Attieh A. Al-Ghamdi

Development of Fe/Fe3O4 core-shell nanocubes as a promising magnetic resonance imaging contrast agent.

Here, we report the synthesis, characterization, and properties of Fe/Fe3O4 core-shell nanocubes prepared via a simple route. It includes NaBH4 reduction of FeCl3 in an ethylene glycol solution in the presence of 2-mercaptopropionic acid (surfactant) and trisodium citrate (cosurfactant) followed by surface oxidation with trimethylamine N-oxide. The morphology and structure of Fe/Fe3O4 core-shell nanocubes were characterized using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, X-ray powder diffraction, and X-ray photoelectron spectroscopy. All of the methods confirm a Fe/Fe3O4 core-shell structure of nanocubes. Magnetic measurements revealed that the Fe/Fe3O4 core/shell nanocubes are superparamagnetic at 300 K with a saturation magnetization of 129 emu/g. The T2 weighted imaging and the T2 relaxation time showed high MRI contrast and sensitivity, making these nanocubes viable candidates as enhanced MRI contrast agents.

Fluorescence anisotropy by use of optical Kerr gating with incoherent laser light

Incoherent fluorescence optical Kerr gating can in principle be used to measure fluorescence anisotropies and determine molecular reorientational times. A novel method for fluorescence anisotropy by use of optical Kerr gating with incoherent laser light is presented. Incoherent optical Kerr signals have been obtained for parallel and perpendicular fluorescence polarization for a 10(-3)-M solution of Rhodamine 6G in ethanol.

A novel conducting nanocomposites containing phenolic resin/carbon nanoparticles for electromagnetic wave shielding effectiveness at microwave frequency

The microstructure of phenolic resin reinforced carbon black (CB) nanoparticles was examined by scanning electron microscopy. The thermal stability of the nanocomposites was examined by means of isothermal resistivity change at 100°C. Electromagnetic interference (EMI) response of conducting phenolic/CB nanocomposites in the frequency range from 1 GHz to 12 GHz has been studied. In the microwave range from 8 to 12 GHz conducting nanocomposites shows a shielding effectiveness in the range 30-40 dB. The highest EMI of nanocomposites was 55 dB for CB12 sample which is realistic for an industrial application. The results of this study demonstrate the high possibility of using the proposed nanocomposites as electronic conductive fillers in polymer package and EMI shielding effectiveness at microwave frequency.

New resistive switching and self-regulating heating in foliated graphite/nickel polyvinyl chloride nanocomposites

Polyvinyl chloride- (PVC-) based nanocomposites containing nanosized graphite and nickel nanoparticles (GN) as conductive fillers to achieve positive temperature coefficient of resistance (PTCR) thermistors and self-regulating heater function have been successfully fabricated. The microstructure of the foliated graphite and nanocomposites was examined by scanning electron microscopy (SEM). The effect of GN content on the static electrical conductivity, carriers mobility, and number of charge carriers of the nanocomposites was studied. The applicability of nanocomposites as PTCR thermistors was examined by monitoring the conductivity as a function of temperature. It is found that the conduction mechanism in PVC/GN nanocomposites is governed by tunneling mechanism. Also, the applied voltage versus current and temperature were studied to check the applicability of composites as self-regulating heater. The results show that the PVC/GN nanocomposites might have potential applications in PTCR devices, self-regulating heater, and temperature sensors.

Establishing an infrared measurement and modelling capability

The protection of own aircraft assets against infrared missile threats requires a deep understanding of the vulnerability of these assets with regard to specific threats and specific environments of operation. A key capability in the protection of own assets is the ability to perform infrared measurements, analyse the data and construct signature models of aircraft, countermeasures and the background. The creation of such a capability is a complex task. A framework for capability development was used to identify all required elements and to ensure an optimal and complete programme. Topics covered include Personnel, Organisation, Support, Training, Equipment, Doctrine, Facilities, Information and Technology (POSTEDFIT). This paper reports on the process that was followed and its initial outcome after a two year project was concluded.

Fluorescence anisotropy of rhodamine 6G using incoherent laser light

A novel method for fluorescence anisotropy using incoherent laser light is presented. The incoherent upconversion technique to measure picosecond molecular motion of rhodamine 6G is investigated experimentally.

New non-linear electrical-thermal switching of carbon nanoparticles/silane coupling agent reinforced phenolic resin nanocomposites

This paper evaluates the use of a new multifunctional conducting polymer containing phenolic resin reinforced by carbon black (CB) nanoparticles modified by silane coupling agent to produce positive temperature coefficient (PTC) thermistors and switching current. The percolation threshold of the conducting composites at room temperature was found to be as low as 4 wt% of CB. Temperature dependent electrical characterisation of phenolic resin/CB nanocomposites is performed. The composites exhibit PTC properties with ρmax/ρmin value as great as 104. Electrical parameters such as charge carriers type, drift mobility, concentration of charge carriers, activation and hopping energy are verified with CB content. The current-voltage curves of the nanocomposites change from linear to non-linear behaviour and the switching current is observed within the non-linear regime.

Fluorescence anisotropy of rhodamine 6G using OKG with incoherent laser light

Incoherent fluorescence optical kerr gate can be used in principle to measure fluorescence anisotropies and determine molecular reorientational times. In this work a novel method for fluorescence anisotropy using Optical Kerr Gating with incoherent laser light is presented. We have obtained incoherent optical kerr signals for parallel and perpendicular fluorescence polarization for a 10-3 M solution of rhodamine 6G in ethanol.