Voltammetry Of Immobilized Microparticles Research Articles

Modeling solid-state reaction processes: application for the archaeometric study of potteries from Venus Fisica Temple in Pompeii (Italy)

AbstractThis research employs the voltammetry of immobilized microparticles (VIMP) methodology to analyze a collection of ceramic samples from the temple of Venus Fisica in the archaeological site of Pompeii. The primary objective is to discern their origins and manufacturing processes by the solid-state analysis of the electroactive properties of iron minerals, particularly hematite, extensively investigated for its electrochemical and catalytic characteristics. In our study, we propose a model to elucidate the electrochemical processes involved, building upon prior logistic and nucleation formulations. In this model, we consider the possibility of two superimposed pathways. This approach provides a nuanced understanding of composition changes and mineral crystallinity, factors that can induce significant variations in the voltammetric signal. Consequently, it becomes an effective means to discriminate between different provenances and manufacturing techniques of different potteries. The outcomes of this research contribute valuable insights into the intricate realm of ancient ceramic materials, casting light on their origins and production processes within the historical context of Pompeii.

Better tolerance to Huanglongbing is conferred by tetraploid Swingle citrumelo rootstock and is influenced by the ploidy of the scion.

Huanglongbing (HLB) is a disease that is responsible for the death of millions of trees worldwide. The bacterial causal agent belongs to Candidatus Liberibacter spp., which is transmitted by psyllids. The bacterium lead most of the time to a reaction of the tree associated with callose synthesis at the phloem sieve plate. Thus, the obstruction of pores providing connections between adjacent sieve elements will limit the symplastic transport of the sugars and starches synthesized through photosynthesis. In the present article, we investigated the impact of the use of tetraploid Swingle citrumelo (Citrus paradisi Macfrad × Poncirus trifoliata [L.] Raf) rootstock on HLB tolerance, compared to its respective diploid. HLB-infected diploid and tetraploid rootstocks were investigated when grafted with Mexican and Persian limes. Secondary roots were anatomically studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to observe callose deposition at the phloem sieve plate and to evaluate the impact of the bacterium's presence at the cellular level. Voltammetry of immobilized microparticles (VIMP) in roots was applied to determine the oxidative stress status of root samples. In the field, Mexican and Persian lime leaves of trees grafted onto tetraploid rootstock presented less symptoms of HLB. Anatomical analysis showed much stronger secondary root degradation in diploid rootstock, compared to tetraploid rootstock. Analysis of the root sieve plate in control root samples showed that pores were approximately 1.8-fold larger in tetraploid Swingle citrumelo than in its respective diploid. SEM analyses of root samples did not reveal any callose deposition into pores of diploid and tetraploid genotypes. VIMP showed limited oxidative stress in tetraploid samples, compared to diploid ones. These results were even strongly enhanced when rootstocks were grafted with Persian limes, compared to Mexican limes, which was corroborated by stronger polyphenol contents. TEM analysis showed that the bacteria was present in both ploidy root samples with no major impacts detected on cell walls or cell structures. These results reveal that tetraploid Swingle citrumelo rootstock confers better tolerance to HLB than diploid. Additionally, an even stronger tolerance is achieved when the triploid Persian lime scion is associated.

Valencian red imprimaturs since Francisco Ribalta (1565–1628)

• Imprimaturs used in 17th century by F. Ribalta and other valencian painters. • Possible use of red lake as imprimatur in 17th century canvas on painting. • Possible use of mars red as imprimatur in 17th century canvas on painting. • FESEM-EDX and miroRaman spectroscopy study of red imprimaturs. The aim of this study was to confirm the use of an admixture of natural earth and a second unusual Al-rich red pigment in the imprimaturs of paintings that date back to 1600–1660, painted by some of the most outstanding Valencian Baroque painters. For this purpose, microsamples excised from six paintings were prepared as cross-sections to be analysed by optical microscopy (OM) and field emission scanning electron microscopy-X-ray microanalysis (FESEM-EDX) combined with Fourier Transform Infrared (FTIR) spectroscopy, microRaman spectroscopy and voltammetry of immobilized microparticles (VIMP). Two possible red pigments, red lake or synthetic Mars red could be used by these painters in red imprimaturs mixed with natural earth pigments. This particular technique, identified for the first time in seventeenth-century Valencian paintings of known authorship, is a novel finding than can help in authentication studies of unknown Baroque paintings.

Use of carbon black based electrode as sensor for solid-state electrochemical studies and voltammetric determination of solid residues of lead

For the first time carbon black based electrode modified with paraffin was applied as a sensor on voltammetry of immobilized microparticles (VIMP) approach for determination of lead solid residues in hair dye samples. The solid microparticles of Pb(II) (Pb(CH3COO)2(s)) immobilized into the carbon paste sensor containing carbon black and paraffin were firstly reduced at initial potentials and further reoxidized at around −0.60 V during anodic scan. Electroanalytical parameters as well as supporting electrolyte composition, and pH were also evaluated. An analytical curve in 0.2 mol L−1 phosphate buffer solution (pH 5.0) from 0.04 to 3.2 μg (R2 = 0.999) with detection and quantification limits of 4 and 13 ng, respectively, were achieved. The method was applied to quantify lead solid residues in hair dye samples without previous mineralization or complex sample pre-treatment. Besides adequate repeatability, stability and selectivity of the developed sensor based on VIMP features, the method using carbon black based sensor was considered advantageous comparing to the results recorded by a spectrometric method (relative error lower than 8%) from several analytical viewpoints.

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.

Cutoff points and viewpoints of archaeometric investigation of archeological metals

This audit means to gather the new writing about the archaeometric investigation on antiquated metals zeroing in on the electrochemical methods: the electrochemical impedance spectroscopy (EIS) and the voltammetry of immobilized microparticles (VIMP) technique. An extraordinary look will be given to the investigation of bronze coins, extremely normal finds in the archeological challenges. It will be examined the significance of the portrayal examination and the archaeometric exploration to address archeological inquiries. In this respect, the examinations about the possibilities of EIS and VIMP for dating these items will be analyzed , featuring the best in class in the utilization of electrochemical strategies in the archaeometric field.

Ready-to-use 3D-printed electrochemical cell for in situ voltammetry of immobilized microparticles and Raman spectroscopy

We report in this communication a ready-to-use fused deposition modeling (FDM) based 3D-printed spectroelectrochemical cell to perform for the first time voltammetry of immobilized microparticles (VIMP) and Raman spectroscopy in situ using acrylonitrile butadiene styrene (ABS) as the filament material for printing. The 3D-printed cell was applied to evaluate solid state electrochemical behavior of tadalafil as a proof-of-concept. Several advantages were achieved in the use of the developed device, such as less manipulation of the working electrode, monitoring the same region of the solid microparticles before and after electrochemical measurements, better control of the laser incidence, low-cost and low-time production. Furthermore, the device was printed in a single-step, without handling to assembly and it has an estimated material cost of approximately 2 $. The use of 3D-printing technology was significantly important to integrate Raman spectroscopic method with VIMP measurements and to support mechanism elucidation and characterization of the compounds with less manipulation of the working electrode, avoiding loss of solid products formed from electrochemical reactions.

Multiple-scan voltammetry of immobilized particles of ancient copper/bronze coins

The application of a multiple-scan strategy to study the structure of the corrosion patina of copper/bronze ancient objects using the voltammetry of immobilized microparticles (VIMP) is described. Upon nanosample attachment to graphite electrodes in contact with aqueous acetate buffer, voltammetric signatures characterizing cuprite with variable degree of crystallinity are recorded by means of successive cathodic scans reflecting the composition of the corrosion patina. The reported methodology, complemented with ion beam-field emission scanning electron microscopy (FIB-FESEM) and high-resolution field emission scanning electron microscopy (HRFESM-EDX), is applied to a set of coins fabricated between 1709 and 1962 revealing different corrosion patterns.

Electrochemical behavior of 5-type phosphodiesterase inhibitory drugs in solid state by voltammetry of immobilized microparticles

Evaluation of electrochemical behavior of 5-type phosphodiesterase inhibitory drugs is of major concern since they have been added illegally as adulterants in dietary supplements. Then, for the first time, the solid-sate electrochemistry of sildenafil and tadalafil is described using voltammetry of immobilized microparticles (VIMP). An electrochemical cell was designed and printed in a fused deposition modeling (FDM)-based 3D printer for VIMP measurements. The 3D-printed cell designed with a distance of 5 mm between the working and reference electrode presented better voltammetric response and decrease in the uncompensated resistance of the electrochemical system. Cyclic and square wave voltammograms of the individual compounds were recorded in a paraffin-impregnated graphite electrode in contact with 0.01 mol L−1 H2SO4. The electrochemical oxidation/reduction products were characterized by Raman spectroscopy and scanning electron microscopy (SEM). Different voltammetric responses were detected for the solid compounds depending on the solubility of the parent compound and their products of oxidation/reduction. Moreover, significant crystal re-structuring was also observed after voltammetric scan of the solid compounds. Under optimized conditions, sildenafil and tadalafil could be electrochemical identified and distinguished in dietary supplements.

Limits and perspectives of archaeometric analysis of archaeological metals: A focus on the electrochemistry for studying ancient bronze coins

This review aims to collect the recent literature about the archaeometric analysis on ancient metals focusing on the electrochemical techniques: the electrochemical impedance spectroscopy (EIS) and the voltammetry of immobilized microparticles (VIMP) method. A special look will be given to the analysis of bronze coins, very common finds in the archaeological contests. It will be discussed the importance of the characterization analysis and the archaeometric research to solve archaeological questions. In this regard, the studies about the potentialities of EIS and VIMP for dating these objects will be examined , highlighting the state of the art in the application of electrochemical techniques in the archaeometric field.

Discrimination and Provenances of Phoenician Red Slip Ware Using both the Solid State Electrochemistry and Petrographic Analyses

AbstractSolid state electrochemistry based on the voltammetry of immobilized microparticles (VIMP) methodology is applied to a series of 80 Phoenician Red Slip samples from the archaeological sites of Motya (Sicily, Italy), Mogador (Morocco), Ramat‐Rahel (Israel), Sulky (Sardinia, Italy), Tas Silg (Malta), Pantelleria (Italy), and Cádiz (Spain), dated from the 8th to the 6th century BC. Upon attachment of sub‐microsamples to graphite electrodes in contact with aqueous H2SO4 electrolyte, voltammetric features due to the reduction of Fe(III) minerals and the oxidation of Fe(II) ones, complemented with electrocatalytic effects on oxygen reduction and oxygen evolution reactions, provide characteristic electrochemical fingerprints for pottery samples. A consistent sample grouping discriminating between different potteries from different archaelogical sites, is obtained, all results being consistent with morphological, compositional and mineralogical data. Petrographic analysis supports the grouping, defining the manufacture and firing procedure for the different archaeological context.

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.

New insights on medieval Provisini silver coins by a combination of non-destructive and micro-invasive techniques

The aim of this research was to characterize ten Provisini, one of the most common silver coins in the Middle Age, dating back to the 13th century A.D. These coins are composed by Ag-Cu alloy and were coined in the Roman mint. A non-destructive, micro-destructive and multi-analytical approach was used, aiming to preserve the surfaces of the coins. The results of XRD and micro-Raman spectroscopy allow defining the alloy composition and the mineralogical nature of the alteration products (e.g. cuprite, tenorite, chlorargyrite, stromeyerite). X-ray maps provided information on major elements distribution on the surface. Finally, Electrochemical Impedance Spectroscopy (EIS) and Voltammetry of Immobilized Micro-Particles (VIMP) permitted to reconstruct the possible scheme of the multi-layering of the patina on the coins. Then, the conservation status was monitored.

Electrochemical discrimination of manufacturing types of pottery from Magna Mater Temple and Fora of Nerva and Caesar (Rome, Italy)

The voltammetry of immobilized microparticles (VIMP) methodology is applied to a series of pottery samples from the Roman sites of Nerva's Forum (second half of 9th-early 11th A.D), Caesar's Forum (second half of 9th-early 11th A.D) and Magna Mater Temple (III century). The VIMP sampling applied to voltammetric and electrochemical impedance spectroscopy (EIS) measurements was applied by the first time to acquire archaeometric information on archaeological pottery. VIMP measurements using pressed sample pellets on gold electrodes in contact with air-saturated 0.10 M H2SO4 have permitted to detect voltammetric signals for the reduction/oxidation of Fe and Mn minerals as well as catalytic effects the mineral components on gold oxidation and oxygen reduction reaction. A consistent sample grouping was obtained using independent EIS measurements performed on microparticulate deposits of pottery samples on graphite electrodes in the same electrolyte.

Polythiophenes as markers of asphalt and archaeological tar pitch aging. Characterization using solid-state electrochemistry

The voltammetry of immobilized microparticles (VIMP) was used to characterize organosulfur components from ovens found at the Spanish archaeological sites of Cueva de Nerja (ca. 35,000cal BC), la Illeta dels Banyets (4th century BCE) and Gestalgar (12th–13th CE), and asphalt probes subjected to PAV and SUNTEST aging protocols. The voltammetric responses of the archaeological samples and the asphalt probes after photodegradation were quite similar, indicating the presence of polythiophene components which could act as age/degradation markers.

A combination of voltammetry of immobilized microparticles and carbon black-based crosslinked chitosan films deposited on glassy carbon electrode for the quantification of hydroquinone in dermatologic cream samples

New progress in the application of voltammetry of immobilized microparticles (VIM) technique in electroanalytical chemistry is reported in this work through the determination of hydroquinone in dermatologic cream samples. The designed electrode was based on a glassy carbon electrode modified with a crosslinked chitosan film containing immobilized carbon black nanoparticles and hydroquinone standards or sample. The electrochemical features of immobilized hydroquinone were explored, which a fast electron transfer kinetic was verified from the perfect reversible redox behavior of this molecule. All the experimental conditions were optimized, including supporting electrolyte condition (composition, pH, and ionic strength) and technical parameters of differential pulse voltammetry (DPV). Under the optimized experimental conditions, the analytical curve was linear by a wide concentration range from 2.7 to 43 ng, with detection and quantification limits of 0.045 and 0.15 ng, respectively. Two commercial dermatologic cream samples were successfully immobilized and analyzed using the proposed VIM procedure, and the results were similar to those recorded by a spectrophotometric comparative procedure. Our set of results represents a unique and exciting advance in the scenario of electroanalytical chemistry for future applications.

Voltametria de micropartículas imobilizadas: fundamentos e aplicações analíticas

The theoretical aspects of Voltammetry of Immobilized Microparticles (VIM) were discussed. The immobilization of microparticles on electrode surface, the electrode cleaning processes and the electrode materials were analyzed. The three-phase electrode model and the possible reactions between the immobilized particle and the electrolytic solution were discussed. In addition, this work discusses some selected applications of VIM published in the last years.

V(V) species in supported catalysts: Analysis and performance in oxidative dehydrogenation of ethane

Voltammetry of immobilized microparticles (VMP), diffuse reflectance UV–vis spectroscopy (DRS), X-ray powder diffraction (XRD), and Raman spectroscopy were used to identify V(V) oxidic species in vanadia catalysts supported on titania, alumina, mesoporous silicas, and composites of Al 2O 3 and TiO 2 with montmorillonite (MMT). V 2O 5 was detected by VMP irrespective of its crystallinity at concentrations close to the detection limit of crystalline V 2O 5 by XRD. The interpretation of DRS was re-evaluated after VMP analyses, because detection of lower concentrations of V 2O 5 by DRS is complicated by partial overlap of their absorption bands with rather intense absorption bands of major oligomeric vanadate species, while sensitivity of VMP to V 2O 5 is much better than to less condensed vanadates. VMP selectively identified polyvanadates prevailing on TiO 2 supports and oligomeric vanadate species prevailing on alumina at medium V-loadings. XRD-nanocrystalline V 2O 5 was found as major species on impregnated mesoporous silicas with V loading above 4 wt.%. Al- and Ti-chemically modified MMTs disperse V(V) oxide species preferentially either on the Al 2O 3 or TiO 2 components, or on the aluminosilicate components; these cases are easily distinguished by VMP. VMP, especially if combined with spectral and XRD analyses, can produce detailed information about V(V) oxidic forms at V-loading close to or slightly above the critical monomer monolayer concentration, where 2-D and 3-D condensation of [VO 4] units is initiated. These forms play an important role in functionality of heterogeneous catalysts in oxidative dehydrogenation of ethane.

Electrochemical characterisation of dental alloys: its possibilities and limitations

Dental alloys are metallic biomaterials which have a broad variation of composition compared to technical alloys. It is therefore in the interest of patients and technicians to conduct a good assessment of the electrochemical behaviour of dental alloys in order to collect information about their corrosion resistance. The purpose of this work was to demonstrate possibilities and limitations of two electrochemical techniques: the voltammetry of immobilised microparticles (ViMP) onto lead, and cyclic voltammetry measurements with the help of the mini-cell system (MCS). Based on fingerprints obtained from ViMP it was possible to analyse and differentiate the dental alloys. The results obtained by MCS were comparable with ViMP, but give a better understanding of the corrosion behaviour of the materials.

Fast and Simple Electroanalytical Identification of Iron Oxides in Geological Samples Without Sample Pretreatment

Hematite, goethite and siderite were found in geological samples using a simple, fast and low cost electroanalytical technique called voltammetry of immobilized microparticles (VMP). A carbon paste electrode was carefully rubbed onto the studied samples (an iron ore and ferrous oolites) to attach some microparticles to the surface of the electrode, and subsequently a potential scan was performed in two aqueous media to obtain the voltammogram which might be considered as the fingerprint of the sample deposited on the electrode. Each peak was related to an electrode process on the electrode whose peak potential indicates the type of iron compound. All the results were confirmed by commonly used analytical techniques to detect the presence of the different phases. All of this makes VMP an analytical tool very useful to save time and reduce analysis costs for geologist.