On the Road to True Silicon Lasers using Nanoparticles Print
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Thursday, 04 December 2008 16:30

Hôm nay, 04/12/2008, trong khuôn khổ hợp tác giữa trường ĐHBKHN với ĐH kỹ thuật Praha CH Séc, GS. Fojtik trình bày kết quả nghiên cứu trong lĩnh vực nano  tại Hội trường ITIMS với 2 chủ đề:
“On the Road to True Silicon Lasers using Nanoparticles” và
"Biomedical Application of Metallic and Magnetic Nanoparticles"

Nội dung Abstract của 2 chủ đề này là:

“On the Road to True Silicon Lasers using Nanoparticles” 

Abstract of lecture
To satisfy the need for CPU clock frequencies continuous increase, optical data transmission process integrated within silicon chips is required. Practical optical amplification in silicon is therefore very desirable. Unfortunately, bulk silicon is an indirect bandgap semiconductor with very low light-emission efficiency. To overcome this problem, the stimulated Raman scattering has been successfully employed for light amplification and lasing in silicon. Due to the two-photon absorption nonlinear optical loss, this scheme was initially working only in a pulsed operation mode. Very recently, an improved design has been allowed also for the continuous operation. However, this encouraging development still contains a major drawback—a need for an external optical pumping. It seems that this problem might be overcome by switching from the bulk silicon to its properly prepared nanocrystalline form provided a reasonably good electroluminescence can be achieved. An intensive research is under way with some first promising results already in the pipeline.
Light-emitting silicon nanocrystals are prepared by the pyrolysis of silane and subsequent controlled size reduction by chemical etching. These nanocrystals show luminescence tunable through the full visible spectral region. The luminescence rate increases by two orders of magnitude when shortening wavelength from red to blue side of the spectrum, which is interpreted as relaxation of the direct band-gap energy structure.

"Biomedical Application of Metallic and Magnetic Nanoparticles"

Nanotechnology is getting still more attention and is becoming emerging topic of recent days. Its biological and medical approaches and applications are opening novel, unpredicted and efficient ways of solving health issues, that is why the extraordinary field of bionanotechnology is shaping into one of the leading sciences of the 21st century… Goal of the project is to functionalize Fe3O4 magnetic nanoparticles, which according to chemical groups attached at the surface, are able to bond to special pathogens (bacteria or virus) and being easily manipulated by magnetic field, they can be removed from the system taking the pathogens with them as well.
Nanoparticles are produced by 'wet' chemical way under special conditions. Final product is 10s of nanometers in diameter and possesses special superparamagnetic properties, which give it ability to be manipulated while working in complex biological systems such as human body. Shape and size of nanoparticles are evaluated using AFM, magnetic properties measured by Mössbauer Spectroscopy and Superconducting Quantum Interference Device (SQUID). Surface of the particles is stabilized and treated, so that they maintain their unique properties and remain stable and separated. Certain chemical groups, proteins or residues are attached onto the surface to functionalize it. Particles are then ready to play a key role in recognition of the pathogens bonding to the surface of nanoparticles and following applied magnetic field to get out of the system.