Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 32
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
Anal Chem ; 91(23): 14951-14959, 2019 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-31691565

RESUMO

Here, we provide the first experimental evidence of proton release from polyaniline (PANI) films subjected to anodic potentials at environmental pHs. We conducted an extensive characterization of unpolarized/polarized PANI films-synthesized by traditional sequential voltammetric scanning-by using spectroelectrochemistry, synchrotron radiation-X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure, and potentiometric pH sensing in the vicinity of the PANI layer. This new insight enables the utilization of PANI as a proton pump, which is actively tuned through an electrochemical pulse, so as to controllably acidify well-confined thin layer samples. Furthermore, we demonstrate the analytical significance of this system by measuring the alkalinity of artificial and natural water samples by using two faced planar PANI electrodes, one working as a proton source and the other one as pH electrode. Finally, the impact of this approach is 2-fold: (i) all-solid-state electrode materials may be used with devisible consequences in miniaturized and implementable submersible probes, and (ii) rapid determination of alkalinity as compared to traditional approaches together with a versatility in pH adjustment in any kind of sample, among other applications.

2.
Angew Chem Int Ed Engl ; 58(52): 19027-19033, 2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31617301

RESUMO

Water-splitting photoanodes based on semiconductor materials typically require a dopant in the structure and co-catalysts on the surface to overcome the problems of charge recombination and high catalytic barrier. Unlike these conventional strategies, a simple treatment is reported that involves soaking a sample of pristine BiVO4 in a borate buffer solution. This modifies the catalytic local environment of BiVO4 by the introduction of a borate moiety at the molecular level. The self-anchored borate plays the role of a passivator in reducing the surface charge recombination as well as that of a ligand in modifying the catalytic site to facilitate faster water oxidation. The modified BiVO4 photoanode, without typical doping or catalyst modification, achieved a photocurrent density of 3.5 mA cm-2 at 1.23 V and a cathodically shifted onset potential of 250 mV. This work provides an extremely simple method to improve the intrinsic photoelectrochemical performance of BiVO4 photoanodes.

3.
Adv Sci (Weinh) ; 6(10): 1802066, 2019 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-31131190

RESUMO

Iron single atom catalysts (Fe SACs) are the best-known nonprecious metal (NPM) catalysts for the oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells (PEMFCs), but their practical application has been constrained by the low Fe SACs loading (<2 wt%). Here, a one-pot pyrolysis method is reported for the synthesis of iron single atoms on graphene (FeSA-G) with a high Fe SAC loading of ≈7.7 ± 1.3 wt%. The as-synthesized FeSA-G shows an onset potential of 0.950 V and a half-wave potential of 0.804 V in acid electrolyte for the ORR, similar to that of Pt/C catalysts but with a much higher stability and higher phosphate anion tolerance. High temperature SiO2 nanoparticle-doped phosphoric acid/polybenzimidazole (PA/PBI/SiO2) composite membrane cells utilizing a FeSA-G cathode with Fe SAC loading of 0.3 mg cm-2 delivers a peak power density of 325 mW cm-2 at 230 °C, better than 313 mW cm-2 obtained on the cell with a Pt/C cathode at a Pt loading of 1 mg cm-2. The cell with FeSA-G cathode exhibits superior stability at 230 °C, as compared to that with Pt/C cathode. Our results provide a new approach to developing practical NPM catalysts to replace Pt-based catalysts for fuel cells.

4.
Adv Mater ; 30(13): e1706287, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29423964

RESUMO

Single-atom catalysts (SACs) are the smallest entities for catalytic reactions with projected high atomic efficiency, superior activity, and selectivity; however, practical applications of SACs suffer from a very low metal loading of 1-2 wt%. Here, a class of SACs based on atomically dispersed transition metals on nitrogen-doped carbon nanotubes (MSA-N-CNTs, where M = Ni, Co, NiCo, CoFe, and NiPt) is synthesized with an extraordinarily high metal loading, e.g., 20 wt% in the case of NiSA-N-CNTs, using a new multistep pyrolysis process. Among these materials, NiSA-N-CNTs show an excellent selectivity and activity for the electrochemical reduction of CO2 to CO, achieving a turnover frequency (TOF) of 11.7 s-1 at -0.55 V (vs reversible hydrogen electrode (RHE)), two orders of magnitude higher than Ni nanoparticles supported on CNTs.

5.
ACS Appl Mater Interfaces ; 9(37): 31922-31930, 2017 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-28857542

RESUMO

As differentiated from conventional synthetic processes, amino-functionalized hollow mesoporous silica (NH2-HMS) has been synthesized using a new and facile strategy of ion-exchange-induced selective etching of amino-functionalized mesoporous silica (NH2-meso-silica) by an alkaline solution. Nuclear magnetic resonance (NMR) spectroscopy and in situ time-resolved small-angle X-ray scattering (SAXS) reveal that ion-exchange-induced selective etching arises from the gradient distribution of OH- in the NH2-meso-silica nanospheres. Moreover, the ion-exchange-induced selective etching mechanism is verified through a successful synthesis of hollow mesoporous silica. After infiltration with phosphotungstic acid (PWA), PWA-NH2-HMS nanoparticles are dispersed in the poly(ether sulfone)-polyvinylpyrrolidone (PES-PVP) matrix, forming a hybrid PWA-NH2-HMS/PES-PVP nanocomposite membrane. The resultant nanocomposite membrane with an optimum loading of 10 wt % of PWA-NH2-HMS showed an enhanced proton conductivity of 0.175 S cm-1 and peak power density of 420 mW cm-2 at 180 °C under anhydrous conditions. Excellent durability of the hybrid composite membrane fuel cell has been demonstrated at 200 °C. The results of this study demonstrated the potential of the facile synthetic strategy in the fabrication of NH2-HMS with controlled mesoporous structure for application in nanocomposite membranes as a technology platform for elevated-temperature proton exchange membrane fuel cells.

6.
Anal Chem ; 89(6): 3508-3516, 2017 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-28194968

RESUMO

To understand the rate determining processes during the equilibration of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-based (PEDOT(PSS)-based) solid contact (SC) ion-selective electrodes (ISEs), the surfaces of Pt, Au, and GC electrodes were coated with 0.1, 1.0, 2.0, and 4.0 µm thick galvanostatically deposited PEDOT(PSS) films. Next, potential vs time transients were recorded with these electrodes, with and without an additional potassium ion-selective membrane (ISM) coating, following their first contact with 0.1 M KCl solutions. The transients were significantly different when the multilayered sensor structures were assembled on Au or GC compared to Pt. The differences in the rate of equilibration were interpreted as a consequence of differences in the hydrophilicity of PEDOT(PSS) in contact with the substrate electrode surfaces based on X-ray photoelectron spectroscopy (XPS) and synchrotron radiation-XPS (SR-XPS) analysis of 10-100 nm thick PEDOT(PSS) films. The influence of the layer thickness of the electrochemically deposited PEDOT(PSS)-films on the hydrophilicity of these films has been documented by contact angle measurements over PEDOT(PSS)-coated Au, GC, and Pt electrode surfaces. This study demonstrates that it is possible to minimize the equilibration (conditioning) time of SC ISEs with aqueous solutions before usage by optimizing the thickness of the SC layer with a controlled ISM thickness. PEDOT(PSS)-coated Au and GC electrodes exhibit a significant negative potential drift during their equilibration in an aqueous solution. By coating the PEDOT(PSS) surface with an ISM, the negative potential drift is compensated by a positive potential drift related to the hydration of the ISM and activity changes at the PEDOT(PSS)|ISM interface. The potential drifts related to activity changes in the ISM have been determined by a novel adaptation of the "sandwich membrane" method.

7.
Chem Commun (Camb) ; 52(62): 9703-6, 2016 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-27405722

RESUMO

This paper presents the first direct spectroscopic evidence for double layer or capacitive charging of carbon nanomaterial-based solid contacts in all-solid-state polymeric ion-selective electrodes (ISEs). Here, we used synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and SR valence band (VB) spectroscopy in the elucidation of the charging mechanism of the SCs.

8.
Anal Chem ; 88(13): 6939-46, 2016 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-27266678

RESUMO

We report on the limiting conditions for ion-transfer voltammetry between an ion-exchanger doped and plasticized poly(vinyl chloride) (PVC) membrane and an electrolyte solution that was triggered via the oxidation of a poly(3-octylthiophene) (POT) solid-contact (SC), which was unexpectedly related to the thickness of the POT SC. An electropolymerized 60 nm thick film of POT coated with a plasticized PVC membrane exhibited a significant sodium transfer voltammetric signal whereas a thicker film (180 nm) did not display a measurable level of ion transfer due to a lack of oxidation of thick POT beneath the membrane film. In contrast, this peculiar phenomenon was not observed when the POT film was in direct contact with an organic solvent-based electrolyte. This evidence is indicative of three key points: (i) the coated membrane imposes a degree of rigidity to the system, which restricts the swelling of the POT film and its concomitant p-doping; (ii) this phenomenon is exacerbated with thicker POT films due to an initial morphology (rougher comprising a network of large POT nanoparticles), which gives rise to a diminished surface area and electrochemical reactivity in the POT SC; (iii) the rate of sodium transfer is higher with a thin POT film due to a smoother surface morphology made up of a network of smaller POT nanoparticles with an increased surface area and electrochemical reactivity. A variety of techniques including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry, scanning electron microscopy (SEM), atomic force microscopy (AFM), and synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) were used to elucidate the mechanism of the POT thickness/POT surface roughness dependency on the electrochemical reactivity of the PVC/POT SC system.

9.
Langmuir ; 31(38): 10599-609, 2015 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-26327251

RESUMO

The transportation and accumulation of redox active species at the buried interface between glassy carbon electrodes and plasticized polymeric membranes have been studied using synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS), near edge X-ray absorption fine structure (NEXAFS), in situ electrochemical Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). Ferrocene tagged poly(vinyl chloride) [FcPVC], ferrocene (Fc), and its derivatives together with tetracyanoquinodimethane (TCNQ) doped plasticized polymeric membrane electrodes have been investigated, so as to extend the study of the mechanism of this reaction chemistry to different time scales (both small and large molecules with variable diffusion coefficients) using a range of complementary electrochemical and surface analysis techniques. This study also provides direct spectroscopic evidence for the transportation and electrochemical reactivity of redox active species, regardless of the size of the electrochemically reactive molecule, at the buried interface of the substrate electrode. With all redox dopants, when CA electrolysis was performed, redox active species were undetectable (<1 wt % of signature elements or below the detection limit of SR-XPS and NEXAFS) in the outermost surface layers of the membrane, while a high concentration of redox species was located at the electrode substrate as a consequence of the deposition of the reaction product (Fc(+)-anion complex) at the buried interface between the electrode and the membrane. This reaction chemistry for redox active species within plasticized polymeric membranes may be useful in the fashioning of multilayered polymeric devices (e.g., chemical sensors, organic electronic devices, protective laminates, etc.) based on an electrochemical tunable deposition of redox molecules at the buried substrate electrode beneath the membrane.


Assuntos
Carbono/química , Plastificantes/química , Polímeros/química , Eletrodos , Oxirredução , Propriedades de Superfície
10.
Anal Chim Acta ; 851: 78-86, 2014 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-25440668

RESUMO

Three new calixarene Tl(+) ionophores have been utilized in Tl(+) ion-selective electrodes (ISEs) yielding Nernstian response in the concentration range of 10(-2)-10(-6)M TlNO3 with a non-optimized filling solution in a conventional liquid contact ISE configuration. The complex formation constants (logßIL) for two of the calixarene derivatives with thallium(I) (i.e. 6.44 and 5.85) were measured using the sandwich membrane technique, with the other ionophore immeasurable due to eventual precipitation of the ionophore during these long-term experiments. Furthermore, the unbiased selectivity coefficients for these ionophores displayed excellent selectivity against Zn(2+), Ca(2+), Ba(2+), Cu(2+), Cd(2+) and Al(3+) with moderate selectivity against Pb(2+), Li(+), Na(+), H(+), K(+), NH4(+) and Cs(+), noting that silver was the only significant interferent with these calixarene-based ionophores. When optimizing the filling solution in a liquid contact ISE, it was possible to achieve a lower limit of detection of approximately 8nM according to the IUPAC definition. Last, the new ionophores were also evaluated in four solid-contact (SC) designs leading to Nernstian response, with the best response noted with a SC electrode utilizing a gold substrate, a poly(3-octylthiophene) (POT) ion-to-electron transducer and a poly(methyl methacrylate)-poly(decyl methacrylate) (PMMA-PDMA) co-polymer membrane. This electrode exhibited a slope of 58.4mVdecade(-1) and a lower detection limit of 30.2nM. Due to the presence of an undesirable water layer and/or leaching of redox mediator from the graphite redox buffered SC, a coated wire electrode on gold and graphite redox buffered SC yielded grossly inferior detection limits against the polypyrrole/PVC SC and POT/PMMA-PDMA SC ISEs that did not display signs of a water layer or leaching of SC ingredients into the membrane.


Assuntos
Calixarenos/química , Eletrodos Íon-Seletivos , Tálio/análise , Acrilamidas/química , Interações Hidrofóbicas e Hidrofílicas , Ionóforos/química , Limite de Detecção , Membranas Artificiais , Polimetil Metacrilato/química , Tálio/química
11.
Anal Chem ; 85(21): 10495-502, 2013 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-24080025

RESUMO

The ion-to-electron transduction reaction mechanism at the buried interface of the electrosynthesized poly(3-octylthiophene) (POT) solid-contact (SC) ion-selective electrode (ISE) polymeric membrane has been studied using synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS), near edge X-ray absorption fine structure (NEXAFS), and electrochemical impedance spectroscopy (EIS)/neutron reflectometry (NR). The tetrakis[3,5-bis(triflouromethyl)phenyl]borate (TFPB(-)) membrane dopant in the polymer ISE was transferred from the polymeric membrane to the outer surface layer of the SC on oxidation of POT but did not migrate further into the oxidized POT SC. The TFPB(-) and oxidized POT species could only be detected at the outer surface layer (≤14 Ǻ) of the SC material, even after oxidation of the electropolymerized POT SC for an hour at high anodic potential demonstrating that the ion-to-electron transduction reaction is a surface confined process. Accordingly, this study provides the first direct structural evidence of ion-to-electron transduction in the electropolymerized POT SC ISE by proving TFPB(-) transport from the polymeric ISE membrane to the oxidized POT SC at the buried interface of the SC ISE. It is inferred that the performance of the POT SC ISE is independent of the thickness of the POT SC but is instead contingent on the POT SC surface reactivity and/or electrical capacitance of the POT SC. In particular, the results suggest that the electropolymerized POT conducting polymer may spontaneously form a mixed surface/bulk oxidation state, which may explain the unusually high potential stability of the resulting ISE. It is anticipated that this new understanding of ion-to-electron transduction with electropolymerized POT SC ISEs will enable the development of new and improved devices with enhanced analytical performance attributes.


Assuntos
Elétrons , Eletrodos Íon-Seletivos , Polímeros/química , Tiofenos/química , Propriedades de Superfície
12.
ACS Appl Mater Interfaces ; 5(21): 11240-8, 2013 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-24125494

RESUMO

A novel inorganic proton exchange membrane based on phosphoric acid (PA)-functionalized sintered mesoporous silica, PA-meso-silica, has been developed and investigated. After sintering at 650 °C, the meso-silica powder forms a dense membrane with a robust and ordered mesoporous structure, which is critical for retention of PA and water within the porous material. The PA-meso-silica membrane achieved a high proton conductivity of 5 × 10(-3) to 5 × 10(-2) S cm(-1) in a temperature range of 80-220 °C, which is between 1 and 2 orders of magnitudes higher than a typical membrane Nafion 117 or polybenzimidazole (PBI)/PA in the absence of external humidification. Furthermore, the PA-meso-silica membranes exhibited good chemical stability along with high performance at elevated temperatures, producing a peak power density of 632 mW cm(-2) using a H2 fuel at 190 °C in the absence of external humidification. The high membrane proton conductivity and excellent fuel cell performance demonstrate the utility of PA-meso-silica as a new class of inorganic proton exchange membranes for use in the high-temperature proton exchange membrane fuel cells (PEMFCs).

13.
Analyst ; 138(15): 4266-9, 2013 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-23714844

RESUMO

Cyclic voltammetry (CV), synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and near edge X-ray absorption fine structure (NEXAFS) show that oxidation of ferrocene tagged PVC induces an accumulation of high molecular weight polymer at the buried interface between the substrate electrode and the plasticized membrane.


Assuntos
Compostos Ferrosos/metabolismo , Plastificantes/química , Cloreto de Polivinila/metabolismo , Transporte Biológico/fisiologia , Eletrodos , Compostos Ferrosos/análise , Metalocenos , Espectroscopia Fotoeletrônica/métodos , Cloreto de Polivinila/análise
14.
Chem Commun (Camb) ; 49(41): 4655-7, 2013 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-23579968

RESUMO

An inorganic proton exchange membrane based on sintered mesoporous silica and phosphoric acid was developed with a high proton conductivity of 0.06 S cm(-1) at 200 °C, achieving an excellent power output of 689 mW cm(-2) in H2 at 190 °C and 200 mW cm(-2) in methanol at 200 °C with no external humidification.


Assuntos
Ácidos Fosfóricos/química , Dióxido de Silício/química , Espectroscopia Dielétrica , Condutividade Elétrica , Eletrólitos/química , Metanol/química , Porosidade , Prótons , Temperatura
15.
Phys Chem Chem Phys ; 15(5): 1364-8, 2013 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-23247387

RESUMO

Resistivities of thin polymer films increase abruptly with decreasing thickness, although the corresponding decline in resistance plateaus below a certain thickness. One can jump to the incorrect conclusion that quantum confinement and surface scattering are responsible for this behaviour, and we highlight the pitfalls of committing such an error.


Assuntos
Polímeros/química , Transporte de Elétrons , Polimetil Metacrilato/química , Teoria Quântica , Propriedades de Superfície
16.
Anal Chim Acta ; 744: 39-44, 2012 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-22935372

RESUMO

A nitrate ion-selective electrode (ISE) employing a permeable tubular membrane impregnated with a conventional ISE cocktail has been used successfully in the coulometric analysis of nitrate in fresh waters. The liquid ISE membrane comprising a nitrate ionophore [tridodecylmethylammonium nitrate (TDMAN)], lipophilic electrolyte [tetradodecyl-ammoniumtetrakis(4-chlorophenyl)borate (ETH 500)] and plasticizer [bis(3-ethyl-hexyl)sebacate (DOS)] was supported on a porous polypropylene tube. Coulometric analysis with the tubular membrane ISE showed that nitrate could be detected in the range 10-100 µM with a precision of 2.3% relative standard deviation (RSD), limit of detection of 1.1 µM and relative accuracy of 4.4% compared to a certified reference material (CRM) Lake sample.

17.
Anal Chem ; 84(14): 6158-65, 2012 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-22703479

RESUMO

Seawater analysis is one of the most challenging in the field of environmental monitoring, mainly due to disparate concentration levels between the analyte and the salt matrix causing interferences in a variety of analytical techniques. We propose here a miniature electrochemical sample pretreatment system for a rapid removal of NaCl utilizing the coaxial arrangement of an electrode and a tubular Nafion membrane. Upon electrolysis, chloride is deposited at the Ag electrode as AgCl and the sodium counterions are transported across the membrane. This cell was found to work efficiently at potentials higher than 400 mV in both stationary and flow injection mode. Substantial residual currents observed during electrolysis were found to be a result of NaCl back diffusion from the outer side of the membrane due to insufficient permselectivity of the Nafion membrane. It was demonstrated that the residual current can be significantly reduced by adjusting the concentration of the outer solution. On the basis of ion chromatography results, it was found that the designed cell used in flow injection electrolysis mode reduced the NaCl concentration from 0.6 M to 3 mM. This attempt is very important in view of nutrient analysis in seawater where NaCl is a major interfering agent. We demonstrate that the pretreatment of artificial seawater samples does not reduce the content of nitrite or nitrate ions upon electrolysis. A simple diffusion/extraction steady state model is proposed for the optimization of the electrolysis cell characteristics.

18.
Analyst ; 136(16): 3252-8, 2011 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-21735000

RESUMO

Solid-contact (SC) ion-selective electrodes (ISEs) utilizing thin films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and plasticized poly(vinylchloride) (PVC) have been produced using a spin casting procedure. This study was carried out with a view of characterizing this popular and well known SC ISE using a series of complementary surface analysis techniques. This work revealed that PEDOT:PSS prevents the separation of an undesirable water layer at the buried interface of this SC ISE due to the high miscibility of water in the hydrophilic PEDOT:PSS layer. The lack of a clearly defined and molecularly sharp buried interface prohibits the formation of a distinct water layer presumably by eliminating sites that promote the accumulation of water. This outcome is important to the chemical sensor community since it provides further insights into the compatibility of sensor components in SC ISEs.

19.
Phys Chem Chem Phys ; 13(10): 4400-10, 2011 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-21249246

RESUMO

Both Keggin-type phosphotungstic acid (HPW) and Pd are not prominent catalysts towards the oxygen reduction (ORR), but their composite Pd-HPW catalyst produces a significantly higher electrochemical activity for the ORR in acidic media. The novel composite catalyst was synthesized by self-assembly of HPW on multi-walled carbon nanotubes (MWCNTs) via the electrostatic attraction between negatively charged HPW and positively charged poly(diallyldimethylammonium (PDDA)-wrapped MWCNTs, followed by dispersion of Pd nanoparticles onto the HPW-PDDA-MWCNT assembly. The as-prepared catalyst was characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). TEM images show that Pd nanoparticles were uniformly dispersed on the surface of MWCNTs even when the Pd loading was increased to 60 wt%. Electrochemical activity of the catalysts for the ORR was evaluated by steady state polarization measurements using a rotating disk electrode. Compared with the acid treated MWCNTs, Pd nanoparticles supported on the HPW-assembled MWCNTs show a much higher ORR activity that is comparable to conventional Pt/C catalysts. The high electrocatalytic activities could be related to high dispersion of Pd nanoparticles as well as synergistic effects originating from the high proton conductivity of HPW. The Pd/HPW-PDDA-MWCNTs system as the cathode catalyst in proton exchange membrane fuel cells is demonstrated.

20.
Anal Chem ; 82(14): 6203-7, 2010 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-20557118

RESUMO

This paper reports on three-dimensional synchrotron radiation/Fourier transform-infrared microspectroscopy (SR/FT-IRM) imaging studies of water inclusions at the buried interface of solid-contact-ion-selective electrodes (SC-ISEs). It is our intention to describe a nondestructive method that may be used in surface studies of the buried interfaces of materials, especially multilayers of polymers. Herein, we demonstrate the power of SR/FT-IRM for studying water inclusions at the buried interfaces of SC-ISEs. A poly(methyl methacrylate)-poly(decyl methacyrlate) [PMMA-PDMA] copolymer revealed the presence of micrometer sized inclusions of water at the gold/membrane interface, while a coupling of a hydrophobic solid contact of poly(3-octylthiophene 2,5-diyl) (POT) prevented the accumulation of water at the buried interface. A similar study with a poly (3,4-ethylenedioxythiophene)/poly (styrenesulfonate) [PEDOT/PSS] solid contact also revealed an absence of distinct micrometer-sized pools of water; however, there were signs of absorption of water accompanied by swelling of the PEDOT/PSS underlayer, and these membrane zones are enriched with respect to water.


Assuntos
Polímeros/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Síncrotrons , Água/química , Ouro/química , Eletrodos Íon-Seletivos , Tiofenos/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA