Solid State Electrochemical Techniques Research Articles

Gold Nanoparticle-Loaded Silica Nanospheres for Sensitive and Selective Electrochemical Detection of Bisphenol A.

In this work, silica nanospheres were used as support for gold nanoparticles and applied for bisphenol A electrochemical detection. The development of new silica-supported materials has attracted increasing attention in the scientific world. One approach of interest is using silica nanospheres as support for gold nanoparticles. These materials have a variety of applications in several areas, such as electrochemical sensors. The obtained materials were characterized by solid-state UV-vis spectroscopy, electron microscopy, X-ray diffraction, and electrochemical techniques. The electrode modified with AuSiO2700/CHI/Pt was applied as an electrochemical sensor for BPA, presenting an oxidation potential of 0.842 V and a higher peak current among the tested materials. The AuSiO2700/CHI/Pt electrode showed a logarithmic response for the detection of BPA in the range of 1-1000 nmol L-1, with a calculated detection limit of 7.75 nmol L-1 and a quantification limit of 25.8 nmol L-1. Thus, the electrode AuSiO2700/CHI/Pt was presented as a promising alternative to an electrochemical sensor in the detection of BPA.

Enhanced adsorption-catalysis combination for the removal of sulphur from fuels using polyoxometalates supported on amphipathic hybrid mesoporous silica nanoparticles.

Polyoxometalate (POM) mesoporous silica-based materials with a low POM loading have been designed with hydrophilic and hydrophobic properties. These materials act as powerful heterogeneous catalysts in oxidative desulfurization (ODS), owing to their ability to adsorb both H2O2 and sulphur-containing compounds from the model oil simultaneously. The formation of charge transfer salts through ion pair interaction with a choline functionality, available on the hybrid silica support, affords robust and recyclable heterogeneous catalysts for the ODS process under mild conditions (45 min and 40 °C). Besides, the nature of the polyoxometalate anions is highly dependent on the characteristics of the silica surface. The masking of silanol groups present on the silica surface using silylating agents, with diverse reactivity and steric hindrance, influences the silica surface-heteropolyanion interactions, as well as heteropolyanion-heteropolyanion interactions. In addition, it modifies the hydrophobic properties of the surface, which is a determining factor in the adsorption properties of non-polar dibenzothiophene (DBT) by the catalysts. Adsorption, an anterior step to the oxidation reaction, has been demonstrated to be key to the superior activity of POM-SiMe3-Chol-MSN, where the silanol groups have been capped by trimethylsilyl groups. For the first time, and to better understand POM-surface and POM-POM anion interactions, an extensive characterization of the materials has been performed using 13C, 31P, and 95Mo MAS NMR spectroscopy and solid-state electrochemical techniques, among others.

Multiple-scan voltammetry and OCP: Archaeometric tools for dating archaeological bronzes

The application of a multiple-scan strategy to nanosamples taken from 18 cross-sections of Bronze Age arms and armour, as well as two Roman coins using two solid-state electrochemical techniques, the voltammetry of immobilized microparticles (VIMP) and open circuit potential measurements (OCP) is described. The voltammetric responses in contact with aqueous acetate buffer can be attributed to the reduction of cuprite with variable degree of compaction and crystallinity revealing significant differences in the gradient of such properties with depth. Such differences are also revealed by “dry” OCP measurements connecting points in the cross section near and separated from the corrosion layer. The voltammetric study of the metallographic samples of the bronze objects shows correlation with the age of the objects, respectively the period of their deposition. We discuss also (potential) influence of different factors on the VIMP and OCP measurements, such as deposition context (soil, water), chemical composition of the copper alloys, and microstructural features (as-cast, annealed, work-hardened), and how to overcome these issues.

Stability studies and magnetic behaviour of rhodium vanadate

Rhodium vanadate an important catalytic compound was synthesized by solid state reaction route and characterized by X-ray diffraction. The standard molar Gibbs energy of formation of rhodium vanadate was determined using solid state electrochemical technique employing a calcia stabilized zirconia (CSZ) oxide ion conducting electrolyte. The Gibbs energy of formation was determined from electromotive force measurements carried out in the temperature range from 959 K to 1137 K.Magnetic measurements using a Vibration Sample Magnetometer (VSM) in the temperature range from 4 K to 300 K under the influence of a magnetic field of 1 kOe was carried out. The measurements concluded that the compound RhVO4(s) shows paramagnetic behavior. The magnetization measured at 1.8 K under a changing magnetic field shows a very narrow and symmetric loop that further reiterates the above conclusion.

Heterogeneous oxidative desulfurization catalysed by titanium grafted mesoporous silica nanoparticles containing tethered hydrophobic ionic liquid: A dual activation mechanism

In this study, heterogeneous catalysts containing ionic liquid and/or titanium have been prepared and used for oxidative desulfurization. For the synthesis of hybrid mesoporous silica nanoparticles (ILBF4-MSN), a grafting method has been employed with the ionic liquid 1-octyl-3-(3-(triethoxysilyl)propyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate (ILBF4) which contains a long alkyl chain. Titanium hybrid mesoporous silica nanoparticles (ILBF4-x%TiCp2-MSN) and mesoporous silica nanoparticles containing titanium (TiCp2-MSN) have also been prepared using titanocene dichloride. The catalyst containing ionic liquid and titanium, ILBF4-3%TiCp2-MSN exhibited the highest desulfurization efficiency (99.1%) in model oil with high concentration of DBT and using H2O2 as oxidant. In addition, the effect of immobilization of the ionic liquid on titanium materials has been investigated by solid-state 13C, 47/49Ti and 19F NMR spectroscopy and solid state electrochemical techniques. The titanium species and ionic liquid play an important role in the oxidative desulfurization reaction since they might activate synergistically sulfur derivatives and enhance the process.

(Keynote) A Solid State Electrochemist’s View on the Requirements for Solid State Electrolytes and Electrodes for All-Solid-State Battery Applications

The advantages of solid electrolytes for new generations of high performance batteries are generally recognized. But these materials alone have no practical importance. Only suitable combinations of materials with well selected kinetic and thermodynamic properties are relevant and quite different features of solid state compared to liquid phase electrochemistry have to be taken into account. These requirements and an insight into the fundamental processes of cell operation will be discussed in terms of the various electrical and thermodynamic potentials. Electrons are often neglected, but play a most important role in the performance for both solid electrolytes and electrodes. Further, solid state electrochemical techniques will be discussed for enhancing and optimizing the search for suitable materials combinations for practical applications.

Microchemical surface analysis of historic copper-based coins by the combined use of FIB-FESEM-EDX, OM, FTIR spectroscopy and solid-state electrochemical techniques

A multi-technique strategy, including microscopy, spectroscopic and electrochemical techniques, is proposed to study thin corrosion layers that form on the surface of historic copper-based coins. An accurate characterisation of this external corrosion layer is important for selecting a suitable conservation and/or restoration treatment. For this purpose, a series of copper-based coins from different historical periods and provenances, which mainly exhibited atmospheric corrosion, was analysed. The morphology of the corrosion layer and the upper core of coins was studied in trenches done on coin surfaces with a focused ion beam gun, coupled to a field emission scanning electron microscope- X-ray microanalysis (FIB-FESEM-EDX). The X-ray microanalysis performed with FESEM-EDX on trenches allowed elemental composition profiles on the corrosion layer to be obtained. These results were complemented with the compositional data of the corrosion products provided by the voltammetry of immobilised microparticles (VIMP) and Fourier transform infrared spectroscopy (FTIR), and by studying visual appearance by optical microscopy and colorimetry. Cuprite and tenorite (the latter increased with coin age) were the main identified corrosion products, which were accompanied, to a lesser extent, by copper trihydroxychloride polymorphs. Interestingly, metal oxalates and metal-carboxylate complexes were identified on the corrosion layer of most coins. These unusual alteration products of copper-based coins were formed from the organic matter deposited on coin surfaces given their use when placed in circulation or by further manipulations of collectors.

Thermodynamic properties of Pr7O12

To explore the potential of Pr7O12 in a biphasic oxygen buffer in automobile exhaust control systems, thermodynamic data for Pr7O12 are required. Since there is no information on Pr7O12 in thermodynamic data compilations, its Gibbs energy of formation has been determined relative to that of Pr2O3 as a function of temperature in the range from 850 to 1200 K using a solid-state electrochemical technique. The standard molar Gibbs energy of formation of Pr7O12 from elements can be represented by two equations. In the range from 850 to 1068 K, ΔGf°Jmol-1=-6454317+1085.52T/K. From 1068 to 1204 K, ΔGf°Jmol-1=-6467695+1097.77T/K.

Selective oxidation of thioanisole by titanium complexes immobilized on mesoporous silica nanoparticles: elucidating the environment of titanium(iv) species

The coordination environment of titanium of the catalysts was investigated by DRUV–vis, Raman and 47/49Ti MAS-NMR spectroscopies and solid-state electrochemical techniques.

Differential scanning calorimetric measurements and thermodynamic functions of YbRhO3(s)

Abstract

Mesoporous SBA-15 modified with titanocene complexes and ionic liquids: interactions with DNA and other molecules of biological interest studied by solid state electrochemical techniques.

The immobilization of two titanocene complexes on SBA-15 has been accomplished following post-synthetic procedures. The ionic liquid, 1-methyl-3-[(triethoxysilyl)propyl]imidazolium chloride, has also been incorporated into the titanium containing materials to determine its influence on the interaction with molecules of biological interest. Cyclic voltammetry has been used to study the influence of the ionic liquid on the mechanism of reduction of titanocene derivatives. The interaction of titanocene and titanocene/ionic liquid-containing mesoporous silica SBA-15 materials, with molecules of biological interest associated with important processes of metallodrug action against cancer cells, has been studied. Thus, we have carried out hydrolysis experiments on the materials functionalized with titanocene derivatives in physiological media to determine their stability and the interaction with serum/transport proteins such as transferrin and BSA and with target molecules such as guanosine, single-stranded DNA and double-stranded DNA by means of solid state voltammetry techniques. A qualitative analysis of the data based on peak current and reduction potential value changes of the couple Ti(iv)/Ti(iii) in the presence of biomolecules at physiological pH, has revealed that grafted titanocene complexes show higher affinity for serum/transport proteins than for nucleic acids, indicating that the transport steps to the cells may be easier than the subsequent attack on DNA.

Electrochemical monitoring of ROS generation by anticancer agents: the case of chartreusin

Generation of ROS by anticancer agents is monitored using solid state electrochemical techniques.

Detecting and Monitoring the Production of Melatonin and Other Related Indole Compounds in Different Saccharomyces Strains by Solid-State Electrochemical Techniques

Recently, melatonin (Mel) has been detected in wine, and as its quantity increases during alcoholic fermentation, yeasts are primarily responsible for its production during the process. L-tryptophan (L-Trp) is an indolic molecule that plays an important role as a precursor of a large amount of tryptamine molecules, including Mel. We propose a novel method for detecting Mel and other derived indole compounds directly on yeast cells based on the voltammetry of immobilized particles methodology. This will abridge and facilitate the detection of these highly conserved and electroactive molecules. Tafel and modified Tafel analyses have been used to distinguish among Mel, tryptophol, and indole-3-acetic acid. We obtained different voltammetry responses in various Saccharomyces strains treated with L-Trp, 5-hydroxytryptophan, and serotonin and without them. The different responses allowed us to assess the production of indole compounds from L-Trp and other precursors. The voltammetric changes in mutant strains with deleted genes of tryptophan metabolism were also tested.

ChemInform Abstract: Exploiting Redox Activity in Metal—Organic Frameworks: Concepts, Trends and Perspectives

AbstractReview: 167 refs.

Exploiting redox activity in metal-organic frameworks: concepts, trends and perspectives.

Of the many thousands of new metal-organic frameworks (MOFs) that are now discovered each year, many possess potential redox activity arising from the constituent metal ions and/or organic ligands, or the guest molecules located within their porous structures. Those redox states that can be accessed via postsynthetic redox modulation often possess distinct physical properties; if harnessed, these provide a basis for applications including microporous conductors, electrocatalysts, energy storage devices and electrochemical sensors, amongst others. This feature article highlights the latest developments in experimental, theoretical and computational concepts relevant to redox-active MOFs, including new solid state electrochemical and spectroelectrochemical techniques that have great utility in this field. A particular emphasis is on current and emerging trends at the fundamental level which underscore the importance of this promising class of electroactive materials for a wide range of technologically- and industrially-relevant applications.

Thermodynamic study of monoclinic pyrrhotite in equilibrium with pyrite in the Ag-Fe-S system by solid-state electrochemical cell technique

An equilibrium mixture of monoclinic pyrrhotite and pyrite was synthesized in the eutectic AlCl3- KCl melt at 525 K. The reaction 7FeS2(cr) + 12Ag(cr) = 8Fe0.875S(cr) + 6Ag2S(cr) was studied by an electromotive force technique in an all-solid-state electrochemical cell with an Ag+-conductive solid electrolyte in Ar at atmospheric pressure: (-) Pt | Ag | AgI | Ag2S, Fe0.875S, FeS2 | Pt (+). In the 490-565 K temperature range a linear electromotive force vs. temperature trend was obtained from which the temperature dependence of the sulfur fugacity was determined for the monoclinic pyrrhotitepyrite equilibrium: logfS2(mpo+py) = 14.079 - 14406⋅T-1, (500 < T/K < 565). In addition, standard thermodynamic functions were calculated for monoclinic pyrrhotite Fe0.875S at 298 K and atmospheric pressure: ΔGf(mpo, 298.15 K) = -(136 200 ± 3000) J/mol, S°(mpo, 298.15 K) = (66.7 ± 1.3) J/(mol-K), ΔHf(mpo, 298.15 K) = -(157 400 ± 3000) J/mol. Gaseous sulfur, S2-ideal gas at 1 bar (105 Pa) pressure- was taken as a standard state for sulfur.

Thermodynamic stability and impedance measurements of perovskite LuRhO3(s) in the Lu–Rh–O system

The Gibbs energy of formation of LuRhO3(s) has been determined using a solid-state electrochemical technique employing an oxide ion conducting electrolyte.

Gibbs free energy of formation of rhodium sulfides

Using a solid-state electrochemical technique, thermodynamic properties of three sulfide phases (RhS0.882, Rh3S4, Rh2S3) in the binary system (Rh+S) are measured as a function of temperature over the range from (925 to 1275)K. Single crystal CaF2 is used as the electrolyte. The auxiliary electrode consisting of (CaS+CaF2) is designed in such a way that the sulfur chemical potential converts into an equivalent fluorine potential at each electrode. The sulfur potentials at the measuring electrodes are established by the mixtures of (Rh+RhS0.882), (RhS0.882+Rh3S4) and (Rh3S4+Rh2S3) respectively. A gas mixture (H2+H2S+Ar) of known composition fixes the sulfur potential at the reference electrode. A novel cell design with physical separation of rhodium sulfides in the measuring electrode from CaS in the auxiliary electrode is used to prevent interaction between the two sulfide phases. They equilibrate only via the gas phase in a hermetically sealed reference enclosure. Standard Gibbs energy changes for the following reactions are calculated from the electromotive force of three cells:2.2667Rh (s)+S2 (g)→2.2667RhS0.882 (s), ΔrGo±2330/(J·mol-1)=-288690+146.18(T/K),4.44RhS0.882 (s)+S2 (g)→1.48Rh3S4 (s),ΔrGo±2245/(J·mol-1)=-245596+164.31(T/K),4Rh3S4 (s)+S2 (g)→6Rh2S3 (s),ΔrGo±2490/(J·mol-1)=-230957+160.03(T/K).Standard entropy and enthalpy of formation of rhodium sulfides from elements in their normal standard states at T=298.15K are evaluated.

System Er–Ru–O: High temperature study of the heavy rare earth pyrochlore Er2Ru2O7(s) by electrochemical cell and differential scanning calorimeter

Abstract The Gibbs free energy of formation of Er 2 Ru 2 O 7 (s) has been determined using solid-state electrochemical technique employing oxide ion conducting electrolyte. The reversible electromotive force (e.m.f.) of the following solid-state electrochemical cell has been measured: (−)Pt/{Er 2 O 3 (s) + Er 2 Ru 2 O 7 (s) + Ru(s)}//CSZ//O 2 (p(O 2 ) = 21.21 kPa)/Pt(+). The Gibbs free energy of formation of Er 2 Ru 2 O 7 (s) from elements in their standard state, calculated by the least squares regression analysis of the data obtained in the present study, can be given by: {Δ f G°(Er 2 Ru 2 O 7 ,s) / (kJ∙mol −1 ) ± 2.2} = − 2517.3 + 0.6099 ∙ (T/K); (934.6 ≤ T/K ≤ 1236.3). Standard molar heat capacity C° p,m (T) of Er 2 Ru 2 O 7 (s) was measured using a heat flux type differential scanning calorimeter (DSC) in two different temperature ranges, from 129 K to 296 K and 307 K to 845 K. The heat capacity in the higher temperature range was fitted into a polynomial expression and can be represented by: C° p,m (Er 2 Ru 2 O 7 ,s,T)(J∙K −1 ∙mol −1 ) = 293.88 + 2.397 10 −2 T(K) − 54.74717 10 5 /T 2 (K); (307 ≤ T(K) ≤ 845). The heat capacity of Er 2 Ru 2 O 7 (s), was used along with the data obtained from the oxide electrochemical cell to calculate the standard enthalpy and entropy of formation of the compound at 298.15 K.

Oxygen Transport Parameters in Nafion® 117 under Controlled Relative Humidity

Solid state electrochemical techniques have provided insight into the effect of relative humidity on oxygen mass transport properties in Nafion® 117. Specifically, subsequent potential step coulometric measurements taken over a period of time have shown that the act of measurement affects the catalyst-membrane interface. It is postulated that the formation of product water at the interface leads to interactions with the Nafion® 117 surface and results in local domain changes. This effect has been shown to be reversible provided there is adequate rest time between measurements to allow for water diffusion from the interface.