David Giménez-Romero

EQCM and EIS studies of Znaq2++2e−⇄Zn0 electrochemical reaction in moderated acid medium

The zinc electrodissolution and electrodeposition have been studied by means of electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy. Relevant information on the mechanism of these electrochemical processes is provided by the analysis of experimental data. The zinc electrodeposition takes place with an important participation of hydrogen ions while the zinc electrodissolution occurs, in these experimental conditions, by a mechanism in two steps. Besides, it is proved that the presence of molecular oxygen in the solution contributes to the formation of a passive layer on the metallic zinc deposit.

Dual-Polarization Interferometry: A Novel Technique To Light up the Nanomolecular World

Nanomolecular World Jorge Escorihuela,† Miguel Ángel Gonzaĺez-Martínez,† Jose ́ Luis Loṕez-Paz,† Rosa Puchades,† Ángel Maquieira,† and David Gimenez-Romero*,‡ †Department of Chemistry, Institute of Molecular Recognition and Technological Development, Universitat Politec̀nica de Valeǹcia, Camino de Vera s/n, 46022 Valeǹcia, Spain ‡Physical Chemistry Department, Faculty of Chemistry, Universitat de Valeǹcia, Avenida Dr. Moliner 50, 46100 Burjassot, Valeǹcia, Spain

Kinetics of zinc anodic dissolution from the EIS characteristic points

A possible faradaic impedance function for the complex mechanism of metals electrodissolution across two consecutive electrotransferences has been developed in this work. The analysis of this function provides some characteristics points from which it is possible to calculate kinetic parameters of these processes. The dependence of these parameters on the potential has been studied in the case of Zn. These ones have been interpreted in terms of changes in the controlling stages of the overall rate of reaction.

Electronic Perspective on the Electrochemistry of Prussian Blue Films

The derivative of the voltabsommetric scans, together with previous nano-electrogravimetric and X-ray diffraction results, allow different electrochemical processes to be distinguished during the Prussian blue (PB) voltammetric scan. Potassium, proton, and hydrated proton counterions involved in PB electrochemistry are related here to the electrochemical reactions of specific Fe sites. Potassium counterions show two different sites for their insertion: one located in the crystalline framework and another in ferrocyanide vacancies. From the monitoring of electroactive Fe sites, the covalent-exchange model is suggested as one of the first approaches to explain the origin of the PB magnetic ordering observed at room temperature during voltammetric scanning.

Resonant x-ray diffraction as a tool to calculate mixed valence ratios: Application to Prussian Blue materials

An approach is proposed here to calculate mixed valence ratios in molecular compounds. Synchrotron x-ray powder diffraction experiments were conducted to determine the Fe+3∕Fe+2 ratio in Prussian Blue compounds, which were elected as an example of the use of this approach. As a result, a resonant x-ray diffraction measurement provided direct evidence that the vacant [Fe(CN)6] group was randomly absent from ∼31% of the structure, which was indicated by structural differences caused by variations in the anomalous dispersion term. These findings are very important for a deeper understanding of the changes occurring in properties during in situ compositional variations.An approach is proposed here to calculate mixed valence ratios in molecular compounds. Synchrotron x-ray powder diffraction experiments were conducted to determine the Fe+3∕Fe+2 ratio in Prussian Blue compounds, which were elected as an example of the use of this approach. As a result, a resonant x-ray diffraction measurement provided direct evidence that the vacant [Fe(CN)6] group was randomly absent from ∼31% of the structure, which was indicated by structural differences caused by variations in the anomalous dispersion term. These findings are very important for a deeper understanding of the changes occurring in properties during in situ compositional variations.

Label-free piezoelectric biosensor for prognosis and diagnosis of Systemic Lupus Erythematosus

An autoantigen piezoelectric sensor to quantify specific circulating autoantibodies in human serum is developed. The sensor consisted on a quartz crystal microbalance with dissipation monitoring (QCM-D) where TRIM21 and TROVE2 autoantigens were covalently immobilized, allowing the selective determination of autoantibodies for diagnosis and prognosis of Systemic Lupus Erythematosus (SLE). The sensitivity of the biosensor, measured as IC50 value, was 1.51U/mL and 0.32U/mL, for anti-TRIM21 and anti-TROVE2 circulating autoantibodies, respectively. The sensor is also able to establish a structural interaction fingerprint pattern or profile of circulating autoantibodies, what allows scoring accurately SLE patients. Furthermore, a statistical association of global disease activity with TRIM21-TROVE2 interaction was found (n=130 lupic patient samples, p-value=0.0413). The performances of the biosensor were compared with standard ELISA and multiplex DVD-array high-throughput screening assays, corroborating the viability of piezoelectric biosensor as a cost-effective in vitro assay for the early detection, monitoring or treatment of rare diseases.

Anodic Dissolution of Nickel across Two Consecutive Electron Transfers Calculation of the Ni(I) Intermediate Concentration

The analysis of the electrochemical quartz crystal microbalance and electrochemical impedance spectroscopy results are consistent with a nickel electrodissolution process limited by the passage of Ni(I) to Ni(II), when chloride ions are present in the acid sulfate medium, or by the passage of Ni(II) to Ni 2+ in solution, in absence of chloride. This interpretation allows an explanation of the potential evolution of Fdm/dQ values in both experimental conditions by assuming the formation of a new phase on the electrode surface with a gel-like structure placed between the metal and the solution. Ni(I) surface concentration is calculated from the instantaneous mass/charge Fdm/dQ values.

Insights on the Mechanism of Insoluble-to-Soluble Prussian Blue Transformation

The electrochemical transformation of the soluble form of Prussian blue (PB) material from the insoluble form was monitored using electrochemical, gravimetric, acoustic, and spectroscopic techniques simultaneously. The described combination of in situ techniques represents an innovative tool for measurement in electrochemistry, which provides complementary information on the electrochemical systems. The insoluble-to-soluble PB transformation process takes place during the successive voltammetric cycles between the mixed valence form (PB) and the fully reduced form [Everitts salt (ES)]. One of the processes that takes place is the exit of free Fe(CN) 4- 6 ions occluded in the vacancies of the insoluble PB crystalline framework during the fresh PB electrodeposit process. In potassium salt solutions, the exit of each ferrocyanide ion is compensated by the entrance of two potassium ions and six hydroxyl anions. This species exchange increases the manifestation of viscoelastic phenomena of the rigid skeleton from the insoluble PB form to the soluble one, which could facilitate the appearance of an internal magnetic field at room temperature during the soluble PB ⇄ ES voltammetric cycle.

INSEL: an in silico method for optimizing and exploring biorecognition assays

A practical in silico method for optimizing and exploring biointeraction-based events is developed.

Elucidation of Carbohydrate Molecular Interaction Mechanism of Recombinant and Native ArtinM

The quartz crystal microbalance (QCM) technique has been applied for monitoring the biorecognition of ArtinM lectins at low horseradish peroxidase glycoprotein (HRP) concentrations, using a simple kinetic model based on Langmuir isotherm in previous work.18 The latter approach was consistent with the data at dilute conditions but it fails to explain the small differences existing in the jArtinM and rArtinM due to ligand binding concentration limit. Here we extend this analysis to differentiate sugar-binding event of recombinant (rArtinM) and native (jArtinM) ArtinM lectins beyond dilute conditions. Equivalently, functionalized quartz crystal microbalance with dissipation monitoring (QCM-D) was used as real-time label-free technique but structural-dependent kinetic features of the interaction were detailed by using combined analysis of mass and dissipation factor variation. The stated kinetic model not only was able to predict the diluted conditions but also allowed to differentiate ArtinM avidities. For instance, it was found that rArtinM avidity is higher than jArtinM avidity whereas their conformational flexibility is lower. Additionally, it was possible to monitor the hydration shell of the binding complex with ArtinM lectins under dynamic conditions. Such information is key in understanding and differentiating protein binding avidity, biological functionality, and kinetics.