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Metallic colloids are frequently used in industry and provide understanding of science at microns to nanometers scales along with their applicability for various technologically important applications. Present investigations deal with morphology and structure of gold, silver and their binary composition while processing certain amounts of their solutions in a newly designed process and tapping opportunities of developing tiny-shaped particles. At tuned ratio of pulse OFF to ON time and when gold solution was processed, several tiny-shaped particles developed at the solution’s surface. Such tiny particles exert force at the tip of each converting their structure of smooth element where steady-state immersing behavior directed them toward a common centre resulting into bind them for developing different geometric anisotropic shaped particles. Under identical parameters along with pulse time, processing solutions of silver nitrate and binary composition of chloroauric acid-silver nitrate result in the development of tiny particles having no specific shape where their assembling is under the mixed behavior of forces resulting in distorted particles. Elongation and deformation of gold and silver atoms while developing different structures are because of the plastically driven behavior of their electrons. In three-dimensional structures where atoms do not undergo transition to elongate, they retain the structure as it is, which is known as hcp structure or two-dimensional structure. Different nature of precursors along with morphology and structure of particles are discussed in this paper opening abundant avenues for research.

In this study, double-emulsion capsules (DECs) capable of concealing drug-incorporated targeted-supermolecules are developed to achieve "on-demand" supermolecule release and enhanced sequential targeting for magneto-chemotherapy. These water-in-oil-in-water DECs less than 200 nm in diameter are synthesized using a single component of PVA (polyvinyl alcohol) polymer and the magnetic nanoparticles, which are capable of encapsulating large quantities of targeted supermolecules composed of palitaxel-incorporated beta-cyclodextrin decorated by hyaluronic acid (HA, a CD44-targeting ligand) in the watery core. The release profiles (slow, sustained and burst release) of the targeted supermolecules can be directly controlled by regulating the high-frequency magnetic field (HFMF) and polymer conformation without sacrificing the targeting ability. Through an intravenous injection, the positive targeting of the supermolecules exhibited a 20-fold increase in tumor accumulation via the passive targeting and delivery of DECs followed by positive targeting of the supermolecules. Moreover, this dual-targeting drug-incorporated supermolecular delivery vehicle at the tumor site combined with magneto-thermal therapy suppressed the cancer growth more efficiently than treatment with either drug or supermolecule alone.

The electronic structures of graphene nanoflakes (GNFs) exposed to an organo-silane precursor [tetramethylsilane, TMS, Si(CH3)4] were studied using electron field emission (EFE), Raman spectroscopy, X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES), and first-principles calculation. The results of XANES, XPS, and Raman spectroscopy indicate that the silyl radical strong covalent bonds were formed in GNFs, which induced local structural relaxations and enhanced sp3 hybridization. Comparison of calculated electronic structure, XANES, and XES spectra of Si-treated GNFs suggests that the Si atom substitutes one 3-fold coordinated C atom in a given graphene layer and relaxes outward to form sp3 bonding with another C atom in the adjacent graphene layer. The EFE measurements show an increase in the turn-on electric field with the increase of the Si content, which suggests an enhancement of the nonmetallic sp3 bonding.

High-performance Pb(Zr,Ti)O3, PZT, thin films were synthesized on Si substrates by using low-temperature laser-assisted processes, which combine pulsed laser deposition (PLD), laser lift-off (LLO) and laser-annealing (LA) processes. The PZT films were first grown on sapphire substrates at 400 °C, using Ba(Mg1/3Ta2/3)O3, BMT, as seeding layer, by the PLD process, and were then transferred to Si substrates at room temperature by a LLO transferring process. Utilization of the BMT layer is of critical importance in those processes, since it acted as a nucleation layer for the synthesis of the PZT thin films on the sapphire substrates and, at the same time, served as a sacrificial layer during laser irradiation in the LLO process. After the LLO process, the surfaces of the PZT films were recovered by the LA process for removing the damage induced by the LLO process. A thin BMT (∼30 nm) layer is randomly oriented, resulting in non-textured PZT films with good ferroelectric properties, viz. Pr=20.6 μC/cm2 and Ec=126 kV/cm, whereas a thick BMT (∼100 nm) layer is (100) preferentially oriented, leading to (100)-textured PZT films with markedly better ferroelectric properties, viz. Pr=34.4 μC/cm2 and Ec=360 kV/cm.

Needle-like ZnO nanowires with high density are grown uniformly and vertically over an entire Ga-doped conductive ZnO film at 550 °C. The nanowires are grown preferentially in the c-axis direction. The X-ray diffraction (XRD) θ-scan curve shows a full width at half maximum (FWHM) value of 2°. This indicates that the c-axes of the nanorods are along the normal direction of the substrate surface. The investigation using high-resolution transmission electron microscopy (HRTEM) confirmed that each nanowire is a single crystal. A room-temperature photoluminescence (PL) spectrum of the wires consists of a strong and sharp UV emission band at 380 nm and a weak and broad green–yellow band. It reveals a low concentration of oxygen vacancies in the ZnO nanowires and their high optical quality. Field electron emission from the wires was also investigated. The turn-on field for the ZnO nanowires was found to be about 18 V μm–1 at a current density of 0.01 μA cm–2. The emission current density from the ZnO nanowires reached 0.1 mA cm–2 at a bias field of 24 V μm–1.

In-situ time-dependent Raman spectra were measured on the thermal annealing of diamond-like carbon films produced by Pulsed Laser Deposition (PLD-DLC), with or without the presence of atomic hydrogen etching. It was found that annealing transformed DLC films into a graphitic structure in both cases and this transformation was completed within 30 min of annealing. Atomic hydrogen etches away the G*=1500 cm −1 band, revealing the existence of the D*=1200 cm −1 band. Both G*- and D*- phases are as stable as graphite during thermal annealing. These observations separate the effects of thermal annealing and annealing with atomic hydrogen etching on diamond-like carbon films.

Atomic hydrogen etching on the pulsed laser deposited (PLD) diamond-like carbon (DLC) films were examined in situ by using Raman spectroscopy. Thermal annealing of the as-prepared DLC films was found to alter the D-band (∼1355 cm −1 ) and G-band (∼1582 cm −1 ) from unresolved features at room temperature to clearly separated bands at above 500°C, indicating graphitization of the films. The presence of atomic hydrogen retards graphitization at temperatures lower than 500°C, presumably because reactive atomic hydrogen formed sp 3 -bonding carbons which prevented graphitization at below 500°C, while at above 500°C, the hydrogen etches away disordered structure of the DLC film as the intensity changes of the D-bands demonstrate.

Selected area depositions (SAD) of diamond films were successfully achieved on silicon by two different approaches. In the first case, a standard lift-off technique employing a patterned SiO 2 layer was used as a mask, and in the second case commercial ink-jet printer technology was adapted to be used to seed diamond nano-grit onto silicon. Patterned, boron-doped diamond pads roughly 5.6 μm in diameter were formed by CVD growth on patterned SiO 2 /Si substrates and found to be composed of closely packed carbon clusters approximately 250–800 nm in size each containing 50-nm particles embedded in them. The patterned diamond film seeded by ink-jet printing formed after CVD growth with in situ boron-doping, dots (85 μm in diameter) containing poly-crystals in the nanometre range. The resulting patterned diamond films were characterised by Raman and scanning electron microscope (SEM) analysis and then configured as cold cathode field emitters to determine their electron emission performance. The results suggest that patterned diamond films produced by ink-jet printing offer a simpler method for fabricating planar diamond emitter arrays with field emission and conduction properties which could be tailored to improve the performance and fabrication cost of cold field emitters in state-of-the-art field emission displays.

YBa2Cu3O7−δ (YBCO) thin films were deposited on n-type (100) silicon wafers with yttria-stabilized zirconia (YSZ) buffer layers by a laser ablation technique. The YSZ layer had a thickness of about 60 nm, and was oriented preferentially in the (100) direction. The YBCO films were found to be preferentially (001) oriented, and had a superconducting critical temperature (Tc) above 85 K. Pure gold ohmic contacts were made on both sides of the YBCO/YSZ/Si structure and its I-V characteristics revealed a diode behavior. The turn-on and breakdown voltages are 1.3 and 20.34 V, respectively, at temperatures below the Tc. The ideality factor η had values of 13, 9.5 and 7 at room temperature, 100 and 50 K, respectively. Better superconductivity, lower operation temperature, and thinner buffer layers would result in better rectification.

The superconductivity of YBa 2 Cu 3 O 7−∂ (YBCO) films grown on MgO substrate materials has been modified significantly using SrTiO 3 (STO) films as buffer layers. The role of the STO layer has been examined by conventional wide-angle X-ray diffraction (XRD), by atomic force microscopy (AFM) and by grazing-incident X-ray diffraction (GIXD) techniques and it has been found (i) to suppress the interaction between the films and the substrate materials and (ii) to enhance the nucleation and growth of (001)-oriented YBCO grains. The (001) epitaxial STO films are found to be of decisive importance to optimization of the superconductivity of the subsequently deposited YBCO films. Both the substrate temperature (720°C) and oxygen pressure (0.02 mbar) have to be stringently controlled for this purpose. The YBCO/STO/MgO films thus obtained possess excellent superconducting properties with T c =90 K and transition width δT =2 K.

Epitaxial-like Y 1 Ba 2 Cu 3 O 7−δ (YBCO) thin films, with superconductivity ( T c ) around 89 K have been synthesized on MgO (001) substrates at 720°C, using the single-source plasma enhanced chemical beam deposition (PE-CBD) technique. The oxygen plasma excited by the microwave is observed to be capable of effectively enhancing the formation of the perovskite phase. The YBCO films are highly c-axis textured when deposited at a substrate temperature higher than 690°C, but it requires 720°C to fully align the a and b -axes of the YBCO grains in parallel with the [100] and [010] axes of the MgO lattice. The rocking curve (Δθ=2950″) indicates that the films are of good crystallinity. In addition, the advantage of PE-CBD over other processes in preparing high-quality YBCO films is also discussed from the aspects of reliability and device compatibility. The PE-CBD shows a promising method to prepare a high-quality YBCO film.

Factors affecting the densification and microstructure development in the reaction sintering process (RSP) of yttrium iron garnet were investigated. Three different powder mixtures were used: Fe2O3/Y2O3, Fe2O3/YFeO3 (1100 ° C calcined), and Fe2O3/YFeO3 (1200 ° C calcined). The conventionally prepared garnet powder was also adopted as a reference material. It was found that the RSP using Fe2O3-YFeO3 systems has a beneficial effect on densification from the dilatation occurring along with the reaction of garnet formation. On the other hand, it has a detrimental effect due to the local contraction induced by the reaction in the Fe2O3-Y2O3 system. The densification rate and ultimate density achievable are also affected by the YFeO3 powder adopted in RSP. A high grain-growth rate was obtained for garnet when the 1200 ° C calcined YFeO3 powder was used. This leads to a high densification rate at low temperature. However, the densification ability deteriorates at temperatures above 1425 ° C due to the trap of pores in the fast-grown grains. Conversely, the grain-growth rate in RSP with 1100 ° C-calcined YFeO3 was moderate, and although it gives a slower densification rate at low temperature, the ultimate density can be raised to ≈ 99% theoretical density at ⩾ 1450 ° C.

High performance flexible field emitters made of aligned pyramidal shaped conducting ultrananocrystalline diamond (C-UNCD) microtips on polynorbornene substrates is demonstrated. Flexible C-UNCD pyramidal microtips show a low turn-on field of 1.80 V/μm with a field enhancement factor of 4580 and a high emission current density of 5.8 mA/cm2 (at an applied field of 4.20 V/μm) with life-time stability of 210 min. Such an enhancement in the field emission is due to the presence of sp2-graphitic sheath with a nanowire-like diamond core. This high performance flexible C-UNCD field emitter is potentially useful for the fabrication of diverse, flexible electronic devices.

BaTiO3 is a prototype perovskite having many properties common to cuprates, manganites and nickelates. To understand the electronic structure of these perovskites, we have measured O K-edge of TiO2, BaTiO3 and CaTiO3. Spectral features starting from 530 to 550 eV in O K-edge provides significant information to understand the role of alkaline metals like Ca, Ba. Electronic polarizability may be an important parameter to understand many properties of these perovskite materials.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Fabrication of free-standing/highly conducting ultrananocrystalline diamond (fc-UNCD) films at low growth temperature (

We report monolithic n-type conductivity on low-temperature (

Polycrystalline samples of yttrium iron garnet, Y 3 Fe 5 O 12 , were prepared by sintering the powder mixtures of Y 2 O 3 and Fe 2 O 3 , as well as YFeO 3 and Fe 2 O 3 , in the temperature range from 1350 to 1475°C. The sintering of calcined garnet powder was also done for a comparison. It was found that the densification was enhanced by the reaction sintering with YFeO 3 and Fe 2 O 3 powder mixture, but deteriorated by that with Y 2 O 3 and Fe 2 O 3 . The former was benefited from a microstructure of fine grain and porosity without trapped pores in the grains. However, the latter was ill with an early and rapid anomalous grain growth, which had caused a large number of pores trapped in the anomalously-grown grains. A high density near 99% theoretical value was reached for the samples prepared from YFeO 3 and Fe 2 O 3 powder mixture and sintered at 1475°C for 4 hours, or at 1450°C for 8 hours.

Polycrystalline MgAl204 which is transparent in the infrared spectral regions can be achieved by hot pressing of high activity powders. Fine, homogeneous and high purity MgAl204 powders were obtained by metal alkoxide-hydrolysis method. Three processes for powder preparation have been approached, namely, (1) conventional alkoxide-hydrolysis process, (2) sol-gel process and (3) diluted-sol drying process. The last process was the most attractive one, as it is easier to control the powder morphology and takes less time to prepare. Drying process affects the characteristics of the powders significantly. The morphology of spray-dried powders are thin-wall hollow spheres of uniform size, while those of freeze-dried powders show agglomerated lump. Spray-dried powders possess higher sinterability and the disks hot preesed from these powders show higher infrared transparency. That of the hot pressed spinel samples was further improved by heat treatment and optical polishing.

The superconductivity of pseudo-quternary system Y1−xMx Ba2 Cu3 O7-δ, YBa2 Cu3−xM x O7-δ, where M stands Co,Cr,&Zn and with x=0,0.001,0.005,0.01 & 0.02, has been investigated.The XRD analysis shows that the perovskite structure is preserved and a stabilization effect on orthorhombic structure by 3d elements addition was proposed. On the contrary, the microstructure has been modified prominently and it is determined by the sintering mechanism involved and/or diffusion process in each doped sample. Second phase precipitate can be found at grain surface. The superconductivity, however, has not been greatly affected.

High‐T YBaCuO and BiSrCaCuO Superconducting wires have been fabricated by powder metallurgy technique. Copper and silver tubes were used as the external jackets. Thermal annealing treatments for all the wire‐type samples were performed between 773 K and 1223 K. Both electrical and magnetization studies show that the superconducting properties can be improved after properly thermal annealing these samples with silver jacket. Our experimental results show that proper thermal annealing treatment can enhance the intragrain critical current density more than 100 times; however, the intergrain critical current density improves only a few times.

MnZn-ferrites and Li-ferrites are soft magnetic materials used in telecommunication and entertainment electronics because of their high magnetic permeability and low magnetic loss characteristics. The magnetic properties of these materials are very sensitive to composition and microstructure. In the present paper, results of an investigation of the interaction of magnetic domains with the microstructural features are presented and the significance of such studied on microstructure-property relationships is discussed.Lorentz microscopic technique in TEM has been used to study the domain wal structure and its interaction with grain boundaries, precipitates, pores, cracks, etc. in situ. Electron transparent specimens from bulk samples were prepared by ion beam milling technique and were examined in a Philips EM301 microscope operating at 100kV. The motion of domain walls was studied in situ by tilting the specimen so that there is a magnetic field applied to the plane of the specimen.