New Trends in Nanoparticles: Syntheses and Their Applications to Fuel Cells, Health Care, and Magnetic Storage

Abstract

This paper reviews important research on chemical and electrochemical synthesis and application of nanoparticles, especially our recent results in this field: (i) catalytic metal nanoparticles for micro‐fuel cells, (ii) magnetic oxide nanoparticles for drug delivery systems, and (iii) magnetic metal nanoparticles for magnetic recording media. To fulfill the requirements of each application, we chose and modified those synthetic methods for obtaining suitable properties, e.g., morphology, catalytic activity, and magnetic properties. (i) For micro‐fuel cells, electrodeposition is attractive because of its selective deposition onto current collectors and possible elimination of an annealing process. As a result, we have successfully synthesized Pt, PtRu alloy, and PdCo alloy, which consisted of dendritic structures macroscopically and of interconnected nanoparticles microscopically. (ii) For drug delivery systems, since magnetic nanoparticles should possess ferromagnetism, be dispersible in water, and be nontoxic, Fe3O4 nanoparticles synthesized by hydrolysis in aqueous media are suitable. As a result, we have successfully controlled the size (10–40 nm in diameter) and the magnetic properties of Fe3O4 nanoparticles by means of adjusting the molar ratio of ferrous to ferric ions in the precursor solution. (iii) For magnetic recording materials, since magnetic nanoparticles should possess high coercivity, a controlled shape, and a uniform small size, we have modified a chemical method for synthesizing FePt by adjusting the growth temperature. As a result, we have succeeded in synthesizing FePt nanoparticles with a controlled shape (cubic) and a uniform size (ca. 5.6 nm).

Sub-nanometer dimensions control of core/shell nanoparticles prepared by atomic layer deposition

“…Hence, turning this drawback into an opportunity, ALD can also be considered as a new route for the synthesis of metallic NPs [25]. It allows for the deposition of highly dispersed NPs on high aspect ratio substrates [26,27], which is very relevant for heterogeneous catalysis applications [26,28,29]. Various highly dispersed NPs of platinum group metals, such as Ru [30], Ir [31], Pt [27] and Pd [32], have been synthesized by ALD recently, and it has been demonstrated that their diameter can be controlled at the nanometer-level by simply tuning the number of ALD cycles applied.…”

On-chip fuel cells for safe and high-power operation: investigation of alcohol fuel solutions

“…Finally, Pd-Co alloy was electrodeposited as the cathode catalyst at À200 mA cm À2 for 60 s in a solution containing an ammonia complex of Pd(II) and a malonic acid complex of Co(II), and Pt-Ru alloy was electrodeposited as the anode catalyst by applying a pulse current, as reported previously. 18,22 Details of the electrodeposition processes are described in the ESI †.…”

Combining nanoparticles grown by ALD and MOFs for gas separation and catalysis applications

“…Metallic nanoparticles (NPs) have gained a lot of interest in research because they can be applied in many different fields, such as biomedicine, 1 magnetic recording, 2 plasmonics, 3 water purification 4 and, most importantly, heterogeneous catalysis. 5,6 Heterogeneous catalysis is by far the main application of metallic NPs.…”