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Photoluminescence features of AgBr nanoparticles formed in porous glass matrices

Doycho I. K., Gevelyuk S. A., Ptashchenko O. O., Rysiakiewicz-Pasek E., Tolmachova T. M., Tyurin O. V., Zhukov S. O.

Optica Applicata

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2010

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Vol. 40, nr 2

323--332

EN

The photoluminescence of AgBr nanoparticles formed by a two stage liquid-gas microsynthesis technology in two types of porous glass with different sizes of pores was investigated. Polyvinyl alcohol (Polinol) was used as a binder. It has been found that AgBr nanoparticles in the glasses with smaller pores luminesce more intensively, and we attribute this phenomenon to the differ-ences in pore size distributions. The luminescence spectra were shown to have two maxima corresponding to AgBr nanoparticles formed within the nanopores of two different sizes characteristic of each of the matrices. In both cases, the spectra excited by xenon lamp irradiation are more intensive than those stimulated by a 337-nm nitrogen laser. Comparing the maxima shifts in the phosphorescence excitation spectra with ones in phosphorescence spectra we can conclude that the luminescence and phosphorescence centers in AgBr nanoparticles are of identical nature in the matrices of both types. The investigation results fit neatly into the inherently consistent quantum confinement model and are well correlated with the poroscopic spectra of both types of glass.

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Room temperature ferromagnetism in Si nanocaps on self-assembled glass beads

Chi Y. C., Liou Y.

Materials Science Poland

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2010

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Vol. 28, No. 4

823--832

EN

Based on self-assembly techniques, Si layers of various thicknesses were deposited on glass bead arrays of various dimensions. The experimental results support the view that the self-assembled glass beads of small sizes (i.e., 10 and 20 nm in diameter), covered with a Si layer below 5 nm in thickness, can induce ferromagnetism. Regularity in the saturation magnetization confirms that the ferromagnetic-like behaviours heavily depend on both the size of the glass beads as well as the thickness of Si nanocaps. Maximum magnetization (750 emu/cm3) was found in the 20 nm glass bead template on which was deposited an ultra-thin 1 nm Si layer. We suggest that the quantum confinement mechanism helps to promote the unpaired electrons, which interact with neighbouring counterparts through the tunnelling effect and, thus, contribute to room temperature ferromagnetism.

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Quantum confinement effect of in-situ generated Cu2O in a nanostructured zirconia matrix

Kundu S., Jana S., Biswas P. K.

Materials Science Poland

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2005

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Vol. 23, No. 1

7--14

EN

The incorporation of Cu2+ in zirconyl chloride octahydrate sol or solution was used as a precursor for dip coating. This resulted in the in-situ formation of nanostructured Cu2O quantum particles in the zirconia matrix. The size-dependent properties of the Cu2O quantum particles were observed when the films were annealed in the range of 200-600°C. A red shift of the UV band, ascribed to the transition from the copper d-shells to higher sublevels of the conduction band, was observed in the range of 260-315 nm due to an increase in the nanocrystallite size with increasing annealing temperature. Three types of emissions, blue, green, and yellow, were observed in films of relatively high thickness (around 120-130 nm) due to Wannier-like excitonic transitions. For films of relatively low thickness (50-70 nm) only green emission was observed. From lifetime measurements of samples annealed at 450°C it may be concluded that the short decay time is bi-exponential in character from ns to ps with the chi-square value of 1.005, which is due to the confinement of Cu2O quantum particles.