The primary objective of our work is to understand the nanocomposite structure of SiO2 coated over graphene (G) nanoplatelets. An attempt has been made to synthesize G-SiO2 nanocomposite using sol-gel technique. The G-SiO2 nanocomposite is characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy, FTIR spectroscopy, and Electrochemical and Electrical measurement technique, respectively. The G-SiO2 nanocomposite reveals platelets characteristics much larger in size than the graphene nanoplatelets. The conductivity of G-SiO2 has been found to increase with an increase in the graphene ratio to SiO2 in nanocomposite material. The G-SiO2 has revealed interesting feature vibrational bands of graphene with SiO2 by varying the precursor of SiO2 with graphene moieties. The cyclic voltammetry studies have indicated the diffusion controlled system. The G-SiO2 nanocomposite shows interesting current–voltage characteristics with variation of graphene in nanocomposite. Our result is indicative of a transformable and viable G-SiO2 material for energy and electrical relay applications.

We report on the laser interference patterning of as-spun block copolymer films on silicon and silicon dioxide substrates. Our process involves the use of a pulsed laser light source of 266 nm wavelength and any type of diblock copolymer as a positive tone photoresist, resulting in the generation of sub-micron domains of different geometries and periodicity. This non-solvent based method is robust, and when combined with the inherent nano-scaled periodicity in block copolymers, can produce hierarchical patterns on substrates with potential use in the electronics and semiconductor industries.

At INFN-LNS we have developed a new kind of gamma mini-sensor, which allowed to implement a prototype array of modular sensors for online monitoring of radioactive waste. The sensors are based on Silicon PhotoMultipliers and scintillating fibers sensitive to gamma radiation, that have to be placed in a repository in shape of a fine grid, around each single waste drum. We simulated the counting response of thin scintillating fibers and verified the results with measurements using radioactive sources. Front-end electronics and an FPGA-based counting system were developed to handle the field data, also implementing data transmission, a graphical user interface and a data storage system. Moreover a test of four sensors in a real radwaste storage site was performed with promising results.

The purpose of this work is to compare the results obtained from three methodologies intended to estimate kinetic parameters describing quantitatively the grain growth during equiaxed eutectic solidification in order to identify the best procedure to characterize grain growth kinetics. A heat transfer / solidification kinetics model is implemented to simulate the cooling and solidification of eutectic Al-Si and eutectic cast iron in sand molds. Using simulated cooling curves and volume grain density data generated by the model, the three methods are applied to obtain their predicted grain growth coefficients. The predicted results are compared with the grain growth coefficients used in the model. The outcome of this work suggests that two of the three methods under study represent the best option to obtain the kinetic parameters of equiaxed growth during eutectic solidification.

Successful experimental strategy in the high throughput world requires coordination of the statistical planning of the experimental program with the optimization of the workflow for efficient use of robotic workstation resources.

We investigated pure FCC metals including Aluminum, Nickel, Silver, and 70/30 Copper Zinc (alpha-brass) alloy for the indentation size effect (ISE) and the bilinear behavior using a single Berkovich indenter tip in a single test machine. The results were consistent with those reported by Elmustafa and Stone, 2003 of the ISE and the bilinear behavior using two separate indenter tips (Berkovich and Vickers) from two separate machines. This behavior is mechanistic in nature and is observed regardless of the type of the self similar indenter tip employed. Furthermore, the research presented in this paper would seem to also validate the conclusions that Elmustafa et al (2004) articulate that the Strain Gradient Plasticity collapses at small scales and that the bilinear behavior of these FCC metals is attributed to the presence of long range shear stresses induced by geometrically necessary dislocations. Also, we observed what has been defined as a “tapping” issue for materials with high E/H ratios when using the CSM. The CSM protocol results in erroneous hardness results at very shallow depths for high E/H ratio soft metals due to the so called “tapping” of the stylus as articulated by Pharr et al. (2009). This method should only be used as a secondary technique to the load control protocol when examining the ISE effect.

To fully accomplish all promises and hopes on clinical applications of carbon nanotubes, it is crucial to understand their interactions with physiological environment. One of these applications is polymer fillers, and it is important to review the toxicology of carbon nanotubes themselves because some polymer matrices may be biodegradable. Therefore, the interactions with organic molecules such as water, electrolytes, and proteins are reviewed and results of multiple studies on cellular interaction, cytotoxicity, immune response, biodistribution, and biopersistence are further presented. Finally, a section describing the interaction of polymer matrices with carbon nanotube reinforcements and the physiological environment is presented.

Cadmium Sulphide (CdS) thin films have been prepared on ultrasonicated glass substrates using a specially designed chemical bath deposition technique via isochronal synthesis. The structural properties have been determined through XRD. The nanostructures have been identified in FE-SEM images. The chemical analysis has been carried out through EDAX. Optical analysis and PL studies were carried out on these films. The growth conditions and the characterization results exhibit strong dependence on the pH of the precursor solution as well as the temperature of the bath. Cu doping has been employed on the tailored films to make them low resistive and efficient for window layer applications.

The influence of negative substrate bias on the chemical, electrical and mechanical properties of silicon carbide (SiC) thin films deposited onto (100) silicon substrate by dc magnetron cosputtering without external substrate heating is reported. These studies were performed by using the following techniques: Rutherford backscattering spectroscopy (RBS), profilometry, Raman spectroscopy, four-point probe method and nanoindentation. The results indicate that there is a good correlation between the substrate bias voltage and the argon incorporation into SiC film, namely, the SiC films deposited under substrate bias of –200 V and –300 V have higher argon content and higher elastic modulus and hardness than those deposited at 0 V. An opposite behavior was found for electrical resistivity: the SiC deposited at –300 V has resistivity of 0.45 Ω.cm whereas the deposited at 0 V has 7.0 Ω.cm.

The effect of an external electric field during post-annealing on the device characteristics of poly(3-hexylthiophene) (P3HT) and phenyl-C61butyric acid methyl ester (PCBM) bulk heterojunction solar cells was studied. The application of external electric field in forward bias resulted in significant enhancement in Voc and fill factor whereas devices annealed under reverse bias had an enhanced Jsc. Both forward and reverse bias annealing increased the shunt resistance. The Al - blend interface topography and carrier dynamics were studied using conducting atomic force microscopy and frequency dependent intensity modulated photocurrent spectroscopy (IMPS). The results indicate that post-annealing under external electric field can be used to engineer the interface composition to enhance the charge transport in bulk heterojunction solar cells to improve the device performance.

In the performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP), the solubility of uranium (VI) was conservatively set at 10-3 M for all expected WIPP conditions, including the potential and likely effects of carbonate complexation [1]. Under WIPP-relevant conditions, long-term experiments were performed to establish the uranium (VI) solubility limits in WIPP-simulated brine over a broad range of pCH+ values [7.5-12.5] and to evaluate the contribution of carbonate complexation and hydrolysis to uranium (VI) speciation. Data obtained in carbonate-free ERDA-6 brine, a simulated WIPP brine, were reported earlier [2]. In the absence of carbonate, uranium solubility approached 10-7 M at the expected pCH+ in the WIPP (~ 9.5). In the presence of a significant amount of carbonate (millimole levels), recent experimental results showed that uranium (VI) concentrations will not exceed 10-4M. This measured solubility limit is an order of magnitude lower than the uranium solubility value currently used in the WIPP PA [3]. A small effect of borate complexation was found in the pCH+ range [7.5-10]. At pCH+ ≥ 10, hydrolysis overwhelmed carbonate effects, and no amphoteric effect was observed.

We present a hybrid structure of Isotactic Polypropylene (iPP) nanocomposite with multiwall carbon nanotubes (MWCNTs). The polymer component contributes to the optical properties, flexibility and integrity of the polymer film while the carbon nanotubes change the thermal and mechanical stability, electrical and thermal conductivity and sensitivity. The multifunctional characteristics of this nanocomposite material are enhanced by anisotropic organization of the nanotubes and polymer through melt shearing which provides organization of the structural constituents at the molecular, nano, and micro length scales. This results in anisotropy of the macroscopic composite film properties parallel and perpendicular to the direction of shearing. On the molecular scale, the CNTs control the arrangement of the polymer molecules in a crystal lattice. On the nanometer scale, the CNTs couple to and align with the smectic normal of the liquid crystal phase of iPP. On the micron scale and larger, the secondary polymer crystal structure is rearranged due to the pinning of the polymer at the CNT surface to form fibrillar rather than spherulitic structures. These multi-scale rearrangements affect the optical, thermal, electrical, mechanical and chemical properties of the nanocomposite film. Our findings indicate that the CNTs under shear induce a novel anisotropy to the various thermo-physical properties of the iPP/CNTs films. We introduce an approach to extract the shear induced orientational order from the thermal conductivity of the dispersed CNTs. The index of refraction of the nanocomposites was also estimated via ellipsometry and was found to decrease slightly when CNTs were added and also showed shear induced anisotropy. The comparison between the results from the different experiments methods for probing induced anisotropy by melt shearing shows that orientation in iPP/CNTs nanocomposites induces anisotropy in multiple macroscopic properties.

In this paper recent advances in terahertz-wave generation in graphene are reviewed. First, fundamental basis of the optoelectronic properties of graphene is introduced. Second, nonequilibrium carrier relaxation and recombination dynamics in optically or electrically pumped graphene is described to introduce a possibility of negative dynamic conductivity in a wide terahertz range. Third, recent theoretical advances toward the creation of current-injection graphene terahertz lasers are described. Fourth, unique terahertz dynamics of the two-dimensional plasmons in graphene are described. Finally, the advantages of graphene materials and devices for terahertz-wave generation are summarized.

Semi-conducting conjugated (co)polymers are well soluble and can be processed easily in a large scale. Among these materials, rod-coil block and graft copolymers, show very particular properties of self-assembly, and are very promising in organic electronic, as organic photovoltaic materials for example.

The post-functionalization of poly(3-hexylthiophene) (P3HT) from ω-allyl terminated P3HT via various synthetic routes is reported in order to obtain well-defined block and graft copolymers for optoelectronic or photovoltaic applications. First, a well-defined and monofunctional P3HT-based macro-initiator has been obtained through a clean and versatile process. Well-defined rod-coil block copolymers were obtained by nitroxide mediated radical polymerization (NMRP) with various monomers. Finally, three different novel P3HT-based graft copolymers were synthesized following two routes.

The effects of high concentration on the photophysical properties of a nonlinear material have been of interest for some time in our group. It is well known in the literature that for a nonlinear absorbing dye to be the most effective, high concentrations are needed. The problem is that most photophysical studies in solution are done at low concentration. These low concentration studies are important for understanding inherent materials properties but it is also important to understand what happens in a material at high concentration. In addition to this, efforts have been made to study the effects of incorporating a dye into a solid matrix environment to better understand the constraints this environment has to a given material. Preliminary results for a PMMA system reveal the formation of excimers (excited state dimers) with an increase in concentration. Excimers are forming from the triplet excited state of the E1-BTF. A rate constant for this formation is 2.3 x 106 M-1 s-1. While rather slow, at high concentration the excimer is readily formed. This must be considered when making nonlinear absorption measurements since the excimer will certainly contribute to the overall nonlinearity.

Fluorescence Quenching Microscopy has been shown to be an effective means of characterizing graphene on the macroscale. Centimeter-scale CVD-grown pristine and doped graphene were manufactured in a high temperature (1000°C) furnace on pristine copper substrates. The copper was then etched away in a FeCl3solution and the graphene was coated with DCM-based fluorescent dye before being imaged in a fluorescence microscope. The fluorescence image was then image-processed using modified Matlab software. The resulting image showed clear contrast between the pristine graphene sheet and defects on the graphene surface, which revealed that fluorescence microscopy could determine the quality of a large region of graphene. Also, significant contrast was identified between single-layer and multi-layer regions, showing that this technique is also effective at determining the degree of uniformity within a graphene sample. Lastly, the fluorescence images showed contrast between doped and undoped regions of graphene.

We investigated effects of atmospheric pressure dielectric barrier discharge (DBD) plasma irradiation on growth characteristics of bread yeast (Saccharomyces cerevisie). Nitric oxide of 400 ppm and O3 above 200 ppm are produce by the DBD plasmas. DBD plasma irradiation of 50 and 100 s enhances the growth of yeast in the lag phase, whereas 150 s irradiation suppresses the growth. There is an optimum duration of plasma irradiation for the growth promotion.