensitivity about 5%. © 2007 Elsevier B.V. All rights reserved.

Two amperometric biosensors based on glassy carbon electrodes (GC) modified with Mg/Al layered double hydroxides (LDHs) containing ferrocene-carboxylate (FcCO2H) or ferrocene-sulfonate (FcSO3H), as interlayer anions, and glucose oxidase (GOx) are presented. Amperometric detection of glucose involves the electrochemical oxidation of H2O2 mediated by the ferrocene derivative. Optimization of the biosensors construction and of the operative conditions was investigated and is discussed herein. The performances of the two biosensors were evaluated by chronoamperometry, working at low anodic potentials (þ 0.400 V for FcCO2H and þ 0.500 V for FcSO3 Hv s. SCE). The linearity extended up to 1.5 mM and 10.0 mM in batch and in flow conditions, respectively, for both biosensors, whereas the sensitivity was higher for the one based on FcCO2H (4.8 � 0.3versus 2.0 � 0.3 m Am M � 1 cm � 2 in batch mode, and 63.9 � 0.4 versus 25.8 � 0.4 m Am M � 1 cm � 2 in flow mode). The biosensors display rapid response time (less than 20 s), good reproducibility, as well as good operational stability. Glucose can be accurately determined in the presence of the most common interferences that coexist in blood serum if an oxidative membrane containing nanoparticles of MnO2 is applied on the biosensors? surface.

Microscopy techniques were used to study films of a hydrotalcite-like compound electrosynthesised on a Pt electrode, entrapping glucose oxidase. SECM study has been carried out to probe local enzymatic activity and to obtain topographic images of the modified electrode, which can be used as glucose amperometric biosensor. Due to the complexity of the investigated system, different configurations were considered, starting from the Pt surface only modified with the inorganic clay, up to the optimized biofilm, with glucose oxidase stabilized by cross-linking with glutaraldehyde. SECM was used to detect the activity of the entrapped enzyme by observing the feedback current in a solution of K4[Fe(CN)6] and glucose in phosphate buffer, when K3[Fe(CN)6] was generated at the tip. It was demonstrated that the enzyme distribution was not homogeneous all over the electrode surface, but it reflected the distribution of the underlying electrosynthesised inorganic film. SECM gave only poor topographic information about the complex samples studied, but the images were in good agreement with those provided by other microscopy techniques. © 2007 Elsevier B.V. All rights reserved.

Recently, we presented the preparation, without any need of additional reducing and/or stabilizing agents, of a variety of stable silica-supported gold nanoparticles (AuNPs) by using as the only reactants an aqueous solution of chloroauric acid (HAuCl4) and different functionalized-silica supports. We started using commercial polyethyleneimine-functionalized silica bead [1] and we went on preparing silica nanoparticles with alkynyl carbamate moieties [2]. We now present the results of our recent work with supported AuNPs, which has been focused on the synthesis of a material with the right features for the application as catalyst in a continuous flow system. Indeed, flow chemistry is recognized by the Green Chemistry Institute (GCI) as a key area for research activities in the aim of developing sustainable manufacturing [3]. [1] S. Fazzini , D. Nanni , B. Ballarin , M. C. Cassani , M. Giorgetti , C. Maccato, A. Trapananti, G. Aquilanti and S. I. Ahmed, J. Phys. Chem. C. 116 (2012) 25434−25443. M. Giorgetti, G. Aquilanti, B. Ballarin, M. Berrettoni, M. C. Cassani, S. Fazzini, D. Nanni and D. Tonelli, Anal. Chem. 88 (2016) 6873-6880. [2] S. Fazzini, M. C. Cassani, B. Ballarin, E. Boanini, J. S. Girardon, A.S. Mamede, A. Mignani and D. Nanni, J. Phys. Chem. C. 118 (2014) 24538-24547. [3] C. Wiles and P. Watts, Green Chem. 16 (2014), 55-62.

Recently, we presented the preparation, without any need of additional reducing and/or stabilizing agents, of a variety of stable silica-supported gold nanoparticles (AuNPs) by using as the only reactants an aqueous solution of chloroauric acid (HAuCl4) and different functionalized-silica supports. We started using commercial polyethyleneimine-functionalized silica bead and we went on preparing silica nanoparticles with alkynyl carbamate moieties. We now present the results of our recent work with supported AuNPs, which has been focused on the synthesis of a material with the right features for the application as catalyst in a continuous flow system. Indeed, flow chemistry is recognized by the Green Chemistry Institute (GCI) as a key area for research activities in the aim of developing sustainable manufacturing. The silica-supported AuNPs have been prepared by the simple grafting of commercial available silica with the alkyne terminated organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS), followed by the addition of HAuCl4 to obtain the in situ formation of the target AuNPsanchored systems. The resulting material (Au/SiO2@Yne) has been characterized with various techniques, such as atomic absorption spectroscopy (AAS), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Afterwards, Au/SiO2@Yne has been employed as heterogeneous catalyst in the oxidation of alcohols to their corresponding carbonyl compounds. The reaction conditions have been chosen with particular attention to the green aspect, therefore the oxidation have been carried out using a mixture of tert-butanol and water as solvent and hydrogen peroxide as the oxidant agent.

Layered Double Hydroxides (LDHs) have general formula [M(II)M(III)(OH)] x+ (A n-a1-xbx2x/n )mH 2 O, where x ranges between 0.2 and 0.5, depending on the nature of the M a and M b metals [1]. These materials are attractive due to their anionic exchange behaviour which makes them useful in several fields, such as catalysis, separation technology, and medicine. When M a (II) is a transition metal, like Ni or Co, undergoing a reversible redox reaction between the oxidised and reduced states, the material displays improved charge transport properties, especially in alkaline solution [2]. For most LDHs applications in the field of electrochemical sensors, it is required to coat a metal or a carbon-based substrate with a stable thin film. Previously, we have described a simple and rapid electrochemical procedure to deposit, with good reproducibility, well adherent thin films of Ni/Al or Co/Al LDHs on conductive surfaces [3]. In this contribution we report two analytical applications of cobalt-based LDH modified Pt electrodes. The former concerns the development of a potentiometric pH sensor, the latter the amperometric detection of salicylic acid (SA). The performances of the coated electrode as pH sensor are summarized in Figure 1. It shows, as a function of time, the recorded potential and the corresponding pH value, simultaneously recorded with a conventional glass electrode, in a dynamic experiment where the pH of a universal buffer solution is increased in the range 5.5-12 by dropwise addition of KOH. The graph highlights the excellent behaviour of the new sensor, as to response time (5 s for all the investigated pH values) and signal stability. The response is linear, with a slope of -76.2 + 0.6 mV/pH in the pH interval between 2 and 14, and does not suffer from memory effects.