Detection of chemical warfare agent Nitrogen Mustard-1 based on conducting polymer phthalocyanine nanorod modified electrode

A simple method is reported for the detection of chemical warfare agent Nitrogen Mustard-1 (NM-1) by using a modified electrode which was prepared by electrochemically immobilizing copper phthalocyanine (CuPc) into polypyrrole (pPy) in presence of a cationic surfactant cetyltrimethylammonium bromide (CTAB) during the polymerization of pyrrole in an aqueous solution. The surface of the modified and bare electrodes are characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques in order to know the surface morphology and elemental composition of the modified electrodes, respectively. SEM images indicated the presence of nanorods on pPy/CuPc/CTAB sample and EDS study confirmed the nanorods as CuPc. Moreover, EDS study confirmed that the nanorods are only on the pPy matrix and not inside the pPy. FTIR results confirmed the presence of CuPc in pPy film. AC impedance spectroscopy analysis of the modified electrode with NM-1 exhibited more electron transfer resistance. The prepared modified electrode showed good electrochemical activity with NM-1 when compared to the unmodified gold electrode.     

Inhibitive properties of 2,5-bis(n-methylphenyl)-1,3,4-oxadiazole and biocide on corrosion,biocorrosion and scaling controls of brass in simulated cooling water

2,5-Bis(n-methylphenyl)-1,3,4-oxadiazole with (n = 2,3,4), denoted n-MPOX, have been investigated by using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) methods, to evaluate the electrochemical behavior of brass in simulated cooling water system. The PP study revealed that oxadiazole inhibited both cathodic and anodic reactions, indicating a mixed type control of inhibition. It was shown that, 3-MPOX as well as 4-MPOX, were the best inhibitors and the inhibition efficiency followed the sequence: 3-MPOX ⩾ 4-MPOX ≫ 2-MPOX. The interference between non-oxidizing biocide CTAB and 3-MPOX and 4-MPOX against corrosion and biocorrosion has also been studied.     

Function of cobalt in the new type rare-earth Mg-based hydrogen storage electrode alloys

The role of cobalt on the structural and electrochemical properties of the La_0.7Mg_0.3Ni_3.4−xMn_0.1Co_x (x=0–1.15) hydrogen storage alloys were investigated systematically. XRD and Rietveld analyses show that all alloys consist mainly of the (La,Mg)Ni₃ phase and the LaNi₅ phase. P–C isotherms illustrate that the equilibrium pressure for hydrogen decreases monotonically with increasing x. Electrochemical studies indicate that the maximum discharge capacity first increases from 397.5 (x=0) to 403.1 mA h/g (x=0.75) and then decreases to 388.2 mA h/g (x=1.15). Moreover, with increasing Co substitution, the cycling durability of the alloy electrodes was markedly improved due to the decrease in the pulverization of the alloy particles and the corrosion of La in KOH solution. The high rate dischargeability, electrochemical impedance spectrum, linear polarization, Tafel polarization and potential-step measurements all indicate that the electrochemical kinetics of the alloy electrodes first increases and then decreases with increasing Co content.     

Polypyrrole-polyethylene glycol conducting polymer composite films: Preparation and characterization

The preparation and characterization of polypyrrole-polyethylene glycol (PPy-PEG) composite films are reported in this present paper. The polypyrrole-polyethylene glycol composites were synthesized by electrochemical method, using p-toluene sulfonate as a dopant in aqueous medium. The composite films were synthesized with various concentration of PEG and were characterized by optical microscopy, x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, photoacoustic spectroscopy and electrical conductivity measurement. Both the electrical conductivity and thermal diffusivity exhibited the highest values with the process condition of 0.2 M pyrrole, 0.1 M p-toluene sulfonate and 1×10⁻³ M PEG at 1.2 V (versus SCE). The optical microscopy of PPy-PEG shows the globular surface morphology. The XRD results demonstrated that PPy-PEG composite films are amorphous. The FTIR result reveals the successful incorporation of PEG into the PPy structure forming PPy-PEG composite films.     

Oxidative electropolymerization of pyrrole from neat monomer solution

Oxidative electrochemical polymerization of pyrrole at gold, indium doped tin oxide on glass, and stainless steel type 304 was accomplished from neat monomer solution containing only supporting electrolyte (0.05–0.3 M n-tetrabutyl ammonium perchlorate, n-tetrabutyl ammonium hexafluorophosphate, or n-tetrabutyl ammonium tetrafluoroborate) by multiple scan cyclic voltammetry. The results presented demonstrate that thick (>1–14 μm), stable, highly conductive (up to 0.6 S/cm) polypyrrole films can be readily prepared on a wide range of electrode substrates using this simple electrochemical method.     

In situ UV–visible spectroelectrochemical studies on electrochromic behavior of poly(2,5-dimethoxy aniline)

The electrochromic characteristics of poly(2,5-dimethoxy aniline) (PDMA), have been evaluated using cyclic voltammetry, in situ UV–visible (UV–VIS) spectroscopy, cyclic spectrovoltammetry and spectrochronoamperometry. The results from cyclic voltammetry revealed that PDMA could be easily transformed from leucoemeraldine to emeraldine state in comparison with polyaniline (PANI). The conversion of reduced PDMA form into fully oxidized state could occur at a lower positive potential for PDMA than PANI (0.70 V for PANI and 0.27 V for PDMA). UV–VIS spectrum of PDMA showed three optical transitions at λ_max=375 nm (I), 460 nm (II) and 770 nm (III). The electrochemical transitions of PDMA while cycling the potentials were simultaneously monitored through UV–VIS spectroscopy. Results of cyclic spectrovoltammetry experiments revealed that the band at λ_max^II=460 nm corresponds to intermediate state between leucoemeraldine and emeraldine forms of PDMA. Hysteresis were noticed in the absorbance-potential profile for λ_max=375, 460 and 770 nm. The derivative cyclicvoltabstogram (DCVA) deduced from spectrovoltammetry reveals the presence of residual absorbance at E=0.0 V for PDMA. A linear correlation was noticed between half intensity of absorbance (E_1/2^A) at the wavelength 375, 460 and 770 nm and scan rate (ν). Electrochromic properties of PDMA like optical contrast, columbic efficiency and electrochromic efficiency are reported.     

TiNx coated polycarbonate for bio-electrode applications

Titanium nitride (TiN_x) thin films were deposited by PVD, in a wide range of compositions (0 < x < 0.99), on polycarbonate (PC) substrates, aiming at studying their potential application as bio-electrodes. The electrochemical study of the TiN_x films, performed in an isotonic sodium chloride solution, proved the very good chemical stability of all films in salt solution conditions. On the other hand, the electrochemical noise analysis showed that the electrical noise generated at the stoichiometric TiN/electrolyte interface is of the same magnitude as that generated by the traditional Ag/AgCl electrodes.     

Chiral conducting surfaces based on the electropolymerization of 3,4-ethylenedioxythiophene

The synthesis and electrochemical characterization of d- and l-proline functionalized monothiophenes are reported. Both monomers 2L and 2D showed anodic peak potentials of 1.86 V vs. Fc⁺/Fc and their electropolymerization affords polymers that exhibit poor stability on platinum electrodes. However, the electrochemical copolymerization using cyclic voltammetry of 2L or 2D in the presence of EDOT gives polymeric films at the surface of the electrode with specific chirality. The E_1/2 of the copolymers was found to be 0.38 V vs. Fc⁺/Fc. The copolymers display excellent electrochemical stability and adhesion properties on the surface of platinum and ITO electrodes. Moreover, the films also undergo a reversible color change between their doped (blue-green) and undoped (blue-brown) states. Incorporation of the chiral pendant group was confirmed through the appearance of characteristic CO stretching absorptions in the IR spectra of the copolymers.     

Electrochemical synthesis and redox processes of poly(paraphenylene vinylene): An in situ FTIR-attenuated total reflectance and electrochemical quartz crystal microbalance study

The electrochemical synthesis and the redox reactions of poly(paraphenylene vinylene) (PPV) have been studied by in situ Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflection method and by the electrochemical quartz crystal microbalance, EQCM, technique. The polymer material has been synthesized by electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene on a Pt-electrode in dimethylformamide or acetonitrile using tetraethylammoniumtetrafluoroborate or tetraethylammoniumtosylate as electrolyte salts. The IR spectra of the doped conducting state show a very large broad absorption band starting at 1700 cm⁻¹ and extending to 5000 cm⁻¹. Additional changes in the spectra can be seen in the region between 1700 and 700 cm⁻¹ where new absorption bands appear. The intensity for these infrared active vibrations (IRAV) increase with increasing n-doping level. The reversible charging–discharging reaction is characterized by the growth in intensity of the IRAV during charging and diminish during discharging of the PPV film. Results from FTIR spectroscopy obtained from the charging–discharging reaction are consistent with the results obtained from the EQCM experiments, which show movement of counter cations during n-doping.     

A comparative study on polyaniline degradation by an electrochemical quartz crystal impedance system: electrode and solution effects

By combining the piezoelectric quartz crystal impedance (PQCI) and electrochemical impedance spectroscopy (EIS) measurements, we conducted a comparative study on polyaniline (PANI) degradation in different media, HClO₄ and H₂SO₄, and on different piezoelectric quartz crystal (PQC) electrodes, Pt and Au. It is concluded that (1) the PANI film grown on an Au electrode is more stable than that on a Pt electrode; (2) the PANI degradation reaction abides by the zero-order kinetic law in HClO₄ with rate constants from 0.17 to 2.25 Hz s⁻¹ on Pt and 0.16 to 0.83 Hz s⁻¹ on Au, but the first-order kinetic law in H₂SO₄ with rate constants from 2.61×10⁻³ to 7.00×10⁻³ s⁻¹ on Pt and 1.00×10⁻³ to 5.00×10⁻³ s⁻¹ on Au at different ion concentrations. The contrary effects of ClO₄⁻ and SO₄²⁻ on PANI degradation may be understood from the Hofmeister series of anions; (3) the dissolution of the PANI film bulk, the increase of film porosity and the film attenuation occurred simultaneously during degradation via systematic analyses of the motional resistance (R₁)and electrochemical impedance spectra responses, etc.     

Long-term monitoring of atmospheric corrosion at weathering steel bridges by an electrochemical impedance method

Weathering steel corrosion was monitored for one to two years under natural atmosphere by an electrochemical impedance technique. Two identical comb-shape weathering steel sheets embedded in epoxy resin were used as monitoring probe electrodes at two different bridges in Japan. Impedances at 10 kHz (Z_10kHz) and 10 mHz (Z_10mHz) were automatically measured every hour. Coupons (50 × 50 × 2 mm³) prepared from the same steel sheets were exposed together to measure the corrosion mass loss. The average (Z_10mHz)⁻¹ value for half to one year exposure correlated well with the average corrosion rate determined from the corrosion mass loss.     

Electrochemical properties of poly-1-naphthylamine synthesized in the presence of ferrocenesulfonic acid

Ferrocenesulfonic acid (Fc) plays an important role in increasing the electrochemical polymerization rate of 1-naphthylamine (Nap). Poly-1-naphthylamine prepared in the presence of ferrocenesulfonic acid (PNapFc) was charaterized by FTIR, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The above results confirmed that Fc could be doped in poly-1-naphthylamine (PNpa). From FTIR spectra of PNapFc, it was revealed that polymerization reaction occurred by head-to-tail mechanism. Cyclic voltammograms (CVs) show that PNapFc has a rather high electrochemical activity compared with PNap in 0.5 mol dm⁻³ Na₂SO₄ solution at pH 5.00. Particularly, both PNpa- and PNapFc-modified electrodes can catalyze the electrochemical reduction of H₂O₂ in the 0.1 mol dm⁻³ citrate buffer with pH 5.00, but the catalytic activity of PNapFc is superior to that of PNpa, which is due to that Fc enhance the charge transfer ability in PNapFc film.     

Densification behavior,microstructure evolution,and wear performance of selective laser melting processed commercially pure titanium

This work presents a comprehensive study of the densification behavior, phase and microstructure development, hardness and wear performance of commercially pure Ti parts processed by selective laser melting (SLM). An in-depth relationship between SLM process, microstructures, properties, and metallurgical mechanisms has been established. A combination of a low scan speed and attendant high laser energy density resulted in the formation of microscopic balling phenomenon and interlayer thermal microcracks, caused by a low liquid viscosity, a long liquid lifetime, and resultant elevated thermal stress. In contrast, using a high scan speed produced the disorderly liquid solidification front and considerably large balling, due to an elevated instability of the liquid induced by Marangoni convection. A narrow, feasible process window was accordingly determined to eliminate process defects and result in full densification. The phase constitutions and microstructural characteristics of SLM-processed Ti parts experienced a successive change on increasing the applied scan speeds: relatively coarsened lath-shaped α → refined acicular-shaped martensitic α′ → further refined zigzag-structured martensitic α′, due to the elevated thermal and kinetic undercooling and attendant solidification rate. The optimally prepared fully dense Ti parts had a very high hardness of 3.89 GPa, a reduced coefficient of friction of 0.98 and wear rate of 8.43 × 10^?4 mm³ N^?1 m^?1 in dry sliding wear tests. The formation of an adherent, plastically smeared tribolayer on the worn surface contributed to the enhancement of wear performance.     

Preparation of Fe2B boride coating on low-carbon steel surfaces and its evaluation of hardness and corrosion resistance

Fe₂B coating was prepared on low-carbon steel by surface alloying. A series of experiments were carried out to examine some surface properties of boride coating. The surface heat treatment of coated low-carbon steel was performed at 700 °C, 800 °C and 900 °C for 2 h, 4 h, 6 h and 8 h under hydrogen atmosphere. The boride coating was revealed by XRD analysis and the microstructure of the boride coating was analyzed by scanning electron microscopy (SEM). Depending on the temperature and time of the process, the hardness of the borided low-carbon steel ranged from 99 to 1100 HV. The hardness showed a maximum (about 1100 HV) at 900 °C for 8 h. The corrosion resistance of the borided samples was evaluated by the Tafel polarization and electrochemical impedance spectroscopy (EIS). Shift in the corrosion potential (E_corr) towards the noble direction was observed, together with decrease in the corrosion current density (I_corr), increase in the charge transfer resistance (R_ct) and decrease in the capacitance (C_c), which indicated an improvement in corrosion resistance with increasing temperature and time of the treatment.     

Fabrication and characterization of polyaniline/porous silicon heterojunction

Heterojunction between polyaniline (PANI) and porous silicon (PS) was fabricated by making a layer of PANI on PS, using spin coating method. PS was fabricated by electrochemical etching process. PS was characterized by photoluminescence (PL), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) while the PANI was characterized by FTIR and absorption (UV–VIS) spectroscopy. Current–voltage and capacitance–voltage measurements were done to determine the electrical properties of the heterojunction structure. The ideality factor of the heterojunction was found to be 4.2, which was considered high due to large defect density at the interface. Built-in potential was measured by both I–V and C–V and was found to be Φ_b(I–V) = 0.41 V and Φ_b(C–V) = 0.28 V respectively. The discrepancy in the values of the built-in potential was discussed. Band discontinuity in conduction band and valence band were found to be 0.65 and 1.27 eV respectively. Solar response of the heterojunction was also observed at AM (air mass) 1.0 and it showed a promising behavior as a photovoltaic device.     

Improvement of corrosion resistance of Cu-based bulk metallic glasses by the microalloying of Mo

(Cu₄₇Zr₁₁Ti₃₄Ni₈)_100−xMo_x bulk metallic glasses (BMGs) with x = 0, 1 and 2 at% were prepared by water-cooled copper mold casting. The effect of the addition of a small amount of Mo on the corrosion resistance of the Cu-based BMGs was examined by electrochemical polarization and weight loss measurement in 1 mol/L H₂SO₄ open to air. It is found that the corrosion resistance of Cu-based BMGs enhanced with increasing Mo content, as indicated by the decrease in passive current density and corrosion rate with the increase in Mo content. X-ray photoelectron spectroscopy (XPS) was employed to study the composition and the state of elements in the passive film, which revealed that the improvement of corrosion resistance of Cu-based BMGs microalloyed with Mo originated from the enrichment of ZrO₂ and TiO₂, but depletion in Cu- or Ni-oxide in the passive films formed during electrochemical polarization. In addition, the galvanostatic-step measurement was performed to investigate the formation kinetics of the passive films. It is demonstrated that the addition of an appropriate amount of Mo can promote the formation of the passive film on the surface.     

Inhibition by Ginkgo leaves extract of the corrosion of steel in HCl and H2SO4 solutions

The inhibition effect of Ginkgo leaves extract (GLE) on the corrosion of cold rolled steel (CRS) in 1.0–5.0 M HCl and 0.5–2.5 M H₂SO₄ solutions was investigated for the first time by weight loss, potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods. The results show that GLE is a good inhibitor, and exhibits more efficient in 1.0 M HCl than 0.5 M H₂SO₄. The adsorption of GLE on CRS surface obeys Langmuir adsorption isotherm. GLE acts as a mixed-type inhibitor in 1.0 M HCl, while a cathodic inhibitor in 0.5 M H₂SO₄.     

2-Amino-5-(4-pyridinyl)-1,3,4-thiadiazole monolayers on copper surface: Observation of the relationship between its corrosion inhibition and adsorption structure

Corrosion inhibition behavior of 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole (4-APTD) monolayers on copper surface were investigated by electrochemical impedance spectroscopy (EIS), electrochemical polarization measurement and surface-enhanced Raman scattering (SERS) experiment. The EIS mechanism of the copper surface with 4-APTD monolayers fitted to the mode of R(Q(R(QR))). The electrochemical polarization measurements indicated high inhibition efficiency of about 90.4%. SERS results suggested that 4-APTD molecules anchored at copper surface in a tilted orientation directly via N³ and N¹² atoms. The transition adsorption states of 4-APTD on the copper surface were observed as the potential applied from 0 to −1.6 V vs. SCE.     

Effect of Au deposition rate on the performance of top-contact pentacene organic field-effect transistors

A study of the influence of the deposition rate of top-contact Au source and drain electrodes deposited by electron-beam evaporation on the electrical performance of pentacene organic field-effect transistors (OFETs) is presented. By adjusting the deposition rate of the Au electrodes to minimize metal diffusion into the semiconductor pentacene layer, the source/drain contact resistance could be reduced. At a Au deposition rate of 10 Å/s, high-performance pentacene p-channel OFETs were obtained with a field-effect mobility of 0.9 cm²/Vs and a normalized channel width resistance of 23 kΩ cm in a device with a channel length of 25 μm.     

Impact of selective oxidation during inline annealing prior to hot-dip galvanizing on Zn wetting and hydrogen-induced delayed cracking of austenitic FeMnC steel

The present study discusses the impact of selective oxidation during in-line annealing of Fe–23%Mn–0.6%C–0.3%Si steel on surface and sub-surface properties and is focused on hot-dip galvanizability and susceptibility to hydrogen-induced delayed cracking. Annealing temperature (700–1100 °C) and dewpoint DP (? 15/?30/?50 °C) of the 5%H₂–N₂ annealing atmosphere were varied in order to investigate Zn wetting in dependence on selective oxidation of Mn and Si. Sub-surface microplasticity (hardness, pop-in frequency, pop-in activation load) was examined by electrochemical nanoindentation in-situ to hydrogen charging (ECNI) to assess hydrogen/material interactions. Zn wetting fails if external Mn and Si oxidation is not avoided by performing high reductive bright annealing (1100 °C/DP ? 50 °C). Zn wetting will however turn to increase if a roughly globular MnO layer appears and Si is internally oxidized (700–900 °C/DP ? 15 °C). Selective oxidation further affects hydrogen/material interactions by influencing the local distribution of solid-soluted Mn: ECNI results indicate hydrogen-induced dislocation demobilization (HEDE mechanism) or dislocation mobilization (HELP mechanism) in dependence on the local amount of solid-soluted Mn within the sub-surface. Macroscopic delayed cracking seems to occur earlier if HELP is predominating. The gained results benefit understanding the impact of selective oxidation on galvanizability and susceptibility to hydrogen-induced failure of austenitic FeMnC steel and advance further developments in processing high Mn alloyed steels.