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.     

Investigations on structural and optical properties of Zn1−xGdxS nanoparticles

Zn_1−xGd_xS (x = 0.00, 0.02 and 0.04) nanoparticles were synthesized by facile chemical co-precipitation method using PVP as a surfactant. ZnS nanoparticles could be doped with Gd ions during synthesis without altering the XRD patterns of ZnS. Also, the pattern of the powders showed cubic zincblende structure. The particle size obtained from the XRD studies lies in the range 3-5 nm, whereas from TEM analysis it is 4 nm for x = 0.02 sample. The UV-Vis absorption spectra revealed that Zn_1−xGd_xS nanoparticles exhibit strong confinement effect as the blue shift in the absorption spectra with that of the undoped ZnS. The photoluminescence spectra showed enhanced luminescence intensity and the entry of Gd into host lattice.     

The wettability of poly(tetrafluoroethylene) by aqueous solutions of ternary surfactant mixtures

Contact angle measurements on poly(tetrafluoroethylene) (PTFE) surface were carried out for the systems containing ternary mixtures of cetyltrimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycols), Triton X-100 (TX100) and Triton X-165 (TX165). The aqueous solution of ternary surfactant mixtures were prepared by adding the third surfactant to the binary mixture of the surfactants where the synergetic effect in the reduction of the surface tension of water was determined, to compare the influence of the third surfactants on the values of surface tension of this binary mixture and the values of the contact angle on PTFE. The obtained results and calculations indicate that the ternary mixtures of CTAB + TX165 (αCTAB = 0.2, γ_LV = 60 and 50 mN/m) + TX100 (C = 10⁻⁸ to 10⁻² M) have the biggest efficiency of the reduction of contact angle of water on PTFE in comparison to aqueous solutions of the single surfactants and their binary and ternary mixtures. Also in the case of all studied ternary mixtures of surfactants at concentrations of the bulk phase corresponding to unsaturated monolayer at water-air interface the adsorption of surfactants at PTFE-water interface is different than that at water-air interface, but is the same at concentrations near the critical micelle concentration (CMC). Thus the linear dependences between γ_LV cos θ − γ_LV and cos θ − 1/γ_LV, in the range of concentration studied for all systems confirm the same adsorption at two interfaces only at C near the CMC.     

Ternary semiconductor compounds CuInS2 (CIS) thin films synthesized by electrochemical atomic layer deposition (EC-ALD)

In this paper the formation and characterization of the I-III-VI₂ semiconductor compound CuInS₂ (CIS) on gold substrate at room temperature by electrochemical atomic layer deposition (EC-ALD) method are reported. Optimum deposition potentials for each element are determined using cyclic voltammetry (CV) technique and Amperometric I-t method is used to prepare the semiconductor compound. These thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FT-IR). XRD results indicate that the CIS thin films have a (1 1 2) preferred orientation. The XPS analyses of the films reveal that Cu, In and S are present in an atomic ratio of approximately 1:1:2. And their semiconductor band gaps are found to be 1.50 eV by FT-IR.     

Spectroscopic characterization approach to study surfactants effect on ZnO2 nanoparticles synthesis by laser ablation process

Zinc peroxide nanoparticles having grain size less than 5 nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H₂O₂. The effect of surfactants on the optical and structure of ZnO₂ was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8 nm in pure H₂O₂, and H₂O₂ mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO₂ nanoparticles prepared with and without surfactants show a characteristic ZnO₂ absorption at 435-445 cm⁻¹. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV-vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830-840 and 420-440 cm⁻¹.     

A simple sonochemical approach for synthesis and characterization of Zn2SiO4 nanostructures

Zn₂SiO₄ nanoparticles have been successfully prepared via a simple sonochemical method, for the first time. The effect of various parameters including ultrasonic power, ultrasonic irradiation time and different surfactants were investigated to reach optimum condition. The as-prepared nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), Fourier transform infrared (FT-IR) spectra and energy dispersive X-ray microanalysis (EDX). The photocatalytic activity of Zn₂SiO₄ nano and bulk structures were compared by degradation of anionic dye methyl orange in aqueous solution under UV-light irradiation. Moreover, the cyclic voltammetry analysis of Zn₂SiO₄ nano and bulk structures were investigated.     

The electrical conductivity properties of polythiophene/TiO2 nanocomposites prepared in the presence of surfactants

A composite of polythiophene (PT) and nano-titanium dioxide (TiO₂), possessing core–shell structure, was synthesized via oxidative polymerization of thiophene using FeCl₃ in the presence of three different surfactants: anionic, cationic, and nonionic. The morphology of the obtained composite materials was investigated by SEM, proving the core–shell structure of the prepared nanocomposite. The formation and thermal stability of the PT onto TiO₂ nanoparticles were confirmed by FTIR and TGA analyses, respectively. XRD data show all of composite materials were amorphous structures. The electrical properties of the nanocomposites were investigated in the presence of surfactant materials, and the best semiconductor property was observed for PT/TiO₂-anionic system. This difference in the conductivity has been attributed to differences in the stability of the composites.     

Effects of surfactants on microwave-assisted solid-state intercalation of poly(carbazole) in Bentonite

The present preliminary investigation reports, for the first time, the effects of typical cationic and anionic surfactants on the microwave-assisted solid-state intercalation and polymerization of carbazole (Cz) in the basal spacings of Bentonite. The intercalation of cetyl pyridinium chloride (CPCl), a cationic surfactant, and naphthalene sulfonic acid (NSA), an anionic surfactant, in Bentonite was carried out at two loadings—25 and 50 wt%—using microwave irradiation. The in situ polymerization of Cz was successfully carried out into the surfactant-modified galleries of Bentonite. This was confirmed by Gel permeation chromatography (GPC). The intercalation of poly(carbazole) (PCz) was confirmed by FT-IR, UV–Visible, and XRD analyses. Although polymerization was carried out in the solid-state, the UV–Visible spectra revealed the doped state of PCz and the presence of a charge carrier tail. The XRD studies showed that the increase in the height of the galleries was higher in case of Bentonite/CPCl/PCz nanocomposites as compared to Bentonite/NSA/PCz nanocomposites. It also revealed different orientations of the two surfactants in the galleries of the clay. The average particle size of Bentonite/CPCl/PCz (1:0.25:0.25) and (1:0.5:0.5) nanocomposites was found to be in the range of 25–35 and 50–60 nm, respectively. The Bentonite/NSA/PCz (1:0.25:0.25) and (1:0.5:0.5) nanocomposites showed the average particle size in the range of 20–30 nm and 40–50 nm, respectively. The results revealed that both cationic and anionic surfactants strongly influenced the morphology of Bentonite/PCz nanocomposites. The difference in the mechanisms of solid-state intercalation of PCz in the presence of these surfactants has been proposed.     

Roles of oleic acid during micropore dispersing preparation of nano-calcium carbonate particles

In the present work, nano-calcium carbonate powder was prepared by micropore dispersion method with assistance of oleic acid as surfactant. CO₂ gas was dispersed into the Ca(OH)₂/H₂O slurry via a glass micropore-plate with the diameter of micropore about 20 μm. To investigate the effect of oleic acid on the size of CaCO₃ particles, different amount of oleic acid was added in Ca(OH)₂/H₂O slurry at 5 °C and 25 °C, respectively. XRD patterns show that cubic calcite is the only crystalline phase in all cases. ZPA data and TEM photo indicate that the average particle size synthesized at 5 °C without oleic acid is of about 40 nm, slightly smaller than that of prepared at 25 °C, and that the dispersity of sample prepared at 5 °C is better than that of 25 °C. When oleic acid is added in both temperatures, the average particle size decreases a little. FT-IR spectra demonstrate that oleic acid interacts with Ca²⁺ and carbon-carbon double bond existed on the surface of particle. Consequently, two opposite roles of oleic acid during the process of preparation of nano-CaCO₃ were proposed, namely preventing nanoparticles from growing during reaction and making nanoparticles reunite to a certain extent after reaction.     

Template-free synthesis of MnO2 nanowires with secondary flower like structure: Characterization and supercapacitor behavior studies

Manganese dioxide (MnO₂) nanowires with diameter about 30-70 nm is achieved via a two-step process: first, template-free cathodic electrodeposition from aqueous solution of Mn(NO₃)₂ on steel substrate and followed by heat treatment. The temperature-annealed sample was studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) methods and Fourier transform infrared (FT-IR) spectroscopy. The electrochemical performance of the MnO₂ sample was studied by cyclic voltammetry (CV) and chronopotentiometry in Na₂SO₄ solutions. The sample showed excellent supercapacitive behavior. The specific capacitance (SC) of 237 F g⁻¹ in a potential window of 0-0.9V was obtained at the scan rate of 2 mV s⁻¹. The SC calculated from the chronopotentiometry data is about 246 F g⁻¹. The SC was decreased by 16% after 1000 cycles.     

A novel one-step synthesis of mesostructured silica-pillared clay with highly ordered gallery organic-inorganic hybrid frame

A new class of organic-inorganic hybrid mesostructured silica-pillared clay (HSPC) has been prepared through the surfactant directed assembly of organosilica in the galleries of montmorillonite. The surfactant templates were removed from the pores by solvent-extraction. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), nitrogen adsorption-desorption measurements, solid-state ²⁹Si and ¹³C NMR, and Fourier-transform infrared (FT-IR) spectra. XRD patterns indicated a regular interstratifications of the clay layers for HSPCs. Depending on loading of phenyl groups, HSPCs had BET surface areas of 395-602 m² g⁻¹, pore volumes of 0.34-0.79 cm³g⁻¹, and the framework pore sizes in the supermicropore to small mesopore range (1.3-2.6 nm). HSPCs were hydrophobic and acidic. The number of silanol groups on the surface of HSPC materials has been titrated by a surface reaction with hexamethyldisilazane, followed by quantification of the liberated NH₃. Based on this method extracted HPCHs have high silanol numbers, a very important feature with respect to the amount of catalytic sites that can eventually be grafted onto the surface.     

Chemical synthesis of nanocrystalline SnO2 thin films for supercapacitor application

Nanocrystalline SnO₂ thin films were deposited by simple and inexpensive chemical route. The films were characterized for their structural, morphological, wettability and electrochemical properties using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy techniques (SEM), transmission electron microscopy (TEM), contact angle measurement, and cyclic voltammetry techniques. The XRD study revealed the deposited films were nanocrystalline with tetragonal rutile structure of SnO₂. The FT-IR studies confirmed the formation of SnO₂ with the characteristic vibrational mode of Sn-O. The SEM studies showed formation of loosely connected agglomerates with average size of 5-10 nm as observed from TEM studies. The surface wettability showed the hydrophilic nature of SnO₂ thin film (water contact angle 9°). The SnO₂ showed a maximum specific capacitance of 66 F g⁻¹ in 0.5 Na₂SO₄ electrolyte at 10 mV s⁻¹ scan rate.     

Adsorption and photocatalytic degradation of methylene blue on Zn1−xCuxS nanoparticles prepared by a simple green method

Nanoparticles of Zn_1−xCu_xS with various dopant contents (0 ≤ x ≤ 0.15) were prepared in water by refluxing for 90 min at about 95 °C. Powder X-ray diffraction (XRD) patterns of the nanoparticles demonstrate that loading of Cu²⁺ ions does not change the crystal structure of ZnS. Scanning electron microscopy (SEM) images demonstrate that size of the nanoparticles decreases with increasing Cu²⁺ ions. UV-Vis diffuse reflectance spectra (DRS) of the nanoparticles show significant absorption in visible light region. Adsorption capacity of the nanoparticles for methylene blue (MB) increases with mole fraction of copper ions. Photocatalytic activity of the nanoparticles toward photodegradation of MB was evaluated under visible light irradiation. The results indicate that Zn_0.85Cu_0.15S nanoparticles exhibit highest photocatalytic activity among the prepared samples. Moreover, effects of refluxing time applied for preparation of the nanoparticles and calcination temperature were investigated.     

Synthesis and room temperature photoluminescence of ZnO/CTAB ordered layered nanocomposite with flake-like architecture

Flake-like ZnO/surfactant ordered layered nanocomposite has been synthesized by self-assembly at room temperature with the presence of cetyltrimethylammonium bromide (CTAB, CH₃(CH₂)₁₅N⁺(CH₃)₃Br⁻) surfactant. The procedure described in this study is attractive since it gives high yields of ordered layered nanocomposite with flake-like architecture. XRD results showed the formation of a layered structure with two layered spacings ca. 18.56 Å. SEM and FT-IR spectroscopy were used to further characterize ZnO/CTAB nanolayered composite. The ZnO/CTAB-ordered layered nanocomposite exhibits the room temperature photoluminescence (RTPL) characteristics. It is inferred that the RTPL of ZnO/CTAB-layered nanocomposite might be induced by the interfacial effect between the ZnO and the surfactant.     

Thermally stable blue-emitting NaSrPO4:Eu phosphor for near UV white LEDs

A novel blue light emitting NaSr_1 − xPO₄:Eu²⁺_x (x = 0.001 to 0.02) phosphors were prepared by solid-state reaction method to investigate its optical properties and thermal stability for its application in white light-emitting diodes (w-LEDs). The excitation and emission spectra of the prepared phosphor reveal a broad emission peak centered at 460 nm which arises due to 4f-5d transitions of Eu²⁺ upon the near ultra-violet (n-UV) excitation wavelength at 380 nm. The effect of Eu²⁺ doping concentration and sintering temperature on the emission intensity of NaSrPO₄:Eu²⁺ was investigated along with its chromaticity coordinates. The temperature dependent luminescence properties of the prepared phosphor show better results than that of the commercial YAG:Ce³⁺phosphor. Besides, their XRD, FT-IR, SEM, TG, and DTA profiles have also been analyzed to explore its structural details.     

Microwave assisted one pot synthesis of biocompatible gold nanoparticles in Triton X-100 aqueous micellar medium using tryptophan as reducing agent

The present work reports an environmentally benign process for the synthesis of gold nanoparticles via microwave-assisted heating method, using a basic amino acid l-Tryptophan as reducing agent. The synthesis was carried out in the presence of a nonionic surfactant Triton X-100 (TX-100) aqueous micellar system. Influence of various reaction parameters such as microwave irradiation time and concentrations of precursor ion were analyzed. The effect of pH on the plasmonic properties and stability of synthesized AuNPs were studied in detail. The various size distributions of gold nanostructures obtained were characterized and analyzed by ultraviolet visible spectroscopy (UV-Vis), TEM and DLS analysis. Fourier transform infrared (FT-IR) measurements were carried out to identify the interaction sites responsible for capping and efficient stabilization by the amino acid as well as the surfactant. The synthesized gold nanoparticles were stable for more than 6 months at ambient conditions.     

Desorption of surfactant and sintering of surface-modified PdxNi1 − x nanoparticles

A series of Pd_xNi_1 − x nanoparticles in a diameter of 6-7 nm were prepared by wet chemical reduction. They were then modified with two surfactants, stearic acid (SA) and polyethylene glycol (PEG). Desorption of the surfactant was studied using a temperature programmed desorption technique, and the sintering behavior of surface-modified Pd_xNi_1 − x nanoparticles was examined. Since surface energy of the nanoparticles depends on the alloy composition, it can be correlated with the desorption temperature of surfactant from the nanoparticle surface. Because Ni has a higher surface energy, the surfactant desorption temperature increases as the Ni content increases. With the same stoichiometry, the desorption temperature of SA is always higher than that of PEG. The SA-modified nanoparticles have higher thermal stability and are less sintered than PEG-modified nanoparticles. The sintering and growth behavior of the nanoparticles can be correlated with variation of surface energy due to different surface modification.     

Electrochemical supercapacitor studies of hierarchical structured Co2+-substituted SnO2 nanoparticles by a hydrothermal method

Hierarchical structured Co-doped SnO₂ nanoparticles are prepared by a low temperature hydrothermal process. The structural and surface morphologies of the SnO₂ and Sn_1?xCo_xO₂ nanoparticles are studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The Sn_1?xCo_xO₂ nanoparticles form with a tetragonal rutile structure during the hydrothermal process without further calcination. The pseudocapacitance behavior of the Sn_1?xCo_xO₂ nanoparticles is characterized by cyclic voltammetry (CV) in 1.0 M H₂SO₄ electrolyte. The specific capacitance (SC) is found to increase with an increase in cobalt content. A maximum SC of 840 F g^?1 is obtained for a Sn_0.96Co_0.04O₂ composite at a 10 mV s^?1 scan rate.     

Optical and electrochemical properties of Cu-doped NiO films prepared by electrochemical deposition

Cu-doped nickel oxide (NiO) thin films were prepared by electrochemial deposition (cathodic deposition) technique onto the fluorine doped tin oxide (F: SnO₂; FTO) coated glass substrates from organic solutions. Effects of Cu content on the morphology, structure, optical and electrochromic properties of NiO films were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), ultraviolet-visible spectrophotometer (UV-vis) and cyclic voltammetry (CV), respectively. SEM images indicated the formation of nanorods after Cu was added. The films were formed with amorphous or short-range ordered NiO grains and a trace of face-centered cubic Ni_xCu_1−xO confirmed by XRD. The transmittances of both bleached state and colored state were significantly lowered when Cu was added. The NiO films doped with Cu (the molar ratio was 1/8) exhibited the optimum electrochromic behavior with a variation of transmittance (ΔT) up to ∼80% at the wavelength range of 350-600 nm. Cu doping reduces the response time for both the coloring and bleaching states, and the reversibility of the redox reaction was increased as well.     

Electrochemical behavior of cobalt from 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

The electrodeposition of metallic cobalt from a 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid was investigated. The electrochemical behavior of Co(II) in the ionic liquid on a platinum working electrode at 60 °C was studied by cyclic voltammetry and chronoamperometry. The results from the cyclic voltammetry showed that the electrodeposition of metallic Co in the ionic liquid was an irreversible process and controlled by the diffusion of Co(II) on a platinum working electrode. The average value of αn_α was calculated to be 0.35 and the diffusion coefficient (D₀) of Co(II) was calculated to be 1.76 × 10⁻⁸ cm²/s at 60 °C. Chronoamperometric results indicated that the electrodeposition of Co on a platinum working electrode followed the mechanism of instantaneous nucleation and three-dimensional growth with diffusion-controlled. The cobalt plating was uniform, dense, shining in appearance with good adhesion to the platinum substrate at 60 °C. The scanning electron microscope (SEM) micrographs were used to confirm that the cobalt plating was denser and finer at 60 °C. Energy dispersive X-ray analysis (EDAX) profile showed that the obtained plating was pure cobalt. X-ray diffraction (XRD) pattern indicated that there was a preferred orientation direction and the average size of cobalt grains was 40 nm.