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The purpose of this paper is to reveal the mechanism of nitrite (NO_2⁻) for the surface passivation of carbon steels in acidic environments through investigating the influences of 0.01 mol/L NaNO₂ addition on the corrosion and passivation behaviors of Q235 carbon steel in acidic phosphate buffer (APB) solutions (pH 2 to 6).

The electrochemical techniques including open circle potential evolution, potentiodynamic polarization, electrochemical impedance spectroscopy and cyclic voltammetry were applied.

In APB solutions without NO_2⁻, the Q235 steel presented the electrochemical behaviors of activation (A), activation-passivation-transpassivation and self-passivation-transpassivation at pH 2 to 4, pH 5 and pH 6, respectively; the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6.

In APB solutions without NO_2⁻, the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6. With the addition of 0.01 mol/L NaNO₂, into APB solutions, the variation of corrosion rate showed the same rule, but the surface passivation occurred over the whole acidic pH range, including the anodic passivation at pH 2 to 4 and the spontaneous passivation at pH 5 to 6.

The purpose of this study is to investigate the initial corrosion behavior of pure Mg, AZ31 and AZ91 alloys in phosphate buffer solution (PBS) and to characterize the features in corrosion type and resistance of the corrosion product layer.

The scanning electron microscopy, equipped with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy have been used to characterize the as-corroded samples. Besides, the Mg²⁺ concentration in PBSs has been determined by inductively coupled plasma atomic emission spectrum.

It has been found that pure Mg suffers pit corrosion, and AZ31 initially undergoes pit corrosion and then uniform corrosion dominates with an extended immersion duration. However, AZ91 exhibits the uniform corrosion with the highest corrosion rate among the three materials. Besides, the corrosion product layer on AZ31 has the best compactness and corrosion resistance.

The findings add depth in understanding the corrosion of pure Mg and its alloys in PBS and also have guiding significance in exploring the effects by alloyed elements to develop new biomaterials with better performance.

The aim of this work was to propose a method to prepare composite phosphate conversion coating (CPCC), including ternary phosphate conversion coating (TPCC) and binary phosphate conversion coatings (BPCC), with one-step chemical conversion and to reveal and compare the corrosion resistance between TPCC and BPCC.

In this work, a calcium–manganese–zinc (Ca–Mn–Zn) TPCC was prepared on the surface of magnesium alloy (MA) AZ91D with one-step chemical conversion method; for Ca-Mn-Zn@TPCC, its microstructure was characterized with scanning electron microscope observation and scanning tunneling microscope detection, and its composition was characterized with energy dispersion spectroscopy and X-ray photoelectron spectroscopy analyses. Particularly, the corrosion resistance of Ca-Mn-Zn@TPCC and its comparison with Ca–Mn, Ca–Zn and Mn–Zn BPCCs were clarified with electrochemical and immersion measurements.

Ca-Mn-Zn@TPCC, which was composed of Ca, Mn, Zn, P and O, exhibited a mud-shaped with cracks microstructure, and the average crack width, terrain fluctuation and coating thickness were 0.61 µm, 23.78 nm and 2.47 µm, respectively. Ca-Mn-Zn@TPCC provided good corrosion resistance to MA AZ91D; in NaCl solution, the total degradation of Ca-Mn-Zn@TPCC consumed eight days; corrosion products with poor adhesion peeled out from Ca-Mn-Zn@TPCC-coated MA AZ91D spontaneously. Besides, the corrosion resistance of Ca-Mn-Zn@TPCC was better than that of Ca-Mn@BPCC, Ca-Zn@BPCC or Mn-Zn@BPCC.

The successful preparation of Ca-Mn-Zn@TPCC on MA AZ91D surface confirmed the proposed method to prepare CPCC with one-step chemical conversion was feasible; at the same time, it was further confirmed that for phosphate conversion coating, ternary coating had better corrosion resistance than binary coating did.

The purpose of this study is determination of cadmium using silver-gold bimetallic nanoparticles (Ag-Au BMNPs) and an aptamer modified glassy carbon electrode.

The maximum response of modified electrode was obtained with, 50 mV pulse amplitude, 20 mV/s scan rate in phosphate buffer of pH 4.0. Ag-Au BMNPs, as the mediators improved electron transmit during the entire electron transfer process and the aptasensor response. Herein, the authors used aptamer as the capture probe to prepare an aptasensor with enhanced stability.

The proposed aptasensor exhibited a wide linearity to cadmium in the range of 0.001–0.100 µg/L with a low detection limit of 0.005×10⁻³ µg/L. The glassy carbon electrodes with Ag-Au BMNPs showed a lower detection limit.

This aptasensor has good reproducibility, stability and repeatability and is cost-effective to regenerate. The specificity and selectivity of the novel modified electrode is tested in the presence of other interfering metal ions such as Fe²⁺, Mn²⁺, Mg²⁺, Sb³⁺ and Bi³⁺. The aptasensor shows 10 times more sensitivity and selectivity for Cd²⁺ ions.

This paper aims to develop an inexpensive, portable, sensitive and environmentally friendly electrochemical sensor to quantify trace metals.

A sensor was constructed by modifying carbon paste electrode for the determination of lead, cadmium and zinc ions using square wave anodic stripping voltammetry (SWASV). The modified electrode was prepared by inserting homogeneous mixture of 2-hydroxy-acetophenonethiosemicarbazone, graphite powder and mineral oil. Various important parameters controlling the performance of the sensor were investigated and optimized. Electrochemical behavior of modified electrode was characterized by cyclic voltammetry.

Modified carbon pastes electrodes showed three distinct peaks at −0.50, −0.76 and −1.02 V vs silver/silver chloride corresponding to the oxidation of lead, cadmium and zinc ions at the electrode surface, respectively. The highest peak currents for all the metal ions under study were observed in the phosphate buffer solution at pH 1 with a deposition time of 70 s. The sensor exhibited linear behavior in the range of 0.25-12.5 μg mL-1 for lead and cadmium and 0.25-10.0 μg mL⁻¹ for zinc. The limit of detection was calculated as 78.81, 96.17 and 91.88 ng mL⁻¹ for Pb2⁺, Cd2⁺and Zn2⁺, respectively. The modified electrode exhibited good stability and repeatability.

A chemically modified electrode with Schiff base was applied to determine the content of cadmium, lead and zinc ions in aqueous solutions using SWASV.

The emergence of tissue engineering has led to the development of three‐dimensional cellular scaffolds that reconstruct the tissue structure. Research into the use of biodegradable materials in scaffolds has grown; the aim is that when tissue growth is complete, the scaffold degrades completely. This research aims to design novel scaffolds and investigates biodegradable polylactide (PLA) yarns; in particular, poly(l‐lactide) (PLLA) yarns extruded in‐house. To study degradation and determine the effect on the biodegradable yarns/textiles, they were immersed in phosphate buffer solution (PBS, pH=7.4) for various durations at 37°C. Mechanical properties were evaluated on tensile testing rigs and they were observed, before and after the immersion period. Cells were then cultured (37°C, 5 per cent carbon dioxide in air) on the textiles for 1 week. As expected, after immersion, the yarns exhibit a decrease in elongation and tenacity. Initial results indicate that the yarn properties influence cell attachment and spreading.

A new electrochemical analysis based on ß-cyclodextrin (ß-CD) was developed for penicillin V (Peni-V) using polyaniline as a conducting polymer.

The preparation of modified electrode involves the incorporation of β-CD with membrane of polyaniline. Polyaniline, incorporating β-CD, was prepared by electrochemical polymerization method in a medium of hypochloride. Cyclic voltammetry and electrochemical impedance have been used to characterize this sensor. The detection and the kinetic study of modified platinum electrode are evaluated.

Results clearly indicate that β-CDs interfere with the polymerization mechanism with an inhibition factor. The inclusion phenomenon of β-CDs has been studied and applied to detect Peni-V. The principle of this electrochemical sensor is based on the chemical properties of β-CD, which were studied using the cyclic voltammetric method and impedance spectroscopy. The electrochemical behavior of Peni-V at concentrations between 10^–8 and 10^–2 M was measured versus Ag/AgCl at pH 7.4 and 30°C in a phosphate alkaline buffer. Relationship of Peni-V concentration in logarithmic mathematical form with current in potentiometric method and with resistance in impedimetric method were obtained.

The present study showed that the Pt electrode modified with Polyaniline–β-CD was an excellent candidate for sensitive penicillin analysis. The proposed electroanalytical technique is rapid, simple and inexpensive.

The purpose of this paper is to study the immobilization of porcine pancreatic lipase (PPL), in an organic matrix by a covalent cross-linking method to sense propylparaben (PP) present in aqueous solution.

PPL immobilization was performed by the covalent cross-linking method, using bovine serum albumin (BSA) in the presence of saturated glutaraldehyde vapor (GA). The preparation of the enzymatic membrane involves the incorporation of porcine pancreatic lipase (PPL), bovine serum albumin (BSA) and glycerol into a phosphate buffer solution (PBS). Characterization of this sensor was performed by impedance spectroscopy (EIS) and scanning electron microscope (SEM). The effect of experimental conditions such as PPL activity, potential, scan rate, PP concentration, pH and presence of interfering elements were studied by cyclic voltammetry.

Under the optimal experimental conditions, a number of significant factors were optimized. The method exhibited good linearity in the range of 10^–14 to 10^–9 mol/L with a good correlation coefficient of 0.957, detection limit (LOD) of 3.66 × 10^–15 mol/L and high sensitivity of 1.086 mA mol⁻¹L. The authors also obtained a very good coverage rate of the surface equal to 91.44%, and hydrolytic activity of lipase is evaluated to 26.64 mmol min⁻¹. The stability and the interference were also evaluated. The equivalent circuit used to explain the electrochemical behavior of modified electrode is a Randle circuit.

The main application of biosensors is the detection of biomolecules that are either indicators of a disease. For example, electrochemical biosensing techniques can be used as clinical tools to detect breast tumors, because these compounds (PP) were found in breast tumors.

The result registered in this paper indicates that the developed sensor is an efficient, fast, simple and inexpensive analytical tool that can be used for the analysis of water containing PP.

The behaviour of iron electrodes immersed in pH 8.9‐11.0 Na₂HPO₄ solutions was studied by potentiodynamic measurements (cyclic voltammetry) and scanning electron microscopy (SEM). The influence of proton and phosphate content, scan rate, anodic switching potential and other devised potential/time perturbation regimes were evaluated in order to obtain an understanding of the reactions involved during the passivation process. The oxidation‐reduction peaks were analysed using a thermodynamic approach. It was possible to reveal the most important reactions coming about on the electrode surface, which comprise, initially, the formation of Fe₃(PO₄)₂ and Fe(OH)₂ at ca. −0.8 V/SCE. Subsequently, these ferrous species are further oxidized to γ‐FeOOH at ca. −0.36 V/SCE, the latter being transformed into Fe₂O₃ in the passive region. Depending on the pH value (11.0) and scan rate (slow), Fe₃O₄ is clearly present as an intermediate oxide structure between the ferrous and ferric species mentioned earlier. In addition, scan rate was discovered to play a remarkable influence on the surface morphology observed during the SEM examinations.

The present study aims to focus on the possibility of developing new eco-friendly azo dyes with good colouristic application properties, exhibiting biological and pharmacological activities.

Coupling of 4-hydroxycoumarin with a variety of aromatic diazonium salts of 2-aminothiazole, 2-aminobenzothiazole, 4-aminoantipyrine, 4-aminoacetophenone, adenine sulphate, a-naphthylamine and sulphadimidine to produce novel azo dyes. The compounds were fully characterised using spectroscopic and analytical methods. All of the compounds were tested for their antimicrobial, anticancer and antioxidant activities. The prepared dyestuffs were dyed on polyester fabrics and subsequently their dyeing properties, light, washing, perspiration, rubbing and sublimation fastness were determined.

The spectroscopic data of the synthesised compounds have provided decisive evidence that such compounds exist in the solid state as the azo-dike to form C and in solution in equilibrium tautomer forms A, B and D. The prepared dyestuffs are suitable for either heat transfer printing or traditional printing on polyester and nylon 6 fabrics. The prints obtained from the dyes possess high colour strength, as well as good overall fastness properties. Also the synthesised compounds exhibit good biological and pharmacology activity.

Synthesis of these seven azo dyes for textile dyeing had never been reported previously.

The dyestuffs derived from 4-hydroxycoumarin are reasonable azo disperse dyestuffs giving good all round fastness properties on polyester fabrics.

Production of less expensive and new eco-friendly dyes exhibit antimicrobial and anticancer activity.

It provided a potentially simple way to synthesize novel coumarin azo-dyes exhibit good biological and pharmacology activity and also exhibit good overall fastness properties.