INTERNATIONAL NANO LETTERS (INL)
Year:2012 | Volume:2 | Issue:2|Papers Count:8

In this study, we describe the synthesis of carbon nanotubes (CNTs) by chemical vapor deposition at 500oC to 975oC, over Co3O4/MgO catalyst. The size of Co3O4 nanoparticles is controlled by changing cobalt nitrate concentration in aqueous solution by impregnation method. The main object of this study is the synthesis of CNTs that started suddenly without any preheating of catalyst nanoparticles. The effect of sudden initiation and conventional preheating processes of catalyst nanoparticles on yield of CNTs was then described. The results suggest that this sudden initiation of synthesis process affects the carbon yield and morphology of CNTs.

This paper demonstrates the synthesis of SnO2 nanoparticles using a simple hydrothermal route in the presence of the surfactant hydrazine at 100oC for 12 h. X-ray diffraction (XRD), field emission scanning electron microscopy, and transmission electron microscopy (TEM) were employed to characterize the as-prepared product, and optical property was studied by UV-visible diffuse reflectance spectroscopy (DRS). The XRD pattern of the as-prepared sample is indexed to the tetragonal structure of SnO2, and the calculated particle size is 22.4 nm, which is further confirmed by TEM. The selected area electron diffraction patterns showed continuous ring patterns without any additional diffraction spots and rings of secondary phases, revealing their crystalline structure. Analysis of the DRS spectrum showed the bandgap of the synthesized SnO2 to be 3.6 eV. The anionic surfactant hydrazine plays a key role in the formation of the SnO2 nanostructures. A probable reaction for the formation of SnO2 nanoparticles is proposed.

Nanostructured TiO2 has been synthesized using one-step sol–gel method and characterized by different characterization techniques (SEM, EDS, XRD, and UV–vis spectroscopy). The photocatalytic degradation of methylene blue (MB) and Congo red (CR) is studied with the synthesized TiO2. The photocatalytic degradation data has been validated using several kinetic models. The TiO2 showed efficient photocatalytic degradation performance on MB and CR. In addition to this, the effect of pH on the photocatalytic degradation has been investigated. The TiO2 showed enhanced photocatalytic performance in basic media than that in neutral or acidic ones.

Bromothymol blue (BTB) thin films were prepared by depositing a thin layer of a solution containing tetraorthosilicate and BTB pH indicator in the presence of surfactants, namely cetyltrimethylammonium bromide (C19H42BrN, CTAB) or dodecyldimethylamine oxide (C14H31NO, 69%), C16H35NO (11%), Genaminox LA onto a glass slide substrate. CTAB or GLA surfactants were used to improve the mesostructure of the host material and to increase its porosity. Optical BTB thin films were found to be sensitive against pH and behave as free BTB. This provides evidence for weak interactions between the BTB molecules and the host silica matrix. The effects of the sol mixture on the stability and reproducibility and the colorimetric response to solutions of different pH were examined and pKa values were determined. The BTB thin film sensors showed an advantage over the encapsulated monolithic sensors in which the thin film sensors exhibit a faster response time than the monolithic disks. These pH sensors showed reproducibility and high stability behavior.

Platinum oxide nanoparticles were prepared by a simple hydrothermal route and chemical reduction using carbohydrates (fructose and sucrose) as the reducing and stabilizing agents. In comparison with other metals, platinum oxide has less environmental pollution. Therefore, Pt is considered an appropriate candidate to deal with environmental pathogens. The crystallite size of these nanoparticles was evaluated from X-ray diffraction, atomic force microscopy, and transmission electron microscopy (TEM) and was found to be 10 nm, which is the demonstration of EM bright field and transmission electron microscopy. The effect of carbohydrates on the morphology of the nanoparticles was studied using TEM. The nanoparticles were administered to the Pseudomonas stutzeriand Lactobacillus cultures, and the incubation was done at 37oC for 24 h. The nano composites exhibited interesting inhibitory as well as bactericidal activity against P. stutzeri and Lactobacillus species. Incorporation of nanoparticles also increased the thermal stability of the carbohydrates. The results of this paper showed that carbohydrates can serve as a carrier for platinum oxide nanoparticles, and nano composites can have potential biological applications.

ZnO is a promising member of the semiconducting materials of II-VI group. ZnO nanocrystals have shown potential applications in various novel technologies. In the present investigation of ZnO nanocrystals, a novel chemical route using Zinc acetate as organic precursor is being reported. ZnO nanocrystals were characterized using X-ray diffraction, scanning electron microscopy UV-visible (UV–vis) spectroscopy, and photoluminescence measurements.The X-ray diffraction studies reveal the typical hexagonal structure of ZnO nanocrystals along the preferred orientation of (101) and (100) planes. The optical bandgap of ZnO nanocrystals was found to be 3.50 eV from the absorbance spectrum, which is higher than that of the bulk ZnO material. A blueshift of 21 nm is observed in the excitonic transitions, which clearly indicates the formation of ZnO nanocrystals. Photoluminescence spectroscopy of the ZnO nanocrystals showed a strong emission peak at 365 nm near the band edge along with a weak green-yellow emission peak spanning the range of 450 to 600 nm. The blueshifting was also observed in the photoluminescence spectrum, in accordance with the UV–vis spectroscopy in contrast to the bulk ZnO material.

The hydrothermal synthesis and optical properties of undoped and Sb3+-doped lithium metasilicate and lithium disilicate nanomaterials were investigated. The microstructures and morphologies of the synthesized Li2−2xSb2xSiO3 and Li2−2xSb2xSi2O5 nanoparticles were studied with powder X-ray diffraction and scanning electron microscopy techniques, respectively. The synthesized undoped and doped lithium metasilicate and lithium disilicate nanomaterials, respectively, are isostructural with the standard bulk Li2SiO3 (space group Cmc21) and Li2Si2O5 (space group Ccc2) materials. The electronic absorption and photoluminescence spectra of the synthesized materials are studied. The measured optical properties show dependence on the dopant amounts in the structure.

Here, we report the novel use of the ethonolic leaf extract ofPiper betle for gold nanoparticle (AuNP) synthesis. The successful formation of AuNPs was confirmed by UV-visible spectroscopy, and different parameters such as leaf extract concentration (2%), gold salt concentration (0.5 mM), and time (18 s) were optimized. The synthesized AuNPs were characterized with different biophysical techniques such as transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). TEM experiments showed that nanoparticles were of various shapes and sizes ranging from 10 to 35 nm. FTIR spectroscopy revealed that AuNPs were functionalized with biomolecules that have primary amine group–NH2, carbonyl group, –OH groups, and other stabilizing functional groups. EDX showed the presence of the elements on the surface of the AuNPs. FT-IR and EDX together confirmed the presence of biomolecules bounded on the AuNPs. Cytotoxicity of the AuNPs was tested on HeLa and MCF-7 cancer cell lines, and they were found to be nontoxic, indicating their biocompatibility. Thus, synthesized AuNPs have potential for use in various biomedical applications.