Synthesis,characterization, and photovoltaic properties of diketopyrrolopyrrole-oligothiophene/fullerene dyads

Low-band-gap dyad molecules containing diketopyrrolopyrole (DPP) chromophore and hexathiophene were designed and synthesized in combination with C₆₀ and C₇₀ derivatives as the electron acceptors. The effect of alkyl side chains in the donor parts on film morphology, thermal properties, and optical properties were investigated by X-ray diffraction analysis, differential scanning calorimetry, UV–vis absorption spectroscopy, and fluorescence spectroscopy. The donor part with a shorter alkyl side chain showed better packing of the π-plane and an enhancement of absorption in the longer-wavelength region, which led to higher J_SC of organic solar cells. The use of C₇₀ as the electron acceptor led to stronger absorption in the visible region, resulting in improved external quantum efficiency and J_SC compared with those of the C₆₀ derivatives. The single-component solar cell of the dyad with the methyl side chains and C₇₀ derivative showed the power conversion efficiency of 0.84% with a relatively high J_SC of 4.4 mA cm⁻² under AM 1.5 illumination (100 mW cm⁻²).     

New organic semiconductors for thin-film transistors: Synthesis,characterization, and performance of 4H-indeno[1,2-b]thiophene derivatives

Three new hybrid polycyclic aromatic 4H-indeno[1,2-b]thiophene derivatives (DIT-nT) were readily synthesized and characterized. Ultraviolet photoelectron spectroscopy (UPS) and inverse photoemission spectroscopy (IPES) study shows that the gap energies of these oligothiophene derivatives are dependent on the effective π-conjugation length of the molecules, with decreasing gap energies while the conjugated length is increased. More importantly, the hole injection barrier obtained from UPS and IPES studies decreases significantly at the metal-organic interface as the effective π-conjugation length of the molecules increases. Hence, the hole injection into DIT-2T is expected to be more facile than that into DIT-0T due to the smaller barrier. X-ray diffraction examination revealed that thin films are highly ordered, with the long axes of the molecules nearly perpendicular to the surface. The field-effect transistor (FET) devices based on the three oligomers show good p-type performance with high hole mobilities, and the highest value (0.014 cm² V⁻¹ s⁻¹) was obtained for the longest oligomer DIT-2T.     

Evaluation of some non-toxic thiadiazole derivatives as bronze corrosion inhibitors in aqueous solution

The inhibiting effect of four innoxious thiadiazole derivatives (2-mercapto-5-amino-1,3,4-thiadiazole (MAT), 2-mercapto-5-acetylamino-1,3,4-thiadiazole (MAcAT), 2-mercapto-5-methyl-1,3,4-thiadiazole (MMeT) and 2-mercapto-5-phenylamino-1,3,4-thiadiazole (MPhAT)) on bronze corrosion in an aerated solution of 0.2 g L⁻¹ Na₂SO₄ + 0.2 g L⁻¹ NaHCO₃ at pH 5 was studied by potentiodynamic voltammetry and electrochemical impedance spectroscopy.The corrosion parameters determined from the polarisation curves indicate that the addition of the investigated thiadiazole derivatives decreases both cathodic and anodic current densities, due to an inhibition of the corrosion process, through the adsorption of thiadiazoles on the bronze surface. The inhibiting effect of the investigated organic compounds appears to be more pronounced on the anodic process than on the cathodic one and, except for the case MPhAT, it is enhanced by the increases of the inhibitors’ concentration.The adsorption of the thiadiazole derivatives on bronze was confirmed by the presence of the nitrogen atoms in the EDX spectra of the bronze exposed to inhibitor-containing solutions.The magnitude of polarisation resistance values and, consequently, the inhibition efficiencies are influenced by the molecular structure of thiadiazole derivatives. The strongest inhibition was noticed in the presence of compounds with phenyl amino- or amino-functionalities in their molecules. The maximum protection efficiencies were obtained by addition of: 5 mM MAT (95.9%), 1 mM MAcAT (95.7%), 5 mM MMeT (92.6%) and 0.1 mM MPhAT (97%). EIS measurements also revealed that the inhibitor effectiveness of the optimal concentrations of thiadiazole is time-dependent.     

Two-dimensional organic metals θ-(BETS)4MBr4(PhBr), M = Cd,Hg with differently oriented conducting layers

New bis(ethylenedithio)tetraselenafulvalene (BETS) based radical cation salts with tetrahedral dianions [CdBr₄]²⁻ and [HgBr₄]²⁻ of the (BETS)₄MBr₄(PhBr) composition were prepared by electrochemical crystallization. Room-temperature crystal structure of (BETS)₄CdBr₄(PhBr) determined by single crystal X-ray diffraction involves BETS radical cation layers of the θ-type packing and insulating layers consisting of [CdBr₄]²⁻ anions and PhBr molecules. In the neighboring conducting layers, the stacks are arranged perpendicular to each other. A metal-to-metal transition within 225–230 K range was found in both (BETS)₄CdBr₄(PhBr) and (BETS)₄HgBr₄(PhBr). The behavior of electrical resistivity of these salts differs substantially along and across conducting layers. The study of magnetoresistance of (BETS)₄HgBr₄(PhBr) revealed weak Shubnikov-de Haas oscillations in fields higher than 6 T.     

Phenoxazine and N-phenyl-1-naphtylamine-based enamines as hole-transporting glass-forming materials

New aromatic enamines were synthesized by condensation of the commercially available phenoxazine and N-phenyl-1-naphtylamine with 2,2-diphenylacetaldehyde or 2-phenylpropionaldehyde. The materials were examined by various techniques including differential scanning calorimetry, UV and fluorescence spectrometry, electron photoemission and time of flight techniques. The electron photoemission spectra of the layers of the amorphous materials showed the ionization potentials of 5.42–5.61 eV. Hole drift mobilities in the layers of 33–50% solid solutions of the derivatives in bisphenol Z polycarbonate range from 10⁻⁵ to 3.4 × 10⁻⁴ cm²/V s at high electric fields.     

Fine tuning the HOMO energy levels of polythieno[3,4-b]thiophene derivatives by incorporation of thiophene-3,4-dicarboxylate moiety for photovoltaic applications

To lower the HOMO (highest occupied molecular orbital) energy level of polythieno[3,4-b]thiophene (∼−4.5 eV), a series of ester-functionalized polythieno[3,4-b]thiophene derivatives (P1–P3) were designed and synthesized by Stille cross coupling reaction. The resulting copolymers exhibited broad and strong absorption bands from visible to near infrared region with low optical band gaps of 1.23–1.42 eV. Through cyclic voltammetry measurements, it was found that the HOMO energy levels of the copolymers gradually decreased with increasing the content of the thiophene-3,4-dicarboxylate moiety, i.e. −4.91 eV for P1, −5.00 eV for P2, and −5.11 eV for P3. Preliminary photovoltaic properties of the copolymers blended with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as electron acceptor were investigated. Among the three copolymers, P1 exhibited the best photovoltaic performance with an open circuit voltage (V_oc) of 0.54 V, a short circuit current density (I_sc) of 3.3 mA/cm², a fill factor (FF) of 0.57, and a power conversion efficiency (PCE) of 1.02%. A high V_oc up to 0.71 V was achieved in the solar cell based on a P3:PCBM blend.     

Characterisation of mackinawite by Raman spectroscopy: Effects of crystallisation, drying and oxidation

Iron(II) sulphides were precipitated by mixing FeCl₂ · 4H₂O (or FeSO₄ · 7H₂O) and Na₂S aqueous solutions with various [Fe(II)]/[S(-II)] concentration ratios at [Fe(II)] = 0.1 mol L⁻¹. They were analysed by micro-Raman spectroscopy and X-ray diffraction immediately after precipitation and after various times of ageing in suspension at room temperature. In any case, the initial precipitate was nanocrystalline mackinawite. Its Raman spectrum is made of two sharp peaks at 208 ± 1 and 282 ± 1 cm⁻¹. For [Fe(II)]/[S(-II)] ? 1, ageing of the precipitate led to crystalline mackinawite, as testified by X-ray diffraction. The Raman spectrum of crystalline Fe(II) mackinawite shows three main peaks at 208, 256 and 298 cm⁻¹. Drying of nanocrystalline mackinawite under an argon flow favoured crystallisation. The removal of interparticle and surface adsorbed water molecules led to coalescence of the nanoparticles and increase of the size of the domains of coherent scattering. For [Fe(II)]/[S(-II)] = 1/2, the precipitate still consisted of nanocrystalline mackinawite after 70 days of ageing. Finally, the early oxidation stages of mackinawite led to the formation of Fe(III) cations inside the tetrahedral sites of the crystal structure. The most oxidised form of Fe(III)-containing mackinawite is characterised by a Raman spectrum with sharp peaks at 125, 175, 256, 312 and 322 cm⁻¹, and a large vibration band at 350-355 cm⁻¹ that may be attributed to stretching modes of Fe(III)-S tetrahedrons. Analyses of the rust layers of a roman ingot that remained 20 centuries in the Mediterranean Sea revealed the presence of iron sulphides, more likely generated by sulphate-reducing bacteria. Micro-Raman analyses demonstrated the presence of nanocrystalline mackinawite and Fe(III)-containing mackinawite.     

Study of post annealing influence on structural, chemical and electrical properties of ZTO thin films

Zinc-Tin-Oxide (ZTO) thin films were deposited on glass substrate with varying concentrations (ZnO:SnO₂; 100:0, 90:10, 70:30 and 50:50 wt.%) at room temperature by flash evaporation technique. These deposited ZTO films were annealed at 450 °C in vacuum. These films were characterized to study the effect of annealing and addition of SnO₂ concentration on the structural, chemical and electrical properties. The XRD analysis indicates that crystallization of the ZTO films strongly depends on the concentration of SnO₂ and post annealing where annealed films showed polycrystalline nature. Atomic force microscopy (AFM) images manifest the surface morphology of these ZTO thin films. The XPS core level spectra of Zn(2p), O(1s) and Sn(3d) have been deconvoluted into their Gaussian component to evaluate the chemical changes, while valence band spectra reveal the electronic structures of these films. A small shift in Zn(2p) and Sn(3d) core level towards higher binding energy and O(1s) core level towards lower binding energy have been observed. The minimum electrical resistivity (ρ ≈ 3.69 × 10⁻² Ω-cm), maximum carrier concentration (n ≈ 3.26 × 10¹⁹ cm⁻³) and Hall mobility (μ ≈ 5.2 cm² v⁻¹ s⁻¹) were obtained for as-prepared ZTO (50:50) film thereafter move towards lowest resistivity (ρ ≈ 1.12 × 10⁻³ Ω-cm), highest carrier concentration (n ≈ 2.96 × 10²⁰ cm⁻³) and mobility (μ ≈ 18.8 cm² v⁻¹ s⁻¹) for annealed ZTO (50:50) thin film.     

Long-term corrosion of rebars embedded in aerial and hydraulic binders - Mechanisms and crucial physico-chemical parameters

The prediction of long-term behaviour of reinforced concrete structures involved in the nuclear industry requires the comprehension of the mechanism involved in long-term corrosion. Yet, studies on archeological artefacts allowed to identify a typical layout constituted of four layers: the metal, the dense product layer (DPL), the transformed medium (TM) and the binder. Oxygen reaction sites were labelled using oxygen 18 (¹⁸O) and it was evidenced that the cathodic sites are located at the metal/dense product layer interface. So, oxygen has to crossed the DPL to react at the M/DPL interface or inside the marblings, and measurements of the effective tritiated water (2.6 ± 0.1 × 10⁻¹¹ m²/s) and iodide (1.0 ± 0.3 × 10⁻¹¹ m²/s) diffusivity of this layer saturated with water were made. Indeed, these two molecules have a diffusivity in water very closed to oxygen diffusivity.     

Preparation of large scale photocatalytic TiO2 films by the sol-gel process

Nanocrystalline titanium dioxide films were formed on frosted and clear borosilicate glass with a large surface area (12 × 22 cm) using doctor blade and spray coating techniques. The films were subjected to a high temperature treatment at 550 °C. X-ray diffraction (XRD) analysis indicated that the TiO₂ films contain only the anatase phase. Optical microscopy was used to determine the morphology changes after the deposition of each layer. Scanning electron microscopy (SEM) was used to study the films surface morphology. The large scale TiO₂ films produced showed a high photocatalytic activity which was evaluated by the degradation of methyl orange (MO) in aqueous solution (10 mg L^− 1) under illumination of a UV light source with an overall irradiance of 0.9 mW cm^− 2. UV-visible spectrophotometry was used to monitor the degradation of MO through the decrease of the main absorbance peak at 464 nm. The results demonstrated that a complete decomposition of MO could be achieved after 2 h of UV irradiation.     

Carbazole-containing enamines as charge transport materials for electrophotography

Synthesis and thermal, optical as well as photoelectrical properties of carbazole-based enamines are reported. The synthesized compounds were found to form glasses with the glass transition temperatures up to 104 °C as characterized by differential scanning calorimetry. Electron photoemission spectra of the synthesized enamines have been recorded and the ionization potentials have been established. The lowest value of ionization potential (5.22 eV) and the best charge transport properties were shown by di(2,2-diphenylvinyl)(9-ethyl-3-carbazolyl)amine. Room temperature hole-drift mobilities in its 50% solid solutions in bisphenol Z polycarbonate established by the xerographic time-of-flight technique were found to be 9 × 10⁻⁵ cm² V⁻¹ s⁻¹ at electric field of 10⁶ V cm⁻¹.     

Composition and protective ability of rust layer formed on weathering steel exposed to various environments

The compositional change of rust (corrosion products) layer formed on weathering steel exposed to atmosphere with different amount of air-borne sea salt particles in Japan have been investigated by the X-ray diffraction method. The mass ratio (α/γ) of crystalline α-FeOOH to γ-FeOOH, in the rust layer formed on the weathering steel exposed in an industrial environment, increases with an increase in exposure duration. The α/γ is closely related to the corrosion rate in environments when the amount of air-borne salt is less than 0.2 mg NaCl/dm²/day (2.31 × 10⁻⁷ g NaCl/m²/s). However this is not the case in seaside environments with a higher amount of air-borne salts. The mass ratio (α/γ^∗) of crystalline α-FeOOH to the total mass of γ-FeOOH, β-FeOOH and Fe₃O₄, in the rust layer formed on the weathering steel is related to the corrosion rate even in seaside environments certainly more than 0.2 mg/dm²/day (2.31 × 10⁻⁷ g/m²/s) of air-borne salt particles. When the α/γ^∗ is more than 1, a higher corrosion rate more than 0.01 mm/year (3.17 × 10⁻¹³ m/s) is not observed. The α/γ^∗ is a protective ability index of rust formed on weathering steel.     

Capacitive properties of RuO2 and Ru–Co mixed oxide deposited on single-walled carbon nanotubes for high-performance supercapacitors

Composite electrodes for use in redox supercapacitors were prepared by electrochemical deposition of RuO₂ or the co-deposition of Ru–Co mixed oxides on the surface of single-walled carbon nanotubes. Electrodes coated with the Ru–Co mixed oxide [Ru (13.13 wt%) and Co (2.89 wt%)] or RuO₂, exhibited a similar specific capacitance (∼620 F g⁻¹) at low potential scan rates (10 mV s⁻¹). However, at higher scan rates (500 mV s⁻¹) the mixed metal oxide electrode showed superior performance (570 F g⁻¹) when compared to the RuO₂ electrode (475 F g⁻¹). This increase in capacitance at high scan rates is attributed to the role of the Co in providing enhanced electronic conduction.     

Effect of underpotential deposition of lead on polarization behavior of nickel in acidic perchlorate solutions at room temperature

The effect of Pb²⁺ on polarization behavior of nickel has been investigated in 0.1 M NaClO₄ + 10⁻² M HClO₄ + x M PbO solutions (x = 0, 10⁻⁵, 10⁻⁴, 10⁻³) at room temperature. The cyclic voltammogram has suggested that Pb²⁺ degrades the stability of the passive film on Ni. The corrosion potential of Ni shifted to the more noble direction and the anodic current peak of Ni dissolution decreased with increasing Pb²⁺ concentration in solution, indicating that Pb²⁺ suppresses significantly the anodic dissolution. The underpotential deposition (UPD) of lead on Ni in the potential range more noble than −0.215 V (SHE) corresponding to the equilibrium potential of the Pb²⁺ (10⁻³ M)/Pb electrode was confirmed by XPS and GDOES analyses. The anodic Tafel slope, b⁺, of Ni dissolution changed from b⁺ = 40 mV decade⁻¹ in the absence of Pb²⁺ to b⁺ = 17 mV decade⁻¹ in the presence of 10⁻⁴ or 10⁻³ M Pb²⁺, which was ascribed to the increase in active sites of Ni surface emerged as a result of electrodesorption of Pb adatoms. The roles of Pb adatoms in active dissolution and active/passive transition of Ni were discussed from the above results.     

Modification of graphite oxide nanoparticles prepared via electrochemically oxidizing method

Graphite oxide nanoparticles (GONPs), prepared via electrochemically oxidizing technique, were chemically reduced by hydrazine hydrate in water medium. The electrical conductivity of the samples showed an improvement by three orders of magnitude from 1.38 × 10⁻⁶ s cm⁻¹ (before reduction) to 1.02 × 10⁻³ s cm⁻¹ (after reduction). UV–vis measurement was used to explained the restoration of the conducting conjugated networks in graphite nanoparticles. The hydrophilic GONPs or their reduced samples could be further organically modified, using cetyltrimethylammoniumbromide (CTAB) as a modifier, turned to a hydrophobic nanoparticles which could form homogeneous and stable dispersion in toluene, and other organic media.     

Metal release from various grades of stainless steel exposed to synthetic body fluids

Release rates of individual alloy constituents have been determined from seven grades of stainless steels exposed to two synthetic body fluids, used as surrogates for different areas of potential exposure in the lung: “Gamble’s solution”, (pH 7.4) that represents the interstitial fluid of the deep lung, and artificial lysosomal fluid (ALF) that represents the more acidic (pH 4.5-5) milieu of particles following their phagocytosis by macrophages. Total metal release rates from all grades of stainless steel investigated were low (<5 μg cm⁻² week⁻¹). The more acidic environment of ALF resulted in significantly higher total metal release rates (0.3-4.6 μg cm⁻² week⁻¹) compared to Gamble’s solution (<0.1 μg cm⁻² week⁻¹).     

Electrochemical pitting corrosion behaviour of α-brass in LiBr containing solutions

The potentiodynamic anodic polarization curve of α-brass (70% Cu-30% Zn) in 1 M LiBr solution showed an initial active region of the alloy dissolution followed by two well defined anodic current peaks then a narrow passivation region before the pitting potential (E_pit) is reached. The initial active anodic region exhibited Tafel slope with 90 mV dec⁻¹ attributed to the formation of CuBr₂⁻ complexes. The anodic current peaks were attributed to the formation of CuBr and Cu²⁺ ions, respectively. The change of pH values of LiBr solution did not affect the anodic polarization curves of α-brass. Increasing the solution temperature from 30 to 90 °C changed the corrosion type from pitting to general one. The addition of 10⁻² M benzotriazole (BTAH) to 1 M LiBr solution is completely inhibited the pitting corrosion at 30 °C while it did not inhibit the pitting at 90 °C. The inhibition effect was attributed to the adsorption of BTAH molecules on the alloy surface, which obeys Langmuir isotherm. The presence or absence of pitting corrosion was confirmed by using SEM.     

Ink-jet printing of organic semiconductor for fabricating organic thin-film transistors: Film uniformity control by ink composition

We have investigated the influence of solvent chemistry on ink-jet printed semiconductor patterns. Our research focuses on improving the uniformity of an ink-jet printed single dot semiconductor by adjusting the solvent mixture combination. Use of a solvent mixture with one solvent of a lower boiling point and a higher solubility with respect to the semiconductor molecules and another of a higher boiling point and a lower solubility allows us to produce a uniform single dot pattern by ink-jet printing. It was observed that the film uniformity of the semiconductor layer plays an important role in determining the electrical parameters of the transistor. In comparison with uncontrolled ink composition, the OTFT fabricated from the well-controlled ink exhibited better device performance, including a carrier mobility of 8.5 × 10⁻³ cm² V⁻¹ s⁻¹ in the saturation regime, an on/off current ratio of 10³, and a threshold voltage of 0.39 V with subthreshold slopes of 0.95 V dec⁻¹.     

Influence of flow on the corrosion inhibition of carbon steel by fatty amines in association with phosphonocarboxylic acid salts

This work was carried out to study the inhibition mechanism of a carbon steel in a 200 mg l⁻¹ NaCl solution by a non-toxic multi-component inhibitor used for water treatment in cooling circuits. The inhibitive formulation was composed of 50 mg l⁻¹ fatty amines associated with 200 mg l⁻¹ phosphonocarboxylic acid salts. Steady-state current-voltage curves, obtained with a rotating disc electrode, revealed that the properties of the protective layer were dependent on the electrode rotation rate and on the immersion time. The cathodic process of oxygen reduction was not modified in the presence of the inhibitive mixture. As expected, the current densities increased when the rotation rate was increased. In the anodic range, original behaviour was observed: the current densities decreased when the electrode rotation rate increased. The morphology and the chemical composition of the inhibitive layers allowed the electrochemical results to be explained. Two distinct surface areas were visualised on the metal surface and the ratio between the two zones was dependent on the flow conditions. This behaviour was attributed to a mechanical effect linked to centrifugal force. XPS analysis revealed that the formation of a chelate between the phosphonocarboxylic acid salt molecules and the iron oxide/hydroxide was enhanced by the increase of the electrode rotation rate.