Electrochemical nanostructured biosensors: carbon nanotubes versus conductive and semi-conductive nanoparticles

The aim of this work was to demonstrate that various types of nanostructures provide different gains in terms of sensitivity or detection limit albeit providing the same gain in terms of increased area. Commercial screen printed electrodes (SPEs) were functionalized with 100 µg of bismuth oxide nanoparticles (Bi₂O₃ NPs), 13.5 µg of gold nanoparticles (Au NPs), and 4.8 µg of multi-wall carbon nanotubes (MWCNTs) to sense hydrogen peroxide (H₂O₂). The amount of nanomaterials to deposit was calculated using specific surface area (SSA) in order to equalize the additional electroactive surface area. Cyclic voltammetry (CV) experiments revealed oxidation peaks of Bi₂O₃ NPs, Au NPs, and MWCNTs based electrodes at (790 ± 1) mV, (386 ± 1) mV, and (589 ± 1) mV, respectively, and sensitivities evaluated by chronoamperometry (CA) were (74 ± 12) µA mM^?1 cm^?2, (129 ± 15) ±A mM^?1 cm^?2, and (54 ± 2) ±A mM^?1 cm^?2, respectively. Electrodes functionalized with Au NPs showed better sensing performance and lower redox potential (oxidative peak position) compared with the other two types of nanostructured SPEs. Interestingly, the average size of the tested Au NPs was 4 nm, under the limit of 10 nm where the quantum effects are dominant. The limit of detection (LOD) was (11.1 ± 2.8) ±M, (8.0 ± 2.4) ±M, and (3.4 ± 0.1) ±M for Bi₂O₃ NPs, Au NPs, and for MWCNTs based electrodes, respectively.     

Hydrothermal Synthesis of Bismuth Sulfide (Bi2S3) Nanorods: Bismuth(III) Monosalicylate Precursor in the Presence of Thioglycolic Acid

Well-segregated bismuth sulfide (Bi₂S₃) nanorods with a high order of crystallinity have been successfully prepared from bismuth(III) monosalicylate [BiO(C₇H₅O₃)] by a simple hydrothermal reaction in H₂O at 180 °C. Bismuth(III) monosalicylate and thioglycolic acid act as the starting materials. The products were characterized by powder X-ray diffraction, Ultraviolet–Visible (UV–Vis) spectroscopy, transmission electron microscopy photoluminescence spectroscopy, and Fourier transform infrared spectra. The powder X-ray diffraction pattern shows the product belongs to the orthorhombic Bi₂S₃ phase. Their UV–Vis spectrum shows the absorbance at 328 nm, with its direct energy band gap of 2.6 eV. Bismuth salicylate, which is known to be a complex, may play a critical role as a precursor and a template for the growth of linear bismuth sulfide nanorods. Finally the influences of the reaction conditions are discussed and a possible mechanism for the formation of Bi₂S₃ nanorods is proposed.     

Electrochemical modification of Bi2S3 coatings in a nickel plating electrolyte

The electrochemical behavior of Bi₂S₃ coatings in Watts nickel plating electrolyte was investigated using the cyclic voltammetry, electrochemical quartz crystal microbalance, X-ray diffraction, and energy dispersive X-ray analysis methods. During the bismuth sulfide coating reduction in Watts background electrolyte in the potential region from −0.4 to −0.6 V, the Bi₂S₃ and Bi(III) oxygen compounds are reduced to metallic Bi, and the decrease in coating mass is related to the transfer of S²⁻ ions from the electrode surface. When the bismuth sulfide coating is reduced in Watts nickel plating electrolyte, the observed increase in coating mass in the potential region −0.1 to −0.4 V is conditioned by Ni²⁺ ions reduction before the bulk deposition of Ni, initiated by Bi₂S₃. In this potential region, the reduction of Bi(III) oxygen compounds can occur. After the treatment of as-deposited bismuth sulfide coating in nickel plating electrolyte at E = −0.3 V, the sheet resistance of the layer decreases from 10¹³ to 500–700 Ω cm. A metal-rich mixed sulfide Ni₃Bi₂S₂–parkerite is obtained when as-deposited bismuth sulfide coating is treated in Watts nickel plating electrolyte at a potential close to the equilibrium potential of the Ni/Ni²⁺ system and then annealed at temperatures higher than 120 °C.     

1,3,4-Trisubstituted-2-azetidinone Derivatives as Novel Receptors for Bismuth(III) Ion-Selective Electrodes: Application in Pharmaceutical and Glass Samples

Abstract

Polymeric membrane electrodes (PMEs) and coated graphite electrodes (CGEs) containing 1,3,4-trisubstituted-2-azetidinone derivatives as ion carriers are reported here for bismuth(III) ion selectivity. These electrodes exhibited Nernstian response for Bi³⁺ ions over a wide concentration range (5.0 × 10^?7 M to 1.0 × 10^?1 M for CGE) with a lower detection limit of 3.98 × 10^?7 M (for CGE) and wide pH range (1.3–5.0). Compared to polymeric membrane electrode, the coated graphite electrode has shown better selectivity for Bi³⁺ ions with respect to common metal ions. Proposed electrodes have been used for the estimation of Bi³⁺ ions in pharmaceutical and glass samples.     

A novel method for the anodic stripping voltammetry determination of Sb(III) using silver nanoparticle-modified screen-printed electrodes

Carbon screen-printed electrodes (CSPE) modified with silver nanoparticles present an interesting alternative in the determination of antimony using differential pulse anodic stripping voltammetry.Metallic silver nanoparticle deposits have been obtained by direct electrochemical deposition. Scanning electron microscopy measurements show that the electrochemically synthesized silver nanoparticles are deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analyzed to ensure that common interferents in the determination of antimony by ASV, such as bismuth, do not influence the electrochemical response of the latter element. The detection limit for Sb(III) obtained was 6.79 × 10⁻¹⁰ M. In terms of reproducibility, the precision of the above mentioned method in %RSD values was calculated at 3.50%. The method was applied to determine levels of antimony in seawater samples and pharmaceutical preparations.     

The synthesis of bismuth sulfide,antimony sulfide,and their solid solutions from tribenzylbismuth,tribenzylantimony, and elemental sulfur

The condensed phase reactions of tribenzylbismuth or tribenzylantimony and elemental sulfur under mild thermal conditions (≤275°C) produces the respective sesquisulfides in good yields and high purity. A mixture of the perbenzylated metals and elemental sulfur produces solid solutions of the general formula (Bi_xSb_1-x)₂S₃. It has been demonstrated that it is possible to achieve synthetic control over the size and microstructure of the as produced metal sulfide particles by simply changing reaction conditions. In combination with the condensed phase pyrolysis of tris(benzylthiolato)bismuth, five different microstructures for bismuth sulfide are accessible through compounds containing the benzyl ligand.     

Synthesis and properties of bismuth oxide nanoshell coated polyaniline nanoparticles for promising photovoltaic properties

A novel heterostructure made of polyaniline (PANI) nanoparticles coated by nanolayer of bismuth oxide Bi₂O₃ was synthesized. The structure was characterized by scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy. These characterizations showed that the bismuth oxide nanoshell was pure and crystalline, and has thickness in the range of 10 nm. The experiment on photoluminescence (PL) of Bi₂O₃ nanoshell coated polyaniline nanoparticle, at room temperature, shows an emission band peaked at around 385 nm. When compared with the PL spectrum of Bi₂O₃ nanoparticles, about 100 times PL enhancement was found in the PL spectrum of Bi₂O₃ nanoshell coated polyaniline nanoparticle. The current density versus voltage (J–V) measurements in dark and illumination showed that this heterojunction has 4 orders of magnitude rectification in the dark and 3 orders of magnitude rectification under illumination. The obtained power conversion efficiency of polyaniline nanoparticles coated by nanoshell of bismuth oxide (η = 7.453%) was much enhanced compared with polyaniline alone (η = 8.33 × 10^?4%) this indicates that the prepared heterostructure represents a promising photovoltaic solar cell. Copyright © 2009 John Wiley & Sons, Ltd.     

Study of electrooxidation of binary electrolytic deposit palladium–bismuth deposited on graphite electrode surface

The phase structure of palladium–bismuth binary electrolytic deposit was studied. The electrodeposition of deposit components on the surface of a graphite electrode (GE) was carried out in situ. On current–voltage curves, the peak of bismuth electrooxidation, the peak of palladium electrooxidation and an additional peak at 0.15 V vs. Ag/AgCl are observed. The peak current at 0.15 V depends both on the concentration of palladium(II) ions and on that of bismuth(III) ions. The thermodynamic theory of alloys in the approximation of the theory of regular solutions was used for calculations. The mixing heat of the binary alloy components and the equilibrium potential of bismuth in the bismuth–palladium alloy are calculated. The calculated equilibrium potential of bismuth in an alloy with palladium is 0.12 V vs. Ag/AgCl which corresponds to the Bi₂Pd intermetallic compound (IMC). Investigation of the surface of a GE with a palladium–bismuth deposit with use of scanning electron microscope showed that the electrolytic deposit contains bismuth, palladium and the Bi₂Pd IMC. Peak at the potential of plus 0.15 V vs. Ag/AgCl is due to selective bismuth electrooxidation from the Bi₂Pd IMC.     

Bismuth triple-decker phthalocyanine: synthesis and structure

Triclinic crystals of bismuth(III) triple-decker phthalocyanine, Bi₂Pc₃, Pc=C₃₂H₁₆N₈²⁻, were grown directly by the reaction of Bi₂Se₃ with 1,2-dicyanobenzene at 220°C. The Bi₂Pc₃ molecule is centrosymmetric with the bismuth atoms located closer to the peripheral phthalocyaninato(2−) rings than to the central ring. Each bismuth(III) ion is connected by four N-isoindole atoms to the peripheral and by four N-isoindole to the central Pc ring with average distances of 2.333 and 2.747 Å, respectively. This indicates a stronger connection of Bi(III) to the peripheral saucer-shaped macrocyclic rings than to the central rings. The neighbouring phthalocyaninato(2−) moieties in the Bi₂Pc₃ molecule are separated by a distance of 3.101(5) Å. The central Pc ring is rotated by 36.4° with respect to the peripheral ones. Differences in Bi–N bond lengths are a result of interaction of the bismuth ion with peripheral and central rings as well as the repulsion forces between two bismuth ions in the same Bi₂Pc₃ molecule, which are separated by a distance of 3.839(2) Å. The crystal packing is characterized by a distance of 3.56 Å between Pc rings of neighbouring Bi₂Pc₃ molecules.     

Electrochemical Detection of Nitrite Using an Asymmetrically Substituted Cobalt Phthalocyanine Conjugated to Metal Tungstate Nanoparticles

This paper explores the synthesis and characterisation of an asymmetrical Co phthalocyanine (CoPc), and its covalent linking to two tungsten nanoparticles: bismuth tungsten oxide (Bi₂WO₆) and nickel tungsten oxide (NiWO₄). The nanoparticles were also mixed with the CoPc. The CoPc, nanoparticles and their respective conjugates were used as electrocatalysts in the electrochemical detection of nitrite. The electrocatalysts studied in this work had sensitivities ranging from 3–133 μA/mM while the limits of detection (LoDs) ranged between 0.063 μM and 1.7 μM. Bi₂WO₆ and its conjugate exhibited better LoD than corresponding NiWO₄ and conjugate.     

Ag Doped Titanium Dioxide Nanocomposite‐modified Glassy Carbon Electrode as Electrochemical Interface for Catechol Sensing

The electrochemical sensing of catechol (CC) on a glassy carbon electrode modified with the ionothermal assisted synthesis of Ag doped TiO₂ a nanoparticle has been successfully demonstrated for the first time.Ag doped TiO₂ nanoparticles composite modified glassy carbon electrode exhibits higher electrocatalytic activity towards oxidation of catechol than glassy carbon electrode itself. The modified electrode also exhibits high selectivity towards this analyte in the presence of some of the metal ions and some of the biological compounds. Linear ranges and the limit of detections with the above electrode are 1–15 µM and 0.0249 µM respectively. The optimized protocol has been utilized for monitoring the catechol in some of the natural samples like apple juice and green tea and in industrial effluents.     

Substituted bismuth vanadates and chromates: New aspects

The work is devoted to the synthesis and attestation of a number of substituted vanadates and chromates of bismuth. For bismuth vanadates of the BIMEVOX family, the homogeneity regions of the Bi₄V_{2 – x}Cr _x O_{11 ± d} solid solutions have been refined, the features of the structure change of the compounds with increasing chromium content and changing temperature have been noted, and the powders and ceramics have been studied by electron microscopy. For the first time, as an impurity, an individually substituted bismuth chromate of the composition Substituted bismuth chromate of the Bi₁₃Cr_{5 – y}V _y O_{34.5 – d} (y = 0.95 ± 0.05) composition has been detected for the first time as an impurity and synthesized as an individual compound, which has been characterized by X-ray diffraction, electron microscopy, chemical analysis, and photoelectron spectroscopy data; its homogeneity range has been determined, and electroconductive characteristics have been studied.     

Effect of phase stability degradation of bismuth on sensor characteristics of nano-bismuth fixed electrode

Effect of phase stability degradation of bismuth on sensor characteristics of nano-bismuth fixed electrode has been investigated using square-wave anodic stripping voltammetry technique, scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectroscopy. From the analyses of square-wave anodic stripping voltammograms (SWASV) repetitively measured on the nano-bismuth fixed electrode, it was found that the oxidation peak currents dropped by 81%, 68% and 59% for zinc, cadmium and lead, respectively, after the 100th measurement (about 400 min of operation time). The sphere bismuth nanoparticles gradually changed to the agglomerates with petal shape as the operation time increased. From the analyses of SEM images and XRD patterns, it is confirmed that the oxidation of Bi into BiOCl/Bi₂O₂CO₃ and the agglomeration of bismuth nanoparticles caused by the phase change decrease a reproducibility of the stripping voltammetric response. Moreover, most of the bismuth becomes BiOCl at pH 3.0 and bismuth hydroxide, Bi(OH)₃ at pH 7.0, which results in a significant decrease in sensitivity of the nano-bismuth fixed electrode.     

Investigation of synthesis and microstructure of bismuth titanates with TiO<Subscript>2</Subscript> rich compositions

Preliminary examinations regarding formation of bismuth titanates in a part of Bi₂O₃—TiO₂ system rich with TiO₂ have been carried out. Bismuth titanates have been synthesized from mixtures of Bi₂O₃ and TiO₂ (anatase) by the conventional solid-state method at the temperatures ranged from 1273 to 1473 K. Differential thermal analysis (DTA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to study the formation of bismuth titanates. The following compounds have been achieved: Bi₄Ti₃O₁₂, Bi₂Ti₂O₇ and Bi₂Ti₄O₁₁. Existence of controversial bismuth titanate of formula Bi₂Ti₃O₉ in the Bi₂O₃—TiO₂ system has not been confirmed.     

Synthese und Kristallstrukturen der quaternären Chalkogenidchloride AgBi2S3Cl und AgBi2Se3Cl

Synthesis and Crystal Structures of the Quaternary Chalcogenide Chlorides AgBi₂S₃Cl and AgBi₂Se₃Cl Grey crystals of AgBi₂S₃Cl and AgBi₂Se₃Cl were synthesized from AgCl and Bi₂S₃ or Bi₂Se₃by cooling stoichiometric melts from 790 K to room temperature. X‐ray diffraction on powders and single‐crystals revealed that the compounds crystallize isostructural with space group type P 2₁/m. In the crystal structure of AgBi₂S₃Cl the bismuth(III) cations have a capped trigonal prismatic coordination of sulfide and chloride ions. The prisms constitute a three‐dimensional framework by sharing common edges and faces. Silver(I) cations, which have a distorted octahedral coordination of sulfide ions, fill linear channels. Parallels to the crystal structures of Cu₃Bi₂S₄Cl and Pr₂Br₅ can be seen.     

A Role of the Plating Regime in the Deposition of Bismuth Films onto a Carbon Paste Electrode. Microscopic Study

A microscopic study is presented based on observations of bismuth films deposited from various plating solutions and under different experimental conditions onto the carbon paste surface. Electrolytic plating of bismuth films was performed either as simulation of preconcentration in‐situ from a 0.2 M acetate buffer containing 5×10^?5 M Bi³⁺ (pH 4.25), or as external deposition from various plating solutions: 0.1 M acetate buffer with 5×10^?4 M Bi³⁺ (pH 4.50), 0.5 M HCl with either 0.001 M BiCl₃ or 0.005 M BiCl₃ , 0.5 M HCl+0.5 M KBr+0.005 M BiCl₃ , and 0.5 M HCl+0.5 M KI+0.005 M BiCl₃ (all pH≈0.5). Scanning electron microscopic images of the bismuth films showed a considerable variability in structure and compactness of the deposited layer in dependence on experimental conditions chosen such as the concentration of Bi(III) species, the total acidity of plating media, the stability of complexes of Bi(III) with halogenide anions or the deposition potential applied.     

Voltammetric behavior and determination of bismuth on sodium humate modified carbon paste electrode

The preconcentration and voltammetric behavior of Bi^III on a sodium humate modified carbon paste electrode was studied by means of cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). The proposed measurement involves an initial nonelectrolytic preconcentration step in which Bi^III is complexed by the surface modifier in a solution of 0.05 M KNO₃-0.0106 M HNO₃ (pH 2.0) and a subsequent electrochemical scan step in which the preconcentrated Bi^III was reduced and then oxidized promptly in supporting electrolyte of 0.5 M HNO₃. The resulting DPSV anodic current was proportional to the concentration of Bi^III ion over the range of 4.78 × 10⁻⁸–1.44 × 10⁻⁵ M. The detection limit was 4.78 × 10⁻⁸ M. The proposed method was used to determine bismuth in various samples. Various factors affecting the electrode behavior were also investigated at the same time.     

Effect of surface melting on the formation and growth of nanocrystals in the Bi2O3-Fe2O3 system

Formation of nanocrystals in the Bi₂O₃-Fe₂O₃ system prepared by the co-precipitation of bismuth and iron hydroxides has been studied. The temperature of onset of the BiFeO₃ and Bi₂Fe₄O₉ nanocrystals formation is correlated with the melting point of the non-autonomous phases. The optimal temperature of BiFeO₃ and Bi₂Fe₄O₉ nanoparticles synthesis is 460–520 and 500–550°C, respectively.     

Preparation and voltammetric characterisation of bismuth-modified mesoporous platinum microelectrodes. Application to the electrooxidation of formic acid

In this paper mesoporous platinum microeletrodes (Pt-ME) modified with submonolayers of adsorbed bismuth (Bi-PtME) were prepared and characterised by cyclic voltammetry (CV). The mesoporous platinum films were electrodeposited from hexachloroplatinic acid dissolved in the aqueous domain of the lyotropic liquid crystalline phase of Brij 78^®, to form metal films with hexagonal arrays of nanometer-sized channels. Bismuth deposition was performed by different procedures involving either the spontaneous adsorption of bismuth onto the Pt surface from Bi³⁺ solutions, or by under potential deposition (UPD) of bismuth from Bi³⁺ solutions, by cycling the potential over an useful range, or applying a constant potential for a given time. The latter procedures provided high bismuth coverage (θ_Bi), whereas only small amounts of bismuth could be adsorbed from the simple immersion of the Pt-ME at open circuit. The coverage by irreversibly adsorbed bismuth was checked in a 0.5 M H₂SO₄ solution free of Bi³⁺ ions and exploiting the charge involved in the hydrogen adsorption/desorption, which decreased in proportion to the amount of platinum sites covered by bismuth. The ability of the prepared Bi-PtME towards the oxidation of formic acid was also investigated. It was found that Bi-PtME with θ_Bi = 0.6 provided stationary voltammograms characterised by a low hysteresis between the anodic and cathodic scans. The onset of the waves resulted shifted by about 150 mV towards less positive potentials with respect to that of the corresponding Pt-ME. At 0.1 M HCOOH current densities of about 70 mA cm⁻² were achieved. These results were discussed in terms of high tolerance towards the intermediate poisons of the Bi-PtME investigated here. Bi-PtME with much lower real surface area and bismuth coverage displayed both lower catalytic activity and tolerance to poisons.     

Multifunctional material Bi4Ge3O12: thermodynamic properties

Thermodynamic characteristics of a single crystal of bismuth orthogermanate (Bi₄Ge₃O₁₂), which are necessary to improve device portfolio, have been studied. It has been shown that bismuth orthogermanate is thermodynamically stable against decomposition into binary oxides at 50 °C, which gives us grounds to consider this compound promising for various applications.