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Applied Nanoscience (v.1, #4)
Quick single-step mechanosynthesis of ZnO nanorods and their optical characterization: milling time dependence by Soumen Dhara; P. K. Giri (pp. 165-171).
We report on the growth of ZnO nanorods (NRs) by a quick single-step mechanochemical process and investigated the milling time dependence on the structural and optical properties of the ZnO NRs. Mechanochemical reactions are carried out in a planetary ball mill for the time durations ranging from 30 min to 5 h. XRD and TEM studies revealed wurtzite structure of the as-grown ZnO NRs with length of several hundreds of nanometers to few micrometers after 30 min of reaction. Average diameter of the as-grown ZnO NRs decreases from 40 to 15 nm with increasing reaction time. Micro-Raman spectra show redshift in the characteristic Raman modes, indicating presence of milling induced strain. As-grown NRs show blueshift in the excitonic absorption peak with increasing milling time due to decrease in size and induced strain. Room temperature photoluminescence (PL) spectra show strong band-edge related UV emission and other three major emission peaks, two in the UV-blue region and one at the visible region. Post-growth annealing of the as-grown ZnO NRs completely eliminates the defect related visible PL band. Low-temperature PL studies show an additional sharp peak related to donor-bound excitonic transition, revealing the n-type nature of the as-grown NRs.
Keywords: ZnO Nanorods; Single-step mechanosynthesis; Photoluminescence; Raman
Analysis of a nano-porous multi-layer film for thermal radiation barrier coatings by Kaushik Das; Dimitris C. Lagoudas; John D. Whitcomb (pp. 173-188).
A highly reflective thermal radiation barrier coating (TRBC) made of a multi-layer film is studied for high temperature applications. The multi-layer film with a periodic microstructure consisting of cylindrical nano-pores acts a photonic band gap (PBG) crystal. The coating is constructed such that pores are arranged periodically along the in-plane directions and axes of the pores are parallel to the thickness direction. The pore diameter is varied periodically through the thickness to form a multi-layer film of alternating low and high porosities. The primary motivation behind considering this microstructure is that it can be fabricated from aluminum dioxide, which remains stable at high temperatures. The reflectivity of a single layer with uniform porosity is computed by numerically solving Maxwell’s equations, by considering both the microstructure explicitly and a homogenized layer to gain insights into the effect of pore size on the reflectivity of the nano-porous layer. Based on the study of the single layer, two microstructures with different arrangements of pores are designed to exploit the effect of microstructure to widen the band gap of the PBG crystal and to increase the reflectivity of the TRBC. Results of numerical simulations reveal that a wider band gap and higher reflectivity can be achieved by making the inter-pore distance of alternate layers of the multi-layer film comparable to the wavelength of the incident thermal radiation. A TRBC, which is made of a microstructure with a wider band gap and has increased reflectivity, will reflect a greater amount of incident heat energy over a wider range of frequencies.
Keywords: Thermal radiation barrier coating; Multi-layer film; Anodic aluminum dioxide; Nanostructured material
Amine functionalized TiO2–carbon nanotube composite: synthesis, characterization and application to glucose biosensing by Mahboubeh Tasviri; Hossain-Ali Rafiee-Pour; Hedayatollah Ghourchian; Mohammad Reza Gholami (pp. 189-195).
The synthesis of amine functionalized TiO2-coated multiwalled carbon nanotubes (NH2-TiO2-CNTs) using sol–gel method was investigated. The synthesized nanocomposite was characterized with XRD, FTIR spectroscopy, BET test and SEM imaging. The results demonstrated a unique nanostructure with no destruction of the CNTs’ shape. In addition, the presence of amine groups on the composite surface was confirmed by FTIR. This nanocomposite was used for one-step immobilization of glucose oxidase (GOx) to sense glucose. The result of cyclic voltammetry showed a pair of well-defined and quasi-reversible peaks for direct electron transfer of GOx in the absence of glucose. Also, the result of electrochemical impedance spectroscopy indicated that GOx was successfully immobilized on the surface of NH2-TiO2-CNTs. Furthermore, good amperometric response showed that immobilized GOx on the NH2-TiO2-CNTs exhibits exceptional bioelectrocatalytic activity toward glucose oxidation.
Keywords: Carbon nanotube; TiO2 ; Glucose oxidase; Bioelectrocatalysis
Facile synthesis and catalytic studies of CdS–manganese oxide nanocomposite by R. Kannan; K. Karunakaran; S. Vasanthkumar (pp. 197-203).
Cadmium sulfide (CdS)–manganese oxide (MO) nanocomposite was synthesized by the ion exchange and ultrasonic irradiation methods. The synthesized nanocomposite was characterized by FTIR, powder X-ray diffractrogram (XRD), UV–Vis diffused reflectance spectra (UVDRS), photoluminescence (PL), transmission electron microscope (TEM) and energy dispersive X-ray analysis (EDX). The experimental results confirm the formation of CdS–MO nanocomposite. The luminescence of the nanocomposite exhibits a notable blue shift. The TEM results disclosed the size of the nanocomposite to be within 10–20 nm. The catalytic activity of the nanocomposite was evaluated by the degradation of methylene blue (MB) under visible light.
Keywords: Cadmium sulfide; Manganese oxide; Ion exchange; Ultrasonication; Nanocomposite
Synthesis and evaluation of silver nanoparticles material for solid phase extraction of cobalt from water samples by Mostafa Khajeh; Esmael Sanchooli (pp. 205-209).
In this study, a new solid phase extractor, nano-scale silver particles were synthesized. The silver nanoparticle-based solid phase extraction was used for separation and preconcentration of the trace amount of cobalt ion from various water samples prior to its determination by flame atomic absorption spectrometry. The effects of various parameters, including pH, amount of complexing agent [1-(2-pyridylazo)-2-naphthol] (PAN), flow rates of solution and eluent, type and least amount of the eluent for elution of the cobalt from silver nanoparticles were studied and optimized. Under the optimum conditions, the detection limit of this procedure was 0.78 μg L−1, and the relative standard deviation (RSD%) was 3.1% (n = 10, c = 20 μg L−1). This method was applied to the determination of cobalt in water samples.
Keywords: Cobalt; Silver nanoparticle; Solid phase extraction; Water samples
Growth and characterization of germanium nanowires on a flexible aluminium substrate by electron beam evaporation by R. Rakesh Kumar; K. Narasimha Rao; A. R. Phani (pp. 211-217).
For the first time, Germanium (Ge) nanowires have been grown on a gold (Au) coated flexible aluminum (Al) foil substrate in high vacuum (1 × 10−5 mbar) by electron-beam evaporation of germanium using the vapor–liquid–solid mechanism at a substrate temperature of 380°C. The grown nanowires have been analyzed for their structural, morphological and chemical properties by employing standard techniques X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy, respectively. X-ray diffraction measurements revealed the formation of cubic Ge phase highly oriented in (111) reflection in plane with the Al foil substrate. The morphological observations by SEM have shown the randomly grown nanowires with an average length and diameter of 600 ± 50 and 100 ± 10 nm, respectively, for a deposition time of 30 min. TEM investigation revealed single crystalline nanowires with free of defects. The wettability studies by contact angle measurement have confirmed the hydrophobic nature of the Ge NWs film surface with contact angle for water 110° ± 1°. The growth mechanism of Ge nanowires on Al foil substrate has also been discussed.
Keywords: Ge nanowires; VLS growth mechanism; Scanning electron microscopy; Flexible substrate; Hydrophobicity; Thin films; e-beam evaporation
Enhanced encapsulation of metoprolol tartrate with carbon nanotubes as adsorbent by Kevin Garala; Jaydeep Patel; Anjali Patel; Abhay Dharamsi (pp. 219-230).
A highly water-soluble antihypertensive drug, metoprolol tartrate (MT), was selected as a model drug for preparation of multi-walled carbon nanotubes (MWCNTs)-impregnated ethyl cellulose (EC) microspheres. The present investigation was aimed to increase encapsulation efficiency of MT with excellent adsorbent properties of MWCNTs. The unique surface area, stiffness, strength and resilience of MWCNTs have drawn much anticipation as carrier for highly water-soluble drugs. Carbon nanotubes drug adsorbate (MWCNTs:MT)-loaded EC microspheres were further optimized by the central composite design of the experiment. The effects of independent variables (MWCNTs:MT and EC:adsorbate) were evaluated on responses like entrapment efficiency (EE) and t 50 (time required for 50% drug release). The optimized batch was compared with drug alone EC microspheres. The results revealed high degree of improvement in encapsulation efficiency for MWCNTs:MT-loaded EC microspheres. In vitro drug release study exhibited complete release form drug alone microspheres within 15 h, while by the same time only 50–60% drug was released for MWCNTs-impregnated EC microspheres. The optimized batch was further characterized by various instrumental analyses such as scanning electron microscopy, powder X-ray diffraction and differential scanning calorimetry. The results endorse encapsulation of MWCNTs:MT adsorbate inside the matrix of EC microspheres, which might have resulted in enhanced encapsulation and sustained effect of MT. Hence, MWCNTs can be utilized as novel carriers for extended drug release and enhanced encapsulation of highly water-soluble drug, MT.
Keywords: Multi-walled carbon nanotubes; Central composite design; Ethyl cellulose; In vitro drug release; Microspheres
Antibacterial potential of silver nanoparticles against isolated urinary tract infectious bacterial pathogens by Samuel Jacob Inbaneson; Sundaram Ravikumar; Nachiappan Manikandan (pp. 231-236).
The silver nanoparticles were synthesized by chemical reduction method and the nanoparticles were characterized using ultraviolet–visible (UV–Vis) absorption spectroscopy and X-ray diffraction (XRD) studies. The synthesized silver nanoparticles were investigated to evaluate the antibacterial activity against urinary tract infectious (UTIs) bacterial pathogens. Thirty-two bacteria were isolated from mid urine samples of 25 male and 25 female patients from Thondi, Ramanathapuram District, Tamil Nadu, India and identified by conventional methods. Escherichia coli was predominant (47%) followed by Pseudomonas aeruginosa (22%), Klebsiella pneumoniae (19%), Enterobacter sp. (6%), Proteus morganii (3%) and Staphylococcus aureus (3%). The antibacterial activity of silver nanoparticles was evaluated by disc diffusion assay. P. aeruginosa showed maximum sensitivity (11 ± 0.58 mm) followed by Enterobacter sp. (8 ± 0.49 mm) at a concentration of 20 μg disc−1 and the sensitivity was highly comparable with the positive control kanamycin and tetracycline. K. pneumoniae, E. coli, P. morganii and S. aureus showed no sensitivity against all the tested concentrations of silver nanoparticles. The results provided evidence that, the silver nanoparticles might indeed be the potential sources to treat urinary tract infections caused by P. aeruginosa and Enterobacter sp.
Keywords: Antibacterial sensitivity; Disc diffusion assay; Silver nanoparticles; UTI
Controlling the optimum dose of AMPTS functionalized-magnetite nanoparticles for hyperthermia cancer therapy by Yosefine Arum; Youngjin Song; Junghwan Oh (pp. 237-246).
Magnetic hyperthermia has been used for many years to treat a variety of malignant tumors. One of the problems in magnetic hyperthermia is the choice of the correct particle concentration to achieve a defined temperature increase in the tumor tissue. In this study, we evaluated magnetic heat distribution induced by Fe3O4-APTMS magnetic nanoparticles in agar tissue phantom when it subjected to the AC magnetic filed. Using the correct nanoparticle dosage and considering their specific loss power, it is possible to estimate the efficiency of this therapeutic method. The experimental data were compared with a computer-based model, which were created using COMSOL Multiphysics to simulate the heat dissipation within the tissue for typical configurations of the tumor position as well as particle distribution within the tumor. Heating the cancer cells up to 50°C for 10 min was sufficient for complete cell killing and the heat dose of 19.9 W/gtissue is required for 5-mm tumor. Cell viability assay showed that MNPs exhibited no significant cytotoxicity against HeLa cells. Additionally, it was observed that the FITC-labeled Fe3O4-APTMS MNPs presented high cell biocompatibility and cellular uptake for efficient endocytosis.
Keywords: Hyperthermia; Magnetic nanoparticles dose; SAR; Tumor