International Journal of Nanoscience

The aim of this work is to present the results obtained for the synthesis of Pd NPs by the modified-polyol method with Vulcan XC-72R as support. Two different ways were used to synthesize catalysts: (a) Maintaining the initial pH of the synthesis equal to 12 and changing the initial concentration of the precursor to obtain an overall 10 wt.% nominal Pd load; (b) Fixing the initial concentration of the precursor at 2mM whilst changing the initial pH of the synthesis at different values to obtain an overall 10wt.% nominal Pd load. Catalysts were characterized using X-ray diffraction (XRD), Transmission electron microscopy (HRTEM, TEM, STEM) and cyclic voltammetry (CV). This work shows that the density of NPs generated during the nucleation process is a consequence of the fluctuation of the concentration. The standard deviation of the diameters varied linearly with the mean volume for values between 0.5mM and 6mM, demonstrating that there was a clear separation between nucleation and growth processes. The final mean diameter strongly depends on the initial pH of the synthesis for the same initial concentration of the precursor; mean diameters are smaller for basic media. The analysis of the voltammograms allowed the determination of the coverage fraction of oxygen on Pd, obtaining a value of 0.51 with a structure type $c(2\times 2)$. The coverage value found for CO is 0.71 with a structure type $p(2\times 2)-3$CO.

Silver nanoparticles have been synthesized from Poly(N-vinylpyrrolidone) (PVP)/ethanol solutions, and six different PVP to silver nitrate weight ratios (PVP:AgNO₃) are studied in reduction of silver nitrate in ethanol with the presence of PVP as a stabilizer. The produced silver nanoparticles showed strong plasmon resonance peak centered at around 405nm in UV-Vis spectra. The particle morphologies were also examined and compared under secondary electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersion X-ray spectroscopy (EDX) was utilized to determine the formation of silver nanoparticles. We found that the particle size and morphology were strongly dependent on the PVP:AgNO₃ weight ratio. The average size of silver particles decreased from 19.25nm to 10.03nm as the weight ratio of PVP:AgNO₃ increased from 1:1 to 20:1.

In this paper, we analyze the effects of temperature dependence of energy bandgap on $I-V$ characteristics in some carbon nanotube field effect transistors (CNTFETs) models proposed in literature in order to identify the one more suitable for computer aided design (CAD) applications. At first we consider a compact, semi-empirical model, already proposed by us, performing $I-V$ characteristic simulations at different temperatures. Our results are compared with those obtained with the Stanford-Source virtual carbon nanotube field-effect transistor model (VS-CNFET), obtaining $I-V$ characteristics comparable, but with lower CPU calculation time.

In this work, novel monolithic carbon aerogels obtained by using a polymer template method were characterized and evaluated for their applications in the hydrogen and deuterium adsorption capacity. The properties (i.e., surface area, pore size distribution, hydrogen and deuterium adsorption capacities, etc.) of the carbon aerogels were affected by the polymer templates. The results showed that the carbon aerogel with the molar ratio of polyacrylic acid (PAA) to zinc chloride (ZnCl₂) being 0.75:40 was featured the highest surface area (1806 m²/g) and had the highest hydrogen adsorption capacity. Moreover, the deuterium adsorption capacity of the carbon aerogel was to be further elucidated.

Nanosilicon is currently under intensive research owing to its extremely promising properties, particularly in photonics domain. However, the photoluminescence (PL) mechanism of silicon nanocrystal remains unclear. We propose, in this paper, a simple method to investigate the PL properties of silicon nanoparticles by exposing the nanoparticles directly to the solvents. The interaction between the nanoparticles and different solvents allows us to assume that not only the quantum size effect but also the surface defect states play a critical role in the PL mechanism, especially at high energy region. This can be confirmed by the results of Transmission Electron Microscopy, FTIR and Raman Spectroscopy.

In this project, nanocomposite films were prepared with different Titanium dioxide (TiO₂) percentages. Properties of polycarbonate (PC) and PC–TiO₂ nanocomposite films were studied by X-ray diffraction (XRD) analysis and Fourier transform infrared (FTIR) spectroscopy. The structure of samples was studied by XRD. The mechanical properties of PC–TiO₂ nanocomposite films were investigated by conducting tensile tests and hardness measurements. Thermal stability of the nanocomposites was studied by thermogravimetric analysis (TGA) method. The elastic modulus of the composite increased with increasing weight fraction of nanoparticles. The microhardness value increases with increasing TiO₂ nanoparticles. The results of tensile testing were in agreement with those of micro-hardness measurements. In addition, TGA curves showed that nanocomposite films have higher resistance to thermal degradation compared to polycarbonate. There are many reports related to the modification of polycarbonate films, but still a systematic study of them is required.

The Cuprous oxide (CuO) thin film was prepared on texturized Si wafer by a simple sol–gel method to fabricate p-CuO/n-Si heterojunction photoelectric device. The novel sol–gel method is very cheap and convenient. The structural, optical and electrical properties of the CuO film were studied by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), UV–Vis spectrophotometer and Hall effect measurement. A good nonlinear rectifying behavior is obtained for the p-CuO/n-Si heterojunction. Under reverse bias, good photoelectric behavior is obtained.

Carbonaceous nanotubes with a calculated specific heat of 710J K${}^{-1}$ Kg${}^{-1}$, and an outer diameter of 58nm, made by a micro-thermal reaction, using polypyrrole nanotubes precursor is presented here. Three degradation stages from the thermal curves are identified. We observe a decomposition temperature at 371${}^{\circ }$C that relates to the presence of amorphous carbon on samples for the first time in this material. Also, it is identified that gradual decomposition of the fragments provides a different kind of residue percentage in the range 48–32% that is related to stirring speed used in each synthesis. It is worthy to note that electron transmission microscope images of carbonaceous nanotubes present defects as well, wherein we identify chloride and nitrogen as doped agents. Finally, results of nanotubes using Infrared, Raman spectrometry analysis, scanning electron microscopy and electron diffraction are presented here.

Covalent cross-linking of enzymes to magnetite (Fe₃O₄) nanoparticles (MNPs) is one of the useful enzyme immobilization methods which provides repeated use of the catalyst, facilitates enzyme separation from the reaction mixture, and sometimes improves biocatalysts stability. The aim of this study was to immobilize $\alpha$-amylase onto MNPs via covalent attachment using carbodiimide (CDI) molecules. MNPs were synthesized by the co-precipitation method. The size and the structure of the particles were characterized by X-ray diffraction and transmission electron microscopy. The effects of different operational conditions of direct $\alpha$-amylase binding on MNPs in the presence of CDI were investigated by using the shaking method. Fourier transform infrared spectroscopy was used to confirm the success of immobilization. The optimum conditions and catalytic properties of immobilized $\alpha$-amylase were also evaluated. The efficiency of immobilization and the residual activity of the immobilized $\alpha$-amylase were dependent on the mass ratio of MNPs: CDI: $\alpha$-amylase and the immobilization temperature. The optimum pH for the free and immobilized amylase was 6. The free and immobilized $\alpha$-amylase showed maximum activity at 20${}^{\circ }$C and 35${}^{\circ }$C, respectively. The immobilized $\alpha$-amylase was more thermostable than the free one. The retained activity for free $\alpha$-amylase after 19 storage days was 57.7% whereas it was 100% for the immobilized $\alpha$-amylase. In repeated batch experiments, the immobilized $\alpha$-amylase retained a residual activity of 45% after 11 repeated uses. The $K_m$ and $V_{\mathrm{\text{max}}}$ values for the immobilized enzyme were larger than those of the free enzyme. The immobilization of $\alpha$-amylase on MNPs using CDI improves its stability and reusability.

Low-density porous tin monolith with the pteridophyta leaf-like structure was fast fabricated by a facile route via the electrochemical deposition process via hydrogen bulb dynamics templates within less than 1min. The samples were characterized by scanning electron microscope, X-ray diffraction and so on. The results indicated that the deposited tin porous structure could be easily controlled to form film or monolith by adjusting the tin precursor concentration and surfactant content.

Nanostructured zero-valent iron (NSZVI) particles were synthesized by the method of ferric ion reduction with sodium borohydride with subsequent drying and passivation at room temperature in technical grade nitrogen. The obtained sample was characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and dynamic light scattering studies. The prepared NSZVI particles represent 100–200nm aggregates, which consist of 20–30nm iron nanoparticles in zero-valent oxidation state covered by thin oxide shell. The reactivity of the NSZVI sample, as the removal efficiency of refractory azo dyes, was investigated in this study. Two azo dye compounds, namely, orange G and methyl orange, are commonly detected in waste water of textile production. Experimental variables such as NSZVI dosage, initial dye concentration and solution pH were investigated. The kinetic rates of degradation of both dyes by NSZVI increased with the decrease of solution pH from 10 to 3 and with the increase of NSZVI dosage, but decreased with the increase of initial dye concentration. The removal efficiencies achieved for both orange G and methyl orange were higher than 90% after 80min of treatment.

Silver oxide nanoparticle can be synthesized by chemical and biological methods. Biological synthesis has emerged as an exciting, ecofriendly approach. However, the process tends to be slow when we consider its industrial applicability. The development of reliable method for rapid synthesis of nanoparticles is one of the significant zones of interests in current nanotechnological research. In this paper, optimization of physiochemical parameters for rapid silver oxide nanoparticle synthesis using Bacillus thuringiensis SSV1 culture supernatant has been elucidated. Spherical-shaped silver oxide nanoparticles with an average particle size of 30nm were obtained. The cytotoxic effect of silver oxide nanoparticles was studied against HepG2 and Chang liver cell lines by MTT assay. These nanoparticles showed dose-dependent response on HepG2 (IC${}_{50}=0.47\mu$g/mL) and Chang liver cells (IC${}_{50}=1.11\mu$g/mL).

Due to exciting size-dependent chemical and physical properties, nanoscale materials have extensive range of applications compared with microstructural particles. CuO nanoparticles are very important among transition metal oxides because of their large number of applications. Quantum dots (QDs) of CuO (copper oxide) were prepared by the innovative ultrasonication method. Ultrasonic sound is used in this synthesis method to synthesize QDs of copper oxide. Structural and optical properties were studied in this research work. X-ray diffraction was used to study the formation of structural phase CuO QDs and found to be single phasic without any impurity. Transmission electron microscopic measurements were performed to study the morphology of QDs of CuO, which confirms spherical QDs with an average diameter of $\sim$4nm. In optical studies, absorption spectra of the CuO were analyzed by using UV–visible spectroscopy.

Heat exchanger plays an essential part in industrial sector in transferring the heat energy. Heat is exchanged between fluids in convection and conduction mode through the walls of the heat exchanger. If the heat transfer medium has low thermal conductivity, it will greatly limit the efficiency of the heat exchanger. Whenever the system acts subjected to an increase in the heat load, heat fluxes caused by more power and smaller size, cooling is one of the technical challenges faced by the industries. The objective of this research work is to evaluate the overall heat transfer coefficient through an experimental analysis on the convective heat transfer and flow characteristics of a nanofluid. In our experiment, the nanofluid consists of water and one percentage volume concentration of Al₂O₃-water nanofluid flowing through parallel and counter flow in shell and tube heat exchangers. About 50nm diameter of Al₂O₃ nanoparticles was used in this analysis and found that the overall heat transfer coefficient and convective heat transfer coefficient of nanofluid were slightly higher than those of the base liquid at same mass flow rate and inlet temperature. Here, there are three samples of dissimilar mass flow rates, which have been identified for conducting the experiments and their results are continuously monitored and reported. Finally, the observed results through an experimental investigation were presented and concluded that the enhancement of overall heat transfer coefficient is likely to be feasible by means of increasing the mass flow rate of base fluid and prepared nanofluid on the proportional basis.