An in situ electrochemical fabrication of layer by layer graphenized graphite polyaniline as a stable solid‐phase microextraction fiber coating for trace environmental analysis

A layer by layer graphenized graphite/polyaniline coating was fabricated on commercial pencil lead substrate by an in situ facile, fast and efficient electrochemical procedure. The electrodeposited polyaniline film on surface‐confined graphene structure can integrate the advantages of the both layers and was used for solid‐phase microextraction. Effective experimental parameters in electrochemical production of graphene nanosheets and electropolymerization of aniline were optimized. The prepared fiber was used for extraction and determination of four polycyclic aromatic hydrocarbons: phenanthrene, anthracene, fluoranthene and pyrene in aqueous samples by high performance liquid chromatography. The fiber coating was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy. Under the optimized conditions, the coating provided good linear ranges (0.10–25 μg/L for phenanthrene, 0.05–12.5 μg/L for anthracene, 0.825–99 μg/L for fluoranthene and 0.625–75 μg/L for pyrene (R² = 0.999)) and limits of detection, 0.016 to 0.275 μg/L. The produced coating has several attractive features such as high stability, low cost and long operation time.     

Active protective Al–Ce alloy coating electrodeposited from ionic liquid

The electrochemical co-deposition of Al–Ce metallic protective coating with active inhibiting effect was performed for the first time using an ionic liquid as an electrolyte. Cerium was successfully co-deposited with aluminium on surface of Pt and AA2024 aluminium alloy forming uniform films with globular micro-structure and thickness up to 75 μm.Cerium was introduced into the aluminium coating as a potential corrosion inhibitor which can be liberated during sacrificial dissolution of the galvanic layer deposited on the alloy surface. The released inhibitor provides an additional active corrosion protection slowing down the corrosion processes in the defects.     

Corrosion resistance of zinc electrodeposited from acidic and alkaline electrolytes using pulse current

Corrosion resistance of zinc coatings was investigated in an accelerated corrosion test in a condensation chamber. Zinc was electrodeposited from alkaline and acidic electrolytes using direct current (DC) or pulse current (PC). The zinc coating was subsequently protected against corrosion with a chrome (III) layer. Morphology and structure of the coatings was investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) before and after the corrosion test. Corrosion resistance of alkaline zinc coatings electrodeposited with DC and PC under test conditions was found to be comparable. The corrosion resistance of zinc coatings deposited from acidic electrolytes by PC was lower in comparison with corrosion resistance of zinc coatings deposited using DC. Presented at the 8th Conference on Solid State Chemistry, Bratislava, Slovakia, 6–11 July 2008.     

Direct synthesis of nitrogen-doped graphene on platinum wire as a new fiber coating method for the solid-phase microextraction of BXes in water samples: Comparison of headspace and cold-fiber headspace modes

In this work, a new solid-phase microextraction fiber was prepared based on nitrogen-doped graphene (N-doped G). Moreover, a new strategy was proposed to solve problems dealt in direct coating of N-doped G. For this purpose, first, Graphene oxide (GO) was coated on Pt wire by electrophoretic deposition method. Then, chemical reduction of coated GO to N-doped G was accomplished by hydrazine and NH₃. The prepared fiber showed good mechanical and thermal stabilities. The obtained fiber was used in two different modes (conventional headspace solid-phase microextraction and cold-fiber headspace solid-phase microextraction (CF-HS-SPME)). Both modes were optimized and applied for the extraction of benzene and xylenes from different aqueous samples. All effective parameters including extraction time, salt content, stirring rate, and desorption time were optimized. The optimized CF-HS-SPME combined with GC-FID showed good limit of detections (LODs) (0.3–2.3 μg/L), limit of quantifications (LOQs) (1.0–7.0 μg/L) and linear ranges (1.0–5000 μg/L). The developed method was applied for the analysis of benzene and xylenes in rainwater and some wastewater samples.     

A high performance nano-structure conductive coating on a Crofer22APU alloy fabricated by a novel spinel powder reduction coating technique

A nano-structure conductive coating was fabricated on a Crofer22APU alloy interconnect by an original coating strategy using Mn_0.9Y_0.1Co₂O₄ (MYC) novel spinel nanocrystalline powder. A unique treatment method by which the spinel powder was reduced was used to prepare the green coating. The resulting coating was about 12 μm in thickness, and was composed of MYC nanocrystalline with an average particle size of about 100 nm. The coating was well adhered with the substrate alloy. Less than 4 mΩ cm² of the area specific resistance (ASR) was obtained, and no obvious degradation was observed for a coated alloy (whose coating thickness was about 30 μm) after operated at 800 °C for 538 h under seven thermal cyclings. The coated alloy exhibited excellently electrical performance and long-term stability compared with the uncoated one. The exploration of the novel spinel powder reduction coating technique for alloy interconnect to obtain cheap coatings with excellent microstructure and performance showed a promising prospect for the practical application of solid oxide fuel cells (SOFCs).     

Synthesis,characterization and electrocatalytic activity for ethanol oxidation of carbon supported Pt,Pt–Rh,Pt–SnO2 and Pt–Rh–SnO2 nanoclusters

Nanoclusters of Pt, Pt–Rh, Pt–SnO₂ and Pt–Rh–SnO₂ were successfully synthesized by polyol method and deposited on high-area carbon. HRTEM and XRD analysis revealed two phases in the ternary Pt–Rh–SnO₂/C catalyst: solid solution of Rh in Pt and SnO₂. The activity of Pt–Rh–SnO₂/C for ethanol oxidation was found to be much higher than Pt/C and Pt–Rh/C and also superior to Pt–SnO₂/C. Quasi steady-state measurements at various temperatures (30–60 °C), ethanol concentrations (0.01–1 M) and H₂SO₄ concentrations (0.02–0.5 M) showed that Pt–Rh–SnO₂/C is about 20 times more active than Pt/C in the potential range of interest for the fuel cell application.     

Reaction of CO oxidation on platinum,rhodium, a platinum-rhodium alloy,and a heterophase bimetallic platinum/rhodium surface

The reaction of CO oxidation on thin metal films of platinum, rhodium, and their alloy and on a heterophase bimetallic Pt/Rh surface that consisted of platinum particles of size 10–20 nm on the surface of rhodium was studied in the region of low reactant pressures (lower than 2 × 10^?5 mbar). At low temperatures (T < 200°C), the activity of samples increased in the order Rh > Pt/Rh > Pt-Rh alloy > Pt. Above 200°C, the rate of reaction on the heterophase Pt/Rh surface was almost twice as high as the sum of the rates of reaction on the individual metals; this fact is indicative of a synergistic effect. The nature of this effect is considered.     

Evaluation of tungsten–rhodium coating on an integrated platform as a permanent chemical modifier for cadmium,lead, and selenium determination by electrothermal atomic absorption spectrometry

A tungsten–rhodium coating on the integrated platform of a transversely heated graphite atomizer is proposed as a permanent chemical modifier for the determination of Cd, Pb, and Se by electrothermal atomic absorption spectrometry. It was demonstrated that coating with 250 μg W+200 μg Rh is as efficient as the conventional Mg(NO₃)₂+NH₄H₂PO₄ or Pd+Mg(NO₃)₂ modifiers for avoiding most serious interferences. The permanent W–Rh modifier remains stable for 300–350 firings of the furnace, and increases tube lifetime by 50%–100% when compared to pyrolytic carbon integrated platforms. Also, there is less degradation of sensitivity during the atomizer lifetime when compared with the conventional modifiers, resulting in a decreased need of re-calibration during routine analysis. The characteristic masses and detection limits achieved using the permanent modifier were respectively: Cd 1.1±0.4 pg and 0.020 μgL⁻¹; Pb 30±3 pg and 0.58 μgL⁻¹ and Se 42±5 pg and 0.64μgL⁻¹. Results from the determination of these elements in water reference materials were in agreement with the certified values, since no statistical differences were found by the paired t-test at the 95% level.     

Mesoporous titanium oxide with high‐specific surface area as a coating for in‐tube solid‐phase microextraction combined with high‐performance liquid chromatography for the analysis of polycyclic aromatic hydrocarbons

Stainless‐steel wires coated with mesoporous titanium oxide were placed into a polyether ether ketone tube for in‐tube solid‐phase microextraction, and the coating sorbent was characterized by X‐ray diffraction and scanning electron microscopy. It was combined with high‐performance liquid chromatography to build an online system. Using eight polycyclic aromatic hydrocarbons as the analytes, some conditions including sample flow rate, sample volume, organic solvent content, and desorption time were investigated. Under optimum conditions, an online analysis method was established and provided good linearity (0.03–30 μg/L), low detection limits (0.01–0.10 μg/L), and high enrichment factors (77.6–678). The method was applied to determine target analytes in river water and water sample of coal ash, and the recoveries are in the range of 80.6–106.6 and 80.9–103.5%, respectively. Compared with estrogens and plasticizers, extraction coating shows better extraction efficiency for polycyclic aromatic hydrocarbons.     

Studies on surface treatment of electrodeposited Ni–Zn alloy coatings using saccharin additive

Journal of Solid State Electrochemistry - Ni–Zn alloy coatings were electrodeposited galvanostatically at room temperature. Saccharin (0 to 1.8&nbsp;g&nbsp;L−1) was added in the...     

Development of a solid‐phase microextraction fiber by the chemical binding of graphene oxide on a silver‐coated stainless‐steel wire with an ionic liquid as the crosslinking agent

Graphene oxide was bonded onto a silver‐coated stainless‐steel wire using an ionic liquid as the crosslinking agent by a layer‐by‐layer strategy. The novel solid‐phase microextraction fiber was characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and Raman microscopy. A multilayer graphene oxide layer was closely coated onto the supporting substrate. The thickness of the coating was about 4 μm. Coupled with gas chromatography, the fiber was evaluated using five polycyclic aromatic hydrocarbons (fluorene, anthracene, fluoranthene, 1,2‐benzophenanthrene, and benzo(a)pyrene) as model analytes in direct‐immersion mode. The main conditions (extraction time, extraction temperature, ionic strength, and desorption time) were optimized by a factor‐by‐factor optimization. The as‐established method exhibited a wide linearity range (0.5–200 μg/L) and low limits of determination (0.05–0.10 μg/L). It was applied to analyze environmental water samples of rain and river water. Three kinds of the model analytes were quantified and the recoveries of samples spiked at 10 μg/L were in the range of 92.3–120 and 93.8–115%, respectively. The obtained results indicated the fiber was efficient for solid‐phase microextraction analysis.     

Anodic stripping voltammetric analysis of trace arsenic(III) enhanced by mild hydrogen-evolution at a bimetallic Au–Pt nanoparticle modified glassy carbon electrode

A glassy carbon electrode (GCE) modified with electrodeposited bimetallic Au–Pt nanoparticles (Au–PtNPs) was applied to sensitively detect As(III) by linear sweep anodic stripping voltammetry (LSASV). In 0.5 M aqueous H₂SO₄, atomic hydrogen and molecular hydrogen were easily electrogenerated at the Pt sites on Au–PtNPs/GCE, which can chemically reduce As(III) to As(0) and enhance the cathodic preconcentration of As(0) at both the Pt sites and the neighboring Au sites. Since the As(0)–Au affinity is weaker than the As(0)–Pt affinity, the preconcentrated As(0) can be rapidly oxidized on/near the surface Au sites of Au–PtNPs/GCE, yielding sharper and higher LSASV current peaks. Under optimum conditions (700 s preconcentration at − 0.1 V, 5 V s^− 1), the LSASV peak current for the As(0)–As(III) oxidation responded linearly to As(III) concentration from 0.005 to 3.0 μM with a limit of detection (LOD) of 3.7 nM (0.28 ppb) (S/N = 3), while that for the As(III)–As(V) oxidation was linear with As(III) concentration from 0.01 to 3.0 μM with a LOD of 6.0 nM (0.45 ppb) (S/N = 3). This method was applied for analysis of As(III) in real water samples.     

Improved antibacterial properties of an Mg‐Zn‐Ca alloy coated with chitosan nanofibers incorporating silver sulfadiazine multiwall carbon nanotubes for bone implants

Bacteria‐caused infection remains an issue in the treatment of bone defects by means of Mg‐Zn‐Ca alloy implants. This study aimed to improve the antibacterial properties of an Mg‐Zn‐Ca alloy by coating with chitosan‐based nanofibers with incorporated silver sulfadiazine (AgSD) and multiwall carbon nanotubes (MWCNTs). AgSD and MWCNTs were prepared at a weight ratio of 1:1 and then added to chitosan at varying concentrations (ie, 0, 0.25, 0.5, and 1.5 wt.%) to form composites. The obtained composites were ejected in nanofiber form using an electrospinning technique and coated on the surface of an Mg‐Zn‐Ca alloy to improve its antibacterial properties. A microstructural examination by scanning electron microscopy (SEM) revealed the diameter of chitosan nanofiber ejected increased with the concentration of AgSD‐MWCNTs. The incorporation of AgSD‐MWCNTs into the chitosan nanofibers was confirmed by Fourier transform infrared spectroscopy (FTIR). Examination of the antibacterial activity shows that chitosan nanofibers with AgSD‐MWCNTs can significantly inhibit the growth and infiltration of Escherichia coli and Staphylococcus aureus. Biocompatibility assay and cell morphology observations demonstrate that AgSD‐MWCNTs incorporated into nanofibers are cytocompatible. Taken together, the results of this study demonstrate the potential application of electrospun chitosan with AgSD‐MWCNTs as an antibacterial coating on Mg‐Zn‐Ca alloy implants for bone treatment.     

Silicon carbide nanomaterial as a coating for solid‐phase microextraction

Silicon carbide has excellent properties, such as corrosion resistance, high strength, oxidation resistance, high temperature, and so on. Based on these properties, silicon carbide was coated on stainless‐steel wire and used as a solid‐phase microextraction coating, and polycyclic aromatic hydrocarbons were employed as model analytes. Using gas chromatography, some important factors that affect the extraction efficiency were optimized one by one, and an analytical method was established. The analytical method showed wide linear ranges (0.1–30, 0.03–30, and 0.01–30 μg/L) with satisfactory correlation coefficients (0.9922–0.9966) and low detection limits (0.003–0.03 μg/L). To investigate the practical application of the method, rainwater and cigarette ash aqueous solution were collected as real samples for extraction and detection. The results indicate that silicon carbide has excellent application in the field of solid‐phase microextraction.     

Introduction of a coiled solid‐phase microextraction fiber based on a coating of animal bone waste for chromatographic analysis

We attempt to introduce animal bone waste as a coating material with an organic−inorganic structure for the fabrication of a coiled solid‐phase microextraction fiber for the first time. The coiled fiber was simply prepared with the use of copper wire and coated with bone waste suspension through the dip‐coating method. The bone waste coating was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction analysis. It was applied as new type of solid‐phase microextraction fiber for preconcentration of polycyclic aromatic hydrocarbons before determination by high‐performance liquid chromatography with UV detection. A wide linear range 0.01–99.0 μg/L and limits of detection in the range 3.0–11.1 ng/L were obtained at optimized conditions. The bone waste coated coiled solid‐phase microextraction fiber has promise in sample preparation techniques because it is cost effective, available, stable in aqueous and organic solutions, environmentally friendly, and easy to fabricate and operate.     

Determination of platinum, palladium and rhodium in biological and environmental samples by low temperature electrothermal vaporization inductively coupled plasma atomic emission spectrometry with diethyldithiocarbamate as chemical modifier

A novel method for inductively coupled plasma atomic emission spectrometry (ICP-AES) determination of trace amounts of Pt(II), Pd(II) and Rh(III), based on gaseous compounds introduction into the plasma as their diethyldithiocarbamate complexes by electrothermal vaporization (ETV), was developed. At the temperature of 1100 °C, the trace amounts of Pt, Pd and Rh were vaporized into plasma. The factors affecting the formation of the chelates and their vaporization behaviors, such as ashing temperature and time, vaporization temperature and time, pH and the concentration of chelating reagents were studied in detail. Under the optimized conditions, the limits of detection (LODs) (3σ) of Pt, Pd and Rh for tested solutions were 5.4, 1.4 and 0.8 ng ml⁻¹, and for actual sample (auto-catalyst NIST SRM 2557) were 0.27, 0.07 and 0.04 μg g⁻¹, respectively. The relative standard deviations (RSDs) for Pt, Pd and Rh were 1.4, 2.6 and 2.4% (C_Pt=0.5 μg ml⁻¹, C_Pd,Rh=0.25 μg ml⁻¹, n=7), respectively. The linear ranges of calibration graphs for Pt, Pd and Rh cover three orders of magnitude. Compared with conventional electrothermal vaporization technique, using the reagent of diethyldithiocarbamate as chemical modifier could not only enhance the analytical sensitivities, but also reduce the vaporization temperature. By combination with a separation/preconcentration step, the proposed method had been successfully applied to the analysis of the artificial seawater, tap water and urine with recoveries ranging from 91 to 106%. The two certified reference material meager platinpalladium ore GBW 07293 and auto-catalyst NIST SRM 2557 was also analyzed for validation, and the determined values obtained were in good agreement with the certified values.     

Electrodeposition of a nickel-based hydrotalcite on Pt nanoparticles for ethanol and glucose sensing

Two different substrates, GC and graphite electrodes, have been coated with electrodeposited Pt nanoparticles (PtNPs) of different morphologies and sizes (from 2 μm to 20 nm). The electrochemical behavior of the platinised GC electrodes has been mainly evaluated in terms of the increase of the real surface area. A nickel-based hydrotalcite-like compound (HT) has been electrosynthesised on the GC platinised electrodes, by the cathodic reduction of a 0.03 M Ni and Al nitrates solution, and the cyclic voltammetric responses to these electrodes have been measured in a 0.1 M NaOH solution. Finally, the electrocatalytic performances of the GC–PtNPs–HT electrodes to ethanol and glucose have been investigated and compared with the performances of HT electrodeposited onto bare Pt, in the same conditions.     

Oxidative stress induced antimicrobial efficacy of chitosan and silver nanoparticles coated Gutta-percha for endodontic applications

Root canal treatment is the most effective treatment for irreversible pulpal damage. However, it suffers the risk of failure due to micro-leakage at the Gutta-percha-sealer-tooth interface. Concerning the issue, it is important to enhance the antimicrobial properties of Gutta-percha. The current study describes a novel coating of the Gutta-percha with chitosan and silver nanoparticles to increase their antimicrobial efficacy. They were coated with chitosan and silver nanoparticles with concentrations of 1%, 2% using chemical methodology. Coated Gutta-percha were evaluated for their antimicrobial efficacy against E. faecalis, which is frequently isolated microorganism in failed endodontic cases using standard microbiological methods like growth curve analysis. Detailed analysis of the antimicrobial activity was performed by live-dead analysis with the help of flow cytometry and fluorescent microscopy. Although, the experimental analysis showed concentration-dependent antibacterial activity by both chitosan and silver NP coated Gutta-percha, the silver NP coating exhibited higher antibacterial activity compared to the Gutta percha coated with chitosan nanoparticles. Mechanistic evaluation unveiled the cause of antibacterial activates due to action of induced oxidative stress and membrane damage to the bacteria by coated nanoparticles. The information will be useful for the endodontist to have an alternative filling material with higher antibacterial potency for higher success rate of root canal therapies in clinical procedures.     

Solar light-driven photocatalytic production of hypochlorous acid over Pt/WO3 in seawater for marine antifouling

The hypochlorous acid (HCIO) was synthesized from seawater by the Pt/WO₃ photocatalyst under visible-light irradiation. The effect of WO₃ morphology and Pt loading on the performance of the composite photocatalyst for the production of HCIO has been studied in detail. The study found that among the series of materials, hollow WO₃ microspheres with a diameter of about 3 μm loaded with 1.0 wt% Pt have the best HCIO production performance. Over it, 14.52 μM of HClO (1.24 mg/L of free chlorine) was accumulated in 0.5 M NaCl solution after 2 h of visible-light photoirradiation. What is more, the concentration of HClO can reach 4.34 μM (0.354 mg/L free chlorine) in natural seawater for 1 h using this Pt/WO₃ photocatalyst. Under visible-light irradiation, the Pt/WO₃ photocatalyst has a good broad-spectrum antibacterial activity and the activity of inhibiting marine fouling algae. The Pt/WO₃ photocatalyst has high stability and reusability. All these characteristics are conducive to the application in the field of marine antifouling. Moreover, the photocatalytic reaction mechanism was evaluated by studying the photoelectrochemical properties of Pt/WO₃/FTO. This research provides a new strategy for replacing the traditional electrolytic marine antifouling system with the visible-light-catalyzed HClO production system.

     

A modified polyvinylchloride surface with antibacterial and antifouling functions

Surfaces with antibacterial and hydrophilic properties are very attractive to cardiovascular applications. The objective of this study was to synthesize and immobilize a novel antibacterial and hydrophilic polymer onto surface of polyvinylchloride via an effective and mild surface coating technique. The surface coated with a terpolymer constructed with N‐vinylpyrrolidone, 3,4‐dichloro‐5‐hydroxy‐2(5H)‐furanone derivative, and succinimide residue was evaluated with cell adhesion, bacterial adhesion, and bacterial viability. 3T3 mouse fibroblast cells and two bacteria species were used to evaluate surface adhesion and antibacterial activity. Results showed that the polymer‐modified polyvinylchloride surface exhibited not only significantly decreased 3T3 fibroblast cell adhesion with a 66% to 87% reduction but also significantly decreased bacterial adhesion with 69% to 87% and 52% to 74% reduction of Pseudomonas aeruginosa and Staphylococcus aureus attachment, respectively, as compared with original polyvinylchloride. Furthermore, the modified polyvinylchloride surfaces exhibited significant antibacterial functions by inhibiting bacterial growth (75%‐84% and 78–94% inhibition of P aeruginosa and S aureus, respectively, as compared to original polyvinylchloride) and killing bacteria. These results demonstrate that covalent polymer attachment conferred antifouling and antibacterial properties to the polyvinylchloride surface.