Journal of Nanoscience and Nanotechnology
Seed-Mediated Synthesis of Gold Nanorods: Role of …
Jim Yang Lee Group - National University of Singapore
CTAB (cetyltrimethylammonium bromide) coated manganese ferrite (MnFe2O4), nickel ferrite (NiFe2O4) and zinc ferrite (ZnFe2O4) nanoparticles with crystallite sizes of 23 nm, 15 nm, and 28 nm respectively were successfully synthesized by a facile co-precipitation method. The presence of CTAB on the surface of the nanoparticles was confirmed by the Transmission Electron Microscope (TEM) and Fourier Transform-Infrared spectrum (FT-IR). The magnetic study shows a high saturation magnetization of 46 emu/g (MnFe2O4), 59 emu/g (NiFe2O4) and 55 emu/g (ZnFe2O4) which indicates the Fe-O-Fe super-exchange interaction driven by the synergistic influence of magnetocrystalline anisotropy and cation distribution. The Field Cooling (FC) and Zero Field Cooling (ZFC) curves confirmed the superparamagnetic nature of all the samples. The induction heating study elucidates the efficiency of heat generation (>42°C) in all samples showing an exceptionally high specific absorption rate (SAR) of 480 Wg-1, 684 Wg-1, 586 Wg-1 at 2 mg/ml in which CTAB-NiFe2O4 nanoparticles shows the highest efficiency. This is attributed to the co-dependent factors: size, saturation magnetization and Neelian relaxation loss mechanism. This comparative study discussed on the collaborative influences of structural motifs and magnetic properties that engendered the effectiveness of heat generation making it viable for hyperthermia application.
Self-protective/self-healing coatings are imperative for sustained corrosion protection and to minimise economic losses. The present research focuses on this premise. We report here the synthesis of a series of new effective organic corrosion inhibitors for corrosion protection of the aluminium alloy - AA2024-T3. The synthesized inhibitors were encapsulated in silica nano-containers and doped in GPTMS – Titanium isopropoxide based sol-gel coatings for “on-demand” release of the inhibitor. Anticorrosion behaviour of uncoated and coated coupons was characterized by Electrochemical impedance spectroscopy (EIS). The immersion time for evaluating the sustainability of the coatings in 3.5% NaCl was 168h as per MIL’s specifications. The localized corrosion and dissolution of the intermetallic particles (S & Ө phases) on the aluminium alloy was examined by using field emission scanning electron microscopy attached with energy dispersive X- ray spectroscopy, X-ray photoelectron spectroscopy and 3D profilometry. The acquired results revealed that, the synthesized inhibitors offered sustained corrosion protection to AA2024-T3. The coupons qualified salt spray test as per ASTM standard B117. The mechanism of action appeared to be formation organic thin layer of insoluble complex on the surface, thereby preventing the dislodgement of the inter-metallics and pitting corrosion characteristic of the AA2024-T3 alloy.
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Inorganic fertilizers along with high yielding varieties have contributed immensely for success of green revolution. Increasing pressure towards food production globally demands unconscientious fertilizer usage in future as well. Nitrogenous fertilizers are the extensively used fertilizers but also suffer huge losses from agriculture ecosystem due to faster rate of release which is not synchronized with crop demand. Thus resulting in low nitrogen use efficiency. In order to have a sustained release of nitrogen from fertilizer, nanoparticle coated with urea is an effective option. We report urea coated hydroxyapatite based nanofertilizer and its performance on aerobic paddy. In this study hydroxyapatite (HA) nanoparticles were synthesized by adding orthophosphoric acid to calcium hydroxide solution under constant vigorous stirring. Saturated urea solution was added to the HA particle suspension and was stirred continuously for 12 hours for surface modification. The urea modified HA particles were washed and dried at 65ºC. Hydroxyapatite nanoparticles (HA) and urea coated hydroxyapatite nanoparticles (UHA) were characterized using Dynamic Light Scattering (DLS), Scanning Electron Microscope (SEM), Powder X-ray Diffraction (PXRD) and Fourier Transform Infrared (FTIR) Spectroscopy. Nitrogen content of UHA was analyzed using Kjeldahl method. Nitrogen content of UHA particles was found to be 36% and Zeta potential was 165.0 mV indicating stable nanodispersion. PXRD pattern of UHA particles indicated the presence of peaks due to hydroxyapatite and urea. SEM images of UHA particles exhibited oblong structures resembling rice grains with diameter less than 90 nm. FTIR spectroscopy showed prominent peaks around γmax/cm–1 1041 indicating phosphate group in hydroxyapatite and γmax/cm–1 3336 and 3432 indicating presence of urea. Synthesized nanofertilizer was evaluated on aerobic paddy under completely randomized design and was compared with recommended dose of conventional urea (100kgN/ha) in aerobic paddy. Nanofertilizer at 25% of recommended dose recorded highest grain yield. Nanofertilizer@ 50% dose showed similar performace to 100% dose of conventional urea. The results indicate amount of fertilizer application into soil can be reduced than regular dosage with nanofertilizer without affecting the yield. This will reduce environmental pollution of water and soil without compromising agricultural production.
Nanocomposites: synthesis, structure, properties and …
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Encyclopedia of Chemical Processing and Design
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