Nanometer sized silver particles were synthesized by inert gas condensation and co-condensation techniques. Both techniques are based on the evaporation of a metal into an inert atmosphere with the subsequent cooling for the nucleation and growth of the nanoparticles. The antibacterial efficiency of the nanoparticles was investigated by introducing the particles into a media containing Escherichia coli. The antibacterial investigations were performed in solution and on petri dishes. The silver nanoparticles were found to exhibit antibacterial effects at low concentrations. The antibacterial properties were related to the total surface area of the nanoparticles. Smaller particles with a larger surface to volume ratio provided a more efficient means for antibacterial activity. The nanoparticles were found to be completely cytotoxic to E. coli for surface concentrations as low as 8 microg of Ag/cm2.

Three dimensional terahertz pulsed imaging (TPI) was evaluated as a novel tool for the nondestructive characterization of different solid oral dosage forms. The timedomain reflection signal of coherent pulsed light in the far infrared was used to investigate film-coated tablets, sugar-coated tablets, multilayered controlled release tablets, and soft gelatin capsules. It is possible to determine the spatial and statistical distribution of coating thickness in single and multiple coated products using 3D TPI. The measurements are nondestructive even for layers buried underneath other coating structures. The internal structure of coating materials can be analyzed. As the terahertz signal penetrates up to 3 mm into the dosage form interfaces between layers in multilayered tablets can be investigated. In soft gelatin capsules it is possible to measure the thickness of the gelatin layer and to characterize the seal between the gelatin layers for quality control. TPI is a unique approach for the nondestructive characterization and quality control of solid dosage forms. The measurements are fast and fully automated with the potential for much wider application of the technique in the process analytical technology scheme. ß

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We demonstrate the critical effect of postgrowth annealing temperature on the properties of low-temperature-grown GaAs. By using annealing temperatures substantially below the 500–600 °C commonly reported, GaAs with high resistivity and with carrier lifetimes as short as 100 fs can be routinely obtained. We discuss the optimum, but different, anneal conditions required for terahertz photoconductive emitters and detectors, and illustrate their use in a continuous-wave system.