3 research outputs found
Polarization-Modified Upconversion Luminescence in Er-Doped Single-Crystal Perovskite PbTiO<sub>3</sub> Nanofibers
Understanding the energy transition
which is influenced by doping
ions and host materials in the upconversion (UC) physical processes
is of vital importance for further optimizing performance and extending
applications of UC materials. In this work, we have selected 4% Er-doped
perovskite PbTiO<sub>3</sub> (PTO) nanofibers as a model system to
explore the effects of tetragonality and polarization on UC photoluminescence
(PL) properties. By means of in situ X-ray diffraction, the tetragonality
and polarization of these nanofibers have been determined to gradually
decrease with an increasing of the temperature from 50 to 300 K, leading
to obvious enhancements in UC green band emission of 523 nm (about
43 times) and red band emission of 656 nm (about 8 times), in contrast
to the decreased green and red UC intensities in Er-doped BaTiO<sub>3</sub> or PTO particles. Moreover, the significant enhancement in
the intensity ratio of green to red bands from 0.17 to 0.86 has been
achieved, indicating that the emission enhancement is highly wavelength-dependent.
On the basis of in situ UC decay curves from 50 to 300 K, the UC lifetimes
of the <sup>4</sup>S<sub>3/2</sub> and <sup>4</sup>F<sub>9/2</sub> level have been derived to be 128.04 ± 0.47 μs and 278.10
± 1.07 μs at 50 K, respectively, and the values are basically
maintained as the temperature increases. The observed UC phenomena
in Er-doped perovskite PTO nanofibers can be ascribed to an assisted
effect of the low-energy EÂ(1TO) phonon on the UC process. Such phonon
energy can be easily tailored by the tetragonality and polarization;
thus, a modification of UC emissions in Er-doped PTO nanofibers has
been achieved. The findings in this work could provide new insights
into understanding the UC process in perovskite oxides and offer an
opportunity to tune UC emission by an external field, such as an electric
field, in addition to temperature
Growth and Bending-Sensitive Photoluminescence of a Flexible PbTiO<sub>3</sub>/ZnO Nanocomposite
A brushlike
PbTiO<sub>3</sub> (PTO)/ZnO nanocomposite with ZnO nanowires (NWs)
grown epitaxially on the surface of single-crystal ferroelectric tetragonal
PTO NWs is successfully fabricated onto a flexible substrate via a
two-step hydrothermal process. In this nanocomposite, a ZnO NW grew
along [0001] on the (101) plane of the core PTO NW with a lattice
mismatch of 1.06% to form an effective ferroelectric/semiconductor
interface. It is found that the ultraviolet photoluminescence emission
of the nanocomposite could be easily tuned by its bending curvatures
at room temperature. This intriguing phenomenon can be understood
by the bending-induced polarization field from the PTO NW, which could
reduce the bending degree of the energy band of the ZnO NWs through
the interface. Throughthe design of an effective interface, this kind
of ferroelectric/semiconductor nanocomposite may find potential applications
in sensor and piezophotonic nanodevices
Image_1_Functional molecular expression of nature killer cells correlated to HBsAg clearance in HBeAg-positive chronic hepatitis B patients during PEG-IFN α-2a therapy.tif
ObjectiveTo explore whether the frequencies and functional molecules expression of Natural Killer cells (NK cells) are related to hepatitis B surface antigen (HBsAg) disappearance in hepatitis B e envelope antigen (HBeAg)-positive patients with chronic hepatitis B (CHB) throughout peginterferon alpha-2a (PEG-IFN α-2a) treatment.MethodsIn this prospective research, HBeAg-positive patients with CHB received PEG-IFN α-2a treatment, completing 4-year follow-up. After PEG-IFN α-2a treatment, undetectable HBV DNA, HBsAg loss, and HBeAg disappearance were defined as functional cure. Proportions of NK, CD56dim, CD56bright, NKp46+, NKp46dim, NKp46high, and interferon alpha receptor 2 (IFNAR2)+ NK cells, and the mean fluorescence intensity (MFI) of NK cell surface receptors IFNAR2 and NKp46 were detected.Results66 patients were enrolled into the study in which 17 patients obtained functional cure. At baseline, hepatitis B virus desoxyribose nucleic acid (HBV DNA) titer in patients with functional cure was remarkably lower than that in Non-functional cure group. Compared with baseline, HBV DNA levels, HBsAg levels, and HBeAg levels significantly declined at week 12 and 24 of therapy in patients with functional cure. At baseline, the negative correlation between CD56bright NK% and HBV DNA and the negative correlation between CD56dim NK% and HBV DNA was showed; CD56bright NK% and IFNAR2 MFI in patients with functional cure were remarkably higher than those in patients without functional cure. After therapy, CD56bright NK% and NKp46high NK% in patients with functional cure were higher than those in patients without functional cure. In Functional cure group, after 24 weeks of treatment NK%, CD56bright NK%, IFNAR2 MFI weakly increased, and NKp46high NK% and NKp46 MFI significantly increased, meanwhile, CD56dim NK% and NKp46dim NK% decreased. Only NKp46 MFI increased after therapy in patients without functional cure.ConclusionThe lower HBV DNA load and the higher CD56bright NK% before therapy, and the higher the post-treatment CD56bright NK%, IFNAR2 MFI, NKp46high NK%, the easier to achieve functional cure.</p