Fabrication of nanoparticles with ultrafast laser pulses

Ultra-stable and extremely low-power femtosecond laser pulses are an ideal application for creating nanocrystal particles with extremely high uniformity (very narrow particle size distribution), which is a new publication. by US researchers.

Moreover, this technology also allows the creation of different types of structures such as cubes, nuclei - composite shells . by cutting off with the presence of different background gases (According to the recent announcement on Applied Physics Letters 90 044103, 2007 ).

"One of the advantages of this new technology is simplicity," said Yong Che, one of IMRA's fiber laser experts (USA). "Nanoparticles are dispersed evenly. on the base without gathering . " Also the Che, this technique has the independence of base material and does not require heat treatment. This means that nanoparticles can condense right on heat-sensitive substrates, such as glass, plastic or polymer film.

Figure 1. Photo Yong Che and his colleagues. (Photo: NanotechWeb.org)

In this study, the researchers removed Ni, an important material in the field of magnetic recording materials. Che said the technique could be expanded on many other beers and the group was working on sample alloys and some dielectric samples. The key element of this technology is the elemental doped Ytterbium (Yb) laser (also known as the FCPA-mJewel laser), which emits 500 femtosecond pulsed lasers with a central wavelength of 1 mm and the repeating transformation rate back to 200 kHz. Scientists have discovered that they can extinguish the formation of droplet particles (greater than 20 nm) by limiting the effect of the laser on the sample to less than 1 J / cm ² . This value is considered to correspond to the threshold of strong plasma formation.

Figure 2. High resolution electron micrograph of NiO material sample.
(Photo: NanotechWeb.org)

Initially, the researchers removed beer in the vacuum, but it was the use of different substrates, such as Ar, O ₂ . and thus produced many interesting results. "We have created a shell-like structure (Ni-NiO) as originally intended". High-resolution transmission electron micrograph (Figure 2) conducted at the University of Michigan indicates that nano-cube particles are single NiO crystals. This result astounded researchers because the team initially thought that the ultra-fast laser removal time was too short for oxidation.

The above results were developed by the research team between IMRA Group and the University of Michigan, USA. Currently, the group is making plans to announce additional results in the future. Che said IMRA is willing to cooperate with other research groups to develop this technique.

(Photo: Vatlyvietnam)

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According to NanotechWeb.org, Vietnam Physics