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ABSTRACT: Semiconductor nanocrystals (NCs) prepared by wet-chemical routes have been proposed as an attractive candidate for fabrication of the third-generation thin-film solar cells due to their quantum confinement effects and excellent dispersion ability in polymer films. However, to date, a solar cell incorporating semiconductor NCs in the photoactive layer still has rather low efficiency due to the low carrier mobility of the non-continued NC phase and the possible radiative recombination in NCs. To avoid these disadvantages, NCs have been proposed and applied as a luminescent species in a passive photon converting layer to modify the solar spectrum before the light enters the photovoltaic device. Photon conversion processes, including up-conversion, down-conversion, and down-shifting, have been observed in various colloidal NC samples and have great potential to enhance photovoltaic performance when applied to the existing single-junction solar cells or narrow-band molecular-based devices.
Journal of Nanoscience and Nanotechnology 03/2010; 10(3):1418-29. · 1.56 Impact Factor
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ABSTRACT: The B7-H1/PD-1 co-signaling pathway has recently been found to play a pivotal role in the immune evasion of tumor cells from host immune system. The aim of this study was to examine the B7-H1 and PD-1 expression and TILs status in gastric cancer and to elucidate the clinical relevance of B7-H1 and PD-1 to the pathogenesis of gastric carcinoma.
Immunohistochemistry and ANAE histochemical staining were used to investigate the in situ expression of B7-H1 and PD-1 and TILs status in the gastric tissues. RT-PCR was used to explore B7-H1 and PD-1 expression at the transcriptional level. The B7-H1 expression at protein level was detected by Western blot.
Expression of B7-H1 and PD-1 was found to be increased in gastric carcinoma, but absent in normal gastric tissue. B7-H1 expression in gastric carcinoma was inversely correlated with TILs infiltration. B7-H1 but not PD-1 expression in tumor tissue was significantly correlated with some clinicopathhological variables including depth of invasion, lymph node metastasis and distant metastasis.
B7-H1 and PD-1 expressions are increased in gastric carcinoma. This signaling pathway may inhibit antitumor immune responses in gastric carcinoma. B7-H1 expression plays a critical role in the pathogenesis of human gastric carcinoma,and might be a promising prognostic marker and therapeutic target in the treatment of this disease.
Zhonghua zhong liu za zhi [Chinese journal of oncology] 04/2008; 30(3):192-5.
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Shu-Man Liu
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ABSTRACT: This review focuses on the preparation of Si nanoparticles by wet-chemical routes. The methods described include dispersion from porous silicon, etching and surface functionalization of Si/SiO2 powders and direct chemical reaction of Si precursors. Photoluminescence of silicon nanoparticles can be tuned to cover the whole visible spectrum depending on particle size. The excitonic origin or nature of PL has been generally accepted. Some researchers observed exciton recombination across the direct band-gap, i.e., gamma-gamma transitions, while others evidenced indirect nature of excitonic radiative recombination, which becomes direct in very small particles of 1-2 nm. A large redshift of photoluminescence from these small silicon nanoparticles has been explained by a localized surface states model. Others argue that no localized states are found in the band-gap if a complete oxide shell is formed, and the photoluminescence redshift is due to modification of band-edge states.
Journal of Nanoscience and Nanotechnology 04/2008; 8(3):1110-25. · 1.56 Impact Factor
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ABSTRACT: Si nanowires of diameters 5-20 nm and nanoparticles of approximately 4 nm were synthesized by a simple arc-discharge method in water. The TEM analysis reveals that the growth direction of the observed Si nanowires is parallel to the {111} crystal planes.
Chemical Communications 11/2005; · 6.17 Impact Factor
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ABSTRACT: Silicon nanopowder with a narrow size distribution was synthesized by a simple method, in which amorphous SiO(x) (x < 2) powder as starting material was annealed at high temperature and then etched by hydrofluoric acid (HF). Si nanoparticles thus obtained exhibited emission in the ultraviolet and visible regions under excitation at an energy corresponding to the direct band-gap transition. At the same time, they could be redispersed in various organic solvents such as octanol, toluene, etc., without surfactants or capping molecules on particle surfaces. X-ray diffraction and Fourier transform infrared spectroscopy were used to follow the change of components in the sample during annealing and HF etching processes, and the size distribution and dispersion morphology of the nanoparticles in different solvents were revealed by transmission electron microscopy analysis.
Langmuir 07/2005; 21(14):6324-9. · 4.19 Impact Factor
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ABSTRACT: Two devices structures of ITO/PVK: Rubrene/Al and ITO/Alq3:MN-PPV/Al were developed. Their characters of photoluminescence and electroluminscence were studied. The result showed that there were great difference between the photoluminescence and electroluminscence at a doping ratio of 2 wt% in ITO/PVK: Rubrene/Al. It is concluded that energy transfer in these dye-doped devices occurred by Förster energy transfer processes. And the trap effect of electrons of Rubrene on holes of PVK resulted in different combination probability of PVK excitation in photoluminescence and electroluminescence. At the same time, the two EL devices were color-tunable when the bias voltage was increased. The mechanisms which cause color variation are different. In the first device, it indicates that the energy transfer process from PVK to Rubrene is not complete. The combination probability of PVK excitation which does not contribute to the emission of Rubrene is increased when the bias voltage increases. But in the second device, there are many micro-interfaces due to the phase-separation just like the interface in a double layer device. The tunneling interface barriers of carriers is the main cause of color variation in the second device.
Guang pu xue yu guang pu fen xi = Guang pu 01/2003; 22(6):891-4. · 0.84 Impact Factor
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ABSTRACT: Semiconductor nanocrystals appear different optical properties from their bulk analogous due to quantum confinement effects. It is well known that optical absorption of nanocrystals shift to higher energy as the sizes decrease, while the emission at the absorption band edge is always too weak to be investigated in details due to much nonradiative recombination at nanoparticle surface. To eliminate the surface defects, some kinds of materials such as organic molecules, polymers and inorganic compounds are used to overcoat the nanoparticles. It has been found that nanocrystals overcoated with high band gap inorganic materials maned core/shell type nanocrystals exhibit high photoluminescence intensity at band edge due to effective elimination of surface nonradiative recombination. In this article we report the characteristics of CdSe/CdS core/shell nanocrystals synthesized with mercapto acid as stabilizer. The effect of CdS shell on the electronic characteristics and the luminescence of CdSe core were investigated by using optical absorption, photoluminescence and photoluminescence excitation spectra. Large band edge luminescence enhancement was found in CdSe nanoparticles overcoated with the CdS shell with a thickness of 0.3 nm due to passivation of nonradiative recombination sites on CdSe surfaces. Such bandadge emission also appeared redshift from the absorption maximum. This Stokes shift of the emission peak from the absorption edge was explained by a model of formation of excimer among the small nanoparticles based on the optical experimental results and the theoretical calculation on fine structures of bandadge excitons.
Guang pu xue yu guang pu fen xi = Guang pu 01/2003; 22(6):908-11. · 0.84 Impact Factor
