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We employed the oxidative dehydrogenation of C2H2 by CO2 and the C2H2 decomposition to prepare carbon nanotubes (CNTs) and carbon nanofibers (CNFs). The use of a small amount of Ni catalyst made it possible to produce CNTs and CNFs having a highly defective structure at a relatively low temperature compared to the one typically used for the CNT synthesis. The synthesized CNTs and CNFs were decorated with about 10 nm-gold nanoparticles (AuNPs) via an electrostatic self-attachment. The electrode with CNTs synthesized via the C2H2–CO2 reaction exhibits superior electrochemical reactivity with H2O2 when compared to the ones with CNTs synthesized via C2H2 decomposition, commercial CNTs, CNFs, and other more common carbon supports e.g. carbon black and activated charcoal. It demonstrates a rapid response, high sensitivity (104.9 μA mM−1 cm−2), wide linear working range (5 μM–23 mM), low detection limit (0.138 μM), good selectivity, reproducibility, and stability. The CNTs synthesized via the C2H2–CO2 reaction are suggested as energy-saving, cost-effective and environmentally friendly supporting material candidates for practical applications. The electrodes with CNTs show a high electrochemically active surface area, low charge transfer resistance and fast mass transfer at the electrode surface that are key factors for H2O2 detection.

© The Author(s)., For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co2TiO4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer–Emmett–Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology., Funding was provided by Conicyt-Fondecyt Chile (Grant N°1161225), Conicyt-FONDEQUIP Chile (Grant N° EQM170111), and Redes de Investigación 021842SG_RED: RCNM-USACH “Red de Caracterización de NanoMateriales—Universidad de Santiago de Chile”. Additional funding was provided by Ministerio de Economia (MINECO, Spain) under project RTI2018-095303-B-C51.

Precise designs of low-cost and efficient catalysts for the detection of hydrogen peroxide (H2O2) over wide ranges of pH are important in various environmental applications. Herein, a versatile and ecofriendly approach is presented for the rational design of ternary bentonite-silylpropyl-polypyrrole/silver nanoarchitectures (denoted as BP-PS-PPy/Ag) via the in-situ photo polymerization of pyrrole with salinized bentonite (BP-PS) in the presence of silver nitrate. The Pyrrolyl-functionalized silane (PS) is used as a coupling agent for tailoring the formation of highly exfoliated BP-PS-PPy sheet-like nanostructures ornamented with monodispersed Ag nanoparticles (NPs). Taking advantage of the combination between the unique physicochemical properties of BP-PS-PPy and the outstanding catalytic merits of Ag nanoparticles (NPs), the as-synthesized BP-PS-PPy/Ag shows a superior electrocatalytic reduction and high-detection activity towards H2O2 under different pH conditions (from 3 to 10). Intriguingly, the UV-light irradiation significantly enhances the electroreduction activity of H2O2 substantially, compared with the dark conditions, due to the high photoelectric response properties of Ag NPs. Moreover, BP-PS-PPy/Ag achived a quick current response with a detection limit at 1 &mu, M within only 1 s. Our present approach is green, facile, scalable and renewable.

For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co2TiO4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer–Emmett–Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology.

A super-porous hybrid platform can offer significantly increased number of reaction sites for the analytes and thus can offer advantages in the biosensor applications. In this work, a significantly improved sensitivity and selectivity of hydrogen peroxide (H2O2) detection is demonstrated by a super-porous hybrid CuO/Pt nanoparticle (NP) platform on Si substrate as the first demonstration. The super-porous hybrid platform is fabricated by a physiochemical approach combining the physical vapor deposition of Pt NPs and electrochemical deposition of super-porous CuO structures by adopting a dynamic hydrogen bubble technique. Under an optimized condition, the hybrid CuO/Pt biosensor demonstrates a very high sensitivity of 2,205 &micro, A/mM∙cm2 and a low limit of detection (LOD) of 140 nM with a wide detection range of H2O2. This is meaningfully improved performance as compared to the previously reported CuO-based H2O2 sensors as well as to the other metal oxide-based H2O2 sensors. The hybrid CuO/Pt platform exhibits an excellent selectivity against other interfering molecules such as glucose, fructose, dopamine, sodium chloride and ascorbic acid. Due to the synergetic effect of highly porous CuO structures and underlying Pt NPs, the CuO/Pt architecture offers extremely abundant active sites for the H2O2 reduction and electron transfer pathways.

Lignin is the second largest naturally renewable resource and is primarily a by-product of the pulp and paper industry; however, its inefficient use presents a challenge. In this work, Fe3O4 nanoparticles loaded on lignin nanoparticles (Fe3O4@LNPs) were prepared by the self-assembly method and it possessed an enhanced peroxidase-like activity. Fe3O4@LNPs catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue color, was observable by the naked eye. Under the optimal conditions, Fe3O4@LNPs showed the ability of sensitive colorimetric detection of H2O2within a range of 5–100 μM and the limit of detection was 2 μM. The high catalytic activity of Fe3O4@LNPs allows its prospective use in a wide variety of applications, including clinical diagnosis, food safety, and environmental monitoring.

Agradecimentos: The authors acknowledge the financial support of the Brazilian research financing institutions: CNPq, CAPES and FAPESP (2014/26420-9 and 2013/22127-2). SAXS measurements were carried out at LNLS National Laboratory of Synchrotron Light, LNLS-Campinas, Brazil (SAXS1 - Project number 18754). HRTEM and STEM-EDX measurements were carried out at LNNano National Laboratory of Nanotechnology Abstract: We report a novel combination of nanomaterial proposed as a peroxidase-like enzymatic mimic for detection of H2O2, where CeO2 nanoparticles dispersed on SBA-15 through synthesis by the impregnation-decomposition cycles method (IDC). The system displays a good peroxidase-like activity and catalyzes to the oxidation of 3,3',5,5‘-tetramethylbenzidine (TMB) by H2O2. KM values were calculated between 0.04 and 0.08 mM for different (CeO2/SBA-15)x catalyst system, the results demonstrates that the combination of these materials displayed a good affinity to TMB substrate, consequently improving the colorimetric assay, due to uniform mesostructures of SBA-15 and their high surface areas. A detailed study of synergistic effects between CeO2NPs and SBA-15 support were held in order to understand how these effects can improve the colorimetric assay. Additionally, high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, thermogravimetric analysis (TGA), small angle X-ray scattering (SAXS) and textural properties were utilized for characterization of the prepared catalysts systems COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

This work presents the modelling of impulsional pH variations in microvolume related to water-based electrolysis and hydrogen peroxide electrochemical oxidation using an Electrochemical Field Effect Transistor (ElecFET) microdevice. This ElecFET device consists of a pH-Chemical FET (pH-ChemFET) with an integrated microelectrode around the dielectric gate area in order to trigger electrochemical reactions. Combining oxidation/reduction reactions on the microelectrode, water self-ionization and diffusion properties of associated chemical species, the model shows that the sensor response depends on the main influential parameters such as: (i) polarization parameters on the microelectrode, i.e., voltage (Vp) and time (tp), (ii) distance between the gate sensitive area and the microelectrode (d), and (iii) hydrogen peroxide concentration ([H2O2]). The model developed can predict the ElecFET response behaviour and creates new opportunities for H2O2-based enzymatic detection of biomolecules.

Poly(allylamine)–dodecylsulfate complex (PA–DS) is able to form a stable and layered structure onto graphite electrodes and can efficiently retain negatively charged ions like ferrocyanide. In this con- text, Prussian blue (PB) is electrochemically synthesized from a solution containing K3[Fe(CN)6] and FeCl3 at pH 1.7. The electrochemical behavior of the new system is investigated in different supporting electrolytes (K+ and Na+ ) and in acid and neutral media. Remarkable, well-defined and reversible voltam- metric responses are obtained, especially under physiological conditions (neutral pH and 150 mM NaCl). In these conditions, the modified electrode is able to electrocatalyze the reduction of hydrogen peroxide (H2O2) at micromolar levels, with a low detection limit and good sensitivity. These results represent an important improvement regarding further uses of PB in bioanalytical applications. Fil: Gaviglio, Carina del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos Aplicados a la Química Orgánica (i); Argentina. Universidad de Buenos Aires; Argentina Fil: Battaglini, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires; Argentina

Acylated xylan-based magnetic Fe3O4 nanocomposite hydrogels (ACX-MNP-gels) were prepared by fabricating Fe3O4 nanoctahedra in situ within a hydrogel matrix which was synthesized by the copolymerization of acylated xylan (ACX) with acrylamide and N-isopropylacrylamide under ultraviolet irradiation. The size of the Fe3O4 fabricated within the hydrogel matrix could be adjusted through controlling the crosslinking concentrations (C). The magnetic hydrogels showed desirable magnetic and mechanical properties, which were confirmed by XRD, Raman spectroscopy, physical property measurement system, SEM, TGA, and compression test. Moreover, the catalytic performance of the magnetic hydrogels was explored. The magnetic hydrogels (C = 7.5 wt %) presented excellent catalytic activity and provided a sensitive response to H2O2 detection even at a concentration level of 5 × 10−6 mol·L−1. This approach to preparing magnetic hydrogels loaded with Fe3O4 nanoparticles endows xylan-based hydrogels with new promising applications in biotechnology and environmental chemistry.

A síntese de novos materiais e a formação de novas estruturas com características e propriedades específicas são vantajosas no desenvolvimento de sensores aplicados na detecção de substâncias para controle e monitoramento ambiental. Esse trabalho teve como objetivo a manipulação de óxido de grafeno (GO), poli(aminoamina) hidroclorada (PAH) e nanopartículas de ferrita de cobalto (NPs-CoFe2O4) utilizando a técnica de automontagem. Os filmes foram fabricados sobre dispositivos Field-EffectDevices (FED) do tipo Electrolyte-Insulator-Semiconductor (EIS) de estrutura p-SiSiO2-Ta2O5 e utilizados na detecção de peróxido de hidrogênio (H2O2) e íons de metais pesados de Cd2+ e Cu2+. As soluções de NPs-CoFe2O4 e GO foram caracterizadas por microscopia eletrônica de transmissão (TEM), e os filmes foram caracterizados por microscopia eletrônica de varredura com emissão de campo (FEGSEM). Na preparação dos filmes foram utilizadas três diferentes concentrações de GO: 0,1 mg/mL, 0,5 mg/mL e 1,0 mg/mL. Os filmes com arquitetura PAH-CoFe2O4/GO foram caracterizados por técnicas eletroquímicas de capacitância/voltagem (C/V) e capacitância constante (ConCap) para estudo de formação das camadas dos filmes e para detecção de pH, H2O2, Cd2+ e Cu2+. Verificamos que a quantidade ideal de bicamadas a ser depositada sobre os chips foi entre 6 e 10 bicamadas. Detecções de pH mostraram que os filmes preparados com GO em 0,5 mg/mL foram mais sensíveis que os demais preparados com as concentrações em 0,1 mg/mL e 1 mg/mL. Filmes sem a presença das NPs-CoFe2O4 não apresentaram sinais de reposta ao H2O2, demonstrando que a detecção dessa substância está diretamente associada à ferrita. Dentre todos os filmes analisados, o sensor EIS-PAH-CoFe2O4/GO(6bi/0,5) exibiu as melhores propriedades com sinais de resposta estáveis e maiores sensibilidades para as detecções de H2O2 e dos íons Cd2+ e Cu2+. Esses resultados mostram a importância de estudar sistemas de filmes otimizados com arquiteturas adequadas para obter nanoestruturas que possam ser empregadas como unidades de sensor com propriedades melhoradas para a detecção de substâncias de interesse para monitoramento ambiental. The synthesis of new materials and the formation of novel structures with specific features and properties are advantageous in the development of sensors applied to detect substances for the control and environmental monitoring. This study was aimed to nanostructure graphene oxide (GO), poly(aminoamine) hydrochloride (PAH) and cobalt ferrite nanoparticles (NPs-CoFe2O4), by using the layer-by-layer (LbL) technique. The films were fabricated onto Field-Effect-Devices (FED) type ElectrolyteInsulator-Semiconductor (EIS) with p-Si-SiO2-Ta2O5 structure and used to detect hydrogen peroxide (H2O2), and heavy metals of Cd2+ and Cu2+ ions. The NPs-CoFe2O4 and GO solutions were characterized by transmission electron microscopy (TEM), and the films were characterized by scanning electron microscopy with field emission (FEG-SEM). For the preparation of the films we used three different GO concentrations: 0.1 mg/mL, 0.5 mg/mL and 1.0 mg/mL. The films were characterized by electrochemical techniques of capacitance/voltage (C/V) and constant capacitance (ConCap) to investigate an optimal number of bilayers and for detecting pH, H2O2, and Cd2+, Cu2+ ions. The results showed that the optimum number of bilayers to be deposited onto the chips were between 6 and 10 bilayers. pH detections showed that the films prepared with GO at 0.5 mg/mL were more sensitive than others prepared with concentrations at 0.1 mg/mL and 1 mg/mL. Films without the presence of NPsCoFe2O4 revealed no response signals toward H2O2, demonstrating that the detection of such substance is directly associated with the ferrites. For all films, the sensor EISPAH-CoFe2O4/GO(6bi/0,5) exhibited the best properties with stable response signal and higher sensitivity for the detection of H2O2, and Cd2+, Cu2+ ions. These results show the importance of studying optimized films with suitable architectures that lead to nanostructures that may be used as sensing units with enhanced properties for the detection of substances of interest for environmental monitoring.

Acylated xylan-based magnetic Fe3O4 nanocomposite hydrogels (ACX-MNP-gels) were prepared by fabricating Fe3O4 nanoctahedra in situ within a hydrogel matrix which was synthesized by the copolymerization of acylated xylan (ACX) with acrylamide and N-isopropylacrylamide under ultraviolet irradiation. The size of the Fe3O4 fabricated within the hydrogel matrix could be adjusted through controlling the crosslinking concentrations (C). The magnetic hydrogels showed desirable magnetic and mechanical properties, which were confirmed by XRD, Raman spectroscopy, physical property measurement system, SEM, TGA, and compression test. Moreover, the catalytic performance of the magnetic hydrogels was explored. The magnetic hydrogels (C = 7.5 wt %) presented excellent catalytic activity and provided a sensitive response to H2O2 detection even at a concentration level of 5 × 10−6 mol·L−1. This approach to preparing magnetic hydrogels loaded with Fe3O4 nanoparticles endows xylan-based hydrogels with new promising applications in biotechnology and environmental chemistry.

Lignin is the second largest naturally renewable resource and is primarily a by-product of the pulp and paper industry, however, its inefficient use presents a challenge. In this work, Fe3O4 nanoparticles loaded on lignin nanoparticles (Fe3O4@LNPs) were prepared by the self-assembly method and it possessed an enhanced peroxidase-like activity. Fe3O4@LNPs catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue color, was observable by the naked eye. Under the optimal conditions, Fe3O4@LNPs showed the ability of sensitive colorimetric detection of H2O2within a range of 5&ndash, 100 &mu, M and the limit of detection was 2 &mu, M. The high catalytic activity of Fe3O4@LNPs allows its prospective use in a wide variety of applications, including clinical diagnosis, food safety, and environmental monitoring.

International audience; For the first time quantitative measurements of the hydroperoxyl radical (HO2) in a jet-stirred reactor were performed thanks to a new experimental setup involving fast sampling and near-infrared cavity ring down spectroscopy at low pres-sure. The experiments were performed at atmospheric pres-sure and over a range of temperatures (550-900 K) with n-butane, the simplest hydrocarbon fuel exhibiting cool flame oxidation chemistry which represents a key-process for the auto-ignition in internal combustion engines. The same tech-nique was also used to measure H2O2, H2O, CH2O, and C2H4 under the same conditions. This new set-up brings new scientific horizons for characterizing complex reactive sys-tems at elevated temperatures. Measuring HO2 formation from hydrocarbon oxidation is extremely important in deter-mining the propensity of a fuel to follow chain-termination pathways from R + O2 compared to chain-branching (leading to OH), helping to constrain and better validate detailed chemical kinetics models.

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.

Here we report the derivatization of mesoporous TiO2 thin films for the preparation of H2O2 amperometric sensors. The coordination of the bifunctional ligand 1,10 phenantroline, 5,6 dione on the surface Ti(IV) ions provides open coordination sites for Fe(II) cations which are the starting point for the growth of a layer of Prussian blue polymer. The porous structure of the mesoporous TiO2 allows the growth, ion by ion of the coordination polymer. Up to four layer of Prussian blue can be deposit without losing the porous structure of the film, which results in an enhanced response of these materials as H2O2 sensors. These porous confined PB modified electrodes are robust sensors that exhibit good reproducibility, environmental stability and high sensitivity towards H2O2 detection. © 2010 Elsevier B.V. Fil: Gaitán, Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Gonçales, Vinicius R.. Universidade de Sao Paulo; Brasil Fil: Soler Illia, Galo Juan de Avila Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Baraldo Victorica, Luis Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Córdoba de Torresi, Susana I.. Universidade de Sao Paulo; Brasil