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.     

Solvothermal synthesis of Cd(OH)2 and CdO nanocrystals and application as a new electrochemical sensor for simultaneous determination of norfloxacin and lomefloxacin

Cadmium hydroxide (Cd(OH)₂) microcrystals were synthesized in ethanol–water medium by using cadmium chloride as cadmium source and 1,10-phenanthroline as complexation agent under solvothermal condition. The sample was characterized by FT-IR, X-ray diffraction (XRD), scanning electron microscopy (SEM) and TEM. The as-prepared Cd(OH)₂ product were transformed to hexagonal CdO nanocubes by thermal treatment in air at 500 °C. The possible growth mechanism for the formation of different morphologies at basic medium has been proposed. DPV experiments were carried out for the simultaneous determination of norfloxacin and lomefloxacin in the acetate buffer solution with pH 4.5.     

Facile synthesis and capacitive performance of the Co(OH)2 nanostructure via a ball-milling method

Co(OH)₂ nanoparticles were synthesized using only CoSO₄·7H₂O and NaOH as reactants without other auxiliary reagents via a simple, low-cost and practical ball-milling technique and investigated as the active electrode materials for supercapacitors. The structure and morphology of the resulting Co(OH)₂ samples were examined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The observations revealed the formation of brucite-like phase of β-Co(OH)₂, which had an irregular sphere-like shape with an average size of 50-100 nm. When investigated as electrode materials for supercapacitors, the β-Co(OH)₂ exhibited good energy-storage performances in terms of high specific capacitance of 599 F g⁻¹ and excellent capacity retention, suggesting its potential application in the electrode material for supercapacitors.     

Investigation of the characteristics and corrosion resistance of Al2O3/TiN coatings

Al₂O₃ /TiN double and Al₂O₃/Cr/TiN triple coatings were produced on stainless steel substrates using plasma-detonation techniques. Investigation of the microstructure and characteristics of the coatings after the preparation was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The corrosion resistance of the coatings was studied in several electrolytic solutions (0.5 M H₂SO₄, 1 M HCl, 0.75 M NaCl) using electrochemical techniques (open circuit potential, cyclovoltammetry and potentiodynamic polarization). The obtained results showed, in most of the cases, an improvement of the corrosion resistance, except in NaCl solutions. The effect of the controlled thickness of TiN and Cr layers as well as the additional treatment with a high-current electron beam was also investigated. Nuclear reaction analysis (NRA), Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy (SEM) were applied for the characterization of the samples before and after the corrosion experiments.     

A simple and low temperature process for super-hydrophilic rutile TiO2 thin films growth

We investigate an environmentally friendly aqueous solution system for rutile TiO₂ violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO₂ with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15 ± 0.4 nm, characterize the films. Band gap energy of 4.61 eV for direct transition was obtained for the rutile TiO₂ films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.     

Facile fabrication of Zn/Zn5(OH)8Cl2·H2O flower-like nanostructure on the surface of Zn coated with poly (N-methyl pyrrole)

Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructures was electrodeposited on the coated Zn with poly (N-methyl pyrrole) in 0.1 M Zn (NO₃)₂ and 0.1 M KCl solution. The morphology and the structure of the Zn/Zn₅(OH)₈Cl₂·H₂O were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction analysis (XRD). The FT-IR results showed special peaks at 908 and 728 cm⁻¹ related to Zn₅(OH)₈Cl₂·H₂O. The FESEM results indicated that Zn/Zn₅(OH)₈Cl₂·H₂O consists of a flower-like nanostructure and these flower-shaped structures contain many shaped nanopetals with the thickness of 27.8 nm. The XRD result confirmed that the major phase of electrodeposited product in 0.1 M KCl as supporting electrolyte was Zn₅(OH)₈Cl₂·H₂O. The ability of PMPy to create a thin film and the existence of several pores in its matrix act as a mold for the growth of Zn/Zn₅(OH)₈Cl₂·H₂O flower-like nanostructure. The trapping of Cl⁻ and OH⁻ within pores can be considered as the reason for the formation of flowerlike Zn/Zn₅(OH)₈Cl₂·H₂O nanostructures in 0.1 M KCl.     

Temperature controlled synthesis of SrCO3 nanorods via a facile solid-state decomposition rout starting from a novel inorganic precursor

Strontium carbonate nanorods have been successfully synthesized via solid-state decomposition of a new precursor, [Sr(Pht)(H₂O)₂]. The obtained nanorods were found to be orthorhombic with the length of 70-100 nm and the diameter of about 10-15 nm. The Effect of calcinations temperature on morphology and purity of the products has been investigated. Strontium carbonate nanorods were formed at 500 °C. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. In addition, further evidence for the purity and stoichiometry of the product was obtained by XPS (X-ray photoelectron spectroscopy) spectrum.     

Synthesis and characterization of cadmium hydroxide nano-nest by chemical route

A facile chemical route based on room temperature chemical bath deposition (CBD) was developed to deposit the Cd(OH)₂ nano-nest. The growth mechanism follows two-stage crystallization with initial growth of nucleation centers, followed by subsequent anisotropic growth. The nano-nest morphological evolution of Cd(OH)₂ on different substrates has been carried out. These films have been characterized by the techniques; such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), optical absorption, contact angle measurement and thermoelectric power (TEP) measurements. The X-ray diffraction study revealed that the as deposited film consists of cadmium hydroxide (Cd(OH)₂) phase. The nano-nest consisted of wires with nearly uniform in dimensions, with diameter around 30 nm and length of few microns. As-deposited Cd(OH)₂ film used in this study showed water contact angle of 66°. The optical bandgap was found to be 3.2 eV, with n-type electrical conductivity as confirmed from thermo-emf measurements.     

Synthesis of nanocrystalline Zn0.5Mn0.5Fe2O4 via in situ polymerization technique

Nanocrystalline Zn_0.5Mn_0.5Fe₂O₄ was synthesized through the pyrolysis of polyacrylate salt precursors prepared via in situ polymerization of the metal salts and acrylic acid. The pyrolysis behavior of the polymeric precursors was studied by use of thermal analysis. The as-obtained product was characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), electron diffraction (ED) pattern, scanning electron microscopy (SEM) and electron dispersive X-ray (EDX) analysis. The results revealed that the particle size is in the range of 15–25 nm for Zn-Mn ferrites with good crystallinity. Magnetic properties of the sample at 300 K were measured using a vibrating sample magnetometer, which showed that the sample exhibited characteristics of superparamagnetism.     

Preparation of flower-like Cu2O nanoparticles by pulse electrodeposition and their electrocatalytic application

A pulsed electrodeposition technique based on a multipulse sequence of potentials of equal amplitude, duration and polarity was employed for preparation of highly dispersed flower-like cuprous oxide (Cu₂O) nanoparticles. The morphology analysis of the particles using scanning electron microscope (SEM) reveals that the flower-like particles were from sequential growth of Cu₂O along the (1 1 1) direction on the cubic Cu₂O (1 0 0). The structure and the chemical composition of the deposits were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Optical property and band gap of the Cu₂O was investigated using UV/vis diffuse reflection spectra (DRS), and the measured value of energy gap is 2.18 eV. The dark and light open circuit potential-time characterization study showed that the flower-like Cu₂O nanoparticles exhibited good photoelectric response. Cyclic voltammetry carried out in the presence of p-nitrophenol (p-NP) shows that the electrocatalytic performance of the Cu₂O particles for the reduction of p-NP, which was characterized by a cathodic peak at around −0.6 V. The influence of the incidence of light on the electrocatalysis is also discussed.     

Effect of pyridine as a ligand in precursor on morphology of CdS nanoparticles

[Cd(thqdtc)₂], [Cd(thqdtc)₂(py)] and [Cd(thqdtc)₂(2,2′-bipy)] (where thqdtc = 1,2,3,4-tetrahydroquinolinecarbodithioate; py = pyridine; 2,2′-bipy = 2,2′-bipyridine) have been found to be effective single source precursors for the preparation of diethylenetriamine capped CdS nanoparticles via solvothermal method. Flower-like and rod-like CdS nanoparticles were prepared at a relatively low temperature by thermolysis of the precursors using chelating solvent diethylenetriamine. Use of [Cd(thqdtc)₂] and [Cd(thqdtc)₂(2,2′-bipy)] afforded rod-shaped nanoparticles and flower-like nanoparticles obtained from [Cd(thqdtc)₂(py)]. UV–Visible spectroscopy established pronounced quantum confinement effect. X-ray diffraction (XRD) analysis revealed hexagonal crystal phase for so obtained CdS nanoparticles. The nanoparticles were also characterized by transmission electron microscopy (TEM) and fluorescence spectroscopy.     

A novel toluene sensor based on ZnO-SnO2 nanofiber web

We proposed in the present work that large-scale synthesis of sensitive ZnO-SnO₂ nanofibres which can be obtained via a simple electrospinning method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction patterns (XRD) showed the average diameter of ZnO-SnO₂ nanofibres ranging between 100 and 200 nm, the mixture of wurtzite (ZnO) and rutile (SnO₂) structure in the composite fibers. The sensitivity of the obtained ZnO-SnO₂ nanofibres to toluene was also investigated. The results showed that under optimal conditions, the calibration curve of response versus toluene concentration was linear in the range of 10-300 ppm, the response and recovery time were only several seconds, and sensitivity for toluene was desirable.     

Fabrication of chain-like Mn2O3 nanostructures via thermal decomposition of manganese phthalate coordination polymers

A novel manganese coordination polymer [Mn(Pht)(H₂O)]_n as a precursor was obtained by chemical precipitation involving an aqueous solution of anhydrous manganese acetate and phthalate anion as a potential O-banded ligand. Fourier transform infrared (FT-IR) results proved that phthalate anions coordinate to metal cations as a chelating bidentate ligand, making polymeric structure. The Mn₂O₃ nanostructures have been prepared via thermal decomposition of as-prepared manganese phthalate polymers as precursor in the presence of oleic acid (OA) and triphenylphosphine (TPP) as a stabilizer and capping. Different approaches such as FT-IR, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to characterize the products. TEM images and XRD analysis indicated that the as-synthesized chain-like Mn₂O₃ has a crystal phase of cubic syngony with a mean size of ∼40 nm.     

Preparation, conversion, and comparison of the photocatalytic property of Cd(OH)2, CdO, CdS and CdSe

In this paper, we report the hydrothermal preparation of Cd(OH)₂ nanowires and further conversion to CdO nanobelts, CdS nanowires and CdSe nanoparticles through thermal treatment, solvothermal and mixed-solvothermal routes, respectively. The as-obtained products were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FEMSEM). Research showed that four cadmium compounds were good photocatalysts for the degradation of organic dyes such as Safranine T and Pyronine B, under irradiation of 365 nm UV light. The order of catalytic activity of different materials was found to be Cd(OH)₂<CdO<CdS<CdSe.     

Green synthesis and characterization of superparamagnetic Fe3O4 nanoparticles

In this paper, we have first demonstrated a facile and green synthetic approach for preparing superparamagnetic Fe₃O₄ nanoparticles using α-d-glucose as the reducing agent and gluconic acid (the oxidative product of glucose) as stabilizer and dispersant. The X-ray powder diffraction (XRD), X-ray photoelectron spectrometry (XPS), and selected area electron diffraction (SAED) results showed that the inverse spinel structure pure phase polycrystalline Fe₃O₄ was obtained. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results exhibited that Fe₃O₄ nanoparticles were roughly spherical shape and its average size was about 12.5 nm. The high-resolution TEM (HRTEM) result proved that the nanoparticles were structurally uniform with a lattice fringe spacing about 0.25 nm, which corresponded well with the values of 0.253 nm of the (3 1 1) lattice plane of the inverse spinel Fe₃O₄ obtained from the JCPDS database. The superconducting quantum interference device (SQUID) results revealed that the blocking temperature (T_b) was 190 K, and that the magnetic hysteresis loop at 300 K showed a saturation magnetization of 60.5 emu/g, and the absence of coercivity and remanence indicated that the as-synthesized Fe₃O₄ nanoparticles had superparamagnetic properties. Fourier transform infrared spectroscopy (FT-IR) spectrum displayed that the characteristic band of Fe-O at 569 cm⁻¹ was indicative of Fe₃O₄. This method might provide a new, mild, green, and economical concept for the synthesis of other nanomaterials.     

Preparation and photoluminescence characteristics of Eu-doped MgAl1.8Y0.2O4 nanocrystals

A simple combustion route was employed for the preparation of Eu³⁺-doped MgAl_1.8Y_0.2−xO₄ nanocrystals using metal nitrates as precursors and urea as a fuel in a preheated furnace at 500 °C. The powders thus obtained were then fired at 1000 °C for 3 h to get better luminescent properties. The incorporation of Eu³⁺ activator in these nanocrystals was checked by luminescence characteristics. These nanocrystals displayed bright red color on excitation under 254 nm UV source. The main emission peak was assigned to the transition [⁵D₀→⁷F₂] at 615 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies were carried out to understand surface morphological features and the particle size. Crystal structures of the nanocrystals were investigated by the X-ray diffraction (XRD) technique. The crystallite size of the as-prepared nanocrystals was around 29 nm, which was evaluated from the broad XRD peaks. The crystallite size increased to ∼45 nm on further heat treatment at 1000 °C.     

Physico-chemical, optical and electrochemical properties of iron oxide thin films prepared by spray pyrolysis

Iron oxide thin films were prepared by spray pyrolysis technique onto glass substrates from iron chloride solution. They were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and (UV-vis) spectroscopy. The films deposited at T_s ≤ 450 °C were amorphous; while those produced at T_sub = 500 °C were polycrystalline α-Fe₂O₃ with a preferential orientation along the (1 0 4) direction. By observing scanning electron microscopy (SEM), it was seen that iron oxide films were relatively homogeneous uniform and had a good adherence to the glass substrates. The grain size was found (by RX) between 19 and 25 nm. The composition of these films was examined by X-ray photoelectron spectroscopy and electron probe microanalysis (EPMA). These films exhibited also a transmittance value about 80% in the visible and infrared range. The cyclic voltammetry study showed that the films of Fe₂O₃ deposited on ITO pre-coated glass substrates were capable of charge insertion/extraction when immersed in an electrolyte of propylene carbonate (PC) with 0.5 M LiCLO₄.     

Efficient visible-light-induced photocatalytic degradation of MO on the Cr-nanocrystalline titania-S

In order to improve visible light photocatalytic activities of the nanometer TiO₂, a novel and efficient Cr,S-codoped TiO₂ (Cr-TiO₂-S) photocatalyst was prepared by precipitation-doping method. The crystalline structure, morphology, particle size, and chemical structure of Cr-TiO₂-S were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) techniques, respectively. Results indicate that the doping of Cr and S, cause absorption edge shifts to the visible light region (λ > 420 nm) compare to the pure TiO₂, reduces average size of the TiO₂ crystallites, enhances desired lattice distortion of Ti, promotes separation of photo-induced electron and hole pair, and thus improves pollutant decomposition under visible light irradiation. The photocatalytic activities of Cr-TiO₂-S nanoparticles were evaluated using the photodegradation of methyl orange (MO) as probe reaction under the irradiation of UV and visible light and it was observed that the Cr-TiO₂-S photocatalyst shows higher visible photocatalytic activity than the pure TiO₂. The optimal Cr-TiO₂-S concentration to obtain the highest photocatalytic activity was 5 mol% for both of Cr and S.     

Aerosol-assisted flow synthesis of WxTi1−xO2 solid solution spheres with enhanced photocatalytic activity

In this paper, W_xTi_1−xO₂ solid solutions (x = 0.000, 0.005, 0.010, 0.015, and 0.020) microspheres were synthesized with an aerosol-assisted flow synthesis method. The resulting samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption, UV-vis diffuse reflectance spectrum (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the as-prepared catalysts were measured by the degradation of rhodamine B (RhB) under visible light irradiation (λ ≥ 420 nm). All the solid solutions exhibited higher photocatalytic activities than pure TiO₂ and the W_0.015Ti_0.985O₂ solid solution possessed the highest photocatalytic activity. The degradation constant of RhB on W_0.015Ti_0.985O₂ solid solution catalyst was about 15 times of that of the pure TiO₂ and 25 times of that of Degussa P25, respectively. This study provides an effective method to prepare visible light photocatalysts on a large scale.     

Fabrication and characterizations of a polymer hybrid OA/MA/St-TiO2

A nano-hybrid composite of octadecyl acrylate/maleic anhydride/styrene (OA/MA/St) encapsulating nano-TiO₂ with an average particle size of 30-60 nm was fabricated based on chemical modification of nanotitania. The polymer hybrid OA/MA/St-TiO₂ and nano-TiO₂ were characterized by infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), static contact angle (CA) as well as transmission electron microscopy (TEM). FT-IR spectra and TGA results suggest that the copolymer OA/MA/St adheres on the surface of nano-TiO₂ through physical adsorption and chemical bonding. The calculated reacted OH surface density is about 0.6 OH/nm², and the modification efficiency is approximately 27.28%. In addition, when the molar ratio of OA/MA/St is 7:2:1, the hybrid shows the strongest hydrophobicity, and its static contact angle reaches as high as 146°. TEM image of the hybrid OA/MA/St-TiO₂ reveals that the modified particles have good dispersibility and compatibility with n-hexane.