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Electrons are the greenest reducing agent for the preparation of highly dispersed noble metal catalysts. Two methods have been developed with electrons as the reducing agent: electron beam irradiation and room-temperature electron reduction with glow discharge or radio frequency discharge as the source of electrons. In this perspective, we attempt to summarize the current status of electron reduction with those non-hydrogen discharges as the electron source. Future developments have been addressed, too. The room-temperature electron reduction via discharges is excellent for size control with fast nucleation and slow crystal growth. It is a simple, easy, cheap, and energy efficient way to reduce metal ions. It is also worthwhile to load noble metal particles into channels of ordered porous materials, like SBA-15, with no need for complex chemical modification. The roomtemperature operation makes it very useful for the preparation of noble metal catalysts supported on thermal sensitive substrates like porous organic materials, conducting polymers, ultrahigh surface area carbon, peptides, and proteins.

A kind of absorbable PLGA microbubble-based contrast agent (PLGA microspheres with porous or hollow inner structure) was fabricated by an improved double emulsion-solvent evaporation method. The contrast efficiency was evaluated and proved both in vitro and in vivo. By adjusting the polymer concentration and volume of the inner aqueous phase during the fabrication of microbubbles, the inner structure of the microbubbles could be controlled. Both air-filled and perfluoropropane-filled microbubbles can opacify the left ventricle. However, when compared with air-filled microbubbles, perfluoropropane-filled microbubbles can produce significantly longer enhancement in left ventricle in the dog model due to the lower diffusivity and lower solubility of perfluoropropane in blood. A suspension of perfluoropropane-filled PLGA microbubbles (1.8 microm average microbubbles size, 2 x 10(8) microbubbles/mL concentration) has successfully and safely achieved myocardial opacification in closed-chest dogs. A perfusion defect was observed in both of the two dogs with acute myocardial infarction with Power Contrast Imaging (PCI) triggered technology. In the examination of contrast in both ventricular and myocardial opacification, the high mechanical index (MI) was found to have superior contrast sensitivity over the low MI for PLGA-based contrast agents.

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