Papers by Keyword: Sonochemical Method

Abstract: The role of both zinc oxide (ZnO) and zinc (Zn) seed layers were evaluated for the growth of vertically aligned high-quality zinc oxide (ZnO) nanorods by the sonochemical method. A total of four samples categorized into two groups were evaluated, with a different type and thickness of seed layer for the first group - ZnO, 85 nm and the second group - Zn, 55 nm respectively. This was after depositing Ti (10 nm) as the adhesion layer on p-type Si (111) substrates for two samples, and without the adhesion layer on the others. All depositions were carried out using RF-sputtering. The effects of the seed layers on the growth of vertically aligned high-quality ZnO nanorods were systematically studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). Results show that the type and thickness of a seed layer are key parameters to the synthesis of high quality ZnO nanorods. Results also show that the Ti (10 nm) adhesion layer did not affect the growth surface-to-volume ratio of the ZnO nanorods and the ZnO nanorods synthesized using ZnO (85 nm) as seed layer has a better surface-to-volume ratio compared to that using Zn (55 nm) as seed layer, with and without the adhesion layer.

Abstract: This study reported the preparation of nanocrystalline CoFe₂O₄ in single step by the sonochemical method in highly basic aqueous solution without requiring of high temperature calcination process. To prepare nanocrystalline CoFe₂O₄, the mixed solution of the required molar ratio of cobalt nitrate hexahydrate (Co (NO₃).6H₂O) and ferric nitrate nonahydrate (Fe (NO₃).9H₂O) was precipitated in high concentration of sodium hydroxide medium solution (NaOH) under high intensity ultrasonic irradiation (20 kHz, 150 W/cm²). The effect of NaOH concentration (5, 10, 15 and 20 M) on phase formation, microstructure and magnetic property of CoFe₂O₄ was investigated. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results showed that the as-prepared powders were single phase CoFe₂O₄ with cubic spinel structure. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study showed that nanocrystalline CoFe₂O₄ had monosized distorted spherical morphology and an agglomeration of the nanocrystalline CoFe₂O₄ into nanoparticles was observed when increasing the NaOH concentration. The nanocrystalline CoFe₂O₄ exhibited superparamagnetic property and the saturation magnetization (M_s) obtained from vibrating sample magnetometry (VSM) was found to correlate with the crystallite size and varied from 39-45 emu/g_.

Abstract: Titanium dioxide (TiO₂) is one of popular semiconductor materials that usually used for photocatalytic application. Recent studies show the improvement of TiO₂ photocatalytic activity through nitrogen doping (N-doped TiO₂). In this study, we focused on the synthesis and characterization of N-doped TiO₂. Ultrasonic assisted synthesis or sonochemical method was used to prepare N-doped TiO₂ polycrystalline powder under room temperature. X-ray diffractometer (XRD), and diffuse reflectance ultraviolet-visible spectrophotometer (DR-UV) were employed to evaluate physical properties of N-doped TiO₂. XRD pattern exhibited that all samples have anatase crystalline phase and crystallite size decrease with increase of N dopant concentration. The absorbance spectra showed the slight shift toward higher wavelength (red shift) and from Kubelka-Munk function the band gaps were getting smaller with increase of N content. The increase of photocatalytic activity under solar radiation was achieved by N-doped TiO₂ samples with highest efficiency about 81 % for 5% of N doping concentration.

Abstract: Al-doped ZnO nanoparticles were synthesized by sonochemical method from zinc acetate dehydrate and aluminum acetate as starting precursors. The deionized (DI) water was selected as the solvent. Sonication of the precursor was performed by a Sonics Model VCX 750 for 30 minutes until precipitated product was finally obtained. The as-precipitated powders were calcined at different temperature range of 550-1100 °C for 2 hr. For all samples, their crystal structures were investigated by X-ray diffraction (XRD) and surface morphologies were observed by scanning electron microscope (SEM). The XRD results revealed that, the purity of as-synthesized powders increases when the calcination temperature increases. Moreover, it is noticed that the AlZnO partial peaks will appear when the as-synthesized powders were calcined at 800 – 1000 °C. In addition, SEM micrographs show the increase of agglomeration and the particles when the calcination temperature increases.

Abstract: The current paper reported the sonichemical synthesis and optical properties of the Bi-doped ZnO with superstructural nanomaterials. The morphology of the powders revealed by SEM and TEM exhibited stelliform dendrite and the sonication time appeared to be a critical parameter for the shape determination. The optical properties of the products were investigated by measuring the photoluminescence spectra at room temperature and the results demonstrated that the synthesized material has good optical properties.

Abstract: SrTiO3 nanoparticles were successfully synthesized by a sonochemical method at room temperature. The as-prepared powders were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM), and exhibited a pure phase SrTiO3 with a perovskite structure about 20nm in size with uniform and nearly spherical shape. It is found that the size of the obtained nanoparticles increased with prolonging the ultrasonic time.

Abstract: Bundle-like ZnO nanostructure was rapidly synthesized by a sonochemical method at 70 °C, using zinc nitrate, citric acid, ammonia, and sodium hydroxide as reactants. The resulting materials were characterized by X-ray diffraction, scanning electron microscopy, and photoluminescence measurements. The bundle-like nanostructure was formed by the anisotropic growth of the ball-like nanostructure. The room-temperature PL spectrum of the bundle-like nanostructure exhibits a weak ultraviolet emission band and a strong visible emission.

Abstract: Nanocristalline TiO₂ obtained by a facile and environment-friendly sonochemical method was subjected to thermal treatment in the temperature range of 400-900 °C in order to produce variable anatase-rutile phases ratio. The relationship between the optical bandgap and the electrochemical behavior was studied. All the stages of phase transformation of the as-prepared sample such as: nucleation, growth and coarsening were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that phase transformation mechanism stems from the redistribution of energy in the system and a critical particle size. On the other hand, the samples were characterized by UV-vis spectroscopy for the bandgap studies. The optical band gap of as-prepared sample increases to 3.31 eV with respect to 3.20 eV for bulk-anatase. This expansion could be attributed to quantum size effect. The i-E characteristics of samples with variable anatase-rutile ratio were obtained using cyclic voltammetry technique in a 0.5 M H₂SO₄ solution at room temperature. The foremost charge magnitude was obtained when anatase had a critical size of 17 nm. Analyzing both particle size for anatase and rutile, we observed that when rutile is the dominating phase and its size difference larger in 35% than anatase, the current reaches its minimum values. Based on electrochemical results, the optimal particle size and content phases control are important in order to obtain an increase in the electrochemical performance in the Hydrogen Evolution Reaction (HER) zone

Abstract: Bismuth sulfide (Bi2S3) nanorods were successfully fabricated by sonochemical aqueous solution. The morphology, crystallinity and composition of samples at various growth stages were investigated by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The results showed that the Bi2S3 nuclei had an obvious tendency to arrange themselves in rod-like arrays over extended length scales under soft template. Moreover the crystallinity would be reinforced with the elongation of the aging periods. The growth mode of particle−to−particle by self-assembly under soft template was proposed. The band gap energy of Bi2S3 nanorods was estimated at about 1.36 eV by UV-Vis absorption spectroscopy.

Abstract: ZnO nanostructures of different morphologies were grown in a controlled manner by a novel sonication assisted sol gel process. Variation in the alcoholic medium resulted in nanorods and flower like ZnO nanostructures. Flower like ZnO nanostructures with a root size of 1m and a tip of 150nm were synthesized using ethanol as solvent, while ZnO nanorods with diameter less than 60 nm and length greater than 1m were synthesized using methanol as solvent. The samples were characterized by X-ray diffraction and Scanning Electron Microscopy. The XRD results show the formation of highly crystalline ZnO with no detectable level of impurity. In this paper, a possible mechanism for the variation of morphology with the change in solvent has been discussed. The effect of solvent vapour pressure on the sonication process has been explained. The solvent vapour pressure has an effect on the intensity of sonication which affects various chemical reactions taking place during the formation of ZnO. The effect of ethylenediamine on the chemical reactions leading to formation of ZnO nanostructures has also been analyzed.