Lanthanum hexaboride nanoparticles,with high emission electrons in cathode materials and peculiar blocking near infrared wavelengths,were applied for many aspects.Based on the quasi-static approximation of Mie theory,the size dependent optical properties of LaB6nanoparticles were researched,such as refractive index n(ω),extinction coefficient k(ω),reflectivity R(ω),absorption coefficientα(ω),and electron energy loss L(ω).Due to the localized surface plasmon resonance(LSPR),the extinction coefficient k(ω)and absorption coefficientα(ω)depended on the size,and the LSPR peaks red-shifted with sizes increased,which was different from that of bulk materials.In addition,electron energy-loss spectrum L(ω)showed electrons oscillation reinforced,since electrons absorbed the photon energy and generated resonance.Further,reflectivity R(ω)and refractive index n(ω)indicated that the light in near infrared region could not be propagated on the surface of LaB6materials,which exhibited metallic behaviors.So the resonance peak of LaB6nanoparticle was located in near-infrared region,making use of this property for solar control glazing and heat-shielding application.
Si4+-doped BaZr(BO3)2:Eu3+ phosphors are prepared by a conventional solid-state reaction.The influence of Si4+ addition on the charge transfer state of Eu3+-O2- and photoluminescence(PL) properties of BaZr(BO3)2:Eu3+ are discussed.Room temperature PL spectra indicated that efficient emission is obtained by Si doping.Increased values for the peak-peak ratio(PPR) of BaZr(BO3)2:Eu3+ at higher Si doping concentrations implied that the Eu3+ ion is located in a more asymmetric environment in BaZr0.8Si0.2(BO3)2:Eu3+ than in the undoped samples.The Judd-Ofelt parameters Ωλ(λ=2,4) were calculated from the PL data,giving results that were consistent with those from the PPR.The maximum radiative quantum efficiency was achieved at a Si doping concentration of 20 mol%.
ZHANG ZhongPengLI GuangMinZHANG XiaoSongXU ShengYanJI TingLI Lan
本文通过化学浴沉积法获得了直径约为50 nm,长度约为250 nm的ZnO纳米棒阵列,引入纳米ZnS对ZnO纳米棒进行表面修饰,分别制备得到了具有ITO(indium tin oxides)/ZnO/Poly-(3-hexylthiophene)(P3HT)/Au和ITO/ZnO@ZnS/P3HT/Au结构的多层器件.通过I-V曲线对比讨论了两种结构器件的开启电压,串联电阻,反向漏电流及整流比等参数,认为包含ZnS修饰层器件的开启电压、串联电阻、反向漏电流明显降低,整流比显著增强,展现出更优异的电子传输性能.光致发光光谱分析结果证实由于ZnS使ZnO纳米棒的表面缺陷产生的非辐射复合被明显抑制,弱化了电场激发下的载流子陷获,改善了器件的导电特性.
ZnS:Mn2+ nanocrystals(NCs) with particle size from 1.9 nm to 3.2 nm are synthesized via chemical precipitation method with different [S2-]/[Zn2+] ratios.The size-dependent decay for Mn emission exhibits a double exponential behavior.And two lifetime values,in millisecond time domain,can both be shortened with size increasing,which is attributed to enhanced interaction between host and Mn2+ impurity.A molecular structure model is proposed to interpret the tendency of two lifetime components,which is correlated to the number of S vacancy(Vs) defects around Mn2+.
ZnO:Cu/ZnO core/shell nanocrystals are synthesized by a two-step solution-phase process. The morphology, structure and optical properties of the samples are detected by scanning electron microscopy, Raman, absorption and luminescence spectroscopy. The increase of particle size confirms the growth of ZnO shell. The segregation of CuO phase observed in ZnO: Cu core is not detected in ZnO:Cu/ZnO core/shell nanocrystals from Raman spectra. It is suggested that some Cu ions can be segregated from ZnO nanocrystals, and the separated Cu ions can be incorporated inside ZnO shell after the growth of ZnO shell. The visible emission mechanism is discussed in detail, and the photoluminescence analysis indicates that the core/shell structure helps to eliminate the surface-related emission.
Undoped ZnS nanocrystals(NCs) with different precursor molar ratios of [S2-]/[Zn2+] are prepared by the chemical precipitation method.The structural and optical properties of the samples are characterized by the X-ray diffraction(XRD) spectra,photoluminescence(PL) spectra and PL decay spectra.The XRD analysis shows that the crystal quality of ZnS NCs becomes better and the grain size is larger at higher [S2-]/[Zn2+] ratios.The PL peaked at 430 nm decreases with the [S2-]/[Zn2+] ratio increasing,which is ascribed to the structure defects of NCs.A multi-exponential decay time curve with hundreds of picoseconds,several nanoseconds and tens of nanoseconds is obtained,which also shows a distinct and regular change with [S2-]/[Zn2+] ratio.It is indicated that the PL and emission decay properties of ZnS NCs mainly depend on the change of the defects number from different particle sizes.
We synthesize Tm3+/Tb3+/Eu3+triply-doped ZrF4–BaF2–LaF3–AlF3–NaF(ZBLAN) transparent glass by using a melt-quenching method. Under excitation of 365 nm, the white emission with Commission internationale deL'Eclairage(CIE) coordinates of(0.33, 0.33) is achieved at the Eu3+concentration of 1.1 mol%. The mechanisms for white emission and the energy transfer process of Tb3+→ Eu3+are discussed in terms of the photoluminescence, photoluminescence excitation spectra, and the light emission decay curves. The nature for the Tb3+→ Eu3+energy transfer is described with the aid of an energy level diagram.
