Octanethiolated Cu and Cu2O nanoparticles as ink to form metallic copper film

The synthesis and spectroscopic characterizations of size-controlled Cu and Cu₂O nanoparticles forming self-assembled 2D superlattices with hexagonal packing are described. The scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) were used to characterize the octanethiol-protected copper nanoparticles. Analysis of XPS confirms the formation of oxidized copper nanoparticles. Conductivity of copper metal film (0.1 μm) on the Si wafer can be improved simply by thermal annealing of copper monolayer protected clusters (MPCs) film (4.8 ± 0.5 × 10² μΩ cm) under air at 300 °C for 1 h, and then for another 5 h under a protective atmosphere of 90% N₂-10% H₂.     

Shape and size transformation of gold nanorods (GNRs) via oxidation process: A reverse growth mechanism

The anisotropic shape transformation of gold nanorods (GNRs) with H₂O₂ was observed in the presence of “cethyl trimethylammonium bromide” (CTAB). The adequate oxidative dissolution of GNR is provided by the following autocatalytic scheme with H₂O₂: Au⁰ → Au⁺, Au⁰ + Auⁿ⁺ → 2Au³⁺, n = 1 and 3. The shape transformation of the GNRs was investigated by UV-vis spectroscopy and transmission electron microscopy (TEM). As-synthesised GNRs exhibit transverse plasmon band (TPB) at 523 nm and longitudinal plasmon band (LPB) at 731 nm. Upon H₂O₂ oxidation, the LPB showed a systematic hypsochromic (blue) shift, while TPB stays at ca. 523 nm. In addition, a new emerging peak observed at ca. 390 nm due to Au(III)-CTAB complex formation during the oxidation. TEM analysis of as-synthesised GNRs with H₂O₂ confirmed the shape transformation to spherical particles with 10 nm size in 2 h, whereas centrifuged nanorod solution showed no changes in the aspect ratio under the same condition. Au³⁺ ions produced from oxidation, complex with excess free CTAB and approach the nanorods preferentially at the end, leading to spatially directed oxidation. This work provides some information to the crystal stability and the growth mechanism of GNRs, as both growth and shortening reactions occur preferentially at the edge of single-crystalline GNRs, all directed by Br⁻ ions.     

Comparative study of electrochemical capacitance of multi-walled carbon nanotubes before and after chopping

In the work, short multi-walled carbon nanotubes (S-CNTs) were synthesized by chopping conventional μm-long multi-walled carbon nanotubes (L-CNTs) under ultrasonication in H₂SO₄/HNO₃ mixed acids. A comparative electrochemical investigation performed in 6 M KOH solution demonstrated that a specific capacitance (SC) of ca. 14.6 μF cm⁻² was delivered by the S-CNTs with the specific surface area (SSA) of 207 m² g⁻¹, much larger than that of ca. 10.1 μF cm⁻² for the L-CNTs with the SSA of 223 m² g⁻¹, the reason for which was that S-CNTs with two open ends, due to good ion penetrability, provided more entrances for electrolyte ions to access the inner surface easily through their shorter inner pathway so as to enhance their SSA utilization and geometric SC. The surface structure disruption of S-CNTs, owing to ultrasonication and oxidation during chopping process, deteriorated their electronic conductivity and resulted in an inferior power property in contrast to L-CNTs.     

Micromechanical and thermal behaviour of gel grown pure- and sodium-modified copper tartrate crystals

Results regarding micromechanical characteristics of gel grown pure- and sodium-modified copper tartrate crystals, bearing composition CuC₄H₄O₆·3H₂O, (Cu)_0.77(Na)_0.23C₄H₄O₆·3H₂O and (Cu)_0.65(Na)_0.35C₄H₄O₆·H₂O, as obtained on using indentation induced hardness testing technique are reported. Thermal behaviour of these crystals in the temperature ranging from room temperature (∼25 °C) to about 600 °C is also reported. Pure copper tartrate crystals are found to be thermally more stable than the sodium-modified ones. Dependence of Vickers’ hardness number H_v on load ranging from 0.049 to 2.94 N on two different planes for all the three compositions is analyzed. It is shown that after initial rise in the value of H_v, the same achieves saturation at a load of 0.49 N. Modification of copper tartrate crystal by introducing sodium in its lattice brings about a change in the micromechanical characteristics. The saturation value of H_v decreases with increase in the concentration of sodium ions. The results on (0 0 1) and (1 1 1) planes for both pure and modified copper tartrate crystals suggest hardness anisotropy. Relative difference of hardness between the two planes and yield strength for both pure and modified copper tartrate crystals is worked out. The experimental results are analyzed for applicability of Meyer’s law and Proportional Specimen Resistance Model. It is suggested that the experimental results indicating reverse ISE phenomenon may be explained in terms of the existence of a distorted zone near the crystal-medium interface. The integral method of Coats and Redfern approximation applied to the thermoanalytical data suggests “Random Nucleation Model” for the reaction kinetics of these crystals. Non-isothermal kinetic parameters such as activation energy, frequency factor and order of reaction are calculated.     

Influence of cetyltrimethylammonium bromide on the morphology of AWO4 (A = Ca, Sr) prepared by cyclic microwave irradiation

AWO₄ (A = Ca, Sr) was prepared from metal salts [Ca(NO₃)₂·4H₂O or Sr(NO₃)₂], Na₂WO₄·2H₂O and different moles of cetyltrimethylammonium bromide (CTAB) in water by cyclic microwave irradiation. The structure of AWO₄ was characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the presence of nanoparticles in clusters with different morphologies; spheres, peaches with notches, dumb-bells and bundles, influenced by CTAB. Six Raman vibrational peaks of scheelite structure were detected at 908, 835, 793, 399, 332 and 210 cm⁻¹ for CaWO₄ and 917, 833, 795, 372, 336 and 192 cm⁻¹ for SrWO₄, which are assigned as ν₁(A_g), ν₃(B_g), ν₃(E_g), ν₄(B_g), ν₂(A_g) and ν_f.r.(A_g), respectively. Fourier transform infrared (FTIR) spectra provided the evidence of W-O stretching vibration in [WO₄]²⁻ tetrahedrons at 793 cm⁻¹ for CaWO₄ and 807 cm⁻¹ for SrWO₄. The peaks of photoluminescence (PL) spectra were at 428-434 nm for CaWO₄, and 447-451 nm for SrWO₄.     

Preparation of superhydrophobic films on titanium as effective corrosion barriers

Stable superhydrophobic films were prepared on the electrochemical oxidized titania/titanium substrate by a simple immersion technique into a methanol solution of hydrolyzed 1H,1H,2H,2H-perfluorooctyltriethoxysilane [CF₃(CF₂)₅(CH₂)₂Si(OCH₂CH₃)₃, PTES] for 1 h at room temperature followed by a short annealing at 140 °C in air for 1 h. The surface morphologies and chemical composition of the film were characterized by means of water contact angle (CA), field emission scanning electron microscopy (FESEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The water contact angle on the surface of this film was measured to be as high as 160°. SEM images showed that the resulting surfaces exhibited special hierarchical structure. The special hierarchical structure along with the low surface energy leads to the high surface superhydrophobicity. The corrosion resistance ability and durance property of the superhydrophobic film in 3.5 wt.% NaCl solution was evaluated by the electrochemical impedance spectroscopy (EIS). The anticorrosion properties of the superhydrophobic film are compared to those of unmodified pure titanium and titania/titanium substrates. The results showed that the superhydrophobic film provides an effective corrosion resistant coating for the titanium metal even with immersion periods up to 90 d in the 3.5 wt.% NaCl solution, pointing to promising future applications.     

High-precision frequency measurements of the ν1 + ν3 combination band of C2H2 in the 1.5 μm region

A pair of 1.5 μm semiconductor laser frequency standards have been developed for optical telecommunications use, stabilised to transitions of ¹²C₂H₂ and ¹³C₂H₂, using cavity-enhanced Doppler-free saturation absorption spectroscopy. The absolute frequencies of 41 lines of the ν₁ + ν₃ band of ¹²C₂H₂, covering the spectral region 1520-1545 nm, have been measured by use of a passive optical frequency comb generator, referenced to ¹³C₂H₂ transitions of known frequency. The mean experimental uncertainties (coverage factor k = 1) of the frequency values are 3.0 kHz (type A) and 10 kHz (type B). Improved values of the band origin ν₀, rotational constants B′ and B″, and centrifugal distortion coefficients D′, D″, H′, and H″ are presented.     

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.     

A novel precursor for synthesis of metallic copper nanocrystals by thermal decomposition approach

[Bis(2-hydroxy-1-naphthaldehydato)copper(II)] complex, as a novel precursor, was employed in thermal decomposition process to synthesize metallic copper nanoparticles using oleylamine (C₁₈H₃₇N) as capping agent. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV-vis) spectroscopy. The synthesized copper nanoparticles have a fcc structure with average size 20-35 nm.     

Preparation and characterization of SrSnO3 nanorods

Perovskite strontium stannate (SrSnO₃) nanorods were prepared by annealing the precursor SnSr(OH)₆ nanorods at 600 °C for 3 h. The precursor nanorods were hydrothermally synthesized at 160 °C for 16 h using Sr(NO₃)₂ and SnCl₄·5H₂O as starting materials in the presence of surfactant cetyltrimethyl ammonium bromide (CTAB). As-prepared samples were characterized by X-ray diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and infrared ray spectroscopy (IR). The results show that the as-synthesized powders are made of SrSnO₃ one-dimensional nanorods of about 0.2-1 μm length and 100-150 nm diameter. Possible formation mechanism of SrSnO₃ with nanorod structure under certain conditions was preliminarily analyzed, in which it was thought that CTAB played an important role in the formation process of the nanorod structure. Electrochemical performance of the samples versus Li metal was also evaluated for possible use in lithium-ion batteries.     

Conformational order of n-dodecanethiol and n-dodecaneselenol monolayers on polycrystalline copper investigated by PM-IRRAS and SFG spectroscopy

Self-assembled monolayers (SAMs) of n-dodecanethiol (C₁₂H₂₅SH) and n-dodecaneselenol (C₁₂H₂₅SeH) on polycrystalline copper have been elaborated with the purpose of achieving densely packed and crystalline-like assemblies. By combining the surface sensitivity of polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation spectroscopy (SFG), the effect of the self-assembly time (15 min, 30 min, 1 h, 2 h and 24 h) on the formation of n-dodecanethiol and n-dodecaneselenol monolayers on untreated and electrochemically reduced polycrystalline copper has been investigated. On electrochemically reduced copper, PM-IRRAS spectroscopy shows that both molecules are able to form well organized layers. SFG spectroscopy indicates that the C₁₂H₂₅SeH SAMs are slightly better ordered than those achieved with C₁₂H₂₅SH. On untreated copper, the two molecules lead to different film organizations. Both PM-IRRAS and SFG indicate that C₁₂H₂₅SH SAMs are of the same film quality as those obtained on electrochemically reduced copper. On the contrary, C₁₂H₂₅SeH monolayers are invariably poorly organized at the molecular level.     

Intrinsic coercivities of molecular beam epitaxy grown single-crystal Ni films on Ag buffer layer

Single-crystal Ni films were made by the molecular beam epitaxy (MBE) method on Si(1 0 0) and Si(1 1 0) substrates, respectively, with an 100 Å thick Ag buffer layer. The growth temperature T_S was 270 °C, and the film thickness t was 500 Å. From reflection high-energy electron diffraction (RHEED) patterns, the crystalline symmetries of the two films are clear and as expected. Intrinsic coercivities, H_C(1 0 0) and H_C(1 1 0), are plotted as a function of the angle of rotation ? around the crystal axes [1 0 0] and [1 1 0], respectively. The results show that both H_C(1 0 0) and H_C(1 1 0) exhibit mixed features of the crystalline (K_C) and the induced uniaxial magnetic (K_u) anisotropies. K_u is the magneto-elastic energy, due to lattice mismatch at the Ni/Ag interface. Moreover, the crystalline anisotropy fields, H_K(1 0 0) and H_K(1 1 0), and the induced anisotropy filed, H_u, can be calculated as a function of ?, respectively. Then, each H_C curve is fitted by the equation: H_C = H_o + H_K + H_u, where H_o is the isotropic pinning field. Meanwhile, domain structures were examined by the Bitter method, using Ferrofluid 707. On the Ni(1 0 0) film, we observed the charged cross-tie walls, and on the Ni(1 1 0) film, the un-charged Bloch walls.     

High sensitivity ICLAS of H2O in the 12,580-13,550 cm transparency window

High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of H₂¹⁸O between 12,580 and 13,550 cm⁻¹. This spectral region covers the 3v+δ polyad of very weak absorption. Four isotopologues of water (H₂¹⁸O, H₂¹⁶O, H₂¹⁷O, HD¹⁸O) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to H₂¹⁸O, while only 160 H₂¹⁸O lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of H₂¹⁸O are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of H₂¹⁸O: (2 4 0), (1 4 1), (0 4 2) and (2 3 1) at 13,167.718, 13,212.678, 13,403.71 and 15,073.975 cm⁻¹, respectively. H₂¹⁸O transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1), (1 7 0), (0 9 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of H₂¹⁷O, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of HD¹⁸O at 13,245.497 cm⁻¹ is also reported for the first time.     

Formation and characterization of conductive thin layers of copper sulfide (CuxS) on the surface of polyethylene and polyamide by the use of higher polythionic acids

Layers of copper sulfide of varying composition and properties are formed on the surface of polyethylene and polyamide by a sorption-diffusion method using solutions of higher polythionic acids, H₂S_nO₆. The concentration of sulfur adsorbed-diffused into PE and PA depends on the degree of the acid sulfurity, n, the temperature of the solution and the period of the polymer treatment. The amount of copper in a sulfide (Cu_xS) layer formed after the sulfured polymer treatment with a solution of Cu(I-II) salt is strongly dependent on the concentration of sulfur in the PE and PA. By the chemical analysis of the obtained sulfide layers was determined that a value of x in the Cu_xS layers varies in the interval 1 < x < 2. The microscopic investigation of transverse sections of PE and PA samples with copper sulfide layers showed that the major part of copper sulfide is in the surface matrix of the polymer. X-ray diffraction studies of the Cu_xS layers obtained seven phases: with x = 2 (chalcocite), 1.9375 (djurleite), 1.8 (digenite), 1.75 (anilite), 1.12 (yarrowite), 1.06 (talnakhite) and 1 (covellite). The measurements of the electrical conductance of Cu_xS layers (0.1-4 S cm⁻²) showed that its value greatly depends on the conditions of PE and PA interaction with H₂S_nO₆ and of further interaction with Cu(I-II) salt solution, on the chemical and phase composition of the layer.     

Novel synthesis and electrophoretic response of low density TiO-TiO2-carbon black composite

Novel low density TiO-TiO₂-carbon black composite was synthesized, which involved the deposition of inorganic coating on the surface of core-shell latex particles and subsequent removal of latex particles by calcination in high-purity nitrogen. The morphology and interior structure were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The images exhibited the composite had spherical shape and smooth surface, and the interior structure was hollow or porous. X-ray diffraction peaks (XRD) were mostly in agreement with the standard diffraction patterns of rutile TiO₂. In addition, the observed peaks at 2θ of 43.5°, 50.6° and 74.4° can be indexed to (1 1 1), (2 0 0) and (2 2 0) planes of cubic phase TiO. The X-ray photoelectron spectroscopy (XPS) results indicated that composite consisted of carbon black, TiO and TiO₂. The apparent density of the composite was suitable to 1.62 g cm⁻³, due to density matching with suspending media. Glutin-arabic gum microcapsules containing TiO-TiO₂-carbon black composite electrophoretic liquid were prepared via complex coacervation. The particles in the microcapsules showed excellent electrophoretic mobility under a DC field.     

Chemical synthesis of p-type nanocrystalline copper selenide thin films for heterojunction solar cells

Nanocrystalline thin films of copper selenide have been grown on glass and tin doped-indium oxide substrates using chemical method. At ambient temperature, golden films have been synthesized and annealed at 200 °C for 1 h and were examined for their structural, surface morphological and optical properties by means of X-ray diffraction (XRD), scanning electron microscopy and UV-vis spectrophotometry techniques, respectively. Cu_2−xSe phase was confirmed by XRD pattern and spherical grains of 30 ± 4 - 40 ± 4 nm in size aggregated over about 130 ± 10 nm islands were seen by SEM images. Effect of annealing on crystallinity improvement, band edge shift and photoelectrochemical performance (under 80 mW/cm² light intensity and in lithium iodide electrolyte) has been studied and reported. Observed p-type electrical conductivity in copper selenide thin films make it a suitable candidate for heterojunction solar cells.     

Growth,structure and optical properties of an efficient NLO crystal-aqua maleatocopper(II)

A promising non-linear optical (NLO) crystal, aqua maleatocopper(II) (CuC₄H₂O₄·H₂O), was grown at room temperature by the controlled ionic diffusion technique. Fourier transform infrared spectrum could identify the various functional groups in the crystal. Structural analysis using single crystal XRD revealed that the compound crystallizes in the monoclinic system with space group P2₁ and unit cell parameters a = 7.7277(5) Å, b = 5.2967(3) Å, c = 7.7179(4) Å, α = γ = 109.170(5)°, β = 111.995(2)°. The thermal stability and decomposition pattern of the material were explored using thermogravimetry (TG) and differential thermal analysis (DTA). The optical band gap energy of the material was estimated as 2.2 eV from the diffuse reflectance spectroscopy. The Kurtz and Perry powder technique established the crystal to be an efficient non-linear optical (NLO) material.     

Spectroscopic study on the interaction of Bacillus subtilis α-amylase with cetyltrimethylammonium bromide

The interaction between α‐amylase from Bacillus subtilis and cetyltrimethylammonium bromide (CTAB) has been investigated at various temperature conditions using fluorescence and circular dichroism (CD) spectroscopic methods. Fluorescence data revealed that the fluorescence quenching of α‐amylase by CTAB is the result of complex formation between CTAB and α‐amylase. The thermodynamic analysis on the binding interaction data shows that the interactions are strongly exothermic (ΔH°=−17.92 kJ mol⁻¹) accompanied with increase in entropy (ΔS° between 109 to 135 J mol⁻¹ K⁻¹). Thus the binding of CTAB to α-amylase is both enthalpic and entropic driven, which represent the predominate role of both electrostatic and hydrophobic interactions in complex formation process. The values of 2.17×10⁻³ M⁻¹ and 1.30 have been obtained from associative binding constant (K_a) and stoichiometry of binding number (n), from analysis of fluorescence data, respectively. Circular dichroism spectra showed the substantial conformational changes in secondary structure of α‐amylase due to binding of CTAB, which represents the complete destruction of both secondary and tertiary structure of α-amylase by CTAB.     

Study of surface interactions of ionic liquids with aluminium alloys in corrosion and erosion-corrosion processes

Surface interactions of alkylimidazolium ionic liquids (ILs) with aluminium alloy Al 2011 have been studied by immersion tests in seven neat ILs [1-n-alkyl-3-methylimidazolium X⁻ (X = BF₄; n = 2 (IL1), 6 (IL2), 8 (IL3). X = CF₃SO₃; n = 2 (IL4). X = (4-CH₃C₆H₄SO₃); n = 2 (IL5). X = PF₆; n = 6 (IL6)] and 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide (IL7)]. Immersion tests for Al 2011 have also been carried out in 1 wt.% and 5 wt.% solutions of 1-ethyl,3-methylimidazolium tetrafluoroborate (IL1) in water. No corrosion of Al 2011 by neat ILs is observed. The highest corrosion rate for Al 2011 in water is observed in the presence of a 5 wt.% IL1 due to hydrolysis of the anion with hydrogen evolution and formation of aluminium fluoride. Erosion-corrosion processes have been studied for three aluminium alloys (Al 2011, Al 6061 and Al 7075) in a 90 wt.% IL1 solution in water in the presence of α-alumina particles. The erosion-corrosion rates are around 0.2 mm/year or lower, and increase with increasing copper content to give a corrosion resistance order of Al 6061 > Al 7075 > Al 2011. Results are discussed on the basis of scanning electron microscopy (SEM) observations, energy dispersive spectroscopy (EDS) analysis, X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) determinations.     

From crystalline V2O5 to nanostructured vanadium oxides using aromatic amines as templates

Nanoneedles, nanorods of B-VO₂, and vanadium oxide nanotubes with high crystallinity were synthesized via a one-step hydrothermal treatment using crystalline V₂O₅ as a precursor and aromatic amines (C₆H₅-(CH₂)_n-NH₂ with n=0, 1, 3) as structure-directing templates. Samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), thermal analysis, nitrogen adsorption/desorption isotherms and infrared spectroscopy. Nanoneedles, 0.5-5 μm in length and about 50 nm in average diameter and VO₂(B) nanorods about 20-100 nm wide and up to 2.5 μm long, have been obtained. The inner and the outer diameters of the vanadium oxide nanotubes vary, respectively, between 15-25 and 70-100 nm with a length up to 4 μm.