We have developed interatomic potentials for Pt-Ni and Pt-Re alloys within the modified embedded atom method (MEAM). Furthermore, we applied these potentials to study the equilibrium structures of Pt75Ni25 and Pt75Re25 nanoparticles at T=600 K using the Monte Carlo method. In this work, the nanoparticles are assumed to have disordered fcc cubo-octahedral shapes (terminated by {111} and {100} facets) and contain from 586 to 4033 atoms (corresponding to a diameter from 2.5 to 5 nm). It was found that, due to surface segregation, (1) the Pt75Ni25 nanoparticles form a surface-sandwich structure: the Pt atoms are enriched in the outermost and third atomic shells, while the Ni atoms are enriched in the second atomic shell; (2) the equilibrium Pt75Re25 nanoparticles adopt a core-shell structure: a Pt-enriched shell surrounding a Pt-deficient core.

The deformation of Au nanowires of helical multi-shell (HMS) structures and the fcc structure under a tensile external force is addressed by molecular-dynamics simulation. The modified embedded-atom method (MEAM) potential is employed for calculating the interaction between Au atoms. At first, a model nanowire is equilibrated at a specified temperature. Next, the external force in the axial direction is imposed on the Au atoms at the ends of the nanowire. We conclude that the Young modulus of a Au nanowire depends on its atomic structure.

We present a study of the photoluminescence and lasing characteristics of individual single-crystal zinc sulfide nanoribbons. We show that ZnS presents optical gain at the near band gap emission of ∼338 nm. Optical gain together with the optical cavity defined by the perfect crystallographic structure with a rectangular cross section results in lasing activity at optical pumping power densities of ∼ 50 kW/cm2. Small collection angle measurements show that nanoribbons form excellent optical cavities and gain medium with record (FWHM<0.1nm) lasing modes free of PL background. Large collection angles (as previously employed for nanowire measurements) add a broad, non-resonant PL component and obscure the original high-quality lasing of the nanowires/nanoribbons.

The combination of 1-adamantanecarboxylic acid and tri-alkylphosphine was applied to produce monodisperse FePd nanoparticles by the polyol reduction of palladium acetylacetonate and thermally decomposition of iron pentacarbonyl. Images of high resolution transmission electron microscopy (TEM) and X-ray diffraction (XRD) data indicate a highly monodisperse and crystalline nature of the FePd nanoparticles. Magnetic studies performed by Quantum Design SQUID magnetometer show that FePd (16nm) nanoparticles are superparamagnetic at room temperature.

ITO nanoparticles were synthesized by coprecipitation method in an aqueous solution and thermal method in an alcohol solution. The coprecipitate prepared at room temperature showed the crystal structure of indium oxide in X-ray diffraction when it was annealed above 300°C. In thermal method, the nanoparticles have two phase crystal structure of indium oxide hydroxide (InOOH) and indium hydroxide (In(OH)3). Annealing at the temperature above 300 °C, it showed the rhombohedral crystal structure of indium oxide (In2O3). The phase transition of ITO nanoparticle was also detected with DSC. Near IR-reflective film was prepared by spin coating using ITO sol solution. Transmission electron microsopy (TEM) and energy dispersive X-ray spectrometer (EDS) were used to characterize the morphology and composition of ITO nanoparticles. Near-IR (NIR) spectrometer was used to determine reflectance on the surface of ITO film in the NIR-radiation region.

A homogeneous non-aqueous solution reactions method has been developed to prepare gold-coated cobalt (Co@Au) nanoparticles. After the sample was washed with 8% HCl, XRD (X-Ray Diffraction), TEM (transmission electron microscopy), and magnetic measurements SQUID (Superconducting Quantum Interference Device) are utilized to characterize the nanocomposites. XRD shows the pattern of sample, which is responding to gold and cobalt, no cobalt oxide was found. TEM results show that the average size of Co@Au nanoparticles is about 10 nm and we can find core-shell structure of the sample. SQUID results show that the particles are ferromagnetic materials at 300K. So the gold- coated cobalt nanoparticles (Co@Au) can be successfully prepared by the homogeneous nonaqueous approach. This kind of core-shell materials is stable in acid condition, which would give many opportunities for bio- application.

One and two-dimensional arrays of nanoripples and nanoprotrusions can be generated by pulsed laser irradiation. Nanoprotrusions were produced on the surface of silicon when a Lloyd's mirror configuration was used, and could develop to a height of 80 nm. Atomic force and high resolution scanning electron microscopy studies revealed that these structures are preceded by the formation of extended ripples that can reach a height of up to 12 nm. It is shown that one or two identifiable arrays of mutually orthogonal ripples may form. Out of the four differently- spaced ripple arrays that were found, three indicated a very close connection with the production of laser-induced periodic surface structures (LIPSS). Interference of the incoming or refracted laser beam and the laser light scattered by surface undulations has been recognized as the cause of LIPSS formation. The present experiments show that the Lloyd's mirror configuration strongly enhances the formation of ripples and that nanoprotrusions form, sometimes at the intersection of two mutually orthogonal sets of ripples. Each of the beams, the directly incident and the mirror-reflected beam, independently produce an interference pattern with their corresponding scattered beams. However, these two independently generated patterns coincide because their periodicity is only a function of the angle of incidence. Thus, the two interference patterns reinforce each other's effects on the substrate. Single beam, direct irradiation of the substrate failed to induce nanoprotrusions, although 1-D ripple arrays developed.

Nanopatterning through strain-assisted nucleation of metal adatom islands is experimentally studied using a magnetic remanence or Δm measurement. The strain field is generated by a square array of interfacial misfit dislocations with a spacing of 4.1 nm due to the lattice mismatch of the epitaxial Pt(002) film on MgO(002) substrates. The intensity of strain is controlled by changing the thickness of the Pt underlayer ranging from 2.0 to 10.0 nm. The amount of exchange coupling among the Co grains grown on Pt template is measured using the μm technique as an indirect indicator of magnetic grain distribution. From the measured μm values, the morphology of adatom islands is indirectly deduced. The Co islands on a 5.0 nm thick Pt underlayer show the overall negative behavior of Δm curve, i.e., the strongest nanopatterning effect. Strain driven nucleation is found to be achievable through a narrow selection of experimental growth conditions.

Ni nanoparticles where obtained from a Ni sample milled with Ar ions by using a Gatan precision ion polishing system, normally used for Transmission Electron Microscopy (TEM) sample preparation. Deposition of Ni nanoparticles was performed over two different surfaces: on a double sided carbon tape and, on a Cu grid covered with collodion film. A continuos film of Ni was characterized, over the carbon tape by SEM and EDAX techniques. The last surface was analysed by TEM. In both cases, a thin film composed of Ni nanoparticles, was founded and result obtained by TEM, show a nanoparticle diameter of about 4 nm.

Efficient and reliable laser-ablation approaches for large-scale synthesis of SnO2 nanowires are reported. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) were used to confirm the crystal structure of the nanowires. The results show that these nanowires had uniform diameters around 20 nm and lengths in the order of 10 νm. In addition, field effect transistors have been constructed based on individual SnO2 nanowires. Excellent n-type transistor characteristics have been observed for SnO2 nanowire transistors. Detailed analysis revealed threshold voltages ∼ -50V with on/off ratios as high as 103 at room temperature. These nanowire transistors were further demonstrated to work as sensitive UV detectors and gas sensors.

Isotopically pure 70Ge and 74Ge nanocrystals embedded in SiO2 thin films on Si substrates have been fabricated through ion implantation and thermal annealing. Nanocrystals were subsequently exposed using a hydrofluoric acid etching procedure to selectively remove the oxide matrix while retaining up to 69% of the implanted Ge. Comparison of transmission electron micrographs (TEM) of as-grown crystals to atomic force microscope (AFM) data of exposed crystals reveals that the nanocrystal size distribution is very nearly preserved during etching. Therefore, this process provides a new means to use AFM for rapid and straightforward determination of size distributions of nanocrystals formed in a silica matrix. Once exposed, nanocrystals may be transferred to a variety of substrates, such as conducting metal films and optically transparent insulators for further characterization.

Since the crystallographic phase and morphology of many materials changes with the crystal size in the one to hundred nanometer range and the potential technological applications of nanoparticles are enormous, a need arises to determine the crystallography of nanoparticles individually. Direct space high- resolution phase-contrast transmission electron microscopy (TEM) and atomic resolution Z-contrast scanning TEM when combined with goniometry of direct and/or reciprocal lattice vectors offer the possibility of developing dedicated nanocrystallography characterization methods for such small nanoparticles. Although experimentally feasible for cubic nanocrystals with lattice constants larger than 0.4 nm in contemporary high-resolution TEMs with modest tilt range, image-based nanocrystallography by means of transmission electron goniometry has so far only been employed by a few specialists worldwide. This is likely to change in the future with the availability of aberration-corrected TEMs. The reasons why this change is likely to happen are outlined in this paper.

Gold nanoparticles were deposited on SiO2, Si(100) and HOPG (Highly Oriented Pyrolitic Graphite) by RF-sputtering from Ar plasmas. Sample preparation was performed at temperatures as low as 60°C under different total pressures, RF-powers and deposition times, with particular attention to the influence of process parameters and growth surface on nanosystem properties. In this paper, the most important results regarding the compositional, structural and morphological features of the obtained specimens, are presented and discussed.

The focus of today's research has largely shifted from macro scale to micro scale and further to nano scale. The reason being the desire to realize quantum size effects in devices that has long eluded scientists around the world alike. With the discovery of nanoparticles, nanowires, and nanotubes, the ability to realize these effects practically into devices has increased manifold. Integration of carbon nanotubes with different types of functional materials may become mandatory in the future for electronics and sensing applications and in this sense, nucleation, growth and evolution of the structure of metallic and semiconducting materials on carbon nanotubes may be necessary. Further, it also provides opportunities to do fundamental research on understanding the structure-property relationships of these nanowires using carbon nanotubes. In this paper, we present a technique to form metallic and semiconducting nanowires using carbon nanotubes themselves as templates. Nanowires of silver and platinum have been fabricated by the electric field assisted deposition of nano particles of these metals on single walled carbon nanotubes. SEM and TEM investigations have shown the dimensions of the nanowires to be dependent only on the size of the nanoparticles, 10 - 100 nm in our case. The silver nanowires exhibited linear current – voltage characteristics whereas the platinum nanowires exhibited non-linear characteristics beyond a certain bias. This technique provides a high degree of selectivity by manipulating the charges on the surface of the nanotubes, which enables the deposition of metals only on the nanotubes and not anywhere else. The versatility of this technique allows for the fabrication of different types of metallic and semiconducting nanowires at the same dimensions as carbon nanotubes.

A honeycomb-like SiC reconstructed surface with regular, periodic porosity in the nano-scale range has been used as an effective template for the formation of monodispersed Co nanoclusters. In-situ scanning tunneling microscopy (STM) was used to study the nucleation process of the Co nanoclusters on this template. The deposition of Co at different substrate temperature was investigated by STM. It is found that the failure in the deposition of Co nanoclusters on the SiC honeycomb template with substrate temperatures higher than room temperature (RT) might be due to the high desorption rate of the adsorbed Co atoms.

In this paper, we demonstrate the self assembled growth of nanotubes along the surface of (100), (110) and (111) silicon wafers using thermal CVD. Iron nanoparticles, 10 nm in diameter, were used as the catalyst. Carbon nanotubes were grown in a methane atmosphere at 1000°C. SEM and AFM characterization revealed single wall carbon nanotubes, about 10 nm in diameter and up to 10 νm in length, growing along the <111> direction of the silicon wafer. The mechanism of growth of nanotubes is similar to that of molecular epitaxy which occurs due to the lattice matching of the silicon and iron crystal lattices forming self aligned silicides at high temperature which help orient the nanotubes. This process may enable the integration of nanotubes with CMOS processing technology.

In this study, a novel SnO2 nanoparticle was successfully synthesized by controlling its surface structure. The surface structure on the nanoparticle is consistent of Pd and PdO clusters of which size is smaller than 1nm. For uniform dispersion of the clusters, in-situ synthetic method was applied using Sn acetate and Pd acetate. The method enhances uniformity by mixing two elements as an aqueous solution. Also, those materials lower the processing temperature since the removal of organic components is possible below 300°C. HRTEM observation reveals that the size of the synthesized particle is ranged from 2 to 7 nm and the Pd cluster is uniformly distributed in the lattice of SnO2 particle. In fact, XRD analysis certifies the uniform solid solution of the Pd cluster in SnO2 since the localized Pd peak was not found. Specific surface area of the synthesized particle measured with BET surface analyzer exceeded 100 m2/g. Also, the SnO2-5wt%Pd nanoparticle exhibits the excellent change in resistance of 0.62 after aging at 400°C for 5 hours. Also, the electrical properties show very stable phenomena in spite of long- term aging for 400 hours at 400°C. So, the ultrafine SnO2-Pd nanoparticle could be synthesized by using the in-situ synthetic method.

We address the template-directed deposition of metals on microtubule supports for generating metal nanostructures with different morphologies. Microtubules are highly ordered protein assemblies of tubular structure with a high aspect ratio. In this approach, the biostructure serves as a functionalised scaffold where the metal is generated in situ and shaped into a nanostructure with its morphology complementary to that of the biotemplate. When the biotemplate is coupled to an appropriate chemical reaction, different Ag / protein structures are produced, ranging from microtubules densely covered by small Ag nanoparticles to continuous Ag nanowires.

Creating hybrid nanostructures of disparate nanoscale blocks is of interest of exploring new types of electronic devices and networks. Here, we demonstrate the novel coupling of gold nanoparticles of 3-4 nm diameters to sidewall of multiwalled carbon nanotubes (MWNTs) using the electroless plating technique. MWNTs were initially chemically modified with an H2SO4-HNO3 acid treatment, and subsequently activated with Pd-Sn catalytic nuclei via a one-step activation approach. When the activated MWNTs were immersed in a gold-containing electroless plating bath, gold deposition occurred at the catalytic sites. The deposited gold clusters then catalyze further gold deposition on the tube surface (autocatalytic process). Novel hybrid nanostructures with gold nanoparticles homogeneously distributed on MWNTs resulted. High-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) were used to characterize the conjugation process.

We have investigated exciton states in wurtzite GaN/AlN and ZnO quantum dots. A strong piezoelectric field in GaN/AlN quantum dots is found to tilt conduction and valence bands, thus pushing the electron to the top and the hole to the bottom of the GaN/AlN quantum dot. As a result, the exciton ground state energy in GaN/AlN quantum dots with heights larger than 3 nm exhibits a red shift with respect to bulk GaN energy gap. It is shown that the radiative decay time in GaN/AlN quantum dots is large and increases from 0.3 ns for quantum dots with height 1.5 nm to 1.1×103 ns for the quantum dots with height 4.5 nm. On the contrary, the electron and the hole are not separated in ZnO quantum dots. Moreover, a relatively thick “dead layer” is formed near the surface of ZnO quantum dots. As a result, the radiative decay time in ZnO quantum dots is small and decreases from 73 ps for quantum dots with diameter 1.5 nm to 29 ps for the quantum dots with diameter 6 nm.