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Fluorescent red-emitting (Y[sub 0.92]Eu[sub 0.08])[sub 2]O[sub 3] films were deposited on sapphire substrates by the metallorganic chemical vapor deposition technique. The films were weakly luminescent in the as-deposited condition. The as-deposited films were composed of nanocrystals embedded in columnar grains. A KrF laser with ultraviolet (λ=248 nm) pulses at a fluence level between 0.9 and 2.3 J/cm[sup 2] was applied to different regions of the film. Increasing the energy fluence density initially increased the photoluminescence intensity but decreased it at the highest level. Transmission and scanning electron microscopy verified that surface melting and ablation occurred at all fluence levels. Computational modeling of the laser melting and ablation process predicted that a significant fraction of the film is removed by ablation at the highest fluence levels, thereby decreasing the photoluminescence intensity of the films due to the significant amount of material removed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Describes a high-efficiency solar cell having the structure of a microcrystalline silicon carbide on polycrystalline silicon. Details of experimental techniques used; Electron cyclotron resonance plasma chemical vapor system and deposition conditions of microcrystalline silicon carbide; Description of electrical and optical properties of dopes microcrystalline silicon carbide films.

This work presents the structural, morphological and optical properties of LaSr2AlO5:Yb3+,Er3+ phosphors (LSA:Yb,Er) synthesized by a combustion method. The Yb3+ concentration was kept constant at 2 mol.%, while the Er3+ concentration changed from 0.2 mol.% to 6 mol.%. X-ray diffraction measurements revealed that all the LSA:Yb,Er phosphors presented a pure tetragonal phase. Scanning electron microscopy images show that LSA:Yb,Er phosphors increased their size as the Er3+ concentration increases (from 1.95 μm for Er3+ concentrations < 1 mol.% to 2.3 μm for Er3+ content in the range of 1 ≤ x < 6 mol.%,). In addition, the phosphors presented oval-like and quasipherical shapes for Er3+ content ≤ 1 mol.%. When the Er3+ concentrations are > 1 mol.%, the LSA:Yb,Er phosphors present a notorious increase of conglomeration, and the particles had irregular morphologies. According to luminescence measurements, the LSA:Yb,Er phosphors present a green luminescence centered at 549 nm (λexc = 968 nm). The strongest green emission was observed for an Er3+ concentration of 1 mol.%, above this concentration, the green emission intensity decreases due to an excess of OH and carbonate groups on the surface of LSA:Yb,Er phosphors, as confirmed by the FTIR spectra. Moreover, the CIE coordinates for the green emission were tuned with the Er3+ concentration. These results suggest that LSA host could be a good candidate to produce upconversion emission when doped with rare earths, which could be attractive for the development of lighting sources. [ABSTRACT FROM AUTHOR]

Upconversion nanoparticles (UCNPs) have been used as biolabels for cancer cells due to their ability to absorb near-infrared photons and upconvert them into visible radiation. We reported the synthesis of UCNPs Y2O3/Yb3+, Er3+ (1, 1 mol%), which upon excitation with infrared photons (λ = 980 nm) emit green colorwith a maximum peak centered at λ = 550 nm. UCNPs were functionalized with folic acid (UCNPs-NH2- FA) and analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy, XRD, DLS and photoluminescence measurements. UCNPs-NH2-FA had a particle size of 70 ± 10 nm and exhibit a good luminescence spectrum in comparison with bare UCNPs. Cytotoxicity of different concentrations of bare and functionalized UCNPs was measured with the MTT assay in three cancer cell lines: human cervical adenocarcinoma (HeLa) and human breast adenocarcinoma cells (MDA-MB-231 and MCF-7). Some concentrations of bare UCNPs were cytotoxic for cells; however, after been functionalized, UCNPs resulted to be non-cytotoxic. Genotoxicity of bare and functionalized UCNPs was performed by the comet assay, andno DNA damage was found for any concentration. The internalization of UCNPs-NH2- FA into cancer cells was confirmed by confocal microscopy showing a cytoplasmic fluorescence signal.UCNPs-NH2-FAwere used to detect cancer cells in suspension by flow cytometry, with a specific green fluorescent signal for effective detection of cells. These results confirm that functionalized UCNPs can be used without any cytotoxic or genotoxic effects for bioimaging to detect and visualize cancer cells. [ABSTRACT FROM AUTHOR]