No abstract

A memory effect has been demonstrated in magnetic nanowire arrays. The magnetic nanowire array has the ability to record the maximum magnetic field that the array has been exposed to after the field has been turned off. The origin of the memory effect is the strong magnetic dipole interaction among the nanowires. Switching field distributions among nanowires has been studied with a first‐order reversal curve technique to elucidate the discrepancy between the experimental result and the theoretical explanation. Based on the memory effect, a novel and extremely low cost EMP detection scheme is proposed.

Size-controlled Pd nanoparticles were electrochemically synthesized in large quantities at room temperature through the direct electroreduction of bulk PdCl4 2- ions in the presence of poly(N-vinylpyrrolidone) (PVP), a water-soluble polymer. The technological key to electrochemical synthesis of Pd particles is that PVP greatly promoted the formation process of Pd particles and inhibited the electrodeposition process of Pd onto the Pt cathode at the same time besides effectively stabilizing the formed Pd nanoparticles. The as-synthesized Pd nanoparticles display the voltammetric behavior significantly different from the bulk Pd and also present a high catalytic activity toward the electrooxidation of methanol.

A simple but effective aqueous-organic phase-transfer method for gold, silver, and platinum nanoparticles was developed on the basis of the decrease of the PVP's solubility in water with the temperature increase. The present method is superior in the transfer efficiency of highly stable nanoparticles to the common phase-transfer methods. The gold, silver, and platinum nanoparticles transferred to the 1-butanol phase dispersed well, especially silver and platinum particles almost kept the previous particle size. Electrochemical synthesis of gold nanoparticles in an oil-water system was achieved by controlling the reaction temperature at 80 degrees C, which provides great conveniences for collecting metal particles at the oil/water interface and especially for fabricating dense metal nanoparticle films. A technique to fabricate gold nanofilms on solid supports was also established. The shapes and sizes of gold nanoparticles as the building blocks may be controllable through changing reaction conditions.