Optical recording using hydrogen phthalocyanine thin films

Vacuum sublimed thin films of the blue dye hydrogen phthalocyanine (H₂Pc) were incorporated into various optical recording structures. The dye was shown to be thermally, hydrolytically, and oxidatively stable. In all cases, the writing mechanisms are dependent on the sublimation of H₂Pc. Several recording structures which take advantage of the sublimation property of H₂Pc are demonstrated, including pit forming and bubble forming media. These H₂Pc-based optical recording structures show very high optical contrast and low writing threshold energies. In addition, very thin films (50–75Å) of H₂Pc were incorporated into a tellurium-based medium, which significantly enhanced the writing contrast observed in that medium.     

Growth mode and molecular orientation of phthalocyanine molecules on metal single crystal substrates: A NEXAFS and XPS study

We report on near-edge X-ray absorption and X-ray photoemission experiments for the large π-conjugated organic molecule metal-free phthalocyanine (H₂Pc) on two different single crystal surfaces. Results from H₂Pc deposited on Ag(1 1 1) at 300 K show a clear linear dichroism indicating that the film grows as islands with the molecules lying essentially flat. On a Ni₃Al(1 1 1) and a cooled Ag(1 1 1) substrate, however, the molecules form a homogeneous film and have an average tilt angle of 45-60°. The different film structure is the result of a different molecule-substrate interaction.     

Electrochemical, SEM/EDS and quantum chemical study of phthalocyanines as corrosion inhibitors for mild steel in 1 mol/l HCl

The inhibition effect of metal-free phthalocyanine (H₂Pc), copper phthalocyanine (CuPc) and copper phthalocyanine tetrasulfuric tetrasodium salt (CuPc·S₄·Na₄) on mild steel in 1 mol/l HCl in the concentration range of 1.0 × 10⁻⁵ to 1.0 × 10⁻³ mol/l was investigated by electrochemical test, scanning electron microscope with energy dispersive spectrometer (SEM/EDS) and quantum chemical method. The potentiodynamic polarization curves of mild steel in hydrochloric acid containing these compounds showed both cathodic and anodic processes of steel corrosion were suppressed, and the Nyquist plots of impedance expressed mainly as a capacitive loop with different compounds and concentrations. For all these phthalocyanines, the inhibition efficiency increased with the increase in inhibitor concentration, while the inhibition efficiencies for these three phthalocyanines with the same concentration decreased in the order of CuPc·S₄·Na₄ > CuPc > H₂Pc according to the electrochemical measurement results. The SEM/EDS analysis indicated that there are more lightly corroded and oxidative steel surface for the specimens after immersion in acid solution containing 1.0 × 10⁻³ mol/l phthalocyanines than that in blank. The quantum chemical calculation results showed that the inhibition efficiency of these phthalocyanines increased with decrease in molecule's LUMO energy, which was different from the micro-cyclic compounds.     

Influence of salts of 1,1,2,2-tetrachloroethane on the acidity function of the solutions of methanesulfonic acid

The influence of salts CH₃SO₃Na and/or CH₃SO₃Bu₄N on the acidity function H ₀ of methanesulfonic acid (MSA) and its solutions in water, N,N-dimethylformamide (DMF) in mixtures of methanesulfonic acid-N,N-dimethylformamide MSA-DMF ≤ 1 and ethyl acetate (EA) in a mixture of methanesulfonic acid-ethyl acetate MSA/EA (1: 1) and 1,1,2,2-tetrachloroethane (TCE) on H ₀ of methanesulfonic acid (MSA) and its mixtures with N,N-dimethylformamide (DMF), 2-pyrrolidine (Pyr) and ethyl acetate (EA) with the ratios of MSA: DMF equal to 1: 1 and 2: 1, MSA: Pyr (2: 1) and MSA: EA, equal to 2: 1, 1: 1, and 1: 2 is investigated by the indicator method at 25°C. It is revealed that a change in the acidity of the solutions of MSA in the aprotic solvents can occur as a result of the influence of salts both on the equilibrium composition of the nascent complexes and on their ionizing ability (both of these factors change acidity on addition of salts to the mixture of MSA-EA (1: 1)). An explanation is proposed why CH₃SO₃Na and CH₃SO₃Bu₄N influence differently on the acidity of aqueous solutions of MSA. It is established that in the solutions of (TCE) the ionizing ability of MSA and its complexes with DMF, Pyr and EA, which have different degree of the proton transfer ($ K_{T_i } $ K_{T_i } ), depends on the concentration ratio of MSA: TCE and ($ K_{T_i } $ K_{T_i } ): TCE.     

Heterogeneous adsorption and catalytic oxidation of benzene, toluene and xylene over spent and chemically regenerated platinum catalyst supported on activated carbon

The heterogeneous adsorption and catalytic oxidation of benzene, toluene and o-xylene (BTX) over the spent platinum catalyst supported on activated carbon (Pt/AC) as well as the chemically treated spent catalysts were studied to understand their catalytic and adsorption activities. Sulfuric aqueous acid solution (0.1N, H₂SO₄) was used to regenerate the spent Pt/AC catalyst. The physico-chemical properties of the catalysts in the spent and chemically treated states were analyzed by using nitrogen adsorption-desorption isotherm and elemental analysis (EDX). The gravimetric adsorption and the light-off curve analysis were employed to study the BTX adsorption and oxidation on the spent catalyst and its modified Pt/AC catalysts. The experimental results indicate that the spent Pt/AC catalyst treated with the H₂SO₄ aqueous solution has a higher toluene adsorption and conversion ability than that of the spent Pt/AC catalyst. A further studies of H₂SO₄ treated Pt/AC catalyst on their catalytic and heterogeneous adsorption behaviours for BTX revealed that the activity of the H₂SO₄ treated Pt/AC catalyst follows the sequence of benzene > toluene > o-xylene. The adsorption equilibrium isotherms of BTX on the H₂SO₄ treated Pt/AC were measured at different temperatures ranging from 120 to 180 °C. To correlate the equilibrium data and evaluate their adsorption affinity for BTX, the two sites localized Langmuir (L2m) isotherm model was employed. The heterogeneous surface feature of the H₂SO₄ treated Pt/AC was described in detail with the information obtained from the results of isosteric enthalpy of adsorption and adsorption energy distributions. Furthermore, the activity of H₂SO₄ treated Pt/AC about BTX was found to be directly related to the Henry's constant, isosteric enthalpy of adsorption and adsorption energy distribution functions.     

The corrosion inhibition and gas evolution studies of some surfactants and citric acid on lead alloy in 12.5 M H2SO4 solution

The inhibition action of the citric acid and three surfactants: sodium dodecyl sulfate (SDS), t-octyl phenoxy polyethoxyethanol (Triton X-100), sodium dodecyl benzene sulphonate (SDBS) on the corrosion behavior and gas evolution of Pb-Sb-As-Se was investigated in 12.5 M H₂SO₄ solution with linear sweep polarization, cyclic voltammetry and weight loss measurements methods. The results drawn from different techniques are comparable. It was found that these surfactants and citric acid act as good inhibitors for the corrosion of lead alloy in H₂SO₄ solution. SDS inhibited most effectively the lead alloy corrosion among the three surfactants and citric acid. The inhibition efficiency for the inhibitors decreases in the order: SDS > SDBS > Triton X-100 > citric acid > blank. The inhibition efficiency increases with rising of the inhibitor concentration. In this work, the effect of the inhibitors on hydrogen and oxygen evolution was studied. In addition, it was found that the adsorption of used inhibitors on lead alloy surface follows Langmuir isotherm.     

Investigation of etch characteristics of non-polar GaN by wet chemical etching

We characterized the surface defects in a-plane GaN, grown onto r-plane sapphire using a defect-selective etching (DSE) method. The surface morphology of etching pits in a-plane GaN was investigated by using different combination ratios of H₃PO₄ and H₂SO₄ etching media. Different local etching rates between smooth and defect-related surfaces caused variation of the etch pits made by a 1:3 ratio of H₃PO₄/H₂SO₄ etching solution. Analysis results of surface morphology and composition after etching by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) demonstrated that wet chemical etching conditions could show the differences in surface morphology and chemical bonding on the a-plane GaN surface. The etch pits density (EPD) was determined as 3.1 × 10⁸ cm⁻² by atom force microscopy (AFM).     

Mechanisms of radical removal by SO2

It is well established from experiments in premixed, laminar flames, jet-stirred reactors, flow reactors, and batch reactors that SO₂ acts to catalyze hydrogen atom removal at stoichiometric and reducing conditions. However, the commonly accepted mechanism for radical removal, SO₂ + H(+M) ? HOSO(+M), HOSO + H/OH ? SO₂ + H₂/H₂O, has been challenged by recent theoretical and experimental results. Based on ab initio calculations for key reactions, we update the kinetic model for this chemistry and re-examine the mechanism of fuel/SO₂ interactions. We find that the interaction of SO₂ with the radical pool is more complex than previously assumed, involving HOSO and SO, as well as, at high temperatures also HSO, SH, and S. The revised mechanism with a high rate constant for H + SO₂ recombination and with SO + H₂O, rather than SO₂ + H₂, as major products of the HOSO + H reaction is in agreement with a range of experimental results from batch and flow reactors, as well as laminar flames.     

Structures and magnetic properties for electrodeposited Co ultrathin films on copper

The formation of Co films on polycrystalline copper in diluted sulphuric acid was investigated by employing cyclic voltammetry (CV), atomic force microscopy, and in-situ magneto-optic Kerr effect (MOKE) techniques. By comparing CV measurements in the pure supporting electrolyte (11 mM K₂SO₄/1 mM H₂SO₄) and the cobalt sulphate solution (10 mM K₂SO₄/1 mM H₂SO₄/1 mM CoSO₄), peaks from voltammetric cycling for copper dissolution, readsorption of dissolved copper ions, cobalt bulk dissolution and oxidation of hydrogen could be resolved. As the electroplating time increases, the size of the Co clusters increases and the deposition of Co corresponds to island growth. The first hysteresis loop occurs at a Co thickness of 0.33 nm in the longitudinal configuration. For films thinner than 7 nm, the Kerr intensity increases linearly because the Curie temperature of the film is well above 300 K.     

New organic FET-like photoactive device, experiments and DFT modeling

We present the possible construction of an organic FET-like photoactive device in which source-drain current through a phthalocyanine ( H₂Pc film is affected by a photo-induced dipolar field in a photoactive “gate” electrode. The influence of the dipolar electric field on charge transfer between H₂Pc molecules is modeled by DFT quantum-chemical calculations on H₂Pc dimers and tetramers.     

Sulfidation of a Cu submonolayer at the Au(1 1 1)/electrolyte interface - An in situ STM study

We describe the electrochemical preparation of an ultrathin copper sulfide film on Au(1 1 1) and its structural characterization by in situ STM. The first step, underpotential deposition of a Cu submonolayer from CuSO₄/H₂SO₄ solution, is followed by two electrolyte exchanges for (i) Cu-free (blank) H₂SO₄ solution and (ii) NaOH/Na₂S solution. The well-known (√3 × √3)R30° structure of the upd Cu layer is stable in the blank electrolyte for at least 2 h. After exposure to bisulfide, the Cu layer contracts and forms two-dimensional islands of two distinct ordered surface phases, i.e. a rectangular and, at higher potentials, a hexagonal phase, with Cu-free Au(1 1 1) regions between them, the latter exhibiting the characteristic (√3 × √3)R30°-S adlayer structure. Potential changes lead to a complex phase behaviour including HS⁻ ? S_x oxidation/reduction and, at strongly anodic potentials, dissolution of the Cu adlayer.     

Synthesis and photophysical behavior of a novel zinc phthalocyanine containing a single carboxylic acid and three phenylthio substituents

Zinc 2, (3)-tri-(phenylthio)-2, (3)-carboxy phthalocyanine (ZnPc(COOH)(SPh)₃), zinc 2, (3)-tetra-(phenylthio) phthalocyanine (ZnPc(SPh)₄) and 2, (3)-tetra-(phenylthio) phthalocyanine (H₂Pc(SPh)₄) were synthesized and their photophysical behavior were compared with those of a number of zinc phthalocyanine (ZnPc) derivatives. ZnPc(COOH)(SPh)₃ and ZnPc(SPh)₄ had similar fluorescence (Φ_F=0.14) and triplet state (Φ_T=0.65) quantum yields in dimethylsulfoxide, hence showing no effects of the replacement of one of the phenylthio groups with a carboxylic acid group. ZnPc(COOH)(SPh)₃ displayed a slightly shorter triplet lifetime (τ_T=331 μs) than ZnPc (τ_T=350 μs) in DMSO, but within the range of ZnPc derivatives. The triplet lifetime for ZnPc(COOH)(SPh)₃ is much longer than for the symmetrical derivative (ZnPc(SPh)₄) with τ_T=149 μs in DMSO.     

Reaction of SO2 with Cu/TiO2(1 1 0): Effects of size and metal-oxide interactions in the chemical activation of Cu nanoparticles

The reaction of SO₂ with stoichiometric TiO₂(1 1 0), partially reduced TiO_2 − x(1 1 0) and Cu/TiO₂(1 1 0) was investigated using synchrotron based X-ray photoemission spectroscopy. SO₂ adsorbs on perfect TiO₂(1 1 0) forming SO₄ species at room temperature, while SO₂ dissociatively adsorbs on partially reduced TiO_2 − x(1 1 0) forming SO₄, SO₃ as well as two sulfide species. SO₂ exposure to Cu particles supported on perfect TiO₂(1 1 0) can lead to the formation of SO₄, SO₃ and sulfide species. When depositing Cu on SO₄/TiO₂(1 1 0) at room temperature, the dissociation efficiency of Cu atoms is much higher than that of Cu deposited on TiO₂(1 1 0) prior to SO₂ dosing. The post-deposited Cu atoms can efficiently contact and react with SO₄ species before they form Cu-Cu bonds and big clusters. Small Cu nanoparticles supported on TiO₂(1 1 0) are more reactive towards SO₂ than surfaces of bulk copper. The chemical reactivity of the Cu/TiO₂(1 1 0) system increases with Cu coverage until reaching a maximum at θ_Cu = 0.5-0.8 ML. After this point, an increase in Cu coverage leads to the formation of big Cu particles and the reactivity of the system decrease to that typical of bulk Cu. A comparison with results for SO₂/Cu/MgO(0 0 1) indicates that the effects of size and metal ↔ oxide interactions are important for the chemical activation of Cu nanoparticles on titania.     

Berberine as a natural source inhibitor for mild steel in 1 M H2SO4

Berberine was abstracted from coptis chinensis and its inhibition efficiency on corrosion of mild steel in 1 M H₂SO₄ was investigated through weight loss experiment, electrochemical techniques and scanning electronic microscope (SEM) with energy disperse spectrometer (EDS). The weight loss results showed that berberine is an excellent corrosion inhibitor for mild steel immersed in 1 M H₂SO₄. Potentiodynamic curves suggested that berberine suppressed both cathodic and anodic processes for its concentrations higher than 1.0 × 10⁻⁴ M and mainly cathodic reaction was suppressed for lower concentrations. The Nyquist diagrams of impedance for mild steel in 1 M H₂SO₄ containing berberine with different concentrations showed one capacitive loop, and the polarization resistance increased with the inhibitor concentration rising. A good fit to Flory-Huggins isotherm was obtained between surface coverage degree and inhibitor concentration. The surface morphology and EDS analysis for mild steel specimens in sulfuric acid in the absence and presence of the inhibitor also proved the results obtained by the weight loss and electrochemical experiments. The correlation of inhibition effect and molecular structure of berberine was then discussed by quantum chemistry study.     

High pressure behaviour of KHSO4 studied by electrical impedance spectroscopy

Measurements of the electrical conductivity were performed in KHSO₄ at pressures between 0.5 and 2.5 GPa and in the temperature range 120-350 °C by the use of the impedance spectroscopy. The temperatures of the α-β phase transition (T_Tr) and of the melting (T_m), determined from the Arrhenius plots ln(σT) vs. 1/T, increase with pressure up to 1.5 GPa having dT/dP∼+45 K/GPa. Above the pressure 1.5 GPa, the pressure dependencies of T_Tr and T_m are negative dT/dP∼−45 K/GPa. At pressures above 0.5 GPa, the reversible decomposition of KHSO₄ into K₃H(SO₄)₂+H₂SO₄ (and probably into K₅H₃(SO₄)₄+H₂SO₄) affects the electrical conductivity of KHSO₄, with the typical values of the protonic electrical conductivity, c. 10⁻¹ S/cm at 2.5 GPa.     

Application of ultrasonic wave to clean the surface of the TiO2 nanotubes prepared by the electrochemical anodization

In this study, the TiO₂ nanotubes were fabricated by electrochemical anodization in a NH₄F/Na₂SO₄/PEG400/H₂O electrolyte system. Ultrasonic wave (80 W, 40 kHz) was used to clean the surface of TiO₂ nanotube arrays in the medium of water after the completion of the anodization. Surface morphology (FESEM) and X-ray diffraction spectrum of the nanotubes treated by sonication at 0 min, 9 min, 40 min and 60 min were compared. The experimental results showed that the precipitate on the surface of the nanotube arrays could be removed by the ultrasonic wave. The treating time had an influence on the precipitate removal and 9 min (corresponding to 12 Wh) is the suitable time for surface cleaning of the TiO₂ nanotubes on this experimental condition.     

Long range one-dimensional ordering of lead phthalocyanine monolayer on InSb(1 0 0) (4 × 2)/c(8 × 2)

Sub-monolayer and monolayer of lead phthalocyanine deposited on InSb(1 0 0) (4 × 2)/c(8 × 2) surface have been investigated by scanning tunneling microscopy and low energy electron diffraction. Molecules first adsorb on the indium rows of the (4 × 2)/c(8 × 2) structure in the [1 1 0] direction and diffuse at the surface in order to form two-dimensional islands. The molecule-substrate interaction stabilizes the PbPc molecules on the In rows. It weakens the interaction between molecules located in adjacent rows resulting in numerous gliding planes between the molecular chains, in the direction parallel to the rows. At monolayer completion, a long-range one-dimensional order is adopted by the molecules in the [1 1 0] direction.     

Quantized conductance behavior of Pt metal nanoconstrictions under electrochemical potential control

We studied the quantized conductance behavior of mechanically fabricated Pt nanoconstrictions under electrochemical potential control in H₂SO₄, Na₂SO₄, and NaOH solutions. There was no clear feature in the conductance histogram, when the electrochemical potential of the nanoconstrictions was kept at the double layer or the under potential deposited hydrogen potential. At the hydrogen evolution potential, the conductance histograms showed clear features around 0.5 and 1 G₀ in the H₂SO₄ solution. In Na₂SO₄, and NaOH solutions, a 1 G₀ feature with a shoulder appeared in the histogram. The quantized conductance behavior of Pt nanoconstrictions could be controlled by the electrochemical potential and solution pH.     

Solvent effect in monoclinic to hexagonal phase transformation in LaPO4:RE (RE=Dy, Sm) nanoparticles: Photoluminescence study

Nanosized phosphor materials, LaPO₄:RE (RE=Dy³⁺, Sm³⁺) have been synthesized using water, dimethyl sulfoxide (DMSO), ethylene glycol (EG) and mixed solvents at a relatively low temperature of 150 °C. X-ray diffraction (XRD) study reveals that as-prepared nanoparticles prepared in DMSO and EG are well crystalline and correspond to monoclinic phase. In the mixed water-DMSO or water-EG solvents, XRD patterns are in good agreement with hexagonal phase, but transformed to monoclinic phase at higher temperature of 900 °C. TEM images show well-dispersed and rice-shaped nanoparticles of diameter 5-10 nm, length of 13-37 nm for Dy³⁺-doped LaPO₄ and diameter of 25-35 nm, length of 73-82 nm for Sm³⁺-doped LaPO₄. Dy³⁺-doped LaPO₄ shows two prominent emission peaks at 480 and 572 nm corresponding to ⁴F_9/2→⁶H_15/2 (magnetic dipole) and ⁴F_9/2→⁶H_13/2 (electric dipole) transitions, respectively. Similarly, for Sm³⁺-doped LaPO₄, three prominent emission peaks at 561, 597 and 641 nm were observed corresponding to ⁴G_5/2→⁶H_5/2, ⁴G_5/2→⁶H_7/2 (magnetic dipole) and ⁴G_5/2→⁶H_9/2 (electric dipole) transitions, respectively. The luminescence intensity of the sample prepared in EG is more than that of DMSO or mixed solvents. Enhancement of luminescence is also observed after heat-treatment at 900 °C due to removal of quencher such as water, organic moiety and surface defects/dangling bonds. The samples are re-dispersible in polar solvent and can be incorporated in polymer film.     

Inhibition of iron corrosion in 0.5 M sulphuric acid by metal cations

Corrosion inhibitors are widely used in acid solutions during pickling and descaling. Mostly organic compounds containing N, O, and S groups are employed as inhibitors. In this study, the inhibition performance of metal cations such as Zn²⁺, Mn²⁺ and Ce⁴⁺ ions in the concentration range 1-10 × 10⁻³ M has been found out. The corrosion behaviour of iron in 0.5 M H₂SO₄ in the presence of metal cations is studied using polarization and impedance methods. It is found that the addition of these metal cations inhibits the corrosion markedly. The inhibition effect is in the following order Ce⁴⁺ ? Mn²⁺ > Zn²⁺.