Characterization of thin InP anodic oxide layers: Correlation of morphological investigations with chemical and electrical properties

Depending on the applied electrochemical parameters, various oxide films can be grown onto InP in aqueous media. In this work, two oxide layers have been grown in borate buffer solution at pH = 9 by applying a low (0.2 mA cm⁻²) or a high (30 mA cm⁻²) current density, but a similar coulometric charge. Capacitance–voltage measurements performed before and after the anodic processes have been made to investigate the electrical properties of new interfaces, while X-ray photoelectron spectroscopy (XPS) analysis and atomic force microscopy (AFM) observations were used to access to the chemical and topographic aspects of the two oxidized surfaces. It is demonstrated that AFM observations coupled with electrochemical and XPS measurements is a good probe for the study of thin oxide on InP. A correlation between the anodization parameters and the resulting electrical and morphological aspects of the anodic layers is clearly evidenced.     

Crystallization of the anodic oxide on titanium in sulphuric acids solution at a very low potential

Anodic oxide films were formed on the deposited pure titanium in 0.1 M H₂SO₄ solution at 30 °C by using cyclic voltammetry (CV) anodization technique. Clear atomic images and step-terrace structure were observed on it by using STM, which gave a direct evidence for the local crystallinity of the anodic oxide films, even though the maximum anodization potential (E_max) was −50 mV, which was much lower than the lowest potential for crystallization in literatures. Moreover, the crystalline degree of the whole anodic oxide film was estimated from the refractive index (n), and the results showed that the crystalline degree increased with potentials. The analysis of XPS spectra revealed that high potentials were also beneficial for the formation of TiO₂, which was the primary substance for the formation of stable crystals in the oxide films.     

Stability of InP oxide versus solvated electrons in liquid ammonia

In alkaline aqueous medium (pH 9), potassium ferricyanide was used as an oxidizing agent on InP. This electroless process was successfully controlled by capacity measurements, AFM and XPS analyses. For the first time, the chemical stability of the oxide has been studied against the strongest reducing agent in liquid ammonia (?50 °C): the solvated electron. It was obtained in two ways; an electroless process which involved the addition of metallic potassium and by cathodic galvanostatic treatment on InP in neutral medium. As a first result, the electroless process required a strong rinsing step of the surface by pure liquid ammonia. As a second result, the galvanostatic process gave also promising results. A significant decrease of the amount of oxide was evidenced by capacity measurements, AFM and XPS analyses.     

Dealing with interference challenge in the electrochemical detection of As(III) —A complexometric masking approach

Copper ion has been reported to be a major interference in the electrochemical detection of arsenic (III) ion in water. Therefore the development of a simple approach to alleviate this interference challenge is important. We present the use of ammonia solution as a masking agent for Cu(II) interference in the square wave anodic stripping voltammetry of As(III) on a gold nanoparticle modified glassy carbon electrode (GCE). AuNPs were electrochemically deposited by cyclic voltammetry on a GCE from a potential range of − 400 mV to 1100 mV for 10 cycles. Square wave anodic stripping voltammetry (SWASV) was used to detect As(III) in water with and without Cu(II) based on the following optimised conditions: pH = 3, deposition potential = − 600 mV, and deposition time = 60 s. Ammonia solution was added to the analyte solution and the effect on mitigating copper interference was studied. The presence of ammonia complexed the Cu(II) ion thereby excluding Cu(II) from interfering with the As(III) signal.     

Spontaneous deposition of Sn on Au(1 1 1). An in situ STM study

The tin adlayer formed by spontaneous deposition on Au(1 1 1) was characterized by cyclic voltammetry and in situ scanning tunneling microscopy (STM) in sulphuric acid solution. Cyclic voltammetry measurements showed oxidation peaks in the potential range −0.60 ⩽ E/V vs SSE ⩽ 0, which can be ascribed to the dissolution of the Sn adsorbed layer. STM images of the Au(1 1 1)/Sn modified surface showed that tin nucleated both on step edges and on the flat terraces forming two-dimensional islands. The anodic polarization of this modified surface produced the gradual dissolution of the Sn adlayer which was evidenced by the formation of some holes and the reduction of the initial terraces to many small islands. STM images with atomic resolution obtained on these islands displayed an hexagonal expanded atomic structure. After the anodic stripping of this Sn adsorbed layer the images exhibited the typical Au(1 1 1) terraces with a (1 × 1) atomic structure. However, at more anodic potentials another dissolution process was observed producing noticeable changes on the surface morphology which could be ascribed to the dissolution of a Au–Sn surface alloy.     

Fast formation of thick and transparent titania nanotubular films from sputtered Ti

Ti films sputtered on transparent fluorine-doped tin oxide glass substrates were anodized in fluoride-containing organic electrolyte in the presence of H₂O. In this work, anodic TiO₂ nanotubes (ATNs) as long as 9.2 ± 0.3 μm were obtained with high growth rate of 0.64 ± 0.3 μm min^?1. We demonstrated the optimum anodization conditions for ATN growth on foreign substrates, were within the range of 0.3–0.5% (wt) NH₄F, with 3–5% (vol) H₂O at 60 V. XPS and ICP-MS were utilized to elucidate the increase of thickness and volume expansion obtained from the sputtered Ti film to their ATN forms. The ATN films exhibited excellent uniformity and adhesion to the substrates.     

Electrochemistry of acetylide anion and anodic formation of carbon films in a LiCl–KCl–CaCl2–CaC2 melt

The electrochemical deposition of carbon films on a nickel substrate was carried out through anodic oxidation of calcium acetylide dissolved in a LiCl–KCl–CaCl₂ melt at 823 K. Continuous and tenacious carbon films were prepared by a two-stage anodically potentiostatic deposition at a fast rate, and characterized by SEM, Raman spectroscopy, XRD and XPS. The results show the carbon films composed of micron-sized particles with graphitized and amorphous phases containing a mixture of sp³ and sp² carbon. The cyclic voltammetry behavior of acetylide anion on graphite and nickel electrodes indicated that C₂^2 − ions are oxidized more favorably on the nickel substrate due to the anodic depolarization from nickel carburization.     

Enhancing the bioactivity of zirconium with the coating of anodized ZrO2 nanotubular arrays prepared in phosphate containing electrolyte

Bioactive zirconium oxide nanotubular arrays on zirconium alloys are prepared electrochemically in fluoride and phosphate containing electrolyte. Geometric factors of the ZrO₂ nanotubular layers, particularly the pore diameter and thickness, are affected by the electrochemical conditions, including applied potential and anodization time. Under specific sets of conditions, highly ordered ZrO₂ nanotubular arrays are formed with diameters varying from 30 nm to 75 nm and lengths varying from 2 μm to 12 μm. XPS shows that the nanotubular layer contains a significant amount of phosphate species distributed almost homogeneously over the entire tubular length. The ZrO₂ nanotubular layer formed in fluoride and phosphate containing electrolyte highly enhances the formation of bioactive hydroxyapatite coating in simulated biological fluid (SBF).     

Electrografting of amino-TEMPO on graphene oxide and electrochemically reduced graphene oxide for electrocatalytic applications

4-Amino-2,2,6,6-tetramethyl-1-piperridine N-oxyl (4-amino-TEMPO), an electroactive nitroxide radical, was attached to the surface of graphene oxide (GO) and electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode by a simple, rapid and green electrografting method. The electroactive interfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The calculated surface coverage for 4-amino-TEMPO is up to 1.55 × 10^− 9 mol·cm^− 2. The modified electroactive interface exhibited excellent electrocatalytic activity towards the electro-oxidation of reduced glutathione (GSH) and hydrogen peroxide (H₂O₂).     

Enhanced electrochromics of nanoporous cobalt oxide thin film prepared by a facile chemical bath deposition

A highly porous cobalt oxide thin film was prepared on ITO glass by a facile chemical bath deposition (CBD) method. The as-prepared cobalt oxide film has an intercrossing net-like morphology. The electrochromic performance of cobalt oxide film was investigated in 0.1 M KOH by means of transmittance, cyclic voltammetry (CV) and chronoamperometry (CA) measurements. The cobalt oxide thin film exhibits a noticeable electrochromism with reversible color changes from pale yellow to dark grey and presents a transmittance variation with 36% in the visible range. The porous cobalt oxide thin film also shows good reaction kinetics with fast switching speed, and the coloration and bleaching time are 2.5 and 2 s, respectively.     

Investigation of electrochemical behavior of anisomycin on gold electrode followed by HPLC–MS/MS analysis

Anisomycin is an immunosuppressant in low doses (< 0.1 μM) with possible application in treatment of some autoimmune diseases and in inhibiting transplantation rejection. Anisomycin suppresses malignant tumor cell growth and affects memory. For the first time it was the subject of the electrochemical investigations by cyclic voltammetry and square wave voltammetry on gold electrode in 0.05 M NaHCO₃ using its electrochemical activity. The cyclic voltammetry experiments at different sweep rates show that electrochemical process is irreversible and diffusion controlled. Based on square wave voltammetry measurements, the calculated values of LOD and LOQ were 1 and 4 nM (in the absence of biological fluid), as well as 2 and 6 nM (in the presence of spiked urine) indicating the high sensitivity of the proposed electroanalytical method. High performance liquid chromatography–tandem mass spectrometry was a reference method for quantification of anisomycin and served for structural identification of its hydrolysis product (deacetylanisomycin).     

InP as new anode material for lithium ion batteries

InP thin film has been successfully fabricated by pulsed laser deposition (PLD) and was investigated for its electrochemistry with lithium for the first time. InP thin film presented a large reversible discharge capacity around 620 mAh g^?1. The reversibility of the crystalline structure and electrochemical reaction of InP with lithium were revealed by using ex situ XRD and XPS measurements. The high reversible capacity and stable cycle of InP thin film electrode with low overpotential made it one of the promise energy storage materials for future rechargeable lithium batteries.     

Anodic TiO2 nanotube layers: Why does self-organized growth occur—A mini review

The present review gives an overview of the highlights of more than 10 years of research on synthesis and applications of ordered oxide structures (nanotube layers, hexagonal pore arrangements) that are formed by self-organizing anodization of metals. In particular we address the questions after the critical factors that lead to the spectacular self-ordering during the growth of anodic oxides that finally yield morphologies such as highly ordered TiO₂ nanotube arrays and similar structures. Why are tubes and pores formed—what are the key parameters controlling these processes?     

The qualitative electrochemical determination of clarithromycin and spectroscopic detection of its structural changes at gold electrode

The aim of the present study was the qualitative determination of the pure clarithromycin using a gold electrode in neutral electrolyte by cyclic linear sweep voltammetry. It was shown that in the range of −1.2 V to 1.0 V vs. SCE in 0.05 M NaHCO₃, a gold electrode is successfully employed for the qualitative determination of clarithromycin by detection of the reproductive four anodic and one cathodic peaks. After the potentiostatic measurements at the potential values corresponded to current peaks, the bulk electrolyte was analyzed by FTIR spectroscopy to show the changes in molecular structure of clarithromycin. FTIR analysis of the bulk electrolyte after 4 h of holding the potential at −0.61 V vs. SCE (cathodic peak) showed the apparent changes in clarithromycin molecule structure: in the ester bond of the lactone and in ethers and acetal bonds.     

Electrochemical oxidation of primary amine in ionic liquid media: Formation of organic layer attached to electrode surface

Electrochemical oxidation of primary amine in ionic liquid media has been investigated. The ionic liquid chosen for this study was 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Two primary amine compounds are used for this study; 4-nitrobenzylamine and 2-aminoethylferrocenylmethylether. The oxidation of the amino compounds in ionic liquid conduces to the modification of the electrode surface. The modified electrodes were characterized by cyclic voltammetry and XPS analysis. Both techniques support the presence of an organic layer strongly attached onto the electrode surface. The surface concentration of the attached group obtained in this media was found to be around 1 to 3 × 10^?10 mol cm^?2. The use of ionic liquid as media for the grafting leads to decrease of the surface concentration of the grafted layer; and the formation of less dense layer compared with classical solvent such as acetonitrile.     

Electrodeposition of nanocrystalline aluminium from a chloroaluminate ionic liquid

In this letter we show that nanocrystalline aluminium can be electrodeposited in the Lewis acidic ionic liquid based on AlCl₃ (60 mol%) and 1-(2-methoxyethyl)-3-methylimidazolium chloride ([MoeMIm]Cl) (40 mol%). The study comprised cyclic voltammetry, potentiostatic polarization, and SEM and XRD measurements. The methoxy group in the side chain of the imidazolium cation significantly influences the electrodeposition pathway of Al in comparison to [EMIm]Cl/AlCl₃. Cyclic voltammetry shows a significant current loop attributed to nucleation. Shiny Al layers are obtained with an average crystallite size of about 40 nm.     

(Liquid + liquid), (solid + liquid), and (solid + liquid + liquid) equilibria of systems containing cyclic ether (tetrahydrofuran or 1,3-dioxolane), water,and a biological buffer MOPS

Two liquid phases were formed as the addition of a certain amount of biological buffer 3-(N-morpholino)propane sulfonic acid (MOPS) in the aqueous solutions of tetrahydrofuran (THF) or 1,3-dioxolane. To evaluate the feasibility of recovering the cyclic ethers from their aqueous solutions with the aid of MOPS, we determined experimentally the phase diagrams of the ternary systems of {cyclic ether (THF or 1,3-dioxolane) + water + MOPS} at T = 298.15 K under atmospheric pressure. In this study, the solubility data of MOPS in water and in the mixed solvents of water/cyclic ethers were obtained from the results of a series of density measurements, while the (liquid + liquid) and the (solid + liquid + liquid) phase boundaries were determined by visually inspection. Additionally, the tie-line results for (liquid + liquid) equilibrium (LLE) and for (solid + liquid + liquid) equilibrium (SLLE) were measured using an analytical method. The reliability of the experimental LLE tie-line results data was validated by using the Othmer–Tobias correlation. These LLE tie-line values were correlated well with the NRTL model. The phase diagrams obtained from this study reveal that MOPS is a feasible green auxiliary agent to recover the cyclic ethers from their aqueous solutions, especially for 1,3-dioxolane.     

Facile one-pot synthesis of fluorinated graphene oxide for electrochemical sensing of heavy metal ions

Doping and functionalization could significantly assist in the improvement of the electrochemical properties of graphene derivatives. Herein, we report a one-pot synthesis of fluorinated graphene oxide (FGO) from graphite. The surface morphology, functionalities and composition of the resulting FGO have been studied using various surface characterization techniques, revealing that layer-structured nanosheets with ~ 1.0 at.% F were formed. The carbon bound F exhibited semi-ionic bonding characteristic and significantly increased the capacitance of FGO compared to GO. Further, the FGO has been employed for the simultaneous detection of heavy metal ions Cd^2 +, Pb^2 +, Cu^2 + and Hg^2 + using square wave anodic stripping voltammetry; and a substantial improvement in the electrochemical sensing performance is achieved in comparison with GO.     

Anodic behavior and pore growth of n-InP in acidic liquid ammonia

In this paper, we report on the anodic behavior of n-InP (100) in acidic liquid ammonia at 223 K. Electrochemical, morphological and optical characterizations have been performed on InP after galvanostatic polarizations in different ranges. Prior to any dissolution processes, the formation of a stable anodic passivating thin film with a chemical composition close to “HNP–NH₂” (phosphinimidic amide) is observed. Depending on the current, two different phenomena occur: at low current density a thick amorphous film is formed, while tortuous current line oriented pores are grown when a high current is applied. For high coulometric charges, this last porous film can exhibit a multilayered structure. A decrease of the photoluminescence intensity without any peak shifts is observed whatever the applied current. This has been ascribed to the absorbent property of the layers.     

Synthesis and properties of 5,10,15,20-tetra(4-lauroylimidophenyl)porphyrin and its metal complexes

Transition metal complexes of 5,10,15,20-tetra(4-lauroylimidophenyl)porphyrin TLPPM [M = Mn(Cl), Fe(Cl), Co, Ni, Cu, Zn] have been synthesized and characterized by means of elemental analyses, UV–VIS spectra, infrared spectra, ¹H NMR spectra, molar conductance, differential scanning calorimetry (DSC), polarized optical microscopy (POM), cyclic voltammetry, luminescence spectra and surface photovoltage spectroscopies. The porphyrin ligand shows liquid crystalline behaviour, and it exhibits a high phase transition temperature 182 °C and a broad mesophase temperature span, 88 °C. The oxidation and reduction properties of the compounds were investigated by cyclic voltammetry. The photovoltaic properties and charge transfer process of the compounds were investigated by surface photovoltage spectroscopy (SPS) and electric field-induced surface photovoltage spectroscopic (EFISPS) techniques, which revealed that all the compounds are p-type semiconductors. Quantum yields of the S₁ → S₀ fluorescence were measured at room temperature. These studies will contribute to further choice and application of the liquid crystals.