Nanoscience

We show that the shape of electroluminescence transients in organic semiconductors can be conveniently used to obtain the diffusion constant D of injected charge carriers, enabling the study of generalized Einstein relationship under nonequilibrium conditions as a function of the electric field. The appearance of peak at the onset of transient is shown to be the signature of diffusive regime of transport. We demonstrate it for two representative materials, Alq 3 and polymer poly [2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene], with the focus on the role of hot carriers in transport and their diffusivity.

Investigating the multidimensional integration between different microbiological kingdoms possesses potential toward engineering next-generation bionic architectures. Bacterial and fungal kingdom exhibits mutual symbiosis that can offer advanced functionalities to these bionic architectures. Moreover, functional nanomaterials can serve as probing agents for accessing newer information from microbial organisms due to their dimensional similarities. In this article, a bionic mushroom was created by intertwining cyanobacterial cells with graphene nanoribbons (GNRs) onto the umbrella-shaped pileus of mushroom for photosynthetic bioelectricity generation. These seamlessly merged GNRs function as agents for mediating extracellular electron transport from cyanobacteria resulting in photocurrent generation. Additionally, three-dimensional (3D) printing technique was used to assemble cyanobacterial cells in anisotropic, densely packed geometry resulting in adequate cell-population density for efficient collective behavior. These 3D printed cyanobacterial colonies resulted in comparatively higher photocurrent (almost 8-fold increase) than isotropically casted cyanobacteria of similar seeding density. An insight of the proposed integration between cyanobacteria and mushroom derives remarkable advantage that arises from symbiotic relationship, termed here as engineered bionic symbiosis. Existence of this engineered bionic symbiosis was confirmed by UV− visible spectroscopy and standard plate counting method. Taken together, the present study augments scientific understanding of multidimensional integration between the living biological microworld and functional abiotic nanomaterials to establish newer dimensionalities toward advancement of bacterial nanobionics.

Low-temperature plasma physics and technology are diverse and interdisciplinary fields. The plasma parameters can span many orders of magnitude and applications are found in quite different areas of daily life and industrial production. As a consequence, the trends in research, science and technology are difficult to follow and it is not easy to identify the major challenges of the field and their many sub-fields. Even for experts the road to the future is sometimes lost in the mist. Journal of Physics D: Applied Physics is addressing this need for clarity and thus providing guidance to the field by this special Review article, The 2012 Plasma Roadmap.

Surface science has evolved from being a sub-field of chemistry or physics, and has now established itself as an interdisciplinary topic. Knowledge has developed sufficiently that we can now understand catalysis from a surface science perspective. No-where is the underpinning nature of surface science better illustrated than with nanoscience.

Now in its third edition, this successful textbook aims to provide students with an understanding of chemical transformations and the formation of structures at surfaces. The chapters build from simple to more advanced principles with each featuring exercises, which act not only to demonstrate concepts arising in the text but also to form an integral part of the book, with the last eight chapters featuring worked solutions.

Synthesis of nanomaterials by a simple, low cost and in high yield has been a great challenge since the very early development of nanoscience. Various bottom and top down approaches have been developed so far, for the commercial production of nanomaterials. Among all top down approaches, high energy ball milling, has been widely exploited for the synthesis of various nanomaterials, nanograins, nanoalloy, nanocomposites and nano -quasicrystalline materials. Mechanical alloying techniques have been utilized to produce amorphous and nanocrystalline alloys as well as metal/non-metal nanocomposite materials by milling and post annealing, of elemental or compound powders in an inert atmosphere. Mechanical alloying is a non-equilibrium processing technique in which different elemental powders are milled in an inert atmosphere to create one mixed powder with the same composition as the constituents. In high-energy ball milling, plastic deformation, cold-welding and fracture are predominant factors, in which the deformation leads to a change in particle shape, cold-welding leads to an increase in particle size and fracture leads to decrease in particle size resulting in the formation of fine dispersed alloying particles in the grain-refined soft matrix. By utilizing mechanical milling various kind of aluminium/ nickel/ magnesium/ copper based nanoalloys, wear resistant spray coatings, oxide and carbide strengthened aluminium alloys, and many other nanocomposites have been synthesized in very high yield. The mechanical milling has been utilized for the synthesis of nanomaterials either by milling and post annealing or by mechanical activation and then applying some other process on these activated materials. This review is a systematic view of the basic concept of mechanical milling, historical view and applications of mechanical milling in the synthesis of various nanomaterials, nanosomposites, nnaocarbons and nano quasicrystalline materials.

Chemical Vapour Deposition (CVD) of films and coatings involve the chemical reactions of gaseous reactants on or near the vicinity of a heated substrate surface. This atomistic deposition method can provide highly pure materials with structural control at atomic or nanometer scale level. Moreover, it can produce single layer, multilayer, composite, nanostructured, and functionally graded coating materials with well controlled dimension and unique structure at low processing temperatures. Furthermore, the unique feature of CVD over other deposition techniques such as the non-line-of-sight-deposition capability has allowed the coating of complex shape engineering components and the fabrication of nano-devices, carbon-carbon (C-C) composites, ceramic matrix composite (CMCs), free standing shape components. The versatility of CVD had led to rapid growth and it has become one of the main processing methods for the deposition of thin films and coatings for a wide range of applications, including semiconductors (e.) used for hard coatings, protection against corrosion, oxidation or as diffusion barriers; metallic films (e.g. W, Mo, Al, Au, Cu, Pt) for microelectronics and for protective coatings; fibre production (e.g. B and SiC monofilament fibres) and fibre coating. This contribution aims to provide a brief overview of CVD of films and coatings. The fundamental aspects of CVD including process principle, deposition mechanism, reaction chemistry, thermodynamics, kinetics and transport phenomena will be presented. In addition, the practical aspects of CVD such as the CVD system and apparatus used, CVD process parameters, process control techniques, range of films synthesized, characterisation and co-relationships of structures and properties will be presented. The advantages and limitations of CVD will be discussed, and its applications will be briefly reviewed. The article will also review the development of CVD technologies based on different heating methods, and the type of precursor used which has led to different variants

Wakaf adalah amalan mulia yang sangat di galakkan oleh Islam. Sebagai salah satu mekanisme kebajikan, wakaf agak unik berbanding dengan sedekah, hadiah dan derma kerana harta yang diwakafkan itu akan di 'tahan' ia itu tidak dihabiskan tetapi sebaliknya apa-apa manfaat atau pulangan daripada penggunaan harta wakaf itu boleh dibelanjankan. Bermula dengan amalan wakaf harta tetap secara langsung, dewasa ini perkembangan wakaf adalah dalam bentuk wakaf tunai dan daripada tunai inilah sebahagiannya dimanfaatkan untuk pembangunan atau pembelian hartanah atau harta lain dan sebahagian pula akan dilaburkan dalam pasaran kewangan. Mengambil iktibar daripada sejarah amalan wakaf di dalam tamaddun Islam serta amalan 'endowmen' di dunia Barat, mekanisme atau kaedah wakaf tunai (aset cair) dalam berbagai aplikasi atau produk perlu dilaksanakan dengan segera. Pembangunan ini dapat dipercepatkan melalui badan khas diperingkat negeri dan kebangsaan dengan mengambil pelajaran daripada perkembangan institusi-institusi zakat. Penulis membuat saranan akan beberapa produk wakaf pendidikan yang berpotensi.

In this paper we give the simple and less hazardous route for synthesis of CdSe nanoparticles. We are using co-prepitation method for synthesis of CdSe nanoparticles we are getting nanoparticles by doing calcination process at 400°C.The synthesized CdSe nanoparticles have been characterized by Optical Microscope and X-ray diffraction. The uniqueness of Hexagonal (Wurtzite) CdSe was revealed by the X-ray diffraction peaks.

This paper reports an experimental investigation into force convective heat transfer of nanofluids flowing through a cylindrical minichannel under laminar flow and constant wall heat flux conditions. Sample nanofluids were prepared by dispersing different volumetric concentrations (0.2-0.8%) of nanoparticles in deionized water. The results showed that both the convective heat transfer coefficient and the Nusselt number of the nanofluid increase considerably with the nanoparticle volume fraction as well as the Reynolds number. Along with the enhanced thermal conductivity of nanofluids, the migration, interactions, and Brownian motion of nanoparticles and the resulting disturbance of the boundary layer are responsible for the observed enhancement of heat transfer coefficients of nanofluids.

The antimicrobial effects of sliver ions have been known for long but their activity against microorganisms has not yet been conclusively studied. In the present study, biological synthesis of silver nanoparticles using Klebsiella pneumonia has been investigated. The bacterial strain was grown the appropriate production media. The cell free filtrate obtained on filtration was bought in contact with different concentrations of AgNO 3. . The change in the pH with respect to the different concentrations was studied .The nanoparticles were further characterized by SEM studies. The antimicrobial activity of silver nanoparticles was investigated against E. coli, Bacillus and ESBL .Also the antimicrobial activity of encapsulated beads of silver nanoparticles and 2mM silver nanoparticles was compared. The anti-microbial fabrics activity was studied by coating the silver nanoparticles on gauge cotton fabric and then compared with standard disc Oxacillin. UV-VIS studies showed an increased in absorbance at 363 nm. The antimicrobial tests against E.coli showed increased inhibition at 1mM while for Bacillus, inhibition was more prominent at 2mM concentration and for ESBL-Pseudomonas inhibitory concentration was 2mM .The zone of inhibition for the encapsulated beads was less than that of the 2mM silver nanoparticles.

Titanium dioxide (TiO 2 ) nanoparticles are widely used in water treatments, yet their influences on other contaminants in the water are not well studied. In this study, the aqueous uptake, assimilation efficiency, and toxicity of two ionic metals (cadmium-Cd, and zinc-Zn) in a freshwater zooplankton, Daphnia magna, were investigated following 2 days pre-exposure to nano-TiO 2 . Pre-exposure to 1 mg/L nano-TiO 2 resulted in a significant increase in Cd and Zn uptake from the dissolved phase. After the nano-TiO 2 in the guts were cleared, the uptake rates immediately recovered to the normal levels. Concurrent measurements of reactive oxygen species (ROS) and metallothioneins (MTs) suggested that the increased metal uptake was mainly due to the increased number of binding sites provided by nano-TiO 2 presented in the guts. Consistently, pre-exposure to nano-TiO 2 increased the toxicity of aqueous Cd and Zn due to enhanced uptake. Our study provides the evidence that nano-TiO 2 in the guts of animals could increase the uptake and toxicity of other contaminants.

In situ near edge X-ray absorption fine structure (NEXAFS) spectroscopy and ambient pressure X-ray photoelectron spectroscopy (AP-XPS) were performed to monitor the oxidation state and structure of 4 nm CoPt nanoparticles during the reaction of CO with O 2 -a model oxidation reaction. In addition, reversible changes in the oxidation state of cobalt as a function of cycling CO and O 2 pressure (in the range of millitorr to 60 Torr) were quantified and compared. Turnover frequency reaction data was also obtained for the CoPt nanoparticles and correlated with the oxidation states and structures observed spectroscopically. These findings indicate that separated from the effect of partial pressure of the reactant gases, chemical state and structure changes of the CoPt nanoparticles during CO oxidation are important factors in determining the rate of the reaction.

We present models for the optical functions of 11 metals used as mirrors and contacts in optoelectronic and optical devices: noble metals ͑Ag, Au, Cu͒, aluminum, beryllium, and transition metals ͑Cr, Ni, Pd, Pt, Ti, W͒. We used two simple phenomenological models, the Lorentz-Drude ͑LD͒ and the Brendel-Bormann ͑BB͒, to interpret both the free-electron and the interband parts of the dielectric response of metals in a wide spectral range from 0.1 to 6 eV. Our results show that the BB model was needed to describe appropriately the interband absorption in noble metals, while for Al, Be, and the transition metals both models exhibit good agreement with the experimental data. A comparison with measurements on surface normal structures confirmed that the reflectance and the phase change on reflection from semiconductor-metal interfaces ͑including the case of metallic multilayers͒ can be accurately described by use of the proposed models for the optical functions of metallic films and the matrix method for multilayer calculations.

ABSTRACT In analogy to photocatalytic materials, the metal-organic framework MIL-53(Fe) showed up self-cleaning ability under light. In the presence of hydrogen peroxide and with exposure under UVA-VIS irradiation, organic impurities were decomposed completely without damage of MIL-53(Fe) structure. The method is efficient and environment-friendly such that all the free and confined 1,4-benzenedicarboxylic acid in the MOF were decomposed within 1 hour at room temperature. The MIL-53(Fe) samples before and after purification were fully analyzed by XRD, FTIR, FE-SEM and TGA measurements.

A series of ceria nanoparticles were synthesized by using a microemulsion method. The effect of relative concentration of surfactant/water on the size and the surface roughness of ceria nanoparticles was examined using transmission electron microscopy (TEM) and atomic force microscopy (AFM) respectively. The investigation confirmed a relationship between the size and the roughness properties of the nanoceria as a function of the water to surfactant ratio. With increasing dilution of the surfactant, the size distribution became narrow such that average particle size decreased linearly as the ratio increased without affecting lower size threshold of particles (∼10 nm). The surface roughness, on the other hand was found to increase with increasing water to surfactant ratio implying diluted surfactant would provide rougher surface of ceria nanoparticles. The information can be used to tailor the adhesion properties of nanoceria by optimizing the size distribution as well as surface roughness as a function of water to surfactant ratio.

Bacteriorhodopsin (bR) is a membrane protein found in the archae Halobacterium salinarum. Here, we studied wild type bR and especially the triple mutant bR, 3Glu [E9Q/E194Q/E204Q], in combination with wide gap semiconductor TiO 2 for their suitability as efficient light harvester in solar cell. Our differential scanning calorimetry data show thermal robustness of bR wild type and 3Glu mutant, which make them good candidates as photosensitizer in solar cells. Molecular modeling indicates that binding of bR to the exposed oxygen atoms of anatase TiO 2 is favorable for electron transfer and directed by local, small distance interactions. A solar cell, based on bR wild type and bR triple mutant immobilized on nanocrystalline TiO 2 film was successfully constructed. The photocurrent density-photo voltage (J-V ) characteristics of bio-sensitized solar cell (BSSC), based on the wild type bR and 3Glu mutant adsorbed on nanocrystalline TiO 2 film electrode were measured. The results show that the 3Glu mutant displays better photoelectric performance compared to the wild type bR, giving a short-circuit photocurrent density (J SC ) of 0.09 mA/cm 2 and the open-circuit photovoltage (V OC ) 0.35 V, under an illumination intensity of 40 mW/cm 2 .

Spontaneous assembly of long chains of nanoparticles (NPs) has been experimentally observed for many different materials including nanocolloids of semiconductors, metal oxides, and metals. While the origin of dipole moment in various colloids can be different, a universal explanation of chain assembly can be provided by the hypothesis of dipole-dipole attraction of nanocolloids. In this paper, we describe the application of the Monte Carlo method for modeling of self-organization of large ensembles of NPs. As the first approximation, the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory provides an adequate description of self-organization of several hundreds of NPs. Unlike microscale colloids that served as a classical model for DLVO, we used a distance-dependent media dielectric constant. The simulated chains are morphologically and geometrically similar to those observed experimentally. This establishes the fundamentally important ability of NPs to self-assemble due to their intrinsic anisotropy. Thermodynamic analysis of Monte Carlo results reveals the role of partial removal of the stabilizer shell in CdTe nanocolloids necessary for reduction of interparticle repulsion. Analysis of the field distribution around short chains demonstrates that the growth of linear agglomerates is kinetically controlled by a high activation barrier for NPs approaching from all of the directions except one end of the chain. The presented algorithm can be applied to other interparticle interactions, such as induced dipoles, which can stimulate chain formation in the absence of permanent dipole moment. It can also serve as a theoretical foundation for the understanding of the large complex superstructures forming from anisotropic and anisometric NPs. Monte Carlo simulation of nanoscale dipoles can also be extended to the interactions of NP with proteins, and related biological systems important for a variety of applications in medicine.

Mg-Gd-Mn nanoferrites with formulae Mg 0.9 Mn 0.1 Gd y Fe 2 À y O 4 , where y¼ 0.05, 0.1, 0.2 and 0.3, have been synthesized by solution combustion technique. The dc resistivity was observed to decrease with the increase in temperature. Dielectric constant (ε′) and loss tangent (tan δ) have been found to be increasing with an increase in temperature while with an increase in frequency both have been found to be decreasing. The ac electrical conductivity (s ac) has been studied as a function of temperature at different frequencies and has been observed to be increasing with the increase in temperature. The Mössbauer spectroscopy has been carried out so as to authenticate our previously reported results on the superexchange interactions.

The present work reports on the influence of the dispersion quality of multiwall carbon nanotubes (MWCNTs) in a silicone matrix on the marine fouling-release performance of the resulting nanocomposite coatings. A first set of coatings filled with different nanofiller contents was prepared by the dilution of a silicone/MWCNTs masterbatch within a hydrosilylation-curing polydimethylsiloxane resin. The fouling-release properties of the nanocomposite coatings were studied through laboratory assays with the marine alga (seaweed) Ulva, a common fouling species. As reported previously (see Ref. [19]), the addition of a small (0.05%) amount of carbon nanotubes substantially improves the fouling-release properties of the silicone matrix. This paper shows that this improvement is dependent on the amount of filler, with a maximum obtained with 0.1 wt% of multiwall carbon nanotubes (MWCNTs). The method of dispersion of carbon nanotubes in the silicone matrix is also shown to significantly (p = 0 05) influence the fouling-release properties of the coatings. Dispersing 0.1% MWCNTs using the masterbatch approach yielded coatings with circa 40% improved foulingrelease properties over those where MWCNTs were dispersed directly in the polymeric matrix. This improvement is directly related to the state of nanofiller dispersion within the cross-linked silicone coating.

Biosynthetic approach using an endophytic fungus is a novel way towards the development of safe, economically viable and green method for the synthesis of silver nanoparticles and thus synthesized silver nanoparticles can be used in antibacterial formulations. We report the extracellular synthesis of silver nanoparticles using an fungus F.solani sp, and their antibacterial activity against human pathogenic bacteria viz. Staphylococcus aureus, Bacillus subtilis ,Escheriachia.coli and Salmonella typhi. Detection of synthesized silver nanoparticles was carried out using UV-Visible spectrophotometer analysis, which showed a peak ranging between 420-450 nm indicating the formation of nanoparticles.

This paper will review the current state of both biological and non-biological nanotechnology and will predict the near future of this technology using physical and economic forecasting methods. Nanotechnology is defined as the precise manipulation of matter under 1 micrometer.

In this letter, we report the design and fabrication of different metal patterns for the realization of spatially controlled hydrophobic/hydrophilic regions with micrometer resolution. The fabrication procedure, based on a combination of lithographic techniques and wet-chemistry reactions (namely, spontaneous Galvanic displacement reactions) is reliable, undemanding, and highly versatile, allowing the achievement of precise spatial control along with the use of a wide variety of different materials. Jani, H.; Plessis, J. D.; Coloe, P. J.; Bhargava, S. K. Adv. Mater. 2008, 20, 717-723. (c) Liang, H. P.; Zhang, H. M.; Hu, J. S.; Guo, Y. G.; Wan, L. J.; Bai, C. L. Angew.

A newly developed method for synthesized and characterized nanocotton extracted from linter (short fibers during the spinning processes from the Egyptian cotton long fibers) was investigated. Acid hydrolysis followed by mechanical pulverized and finally 20 KHz high power ultrasonic was used in synthesized of the nanocotton. Characterization of the prepared sample was confirmed, using particle size distribution, X-Ray diffraction (XRD) and Scanning Electron Microscope (SEM). The particle size distribution results of the sample showed that the average diameter was 70.54, and width, 11.61nm. SEM study showed that the diameter of the sample was about 25 nm to 65 nm. X-ray analysis shows obviously that the crystallinity of the cotton decreases with their particle size.

Iron oxide thin films have been obtained by spray pyrolysis using 100% methanolic and ethanolic solutions of iron trichloride. The films were deposited onto ITO-coated glass substrates. The preparative conditions have been optimized to obtain compact, pin-hole-free and smooth thin films which are adherent to the substrate. The structural, morphological and compositional characterizations have been carried out by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The films deposited using ethanolic solution results into pure hematite; a-Fe 2 O 3 thin films, however, films deposited using methanolic solution consists of hematite and maghemite-c phases of iron oxide. The films are nanocrystalline with particle size of 30-40 nm. The optical absorbance of the film was of the order of 10 5 cm À1 . The optical band gap of films was found to be 2.26 and 2.20 eV for the films deposited using methanolic and ethanolic solutions, respectively.

One-dimensional nanostructures exhibit interesting electronic and optical properties due to their low dimensionality leading to quantum confinement effects. ZnO has received lot of attention as a nanostructured material because of unique properties rendering it suitable for various applications. Amongst the different methods of synthesis of ZnO nanostructures, the hydrothermal method is attractive for its simplicity and environment friendly conditions. This review summarizes the conditions leading to the growth of different ZnO nanostructures using hydrothermal technique. Doping of ZnO nanostructures through hydrothermal method are also highlighted.

Zinc oxide nanostructures were prepared by sol-gel method without using any chelating agents. The structural and optical properties of the nanostructures were studied. The precursors were annealed at 400 °C and 800 °C for 24 hours and characterized using X-Ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The band gap energies were analyzed by using a UV-Vis spectrophotometer. Based on the XRD results, all materials were single phase with the hexagonal structure without any impurities presents. Based on the FESEM results, it was found that the morphology for the materials annealed at 400 °C has nanorod shape while for the materials annealed at 800 °C, they have spherical shape. It was found that the band gap energies of the ZnO nanomaterials were dependent on the morphology of the nanostructures.

A novel unsymmetrically substituted phthalocyanine, which contains an extended planar core and a pair of adjacent peripheral hydroxyl groups is synthesised and used to prepare planar phthalocyanine oligomers. These materials act as macrodiscotic liquid crystals giving a columnar mesophase, which is stable over a large temperature range.

Boron doped and undoped Poly(vinyl) alcohol/Zirconium-yttrium acetate (PVA/Zr-Y) nanofibers were prepared by electrospinning using PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and thermal properties. The effect of boron doping on calcined yttria stabilized zirconia (YSZ) fibers were evaluated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis. XRD
analysis revealed varying amounts of monoclinic and tetragonal zirconia present in the undoped fibers calcined at 800oC. The average crystallite sizes of the undoped YSZ were increased from 9.28 to 22.79 nm with calcining temperature increasing from 250 to 800 °C. The crystallite size was enhanced with boron doping. The systematic evolution of morphological features in the spun and the processed fibers were employed by scanning electron microscopy.

Metal matrix nanocomposites (MMNCs) could be strong candidates for use in the automotive and aerospace industry, where the mechanical performance is a crucial factor. This study aims to determine the feasibility of Al/SiC nanocomposite fabrication by the ultrasonic technique for the production of thixoforming feedstock material. Aluminium (A356) matrix composites were fabricated with the addition of 0.2 wt.% SiC nanoparticles using an ultrasonic method. Two different particle feeding mechanisms; the Al foil double capsulate method and the crucible placement approach, were employed. Better results were obtained for the double capsulate method. Also, Ti and Nb probe tips were tried to provide ultrasonic vibration in the melt. It has been shown that Nb is a promising ultrasonic probe tip material to produce MMNCs above 650 °C as it is thermodynamically stable in comparison with Ti.

The present study describes a simple and reliable I-V technique for detection of Nebivolol drug based on as-grown un-doped silver oxide nanoparticles at room conditions. Here, we have synthesized largescale and low-dimensional silver oxide nanoparticles by a wet-chemical technique using reducing agents in alkaline medium. The morphological, structural, elemental, and optical properties of nanoparticles are investigated by UV/vis. and FT-IR spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FESEM) etc. They were fabricated on a glassy carbon electrode (GCE) to give a fast response towards nebivolol drug. The nebivolol drug sensor also displays good sensitivity and long-term stability, and enhanced electrochemical I-V response. The calibration plot is linear (r 2 = 0.9294) over the broad concentration range (5.46 nM ~ 99.3 μM). The sensitivity and detection limit are calculated from the calibration plo...

The discovery of graphene made the researchers interested towards the other two-dimensional materials which has quite similar properties like graphene. Among them, MoS2 nanosheet has extraordinary optoelectronic and physical properties. It has several applications in developing battery, sensor, optoelectronic device, etc. On the other hand, amorphous carbon nanotube can be synthesized by using a low temperature chemical process. Due to the easy processing of amorphous carbon nanotube (ACNT), good optoelectronic and physical property based nanomaterial with amorphous carbon nanotube, can be a good replacement of crystalline carbon nanotube in numerous applications. Here in this paper, amorphous carbon nanotube-MoS2 nanohybrids were prepared by hydrothermal method. Beside this, ACNT has been synthesized by using a low temperature chemical process. The as prepared samples (ACNT and ACNT-MoS2 nanohybrids) were characterized by using field emission scanning electron microscopy, X-ray diffraction method, high resolution transmission electron microscope and fourier transform infrared spectroscopy method.

Nanoparticles of Bi0.95Mn0.05FeO3 and Ni0.5Zn0.5Fe2O4, synthesized using sol-gel autocombustion method, were mixed with the chemical formula (x).Bi0.95Mn0.05FeO3-(1-x).Ni0.5Zn0.5Fe2O4, where x takes the values of 0, 0.5, 0.6, 0.8 and 1 to prepare multiferroic composites. The sintering of the materials was done at 800 o C for 6 h in air atmosphere. Dense and homogeneous compounds with fine grained microstructures were achieved in all the composite samples as evident from the obtained scanning electron micrographs. Structural analyses of the composites were carried out using X-ray diffraction and FTIR spectroscopy and the obtained data suggests formation of diphase compounds with meek interfacial diffusion while retaining the major individual perovskite and spinel phases in all the composites. Dielectric studies as a function of temperature reveals that there is a phase transition in the composites in each case around the Neel temperature which manifests not only a transition from ferrimagnetic to paramagnetic but also a vanishing magnetoelectric order between the constituent phases. Room temperature magnetic hysteresis loops were taken using vibrating sample magnetometer. The saturation magnetization was found to increase according to the constituent percentage of the ferrite content added to the composite. Superparamagnetic behavior with close to zero coercivities was observed for all the samples. Polarization-electric field (P-E) loops provide the evidence for the existence of spontaneous polarization in all the composites. The preservation of both the ferroelectric and ferrimagnetic phases with required degree of interfacial coupling between them in these composites makes them an attractive choice for sensor and spintronic applications.

The challenge of realizing electronic devices based on organic materials started in the early 70‟s. The discovery and advent of conducting polymers in the 80‟s paved the way to new solution-based process and realization of cheap and flexible electronic devices. Mastering thin films fabrication by evaporation techniques also made possible devices realization with optimal properties and control. Organic electronics is nowadays becoming a mainstream innovative field, with perspectives in solar cells, lightning and cheap electronics. The first industrial products are emerging in our every day‟s life, for example in screens for portable electronics. From another perspective, electrical transport through molecules, or entities of molecular size or thickness, created a growing interest in the research community. The development has been slower, mostly hindered by the technical issue of matching the nm molecular size with the typical 100 nm electrical interconnects sizes. This is illustrated by the scientific literature on the topic, with large fractions of the publications related to theoretical studies and nanofabrication methodologies, leaving aside only a marginal numbers of experimental results reports. The field of molecular electronics has nevertheless matured, and initial high expectations are nowadays moderated by the reality of difficulties in reuniting the molecular and macroscopic worlds. In particular, the scanning probe studies on molecules deposited on surfaces illustrated that stability usually require cryogenic temperatures, and the intrinsic conductivity of the molecules under study can be remarkably modified by the environment, the molecules conformations, and details of its interactions with the substrate. These points illustrate how difficult it is to create molecular devices of reproducible and robust properties. Tackling molecular electronics problems through size reduction of „standard‟ organic electronics systems also have stringent limits. The progress in this field cannot be compared to progress in miniaturization of inorganic silicon-based electronics. The primary technical bottleneck to miniaturization is metal-organic interfaces, which have a large importance for organic devices, and easily become predominant for sub-micrometer sizes. A huge research effort has been dedicated to this problem in the last 15 years, aiming at better for better characterization and understanding of dielectric-organic and metal-organic interfaces joining two materials of very different electronic properties. In the midway between bulk organic electronics and single molecule devices, are molecular electronic devices in the size range of 10-100 nm. This thesis is mostly dedicated to investigate these intermediate size devices. We envision several key advantages: (1) direct top-down nanofabrication tools can be used to fabricate reliable and reproducible interconnects in the 50 – 100 nm size range, (2) we can use bottom up fabrication methodologies to create molecular-based materials of size exceeding a few tens of nanometers, (3) by targeting devices where transport occurs though a significant number of molecules, we get access to average properties, with the advantage of studying more robust and reproducible samples, with expected environmental stability making ambient conditions measurements possible. Our ambition is to convince the reader that this mid-sized devices approach is promising, with high potentials. Our ambition is to provide a solid ground for molecular electronics devices realization, where reliability and results confidence are priorities. This explains why, all along this thesis, a large number of control experiments have been performed. This thesis is essentially articulated in three sections. In the first section (Chapter II), we present our methodology for creating the electrodes circuit, the interconnects, the excitation and measurement environments. Light is used as a trigger or excitation source, illustrating how molecular devices can have controlled properties, making them potential candidates for devices properties beyond those of standard inorganic electronics. For this aim, the setup for electrical measurements is placed in a home built-interconnect setup over an inverted optical microscope where we can apply simultaneous optical-electrical measurements followed by temperature and magnetic field complementary studies. We report the fabrication of lateral electrodes with high aspect ratio (104) separated by a 20-100 nm distance, and using simple optical lithography techniques. These „nanotrenches‟ are our basic top-down tool for interfacing organic materials. The next section (Chapter III) is a proof-of-principle experiment, showing that we can create robust molecular electronics devices. The best experimental confirmation for the occurrence of molecular-type transport relates to the study of „switching‟ molecules. Such systems exhibit a reversible, and possibly hysteretic, modification of their properties under external stimulus. For experimental convenience reasons, aiming at minimizing the risks of experimental artifacts, we use a benchmark molecular system, choosing a photochromic molecular film. These molecules are known to reversibly exhibit a change of conformation (cis↔trans) under light excitations in the UV and blue ranges. We use a microsphere coated with a film of these molecules, and trapped over the nanotrench. The sphere is the intermediate size connector, closing the junction between metallic electrodes through a double molecular layer. While a light induced change of conduction has been shown in a vertical geometry in these molecules, the lateral geometry is unexplored. On-switching molecular films as check system, we provide quantitative success rate in observing electrical transport unambiguously related to molecules properties, reaching a success rate better than 90%. The third section (chapters IV and V) presents the use of our methodology to investigate original new molecular materials. The spincrossover phenomenon, occurring as a collective transition with hysteretic behavior triggered by a change in temperature, pressure or irradiation in transition metal complexes, from paramagnetic high spin state (HS, S=2) to diamagnetic low spin state (LS, S=0) has been studied thoroughly in the literature, and well suites as switching molecular system. The transition is often accompanied by a change in color, dielectric constant and volume of the bulk material. Studies have shown that due to the collective nature of the transition, the hysteresis occurs in an ensemble of molecules and not in single molecules, thus spincrossover nanostructures are ideal candidates for observing the physical change (volume) due to the transition and we aimed to detect this change in their transport properties in chapter IV. We therefore used original spin crossover nanoparticles, of well-characterized spin transition properties, positioned over 100 nm-size gaps. The obtained results do not relate to spin transition, but to other intrinsic properties of the particles (high conductivity and photoconductivity) and confirmed that this geometry and size scale opens a view to novel properties investigation. The other molecular system is designed for supramolecular electronics studies, where the bottom-up fabrication involves the construction of a large molecular architecture, of size matching the nanotrenches widths. We investigate a self-assembled molecular system based on a triarylamine derivative as building block. Light triggers a polymerization of these molecules, through radicals creation in the solution. When this growth procedure is probed between metallic electrodes, a surprising self-fabrication of highly conductive molecular wires parallel to the linesof electric field in the gap is observed. The wires have an ohmic character with conductivity values of 104 S.m-1 combined with an extremely low interface resistance, typically six orders of magnitude lower than conventional polymers, samples exhibit high environmental stability persisting for a long time. This "discovery‟, detailed in chapter V, represents a milestone discovery for organic electronics since it describes the first molecular self-assembly having intrinsic metallic behavior in both bulk and at the metal/organic interface when lowering the temperature down to 1.5 K. Once again we emphasize the importance of the intermediate sized devices in making progress in the field of molecular electronics, by discovering materials with novel intrinsic properties and taking a great step towards lowering the parasitic interface resistance of organic materials with metals using self-fabrication procedures.

This article presents an investigation of the temperature induced modification in the microstructure and dynamics of poly[2-methoxy-5-(2 0 -ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) cast films using Wide-Angle X-ray Scattering (WAXS), solid-state Nuclear Magnetic Resonance (NMR), and Fluorescence Spectroscopy (PL). MEH-PPV chain motions were characterized as a function of temperature by NMR. The results indicated that the solvent used to cast the films influences the activation energy of the side-chain motions. This was concluded from the comparison of the activation energy of the toluene cast film, E a = (54 ± 8) kJ/mol, and chloroform cast film, E a = (69 ± 5) kJ/mol, and could be attributed to the higher side-chain packing provided by chloroform, that preferentially solvates the side chain in contrast to toluene that solvates mainly the backbone. Concerning the backbone mobility, it was observed that the torsional motions in the MEH-PPV have average amplitude of $10°at 300 K, which was found to be independent of the solvent used to cast the films. In order to correlate the molecular dynamics processes with the changes in the microstructure of the polymer, in situ WAXS experiments as a function of temperature were performed and revealed that the interchain spacing in the MEH-PPV molecular aggregates increases as a function of temperature, particularly at temperatures where molecular relaxations occur. It was also observed that the WAXS peak associated with the bilayer spacing becomes narrower and its intensity increases whereas the peak associated with the interbackbone planes reduces its intensity for higher temperatures. This last result could be interpreted as a decrease in the number of aggregates and the reduction of the interchain species during the MEH-PPV relaxation processes. These WAXS results were correlated with PL spectra modifications observed upon temperature treatments.

A new mechanism for the surface instability and dewetting of thin films on chemically heterogeneous substrates is identified and simulated. The time scale for instability varies inversely with the potential difference due to the heterogeneity. Heterogeneities can even destabilize spinodally stable films, reduce the time of rupture substantially for thicker films, and produce complex and locally ordered morphological features (e.g., ripples and castle-moat structures, lack of undulations before hole formation) that are not predicted by the spinodal mechanism. PACS numbers: 68.15. + e, 47.20.Ma, 47.54. + r, Ultrathin fluid films (e.g., coatings) on solid substrates have attracted widespread interest in recent years [6]. The current theoretical understanding of thin film stability, dynamics, and morphology is limited to films on chemically homogeneous substrates. Such films are rendered unstable by a spinodal mechanism whenever the excess intermolecular interaction energy per unit area (DG) shows positive curvature with respect to the film thickness, h, e.g., when the effective Hamaker constant, A s is positive for the long-range van der Waals interaction. Deliberately tailored chemically heterogeneous substrates are increasingly being used to engineer desired nano-and micropatterns in thin films . Also, experiments even on the substrates that were thought to be relatively homogeneous show remarkable departures from the theory of spinodal dewetting [6]. These observations have repeatedly suggested the involvement of heterogeneous sites, e.g., dust, trapped microcavities, chemical contamination, variation of oxide layer thickness on silicon, variable chain adsorption, etc., all of which generate localized patches of surface properties or potential different from the surrounding substrate, as shown in . This Letter proposes and simulates a new mechanism of thin film instability and its evolution on chemically heterogeneous substrates. The general dynamical and morphological features of the instability are then clearly contrasted with the spinodal dewetting. One of our main results is that the heterogeneities, even on length scales substantially smaller than the spinodal scales can greatly accelerate the growth of surface instabilities and can even engender the rupture of spinodally stable films.