Le Quoc Minh

Wieslaw Strek

Tran Kim Anh

Kui Yu

Luminescent Nanomaterials

The cathodoluminescence properties of rare-earth (RE = Ce, Eu, Tb) doped nanocrystalline phosphors (<mml:math id="E1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub></mml:math>, <mml:math id="E2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:mtext>A</mml:mtext><mml:msub><mml:mtext>l</mml:mtext><mml:mn>5</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub></mml:math>) were investigated. Their structure and morphology were determined and correlated with optical properties. The effect of grain sizes on emission yield of RE doped nanophosphors has been investigated. A possibility of application of RE doped nanophosphors for efficient field emission display (FED) devices has been discussed.

P. Psuja

D. Hreniak

W. Strek

Rare-Earth Doped Nanocrystalline Phosphors for Field Emission Displays

Luminescence, energy transfer, and upconversion mechanisms of nanophosphors (<mml:math id="E7" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext> </mml:mtext><mml:mtext>:</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>Eu</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math id="E8" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Tb</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math id="E9" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext> </mml:mtext><mml:mtext>:</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>Tm</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math id="E10" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext> </mml:mtext><mml:mtext>:</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math id="E11" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Yb</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>) both in particle and colloidal forms were studied. The structure, phase, and morphology of the nanopowders and nanocolloidal media were determined by high-resolution TEM and X-ray diffraction. It was shown that the obtained nanoparticles have a round-spherical shape with average size in the range of 4 to 20 nm. Energy transfer was observed for <mml:math id="E12" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext> </mml:mtext><mml:mtext>:</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>Eu</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math id="E13" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Tb</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> colloidal and powders, upconversion transitions were observed for both <mml:math id="E14" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext> </mml:mtext><mml:mtext>:</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> and <mml:math id="E15" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext> </mml:mtext><mml:mtext>:</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math id="E16" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Yb</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> nanophosphors. The dependence of photoluminescence (PL) spectra and decay times on doping concentration has been investigated. The infrared to visible conversion of emission in <mml:math id="E17" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Y</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext> </mml:mtext><mml:mtext>:</mml:mtext><mml:mtext> </mml:mtext><mml:mtext>Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math id="E18" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Yb</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> system was analyzed and discussed aiming to be applied in the photonic technology.

TranKim Anh

Paul Benalloul

Charles Barthou

Lam thiKieu Giang

Nguyen Vu

LeQuoc Minh

Luminescence, Energy Transfer, and Upconversion Mechanisms of 
Y2O3
Nanomaterials Doped with Eu3+,Tb3+, Tm3+,Er3+, and Yb3+ Ions

Combustion and sol-gel methods were used to prepare the upconverting nanocrystalline <mml:math id="E1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mtext>ZrO</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>:<mml:math id="E2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Yb</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>,<mml:math id="E3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> phosphors. The crystal structure was studied by X-ray powder diffraction and the crystallite sizes were estimated with the Scherrer formula. Impurities and nanomaterials' thermal degradation were analyzed with FT-IR spectroscopy and thermal analysis, respectively. Upconversion luminescence and luminescence decays were studied with IR-laser excitation at 977 nm. All nanomaterials possessed the cubic <mml:math id="E4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mtext>ZrO</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> fluorite-type structure except for a small monoclinic impurity obtained with the sol-gel method. The conventional <mml:math id="E5" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo></mml:msubsup></mml:mrow></mml:math> and <mml:math id="E6" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>OH</mml:mtext></mml:mrow><mml:mo>−</mml:mo></mml:msup></mml:mrow></mml:math> impurities were observed for the combustion synthesis products. The <mml:math id="E7" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mtext>ZrO</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>:<mml:math id="E8" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Yb</mml:mtext></mml:mrow><mml:mn>3</mml:mn></mml:msub><mml:msup><mml:mrow><mml:mtext>,Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> nanomaterials showed red (630–710 nm) and green (510–570 nm) upconversion luminescence due to the <mml:math id="E9" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>4</mml:mn><mml:msub><mml:mtext>F</mml:mtext><mml:mrow><mml:mn>9</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>→</mml:mo><mml:mn>4</mml:mn><mml:msub><mml:mtext>I</mml:mtext><mml:mrow><mml:mn>15</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math> and <mml:math id="E10" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mn>2</mml:mn><mml:msub><mml:mtext>H</mml:mtext><mml:mrow><mml:mn>11</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>,</mml:mo><mml:mn>4</mml:mn><mml:msub><mml:mtext>S</mml:mtext><mml:mrow><mml:mn>3</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mo>→</mml:mo><mml:mn>4</mml:mn><mml:msub><mml:mtext>I</mml:mtext><mml:mrow><mml:mn>15</mml:mn><mml:mo>/</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math> transitions of <mml:math id="E11" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, respectively. The products of the combustion synthesis exhibited the most intense luminescence intensity and showed considerable afterglow. It was concluded that excitation energy is partially trapped in the system and subsequently bleached thermally to the luminescent <mml:math id="E12" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>Er</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> center to yield “persistent upconversion”.

Iko Hyppänen

Jorma Hölsä

Jouko Kankare

Mika Lastusaari

Laura Pihlgren

Upconversion Properties of Nanocrystalline ZrO2:Yb3+, Er3+ Phosphors

Dynamics of photo-excited carrier relaxation 
 processes in cadmium selenide nanocrystal thin films 
 prepared by chemical bath deposition method have been 
 studied by nondegenerate femtosecond transient 
 pump-probe spectroscopy. The carriers were generated 
 by exciting at 400 nm laser light and 
 monitored by several other wavelengths. The induced 
 absorption followed by a fast bleach recovery observed 
 near and above the bandgap indicates that the 
 photo-excited carriers (electrons) are first trapped 
 by the available traps and then the trapped electrons 
 absorb the probe light to show a delayed absorption 
 process. The transient decay kinetics was found to be 
 multiexponential in nature. The short time constant, 
<mml:math id="E1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>&lt;</mml:mo></mml:math>1 picosecond, was attributed to the trapping of 
electrons by the surface and/or deep traps and the long time 
constant, <mml:math id="E2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>≥</mml:mo></mml:math>20 picoseconds, was due to the recombination of the trapped carriers. A very little difference in the relaxation processes was observed in the samples prepared at bath temperatures from <mml:math id="E3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mn>25</mml:mn></mml:mrow><mml:mo>∘</mml:mo></mml:msup><mml:mtext>C</mml:mtext></mml:mrow></mml:math> to <mml:math id="E4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mn>60</mml:mn></mml:mrow><mml:mo>∘</mml:mo></mml:msup><mml:mtext>C</mml:mtext></mml:mrow></mml:math>.

M. C. Rath

J. A. Mondal

D. K. Palit

T. Mukherjee

H. N. Ghosh

Femtosecond Transient Absorption Studies in Cadmium Selenide Nanocrystal Thin Films Prepared by Chemical Bath Deposition Method

Two different kinds of rare earth-activated glass-based nanocomposite photonic materials, which allow to tailor the spectroscopic properties of rare-earth ions: (i) Er3+-activated SiO2-HfO2 waveguide glass ceramic, and (ii) core-shell-like structures of Er3+-activated silica spheres obtained by a seed growth method, are presented.

C. Armellini

A. Chiappini

A. Chiasera

M. Ferrari

Y. Jestin

M. Mortier

E. Moser

R. Retoux

G. C. Righini

Rare Earth-Activated Silica-Based Nanocomposites

Recent results on the photoluminescence properties of silicon nanocrystals embedded in silicon oxide are reviewed and discussed. The attention is focused on Si nanocrystals produced by high-temperature annealing of silicon rich oxide layers deposited by plasma-enhanced chemical vapor deposition. The influence of deposition parameters and layer thickness is analyzed in detail. The nanocrystal size can be roughly controlled by means of Si content and annealing temperature and time. Unfortunately, a technique for independently fine tuning the emission efficiency and the size is still lacking; thus, only middle size nanocrystals have high emission efficiency. Interestingly, the layer thickness affects the nucleation and growth kinetics so changing the luminescence efficiency.

L. Ferraioli

M. Wang

G. Pucker

D. Navarro-Urrios

N. Daldosso

C. Kompocholis

L. Pavesi

Photoluminescence of Silicon Nanocrystals in Silicon Oxide

The development of scintillating materials is believed to reach a new step by controlling their preparation on a nanometric level. Sol-Gel chemistry offers very unique tools for nanoscale mastering of the materials preparation. In particular, shaping of the materials as thin films or nanoparticles offers new application in medical imaging. The control of doping ions dispersion thanks to soft chemistry is also a great advantage of such synthetic routes. In this paper, we will review recent work devoted to the sol-gel preparation of inorganic scintillating materials. We will focus on the new possibilities and advantages offered by sol-gel chemistry for the preparation of new scintillators and improvement of existing ones.

J. M. Nedelec

Sol-Gel Processing of Nanostructured Inorganic Scintillating Materials

Poly(vinylcarbazole) (PVK) was decorated with surfactant group to achieve amphiphilic polymer with luminescent property. The composition and properties of the polymers were systematically investigated using FTIR, EA, TGA, UV-Vis, and PL characterizations. Different CdTe nanocrystals (NCs) prepared in aqueous medium were directly transferred to organic phase using the PVK-based polymers. The quantum yield of NCs in the composites had been improved by 50&#37; compared with their parent aqueous solution due to the short distance from carbazole moieties to NCs, which facilitated the F&#246;rster resonant energy transfer (FRET) between them. Moreover, efficient electron transfer at the interface of NCs and polymers had been confirmed which also indicated the application in photovoltaic cell for such composites.

Haizhu  Sun

Junhu  Zhang

Ye  Tian

Yang  Ning

Hao  Zhang

Jie  Ju

Delong  Li

Shidong  Xiang

Bai  Yang

Multifunctional Composites Obtained by Incorporating Nanocrystals into Decorated PVK Polymers

The synthesis of nanocrystalline N<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>b</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math>:E<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>u</mml:mtext><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> has been achieved by using a Pechini procedure. The obtained materials are single-phase niobia with the orthorhombic structure, average crystallite size around 25&#x2009;nm and average lattice strain of about 0.002. TEM images show that the particles are rectangular and reasonably isolated. The luminescence of the E<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mtext>u</mml:mtext><mml:mrow><mml:mn>3</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> ions in the niobia lattice is efficient and affected by a strong inhomogeneous broadening, due to an important disorder around the lanthanide ions.

Daniele  Falcomer

Adolfo  Speghini

Giulio  Ibba

Stefano  Enzo

Carla  Cannas

Anna  Musinu

Marco  Bettinelli

Morphology and Luminescence of Nanocrystalline Nb2O5 Doped with Eu3+

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