International Journal of Nanoscience

The aligned hollow piezoelectric poly (viniliden fluoride) (PVDF) nanofiber was prepared by co-axial electrospinning. Beaded free finer aligned hollow nanofibers have diameter range between 80 and 300 nm. Surface roughness and crystal structure of nanofiber fibers were successfully controlled by using special ionic additives. Furthermore, crystalinity of aligned fiber was evaluated by differential scanning calorimetry. Fourier transforms infra red (FTIR), polarized FTIR, and wide angle X-ray diffraction analysis of fiber showed that the aligned PVDF nanofiber had rich content β-phase crystal structure, and PVDF molecule orientation was along fiber axis. Advanced discussion will be exposed in this paper such as effect of electrospinning speeds on morphology, fiber diameter, crystalinity, and crystal structure of hollow PVDF nanofiber. Piezoelectric nanofiber has great potential application in advanced sensor and actuator.

An experimental program was designed to synthesize and characterize carbon nanotubes (CNTs) and CNTs reinforced polymeric matrix nanocomposites. PMMA, and PS, matrices were adopted for this investigation using different percents of CNTs loading of 0, 1, 3, and 5 and wt%. Morphological characterization was carried out using SEM, TEM, and TEDM microscopy. Mechanical properties were also measured to evaluate the enhancement effect of the CNTs loading percent. The results revealed a remarkable enhancement of the strength and ductility of the matrix material at 3 wt% of reasonably dispersed CNTs.

Carbon nanotube, a new form of carbon element. The arc-discharge method is one of the most efficient techniques for this purpose. Arc-discharge is very simple and has merit to make massive and elongated single wall carbon nanotubes (SWCNTs). Synthesis of SWCNTs are affected with some parameters. In this paper, a predictive model has performed for prediction diameter of SWCNTs based on these factors. In this study, a linear model were established by subjecting the transformed values of independent variables to multiple linear regression (MLR) analysis. In order to examine the correctness of predicted linear model, a predictive artificial neural network (ANN) model was utilized. The optimized models developed by both ANN and regression were validated by comparing the results by a paired t test. These findings demonstrate that ANN provides more accurate prediction and is quite useful in the optimization of diameter SWCNT when compared with the MLR analysis method.

Carbon nanotubes are driving scientific research nowadays. This field has several important directions in basic research, including chemistry, electronic transport, mechanical, and field emission properties. The most eye-catching features of carbon nanotubes are their electronic, mechanical, optical, and chemical characteristics, which open a way to future applications. One of the most important applications of nanotubes based on their properties will be as reinforcements in composite materials. One of the biggest concerns to nanotube industry is the alignment problem which has limited the usage and utilizations of carbon nanotubes in composites. The ability to impose a preferred alignment of carbon nanotubes in a composite will increase the effectiveness of utilizing nanotubes in composite applications. The alignment of nanotubes will maximize the interfacial bonding across the nanotube matrix interface.

In this research, we developed a methodology and a process to align nanotubes in polymer nanocomposites by means of a magnetic field. By doing so, we will get a very strong nanocomposite that can be used in the composites industry. The proposed mechanism aims at aligning the carbon nanotubes by means of nanomagnetic particles that are adsorbed on the nanotube surfaces and by applying an external magnetic field. SEM analysis have shown that nanomagnetic particles with the assistance of the magnetic field were able to align the carbon nanotubes in the desired direction.

Cu–Al₂O₃ metal matrix nanocomposite powder has been synthesized from CuO and Al powders using high energy planetary fast milling. Mechanical alloying was used to produce 20% Vol. Alumina as a reinforcement phase in copper matrix. Reactive milling between Cu (Al) solid solution and CuO powders lead to formation of Cu–Al₂O₃ metal matrix composite. To obtain Cu (Al) solid solution, Cu and Al powders with Cu:Al atomic ratio of six were mechanically alloyed for 50 h.

XRD analysis showed that during the reaction of Cu (Al) solid solution and CuO, Al solute is extracted from Cu (Al) solid solution and reacted with oxygen of CuO to form alumina particles while copper turning back to pure Cu. Presence of alumina particles with sizes smaller than 50 nm was observed in TEM micrographs.

α-Fe₂O₃ nanoparticles were obtained by a mechanical alloying of micrometer-sized powder at different milling times. Samples were characterized by X-ray powder diffraction, scanning electron microscope (SEM), Mössbauer spectrometry, and vibrating sample magnetometer (VSM). A qualitative and quantitative phase analyses using the Rietveld method have been performed based on the XRD data. The results did not reveal any phase change during the milling. The average particle size decreases with a prolongation of milling times, while the lattice parameters, unit cell volume, and microstrain increase. Mössbauer measurement shows that there are two components, one nanometric and other micrometric. The magnetic hysteresis loops shows that the samples are typical of ferromagnet with superparamagnetic fraction in the material.

Co and Co₃O₄ nanoparticles are synthesized via a thermal decomposition method in the presence of oleylamine using a new precursor of [Bis(2-hydroxyacetophenato)cobalt(II)]. The products were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The hysteresis loops of the obtained samples reveal the ferromagnetic behaviors of the enhanced coercivity (H_c) and decreased saturation magnetization (M_s) in contrast to their respective bulk materials.

Zinc oxide nanoparticles were successfully prepared through the decomposition of zinc acetylacetonate precursor in oleylamine in the presence of triphenylphosphine. The products were characterized by X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy.

Mn₃O₄ nanocrystals have been prepared using [bis(2-hydroxyacetophenato)manganese(II)] as precursor. Transmission electron microscopy analysis demonstrated nanocrystals Mn₃O₄ with an average diameter of about 20 nm. The structural study by X-ray diffraction indicates that these nanocrystals have pure tetragonal phase. The phase pure samples were characterized using X-ray Photoelectron Spectroscopy for Mn 2p level. The values of binding energies are consistent with the relative values reported in the literature.

In this study, ZnO nanowires are synthesized via ZnO nanorods at low temperature by using zinc acetate dehydrate and polyvinylpyrrolidone as precursor and capping, respectively. We use chemical solution method for synthesis of ZnO nanowires. Samples are characterized by means of scanning electron microscopy and X-ray diffraction. First, the nanorods are prepared at 300°C temperature, and then they are put into the furnace under air atmosphere at 450°C for 2 h. It is observed that nanowires with 20 nm diameter are produced. Photoluminescence spectra of nanorods and nanowires are compared. It shows that intensity of ultraviolet peak in the nanowires decreases but in contrast the intensity of green emission part increases. This is because, the surface effects such as oxygen vacancies increase in the structures of ZnO.

Functional oxides are presently much investigated for their potential applications in various areas and Tin oxide appears particularly interesting when grown in nanometer range. A versatile and an economic technique have been developed for the synthesis of tin oxide nanoparticles, which does not require any substrate or surfactant. The technique is based on a simple reaction of tin and water at low temperature. The water is regarded as benign and safe solvent and the nanostructures so produced are biocompatible. This synthetic technique has the following advantages: First, the synthesis needs no sophisticated equipments since it is conducted at low temperature of 200°C under normal atmosphere. Second, the clean surfaces of the as-synthesized nanostructures can be readily functionalized for various applications since there is neither a capping reagent nor a substrate. Finally, the approach is nontoxic without producing hazardous waste. Therefore, the technique could be extended and expanded to provide a general simple and convenient strategy for the synthesis of nanostructures of other functional materials with important scientific and technological applications. The relative studies are in process and will be reported in forth coming publications.

Nanocrystalline 8 mol.% yttria-stabilized zirconia powder prepared from a combustion synthesis route has been sintered using microwave (MW) energy by two routes: Conventional one-step and a novel two-step method. The final products from the two routes have been compared regarding their microstructure, ion-conductivity, and mechanical properties. It is shown that it is possible to produce highly dense compacts with significant smaller grains using the novel two-step MW sintering method with significant smaller energy consumption with respect to conventional one-step MW assisted sintering. The novel method is able to produce sintered samples with near similar ionic conductivity at temperatures higher than 700°C and slightly lower mechanical properties at room temperature.

Ferroelectric PbZr_1-xTi_xO₃ (PZT) thin films have been extensively investigated because of their excellent piezoelectric, pyroelectric, ferroelectric, and dielectric properties. Sol–gel synthesis and spin-coating are popular routes to the formation of high quality, dense, and crack-free thin films. In this work, high quality, crack-free PZT thin films have been prepared by sol–gel method via spin-coating on Pt/Ti/SiO₂/Si substrate by different temperature processings. The crystallographic and morphological properties of the films have been analyzed by X-ray diffraction and scanning electron microscopy. The electrical properties of thin films including the permittivity, loss tangent, and polarization–voltage hysteresis loop were measured and compared for different films. Finally, by optimizing temperature processing, highly textured and high quality films of PZT with perovskite phase were obtained on Pt/Ti/SiO₂/Si substrates.

With developments in nanoscience and nanotechnology, Scanning Tunneling Microscope (STM) has found a wide application in imaging the atoms, molecules, and nanostructures. This microscope uses an ultra sharp metallic tip for scanning sample surface to produce surface topographic image with atomic resolution. Reliability and resolution of STM images depend largely on the sharpness of the tip apex and repeatability of images depends on mechanical strength of tip material. During last decades, a variety of techniques and processes have been developed for fabrication of different metallic tips made from tungsten, platinum, platinum–iridium, gold, and silver. Electrochemical etching process is the most popular method for fabrication of nanotips with desired quality, reliability, and reproducibility and tungsten is normally the first choice for fabrication of STM tips as it has a high mechanical strength as well as a good electrical conductivity. Fabrication of STM tungsten tip by using electrochemical etching method and tip characterization has been the subject of several researches. Nevertheless, to our knowledge, effect of voltage type (AC/DC), time delay in turning off the voltage, tungsten wire diameter, environmental vibrations, electrolyte type, cathode material, and perpendicularity of tungsten wire (toward electrolyte surface) on the tip sharpness have not been studied so far. In this paper, effects of these parameters on the tip shape and sharpness are investigated. A proper set-up for STM tungsten nanotip fabrication by using electrochemical etching method is presented.

The photoluminescence (PL) emitted by porous silicon has been investigated by using the continuous tuneable UV Synchrotron Radiation Source. One sample was investigated for orange PL emission wavelength at temperatures 77–295 K. The PL peak is found to shift to higher frequency with decreasing temperature. Information about the nanostructure of porous silicon has been determined from PL and Extended X-ray Absorption Fine Structure (EXAFS), as well as from electron microscopy. In particular, the optical properties of silicon-based nanostructured materials, obtained from PL and photoluminescence excitation measurements, have been correlated with structural information from Si–K-edge EXAFS. Electron microscopy was used to study the relation between the nanostructure and PL of porous Si, and to investigate porous Si structure. Platelet Si and Si crystallites in porous Si layers were observed. The size of crystallites ranged from 4 to 6.5 nm. Diffraction patterns show these porous Si samples have a crystalline structure.

Human Serum Albumin (HSA) nanoparticles represent promising drug carrier systems. Particle size is a crucial parameter in particular for the in vivo behavior of nanoparticles after intravenous injection. The object of present study was to characterize the desolvation process of HSA for preparation of nanoparticles. Two process parameters were examined to achieve a suitable size of nanoparticles such as the pH value and the amount of glutaraldehyde concentration (%). The smallest size of nanoparticles achieved was 91 nm and the largest size was 388 nm which is suitable for drug delivery. The pH value of the HSA solution prior to the desolvation procedure was identified as the major factor determining particle size and the amount of crosslinker showed that it has less effect on produced nanoparticle size. The nanoparticle sample was purified by five cycles' centrifugation (20 000× g, 8 min) and redispersion of the pellet to the original volume in 10 mM NaCl at pH values of 7.5–9, respectively, and then analyzed by particle size analyzer (PCS).

To add to the development efforts in enhancing the capabilities of localized electrodeposition (LED) fabrication technique, this paper presents serial and parallel deposition algorithms to fabricate array microstructures. Such arrays can be implemented as microsensors in neural recording applications or as antenna arrays in ultra high frequency applications. Also, magnetic tip microarrays for tissue engineering can be realized. In the case of serial fabrication, an array of high aspect ratio microstructures is realized using the conventional single-tip microelectrode while implementing a multistep fabrication algorithm. In this algorithm, the fabricated microstructure elements within the array are realized one at a time. In the parallel deposition algorithm, the array is realized using a multitip array microelectrode while implementing a single step fabrication algorithm. In this algorithm, the microstructure elements within the array are fabricated simultaneously. The proposed algorithms are compared through a demonstration of fabricated array microstructures.