International Journal of Nanoscience

CaS nanoparticles have been synthesized by microwave irradiation, using Ca(Ac)₂ as Ca-precursor, and thioacetamide as S-source. The as-prepared sample has a uniform morphology and high purity. After heat treatment similar results were observed. Synthesized nanoparticles were characterized by X-ray powder analysis (XRD), field emission scanning microscopy (FESEM), high resolution transmission electron microscopy (TEM), and UV-Vis absorption spectroscopy. X-ray diffraction patterns suggest the formation of single cubical face of CaS having average particle size of 22 nm. HRTEM micrographs reveal well dispersed cubical morphology with a size distribution of 18–30 nm. Ultraviolet-visible (UV-Vis) spectroscopy shows absorption at 268 nm. In nutshell, microwave irradiation is proved to be a convenient, efficient and environmental-friendly one-step route to synthesize nanoparticles.

Recently it has been elaborated an approach to decrease depth of diffusive- and implanted-junction rectifiers by manufacturing the rectifiers in a semiconductor heterostructure and optimization of annealing of dopant and radiation defects. At the same time with decreasing of depth of the p-n-junction homogeneity of dopant distribution in doped area increases. In this paper we analyzed possibility to increase both the effects at one time by radiation processing of materials of the heterostructure.

In this experimental investigation, the heat transfer coefficients of a shell and helically coiled tube heat exchanger using Al₂O₃/water nanofluid under laminar flow condition were studied. The Al₂O₃ nanoparticles were characterized by X-Ray diffraction (XRD). The Al₂O₃/water nanofluid at 0.1%, 0.4% and 0.8% particle volume concentration were prepared by using two step method. The prepared nanofluid was characterized by scanning electron microscope (SEM). It is observed that the overall heat transfer coefficient, inner heat transfer coefficient and experimental inner Nusselt number increase while increasing particle volume concentration and increasing inner Dean number. The enhancement of overall heat transfer coefficient was found to be 7%, 16.9% and 24.2% at 0.1%, 0.4% and 0.8% Al₂O₃/water nanofluid respectively when compared with water. The enhancement of tube side experimental Nusselt number was found to be 17%, 22.9% and 28% at 0.1%, 0.4% and 0.8% particle volume concentration of Al₂O₃/water nanofluid respectively when compared with water at fixed Dean number. The tests were conducted in the range of 1600 < De < 2700, and 5200 < Re < 8600 under laminar flow condition and counter flow configuration. These enhancements are due to higher thermal conductivity of nanofluid while increasing particle volume concentration and Brownian motion of nanoparticles. It is studied that there is no negative impact on formation of secondary flow and mixing of fluid when nanofluid passes through the helically coiled tube.

The advantage of doping of TiO₂ with copper has been utilized for enhanced degradation of pesticide under visible light irradiation. The sol–gel method has been undertaken for the synthesis of copper-doped TiO₂ by varying the dopant loadings from 0.25 wt.% to 1.0 wt.% of Cu²⁺. The doped samples were characterized by UV-Visible Diffuse Reflectance Spectroscopy (DRS), N₂ adsorption–desorption (BET), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectrometry (EDS). The photocatalytic activity of the catalyst was tested by degradation of dichlorvos under visible light illumination. The results found that 0.75 wt.% of Cu²⁺ doped nanocatalysts have better photo catalytic activity than the rest of percentages doped, undoped TiO₂ and Degussa P25. The reduction of band gap was estimated and the influence of the process parameters on photo catalytic activity of the catalyst has been explained.

Nano-hydroxyapatite (HA) was synthesized by a wet chemical reaction using powdered sea shells (CaO) as starting material which was converted to calcium hydroxide (Ca(OH)₂) and subsequently reacted with phosphoric acid (H₃PO₄). Initially raw sea shells (CaCO₃) were thermally converted to amorphous calcium oxide by heat treatment. Two sets of experiments were done; in the first experiment, HA powder was dried in an electric furnace and in the second experiment, the reactants were irradiated in a domestic microwave oven followed by microwave drying. In each set of experiments, the concentrations of the reactants were decreased gradually. HA was synthesized by slow addition of phosphoric acid (H₃PO₄) in to calcium hydroxide (Ca(OH)₂) maintaining the pH of the solution at 10 to avoid the formation of calcium deficient apatites. In both the experiments, Ca:P ratio of 1.67 was maintained for the reagents. The synthesized samples showed X-ray diffraction (XRD) patterns corresponding to hydroxyapatite. The wet chemical process with furnace drying resulted in HA particles of size 7–34 nm, whereas microwave irradiated process yielded HA particles of size 34–102 nm as evidenced from XRD analyses. The above experimental work done by wet chemical synthesis to produce HA powder from sea shells is a simple processing method at room temperature. Microwave irradiation leads to uniform crystallite sizes as evident from this study, at differing concentrations of the reactants and is a comparatively easy method to synthesize HA. The high resolution scanning electron microscopy (HRSEM)/transmission electron microscopic (TEM) analyses revealed the characteristic rod-shaped nanoparticles of HA for the present study.

Zinc Oxide (ZnO) nanowires were synthesized on the Si substrates by carbothermal evaporation of ZnO + C at elevated temperatures. The syntheses were carried out at different temperatures from 750°C to 950°C. Characterizations of layers were performed to study the effect of synthesis temperature on morphology, crystal structure and electrical behavior of fabricated nanowires. The physical characterization was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDAX) methods. SEM micrograph of layers revealed that the samples grown at the lower temperatures have better quality. However, below 800°C the growth of nanowires was stopped. So the 800°C was concluded to be the optimum temperature for growth of high quality nanowires by proposed system. By recording the conductivity variations as a function of inverse temperature, 1/T, the semiconductor property of the samples was verified. It is demonstrated that two distinct factors affect the electrical conductivity of layers, which are due to the bulk and grain boundary. We experimentally proved that the activation energy corresponding to grain boundary is higher than that of the bulk. As another result we have established for the first time that by increasing synthesis temperatures, both activation energies shift to higher values.

Chitin nanofibers (CNFs)-Au(0) nanoparticles (Au NPs) blends in dispersion, flakes and thin film or sheet forms were first prepared by mixing pre-organized Au NPs prepared in triblock copolymer with diluted CNFs suspension. Water soluble polymer triblock copolymer poly (methyl vinyl ether, PMVE) in the amount 0.6 wt.% was used to prepare NPs and 0.12 wt.% net chitin content was used as CNFs suspension to prepare the blended composite. Au NPs of size 4.4 nm (σ = 1.2) were obtained when Au salt (HAuCl₄⋅3H₂O (hydrogen tetrachloroaurate (III) trihydrate) was reduced by 5 equivalents of NaBH₄. PMVE polymer acted as a stabilizing or capping agent for pre-organized NPs. Completion of reaction was fast, all salt reduced to metallic form in just 15 min after the addition of NaBH₄. CNFs (1 wt.% chitin) which was used to prepare CNFs-Au NPs blend composite were prepared from crab shell in never dried acidic condition by established combination of chemical and mechanical processes that gave 25–40 nm width and high aspect ratio CNFs. When polymer capped Au NPs mixed with CNF suspension, all Au NPs and 56% polymer were mass transferred from water phase to entangle with more polar moieties of CNFs-water suspension as no trace of Au NPs were noticed in water–polymer mother liquor after blending with CNFs suspension. Particles size of CNFs-Au NPs composite was measured by employing TEM, SAXS and SEM techniques. CNFs-Au NPs composite were characterized in solution and compressed dried sheet form by recording digital images, UV-vis and XRD spectroscopies. CNFs-Au NPs suspension had antibacterial activity against gram positive bacteria S. aureus.

Previously, we demonstrated the selective NIR-mediated ablation of tumor cells in vitro using pristine single-walled carbon nanotubes (SWNTs) with adsorbed tumor-targeting ligands and carboxylated SWNTs with covalently-attached ligands. The covalent approach is advantageous in ensuring that protein ligands remain associated with the NIR-absorbing SWNTs in biological matrices and the noncovalent approach has the advantage of enabling SWNT functionalization without perturbation of the SWNT lattice and photothermal properties. Herein, we compare the ability of moderately-carboxylated (~ 4 at.% carboxylic acid groups) and pristine SWNT materials to absorb 808 nm radiation and convert it to heat. Under conditions of a constant 808 nm laser power density, the approach involved measuring the temperature of aqueous dispersions of protein-coated SWNTs as a function of the irradiation time. Nearly identical temperature profiles were observed for dispersions of moderately-carboxylated and pristine SWNTs possessing matched 808 nm optical densities and equivalent concentrations of carbonaceous species (i.e., SWNTs and amorphous carbon impurities). The results indicate that the amount of carbonaceous species in purified dispersions of protein-coated SWNTs is more important for converting absorbed 808 nm radiation into heat than whether or not the SWNTs were moderately carboxylated, and that moderately-carboxylated SWNTs could be the SWNT-material of choice for the targeted photothermal ablation of tumor cells.

We have analyzed the one-dimensional (1D) ZnO nanocrystals in its wurtzite (B4); zinc-blende (B3) and rocksalt (B1) type phases, by means of density functional theory (DFT) calculations. The energetic stability of nanocrystal has been analyzed using Revised Perdew–Burke–Ernzerhof (revPBE) type parameterized GGA potential. The B3 type phase is most stable amongst other phases of nanocrystals. The computation of ground state properties for all the phases of ZnO nanocrystals finds that the bulk modulus are smaller than their bulk counterpart, in turn softening the material at reduced dimensions. The electronic band structure analysis confirms the semiconducting nature of B4 type phase whereas other two are metallic.

Fe₇S₈ nanorods have been successfully synthesized using a chemical evaporation method. X-ray diffraction pattern showed that the as-prepared products were Fe₇S₈ with no impurity phase. The results of scanning electron microscopy indicated that the samples synthesized at 750°C and 900°C were rod and sheet-like, respectively. The magnetic properties of the iron sulfide nanorods were measured over a wide temperature range (4 K–750 K) using a quantum design vibrating sample magnetometer. It was found that the nanorods were ferromagnetic with the Curie temperature of about 581 K. The Mössbauer spectra showed that the iron sulfide nanorods consisted of hexagonal pyrrhotites, whose spectra were asymmetrical according to correlation between the isomer shift and the hyperfine field.